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APMP Supplementary Comparisons of
LED Measurements
APMP.PR-S3a Averaged LED Intensity
APMP.PR-S3b Total Luminous Flux of LEDs
APMP.PR-S3c Emitted Colour of LEDs
Final Report (July 2012)
Dong-Hoon Lee, Seongchong Park, and Seung-Nam Park
Division of Physical Metrology, Korea Research Institute of Standards and Science (KRISS)
267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-340, Rep. Korea
Correspondance to: [email protected]
APMP.PR-S3a Averaged LED Intensity Final Report
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Table of Contents
1. Introduction ...................................................................................................................................................... 5
2. Comparison Protocol .................................................................................................................................... 5
3. Artifact LEDs ..................................................................................................................................................... 7
4. Measurement Capabilities of Participants........................................................................................... 9
4.1. KRISS .......................................................................................................................................................... 9
4.2. MIKES ...................................................................................................................................................... 14
4.3. CMS-ITRI ................................................................................................................................................ 22
4.4. PTB ........................................................................................................................................................... 29
4.5. NMIJ ......................................................................................................................................................... 37
4.6. CENAM ................................................................................................................................................... 44
4.7. LNE ........................................................................................................................................................... 52
4.8. METAS ..................................................................................................................................................... 63
4.9. NMC-A*STAR ....................................................................................................................................... 74
4.10. VSL ....................................................................................................................................................... 80
4.11. NMIA ................................................................................................................................................... 89
4.12. NIST ..................................................................................................................................................... 98
4.13. VNIIOFI ............................................................................................................................................. 104
4.14. MKEH ................................................................................................................................................ 104
4.15. INM .................................................................................................................................................... 109
5. Reported Results of Participants ........................................................................................................ 117
5.1. KRISS ..................................................................................................................................................... 117
5.2. MIKES .................................................................................................................................................... 120
5.3. CMS-ITRI .............................................................................................................................................. 120
5.4. PTB ......................................................................................................................................................... 121
5.5. NMIJ ....................................................................................................................................................... 121
APMP.PR-S3a Averaged LED Intensity Final Report
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5.6. CENAM ................................................................................................................................................. 122
5.7. LNE ......................................................................................................................................................... 122
5.8. METAS ................................................................................................................................................... 123
5.9. NMC-A*STAR ..................................................................................................................................... 123
5.10. VSL ..................................................................................................................................................... 124
5.11. NMIA ................................................................................................................................................. 125
5.12. NIST ................................................................................................................................................... 125
5.13. VNIIOFI ............................................................................................................................................. 126
5.14. MKEH ................................................................................................................................................ 126
5.15. INM .................................................................................................................................................... 127
6. Pre-draft A Process .................................................................................................................................. 128
6.1. Verification of Reported Results ............................................................................................... 128
6.2. Temperature Correction and Artifact Drift ........................................................................... 128
6.3. Review of Relative Data ................................................................................................................ 137
6.4. Review of Uncertainty Budgets ................................................................................................. 138
6.5. Identification of Outliers ............................................................................................................... 138
7. Data Analysis ............................................................................................................................................... 139
7.1. Calculation of Difference to Pilot ............................................................................................. 139
7.2. Calculation of Comparison Reference Value ....................................................................... 140
7.3. Calculation of Degree of Equivalence .................................................................................... 141
7.4. Data Analysis Spreadsheet .......................................................................................................... 141
8. Comparison Results ................................................................................................................................. 142
8.1. Red LEDs .............................................................................................................................................. 142
8.2. Green LEDs ......................................................................................................................................... 144
8.3. Blue LEDs ............................................................................................................................................. 146
8.4. White LEDs.......................................................................................................................................... 148
APMP.PR-S3a Averaged LED Intensity Final Report
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8.5. Diffuser-type Green LEDs ............................................................................................................. 150
9. Discussion ..................................................................................................................................................... 153
9.1. Test of Consistency ......................................................................................................................... 153
9.2. Accuracy of Alignment .................................................................................................................. 153
9.3. Accuracy of Color Correction ..................................................................................................... 154
10. Summary .................................................................................................................................................. 157
Acknowledgement ............................................................................................................................................. 158
Appendix A: Technical Protocol ................................................................................................................... 159
Appendix B: Review of Relative Data ........................................................................................................ 160
Appendix C: Comments from Review of Relative Data .................................................................... 161
Appendix D: Comments from Review of Uncertainty Budgets ..................................................... 162
Appendix E: Identification of Outliers ....................................................................................................... 163
Appendix F: Comments and Revision to Draft A Report ................................................................. 164
APMP.PR-S3a Averaged LED Intensity Final Report
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1. Introduction
With the recent growth of the solid state lighting and display industry, the interest and
importance of accurate measurement of light-emitting diodes (LEDs) are increasing.
Photometric measurement of LEDs, however, is influenced by the specific properties of
individual LED such as spectral distribution, spatial emission profile, temperature
dependence, etc. In general, the measurement uncertainty of LEDs is larger than that of
the conventional incandescent lamps, and greater care is required to avoid or correct the
systematic errors related to the LED properties.
The Asia Pacific Metrology Programme (APMP) Technical Committee of Photometry
and Radiometry (TCPR) decided at its meeting in December 2006 to conduct
supplementary comparisons on measurement of LEDs to test the metrological
equivalence among national metrology institutes (NMIs) under the CIPM Mutual
Recognition Arrangement (MRA)1. The participation was not limited to NMIs in APMP, but
also NMIs of other regional metrology organizations (RMOs). The Korea Research
Institute of Standards and Science (KRISS) of Republic Korea is designated as the pilot
laboratory.
Three measurement quantities of LEDs are selected for the comparisons, which are
listed as service categories for Calibration and Measurement Capabilities (CMCs):
averaged LED intensity in condition B defined by International Commission on
Illumination (CIE) 2 , total luminous flux, and emitted color expressed as chromaticity
coordinates (x, y) according to the CIE 1931 standard colorimetric system3. The three
comparisons are registered as APMP.PR-S3a, -S3b, and -S3c, respectively.
In this report, we summarize the results of the comparison S3a on averaged LED
intensity.
2. Comparison Protocol
The organization, the artifact LEDs, and the guidelines for measurement and report of all
the three comparisons (S3a, S3b, S3c) are settled on one technical protocol before the
start of the comparisons. The protocol is drafted by the pilot lab, agreed by the
participants, and approved by the APMP TCPR in January 2008. The protocol is once
revised in November 2008, as the INM of Romania has joined as an additional participant.
1 http://www.bipm.org/en/cipm-mra/ 2 Measurement of LEDs, 2nd edition, CIE Technical Report 127-2007. 3 Colorimetry, 3rd edition, CIE 015:2004.
APMP.PR-S3a Averaged LED Intensity Final Report
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The final version of the technical protocol is included in
Table 10-1. Summary of the unilateral DoEs and their uncertainties for APMP.PR-S3a (temperature correction applied).
NMI
RED GREEN BLUE WHITE DIFFUSE
DoE U of
DoE DoE
U of
DoE DoE
U of
DoE DoE
U of
DoE DoE
U of
DoE
MIKES -0.001 0.039 0.002 0.040 0.021 0.042 0.005 0.037 0.002 0.020
CMS-ITRI -0.022 0.049 -0.012 0.044 -0.014 0.050 -0.019 0.043 -0.011 0.045
PTB 0.003 0.034 0.001 0.026 -0.004 0.037 0.002 0.024 -0.007 0.020
NMIJ -0.021 0.032 0.019 0.035 0.045 0.044 0.001 0.037 0.011 0.027
CENAM -0.343 0.062 -0.126 0.072 -0.076 0.068 -0.201 0.060 -0.147 0.069
LNE 0.020 0.032 0.030 0.027 0.008 0.035 0.010 0.050 0.030 0.022
METAS -0.028 0.028 -0.001 0.026 0.025 0.039 -0.015 0.020 -0.010 0.025
NMC-
A*STAR 0.007 0.029 -0.002 0.027 0.014 0.029 -0.008 0.023 -0.008 0.024
VSL 0.006 0.026 0.013 0.028 0.010 0.029 0.004 0.030 0.004 0.027
NMIA 0.101 0.043 -0.063 0.030 -0.035 0.031 0.035 0.021 -0.008 0.023
NIST 0.031 0.034 0.036 0.032 0.032 0.044 0.033 0.027 0.041 0.025
VNIIOFI 0.037 0.021 -0.033 0.034 -0.085 0.028 -0.010 0.017 -0.029 0.025
MKEH -0.022 0.024 0.026 0.024 0.067 0.032 0.004 0.022 0.015 0.018
INM 0.082 0.116 0.118 0.114 0.123 0.131 0.093 0.112 0.164 0.114
KRISS -0.011 0.018 -0.012 0.017 0.000 0.018 -0.019 0.015 -0.021 0.015
Acknowledgement
The pilot work of this comparison is partly supported by the Korean Ministry of
Knowledge and Economy under the project of LED standardization, grant B0010209.
APMP.PR-S3a Averaged LED Intensity Final Report
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Appendix A: Technical Protocol as an electronic file. Table 0-1 shows the final list of
participants to the S3a comparison with the measurement schedules planned and
performed. We note that the NPL of the UK listed on the technical protocol has
withdrawn its participation in August 2009.
Table 0-1. List of participants and measurement schedules of APMP.PR-S3a.
NMI country contact person(s) measurement
planned LED set
measurement
performed
results
reported
KRISS
(pilot) Korea
Seongchong Park,
Dong-Hoon Lee -- -- -- --
NMC-
A*STAR
Singapore Yuanjie Liu,
Gan Xu
June ~ Aug.
2008 #8
10 July ~ 28 Aug.
2008
12 Jan.
2009
MIKES Finland (Pasi Manninen),
Tuomas Poikonen,
March ~ May
2008 #1
7 April ~ 13 April
2008
17 June
2008
NIST USA
Cameron Miller,
Yoshi Ohno,
Yuqin Zong
Aug. ~ Oct.
2008 #3
18 Feb. ~ 25 Feb.
2009
31 July
2009
CMS-
ITRI
Chinese
Taipei Cheng-Hsien Chen
March ~ May
2008 #2
26 May 2008 ~ 2
Oct. 2009*
26 Oct
2009
PTB Germany
Matthias
Lindemann,
Robert Maass
April ~ June
2008 #3 May ~ July 2008
18 July
2009
CENAM Mexico
Laura P. González,
Anayansi Estrada,
Eric Rosas
May ~ July
2008 #5
17 July ~ 21 July
2008
08 May
2009
NMIJ Japan Kenji Godo,
(Terubumi Saito)
April ~ June
2008 #4
17 April ~ 22
June 2008
01 Aug.
2008
METAS Switzerland Peter Blattner June ~ Aug.
2008 #7
08 Sept ~ 17 Sept
2008
07 April
2009
LNE France Jimmy Dubard May ~ July
2008 #6
15 June ~ 13 July
2008
15 April
2009
VSL The
Netherlands
(Eric van der Ham),
M. Charl Moolman,
Daniel Bos
July ~ Sept.
2008 #1
13 Oct 2008 ~ 12
Jan 2009
1 Oct
2009
NMIA Australia (Philip Lukins),
Peter Manson
July ~ Sept.
2008 #2 Jan. ~ May 2009
4 May
2010
VNIIOFI Russia Tatiana Gorshkova,
Stanislav Shirokov
Sept. ~ Nov.
2008 #5
28 Nov ~ 05 Dec
2008
06 Feb.
2009
MKEH Hungary George Andor Sept. ~ Nov.
2008 #6
20 Nov ~ 09 Dec
2008
25 March
2009
INM Romania Mihai Simionescu Nov. ~ Dec.
2008 #7 Dec 2008
30 March
2009
* The CMS-ITRI had the initial measurement in May 2008, but it had to repeat the measurement on the red
LEDs in Oct 2009 due to damages in the initial measurement.
The comparison was performed as a star-type circulation of multiple sets of artifact
LEDs. The round for each participant had the following sequence: (1) first measurement
by the pilot, (2) measurement by the participant, (3) second measurement by the pilot.
The results of the repeated measurement by the pilot are used to evaluate the stability of
APMP.PR-S3a Averaged LED Intensity Final Report
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the artifact LEDs.
3. Artifact LEDs
Five different types of LEDs are used as comparison artifacts: RED (Nichia model
NSPR518S), GREEN (Nichia model NSPG518S), BLUE (Nichia model NSPB518S), WHITE
(Nichia model NSPW515BS), and DIFFUSER-TYPE GREEN (NSPG518S mounted in a
cylinder-type cap with an opal diffuser). All the bare LEDs had a lamp diameter of 5 mm
and were to be operated at a forward direct current of 20 mA. The detailed information
of the LEDs is included in the technical protocol (Appendix A).
Each set of artifact LEDs consisted of three pieces of the red (R), green (G), blue (B),
and white (W) LEDs and two pieces of the diffuser-type green (D) LEDs. They were
packaged and identified as shown in Fig. 3-1. The pilot prepared eight sets of artifact
LEDs for the LED comparisons S3a, S3b, and S3c. Each artifact LED is designated in a
form #N-X-M with three codes:
- #N as the artifact set number: N = 1, 2, …, 8
- X as LED color and type code: X = R for red, G for green, B for blue, W for white, D for
diffuser-type green
- M as sample serial number for each type: M = 1, 2, 3
Fig. 3-1. Artifact LED set circulated in the LED comparisons S3a, S3b, and S3c.
The artifact LEDs are prepared based on the functional seasoning 4 that records
4 Seongchong Park et al., Metrologia 43, 299 (2006).
APMP.PR-S3a Averaged LED Intensity Final Report
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during the pre-burning the relative change of luminous intensity and spectral distribution
of each individual LED together with its junction voltage under the ambient temperature
periodically varied from 18 °C to 33 °C. From the recorded data, the temporal drift and
the temperature dependence of the optical characteristics of each LED could be
separately determined. Each artifact LEDs has passed a seasoning procedure over 300
hours.
Since the photometric properties of LEDs have a very high dependence upon
temperature, their comparison requires a sensitive control or monitoring of the junction
temperature. As the junction voltage Vj of a LED can be approximated as a linear
function of the junction temperature T in a small interval, say ±10 °C, around a reference
temperature of T0,5 we can model the temperature dependence of the averaged LED
intensity ILED as a third-order polynomial with three coefficients:
2 3
0 0 0
0
1 ( ) ( ) ( ) ( ) ( ) ( )LED
j j j j j j
LED
I Ta V T V T b V T V T c V T V T
I T . (3-1)
The coefficients a, b, and c of each artifact LED could be determined by fitting the
function of Eq. (3-1) to the functional seasoning data. With these results, the pilot was
capable to calculate a temperature correction factor for the measurement result of any
artifact LED to the same measurement condition, as long as the junction voltage at the
time of measurement is known. The uncertainty of this correction factor is estimated to
be less than 0.5 % as a relative standard uncertainty from the goodness of fit for the
coefficients.
In the comparison S3a, the measurement condition was specified with an ambient
temperature of 25 °C. In addition, the junction voltage of each LED was to be recorded
to monitor the junction temperature and to apply the aforementioned temperature
correction. In the chapters 0~0, we will show and discuss this effect of the temperature
correction to the comparison results.
5 See, for example, E. F. Schubert, Light-Emitting Diodes (Cambrige University Press, 2003)
APMP.PR-S3a Averaged LED Intensity Final Report
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4. Measurement Capabilities of Participants
In this chapter, we summarize the information on measurement capabilities and
uncertainty budgets for averaged LED intensity, which are reported by each participant.
4.1. KRISS
4.1.1. Measurement setup
Fig. 4-1 shows the measurement setup of the averaged LED intensity. The main detector
is an illuminance meter with a circular aperture of 1 cm2 (P15F0T made by LMT). For
spectral mismatch correction and color measurement, we use a CCD-mounted
spectrograph-type spectroradiometer (CAS140CT-153 made by Instrument Systems), of
which the input optics is composed of a 1.5-inch integrating sphere and fiber bundle.
The aperture area of the integrating sphere is 1 cm2. It covers 380 nm to 1050 nm, and
its spectral bandwidth (FWHM) is about 3 nm at 633 nm. The detector holder is mounted
on a 5-axis stage.
The LED is driven by a source-meter unit (2400 source-meter made by Keithley),
which provides both of current sourcing and voltage measuring function. The DUT LED is
connected to the source-meter unit using 4-wire connection. As shown in Fig. 4-1 and
Fig. 4-2, the LED socket is cone-shaped and mounted on a 5-axis stage, which provides
4-wire electrical contacts to the LED.
Fig. 4-1. Averaged LED intensity measurement setup in KRISS.
illuminance meter
: 1 cm2 aperture
input optics of
spectroradiometer
: 1 cm2 aperture
telescope
for axis alignment
telescope
for distance alignment
baffle
detector
mountLED socket
detectors5-axis stage 5-axis stage
illuminance meter
: 1 cm2 aperture
input optics of
spectroradiometer
: 1 cm2 aperture
telescope
for axis alignment
telescope
for distance alignment
baffle
detector
mountLED socket
detectors5-axis stage 5-axis stage
APMP.PR-S3a Averaged LED Intensity Final Report
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Fig. 4-2. LED Measurement socket in KRISS.
4.1.2. Mounting and alignment
As shown in Fig. 4-1, there are two 5-axis stages and two telescope cameras. Using an
alignment laser and a couple of centering jigs (made of a precision reticule), the axis of
the optical bench is aligned, and successively the cameras position and tilt are adjusted.
One telescope camera is for distance alignment between the LED tip and the detector
aperture, and the other for axis alignment of the LED. Fig. 4-3 and Fig. 4-4 show how we
align the LED axis and the distance of LED tip to detector aperture.
Fig. 4-3. Axis alignment in KRISS.
Fig. 4-4. Distance alignment in KRISS.
slightly tilted well-alignedslightly tilted well-aligned
LED tip position Detector mount
position
LED Detector mount
LED tip position Detector mount
position
LED Detector mount
APMP.PR-S3a Averaged LED Intensity Final Report
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4.1.3. Traceability
For the illuminance meter, the illuminance responsivity is calibrated using a KRISS
working standard illuminance meter, and the relative spectral responsivity is calibrated
using a KRISS working standard photodiode. Both of scales are traceable to KRISS
cryogenic radiometer. For the spectroradiometer, the relative spectral responsivity is
calibrated using a spectral irradiance standard lamp traceable to NIST spectral irradiance
scale.
4.1.4. Measurement uncertainty
Tables in the following show the detailed uncertainty budgets of the CIE B averaged LED
intensity measurement for the LEDs used in this APMP LED comparison. The uncertainty
evaluation is carried out according to Guide to the Expression of Uncertainty in
Measurement (GUM). Expanded uncertainty are evaluated at a confidence level of
approximately 95% with a coverage factor normally k = 2. Table 4-6 is the detailed
uncertainty budget of the junction voltage measurement.
Table 4-1. KRISS uncertainty budget of averaged LED intensity measurement for red LEDs
(R).
Uncertainty Component Standard u
ncertainty
Ty
pe Probability
distributio
n
Sensitivity
coefficient
Contribut
ion (%)
DoF Corre
lated?
repeatability 0.00 % A t 1 0.00 9 N
axis alignment: angular 0.43 % B rectangular 1 0.43 N
axis alignment: translational 0.20 % B rectangular 1 0.20 N
current feeding 0.05 % B normal 1 0.05 Y
distance setting 0.44 % B rectangular 1 0.44 N
linearity 0.05 % B rectangular 1 0.05 Y
stray light 0.10 % B rectangular 1 0.10 Y
illuminance responsivity 0.50 % B normal 1 0.50 Y
CCF 0.25 % B normal 1 0.25 Y
reproducibility 0.63 % A t 1 0.63 >30 N
Combined standard uncertai
nty (%)
normal 1.07 >20
Table 4-2. KRISS uncertainty budget of averaged LED intensity measurement for green LEDs
(G).
Uncertainty Component Standard u
ncertainty
Ty
pe Probability
distributio
n
Sensitivity
coefficient
Contribut
ion (%)
DoF Corre
lated?
APMP.PR-S3a Averaged LED Intensity Final Report
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repeatability 0.00 % A t 1 0.00 9 N
axis alignment: angular 0.33 % B rectangular 1 0.33 N
axis alignment: translational 0.10 % B rectangular 1 0.10 N
current feeding 0.03 % B normal 1 0.03 Y
distance setting 0.48 % B rectangular 1 0.48 N
linearity 0.05 % B rectangular 1 0.05 Y
stray light 0.10 % B rectangular 1 0.10 Y
illuminance responsivity 0.50 % B normal 1 0.50 Y
CCF 0.18 % B normal 1 0.18 Y
reproducibility 0.62 % A t 1 0.62 >30 N
Combined standard uncertai
nty (%)
normal 1.02 >20
Table 4-3. KRISS uncertainty budget of averaged LED intensity measurement for blue LEDs
(B).
Uncertainty Component Standard u
ncertainty
Ty
pe Probability
distributio
n
Sensitivity
coefficient
Contribut
ion
DoF Corre
lated?
repeatability 0.00 % A t 1 0.00 9 N
axis alignment: angular 0.23 % B rectangular 1 0.23 N
axis alignment: translational 0.10 % B rectangular 1 0.10 N
current feeding 0.04 % B normal 1 0.04 Y
distance setting 0.44 % B rectangular 1 0.44 N
linearity 0.05 % B rectangular 1 0.05 Y
stray light 0.10 % B rectangular 1 0.10 Y
illuminance responsivity 0.50 % B normal 1 0.50 Y
CCF 0.37 % B normal 1 0.37 Y
reproducibility 0.70 % A t 1 0.70 >30 N
Combined standard uncertai
nty (%)
normal 1.07 >20
Table 4-4. KRISS uncertainty budget of averaged LED intensity measurement for white LEDs
(W).
Uncertainty Component Standard u
ncertainty
Ty
pe Probability
distributio
n
Sensitivity
coefficient
Contribut
ion
DoF Corre
lated?
repeatability 0.00 % A t 1 0.00 9 N
axis alignment: angular 0.03 % B rectangular 1 0.03 N
axis alignment: translational 0.10 % B rectangular 1 0.10 N
current feeding 0.04 % B normal 1 0.04 Y
APMP.PR-S3a Averaged LED Intensity Final Report
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distance setting 0.44 % B rectangular 1 0.44 N
linearity 0.05 % B rectangular 1 0.05 Y
stray light 0.10 % B rectangular 1 0.10 Y
illuminance responsivity 0.50 % B normal 1 0.50 Y
CCF 0.04 % B normal 1 0.04 Y
reproducibility 0.39 % A t 1 0.39 >30 N
Combined standard uncertai
nty (%)
normal 0.79 >20
Table 4-5. KRISS uncertainty budget of averaged LED intensity measurement for diffuser-type
green LEDs (D).
Uncertainty Component Standard u
ncertainty
Ty
pe Probability
distributio
n
Sensitivity
coefficient
Contribut
ion
DoF Corre
lated?
repeatability 0.00 % A t 1 0.00 9 N
axis alignment: angular 0.02 % B rectangular 1 0.02 N
axis alignment: translational 0.10 % B rectangular 1 0.10 N
current feeding 0.00 % B normal 1 0.00 Y
distance setting 0.48 % B rectangular 1 0.48 N
linearity 0.05 % B rectangular 1 0.05 Y
stray light 0.10 % B rectangular 1 0.10 Y
illuminance responsivity 0.50 % B normal 1 0.50 Y
CCF 0.18 % B normal 1 0.18 Y
reproducibility 0.14 % A t 1 0.14 >30 N
Combined standard uncertai
nty (%)
normal 0.75 >20
Table 4-6. KRISS uncertainty budget of junction voltage measurement.
Uncertainty Component Standard u
ncertainty
Ty
pe Probability
distributio
n
Sensitivity
coefficient
Contribut
ion (mV)
DoF Corre
lated?
sourcemeter calibration 0.05 mV B normal 1 0.05 Y
sourcemeter offset 0.10 mV B normal 1 0.10 Y
repeatability 0.04 mV A t 1 0.04 9 N
stray resistance 0.02 mV B rectangular 1 0.02 Y
Combined standard uncertai
nty (mV)
normal 0.12 >20
APMP.PR-S3a Averaged LED Intensity Final Report
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4.2. MIKES
4.2.1. Measurement setup
A photometer, which was used for measuring the photocurrent signal, was LMT P11 SOT.
The photometer has an aperture area of 1 cm2. The relative spectral responsivity of the
photometer has been calibrated with a reference spectrometer of MIKES. The illuminance
responsivity of the photometer has been calibrated against a reference trap photometer
of MIKES using the light source at a color temperature of 2856 K.
For calculating the spectral mismatch correction factor of LEDs under comparison,
a spectroradiometer of type DM150 from Bentham Inc. was used for measuring spectral
power distribution of the LEDs.
The averaged LED intensity measurements for each LED were made at 10-cm
distance from the front tip of the LED to the entrance aperture of the photometer. To
calculate the spectral mismatch correction factor, the relative spectral power distributions
were measured by steps of 1 nm within the wavelength range of 380-780 nm and the
relative spectral responsivity of the used photometer was measured by steps of 2 nm
within the wavelength range of 380-780 nm. During the measurements, the ambient
temperature was (21.5 ± 1.0) °C and the relative humidity of air was (31 ± 5) °C.
4.2.2. Mounting and alignment
The detectors and an LED holder (see Fig. 4-5) were mounted to a measurement rail. The
LED under calibration was mounted on an optical table using an x-y translator, a rotary
stage, and a tilt stage. The detectors were mounted to the rail carrier using a magnetic
base plate and tilt stages. The detectors and the LED under calibration were mounted on
the same optical axis using a two-beam alignment laser. The detectors were aligned
using an auxiliary mirror to get the back-reflection into the alignment laser. The
translational alignment of the LEDs was made by an x-y translator so that the laser beam
hit the tip of the LED. An angular alignment of the LEDs was made by a digital camera,
rotary stage, and tilt stage. The distance from the front tip of the LED to the entrance
aperture of the photometer was measured using a magnetic length measurement rail.
APMP.PR-S3a Averaged LED Intensity Final Report
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Fig. 4-5. Photographs of the LED holder used in the measurement of the averaged LED
intensity B in MIKES.
4.2.3. Traceability
The illuminance responsivity of the photometer used is traceable to MIKES’ reference
photometer. The reference photometer includes a precision aperture, a V(λ) filter, and a
silicon trap detector. The absolute transmittance of the V(λ) filter is traceable to the
national standard of the regular transmittance [Calibration certificate T-R 479]. The
spectral responsivity of the trap detector is traceable to a cryogenic electrical substitution
radiometer at SP in Sweden [Calibration certificate MTeP501362-025] and modeling the
spectral shape [Calibration certificate INT-028]. The determination of the area of the
precision aperture and the distance are traceable to the realization of the meter at MIKES
[Calibration certificates M-07L193 and M-08L357]. The spectral irradiance responsivity of
the spectroradiometer is traceable to the national standard of spectral irradiance
[Calibration certificate T-R 506]. The calibrations of the current-to-voltage converter
Vinculum SP042 and digital voltmeter HP 3458A are traceable to the national standards
of electricity [Calibration certificates INT-033, INT-032].
4.2.4. Measurement uncertainty
Uncertainty budgets for the averaged LED intensity B and the junction voltage of the
LEDs are presented in Tables below. The sensitivity coefficients of the uncertainty
components have been calculated as the ratio between the relative standard uncertainty
of the component and the standard deviation of the probability distribution of the
component. The uncertainty components of spectral mismatch correction are based on
Monte Carlo simulations.
Table 4-7. MIKES uncertainty budget of averaged LED intensity measurement for red LEDs
(R).
APMP.PR-S3a Averaged LED Intensity Final Report
17
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Setup-related
Repeatability 1.41 % A normal 1 1.41 11 X
LED alignment, angular
tilting
B rectangular 0.09 –
0.81 %/1°
0.79 ∞ X
LED alignment,
translational centering
B rectangular 0.2 –
1.4 %/mm
0.08 ∞ X
Photometer alignment 0.6° B rectangular 0.07 %/1° 0.04 ∞ X
Current feeding B rectangular 3 –
5 %/mA
0.03 ∞ O
Distance setting 0.095 mm B rectangular 1.9 %/mm 0.18 ∞ X
Stray light 0.10 % B rectangular 1 0.10 ∞ O
Photocurrent measurement 0.03 % A normal 1 0.03 19 X
Photometer
Illuminance responsivity 0.20 B normal 1 0.20 ∞ O
Long-term stability 0.10 B rectangular 1 0.10 ∞ O
Spectral mismatch
correction
Wavelength error in
spectral response of
photometer
B normal 0.7 –
4.8 %/nm
0.17 ∞ O
Relative spectral response
of the photometer
0.22 B rectangular 1 0.22 ∞ O
Wavelength error in LED
spectrum
B normal 0.05 –
0.25 %/nm
0.04 ∞ X
Measurement noise in LED
spectrum
0.03 B rectangular 1 0.03 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 1.67 22 --
Table 4-8. MIKES uncertainty budget of averaged LED intensity measurement for green LEDs
(G).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Setup-related
APMP.PR-S3a Averaged LED Intensity Final Report
18
Repeatability 1.41 % A normal 1 1.41 11 X
LED alignment, angular
tilting
B rectangular 0.09 –
0.81 %/1°
0.92 ∞ X
LED alignment,
translational centering
B rectangular 0.2 –
1.4 %/mm
0.04 ∞ X
Photometer alignment 0.6° B rectangular 0.07 %/1° 0.04 ∞ X
Current feeding B rectangular 3 –
5 %/mA
0.02 ∞ O
Distance setting 0.095 mm B rectangular 1.9 %/mm 0.18 ∞ X
Stray light 0.10 % B rectangular 1 0.10 ∞ O
Photocurrent measurement 0.03 % A normal 1 0.03 19 X
Photometer
Illuminance responsivity 0.20 B normal 1 0.20 ∞ O
Long-term stability 0.10 B rectangular 1 0.10 ∞ O
Spectral mismatch
correction
Wavelength error in
spectral response of
photometer
B normal 0.7 –
4.8 %/nm
0.15 ∞ O
Relative spectral response
of the photometer
0.22 B rectangular 1 0.22 ∞ O
Wavelength error in LED
spectrum
B normal 0.05 –
0.25 %/nm
0.04 ∞ X
Measurement noise in LED
spectrum
0.03 B rectangular 1 0.03 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 1.73 25 --
Table 4-9. MIKES uncertainty budget of averaged LED intensity measurement for blue LEDs
(B).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Setup-related
Repeatability 1.41 % A normal 1 1.41 11 X
LED alignment, angular
tilting
B rectangular 0.09 –
0.81 %/1°
0.70 ∞ X
LED alignment,
translational centering
B rectangular 0.2 –
1.4 %/mm
0.03 ∞ X
APMP.PR-S3a Averaged LED Intensity Final Report
19
Photometer alignment 0.6° B rectangular 0.07 %/1° 0.04 ∞ X
Current feeding B rectangular 3 –
5 %/mA
0.02 ∞ O
Distance setting 0.095 mm B rectangular 1.9 %/mm 0.18 ∞ X
Stray light 0.10 % B rectangular 1 0.10 ∞ O
Photocurrent measurement 0.03 % A normal 1 0.03 19 X
Photometer
Illuminance responsivity 0.20 B normal 1 0.20 ∞ O
Long-term stability 0.10 B rectangular 1 0.10 ∞ O
Spectral mismatch
correction
Wavelength error in
spectral response of
photometer
B normal 0.7 –
4.8 %/nm
0.29 ∞ O
Relative spectral response
of the photometer
0.22 B rectangular 1 0.33 ∞ O
Wavelength error in LED
spectrum
B normal 0.05 –
0.25 %/nm
0.05 ∞ X
Measurement noise in LED
spectrum
0.03 B rectangular 1 0.03 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 1.66 21 --
Table 4-10. MIKES uncertainty budget of averaged LED intensity measurement for white
LEDs (W).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Setup-related
Repeatability 1.41 % A normal 1 1.41 11 X
LED alignment, angular
tilting
B rectangular 0.09 –
0.81 %/1°
0.85 ∞ X
LED alignment,
translational centering
B rectangular 0.2 –
1.4 %/mm
0.04 ∞ X
Photometer alignment 0.6° B rectangular 0.07 %/1° 0.04 ∞ X
Current feeding B rectangular 3 –
5 %/mA
0.03 ∞ O
Distance setting 0.095 mm B rectangular 1.9 %/mm 0.18 ∞ X
APMP.PR-S3a Averaged LED Intensity Final Report
20
Stray light 0.10 % B rectangular 1 0.10 ∞ O
Photocurrent measurement 0.03 % A normal 1 0.03 19 X
Photometer
Illuminance responsivity 0.20 B normal 1 0.20 ∞ O
Long-term stability 0.10 B rectangular 1 0.10 ∞ O
Spectral mismatch
correction
Wavelength error in
spectral response of
photometer
B normal 0.7 –
4.8 %/nm
0.04 ∞ O
Relative spectral response
of the photometer
0.22 B rectangular 1 0.05 ∞ O
Wavelength error in LED
spectrum
B normal 0.05 –
0.25 %/nm
< 0.01 ∞ X
Measurement noise in LED
spectrum
0.03 B rectangular 1 0.10 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 1.68 22 --
Table 4-11. MIKES uncertainty budget of averaged LED intensity measurement for diffuser-
type green LEDs (D).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Setup-related
Repeatability 0.50 % A normal 1 0.50 5 X
LED alignment, angular
tilting
B rectangular 0.09 –
0.81 %/1°
0.10 ∞ X
LED alignment,
translational centering
B rectangular 0.2 –
1.4 %/mm
0.01 ∞ X
Photometer alignment 0.6° B rectangular 0.07 %/1° 0.04 ∞ X
Current feeding B rectangular 3 –
5 %/mA
0.02 ∞ O
Distance setting 0.095 mm B rectangular 1.9 %/mm 0.18 ∞ X
Stray light 0.10 % B rectangular 1 0.10 ∞ O
Photocurrent measurement 0.03 % A normal 1 0.03 19 X
Photometer
APMP.PR-S3a Averaged LED Intensity Final Report
21
Illuminance responsivity 0.20 B normal 1 0.20 ∞ O
Long-term stability 0.10 B rectangular 1 0.10 ∞ O
Spectral mismatch
correction
Wavelength error in
spectral response of
photometer
B normal 0.7 –
4.8 %/nm
0.15 ∞ O
Relative spectral response
of the photometer
0.22 B rectangular 1 0.21 ∞ O
Wavelength error in LED
spectrum
B normal 0.05 –
0.25 %/nm
0.04 ∞ X
Measurement noise in LED
spectrum
0.03 B rectangular 1 0.10 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 0.66 15 --
Table 4-12. MIKES uncertainty budget of junction voltage measurement for red LEDs (R).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(mV)
Deg. of
freedo
m
Correl
ated?
Calibration of voltmeter B normal 1 0.02 ∞ O
Junction position
dependence
B rectangular 1 0.03 ∞ X
Stability of junction voltage A normal 1 0.05 –
0.13
19 X
Combined standard unce
rtainty (mV)
-- -- normal -- 0.06 –
0.14
26 -
39
--
Table 4-13. MIKES uncertainty budget of junction voltage measurement for green LEDs (G).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(mV)
Deg. of
freedo
m
Correl
ated?
Calibration of voltmeter B normal 1 0.03 ∞ O
Junction position
dependence
B rectangular 1 0.12 ∞ X
Stability of junction voltage A normal 1 0.15 –
0.33
19 X
Combined standard unce
rtainty (mV)
-- -- normal -- 0.19 –
0.35
24 -
49
--
Table 4-14. MIKES uncertainty budget of junction voltage measurement for blue LEDs (B).
APMP.PR-S3a Averaged LED Intensity Final Report
22
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(mV)
Deg. of
freedo
m
Correl
ated?
Calibration of voltmeter B normal 1 0.03 ∞ O
Junction position
dependence
B rectangular 1 0.10 ∞ X
Stability of junction voltage A normal 1 0.21 –
0.28
19 X
Combined standard unce
rtainty (mV)
-- -- normal -- 0.24 –
0.30
25 -
32
--
Table 4-15. MIKES uncertainty budget of junction voltage measurement for white LEDs (W).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(mV)
Deg. of
freedo
m
Correl
ated?
Calibration of voltmeter B normal 1 0.03 ∞ O
Junction position
dependence
B rectangular 1 0.20 ∞ X
Stability of junction voltage A normal 1 0.14 –
0.36
19 X
Combined standard unce
rtainty (mV)
-- -- normal -- 0.25 –
0.42
35 -
193
--
Table 4-16. MIKES uncertainty budget of junction voltage measurement for diffuser-type
green LEDs (D).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(mV)
Deg. of
freedo
m
Correl
ated?
Calibration of voltmeter B normal 1 0.03 ∞ O
Junction position
dependence
B rectangular 1 0.07 ∞ X
Stability of junction voltage A normal 1 0.11 –
0.12
19 X
Combined standard unce
rtainty (mV)
-- -- normal -- 0.14 –
0.15
46 -
50
--
APMP.PR-S3a Averaged LED Intensity Final Report
23
4.3. CMS-ITRI
4.3.1. Measurement setup
As Fig. 4-6, the test LED is located by a mount system and the mechanism axis of LED
and detector is the same axis following the CIE 127:2007 standard. The distance between
LED and detector that using CIE condition B is 100 mm. Using the DC multiple standard
resistor, two voltage meter and DC power supply that give the LED current and monitor
the current and voltage of the junction of LED. The detector is the V(λ) optical detector
that have 100 mm2 circular aperture area and connect the optical current meter for
getting the optical signal.
Fig. 4-6. Averaged LED luminance intensity measurement system in CMS-ITRI.
4.3.2. Mounting and alignment
The LED is mounting by a holder that has two pins connect and has two wires at the end
of holder for power current connecting. The holder is located at the top of the multiple
stages that have rotating and movement stages for alignment. By using two alignment
CCDs to check the mechanical axis of LED align to the axis of setting optical axis that is
using the two lasers for setting previously.
Detector
(100 mm2 circular aperture
) LED
Alignment CCD
Alignment CCD
100 mm
APMP.PR-S3a Averaged LED Intensity Final Report
24
Fig. 4-7. LED Mounting and alignment system in CMS-ITRI.
4.3.3. Traceability
The traceability of LED averaged intensity is the V(λ) detector. The absolute response
[nA/lx] of detector is calibrated by absolute radiometer. The spectral response of optical
detector is trace to the standard optical detector by spectroradiometric system, then the
standard optical detector trace to the cryogenic radiometer system.
Fig. 4-8. Traceability of measurement system in CMS-ITRI.
Candela
definition
Absolute radiometer
Optical detector
Standard optical dete
ctor
Cryogenic radiometer
system
Spectroradiometric
System
Test LED
LED holder
Multiple stages
APMP.PR-S3a Averaged LED Intensity Final Report
25
4.3.4. Measurement uncertainty
Uncertainty budget of averaged LED intensity measurement:
1. Repeatability of test LED:
The repeatability of test LED is record the optical current by using current meter several
times a day and measure several days. Calculate the standard deviation of all the data.
2. LED spatial lighting distribution:
Due to the general LED have non-uniform lighting distribution. By rotating the LED
around mechanical axis consider the misalignment error from this effect.
3. LED mechanical axis alignment:
The LED mechanical axis must coaxial of system optical axis. Consider the maximum
deviation of misalignment by rotating the LED at horizontal plane.
4. Distance setting:
Because the LED averaged intensity is calculated by Inverse Square’s law, the shorter
measurement distances the more effect from deviation of measurement distance.
Consider the maximum alignment error causing the deviation of the result.
5. Photometer calibration:
The uncertainty of standard photometer is drive from the relative expand uncertainty
calibrated by National measurement laboratory (NML) in Taiwan.
6. Spectral mismatch correction:
Because of the correction of spectrometer which the wavelength shifts affect the spectral
correction factor (SCF). Consider the wavelength shifts cause the error of SCF.
Uncertainty budget of junction voltage measurement:
1. Repeatability of test LED:
The repeatability of test LED is record the junction voltage by using voltage meter several
times a day and measure several days when measuring the LED averaged intensity.
Calculate the standard deviation of all the data.
2. Resolution of voltmeter:
To consider the drift when measure the junction voltage that is the maximum digit of
voltage meter.
3. Long-term drift of voltmeter:
Long-term drift of voltmeter is the drift of the traceability since the past. Calculate the
maximum deviation of the uncertainty drift.
4. Voltmeter calibration:
The uncertainty of voltmeter is drive from the relative expand uncertainty calibrated by
APMP.PR-S3a Averaged LED Intensity Final Report
26
National measurement laboratory (NML) in Taiwan.
Table 4-17. CMS-ITRI uncertainty budget of averaged LED intensity measurement for red
LEDs (R).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Repeatability 0.037 A t 1 0.037 87 X
LED spatial light
distribution
1.462 B rectangular 1 1.462 200 O
LED mechanical axis
alignment
0.148 B rectangular 1 0.148 200 O
Distance setting 0.143 B rectangular 4 0.575 200 O
Photometer calibration 0.50 B normal 1 0.50 5000 O
Spectral mismatch
correction
0.004 B rectangular 1 0.004 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 1.93 595 --
Table 4-18. CMS-ITRI uncertainty budget of averaged LED intensity measurement for green
LEDs (G).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Repeatability 0.027 A t 1 0.027 87 X
LED spatial light
distribution
1.462 B rectangular 1 1.462 200 O
LED mechanical axis
alignment
0.148 B rectangular 1 0.148 200 O
Distance setting 0.143 B rectangular 4 0.575 200 O
Photometer calibration 0.50 B normal 1 0.50 5000 O
Spectral mismatch
correction
0.004 B rectangular 1 0.004 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 1.93 594 --
Table 4-19. CMS-ITRI uncertainty budget of averaged LED intensity measurement for blue
LEDs (B).
APMP.PR-S3a Averaged LED Intensity Final Report
27
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Repeatability 0.028 A t 1 0.028 87 X
LED spatial light
distribution
1.462 B rectangular 1 1.462 200 O
LED mechanical axis
alignment
0.148 B rectangular 1 0.148 200 O
Distance setting 0.143 B rectangular 4 0.575 200 O
Photometer calibration 0.50 B normal 1 0.50 5000 O
Spectral mismatch
correction
0.474 B rectangular 1 0.474 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 1.99 661 --
Table 4-20. CMS-ITRI uncertainty budget of averaged LED intensity measurement for white
LEDs (W).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Repeatability 0.035 A t 1 0.035 87 X
LED spatial light
distribution
1.462 B rectangular 1 1.462 200 O
LED mechanical axis
alignment
0.148 B rectangular 1 0.148 200 O
Distance setting 0.143 B rectangular 4 0.575 200 O
Photometer calibration 0.50 B normal 1 0.50 5000 O
Spectral mismatch
correction
0.002 B rectangular 1 0.002 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 1.93 595 --
Table 4-21. CMS-ITRI uncertainty budget of averaged LED intensity measurement for
diffuser-type green LEDs (D).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
APMP.PR-S3a Averaged LED Intensity Final Report
28
Repeatability 0.026 A t 1 0.026 87 X
LED spatial light
distribution
1.462 B rectangular 1 1.462 200 O
LED mechanical axis
alignment
0.148 B rectangular 1 0.148 200 O
Distance setting 0.143 B rectangular 4 0.575 200 O
Photometer calibration 0.50 B normal 1 0.50 5000 O
Spectral mismatch
correction
0.002 B rectangular 1 0.002 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 1.93 594 --
Table 4-22. CMS-ITRI uncertainty budget of junction voltage measurement for red LEDs (R).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Repeatability 0.060 A t 1 0.060 200 X
Resolution of voltmeter 0.003 B rectangular 1 0.003 200 O
Long-term drift of voltme
ter
0.026 B rectangular 1 0.026 200 O
Voltmeter calibration 0.001 B normal 1 0.001 5000 O
Combined standard unce
rtainty (%)
-- -- normal -- 0.06 282 --
Table 4-23. CMS-ITRI uncertainty budget of junction voltage measurement for green LEDs
(G).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Repeatability 0.180 A t 1 0.180 200 X
Resolution of voltmeter 0.003 B rectangular 1 0.003 200 O
Long-term drift of voltme
ter
0.026 B rectangular 1 0.026 200 O
Voltmeter calibration 0.001 B normal 1 0.001 5000 O
APMP.PR-S3a Averaged LED Intensity Final Report
29
Combined standard unce
rtainty (%)
-- -- normal -- 0.18 208 --
Table 4-24. CMS-ITRI uncertainty budget of junction voltage measurement for blue LEDs (B).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Repeatability 0.140 A t 1 0.140 200 X
Resolution of voltmeter 0.003 B rectangular 1 0.003 200 O
Long-term drift of voltme
ter
0.026 B rectangular 1 0.026 200 O
Voltmeter calibration 0.001 B normal 1 0.001 5000 O
Combined standard unce
rtainty (%)
-- -- normal -- 0.14 215 --
Table 4-25. CMS-ITRI uncertainty budget of junction voltage measurement for white LEDs
(W).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Repeatability 0.090 A t 1 0.090 200 X
Resolution of voltmeter 0.003 B rectangular 1 0.003 200 O
Long-term drift of voltme
ter
0.026 B rectangular 1 0.026 200 O
Voltmeter calibration 0.001 B normal 1 0.001 5000 O
Combined standard unce
rtainty (%)
-- -- normal -- 0.09 234 --
Table 4-26. CMS-ITRI uncertainty budget of junction voltage measurement for diffuser-type
green LEDs (D).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Repeatability 0.060 A t 1 0.060 200 X
Resolution of voltmeter 0.003 B rectangular 1 0.003 200 O
APMP.PR-S3a Averaged LED Intensity Final Report
30
Long-term drift of voltme
ter
0.026 B rectangular 1 0.026 200 O
Voltmeter calibration 0.001 B normal 1 0.001 5000 O
Combined standard unce
rtainty (%)
-- -- normal -- 0.07 267 --
4.4. PTB
4.4.1. Measurement setup
Fig. 4-9 below shows the measurement setup in principle. To enable the measurement of
all the desired quantities, a special mechanism is needed. This allows the following
functionality: the alignment of the LED transfer standard to the optical axis of the system,
the rotation of the LED transfer standard around its horizontal axis φ and rotation
around its vertical axis θ. Furthermore, it allows the variation of the distance r between
the selected detector and the LED transfer standard. Opposite the LED transfer standard,
a rotating wheel is used for a quick detector selection. Additionally, there is a laser and a
CCD camera mounted to enable the easy alignment of the LED transfer standard. Due to
the rotation of φ angle, the interconnection between the power supply and the LED
under test prohibits an endless rotation.
Thus, in the case of luminous flux measurements after a little more than one
rotation, a stop is needed. The next movement will then be the turn back and so on.
Fig. 4-9. Measurement setup for averaged LED intensity in PTB.
APMP.PR-S3a Averaged LED Intensity Final Report
31
4.4.2. Mounting and alignment
Fig. 4-10 below shows the holder which was used to hold, align and operate each LED. A
high reflecting cone directly behind the installed LED allows for the indirect measurement
of the backward directed partial luminous flux of the LEDs, which also contributes to the
total luminous flux.
Fig. 4-10. Pictures of the LED holder used in the measurement of the averaged LED intensity in
PTB.
4.4.3. Traceability
The primary standards for the measured quantities are traceable to national standards.
4.4.4. Measurement uncertainty
The uncertainties are determined from up to 30 individual contributions originated in the
operation and alignment of an LED in thermal conditions influenced by the holder and
the environment. The specific properties of the measurement devices and their effects
are considered in detail. The estimated uncertainties of the contributions are maximum
for standard LED calibrations at PTB. They are listed and sorted in uncertainty budgets.
The components are treated as uncorrelated.
The next statement shows the model of determining ILED,B further on called J0:
The meaning, of input data and their uncertainties of the used variables of the model
above is given by the following table for example of a blue LED:
APMP.PR-S3a Averaged LED Intensity Final Report
32
To find the uncertainty in angular alignment of an LED, several persons tried to
align the LED concerning the technical protocol (page 10, Fig. 5) by help of a two-axis
support (with ruler) and a CCD camera connected to a screen. A repeatability of 0.47°
was found, which was affected by the shape and color of the LED package up to a factor
of 1.5 larger. This maximum value is taken as standard uncertainty for the angular
alignment of the LED package.
The translational alignment of an LED is taken as the difference between the tip of
the LED and the center of the measuring system. Again from test with several persons,
the repeatability for centering the LED is estimated to be within 0.4 mm in both
directions in the yz-plane. This deviation is slightly affected by the shape and the color of
the LED package up to a factor of 1.5 larger. Due to the use of a gauge block, the
distance to the photometer is much smaller and contributions from bad repeatability are
considered during luminous intensity determination.
The angular luminous intensity distribution of the LED simulated with the
uncertainty in the alignment influences the averaged luminous intensity of the LED. Since
the luminous flux of the LED is measured by help of a goniophotometer, the angular
distribution is well known and can be approximated in the range of θ (0° < θ < 2.5°) by
the function cos(abs(θ))g. In case of the blue LEDs the values of g = 39 was found.
To simulate the effect of angular and translational uncertainty to luminous
intensity a simulated photometer is introduced. It consists of a number of small
photometers with hexagon shape (finite elements) with the same sensitivity.
To correct the temperature depending change of the LED voltage during the
measurements, the knowledge of the LED voltage at Tambient = 25 °C is needed. For this
purpose the LED was operated in an integrating sphere at different ambient
temperatures.
APMP.PR-S3a Averaged LED Intensity Final Report
33
During measurements of value of the photometric quantities of the LED, the LED
current and LED voltage may drift a little. This causes a change of the photometric values
of the LED. To correct this, two exponents (a and b) for a model are needed. During the
measurements of temperature dependence, the photocurrent of the integrating sphere's
photometer was measured, too. This allows the determination of the fit parameters a and
b.
For determination of the spectral mismatch correction factor and it's standard
measurement uncertainty, a Monte Carlo Simulation was used.
Table 4-27. PTB uncertainty budget of averaged LED intensity measurement for red LEDs (R).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
LED nominal current 0 A 24.8416 0
Exponent LED current
correction
0.36 B normal 0 0 13
Photocurrent amplifier dark
reading
2.4E-7 V A normal -0.115168 -4.0E-6 10
LED voltage reading 0.0006 V A normal -2.06328 -0.17 10
LED current reading 2.0E-6 A A normal -24.8416 -0.0069 10
Photocurrent amplifier
reading
6.3E-4 V A normal 0.115 0.010 10
Exponent LED voltage
correction
1.6 B normal 6.85E-4 0.15 13
Gain of photocurrent
amplifier
646 Ω A normal -2.24E-7 -0.020 10
LED nominal voltage for
25 °C
7.31E-4 V A normal 2.06132 0.21 9
Correction factor for
straylight
0.00050 B normal 0.722602 0.050 10
Bandbass correction of
spectrometer
0.0011 B normal 0.72253 0.011 50
Straylight correction of
spectrometer
5.0E-5 B normal 0.72253 5.0E-3 50
Correction for LED
translational align
4.1E-4 B normal 0.72253 0.041 10
Photometric sensitivity of
photometer
8.9E-11
A/lx
B normal -2.61E7 -0.32 10
Distance setting 0.0002 m B rectangular 14.4506 0.40 10
APMP.PR-S3a Averaged LED Intensity Final Report
34
Correction for LED angular
align
0.0021 B normal 0.72253 0.21 10
Spectral mismatch
correction factor
0.0078 B normal 0.704358 0.76 50
Combined standard unce
rtainty (%)
-- -- normal -- 0.99 89 -
Table 4-28. PTB uncertainty budget of averaged LED intensity measurement for green LEDs
(G).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
LED nominal current 0 A 70.9263 0
Exponent LED current
correction
0.13 B normal 0 0 13
Photocurrent amplifier dark
reading
2.4E-7 V A normal -1.11521 -9.4E-6 10
LED voltage reading 1.1E-3 V A normal -1.30284 -0.052 10
LED current reading 2.0E-6 A A normal -70.9263 -5.1E-3 10
Photocurrent amplifier
reading
2.5E-4 V A normal 1.11521 1E-2 10
Exponent LED voltage
correction
0.45 B normal 4.73E-3 0.076 13
Gain of photocurrent
amplifier
65 Ω A normal -8.69E-6 -0.020 10
LED nominal voltage for
25 °C
0.0026 V A normal 1.3 0.12 9
Correction factor for
straylight
0.00050 B normal 2.81 0.050 10
Bandbass correction of
spectrometer
1.0E-4 B normal 2.81 0.010 50
Straylight correction of
spectrometer
3.0E-5 B normal 2.81 0.0030 50
Correction for LED
translational align
3.0E-4 B normal 2.8 0.030 10
Photometric sensitivity of
photometer
8.9E-11
A/lx
B normal -1.0E8 -0.32 10
Distance setting 0.00020 m B rectangular 56.2 0.40 10
Correction for LED angular
align
0.0011 B normal 2.81 0.11 10
Spectral mismatch
correction factor
0.0035 B normal 2.82 0.35 50
APMP.PR-S3a Averaged LED Intensity Final Report
35
Combined standard unce
rtainty (%)
-- -- normal -- 0.65 45 --
Table 4-29. PTB uncertainty budget of averaged LED intensity measurement for blue LEDs (B).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
LED nominal current 0 A normal 29.7646 0 ∞
Exponent LED current
correction
0.028 B normal 0 0 13
Photocurrent amplifier dark
reading
7.5E-8 V A normal -0.320674 -3.0E-6 10
LED voltage reading 0.79E-3 V A normal -0.115157 -0.011 10
LED current reading 2.0E-6 A A normal -29.7646 -0.0073 10
Photocurrent amplifier
reading
2.5E-4 V A normal 0.320674 0.010 10
Exponent LED voltage
correction
0.1022 B normal 0.0010674 0.013 13
Gain of photocurrent
amplifier
200 Ω A normal -8.1451E-7 -0.020 10
LED nominal voltage for
25 °C
0.0017 V A normal 0.115006 0.024 9
Correction factor for
straylight
0.00050 B normal 0.814303 0.050 10
Bandbass correction of
spectrometer
0.0010 B normal 0.814221 0.10 50
Straylight correction of
spectrometer
0.0010 B normal 0.814221 0.10 50
Correction for LED
translational align
0.0010 B normal 0.814221 0.10 10
Photometric sensitivity of
photometer
8.9E-11
A/lx
B normal -2.9384E7 -0.32 10
Distance setting 0.00020 m B rectangular 16.2844 0.40 10
Correction for LED angular
align
5.7E-3 B normal 0.814221 0.57 10
Spectral mismatch
correction factor
0.0071 B normal 0.917122 0.80 50
Combined standard unce
rtainty (%)
-- -- normal -- 1.10 71 --
Table 4-30. PTB uncertainty budget of averaged LED intensity measurement for white LEDs
(W).
APMP.PR-S3a Averaged LED Intensity Final Report
36
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contribut
ion (%)
Deg.
of fre
edom
Correl
ated?
LED nominal current 0 A normal 25.6011 0 ∞
Exponent LED current
correction
0.21 B normal -3.46E-6 -1.0E-4 13
Photocurrent amplifier dark
reading
2.4E-7 V A normal -0.111457 -3.8E-6 10
LED voltage reading 0.0011 V A normal -0.551501 -0.090 10
LED current reading 2.0E-6 A A normal -25.601 -7.4E-3 10
Photocurrent amplifier
reading
6.2E-4 V A normal 0.11 0.010 10
Exponent LED voltage
correction
0.61 B normal 6.94E-3 0.061 13
Gain of photocurrent
amplifier
646 Ω A normal -2.14E-7 -0.02 10
LED nominal voltage for
25 °C
2.5E-3 V A normal 0.550948 0.2 9
Correction factor for
straylight
0.00050 B normal 0.691747 0.050 10
Bandbass correction of
spectrometer
4.0E-5 B normal 0.691678 4.0E-3 50
Straylight correction of
spectrometer
1E-5 B normal 0.691678 1.0E-3 50
Correction for LED
translational align
1.6E-4 B normal 0.691678 0.016 10
Photometric sensitivity of
photometer
8.9E-11
A/lx
B normal -2.5E7 -0.32 10
Distance setting 0.00020 m B rectangular 13.8336 0.40 10
Correction for LED angular
align
4.1E-4 B normal 0.691678 4.1E-2 10
Spectral mismatch
correction factor
0.0023 B normal 0.695083 0.23 50
Combined standard unce
rtainty (%)
-- -- normal -- 0.61 36 --
Table 4-31. PTB uncertainty budget of averaged LED intensity measurement for diffuser-type
green LEDs (D).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
APMP.PR-S3a Averaged LED Intensity Final Report
37
LED nominal current 0 A normal 2.00106 0 ∞
Exponent LED current
correction
0.12 B normal 0 0 13
Photocurrent amplifier dark
reading
7.6E-8 V A normal -0.036 -3.2E-6 10
LED voltage reading 0.0008 V A normal -0.058 -0.054 10
LED current reading 2.0E-6 A A normal -2.00106 -4.7E-3 10
Photocurrent amplifier
reading
2.4E-4 V A normal 0.0359941 0.010 10
Exponent LED voltage
correction
0.45 B normal 6.6661E-5 0.035 13
Gain of photocurrent
amplifier
2000 Ω A normal -8.6E-9 -0.020 10
LED nominal voltage for
25 °C
0.0017 V A normal 0.0578258 0.012 9
Correction factor for
straylight
0.00050 B normal 0.0860311 0.050 10
Bandbass correction of
spectrometer
1.0E-5 B normal 0.0860224 0.001 50
Straylight correction of
spectrometer
1.0E-5 B normal 0.0860224 0.001 50
Correction for LED
translational align
9.7E-5 B normal 0.0860224 9.7E-3 10
Photometric sensitivity of
photometer
8.9E-11
A/lx
B normal -3.1044E6 -0.32 10
Distance setting 0.00020 m B rectangular 1.72045 0.40 10
Correction for LED angular
align
1.4E-4 B normal 0.0860224 1.3E-2 10
Spectral mismatch
correction factor
0.0032 B normal 0.0863853 0.32 50
Combined standard unce
rtainty (%)
-- -- normal -- 0.62 38 --
Table 4-32. PTB uncertainty budget of junction voltage measurement of blue LED (example).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(mV)
Deg. of
freedo
m
Correl
ated?
Calibration of voltmeter 0.000050 B rectangular 3.44 0.17 10
Junction position
dependence
0.00052 V B rectangular -1 -0.52 10
APMP.PR-S3a Averaged LED Intensity Final Report
38
Reproducibility 0.00058 V A normal 1 0.58 10
Combined standard unce
rtainty (mV)
-- -- normal -- 0.80 35 --
4.5. NMIJ
4.5.1. Measurement setup
The measurement of averaged LED intensity at NMIJ is based on the detector-method.
Photometer for Averaged LED Intensity (LED-photometer) composed of silicon photo-
diode, V(λ) correction filter, and circular aperture having an area of 100 mm2. "f1' value" of
the LED-photometer is 2.4.
Fig. 4-11. Calibration facility for LED luminous intensity and total luminous flux in NMIJ.
4.5.2. Mounting and alignment
a) The laser system and the telescope with CCD camera are used for LED alignment.
b) LED holder is mounted to the gonio-stage. (see Fig. 4-12)
c) Fig. 4-13 shows picture of the LED holder. (Pin socket is used to mount LED)
APMP.PR-S3a Averaged LED Intensity Final Report
39
Fig. 4-12. LED mount socket mounted to the gonio-stage in NMIJ.
Fig. 4-13. LED mount socket in NMIJ.
4.5.3. Traceability
a) Illuminance responsivity of the LED photometer ⇒ luminous intensity standard at
NMIJ.
b) Relative spectral responsivity of the LED photometer ⇒ spectral responsivity
standard at NMIJ.
c) Relative spectral distribution of the test LED ⇒ spectral irradiance standard at NMIJ.
4.5.4. Measurement uncertainty
Table 4-33. NMIJ uncertainty budget of averaged LED intensity measurement for red LEDs
(R).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
APMP.PR-S3a Averaged LED Intensity Final Report
40
Illuminance responsivity
(include near-field effect)
B gaussian 1 1.0 90000 O
Temperature dependence of
illuminance responsivity 1.2 °C B rectangular 0.09 %/°C 0.10 ∞ O
Linearity of illuminance
responsivity
B rectangular 1 0.07 ∞ O
Current feeding accuracy B rectangular 1 < 0.01 ∞ O
DMM accuracy B rectangular 1 < 0.01 ∞ O
Distance setting 0.21 mm B rectangular 2 %/mm 0.42 ∞ O
Mechanical axis alignment,
angular 0.29° B rectangular 0.48 %/° 0.14 ∞ X
Mechanical axis alignment,
translational (centering)
0.58 mm B rectangular 0.48 %/mm 0.16 ∞ X
Repeatability of LED
lighting (including noise
and drift)
A t 1 0.11 6 X
Stray light B rectangular 1 0.10 ∞ O
Spectral mismatch correction factor
Spectral responsivity
calibration (including
repeatability)
A
+
B
gaussian 1 0.11 ∞ X
Spectral irradiance
calibration (including
repeatability)
A
+
B
gaussian 1 < 0.01 ∞ X
Wavelength uncertainty of
relative spectral
responsivity
Random
0.1 nm,
systematic
0.1 nm
A
+
B
gaussian
(random f
actor),
rectangular
(systematic
factor)
-- 0.19 ∞ X
Wavelength uncertainty of
LED spectral distribution
Random
0.1 nm,
systematic
0.1 nm
A
+
B
gaussian
(random f
actor),
rectangular
(systematic
factor)
-- 0.02 ∞ X
Effect of slit function width B rectangular 1 0.12 ∞ X
Alignment of LED B rectangular 1 0.02 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 1.1 >>
25000
--
Table 4-34. NMIJ uncertainty budget of averaged LED intensity measurement for green LEDs
(G).
APMP.PR-S3a Averaged LED Intensity Final Report
41
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Illuminance responsivity
(include near-field effect)
B gaussian 1 1.0 90000 O
Temperature dependence of
illuminance responsivity 1.2 °C B rectangular 0.13 %/°C 0.14 ∞ O
Linearity of illuminance
responsivity
B rectangular 1 0.07 ∞ O
Current feeding accuracy B rectangular 1 < 0.01 ∞ O
DMM accuracy B rectangular 1 < 0.01 ∞ O
Distance setting 0.21 mm B rectangular 2 %/mm 0.42 ∞ O
Mechanical axis alignment,
angular 0.29° B rectangular 1.40 %/° 0.40 ∞ X
Mechanical axis alignment,
translational (centering)
0.58 mm B rectangular 1.40 %/mm 0.46 ∞ X
Repeatability of LED
lighting (including noise
and drift)
A t 1 0.05 6 X
Stray light B rectangular 1 0.1 ∞ O
Spectral mismatch correction factor
Spectral responsivity
calibration (including
repeatability)
A
+
B
gaussian 1 0.10 ∞ X
Spectral irradiance
calibration (including
repeatability)
A
+
B
gaussian 1 < 0.01 ∞ X
Wavelength uncertainty of
relative spectral
responsivity
Random
0.1 nm,
systematic
0.1 nm
A
+
B
gaussian
(random f
actor),
rectangular
(systematic
factor)
-- 0.18 ∞ X
Wavelength uncertainty of
LED spectral distribution
Random
0.1 nm,
systematic
0.1 nm
A
+
B
gaussian
(random f
actor),
rectangular
(systematic
factor)
-- 0.02 ∞ X
Effect of slit function width B rectangular 1 0.02 ∞ X
Alignment of LED B rectangular 1 < 0.01 ∞ X
Combined standard unce
rtainty (%) -- -- normal -- 1.2 >>
25000
--
APMP.PR-S3a Averaged LED Intensity Final Report
42
Table 4-35. NMIJ uncertainty budget of averaged LED intensity measurement for blue LEDs
(B).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Illuminance responsivity
(include near-field effect)
B gaussian 1 1.0 90000 O
Temperature dependence of
illuminance responsivity 1.2 °C B rectangular 0.38 %/°C 0.42 ∞ O
Linearity of illuminance
responsivity
B rectangular 1 0.07 ∞ O
Current feeding accuracy B rectangular 1 < 0.01 ∞ O
DMM accuracy B rectangular 1 < 0.01 ∞ O
Distance setting 0.21 mm B rectangular 2 %/mm 0.42 ∞ O
Mechanical axis alignment,
angular 0.29° B rectangular 2.74 %/° 0.69 ∞ X
Mechanical axis alignment,
translational (centering)
0.58 mm B rectangular 2.74 %/mm 0.78 ∞ X
Repeatability of LED
lighting (including noise
and drift)
A t 1 0.05 6 X
Stray light B rectangular 1 0.1 ∞ O
Spectral mismatch correction factor
Spectral responsivity
calibration (including
repeatability)
A
+
B
gaussian 1 0.19 ∞ X
Spectral irradiance
calibration (including
repeatability)
A
+
B
gaussian 1 0.01 ∞ X
Wavelength uncertainty of
relative spectral
responsivity
Random
0.1 nm,
systematic
0.1 nm
A
+
B
gaussian
(random f
actor),
rectangular
(systematic
factor)
-- 0.35 ∞ X
Wavelength uncertainty of
LED spectral distribution
Random
0.1 nm,
systematic
0.1 nm
A
+
B
gaussian
(random f
actor),
rectangular
(systematic
factor)
-- < 0.01 ∞ X
Effect of slit function width B rectangular 1 0.12 ∞ X
Alignment of LED B rectangular 1 0.02 ∞ X
APMP.PR-S3a Averaged LED Intensity Final Report
43
Combined standard unce
rtainty (%)
-- -- normal -- 1.6 >>
25000
--
Table 4-36. NMIJ uncertainty budget of averaged LED intensity measurement for white LEDs
(W).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Illuminance responsivity
(include near-field effect)
B gaussian 1 1.0 90000 O
Temperature dependence of
illuminance responsivity 1.2 °C B rectangular 0.10 %/°C 0.11 ∞ O
Linearity of illuminance
responsivity
B rectangular 1 0.07 ∞ O
Current feeding accuracy B rectangular 1 < 0.01 ∞ O
DMM accuracy B rectangular 1 < 0.01 ∞ O
Distance setting 0.21 mm B rectangular 2 %/mm 0.42 ∞ O
Mechanical axis alignment,
angular 0.29° B rectangular 0.42 %/° 0.12 ∞ X
Mechanical axis alignment,
translational (centering)
0.58 mm B rectangular 0.42 %/mm 0.14 ∞ X
Repeatability of LED
lighting (including noise
and drift)
A t 1 0.13 6 X
Stray light B rectangular 1 0.1 ∞ O
Spectral mismatch correction factor
Spectral responsivity
calibration (including
repeatability)
A
+
B
gaussian 1 0.03 ∞ X
Spectral irradiance
calibration (including
repeatability)
A
+
B
gaussian 1 < 0.01 ∞ X
Wavelength uncertainty of
relative spectral
responsivity
Random
0.1 nm,
systematic
0.1 nm
A
+
B
gaussian
(random f
actor),
rectangular
(systematic
factor)
-- 0.04 ∞ X
Wavelength uncertainty of
LED spectral distribution
Random
0.1 nm,
systematic
0.1 nm
A
+
B
gaussian
(random f
actor),
rectangular
(systematic
factor)
-- < 0.01 ∞ X
Effect of slit function width B rectangular 1 0.03 ∞ X
APMP.PR-S3a Averaged LED Intensity Final Report
44
Alignment of LED B rectangular 1 0.01 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 1.1 >> 250
00
--
Table 4-37. NMIJ uncertainty budget of averaged LED intensity measurement for diffuser-type
green LEDs (D).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Illuminance responsivity
(include near-field effect)
B gaussian 1 1.0 90000 O
Temperature dependence of
illuminance responsivity 1.2 °C B rectangular 0.13 %/°C 0.14 ∞ O
Linearity of illuminance
responsivity
B rectangular 1 0.07 ∞ O
Current feeding accuracy B rectangular 1 < 0.01 ∞ O
DMM accuracy B rectangular 1 < 0.01 ∞ O
Distance setting 0.21 mm B rectangular 2 %/mm 0.42 ∞ O
Mechanical axis alignment,
angular 0.29° B rectangular 0.25 %/° 0.08 ∞ X
Mechanical axis alignment,
translational (centering)
0.58 mm B rectangular 0.25 %/mm 0.09 ∞ X
Repeatability of LED
lighting (including noise
and drift)
A t 1 0.02 6 X
Stray light B rectangular 1 0.1 ∞ O
Spectral mismatch correction factor
Spectral responsivity
calibration (including
repeatability)
A
+
B
gaussian 1 0.10 ∞ X
Spectral irradiance
calibration (including
repeatability)
A
+
B
gaussian 1 < 0.01 ∞ X
Wavelength uncertainty of
relative spectral
responsivity
Random
0.1 nm,
systematic
0.1 nm
A
+
B
gaussian
(random f
actor),
rectangular
(systematic
factor)
-- 0.17 ∞ X
Wavelength uncertainty of
LED spectral distribution
Random
0.1 nm,
systematic
0.1 nm
A
+
B
gaussian
(random f
actor),
rectangular
(systematic
factor)
-- 0.02 ∞ X
APMP.PR-S3a Averaged LED Intensity Final Report
45
Effect of slit function width B rectangular 1 0.02 ∞ X
Alignment of LED B rectangular 1 < 0.01 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 1.1 >>
25000
--
Table 4-38. NMIJ uncertainty budget of junction voltage measurement.
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(V)
Deg. of
freedo
m
Correl
ated?
Calibration of DMM B gaussian 1 0.0001 ∞ O
Repeatability (including
effect of temperature
difference)
A gaussian 1 0.0006
~
0.0086
4 X
Junction position B rectangular 1 0.0003 ∞ X
Combined standard unce
rtainty (V)
-- -- normal -- 0.0007
~
0.0086
7 --
4.6. CENAM
4.6.1. Measurement setup
As established in the comparison Protocol6, the Averaged LED Intensity measurements
were performed by using the measurement array setup in order to reproduce the CIE
Standard Condition B7, see Fig. 4-14.
Fig. 4-14. CIE Standard Condition B established for Averaged LED Intensity in CENAM.
Since the key condition to be kept in order to reproduce the CIE Standard
6 D. H. Lee, Technical Protocol on APMP Supplementary Comparison of LED Measurements, KRISS, Korea, (2008). 7 Commission International de l’Eclairage, Measurement of LEDs, Publication CIE Nº 127, Genève, (2007).
Circular aperure size A= 100 mm2
Distance d
dB=100 mm, (= 0,01 sr)
dA=316 mm, (= 0,001 sr)
APMP.PR-S3a Averaged LED Intensity Final Report
46
Condition B is the established solid angle of =0.01 sr; then for a given aperture size A,
the corresponding distance d can be deduced from Eq. (4.1):
. (4.1)
Table 4-39 shows the aperture area and distance used at CENAM in order to reproduce
the sought solid angle.
Table 4-39. Parameters used at CENAM to reproduce the CIE Standard Condition B.
Aperture diameter, (mm) Aperture area, A (mm2) Distance, d (mm)
10.058 79.454 89
The selected aperture was coupled to a photometric detector, taking care of
maintaining the corresponding distance, see Fig. 4-15.
Fig. 4-15. Coupling between the aperture and photometric detector in CENAM.
4.6.2. Mounting and alignment
As stated in the Comparison Protocol, the Averaged LED Intensity measurements
required to consider the LED geometrical axis to lie along the measurement optical axis,
see Fig. 4-16.
Fig. 4-16. Averaged LED Intensity geometry.
APMP.PR-S3a Averaged LED Intensity Final Report
47
This alignment between axes required to assemble an LED mounting device
having at least six degrees of freedom for the position adjustment: translational, height,
transverse, centering angle, translational tilt angle, and transverse tilt angle. This special
mounting device consisted of an LED holder, a high load jack, an X-Y translational stage,
a rotation platform, and a pair of perpendicularly coupled goniometers, see Fig. 4-17.
Fig. 4-17. LED mounting device in CENAM.
Thus in order to define the measurement system optical axis, the height of the
LED holder was used as high reference, and propagated along the optical bench with the
use of an alignment laser beam, and fixed by using an alignment jig, see Fig. 4-18.
Fig. 4-18. Measurement system optical axis definition in CENAM.
Since the length of the several LEDs terminals was different for each device, it was
necessary to define a reference plane in order to accurately reproduce the distance d
given in Table 4-39 between the LED tip and the aperture plane; this was achieved by
LED hoder
APMP.PR-S3a Averaged LED Intensity Final Report
48
locating a flat plate aside of the LED holder, see Fig. 4-19.
Fig. 4-19. Reference plane for distance stated in CIE Standard Condition B in CENAM.
With the measurement array aligned, the LEDs were placed in the holder, see Fig.
4-20, and aligned by using the reference plane defined by the flat plate and the
alignment jig; as to obtain the view of the LED as established in the Comparison Protocol,
see Fig. 4-21.
Fig. 4-20. LED insertion in the holder in CENAM.
Fig. 4-21. Lamp-type and diffuser-type LEDs alignment views in CENAM.
APMP.PR-S3a Averaged LED Intensity Final Report
49
4.6.3. Traceability
The Averaged LED Intensity was measured by using a photometric detector calibrated for
photometric responsivity against the luminous intensity standard maintained at CENAM,
which is traceable to the radiant flux SI unit trough the Mexican primary standard. Fig.
4-22. shows the corresponding traceability chart for the luminous intensity
measurements carried out at CENAM, where the expanded uncertainty presented
correspond to a coverage factor of k = 2.
Fig. 4-22. Traceability chart for the luminous intensity measurements performed at CENAM.
4.6.4. Measurement uncertainty
The Averaged LED Intensity, IV, was obtained from Eq. (4.2):
, (4.2)
where ip is the photocurrent produced by the photometric detector; d is the distance
from the LED tip to the aperture plane; sV is the photometric responsivity of the detector
and F is the spectral mismatch correction factor, given by Eq. (4.3):
, (4.3)
Resistance []
Shunt Resistor
Res-61173
0,0999965
U ≤ 1,7µΩ/Ω
[V]
Multimeters
M-3457-883
M-3457-885
U = 15µV
/Ω
r
M-3457-881
U = 13 µA/A
ncia Shunt Res-
61174
U ≤ 1,7 µΩ/Ω
CNM-PNE-3
Electric
Resistance
ohm
[]
Voltage [V]
Multimeter
M-3457-883
M-3458-334
U ≤ 13 µV/V
CNM-PNE-5
Electric DC
Voltage
volt
[V]
CNM-PNM-2
Length
meter
[m]
Length [m]
Ruler
R-FOT-1
U = ± 6 µm
Area
[m2]
Aperture
U = ± 0.002 mm
CNM-PNE-13
Electric DC
current
ampere
[A]
CNM-PNF-12
Radiant Flux
watt
[W]
Responsivity
[A/W]
Photometric Detector
DF-SF-2
427 nm -723 nm
U = ± 4.15% - 0.74%
Photometric
Responsivity
[A/lx]
Photometric Detector
DF-SF-2
U ≈ ± 1.00%
Averaged LED
Intensity
0,1 cd - 1 000cd
LED’S
U = 6%
CNM-PNF-4
Luminous
Intensity
candela
[cd]
SI units
External
Laboratory
Service
APMP.PR-S3a Averaged LED Intensity Final Report
50
where sph (λ) is the spectral responsivity of the used photometric detector and SA(λ) and
SLED(λ) are the spectral power distributions of the CIE Illuminant A and measured LED,
respectively.
From Eqs. (4.2) and (4.3), it is possible to identify the uncertainty components:
which are graphically shown in Fig. 4-23.
Fig. 4-23. Averaged LED Intensity uncertainty components in CENAM.
Table 4-40. CENAM uncertainty budget of averaged LED intensity measurement for red LEDs
(R).
Averaged
LED
Intensity
Multimeter resolution
Readings repeatibility
Multimeter error
i led
Ruler resolution
n d
Sv Photometric responsivity value
Axis misalign
ment
angular
translational
Stray light
Current fee
ding accura
cy
V Resistance
R
Multimeter resolution
Multimeter repeatibility
Multimeter error
Resistance value
Voltage jun
ction due
to position
position vled FLT
V LED
Multimeter resolution
Multimeter repeatibility
Multimeter error
F
s rel
S led
Photometric detector relative spectral responsivity
Spectroradiometer error
Spectroradiometer repeatibility
APMP.PR-S3a Averaged LED Intensity Final Report
51
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedom Correl
ated?
Readings repeatability 0.07 A normal 1 0.07 14 O
Distance setting 0.65 B rectangular 1 0.65 200 O
Photometric responsivity
value
0.33 B normal 1 0.33 200 X
Spectral mismatch
correction
2.69 B normal 1 2.69 200 X
Current feeding accuracy 0.05 A normal 1 0.05 14 X
Junction voltage 0.004 A normal 1 0.004 14 X
Axis alignment 0.13 A normal 1 0.13 4 O
Stray light 0.01 B rectangular 1 0.01 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 2.79 231 --
Table 4-41. CENAM uncertainty budget of averaged LED intensity measurement for green
LEDs (G).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedom Correl
ated?
Readings repeatability 0.02 A normal 1 0.02 14 O
Distance setting 0.65 B rectangular 1 0.65 200 O
Photometric responsivity
value
0.33 B normal 1 0.33 200 X
Spectral mismatch
correction
2.97 B normal 1 2.97 200 X
Current feeding accuracy 0.19 A normal 1 0.19 14 X
Junction voltage 0.02 A normal 1 0.02 14 X
Axis alignment 0.63 A normal 1 0.63 4 O
Stray light 0.01 B rectangular 1 0.01 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 3.13 223 --
Table 4-42. CENAM uncertainty budget of averaged LED intensity measurement for blue
LEDs (B).
APMP.PR-S3a Averaged LED Intensity Final Report
52
Uncertainty Component Standard u
ncertainty
(%) Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedom Correl
ated?
Readings repeatability 0.05 A normal 1 0.05 14 O
Distance setting 0.65 B rectangular 1 0.65 200 O
Photometric responsivity
value
0.33 B normal 1 0.33 200 X
Spectral mismatch
correction
2.70 B normal 1 2.70 200 X
Current feeding accuracy 0.13 A normal 1 0.13 14 X
Junction voltage 0.004 A normal 1 0.004 14 X
Axis alignment 0.23 A normal 1 0.23 4 O
Stray light 0.01 B rectangular 1 0.01 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 2.81 233 --
Table 4-43. CENAM uncertainty budget of averaged LED intensity measurement for white
LEDs (W).
Uncertainty Component Standard u
ncertainty
(%) Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedom Correl
ated?
Readings repeatability 0.08 A normal 1 0.08 14 O
Distance setting 0.65 B rectangular 1 0.65 200 O
Photometric responsivity
value
0.33 B normal 1 0.33 200 X
Spectral mismatch
correction
2.74 B normal 1 2.74 200 X
Current feeding accuracy 0.03 A normal 1 0.03 14 X
Junction voltage 0.003 A normal 1 0.003 14 X
Axis alignment 0.15 A normal 1 0.15 4 O
Stray light 0.01 B rectangular 1 0.01 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 2.84 230 --
Table 4-44. CENAM Uncertainty budget of averaged LED intensity measurement for diffuser-
type green LEDs (D).
APMP.PR-S3a Averaged LED Intensity Final Report
53
Uncertainty Component Standard u
ncertainty
(%) Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedom Correl
ated?
Readings repeatability 0.89 A normal 1 0.89 14 O
Distance setting 0.65 B rectangular 1 0.65 200 O
Photometric responsivity
value
0.33 B normal 1 0.33 200 X
Spectral mismatch
correction
3.11 B normal 1 3.11 200 X
Current feeding accuracy 0.01 A normal 1 0.01 14 X
Junction voltage 0.0003 A normal 1 0.0003 14 X
Axis alignment 0.02 A normal 1 0.02 4 O
Stray light 0.01 B rectangular 1 0.01 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 3.31 235 --
Table 4-45. CENAM uncertainty budget of junction voltage measurement.
Uncertainty Component Standard u
ncertainty
(%) Ty
pe
Probability
distribution
Sensitivity
coefficient
Contri
bution
(%)
Deg. of
freedo
m
Correl
ated?
Readings repeatability 0.002 A normal 1 0.002 14 O
Multimeter resolution 0.0001 B rectangular 1 0.0001 200 X
Multimeter error 0.0005 B normal 1 0.0005 200 X
Combined standard unce
rtainty (%)
-- -- normal -- 0.002 16 --
4.7. LNE
4.7.1. Measurement setup
LNE has developed a measurement set-up to measure photometric and colorimetric
characteristics of LEDs. This set-up is based on a goniophotometer designed to meet the
requirements of the CIE127 standards for averaged intensity and total flux measurements.
It is optimized for high power white LEDs measurements and was adapted for the LEDs
in the framework of the APMP-S3 supplementary comparison. The schematic of the
goniophotometer is shown on Fig. 4-24. It is 2 m long and 1.8 m high.
APMP.PR-S3a Averaged LED Intensity Final Report
54
Fig. 4-24. Goniophotometer for LEDs flux measurements in LNE.
The set-up is made of the following parts:
- Optical rails to set the main frame
- A multi-axis LED mount which allow the accurate alignment of the LED along the
horizontal optical axis and with respect to the photometric center of the
goniophotometer. This device is mounted onto a horizontal axis motorised
rotation stage that rotates the LED around the optical axis. A detailed schematic
of the LED mount is shown on figure 2.
- A vertical axis motorised rotation stage on which the multi-axis LED mount is
placed.
A camera placed above the LED allows us to adjust the position of the LED with
respect to the photometric center. The photometer is mounted on an optical rail. The
Photometer
Spectrocolorimeter
LED mount
Stepping
motor driver
Camera
APMP.PR-S3a Averaged LED Intensity Final Report
55
distance between the photometer and the LED can be adjusted to meet the
requirements of the measurement conditions. During the measurements the photometer
is kept steady. Laser beam is used to define the optical axis of the goniophotometer.
Fig. 4-25. LED mount in LNE.
Fig. 4-26. LED holder in LNE.
Intensity measurement is performed with a photometer, manufacturer LMT, type
P11S00, including a 11,3 mm diameter (1 cm²) sensitive area, with a very fine V()
correction (f’1 1%). The distance between the LED tip and the photometer is 100 mm
(CIE 127, condition B). The instruments used to perform the measurements are listed in Table
4-46.
Table 4-46. Instruments used on the LED photometric bench in LNE.
Instrument Manufacturer Type Function
APMP.PR-S3a Averaged LED Intensity Final Report
56
V() photometer LMT P11S00 Illuminance
measurement
Picoammeter Keithley 486 Photometer current
measurement
LED power supply Agilent 3436A Stabilised LED power
supply
Shunt resistor AOIP 1000 / 228RE6 LED current
measurement
Multimeter Hewlett-Packard 3457A LED junction voltage
measurement
4.7.2. Mounting and alignment
Alignment of the LED on the LED holder is performed using a luminance meter,
manufacturer LMT, type L1009 with reflex viewing. Then the LED is placed in front of the
photometer as shown on Fig. 4-28.
Fig. 4-27. Luminancemeter used to align the LED in LNE.
Fig. 4-28. Alignment of the LED in front of the photometer in LNE.
APMP.PR-S3a Averaged LED Intensity Final Report
57
4.7.3. Traceability
Photometer
The photometer is calibrated in illuminance at LNE using a set of three standard lamps
calibrated in luminous intensity at LNE-INM. The standards lamps are calibrated using
primary realisation of the candela through filter radiometer.
Electrical Instruments
All electrical instruments with critical impact on the measurements are calibrated by the
LNE electrical department which is COFRAC (Comité Français d’Accréditation) accredited.
COFRAC is the French accreditation body.
Length
The distance between the LED and the photometer is measured using a meter calibrated
by the LNE length department which is COFRAC accredited.
4.7.4. Measurement uncertainty
Intensity measurement
Reading repeatability
This uncertainty is estimated from the standard deviation of 5 measurements performed
in the same operating conditions. The uncertainties associated to each colour are the
following:
- Red: 0.20 %
- Green: 0.30 %
- Blue: 0.50 %
- White: 0.30 %
- Diffuser: 0.09 %
Component due to axis alignment
Uncertainty evaluation is performed for horizontal, vertical and angular alignment. For
horizontal and vertical alignment contributions, the LED is moved 1 mm apart from the
photometric axis and the changes in the photometer signal is noted. For the angular
alignment contribution, the result of the goniophotometric measurements are used to
determine change in photometer reading corresponding to an angular deviation of 1°
from the optical axis. The uncertainty contributions are summarized in the following table
APMP.PR-S3a Averaged LED Intensity Final Report
58
for each colour taking into account a 0.5 mm alignment accuracy for the horizontal and
vertical axis and a 0.5° alignment accuracy for the angular positioning.
LED type Horizontal alignment
(%)
Vertical alignment
(%)
Angular alignment
(%)
Red 0.020 0.035 0.25
Green 0.12 0.12 0.5
Blue 0.13 0.15 0.7
White 0.014 0.036 0.1
Diffuser 0.0050 0.032 0
Component due to distance between the LED and the photometer
The distance between the LED and the reference plane of the photometer is known with
an uncertainty of 100 µm. The associated contribution to the intensity measurement is
evaluated by measuring the changes in the photometer signal when the distance is
changed by 5 mm. The result is shown in the following table for the different LED colors.
LED type Relative uncertainty due to distance
LED-photometer
(%)
Red 0.18
Green 0.18
Blue 0.18
White 0.18
Diffuser 0.20
Component due to current feeding accuracy.
The current is measured through a 1000 resistor using a voltmeter. The resistor is
calibrated with an uncertainty of 1. 10-5. The voltmeter is calibrated with an uncertainty
of 1. 10-5. Therefore the current is measured with an uncertainty of 1.4 10-5. The current
is adjusted with an offset of 0.001 mA which corresponds to a relative error of 5. 10-5 .
The intensity is not corrected for this offset which is included in the uncertainty of the
current. The overall uncertainty on the current feeding is obtained from the uncertainty
due to the current measurement and the current offset, that is 5.2 10-5. The
corresponding uncertainty of the LED intensity measurement is determined from the
manufacturer’s data sheets. The results are summarized in the following table:
LED type Relative uncertainty due to
current feeding
(%)
Red 0.0052
APMP.PR-S3a Averaged LED Intensity Final Report
59
Green 0.0042
Blue 0.0031
White 0.0042
Diffuser 0.0042
Component due to stray light in the optical bench
A black tube with apertures is placed between the photometer and the LED. The aperture
in front of the LED is 10 mm in diameter. The LED is placed 20 mm away from the holder
which is black painted, partly shiny, to reduce contribution of backward emission. With
this arrangement stray light is limited and is estimated to be < 0.01 %.
Component due to ambient temperature
The measurements are performed at 23 °C 1 °C. The measurement uncertainty due to
the uncertainty on the ambient temperature is determined from the manufacturer’s data
sheets. The results are summarized in the following table:
LED type Uncertainty due to ambient temperature
(%)
Red 0.5
Green 0.25
Blue 0.25
White 0.2
Diffuser 0.25
Component due to the calibration of the photometer
The photometer is calibrated with a relative uncertainty of 0.6%.
Component due to linearity of the photometer
For intensity measurement the illuminance measured is of the same order of magnitude
than the illuminance measured during the photometer calibration. Therefore the
uncertainty due do linearity of the photometer is < 0.02%.
Component due to spectral mismatch correction
The photometer is calibrated in relative spectral response. The LED flux measurement
results are corrected for the spectral mismatch of the photometer. The uncertainty on the
relative spectral response of the photometer is used to determine the uncertainty on the
spectral mismatch correction. This uncertainty is calculated by taking the average of the
uncertainty of the relative spectral response weighted by the spectral distribution of the
APMP.PR-S3a Averaged LED Intensity Final Report
60
LED. Works using Monte Carlo techniques are underway to take into account correlation
in determining uncertainty on spectral mismatch correction. The actual uncertainties are
the following:
- Red: 0.5 %
- Green: 0.4 %
- Blue: 1 %
- White: 0.2 %
Table 4-47. LNE uncertainty budget of averaged LED intensity measurement for red LEDs (R).
Uncertainty
Component
Standard
uncertainty Ty
pe Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedom
Correlated?
Reading
repeatability
0.2 A t 1 0.2 4 X
Axis
alignment,
angular
0.25 B rectangular 1 0.25 ∞ X
Axis
alignment,
translational
0.04 B rectangular 1 0.04 ∞ X
Distance
setting
0.09 B rectangular 2 0.18 ∞ O
Current
feeding
accuracy
0.0052 B rectangular 1 0.0052 ∞ X
Stray light 0.01 B rectangular 1 0.01 ∞ O
Ambiant
temperature
0.5 B rectangular 1 0.5 ∞ X
Calibration
of
photometer
0.6 B normal 1 0.6 ∞ O
Non-
linearity
0.02 B rectangular 1 0.02 ∞ O
Spectral
mismatch
correction
0.5 B normal 1 0.5 ∞ X
Combined
standard
uncertainty
(%)
-- -- normal -- 1.0 ∞ --
Table 4-48. LNE uncertainty budget of averaged LED intensity measurement for green LEDs
(G).
Uncertainty
Component
Standard
uncertainty Ty
pe Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedom
Correlated?
APMP.PR-S3a Averaged LED Intensity Final Report
61
Reading
repeatability
0.3 A t 1 0.3 4 X
Axis
alignment,
angular
0.5 B rectangular 1 0.5 ∞ X
Axis
alignment,
translational
0.17 B rectangular 1 0.17 ∞ X
Distance
setting
0.09 B rectangular 2 0.18 ∞ O
Current
feeding
accuracy
0.0052 B rectangular 0.8 0.00416 ∞ X
Stray light 0.01 B rectangular 1 0.01 ∞ O
Ambiant
temperature
0.25 B rectangular 1 0.25 ∞ X
Calibration
of
photometer
0.6 B normal 1 0.6 ∞ O
Non-
linearity
0.02 B rectangular 1 0.02 ∞ O
Spectral
mismatch
correction
0.4 B normal 1 0.4 ∞ X
Combined
standard
uncertainty
(%)
-- -- normal -- 1.0 ∞ --
Table 4-49. LNE uncertainty budget of averaged LED intensity measurement for blue LEDs
(B).
Uncertainty
Component
Standard
uncertainty Ty
pe Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedom
Correlated?
Reading
repeatability
0.5 A t 1 0.5 4 X
Axis
alignment,
angular
0.7 B rectangular 1 0.7 ∞ X
Axis
alignment,
translational
0.2 B rectangular 1 0.2 ∞ X
Distance
setting
0.09 B rectangular 2 0.18 ∞ X
Current
feeding
accuracy
0.0052 B rectangular 0.6 0.00312 ∞ O
Stray light 0.01 B rectangular 1 0.01 ∞ O
Ambiant
temperature
0.25 B rectangular 1 0.25 ∞ X
APMP.PR-S3a Averaged LED Intensity Final Report
62
Calibration
of
photometer
0.6 B normal 1 0.6 ∞ O
Non-
linearity
0.02 B rectangular 1 0.02 ∞ O
Spectral
mismatch
correction
1 B normal 1 1 ∞ X
Combined
standard
uncertainty
(%)
-- -- normal -- 1.5 ∞ --
Table 4-50. LNE uncertainty budget of averaged LED intensity measurement for white LEDs
(W).
Uncertainty
Component
Standard
uncertainty Ty
pe Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedom
Correlated?
Reading
repeatability
0.3 A t 1 0.3 4 X
Axis
alignment,
angular
0.1 B rectangular 1 0.1 ∞ X
Axis
alignment,
translational
0.04 B rectangular 1 0.04 ∞ X
Distance
setting
0.09 B rectangular 2 0.18 ∞ X
Current
feeding
accuracy
0.0052 B rectangular 0.8 0.00416 ∞ O
Stray light 0.01 B rectangular 1 0.01 ∞ O
Ambiant
temperature
0.2 B rectangular 1 0.2 ∞ X
Calibration
of
photometer
0.6 B normal 1 0.6 ∞ O
Non-
linearity
0.02 B rectangular 1 0.02 ∞ O
Spectral
mismatch
correction
0.2 B normal 1 0.2 ∞ X
Combined
standard
uncertainty
(%)
-- -- normal -- 0.76 ∞ --
Table 4-51. LNE uncertainty budget of averaged LED intensity measurement for diffuser-type
green LEDs (D).
APMP.PR-S3a Averaged LED Intensity Final Report
63
Uncertainty
Component
Standard
uncertainty Ty
pe Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedom
Correlated?
Reading
repeatability
0.09 A t 1 0.09 4 X
Axis
alignment,
angular
0 B rectangular 1 0 ∞ X
Axis
alignment,
translational
0.03 B rectangular 1 0.03 ∞ X
Distance
setting
0.1 B rectangular 2 0.2 ∞ X
Current
feeding
accuracy
0.0052 B rectangular 0.8 0.00416 ∞ O
Stray light 0.01 B rectangular 1 0.01 ∞ O
Ambiant
temperature
0.25 B rectangular 1 0.25 ∞ X
Calibration
of
photometer
0.6 B normal 1 0.6 ∞ O
Non-
linearity
0.02 B rectangular 1 0.02 ∞ O
Spectral
mismatch
correction
0.4 B normal 1 0.4 ∞ X
Combined
standard
uncertainty
(%)
-- -- normal -- 0.79 ∞ --
Junction Voltage
Repeatability
This uncertainty is estimated from the standard deviation of 20 measurements performed
in the same operating conditions. For all type of LED the uncertainty is 0.02%.
Component due to the calibration of the voltmeter
The voltmeter used for the junction voltage measurement is calibrated with an
uncertainty of 0.001 %.
Component due to position of junction voltage measurement point.
The leads of the LED are made of iron for the red LED and of copper for the green,
blue and white LED. The 4-wires device used to measure the junction voltage is located
20 mm away from the LED chip. Taking into account the geometry of the leads (40 mm
long and 0.25 mm² area) and the conductivity of the material used for the leads we
determine the voltage drop due to the leads. The results are summarized in the following
APMP.PR-S3a Averaged LED Intensity Final Report
64
table.
LED type Relative voltage drop @ 20 mA
(%)
Red 0.008
Green 0.0008
Blue 0.0008
White 0.0008
Diffuser 0.0008
Table 4-52. LNE uncertainty budget of junction voltage measurement of red LEDs.
Uncertainty
Component
Standard
uncertainty Ty
pe Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedom
Correlated?
Repeatability 0.01 A normal 1 0.01 19 X
Calibration
of voltmeter
0.001 B normal 1 0.001 ∞ O
Junction
position
dependence*
0.008 B rectangular 1 0.008 ∞ X
Combined
standard
uncertainty
(%)
-- -- normal -- 0.013 ∞ --
Table 4-53. LNE uncertainty budget of junction voltage measurement of green, blue, white and
diffuser-type LEDs.
Uncertainty
Component
Standard
uncertainty Ty
pe Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedom
Correlated?
Repeatability 0.01 A normal 1 0.01 19 X
Calibration
of voltmeter
0.001 B normal 1 0.001 ∞ O
Junction
position
dependence*
0.0008 B rectangular 1 0.0008 ∞ X
Combined
standard
uncertainty
(%)
-- -- normal -- 0.010 ∞ --
4.8. METAS
4.8.1. Measurement setup
The measurements setup and the instruments used are illustrated in the Fig. 4-29 below.
The measurements were performed by a set of photometers of different manufactures
APMP.PR-S3a Averaged LED Intensity Final Report
65
and different V(λ) matches. The luminous responsivity is individually corrected for all
photometer – LED combinations by measuring the spectral responsivity of the
photometers and spectral distribution of the LEDs.
Fig. 4-29. Schematic setup for averaged LED intensity measurement in METAS.
4.8.2. Mounting and alignment
The LED is fixed inside a kinematic optical mount. The LED is connected through a “true”
4 wires connection. The voltage is measured at the end of the pin by gold plated
electrical connectors (yellow and green wire in the image below). The current is feed
through electrical clamps (brown and white wire).
The alignment is performed in several iterative steps in accordance with the
technical protocol of the comparison: The centering and directional adjustment is done
by a camera based system placed in front the LED on the optical axis of the photometer
bench. The distance is adjusted through visible observation through an alignment
telescope from the side. The required distance of 100 mm is assured through a
mechanical gauge block.
Photometer bench
Carrousel holding different photometers (Czibula, LMT, METAS) and the spectroradiometer
Picoammeter Vinculum
Keithley Multimeter 2010
Keithley Sourcemeter 2400, 4wires
LED holder on 4 axis-alignment holder
Visual alignment telescope
Camera based alignment telescope
APMP.PR-S3a Averaged LED Intensity Final Report
66
Fig. 4-30. LED mount and wire connection in METAS.
4.8.3. Traceability
All primary quantities (i.e. illuminance, length, current, voltage etc) and secondary
quantities (temperature, humidity, etc) are traceable to national standards realized at
METAS. The detailed view of the traceability of the primary quantities is shown in the
following diagram.
4.8.4. Measurement uncertainty
The uncertainty budgets are based on the recommendation of CIE TC2-43
“Determination of measurement uncertainty in photometry”, Draft 9, 2008, and thus
following the GUM.
Cryogenic radiometer METAS
Reference Radiometer METAS
Reference Photometer Illuminant A METAS
METAS Electricity Section
Averaged LED intensity
METAS Length Section
Filterradiometer METAS
Aperture
METAS Electricity Section
Distance
ULED, ILED, IPhoto
Spectral Irradiance Standard METAS
Spectrometer METAS
Colour correction factor
IRadio
IPhoto
APMP.PR-S3a Averaged LED Intensity Final Report
67
For simplicity only the uncertainty budget for a green LED is illustrated explicitly
in the following. The estimated input quantities of the other LED’s are listed in their
description.
Model for averaged LED intensity:
Description of terms:
CS1I output quantity: luminous intensity of the LED at certified conditions.
PSd = 0.100 m, distance between tip of the LED and photometer head, interval
±0.00020 m with rectangular power distribution (RPD), converted into standard
measurement uncertainty (MU) )( PSdu = (0.000200/ 3 = 0.000115) m; Type B
with degree of freedom (DOF) v , no correlation.
PS1y = 0.714242 V, DVM signal photometer, 10n independent readings, the
standard deviation of the mean (SDM) is taken as standard MU
PS1yu 0.000006 V and is significantly larger than the resolution; Type A with
DOF 9v , no correlation.
PS0y = 0.000048 V, DVM dark signal photometer, 10n independent readings, the
SDM is taken as standard MU PS0yu 0.000004 V and is significantly larger
than the resolution; Type A with DOF 9v , no correlation.
CR1s = 25.722 nA/lx, luminous responsivity of the photometer certified with relative
expanded 2k MU CR1rel sU = 0.008, converted into absolute standard MU
CR1su = (25.722*0.008/2 = 0.1029) nA/lx; Type B with DOF v , no
correlation.
Pc = 1.00000, calibration factor for the DVM certified with relative expanded 2k
MU Prel cU = 0.0001, converted into absolute standard MU
Pcu = 1.00000*0.0001/2 = 0.00005; Type B with DOF v , no correlation.
PS1G = 100.0020 K , gain setting resistance (of the picoammeter) certified with
relative expanded 2k MU PS1rel GU = 0.00002, converted into absolute
standard MU PS1Gu = (100.0020*0.00002/2 = 0.001) K; Type B with DOF
v , no correlation.
SMCf = 1.0067, spectral mis-match correction factor of the green LED. The factor and its
uncertainty depend on the spectral distribution of the LED source (and the spectral
responsivity of the photometer). The relative expanded 2k MU )( SMCfU =
)()(
)(
aS1S1PSS1
PPPSP
PS1
P
CR1
PS0PS1PSCS1
xSSS
m
SN
SSMC
dkhTdd
gdd
J
Jf
G
c
s
yydI
JS
111
2
21
21
APMP.PR-S3a Averaged LED Intensity Final Report
68
0.010, converted into standard MU )( SMCfu = (1.0067*0.010/2)= 0.005.
Typical values including standard uncertainties (k = 1) for the other LED colours
are: SMCf (blue) = (1.026 ± 0.015), SMCf (red) = (0.991 ± 0.005), and SMCf
(white) = (1.007± 0.003).
SJ = 20.000 mA, current of the current source with a relative expanded 2k MU
)( SJU = 2E-4, converted into absolute standard MU )( SJu =
(20.000*0.0002/2 = 0.002) mA; Type B with DOF v , no correlation.
SNJ = 20 mA, nominal current, no uncertainty.
JSm = 0.75, exponent relating relative luminous output intensity with electrical input
current (based on the datasheet of the green LED) with absolute standard
uncertainty 020)( .mu JS . The values (included their expanded MU) of the other
colours are: JSm (blue) = 0.72 ± 0.04, JSm (red) = 0.94 ± 0.04, and JSm (white)
= 0.80 ± 0.04, all Type B with DOF v , no correlation.
PSP dd = (0 ± 0.2) mm/100 mm, distance alignment of photometer head within
interval with RPD, converted into standard MU )( PSP ddu = 0.2/(100*
3 ) = 0.0012; Type B with DOF v , no correlation.
)( PPg = 0.0, angular misalignment of photometer head within interval max 1° with
RPD converted into standard MU 20/)180/1())(( 2 PPgu = 0.00007;
Type B with DOF v , no correlation.
PSS1 dd = (0 ± 0.2) mm/100 mm, distance alignment of LED tip within interval with
RPD, converted into standard MU PSP ddu = 0.2/(100* 3 ) = 0.0012; Type B
with DOF v , no correlation.
S1 = -0.0019 -1K , relative temperature coefficient of the green LED (based on the
datasheet ) with standard MU S1u = (0.0002/2 = 0.0001) -1K ; Type B with
DOF v , no correlation. For other LED’s the temperature coefficient is
estimated as: S1 (red) = (-0.0074 ± 0.0005) -1K , S1 (blue) = (0.00175 ±
0.00020) -1K , S1 (white) = (0.0016 ± 0.0005)
-1K ,
aS1T = 0.0 °C, above nominal ambient temperature near lamp, with standard MU
aS1Tu = (0.5/ 3 = 0.28) °C; Type B with DOF 1000v , no correlation.
)( 11 SSh = 0.0, angular misalignment of the LED within interval 1S 2° with RPD
converted into standard MU 202)(2
11 ghu SS = 0.0025;
Type B with DOF v , no correlation. )log(cos/)5.0log( 5.0g = 9.0, is
determined from the FMHW 50. (datasheet of the green LED). For the other
LED’s the values are g (red) = 6.9, g (blue) = 9.0, g (white) = 3.2, g (diffuse)
= 1.0. The uncertainty on g is neglected.
APMP.PR-S3a Averaged LED Intensity Final Report
69
)( xS dk 1 = 0.0, lateral misaligement of the LED within interval xd 0.5 mm with
RPD converted into standard MU 20)100/5.0arctan()(2
1 gdku xS =
0.00005, Type B with DOF v , no correlation, g is taken as above.
The following quantities were ignored
- The influence of the ambient temperature uncertainty on the photometer as a temperature
stabilized photometer was used.
- The influence of the ambient temperature, electrical current (of the LED supply) and the
mechanical alignment on the spectral mis-match correction factor.
- straylight effects (not estimated).
- ageing of the photometer as the detector was calibrated just before use.
- ageing of the DUT as no relevant information was available.
- The influence of the uncertainty of the surface area of the photometer, estimated to be
(100.00 ± 0.01) mm2.
Sensitivity coefficients:
PS
CS
PS
CS
d
I
d
Ic 11
1 2 55.9027 cd/m
1
1
1
12
PS
CS
PS
CS
y
I
y
Ic 3.914 cd/V
1
1
0
13
PS
CS
PS
CS
y
I
y
Ic - 3.914 cd/V
1
1
1
14
CR
CS
CR
CS
s
I
s
Ic -0.1087 cd/V
p
CS
p
CS
c
I
c
Ic 11
5 2.795 cd
PS1
1
PS1
16
G
I
G
Ic CSCS
-0.027951 cd/kΩ
SMC
CS
SMC
CS
f
I
f
Ic 11
7 2.777 cd
S
CSJS
S
CS
J
Im
J
Ic 11
8 0.1048 cd/mA
SN
SCS
JS
CS
J
JI
m
Ic log1
110
0.000 cd
1
PSP
111 2
)(CS
CS Idd
Ic 5.5903 cd
1
112
)(CS
pp
CS Ig
Ic
2.795 cd
1
PSS1
113 2
)(CS
CS Idd
Ic -5.5903 cd
11
S1
114 CSaS
CS ITI
c
0.000 cd K
1S1
1
115 CS
aS
CS IT
Ic 0.00531 cd K
-1
1
11
116
)(CS
SS
CS Ih
Ic
-2.795 cd
1
1
117
)(CS
xS
CS Idk
Ic -2.795 cd
Table 4-54. METAS uncertainty budget of averaged LED intensity measurement for red LEDs
(R).
APMP.PR-S3a Averaged LED Intensity Final Report
70
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contribut
ion (%)
Deg. of
freedo
m
Correl
ated?
Distance photometer
bench PSd
1.15E-4 m B rectangular 13.7847
cd/m
0.23 ∞ X
Mean value photometer
signal PS1y
6E-6 V A t 0.3853 cd/V <0.001 9 X
Mean value photometer
dark signal PS0y
4E-6 V A t -0.3853 cd/V <0.001 9 X
Responsivity photometer
CR1s
0.1029
nA/lx
B normal -0.02680
cd·lx/nA
-0.40 ∞ O
Calibration factor DVM
gain resistor Pc
5E-5 B normal 0.6892 cd 0.005 ∞ O
Gain resistor photometer
PS1G 0.001 kΩ B normal -6.8923E-04
cd/kΩ
<0.001 ∞ O
Spectral mismatch
correction factor SMCf
0.005 B normal 0.6955 cd 0.50 ∞ X
Measured current of LED
SJ 0.002 mA B normal 0.0324
cd/mA
0.009 ∞ X
Intensity to current
exponent JSm
0.02 B normal 0 0 ∞ X
Relative distance
variation, photomter
PSP dd
0.0012 B rectangular 1.3785 cd 0.24 ∞ X
Angular alignment
photometer )( PPg
7E-5 B rectangular 0.6892 cd 0.007 ∞ X
Relative distance
variatioin PSS1 dd
0.0012 B rectangular -1.3785 cd -0.24 ∞ X
Temperature coefficient
of LED S1
0.0001 K-1
B normal 0 0.007 ∞ X
Temperature above
nominal temp. aS1T
0.28 K B rectangular 0.0051 cd/K 0.21 ∞ X
Angular tilt )( 11 SSh 0.002 B rectangular -0.6892 cd -0.20 ∞ X
Lateral misalignment
)( xS dk 1
5R-5 B rectangular -0.6892 cd -0.005 ∞ X
Combined standard unc
ertainty (%)
-- -- normal -- 0.82 > 1000 --
Table 4-55. METAS uncertainty budget of averaged LED intensity measurement for green
LEDs (G).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contribut
ion (%)
Deg. of
freedo
m
Correl
ated?
APMP.PR-S3a Averaged LED Intensity Final Report
71
Distance photometer
bench PSd
1.15E-4 m B rectangular 55.9027
cd/m
0.23 ∞ X
Mean value photometer
signal PS1y
6E-6 V A t 3.9134 cd/V <0.001 9 X
Mean value photometer
dark signal PS0y
4E-6 V A t -3.9134 cd/V <0.001 9 X
Responsivity photometer
CR1s
0.1029
nA/lx
B normal -0.1087
cd·lx/nA
-0.40 ∞ O
Calibration factor DVM
gain resistor Pc
5E-5 B normal 2.7951 cd 0.005 ∞ O
Gain resistor photometer
PS1G 0.001 kΩ B normal -0.0280
cd/kΩ
-0.0010 ∞ O
Spectral mismatch
correction factor SMCf
0.005 B normal 2.7765 cd 0.50 ∞ X
Measured current of LED
SJ 0.002 mA B normal 0.1048
cd/mA
0.008 ∞ X
Intensity to current
exponent JSm
0.02 B normal 0 0 ∞ X
Relative distance
variation, photomter
PSP dd
0.0012 B rectangular 5.5903 cd 0.24 ∞ X
Angular alignment
photometer )( PPg
7E-5 B rectangular 2.7951 cd 0.007 ∞ X
Relative distance
variatioin PSS1 dd
0.0012 B rectangular -5.5903 cd -0.24 ∞ X
Temperature coefficient
of LED S1
0.0001 K-1
B normal 0 0.007 ∞ X
Temperature above
nominal temp. aS1T
0.28 K B rectangular 0.0053 cd/K 0.05 ∞ X
Angular tilt )( 11 SSh 0.0025 B rectangular -2.7951 cd -0.25 ∞ X
Lateral misalignment
)( xS dk 1
5R-5 B rectangular -2.7951 cd -0.005 ∞ X
Combined standard unc
ertainty (%)
-- -- normal -- 0.80 > 1000 --
Table 4-56. METAS uncertainty budget of averaged LED intensity measurement for blue
LEDs (B).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contribut
ion (%)
Deg. of
freedo
m
Correl
ated?
Distance photometer
bench PSd
1.15E-4 m B rectangular 17.9822
cd/m
0.23 ∞ X
Mean value photometer
signal PS1y
6E-6 V A t 0.4000 cd/V <0.001 9 X
APMP.PR-S3a Averaged LED Intensity Final Report
72
Mean value photometer
dark signal PS0y
4E-6 V A t -0.4000 cd/V <0.001 9 X
Responsivity photometer
CR1s
0.1029
nA/lx
B normal -0.03495
cd·lx/nA
-0.40 ∞ O
Calibration factor DVM
gain resistor Pc
5E-5 B normal 0.8991 cd 0.005 ∞ O
Gain resistor photometer
PS1G 0.001 kΩ B normal -8.9911E-04
cd/kΩ
<0.001 ∞ O
Spectral mismatch
correction factor SMCf
0.015 B normal 0.8739 cd 1.46 ∞ X
Measured current of LED
SJ 0.002 mA B normal 0.0324
cd/mA
0.01 ∞ X
Intensity to current
exponent JSm
0.02 B normal 0 0 ∞ X
Relative distance
variation, photomter
PSP dd
0.0012 B rectangular 1.7982 cd 0.24 ∞ X
Angular alignment
photometer )( PPg
7E-5 B rectangular 0.8991 cd 0.007 ∞ X
Relative distance
variatioin PSS1 dd
0.0012 B rectangular -1.7982 cd -0.24 ∞ X
Temperature coefficient
of LED S1
0.0001 K-1
B normal 0 0 ∞ X
Temperature above
nominal temp. aS1T
0.28 K B rectangular -0.0016 cd/K -0.05 ∞ X
Angular tilt )( 11 SSh 0.0025 B rectangular -0.8991 cd -0.25 ∞ X
Lateral misalignment
)( xS dk 1
5R-5 B rectangular -0.8991 cd -0.005 ∞ X
Combined standard unc
ertainty (%)
-- -- normal -- 1.59 > 1000 --
Table 4-57. METAS uncertainty budget of averaged LED intensity measurement for white
LEDs (W).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contribut
ion (%)
Deg. of
freedo
m
Correl
ated?
Distance photometer
bench PSd
1.15E-4 m B rectangular 13.8016
cd/m
0.23 ∞ X
Mean value photometer
signal PS1y
6E-6 V A t 0.3913 cd/V <0.001 9 X
Mean value photometer
dark signal PS0y
4E-6 V A t -0.3913 cd/V <0.001 9 X
Responsivity photometer
CR1s
0.1029
nA/lx
B normal -0.02683
cd·lx/nA
-0.40 ∞ O
APMP.PR-S3a Averaged LED Intensity Final Report
73
Calibration factor DVM
gain resistor Pc
5E-5 B normal 0.6901 cd 0.005 ∞ O
Gain resistor photometer
PS1G 0.001 kΩ B normal -6.9008E-04
cd/kΩ
<0.001 ∞ O
Spectral mismatch
correction factor SMCf
0.003 B normal 0.6855 cd 0.30 ∞ X
Measured current of LED
SJ 0.002 mA B normal 0.0276
cd/mA
0.008 ∞ X
Intensity to current
exponent JSm
0.02 B normal 0 0 ∞ X
Relative distance
variation, photomter
PSP dd
0.0012 B rectangular 1.3802 cd 0.24 ∞ X
Angular alignment
photometer )( PPg
7E-5 B rectangular 0.6901 cd 0.007 ∞ X
Relative distance
variatioin PSS1 dd
0.0012 B rectangular -1.3802 cd -0.24 ∞ X
Temperature coefficient
of LED S1
0.0001 K-1
B normal 0 0 ∞ X
Temperature above
nominal temp. aS1T
0.28 K B rectangular -0.0011 cd/K -0.04 ∞ X
Angular tilt )( 11 SSh 0.001 B rectangular -0.6901 cd -0.10 ∞ X
Lateral misalignment
)( xS dk 1
5R-5 B rectangular -0.6901 cd -0.005 ∞ X
Combined standard unc
ertainty (%)
-- -- normal -- 0.66 > 1000 --
Table 4-58. METAS uncertainty budget of averaged LED intensity measurement for diffuser-
type green LEDs (D).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contribut
ion (%)
Deg. of
freedo
m
Correl
ated?
Distance photometer
bench PSd
1.15E-4 m B rectangular 1.7080 cd/m 0.23 ∞ X
Mean value photometer
signal PS1y
6E-6 V A t 0.0397 cd/V <0.001 9 X
Mean value photometer
dark signal PS0y
4E-6 V A t -0.0397 cd/V <0.001 9 X
Responsivity photometer
CR1s
0.1029
nA/lx
B normal -0.00332
cd·lx/nA
-0.40 ∞ O
Calibration factor DVM
gain resistor Pc
5E-5 B normal 0.0854 cd 0.005 ∞ O
Gain resistor photometer
PS1G 0.001 kΩ B normal -8.5399E-06
cd/kΩ
<0.001 ∞ O
APMP.PR-S3a Averaged LED Intensity Final Report
74
Spectral mismatch
correction factor SMCf
0.007 B normal 0.0836 cd 0.69 ∞ X
Measured current of LED
SJ 0.002 mA B normal 0.0032
cd/mA
0.008 ∞ X
Intensity to current
exponent JSm
0.02 B normal 0 0 ∞ X
Relative distance
variation, photomter
PSP dd
0.0012 B rectangular 0.1708 cd 0.24 ∞ X
Angular alignment
photometer )( PPg
7E-5 B rectangular 0.0854 cd 0.007 ∞ X
Relative distance
variatioin PSS1 dd
0.0012 B rectangular -0.1708 cd -0.24 ∞ X
Temperature coefficient
of LED S1
0.0001 K-1
B normal 0 0 ∞ X
Temperature above
nominal temp. aS1T
0.28 K B rectangular 0.0002 cd/K 0.05 ∞ X
Angular tilt )( 11 SSh 0.0003 B rectangular -0.0854 cd -0.03 ∞ X
Lateral misalignment
)( xS dk 1
5R-5 B rectangular -0.0854 cd -0.005 ∞ X
Combined standard unc
ertainty (%)
-- -- normal -- 0.90 > 1000 --
Model for junction voltage:
L0L1aL0aLrelL,CLL 1 UUTTccU
Description of terms:
LU output quantity: junction voltage of the LED at certified conditions.
Lc = 1.0000, DVM calibration factor with absolute standard MU )( Lcu = 1E-5;
Type B with DOF v , no correlation.
Cc = 1.000, non-equivalence of the contact. We have tried different connectors. A
spread in junction voltages have been observed even with 4 wires connections. The
estimated absolute standard MU )( Ccu = 0.0020; Type B with DOF v , no
correlation.
relL, = 0.000015, relative temp. coefficient according standard MU )( relL,u = 5E-6;
Type B with DOF v , no correlation.
aLT = 22.6 °C, ambient temperature with ±0.5°C RPD, converted into standard MU
)( aLTu = (0.5/ 3 = 0.29)°C; Type B with DOF v , no correlation.
aL0T = 23.0 °C, nominal ambient temperature, no uncertainty
L1U = 1.94058 V, measured voltage (DVM), with standard MU of L1Uu = 0.00011
APMP.PR-S3a Averaged LED Intensity Final Report
75
V, 361 readings, Type A with DOF 360v , no correlation.
L0U = 0.00002 V, measured zero voltage (DVM), with standard MU of L1Uu =
0.00011 V, 361 readings , Type A with DOF 360v , no correlation.
Table 4-59. METAS uncertainty budget of junction voltage measurement.
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
DVM mean value voltage
L1U
0.00011 V A t 0.99999
V/V
0.0055 360 X
DVM calibration factor
Lc
1.0E-5 B normal 1.94055 V 0.0010 ∞ O
Relative temperature
coefficienct relL,
5.0E-6 K-1
B normal -0.77622
VK
-0.0002 ∞ X
Ambient temperature aLT 0.29 °C B rectangular 0.00003
V/°C
0.0004 ∞ X
Offset voltage L0U 0.00011 V A t -0.99999
V/V
-0.0055 360 X
Non-equivalence of contact
Cc
0.0021 B rectangular 1.94055 V 0.21 ∞ X
Combined standard unce
rtainty (V)
-- -- Normal -- 0.21 >1000 --
4.9. NMC-A*STAR
4.9.1. Measurement setup
The measurement setup of the averaged LED intensity is shown in Fig. 4-31 and Fig. 4-32.
The LED light receptor is an integrating sphere with a 1 cm2 opening input port
according to the CIE requirement. The LED light received by the receptor is fed to a
spectroradiometer (Model OL770 made by Optronic Laboratories) through an optical
fibre. The spectroradiometer uses a cooled CCD detector with 128 x 1024 elements
covering the wavelength range of 380 nm to 1100 nm. Its bandwidth (FWHM) is about
3.5 nm and the data interval is 1 nm.
The LED is driven by a programmable DC Source (Model 7651 made by
Yokogawa). The driving current is measured using a calibrated precision resister and a
calibrated digital volt meter (Model 34420A made by Hewlett Packard). The electric
connection in the LED holder is a 4-wire connection to achieve the accurate
measurement of the LED forward voltage.
APMP.PR-S3a Averaged LED Intensity Final Report
76
Fig. 4-31. LED averaged intensity measurement setup in A*STAR.
Fig. 4-32. Photograph of the LED averaged intensity measurement setup in A*STAR.
4.9.2. Mounting and alignment
Fig. 4-33 is a picture of the LED light receptor and Fig. 4-34 shows the LED holder.
The alignment laser and the precision auto level 2 (telescope) are used to define
the measurement axis. The angular and centre alignment of the LED is monitored by a
video camera attached to the auto level 2. Fig. 4-35 shows a picture of the correctly
aligned LED viewed by the camera. The auto level 1 and the precision rail as shown in
Fig. 2 are used to set the distance of 100 mm between the LED and the receptor
accurately.
LED
Spectral irradiance
standard lamp Shutter
Alignment
laser
Auto level 1
(telescope)
Auto level 2
(telescope)
Video
Camera
Standard
photometer
head
LED light
receptor
APMP.PR-S3a Averaged LED Intensity Final Report
77
Fig. 4-33. LED receptor;
Fig. 4-34. LED holder;
Fig. 4-35. LED alignment in A*STAR.
4.9.3. Traceability
The relative spectral responsivity of the spectroradiometer is calibrated by a spectral
irradiance standard lamp traceable to NMC’s spectral irradiance scale. The stray light
error of the spectroradiometer is corrected using cut-on filters. The absolute luminous
responsivity of the spectroradiometer is calibrated using a standard photometer traceable
to NMC’s luminous intensity scale. The average luminous intensity is calculated by
integrating the spectral irradiance measured by the spectroradiometer. The same data is
also used to calculate the emitted colour of the LED (S3c).
4.9.4. Measurement uncertainty
Tables in the following are the detailed uncertainty budgets of the CIE B averaged LED
intensity measurement for the LEDs used in this APMP LED comparison.
The uncertainty evaluation is carried out according to Guide to the Expression of
Uncertainty in Measurement (GUM). The artefact-dependent uncertainties shown in the
table with * adopt the largest uncertainty values registered among the same type of LEDs
measured. Expanded uncertainty are evaluated at a confidence level of approximately 95%
with a coverage factor normally k = 2.
Table 4-60. A*STAR uncertainty budget of averaged LED intensity measurement for red LEDs
(R).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Calibration of standard
photometer
B normal 1 0.550 ∞ Yes
APMP.PR-S3a Averaged LED Intensity Final Report
78
Drift of the standard
photometer
B rectangular 1 0.116 ∞ Yes
Spectroradiometer transfer
measurement (non-
linearity)*
B rectangular 1 0.058 ∞ No
LED axis alignment,
angular
Included in the component “Reproducibility” of three independent
measurements.
LED axis alignment,
translational
Included in the component “Reproducibility” of three independent
measurements.
Distance measurement 0.289 % B rectangular 2 0.578 ∞ Yes
Calibration of current
feeding
0.0058 % B rectangular 0.8 0.005 ∞ Yes
Scattered light including
reflection from holder
B rectangular 1 0.116 ∞ Yes
Wavelength scale of
spectroradiometer*
0.2 nm B rectangular 2.17 %/nm 0.434 ∞ No
stray light correction of
spectroradiometer (20 % of
correction)*
B rectangular 1 0.208 ∞ No
Reproducibility A t 1 0.520 2 No
Combined standard unce
rtainty (%)
-- -- normal -- 1.1 37 --
Table 4-61. A*STAR uncertainty budget of averaged LED intensity measurement for green
LEDs (G).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Calibration of standard
photometer
B normal 1 0.550 ∞ Yes
Drift of the standard
photometer
B rectangular 1 0.116 ∞ Yes
Spectroradiometer transfer
measurement (non-
linearity)*
B rectangular 1 0.058 ∞ No
LED axis alignment,
angular
Included in the component “Reproducibility” of three independent
measurements.
LED axis alignment,
translational
Included in the component “Reproducibility” of three independent
measurements.
Distance measurement 0.289 % B rectangular 2 0.578 ∞ Yes
Calibration of current
feeding
0.0058 % B rectangular 0.8 0.005 ∞ Yes
Scattered light including
reflection from holder
B rectangular 1 0.116 ∞ Yes
APMP.PR-S3a Averaged LED Intensity Final Report
79
Wavelength scale of
spectroradiometer*
0.2 nm B rectangular 2.17 %/nm 0.289 ∞ No
stray light correction of
spectroradiometer (20 % of
correction)*
B rectangular 1 0.092 ∞ No
Reproducibility A t 1 0.347 2 No
Combined standard unce
rtainty (%)
-- -- normal -- 0.94 107 --
Table 4-62. A*STAR uncertainty budget of averaged LED intensity measurement for blue
LEDs (B).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Calibration of standard
photometer
B normal 1 0.550 ∞ Yes
Drift of the standard
photometer
B rectangular 1 0.116 ∞ Yes
Spectroradiometer transfer
measurement (non-
linearity)*
B rectangular 1 0.058 ∞ No
LED axis alignment,
angular
Included in the component “Reproducibility” of three independent
measurements.
LED axis alignment,
translational
Included in the component “Reproducibility” of three independent
measurements.
Distance measurement 0.289 % B rectangular 2 0.578 ∞ Yes
Calibration of current
feeding
0.0058 % B rectangular 0.8 0.005 ∞ Yes
Scattered light including
reflection from holder
B rectangular 1 0.116 ∞ Yes
Wavelength scale of
spectroradiometer*
0.2 nm B rectangular 2.17 %/nm 0.434 ∞ No
stray light correction of
spectroradiometer (20 % of
correction)*
B rectangular 1 0.208 ∞ No
Reproducibility A t 1 0.520 2 No
Combined standard unce
rtainty (%)
-- -- normal -- 1.1 37 --
Table 4-63. A*STAR uncertainty budget of averaged LED intensity measurement for white
LEDs (W).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
APMP.PR-S3a Averaged LED Intensity Final Report
80
Calibration of standard
photometer
B normal 1 0.550 ∞ Yes
Drift of the standard
photometer
B rectangular 1 0.116 ∞ Yes
Spectroradiometer transfer
measurement (non-
linearity)*
B rectangular 1 0.231 ∞ No
LED axis alignment,
angular
Included in the component “Reproducibility” of three independent
measurements.
LED axis alignment,
translational
Included in the component “Reproducibility” of three independent
measurements.
Distance measurement 0.289 % B rectangular 2 0.578 ∞ Yes
Calibration of current
feeding
0.0058 % B rectangular 0.8 0.005 ∞ Yes
Scattered light including
reflection from holder
B rectangular 1 0.116 ∞ Yes
Wavelength scale of
spectroradiometer*
0.2 nm B rectangular 2.17 %/nm 0.289 ∞ No
stray light correction of
spectroradiometer (20 % of
correction)*
B rectangular 1 0.092 ∞ No
Reproducibility A t 1 0.173 2 No
Combined standard unce
rtainty (%)
-- -- normal -- 0.92 1557 --
Table 4-64. A*STAR uncertainty budget of averaged LED intensity measurement for diffuser-
type green LEDs (D).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Calibration of standard
photometer
B normal 1 0.550 ∞ Yes
Drift of the standard
photometer
B rectangular 1 0.116 ∞ Yes
Spectroradiometer transfer
measurement (non-
linearity)*
B rectangular 1 0.231 ∞ No
LED axis alignment,
angular
Included in the component “Reproducibility” of three independent
measurements.
LED axis alignment,
translational
Included in the component “Reproducibility” of three independent
measurements.
Distance measurement 0.289 % B rectangular 2 0.578 ∞ Yes
Calibration of current
feeding
0.0058 % B rectangular 0.8 0.005 ∞ Yes
APMP.PR-S3a Averaged LED Intensity Final Report
81
Scattered light including
reflection from holder
B rectangular 1 0.116 ∞ Yes
Wavelength scale of
spectroradiometer*
0.2 nm B rectangular 2.17 %/nm 0.289 ∞ No
stray light correction of
spectroradiometer (20 % of
correction)*
B rectangular 1 0.092 ∞ No
Reproducibility A t 1 0.462 2 No
Combined standard unce
rtainty (%)
-- -- normal -- 1.0 46 --
Table 4-65 is the detailed uncertainty budget of the junction voltage
measurement, representatively presented for the red LEDs. The artefact-dependent
uncertainties shown in the table with * adopt the largest uncertainty values registered
among the same type of LEDs measured.
Table 4-65. A*STAR uncertainty budget of junction voltage measurement.
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contribut
ion (V)
Deg.
of fre
edom
Correl
ated?
Calibration of DVM B normal 1 9.5E-5 ∞ Yes
Position of junction (0.05
Ω)
B rectangular 1 5.78E-4 ∞ No
Drift of junction voltage B rectangular 1 1.73E-4 ∞ No
Reproducibility* A t 1 7.64E-4 5 No
Combined standard unce
rtainty (V)
-- -- normal -- 9.8E-4 13 --
4.10. VSL
4.10.1. Measurement setup
The quantity for average LED intensity and total luminous flux of LEDs (as defined by the
key-comparison protocol) are measured with a goniometer facility specifically designed
and build for small single LED light sources. The facility is based on the method where
the light source is turned and the detector stands still. Therefore the facility consists out
of a detector platform and a turn-able light source unit. The light source unit includes
two rotation stages, a LED mounting unit and one linear translation stage. The linear
APMP.PR-S3a Averaged LED Intensity Final Report
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translation stage is applied to be able to change the distance between the turn-able
light source unit and the detector platform. The two rotation stages are perpendicular
mounted to each other so that the LED can be rotated exactly in the midpoint of each
stage.
The detector platform consists out of an illuminance meter with a circular
aperture with a surface of 100 mm2 and an array-spectroradiometer (SRM). The SRM is
used to correct for colour mismatch introduced by the detector and the individual LED. In
order to reduce stray light a baffle was places between the detector platform and the
turn-able light source unit. The aperture of the baffle was large compare to the diameter
of the detector and the LED to be measured.
Fig. 4-36. Schematic drawing of LED goniometer facility at VSL.
4.10.2. Mounting and alignment
The LED is fixed in a holder, which is mounted into a mounting unit. The mounting unit
is mounted on the turn-able light source unit consisting out of the two rotation stages.
The LED holder is shown in the following figure.
Fig. 4-37. VSL LED holder.
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83
The LED holder clamps the two LED pins with two parallel copper plates. The
copper plates are connected to the current source which provides the LED with operating
current. The mounting unit allows one to translate the LED in both vertical as well as
horizontal direction, and also to tilt the LED. This alignment unit is in turn mounted to
the two rotation stages. The layout of the alignment system of the LED facility together
with the mounted holder is shown in the following figure.
Fig. 4-38. Turn-able light source unit of the LED goniometer facility at VSL.
In Fig. 4-38, one sees the LED mounted on the mounting unit fixed on a two axis
rotational system. The alignment of the LED with regards to the detector as well as axis
of rotation is done as follows:
1. A high resolution camera is placed perpendicular to the mounted LED.
2. The mounted LED is rotated and visually inspected by using the high resolution camera.
3. If the mounted LED is in the centre of the rotational axis, no movement is detected
with the camera, otherwise translation is observed. The mounted LED is then
iteratively adjusted until no translation of the mounted LED is visible with the camera.
This is iteratively repeated also for the polar rotation. When varying the polar angle the
alignment criteria was that the location of the LED tip remained constant.
4. The mounted LED and illuminance detector are then optically aligned with the double
alignment laser.
The nominal distance between LED and detector is brought to 100 mm by making
use of an electronic translation stage where the LED alignment axes are mounted on, as
well as a calibrated gauge block of nominal length 100 mm. The gauge block is placed
against the detector reference surface and the LED is translated precisely until contact is
made with the gauge block. This translation distance is recorded. The gauge block is
then removed and the LED is translated back to the correct position. The distance is then
100 mm between detector and LED. The following figure illustrates this graphically.
APMP.PR-S3a Averaged LED Intensity Final Report
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Fig. 4-39. Schematic drawing of the detector versus LED distance determination at VSL.
4.10.3. Traceability
The average LED intensity measurement of an LED at VSL has as the traceability route as
shown in Fig. 4-40.
Fig. 4-40. Traceability of an average luminous intensity measurement of an LED at VSL.
The spectral responsivity scale is derived from an Absolute Cryogenic Radiometer
(ACR) by using a double monochromator facility 8 . The same facility is used for the
determination of the illuminance responsivity by using a scanning beam method and the
relative spectral irradiance responsivity of the illuminance meter 9 . Knowing the
illuminance responsivity of an illuminance meter and using a calibrated gauge block one
can determine the luminous intensity of a LED. The gauge block is calibrated and
traceable to the national standard for length. Each measurement within the traceability
chain is conducted by using digital multimeters for measurement of detector current, LED
current and LED voltage. These measurements are traceable to the national standard for
current and voltage by the use of calibrated meters.
8 Comparison of monochromator-based and laser-based cryogenic radiometry, Metrologia 1998, 35, 431-435. 9 Novel calibration method for filter radiometers, Metrologia 1999, 36, 179-182.
Cryogenic radiometer VSL Spectral responsivity scale
(A/W)
ACR facility VSL Illuminance responsivity
(A/lx)
LED Goniomter facility VSL Average luminous intensity and total
luminous flux (cd) and or (lm)
Electrical department for the traceability to the national standard of current and voltage (A) and (V)
Length department for the traceability to the national standard of length (m)
APMP.PR-S3a Averaged LED Intensity Final Report
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4.10.4. Measurement uncertainty
After the LED and detector are aligned, the following steps are performed to measure
the average LED intensity of each of the fourteen LEDs respectively:
1. The LED is brought to an operating current of nominal 20 mA.
2. The whole setup is enclosed by a thermal insulation box and allowed to stabilize for at
least 20 minutes.
3. The measurement of the illuminance at different angles are performed to investigate
the circle symmetry of the illuminance, i.e the LED is rotated in the perpendicular
direction with regards to the illuminance detector.
4. The stray light was measured by blocking light only on the optical axis, through the use
of a blocking strip.
5. The dark signal was measured, by closing the baffle situated in front of the detector
completely.
6. The average luminous intensity of the LED is calculated knowing the illuminance and
distance between detector and LED. This done as is shown in the following model
equation.
Model equation for the averaged LED intensity:
.11 2
__
22 RSA
UU
RSA
UREI
v
sl
v
cvv
Ev is the measured illuminance of the LED,
Sv is the responsivity of the reference standard illuminance meter,
Uc is the corrected measured voltage,
Ul is the measured voltage with shutter open,
Us is the measured voltage due to stray light, including dark signal. This is done by
blocking light on optical axis, for the straight light. For the dark signal the light
was blocked by a shutter.
Av is the amplification factor ,
R is the distance between the LED and the detector, which is 100mm in our case.
The responsivity is corrected for the colour mismatch. This is so since the spectral
responsivity of the detector, as well as the emitted spectrum of the LED are known. One
can then perform the required correction. The colour correction factor is calculated as
stated in the following equation:
.)()(
)()('
det
LV
LVF
CIE
APMP.PR-S3a Averaged LED Intensity Final Report
86
F’ is the correction factor for colour mismatch due to the detector.
VCIE
(λ) is the luminous sensitivity function as defined by the CIE,
VDET
(λ) is the spectral responsivity of the detector which is measured
L (λ) is the measured spectrum of the LED.
An example of an illuminance measurement is shown in Fig. 4-41. As can be
seen, there is strong angle dependence. Since the LED was aligned mechanically with its
casing/lens as reference, this dependence is thought to be due to the optical and
geometrical axis of the LED not coinciding. It is thus important which point is taken as
reference.
Fig. 4-41. An example illuminance measurement of a LED determined at different angles
measured in VSL.
The value at position 0 degrees was chosen to be used when calculating the
average intensity value. This position corresponds to the following geometrical position
of the LED. If one looks perpendicular at the front of the LED one can see that one side
is not round, but flat. That flat part is taken as reference and is always kept at the left
when inspected with the camera for alignment positioned at the same position as the
illuminance meter. This is schematically shown in Fig. 4-42. Here one sees a schematic
drawing of the LED casing/lens as seen from the front, with the LED chip in die centre.
258
260
262
264
266
0 100 200 300 400
Illu
min
ance
/a.u
.
Angle /degrees
APMP.PR-S3a Averaged LED Intensity Final Report
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Fig. 4-42. Front view of an LED.
The comparison protocol states that the participant describes the total uncertainty
in detail for the LEDs of each color. As the total uncertainty of each LED is depending on
individual components the uncertainty from one LED to one other is different. Knowing
this we chose to present a detailed uncertainty budget of that LED that has the lowest
uncertainty, instead of determining the average total uncertainty of the LEDs with the
same color. This was done since no information is given how to determine the average
uncertainty of a group of LEDs. The detailed uncertainty budgets are summarized in the
tables below.
Table 4-66. VSL uncertainty budget of averaged LED intensity measurement for red LEDs (R).
Uncertainty Component Standard
uncertain
ty (%) Ty
pe
Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedo
m
Corre
lated
Axis alignment,
translational
A normal 1 0.25 28 X
Axis alignment, angular B rectangular 1 0.08 ∞ X
Current feeding of LED B normal 1 0.01 ∞ O
Reproducibility B normal 1 0.01 ∞ X
Detector readout A normal 1 0.04 9 O
Stray light A normal 1 0.03 9 O
Trans-impedance amplifier B normal 1 0.001 ∞ O
Responsivity of the
detector (calibration)
B normal 1 0.15 ∞ O
Spectral mismatch
correction of detector
B normal 1 0.22 ∞ X
Non-uniformity of source B rectangular 1 0.08 ∞ X
Distance between LED and
detector
0.294 B rectangular 2 0.59 ∞ O
Combined standard
uncertainty (%)
-- -- normal -- 0.70 ∞ --
APMP.PR-S3a Averaged LED Intensity Final Report
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Table 4-67. VSL uncertainty budget of averaged LED intensity measurement for green LEDs
(G).
Uncertainty Component Standard
uncertain
ty (%) Ty
pe
Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedo
m
Corre
lated
Axis alignment,
translational
A normal 1 0.29 28 X
Axis alignment, angular B rectangular 1 0.33 ∞ X
Current feeding of LED B normal 1 0.01 ∞ O
Reproducibility B normal 1 0.12 ∞ X
Detector readout A normal 1 0.01 9 O
Stray light A normal 1 0.01 9 O
Trans-impedance amplifier B normal 1 0.001 ∞ O
Responsivity of the
detector (calibration)
B normal 1 0.15 ∞ O
Spectral mismatch
correction of detector
B normal 1 0.11 ∞ X
Non-uniformity of source B rectangular 1 0.21 ∞ X
Distance between LED and
detector
0.27 B rectangular 2 0.54 ∞ O
Combined standard
uncertainty (%)
-- -- normal -- 0.76 ∞ --
Table 4-68. VSL uncertainty budget of averaged LED intensity measurement for blue LEDs (B).
Uncertainty Component Standard
uncertain
ty (%) Ty
pe
Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedo
m
Corre
lated
Axis alignment,
translational
A normal 1 0.12 28 X
Axis alignment, angular B rectangular 1 0.41 ∞ X
Current feeding of LED B normal 1 0.01 ∞ O
Reproducibility B normal 1 0.09 ∞ X
Detector readout A normal 1 0.03 9 O
Stray light A normal 1 0.03 9 O
Trans-impedance amplifier B normal 1 0.001 ∞ O
Responsivity of the
detector (calibration)
B normal 1 0.15 ∞ O
Spectral mismatch
correction of detector
B normal 1 0.07 ∞ X
Non-uniformity of source B rectangular 1 0.07 ∞ X
Distance between LED and
detector
0.27 B rectangular 2 0.54 ∞ O
Combined standard
uncertainty (%)
-- -- normal -- 0.72 ∞ --
Table 4-69. VSL uncertainty budget of averaged LED intensity measurement for white LEDs
(W).
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89
Uncertainty Component Standard
uncertain
ty (%) Ty
pe
Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedo
m
Corre
lated
Axis alignment,
translational
A normal 1 0.11 28 X
Axis alignment, angular B rectangular 1 0.02 ∞ X
Current feeding of LED B normal 1 0.01 ∞ O
Reproducibility B normal 1 0.1 ∞ X
Detector readout A normal 1 0.04 9 O
Stray light A normal 1 0.03 9 O
Trans-impedance amplifier B normal 1 0.001 ∞ O
Responsivity of the
detector (calibration)
B normal 1 0.15 ∞ O
Spectral mismatch
correction of detector
B normal 1 0.05 ∞ X
Non-uniformity of source B rectangular 1 0.1 ∞ X
Distance between LED and
detector
0.26 B rectangular 2 0.52 ∞ O
Combined standard
uncertainty (%)
-- -- normal -- 0.58 ∞ --
Table 4-70. VSL uncertainty budget of averaged LED intensity measurement for diffuser-type
green LEDs (D).
Uncertainty Component Standard
uncertain
ty (%) Ty
pe
Probability
distribution
Sensitivity
coefficient
Contribution
(%)
Deg. of
freedo
m
Corre
lated
Axis alignment,
translational
A normal 1 0.02 28 X
Axis alignment, angular B rectangular 1 0.04 ∞ X
Current feeding of LED B normal 1 0.01 ∞ O
Reproducibility B normal 1 0.02 ∞ X
Detector readout A normal 1 0.28 9 O
Stray light A normal 1 0.2 9 O
Trans-impedance amplifier B normal 1 0.001 ∞ O
Responsivity of the
detector (calibration)
B normal 1 0.15 ∞ O
Spectral mismatch
correction of detector
B normal 1 0.11 ∞ X
Non-uniformity of source B rectangular 1 0.32 ∞ X
Distance between LED and
detector
0.31 B rectangular 2 0.62 ∞ O
Combined standard
uncertainty (%)
-- -- normal -- 0.80 ∞ --
Table 4-71 is the detailed uncertainty budget of the junction voltage
measurement.
APMP.PR-S3a Averaged LED Intensity Final Report
90
Table 4-71. VSL uncertainty budget of junction voltage measurement.
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contribut
ion (%)
Deg.
of fre
edom
Correl
ated?
Calibration of DVM B normal 1 1.2E-5 ∞ O
Junction position
dependence
B rectangular 1 0.081 ∞ X
Reproducibility* A t 1 0.0001 9 X
Combined standard unce
rtainty (%)
-- -- normal -- 0.081 ∞ --
4.11. NMIA10
4.11.1. Measurement setup
The averaged luminous intensity of each LED was measured using a windowless silicon
detector mounted behind a 100 mm2 area round precision aperture located 100 mm in
front of the tip of each LED. Simultaneously the relative spectral intensity was measured
using an array spectrometer. One end of an optical fibre was placed next to, and behind,
the precision aperture and directed towards the LED, the other end of the fibre was
connected directly to the spectrometer.
The luminous intensity was calculated using the signal obtained from the silicon
detector, the relative spectral response of the silicon detector, knowledge of the
geometry of the measurement setup, the values of relative spectral irradiance of each
LED and the defined values of CIE V(λ) 1931.
4.11.2. Mounting and alignment
For the measurements of LED intensity, each LED was mounted in a custom made
aluminium LED mount with the front surface of the mount painted with spectrally non-
selective gloss black paint. A separate aluminium base was provided for the diffused
LEDs.
Each aluminium mount was set up to be within 0.1 of perpendicular to the
measurement axis of the receiving radiometer by using a laser/mirror alignment
technique. Since the flanged LEDs are not parallel sided, orthogonality of the LEDs
10 The technical report and uncertainty budgets of NMIA are not reviewed by the participants due to the delayed submission.
APMP.PR-S3a Averaged LED Intensity Final Report
91
relied upon the orthogonality of the LED base flange to the measurement axis. A value
of 0.5° was used for uncertainty calculations, allowing for imperfections in each diode
for these LEDs.
For the diffused diodes, which were not flanged, the aluminium mount provided a
close fit to the parallel sides of the diode, again 0.5° was allowed for uncertainty
calculations.
Each LED aluminium base was fitted to a standard kinematic mount and placed
on the receiving kinematic base on top of a special carriage having five degrees of
freedom in its physical adjustments as shown in Fig. 4-43.
5 degrees of freedom
physical adjustment.
Kinematic
mount
LED
Measurement axis
Fig. 4-43. Side view diagram of measurement setup in NMIA showing the LED mounted in the aluminium mount supported by a carriage having five degrees of freedom in
physical adjustment.
The LEDs were held in place by a cylindrical nylon spacer with two holes running
parallel to the centre of the cylinder, allowing the legs of the LED to pass through the
spacer. The spacer was held in place using a copper side spring as shown in Fig. 4-44.
Grey nylon
support for
electrical
connectors
aluminium
mount
LED
White nylon spacer
Copper spring
Current feed and
voltage sensing leads
Fig. 4-44. Top view, cross-section diagram of LED mount in NMIA, showing the nylon spacer located by the copper spring, and including the grey nylon mount via which
electrical connections were made.
The legs of the LED were inserted into a grey nylon mount containing four screw
APMP.PR-S3a Averaged LED Intensity Final Report
92
tensioned gold contacts via which the LED current was supplied and the LED potential
was measured.
A temperature probe was attached to the aluminium base using aluminium tape
to provide reasonable thermal contact. This provided a cross-check on the LED base
temperature.
The detector system used was based on a calibrated Hamamatsu S6337
windowless silicon photodiode mounted behind a round 100 mm2 area polished steel
aperture with aperture lands at a 60 angle to the measurement axis. The area
surrounding the aperture was covered using a shield plate having a diffuse black
spectrally non-selective paint to reduce inter-reflection between the LED mount and the
aperture as shown in Fig. 4-45.
shutter
LED
Spectrometer Silicon
detector
Aperture
Black shield
plate
Optical fibre
Fig. 4-45. Diagram of the detection system with precision steel aperture masked by blackened cover, optical fibre fed spectrometer and shutter.
A small area shutter was placed between the LED and the detector aperture to
allow the stray light level to be recorded as far as possible. This was later subtracted
from the signal level.
The detector was mounted on an X-Y scanning stage with a resolution of 2 µm.
The detector was aligned with the LED centre by using a bench telescope with a ring
sight aligned along the measurement axis.
The separation between the tip of each LED and the plane of the detector
aperture was determined using a calibrated vernier mounted telescope with an optical
axis perpendicular to the measurement axis. The vernier resolution for this telescope was
0.01 mm.
The shutter did not restrict light entering the optical fibre and so the electronic
dark level (internal to the spectrometer) was used for the dark level of the spectrometer.
The optical fibre was aligned to point directly at the LED by finding the maximum signal.
For each LED the spatial uniformity of the irradiance output from the LED was
APMP.PR-S3a Averaged LED Intensity Final Report
93
measured over approximately ± 20 mm around the central measurement position in
order to determine uncertainties due to spatial and angular variation.
4.11.3. Traceability
The windowless silicon photo-diode used was calibrated for spectral responsivity against
NMIA reference silicon photo-diodes (report RN090120, dated 9 February 2009). The
reference silicon diodes were in turn calibrated directly against the NMIA primary
standard cryogenic radiometer at selected laser wavelengths as well as for relative
spectral response (reports RN45905, RN45906, RN45907, RN060931 and RN060932,
dated 8 May 2003, 9 May 2003, 9 May 2003, 25 Aug 2006 and 25 Aug 2006 respectively).
The spectrometer was calibrated using NMIA colour standard source FEL6. This
source was calibrated for relative spectral irradiance directly against a blackbody
(RN46736, dated 13 July 2004) at the same time, and using the same method, as for the
lamps NMIA used in the CCPR K1-a 2005 Spectral Irradiance Key Comparison. Further
details of the traceability of the relative spectral irradiance of lamp FEL6 can be found in
the final report of this comparison.
4.11.4. Measurement uncertainty
In this section, all indicated uncertainty values refer to the standard uncertainty unless
explicitly described otherwise. All uncertainty components have a sensitivity coefficient of
1 unless explicitly described otherwise.
The spatial distribution of the irradiance field in the plane at a distance of 100mm
from the tip of each LED was measured over a square area of approximately 40 mm ×
40 mm. The results were analysed and the largest gradient of irradiance within a 1 mm
distance of the centre of the scan was evaluated. This gradient was used in the
calculation of the uncertainty components for alignment, both angular and translational,
as follows.
The angular alignment of the mount was considered to have an uncertainty of
0.1°. The LED within the mount was estimated to contribute an uncertainty of between
0.1° and 0.2°, with the angular alignment of the aperture making a similar contribution.
To allow for all these angular uncertainties, a value of 0.5° was estimated for the
uncertainty of misalignment of the LED geometric axis to the measurement axis. At a
distance of 100 mm, this is approximately equivalent to a translational misalignment of
0.9 mm, which when multiplied by the gradient (as determined above) gave an estimate
of the uncertainty in irradiance due to any angular misalignment.
APMP.PR-S3a Averaged LED Intensity Final Report
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The translational alignment of the LED to the centre of the aperture, in the plane
perpendicular to the measurement axis, was estimated to be 1.0 mm. This was
multiplied by the gradient (as determined above) to give an estimate of the uncertainty
in irradiance due to any translational misalignment.
The feed current to the LED was determined by measuring the voltage drop
across a calibrated standard resistor in series with the LED. A standard allowance used by
NMIA for this measurement is 0.01%, which easily covers all our standard resistor /
digital voltmeter combinations. Each LED was measured at a range of current values
close to the target current value of 20 mA and a relationship between the LED optical
output and the LED current was empirically determined for each. The current sensitivity
values determined were used to calculate the luminous intensity of each LED at the
target current value. These sensitivity values were subsequently used in determineation
of the current related uncertainty component.
As described above, a white nylon support was placed immediately behind the
LED to hold it in place during measurement. An obvious glow from the nylon was visible
during measurements, and would thus be the main contributor to stray light for all LED’s
except the Diffused type (which have virtually zero emission in the backward direction).
Subsequent to the main tests, the nylon support was painted black and a variation of
approximately 1.6% in the optical output was observed. This was used as the uncertainty
component for stray light. Other factors that could potentially contribute to stray light
were considered to be negligible as the shutter used was of a minimal size and the
irradiance level with the shutter closed was measured as the background and subtracted
for all measurements.
The detector response to each LED was calculated using the pre-determined
spectral response of the detector and the measured spectrum of the LED. The
wavelength resolution of the system used to measure the LED was 0.4 nm. The
calculations of the detector response to each LED were performed with spectral
displacements of both +0.4 nm and -0.4 nm to determine the variation of detector
response. This produced variations in the derived values of between 0.7% and 1.5%, and
it was decided to use the worst case of 1.5% as an estimate of uncertainty due to
spectral mismatch for all cases.
Two other factors were considered with regard to the measurement of the
spectrum of the LED, but were finally considered negligible in comparison to the 1.5%
described above. Firstly the optical fibre feed was positioned approximately 30° from the
main measurement axis, with the resultant possibility that the recorded spectrum was
APMP.PR-S3a Averaged LED Intensity Final Report
95
different from the on–axis spectrum. Separate tests were performed to measure the
variation in spectral content between the on axis and off axis measurements. Although
the differences were measurable, the cumulative effect was <0.5% in the value of the
calculated detector response. Secondly the stray light was not covered by subtraction of
a background level. However, other light sources were eliminated by the room being
dark, and stray light from undesirable reflections of the LED were most likely to have the
same or similar relative spectral content.
The traceable calibration of our detector for absolute spectral response has a
worst value of 0.4% (k = 2.0) over the whole visible range. Thus a value of 0.2% was
used as the estimate of uncertainty of the detector.
The measurement of Irradiance was performed by taking at least 30
measurements. The experimental standard deviation of the mean calculated from these
measurements (including measurements of the background ‘stray light’ levels) was used
as an estimate of the standard uncertainty and the degrees of freedom were estimated
to be 30.
The distance between the LED tip and the limiting aperture plane was able to be
set at 100.0 mm with an estimated uncertainty of 0.1 mm. Approximating the source to
be a point source meant an estimate of 0.1%, with a sensitivity coefficient of 2, could be
used as the uncertainty due to distance between the LED and the limiting aperture.
The limiting aperture used has an area close to 100.0 mm2 and has been calibrated with
an uncertainty of 0.25% (k = 2.0). Thus the standard uncertainty due to the area of the
limiting aperture was estimated to be 0.125%.
All measured photocurrents from the detector were within a 5:1 range of the
photocurrent measured when the detector was calibrated. A standard allowance of 0.01%
for this range of signal variation was used as the estimated uncertainty due to linearity of
the detector.
Table 4-72. NMIA uncertainty budget of averaged LED intensity measurement for red LEDs
(R).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Axis alignment, angular 0.9 B normal 1 0.9 100 X
Axis alignment,
translational
0.9 B normal 1 0.9 100 X
APMP.PR-S3a Averaged LED Intensity Final Report
96
Current feeding accuracy 0.010 B normal 1.03 0.01 30 O
Stray light 0.46 B rectangular 1 0.46 100 O
Spectral mismatch
correction
0.43 B rectangular 1 0.43 100 O
Calibration of photometer 0.20 B normal 1 0.2 100 O
Reading repeatability 0.0045 A t 1 0.0045 30 X
Distance setting 0.10 B normal 2.0 0.2 100 O
Aperture Area 0.125 B normal 1 0.125 100 O
Non-linearity 0.010 B normal 1 0.10 100 O
Combined standard unce
rtainty (%)
-- -- normal -- 1.45 320 --
Table 4-73. NMIA uncertainty budget of averaged LED intensity measurement for green LEDs
(G).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Axis alignment, angular 0.5 B normal 1 0.5 100 X
Axis alignment,
translational
0.5 B normal 1 0.5 100 X
Current feeding accuracy 0.010 B normal 0.74 0.007 30 O
Stray light 0.46 B rectangular 1 0.46 100 O
Spectral mismatch
correction
0.43 B rectangular 1 0.43 100 O
Calibration of photometer 0.20 B normal 1 0.2 100 O
Reading repeatability 0.007 A t 1 0.007 30 X
Distance setting 0.10 B normal 2.0 0.2 100 O
Aperture Area 0.125 B normal 1 0.125 100 O
Non-linearity 0.010 B normal 1 0.10 100 O
Combined standard unce
rtainty (%)
-- -- normal -- 1.00 475 --
APMP.PR-S3a Averaged LED Intensity Final Report
97
Table 4-74. NMIA uncertainty budget of averaged LED intensity measurement for blue LEDs
(B).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Axis alignment, angular 0.6 B normal 1 0.6 100 X
Axis alignment,
translational
0.6 B normal 1 0.6 100 X
Current feeding accuracy 0.010 B normal 0.82 0.08 30 O
Stray light 0.46 B rectangular 1 0.46 100 O
Spectral mismatch
correction
0.43 B rectangular 1 0.43 100 O
Calibration of photometer 0.20 B normal 1 0.2 100 O
Reading repeatability 0.005 A t 1 0.005 30 X
Distance setting 0.10 B normal 2.0 0.2 100 O
Aperture Area 0.125 B normal 1 0.125 100 O
Non-linearity 0.010 B normal 1 0.10 100 O
Combined standard unce
rtainty (%)
-- -- normal -- 1.10 431 --
Table 4-75. NMIA uncertainty budget of averaged LED intensity measurement for white LEDs
(W).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Axis alignment, angular 0.08 B normal 1 0.08 100 X
Axis alignment,
translational
0.08 B normal 1 0.08 100 X
Current feeding accuracy 0.010 B normal 0.95 0.095 30 O
Stray light 0.46 B rectangular 1 0.46 100 O
Spectral mismatch
correction
0.43 B rectangular 1 0.43 100 O
APMP.PR-S3a Averaged LED Intensity Final Report
98
Calibration of photometer 0.20 B normal 1 0.2 100 O
Reading repeatability 0.0026 A t 1 0.0026 30 X
Distance setting 0.10 B normal 2.0 0.2 100 O
Aperture Area 0.125 B normal 1 0.125 100 O
Non-linearity 0.010 B normal 1 0.10 100 O
Combined standard unce
rtainty (%)
-- -- normal -- 0.71 308 --
Table 4-76. NMIA uncertainty budget of averaged LED intensity measurement for diffuser-
type green LEDs (D).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Axis alignment, angular 0.08 B normal 1 0.08 100 X
Axis alignment,
translational
0.08 B normal 1 0.08 100 X
Current feeding accuracy 0.010 B normal 0.74 0.007 30 O
Stray light 0.0 B rectangular 1 0.0 100 O
Spectral mismatch
correction
0.43 B rectangular 1 0.43 100 O
Calibration of photometer 0.20 B normal 1 0.2 100 O
Reading repeatability 0.0038 A t 1 0.0038 30 X
Distance setting 0.10 B normal 2.0 0.2 100 O
Aperture Area 0.125 B normal 1 0.125 100 O
Non-linearity 0.010 B normal 1 0.10 100 O
Combined standard unce
rtainty (%)
-- -- normal -- 0.55 229 --
Table 4-77. NMIA uncertainty budget of junction voltage measurement.
APMP.PR-S3a Averaged LED Intensity Final Report
99
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Calibration of voltmeter 0.001 B normal 1 0.001 100 O
Junction position
dependence
0.0035 B rectangular 1 0.0035 100 X
Reproducibility 0.0001 A normal 1 0.0001 30 X
Combined standard unce
rtainty (%)
-- -- normal -- 0.0036 116 --
4.12. NIST
4.12.1. Measurement setup
The scale of Averaged LED Intensity at NIST is maintained on two non-diffuser type V(λ)-
corrected, silicon photodiode photometers having 100 mm2 circular apertures. The LED
photometers were calibrated at the NIST tunable-laser-based facility for Spectral
Irradiance and Radiance Responsivity Calibrations using Uniform Sources (SIRCUS)
described in Reference11. The LED photometers were calibrated for spectral irradiance
responsivity at distances of 100 mm and 316 mm using a sphere source that had a 5 mm
aperture. The spectral irradiance responsivity and the emitted LED spectrum measured in
the comparison APMP-S3c were used to calculate the illuminance responsivity of the LED
photometers.
The test LED was operated on DC power at a constant current of 20 mA using a
four-wire connection. The wiring diagram for this measurement is shown in Fig. 4-46. The
operating current of the LED was measured with an 8.5 digit multimeter. The test LED
was measured after it was powered on for 10 minutes. The output signal of the LED
photometer was simultaneously recorded with the LED current, LED voltage, LED ambient
temperature, room temperature, and room humidity. Each LED was measured for a total
of three lightings to check its reproducibility. The mean value of the three measurements
was reported, and the variation was included in the uncertainty budget of the
measurement. More details of the measurement facility and procedures are described in
11 Brown, S.W., Eppeldauer, G.P., and Lykke, K.R., NIST facility for Spectral Irradiance and Radiance Responsivity Calibrations with Uniform Sources, Metrologia 37, 579-582. (2000)
APMP.PR-S3a Averaged LED Intensity Final Report
100
Reference12.
Fig. 4-46. Wiring diagram for measurement of a test LED in NIST.
4.12.2. Mounting and alignment
The LEDs were measured on the NIST 4 m photometry bench described in Reference13.
The two LED photometers were mounted on the rotation wheel with respect to the
reference plane of the carriage. A telescope was fixed on the side of the photometry
bench which imaged the front edge of the photometer which was 4.5 mm away from the
reference place of the photometers. The photometer carriage was moved 95.5 mm away
from the telescope reference plane along the rail system and locked in the position. The
front section of the photometer carriage was separated from the wheel. The LED was
mounted in the holder on the front section as shown in Fig. 4-47. By examining the LED
from the side through the telescope, the tip of the LED was translated to the point in
space, set parallel to the detector axis, and adjusted vertically as shown in Fig. 4-48. The
LED is then rotated 90 degrees on the horizontal plane and adjusted to remain in the
horizontal plane. This iterative process was continued until the LED was aligned with the
optical axis when completely rotated.
12 Miller C. C., and Ohno Y., Luminous Intensity Measurement of LEDs at NIST, in Proc. of 2nd CIE Expert Symposium on LED Measurement, 28-32. (2001) 13 Ohno Y. NIST Special Publication 250-37, Photometric Calibration. (1997)
APMP.PR-S3a Averaged LED Intensity Final Report
101
Fig. 4-47. LED holder and photometer wheel on the NIST photometry bench.
Fig. 4-48. View in the telescope showing the LED tip aligned to the right position and the LED
mechanical axis aligned with the optical axis of the photometry bench.
4.12.3. Traceability
The two LED photometers used to measure the illuminance of the LEDs at the specified
distances were calibrated for spectral irradiance responsivity in the NIST tuneable-laser-
based SIRCUS facility14. The calibration was done by direct comparison of the photometer
with two of the NIST trap detectors, which maintain the NIST spectral irradiance scale
and are periodically calibrated against the NIST Reference Cryogenic Radiometer -
Primary Optical Watt Radiometer (POWR).
4.12.4. Measurement uncertainty
The uncertainty budgets for measurement of Averaged LED Intensity of the red, green,
blue, white, and diffuser-type green LEDs are shown in the tables below, and the
uncertainty budget for measurement of junction voltage of the test LEDs is shown in
14 Brown, S.W., Eppeldauer, G.P., and Lykke, K.R., NIST facility for Spectral Irradiance and Radiance Responsivity Calibrations with Uniform Sources, Metrologia 37, 579-582. (2000)
APMP.PR-S3a Averaged LED Intensity Final Report
102
Table 4-83. The NIST policy on uncertainty statements is described in Reference15.
Table 4-78. NIST uncertainty budget of averaged LED intensity measurement for red LEDs
(R).
Table 4-79. NIST uncertainty budget of averaged LED intensity measurement for green LEDs
(G).
15 B. N. Taylor, and C. E. Kuyatt, Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, NIST Technical Note 1297. (1993)
APMP.PR-S3a Averaged LED Intensity Final Report
103
Table 4-80. NIST uncertainty budget of averaged LED intensity measurement for blue LEDs
(B).
APMP.PR-S3a Averaged LED Intensity Final Report
104
Table 4-81. NIST uncertainty budget of averaged LED intensity measurement for white LEDs
(W).
Table 4-82. NIST uncertainty budget of averaged LED intensity measurement for diffuser-type
green LEDs (D).
APMP.PR-S3a Averaged LED Intensity Final Report
105
Table 4-83. NIST uncertainty budget of junction voltage measurement (typical).
4.13. VNIIOFI
Not submitted.
4.14. MKEH
4.14.1. Measurement setup
The measurements were made on a photometer bench with the help of our standard
LED photometer (f1’=1.39; entrance aperture 1 cm2), Keithley 6485 electrometer,
alignment lasers, current generator for the LED (type adret 103), a 5 freedom LED holder
(two rotation + 3 translation) and an alignment system.
The photometer calibration is based on the spectral responsivity scale of MKEH.
Each LED spectral distribution was measured with the help of a spectral irradiance
comparator with 10 nW resolution in 1 nm steps. The photometer spectral responsivity
was measured in 1 nm steps as well.
Knowing the photometer responsivity at 555 nm, the entrance aperture, the
calculated mismatch correction factor for each LED, the measured photocurrent and the
APMP.PR-S3a Averaged LED Intensity Final Report
106
distance we simply calculated the cd value for each LED.
The junction voltage was measured with 4 wire method with a Keithley 2000
multimeter. The junction voltage was measured for 6 digits. The junction voltage drifted
and its average value was different at each relighting of the LED. Compared to this
uncertainty all other parameter is negligible. We cannot give uncertainty about the
contact potential. We used the same type of clamp for both pole.
The LEDs were powered with a current generator (Type: adret 103). The current
generator was calibrated before the measurements at the Electricity Laboratory with an
uncertainty of 2*10-5.
4.14.2. Mounting and alignment
We have used an adjustment system for LED-s capable for 3 axis translation, pitch and
rotation. We have used a laser which was centred and perpendicular to the detector and
tried to centre the LED and align it’s axis to the laser. First we tried a camera as it was
mentioned but we were not happy with the results. Therefore we tried to use a direct
visual method for the alignment. We found it better. The statistical uncertainty of the
alignment of the different LEDs was given in my uncertainty budget in % of measured cd.
4.14.3. Traceability
All measurements are traceable to MKEH spectral responsivity and spectral irradiance
scale. The MKEH spectral irradiance scale is traceable to the NIST scale.
4.14.4. Measurement uncertainty
Tables in the following show the detailed uncertainty budgets of the CIE B averaged
luminous intensity measurement for the LEDs used in this APMP LED comparison.
The uncertainty budget of the measurements is similar than any other candela
realization error budget. We think it speaks for itself. The only difference, that in this case
the whole error budget was dominated by the alignment errors.
Two persons repeated the alignment 3-5 times for each diode and calculated the
cd value. The calculated relative standard deviation for each LEDs gives the standard
uncertainty of the alignment. This value includes the distance alignment; the centering
and the axis alignment together. (We do not think that it can be measured separately.)
The measured standard uncertainty of the alignment for each diode is given in the
following:
LED relative
APMP.PR-S3a Averaged LED Intensity Final Report
107
standard uncertainty
R1 0,53%
R2 0,34%
R3
G1 0,44%
G2
G3 0,21%
B1 0,71%
B2 0,49%
B3 0,68%
W1 0,20%
W2 0,35%
W3 0,24%
D1 0,18%
D2 0,24%
These uncertainties are random and give the uncorrelated statistical uncertainty of the
diode alignment. There is other uncertainty component concerning to the distance
uncertainty.
Table 4-84. MKEH uncertainty budget of averaged LED intensity measurement for red LEDs
(R).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Photometer S555 calibration
accuracy
B rectangular 1 0.30 ∞ O
Spectral mismatch
correction
B rectangular 1 0.22 ∞ X
Photometer aperture area B rectangular 1 0.05 ∞ O
LED alignment
(angular+centering+distanc
e)
A normal 1 0.34 ~
0.53
∞ O
LED distance uncertainty B rectangular 1 0.20 X
Combined standard unce
rtainty (%)
-- -- normal -- 0.55-
0.68
∞ --
Table 4-85. MKEH uncertainty budget of averaged LED intensity measurement for green
LEDs (G).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
APMP.PR-S3a Averaged LED Intensity Final Report
108
Photometer S555 calibration
accuracy
B rectangular 1 0.30 ∞ O
Spectral mismatch
correction
B rectangular 1 0.15 ∞ X
Photometer aperture area B rectangular 1 0.05 ∞ O
LED alignment
(angular+centering+distanc
e)
A normal 1 0.21 ~
0.44
∞ O
LED distance uncertainty B rectangular 1 0.20 X
Combined standard unce
rtainty (%)
-- -- normal -- 0.45-
0.59
∞ --
Table 4-86. MKEH uncertainty budget of averaged LED intensity measurement for blue LEDs
(B).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Photometer S555 calibration
accuracy
B rectangular 1 0.30 ∞ O
Spectral mismatch
correction
B rectangular 1 0.30 ∞ X
Photometer aperture area B rectangular 1 0.05 ∞ O
LED alignment
(angular+centering+distanc
e)
A normal 1 0.49 ~
0.71
∞ O
LED distance uncertainty B rectangular 1 0.20 X
Combined standard unce
rtainty (%)
-- -- normal -- 0,68-
0,85
∞ --
Table 4-87. MKEH uncertainty budget of averaged LED intensity measurement for white
LEDs (W).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Photometer S555 calibration
accuracy
B rectangular 1 0.30 ∞ O
Spectral mismatch
correction
B rectangular 1 0,20 ∞ X
Photometer aperture area B rectangular 1 0.05 ∞ O
APMP.PR-S3a Averaged LED Intensity Final Report
109
LED alignment
(angular+centering+distanc
e)
A normal 1 0.20 ~
0.35
∞ O
LED distance uncertainty B rectangular 1 0.20 X
Combined standard unce
rtainty (%)
-- -- normal -- 0.47-
0.55
∞ --
Table 4-88. MKEH uncertainty budget of averaged LED intensity measurement for diffuser-
type green LEDs (D).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Photometer S555 calibration
accuracy
B rectangular 1 0.30 ∞ O
Spectral mismatch
correction
B rectangular 1 0.20 ∞ X
Photometer aperture area B rectangular 1 0.05 ∞ O
LED alignment
(angular+centering+distanc
e)
A normal 1 0.18 ~
0.24
3-6 O
LED distance uncertainty B rectangular 1 0.20 X
Combined standard unce
rtainty (%)
-- -- normal -- 0.46-
0.48
∞ --
Table 4-89 is the detailed uncertainty budget of the junction voltage measurement.
Table 4-89. MKEH uncertainty budget of junction voltage measurement (typical).
Uncertainty Component Standard u
ncertainty
(%)
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Calibration of voltmeter 0.0003 B normal 1 0.0003 ∞ O
Junction position
dependence
N.A. B rectangular 1 N.A. ∞
Reproducibility 0.01-0.03 A normal 1 0.01-
0.03
5 X
Combined standard unce
rtainty (%)
-- -- normal -- 0.01-
0.03
--
APMP.PR-S3a Averaged LED Intensity Final Report
110
4.15. INM
4.15.1. Measurement setup
At INM-Ro the measurement set-up closely followed the CIE Technical Report 127:1997
recommendation. The measurement set up (Fig. 4-49) was mounted on a prismatic rail
providing axial positioning.
Fig. 4-49. Setup for average luminous intensity measurements in INM Romania.
A four wire technique as described in the APMP-PR-S3a comparison protocol was
used in order to (almost) simultaneously measure the current fed into the measured LED
and the junction voltage. The LED current was generated by a finely tuned voltage
stabilised supply and a current measurement shunt across which the voltage was
measured with a digital voltmeter. The LEDs junction voltage and was measured with a
similar digital voltmeter.
During the measurements, the photocurrent generated by the photometric head
was fed into Current to Voltage converter with a transimpedance factor of 1E6 V/A. The
output voltage was measured with a third digital voltmeter.
The INM photometer was equipped with a Hamamatsu S 1337-1010BQ which
window was replaced with an IR filter. A small integrating sphere of about 50 mm dia.
APMP.PR-S3a Averaged LED Intensity Final Report
111
was mounted in front of the filtered photodiode. A screen was mounted inside of the
sphere in order to avoid direct irradiance. This sphere was provided with a precision
circular aperture (Fig. 4-49). The small sphere inner surface and the inner diffuser were
covered with a thick sprayed BaSO4 coating (about 25 sprayed layers, the last 4 without
binder).
The spectral densities of the standard lamp and of the LED under calibration were
measured with a fibre optic input spectrometer. The measurement of the spectral density
of the emitted flux was performed with a CCD spectrometer providing a (1 ± 0.1) nm
bandwidth. The spectrometer input fibre head was provided with a diffusing IR filter.
4.15.2. Mounting and alignment
The measured LED was mounted in a cylindrical hole perpendicular on a black slab itself
attached to a cinematic mount. This arrangement provided adjustment with six degrees
of freedom (Fig. 4-49).
Prior to the LED mounting and measurement, a laser diode was mounted on the
prismatic rail instead of the photometric head. First, it was used to align the hole to the
measurement axis. Next, a small mirror was flushed to the black slab which position was
finely adjusted in order to reach the perpendicularity of the slab surface to the optical
axis of the rail. After adjusting the slab perpendicularity to the measurement axis, the
LED was mounted in the black cylindrical hole so that only it’s front part was visible (Fig.
4-49). The tip of the LED under calibration was brought in the same plane as the slab
surface so that the LED tip to the photometer precision aperture plane distance could be
adjusted using a calliper.
4.15.3. Traceability
The photometer as a whole (including the photometric head, the current to voltage
converter and the associated multimeter) spectral responsivity was characterised against
an INM-RO spectral responsivity reference traceable to the LNE-INM primary reference
(cryogenic radiometer).
The spectrometer wavelength scale was calibrated against low pressure spectral
Hg, Cd and He lamps traceable to the INM reference for length measurements (stabilised
He-Ne laser). For all wavelengths within the visible range it was found to be accurate
within ±0.3 nm.
The spectrometer irradiance scale was calibrated against a irradiance spectral
density lamp, traceable to the MIKES–TKK reference. The spectrometer photometric
linearity was calibrated and further checked against a set of spectral transmittance filters
APMP.PR-S3a Averaged LED Intensity Final Report
112
(neutral glass of NG type), traceable to the INM reference spectrophotometer.
All voltage measurements were traceable to the national references of Romania
(group of stabilised Zener diodes of Fluke 732 B). The shunt resistance used to generate
the feeding current was calibrated with traceability to the national references (group of
electrical resistors).
All dimensional measurements (distance and the diameter of the photometer
aperture) are traceable to the INM-RO national reference (stabilised He-Ne laser).
The temperature was measured with a digital thermometer calibrated with traceability to
the INM maintained SIT90 fixed points.
4.15.4. Measurement uncertainty
The expression of the LED average luminous intensity, avI , is:
)1(max.
2
54321 sp
ph
ph
av CKAs
IdCCCCCI
where: 1C is the feeding current factor; 2C is the ambient temperature correction
factor; 3C is the stray light coefficient factor; 4C is the tilting correction factor; 5C is
the centring correction factor; max.phs is the photometer maximum spectral responsivity;
d is the LED to the photometer aperture distance (Fig. 4-49); phI is the generated by
the pho-current; A is the photometer measurement aperture area; )(V is the
relative responsivity of the CIE standard observer; K is the luminous efficacy constant
(683 lm/W);
spC is the spectral correction factor:
)2(
)()(
)()(
830
380
.,
830
380
,
dsS
dVS
C
relphrled
rled
sp
where: )(. relphs is the photometer relative spectral responsivity; )(, rledS is the LED
relative spectral density and )(V is the relative efficacy of the CIE standard observer.
Tables in the following are the detailed uncertainty budgets of the CIE B averaged
luminous intensity measurement for the LEDs used in this APMP LED comparison.
Table 4-90. INM uncertainty budget of averaged LED intensity measurement for red LEDs (R).
APMP.PR-S3a Averaged LED Intensity Final Report
113
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Feeding current factor 1C 0.001 B normal
avI 0.1 ∞ O
Ambient temperature
correction factor 2C
0.001 B rectangular avI 0.1 ∞ X
Stray light coefficiency
factor 3C
0.010 B rectangular avI 1.0 ∞ O
Tilting correction factor
4C
0.020 B rectangular avI 2.0 ∞ X
Centering correction factor
5C
0.005 B rectangular avI 0.5 ∞ X
Potometer maximum
spectral responsivity
max.phs
0.14
mA/W
B normal max./ phav sI
1.0 ∞ O
Photocurrent reading phI 0.01
phI B normal phav II /
1.0 ∞ O
Distance setting d 0.10 mm B rectangular dI av /2 0.1 ∞ O
Photometer aperture area
A
0.30 mm2 B normal AIav /
0.3 ∞ O
Spectral correction factor
spC
0.05 spC B normal avI 5.0 ∞ O
Repeatability 0.001avI A normal
avI 0.1 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 5.4 ∞ --
Table 4-91. INM uncertainty budget of averaged LED intensity measurement for green LEDs
(G).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Feeding current factor 1C 0.001 B normal
avI 0.1 ∞ O
Ambient temperature
correction factor 2C
0.001 B rectangular avI 0.1 ∞ X
Stray light coefficiency
factor 3C
0.010 B rectangular avI 1.0 ∞ O
Tilting correction factor
4C
0.020 B rectangular avI 2.0 ∞ X
APMP.PR-S3a Averaged LED Intensity Final Report
114
Centering correction factor
5C
0.005 B rectangular avI 0.5 ∞ X
Potometer maximum
spectral responsivity
max.phs
0.14
mA/W
B normal max./ phav sI
1.0 ∞ O
Photocurrent reading phI 0.01
phI B normal phav II /
1.0 ∞ O
Distance setting d 0.10 mm B rectangular dI av /2 0.1 ∞ O
Photometer aperture area
A
0.30 mm2 B normal AIav /
0.3 ∞ O
Spectral correction factor
spC
0.05 spC B normal avI 4,5 ∞ O
Repeatability 0.001avI A normal
avI 0.1 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 4.8 ∞ --
Table 4-92. INM uncertainty budget of averaged LED intensity measurement for blue LEDs
(B).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Feeding current factor 1C 0.001 B normal
avI 0.1 ∞ O
Ambient temperature
correction factor 2C
0.001 B rectangular avI 0.1 ∞ X
Stray light coefficiency
factor 3C
0.010 B rectangular avI 1.0 ∞ O
Tilting correction factor
4C
0.020 B rectangular avI 2.0 ∞ X
Centering correction factor
5C
0.005 B rectangular avI 0.5 ∞ X
Potometer maximum
spectral responsivity
max.phs
0.14
mA/W
B normal max./ phav sI
1.0 ∞ O
Photocurrent reading phI 0.01
phI B normal phav II /
1.0 ∞ O
Distance setting d 0.10 mm B rectangular dI av /2 0.1 ∞ O
Photometer aperture area
A
0.30 mm2 B normal AIav /
0.3 ∞ O
Spectral correction factor
spC
0.05 spC B normal avI 5.0 ∞ O
APMP.PR-S3a Averaged LED Intensity Final Report
115
Repeatability 0.001avI A normal
avI 0.1 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 5.4 ∞ --
Table 4-93. INM uncertainty budget of averaged LED intensity measurement for white LEDs
(W).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Feeding current factor 1C 0.001 B normal
avI 0.1 ∞ O
Ambient temperature
correction factor 2C
0.001 B rectangular avI 0.1 ∞ X
Stray light coefficiency
factor 3C
0.010 B rectangular avI 1.0 ∞ O
Tilting correction factor
4C
0.020 B rectangular avI 2.0 ∞ X
Centering correction factor
5C
0.005 B rectangular avI 0.5 ∞ X
Potometer maximum
spectral responsivity
max.phs
0.14
mA/W
B normal max./ phav sI
1.0 ∞ O
Photocurrent reading phI 0.01
phI B normal phav II /
1.0 ∞ O
Distance setting d 0.10 mm B rectangular dI av /2 0.1 ∞ O
Photometer aperture area
A
0.30 mm2 B normal AIav /
0.3 ∞ O
Spectral correction factor
spC
0.05 spC B normal avI 5.3 ∞ O
Repeatability 0.001avI A normal
avI 0.1 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 5.7 ∞ --
Table 4-94. INM uncertainty budget of averaged LED intensity measurement for diffuser-type
green LEDs (D).
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distributio
n
Sensitivity co
efficient
Contrib
ution
(%)
Deg. of
freedo
m
Correl
ated?
Feeding current factor 1C 0.001 B normal
avI 0.1 ∞ O
APMP.PR-S3a Averaged LED Intensity Final Report
116
Ambient temperature
correction factor 2C
0.001 B rectangular avI 0.1 ∞ X
Stray light coefficiency
factor 3C
0.010 B rectangular avI 1.0 ∞ O
Tilting correction factor
4C
0.020 B rectangular avI 2.0 ∞ X
Centering correction factor
5C
0.005 B rectangular avI 0.5 ∞ X
Potometer maximum
spectral responsivity
max.phs
0.14
mA/W
B normal max./ phav sI
1.0 ∞ O
Photocurrent reading phI 0.01
phI B normal phav II /
1.0 ∞ O
Distance setting d 0.10 mm B rectangular dI av /2 0.1 ∞ O
Photometer aperture area
A
0.30 mm2 B normal AIav /
0.3 ∞ O
Spectral correction factor
spC
0.05 spC B normal avI 4.5 ∞ O
Repeatability 0.001avI A normal
avI 0.1 ∞ X
Combined standard unce
rtainty (%)
-- -- normal -- 4.8 ∞ --
The junction voltage expression is:
readj VCCV 21
readV : the mean reading ; 1C : temperature factor and
2C : position factor
Table 4-95 is the detailed uncertainty budget of the junction voltage
measurement.
Table 4-95. INM uncertainty budget of junction voltage measurement.
Uncertainty Component Standard u
ncertainty
Ty
pe
Probability
distribution
Sensitivity
coefficient
Contribut
ion (%)
Deg.
of fre
edom
Correl
ated?
Mean reading readV 2E-5 V B normal 1 0.02 ∞ O
Temperature factor 1C 0.0010 B rectangular readV
0.10 ∞ X
Position factor 2C 0.0005 B rectangular readV
0.05 ∞ X
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Repeatability 0.0005 jV
A normal 1 0.05 ∞ X
Combined standard unce
rtainty (%
-- -- normal -- 0.13 ∞ --
APMP.PR-S3a Averaged LED Intensity Final Report
118
5. Reported Results of Participants
In this chapter, the results of the comparison S3a are presented, which are reported by
each participant as the final version, i.e., after the verification in the pre-draft A process.
We note that, throughout this report document, the uncertainty values with a symbol U
indicate the expanded uncertainties for a confidence level of 95 % normally with a
coverage factor of k = 2, while the values with a symbol u indicate the standard
uncertainties.
5.1. KRISS
As the pilot laboratory of the comparison, KRISS measured each LED at most three times:
the first measurement before sending the LEDs for the first round, the second after
receiving the LEDs from the first round, and the third after receiving the LEDs from the
second round. The final control measurement of the first round is also regarded as the
initial control measurement of the second round. Note that the artefact sets #4 and #8
are circulated only one round. The repeated measurements provide information on the
stability of the artefact LEDs, which will be discussed in Section 6.2.
Table 5-1 sumarizes the measurement results of KRISS of all the artefact LEDs. The
uncertainty values are not explicitly shown in this table but refered to the budgets in
Table 4-1 ~ Table 4-6. The laboratory conditions are kept at a temperature of (25 ± 2) ºC
and a relative humidity of (45 ± 15) %. The burning time of each measurement was 20
minutes in average.
Table 5-1. Measurement results of KRISS.
artifact
set LED
1. measurement 2. measurement 3. measurement
ILED (cd) Vj (V) ILED (cd) Vj (V) ILED (cd) Vj (V)
#1
R-1 0.7067 1.8846 0.7111 1.8870 0.7107 1.8856
R-2 0.6954 1.8881 0.7025 1.8918 0.6999 1.8889
R-3 0.6967 1.9212 0.7030 1.9245 0.7039 1.9217
G-1 2.6916 3.2972 2.6834 3.3016 2.6964 3.2964
G-2 2.5223 3.4378 2.5127 3.4424 2.5178 3.4350
G-3 2.6824 3.3151 2.6904 3.3201 2.6687 3.3139
B-1 0.8124 3.3764 0.8032 3.3791 0.8051 3.3744
B-2 0.8394 3.3773 0.8310 3.3830 0.8197 3.3758
B-3 0.8476 3.3469 0.8456 3.3522 0.8438 3.3438
W-1 0.6423 3.4455 0.6872 3.4474 0.6822 3.4399
W-2 0.6356 3.4651 0.6323 3.4664 0.6224 3.4569
W-3 0.7009 3.4194 0.6992 3.4203 0.6863 3.4109
D-1 0.0848 3.4759 0.0844 3.4767 0.0837 3.4709
D-2 0.0904 3.3135 0.0902 3.3154 0.0900 3.3117
APMP.PR-S3a Averaged LED Intensity Final Report
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#2
R-1 0.6795 1.8888 0.6856 1.8870 0.6944 1.8946
R-2 0.6855 1.8979 0.6905 1.8961 0.6981 1.9043
R-3 0.6996 1.9017 0.7083 1.9001 0.7143 1.9086
G-1 2.4467 3.4765 2.5733 3.4854 2.5856 3.4822
G-2 2.5335 3.3957 2.5322 3.4032 2.5485 3.4003
G-3 2.7702 3.3058 2.7863 3.3126 2.8055 3.3105
B-1 0.7669 3.4556 0.7560 3.4626 0.7630 3.4587
B-2 0.8380 3.3734 0.8306 3.3832 0.8344 3.3805
B-3 0.7736 3.3550 0.7698 3.3621 0.7741 3.3600
W-1 0.6715 3.3047 0.6786 3.3103 0.6753 3.3066
W-2 0.6863 3.4235 0.6875 3.4297 0.6857 3.4235
W-3 0.6173 3.4515 0.6183 3.4602 0.6147 3.4590
D-1 0.0892 3.4018 0.0890 3.4010 0.0880 3.3981
D-2 0.0743 3.4890 0.0738 3.4889 0.0733 3.4864
#3
R-1 0.7154 1.8955 0.6983 1.8908 0.7026 1.8894
R-2 0.7383 1.9004 0.7190 1.8941 0.7200 1.8930
R-3 0.7344 1.9046 0.7146 1.8987 0.7178 1.8976
G-1 2.7833 3.5277 2.7444 3.5122 2.7466 3.5093
G-2 2.5187 3.3920 2.5048 3.3793 2.4973 3.3759
G-3 2.4658 3.3525 2.4366 3.3396 2.4403 3.3365
B-1 0.8172 3.4479 0.8120 3.4359 0.8068 3.4336
B-2 0.8755 3.4351 0.8604 3.4234 0.8602 3.4212
B-3 0.7054 3.5334 0.6980 3.5183 0.6938 3.5159
W-1 0.6831 3.4552 0.6711 3.4410 0.6697 3.4407
W-2 0.6695 3.3567 0.6572 3.3427 0.6538 3.3428
W-3 0.6931 3.3237 0.6827 3.3116 0.6807 3.3103
D-1 0.0857 3.3294 0.0849 3.3176 0.0844 3.3173
D-2 0.0964 3.3298 0.0956 3.3190 0.0951 3.3184
#4
R-1 0.7335 1.9010 0.7229 1.8976
R-2 0.6829 1.8970 0.6746 1.8942
R-3 0.7061 1.8983 0.6979 1.8958
G-1 2.6564 3.5243 2.6238 3.5168
G-2 2.8201 3.3081 2.7930 3.3031
G-3 2.6927 3.3694 2.6636 3.3629
B-1 0.9329 3.4312 0.9182 3.4265
B-2 0.8038 3.4739 0.7942 3.4689
B-3 0.8905 3.4108 0.8769 3.4057
W-1 0.7076 3.4498 0.6897 3.4397
W-2 0.6977 3.3500 0.6846 3.3435
W-3 0.7112 3.4569 0.6991 3.4509
D-1 0.0636 3.3117 0.0631 3.3028
D-2 0.0887 3.4146 0.0879 3.4050
#5
R-1 0.6939 1.9190 0.6977 1.9189 0.6966 1.9193
R-2 0.7185 1.9230 0.7190 1.9229 0.7205 1.9238
R-3 0.6691 1.8858 0.6745 1.8864 0.6757 1.8866
G-1 2.6549 3.3126 2.6840 3.3131 2.6498 3.3141
G-2 2.4914 3.4478 2.4800 3.4494 2.4426 3.4509
G-3 2.5619 3.3808 2.5746 3.3829 2.5854 3.3843
B-1 0.7896 3.4134 0.8006 3.4155 0.7948 3.4140
B-2 0.8971 3.4154 0.9120 3.4175 0.9085 3.4160
APMP.PR-S3a Averaged LED Intensity Final Report
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B-3 0.9084 3.4279 0.9145 3.4307 0.9085 3.4334
W-1 0.6718 3.3232 0.6699 3.3180 0.6655 3.3152
W-2 0.7006 3.4495 0.7018 3.4458 0.6975 3.4417
W-3 0.6810 3.4551 0.6822 3.4530 0.6804 3.4546
D-1 0.0653 3.4818 0.0653 3.4939 0.0645 3.4959
D-2 0.0620 3.4911 0.0621 3.5051 0.0616 3.5046
#6
R-1 0.7000 1.8992 0.7136 1.9024 0.7108 1.9017
R-2 0.6563 1.8856 0.6635 1.8888 damaged
R-3 0.7023 1.8954 0.7144 1.8985 damaged
G-1 2.8398 3.2992 2.8575 3.3039 damaged
G-2 2.7226 3.3015 2.7450 3.3067 damaged
G-3 2.4871 3.3214 2.4902 3.3283 2.4712 3.3257
B-1 0.9185 3.4189 0.9231 3.4258 0.9130 3.4232
B-2 0.8098 3.3772 0.8125 3.3840 0.8037 3.3821
B-3 0.8244 3.3829 0.8236 3.3902 damaged
W-1 0.6933 3.4079 0.6739 3.4122 0.6714 3.4120
W-2 0.6828 3.4052 0.6709 3.4105 0.6651 3.4098
W-3 0.7091 3.4214 0.7016 3.4269 0.6949 3.4253
D-1 0.0935 3.3568 0.0937 3.3672 0.0933 3.3681
D-2 0.0706 3.4505 0.0707 3.4617 damaged
#7
R-1 0.6807 1.9220 0.6852 1.9209 0.6656 1.9179
R-2 0.7452 1.9040 0.7481 1.9033 0.7323 1.9000
R-3 0.6825 1.9200 0.6859 1.9198 0.6743 1.9167
G-1 2.7469 3.2989 2.7600 3.2980 2.7171 3.2912
G-2 2.6392 3.3643 2.6432 3.3626 2.6188 3.3549
G-3 2.8487 3.3041 2.8590 3.3021 2.8165 3.2955
B-1 0.8634 3.4653 0.8619 3.4638 0.8221 3.4545
B-2 0.8611 3.3991 0.8635 3.3972 0.8425 3.3888
B-3 0.8316 3.4295 0.8390 3.4271 0.8138 3.4187
W-1 0.6735 3.4753 0.6723 3.4746 0.6616 3.4608
W-2 0.6323 3.3643 0.6321 3.3620 0.6242 3.3521
W-3 0.6261 3.4177 0.6268 3.4145 0.6174 3.4045
D-1 0.0747 3.4555 0.0745 3.4500 0.0741 3.4435
D-2 0.0841 3.3811 0.0833 3.3766 0.0828 3.3721
#8
R-1 0.6941 1.8900 0.6945 1.8890
R-2 0.6875 1.8940 0.6850 1.8932
R-3 0.7175 1.8988 0.7180 1.8981
G-1 2.6454 3.5389 2.6504 3.5359
G-2 2.6749 3.2960 2.6693 3.2943
G-3 2.6376 3.2981 2.6278 3.2956
B-1 0.8573 3.4506 0.8567 3.4483
B-2 0.8583 3.3670 0.8621 3.3646
B-3 0.8428 3.4687 0.8433 3.4670
W-1 0.6586 3.4304 0.6569 3.4275
W-2 0.5997 3.4313 0.5965 3.4277
W-3 0.6224 3.4662 0.6195 3.4629
D-1 0.0871 3.3190 0.0867 3.3162
D-2 0.0913 3.3068 0.0912 3.3053
APMP.PR-S3a Averaged LED Intensity Final Report
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5.2. MIKES
MIKES of Finland measured the artifact set #1 in its first round from 07 April 2008 to 13
April 2008. The laboratory conditions are reported as temperature of (21.5 ± 1.0) ºC and
relative humidity of (31 ± 5) %. Table 5-2 shows the reported results of MIKES.
Table 5-2. Measurement results of MIKES.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#1
R-1 0.729 0.025 1.89426 0.00012 50
R-2 0.724 0.025 1.89866 0.00011 25
R-3 0.721 0.025 1.93310 0.00027 50
G-1 2.753 0.100 3.31595 0.00033 30
G-2 2.576 0.093 3.45713 0.00060 35
G-3 2.731 0.099 3.33517 0.00068 35
B-1 0.827 0.029 3.39520 0.00044 40
B-2 0.847 0.030 3.40018 0.00058 30
B-3 0.865 0.030 3.37001 0.00043 30
W-1 0.709 0.025 3.46899 0.00075 55
W-2 0.658 0.023 3.48621 0.00036 40
W-3 0.725 0.025 3.44078 0.00039 55
D-1 0.0872 0.0012 3.49373 0.00027 60
D-2 0.0926 0.0013 3.32914 0.00024 60
5.3. CMS-ITRI
CMS-ITRI of Chinese Taipei measured the artifact set #2 in its first round from 26 May
2008 to 28 May 2008. The laboratory conditions are reported as temperature of (23.0 ±
1.5) ºC and relative humidity of (45 ± 10) %. During the measurement at CMS-ITRI,
however, all the three red LEDs were damaged so that the red LEDs of the set #2 had to
be completely replaced for the second round. On the agreement of the other
participants, CMS-ITRI repeated the measurement of the new red LEDs of the set #2 in
Sept. ~ Oct. 2009. Table 5-3 shows the reported results of CMS-ITRI.
Table 5-3. Measurement results of CMS-ITRI.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#2
R-1 0.700 0.027 1.899 0.003 35
R-2 0.699 0.027 1.908 0.002 35
R-3 0.716 0.028 1.912 0.003 35
G-1 2.581 0.099 3.499 0.013 35
G-2 2.565 0.098 3.417 0.010 35
G-3 2.79 0.11 3.327 0.009 35
B-1 0.748 0.030 3.476 0.009 35
APMP.PR-S3a Averaged LED Intensity Final Report
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B-2 0.826 0.034 3.397 0.010 35
B-3 0.762 0.031 3.373 0.009 35
W-1 0.685 0.027 3.324 0.004 35
W-2 0.695 0.027 3.444 0.005 35
W-3 0.625 0.024 3.475 0.007 35
D-1 0.090 0.004 3.406 0.005 35
D-2 0.075 0.003 3.495 0.005 35
5.4. PTB
PTB of Germany measured the artifact set #3 in its first round from 16 June to 2 July
2008. The laboratory conditions are reported as temperature of (25.0 ± 0.7) ºC and
relative humidity of (50 ± 10) %. Table 5-4 shows the reported results of PTB.
Table 5-4. Measurement results of PTB.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#3
R-1 0.7226 0.0144 1.8945 0.0007 590
R-2 0.7324 0.0146 1.8976 0.0007 446
R-3 0.7394 0.0147 1.9024 0.0007 426
G-1 2.8081 0.0378 3.5230 0.0026 560
G-2 2.5521 0.0344 3.3894 0.0025 278
G-3 2.4880 0.0335 3.3503 0.0025 399
B-1 0.8139 0.0186 3.4455 0.0017 574
B-2 0.8516 0.0195 3.4338 0.0017 213
B-3 0.7097 0.0162 3.5314 0.0017 410
W-1 0.6912 0.0088 3.4509 0.0025 495
W-2 0.6789 0.0086 3.3525 0.0025 495
W-3 0.7064 0.0090 3.3217 0.0024 395
D-1 0.0860 0.0011 3.3177 0.0017 93
D-2 0.0973 0.0013 3.3182 0.0017 292
5.5. NMIJ
NMIJ of Japan measured the artifact set #4 in its first round from 17 April 2008 to 22
June 2008. The laboratory conditions are reported as temperature of (23 ± 2) ºC and
relative humidity of (50 ± 30) %. Table 5-5 shows the reported results of NMIJ.
Table 5-5. Measurement results of NMIJ.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#4
R-1 0.718 0.017 1.8984 0.0064 123
R-2 0.674 0.016 1.8966 0.0023 116
R-3 0.698 0.016 1.8976 0.0014 117
G-1 2.727 0.068 3.5180 0.0049 119
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G-2 2.887 0.072 3.3045 0.0029 115
G-3 2.753 0.069 3.3644 0.0040 134
B-1 0.937 0.030 3.4275 0.0018 191
B-2 0.835 0.027 3.4713 0.0020 190
B-3 0.930 0.030 3.4075 0.0033 120
W-1 0.711 0.016 3.4424 0.0036 123
W-2 0.704 0.015 3.3478 0.0024 126
W-3 0.721 0.016 3.4544 0.0036 122
D-1 0.0652 0.0014 3.3021 0.0141 289
D-2 0.0909 0.0020 3.4051 0.0171 186
5.6. CENAM
CENAM of Mexico measured the artifact set #5 in its first round from 17 July 2008 to 21
July 2008. The laboratory conditions are reported as temperature of (22.7 ± 2.2) ºC and
relative humidity of (47.5 ± 8.0) %. Table 5-6 shows the reported results of CENAM.
Table 5-6. Measurement results of CENAM.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#5
R-1 0.4675 0.0248 1.9261 0.0010 56
R-2 0.4888 0.0278 1.9304 0.0008 48
R-3 0.4605 0.0263 1.8918 0.0006 45
G-1 2.3458 0.1702 3.3295 0.0013 47
G-2 2.2183 0.1480 3.4729 0.0020 51
G-3 2.3287 0.1423 3.4041 0.0014 46
B-1 0.7490 0.0429 3.4350 0.0014 48
B-2 0.8259 0.0508 3.4374 0.0012 47
B-3 0.8289 0.0512 3.4513 0.0013 52
W-1 0.5544 0.0315 3.3373 0.0013 59
W-2 0.5815 0.0345 3.4671 0.0011 47
W-3 0.5654 0.0306 3.4730 0.0018 45
D-1 0.0576 0.0037 3.5107 0.0016 51
D-2 0.0544 0.0037 3.5216 0.0013 54
5.7. LNE
LNE of France measured the artifact set #6 in its first round from 15 June 2008 to 13 July
2008. The laboratory conditions are reported as temperature of (22 ± 2) ºC and relative
humidity of (50 ± 10) %. Table 5-7 shows the reported results of LNE.
Table 5-7. Measurement results of LNE.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#6 R-1 0.745 0.015 1.90925 0.00057 120
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R-2 0.692 0.014 1.89535 0.00057 120
R-3 0.750 0.015 1.90543 0.00057 120
G-1 2.985 0.057 3.31209 0.00066 120
G-2 2.861 0.054 3.31284 0.00066 120
G-3 2.603 0.049 3.33553 0.00067 120
B-1 0.934 0.028 3.43531 0.00069 120
B-2 0.816 0.024 3.39327 0.00068 120
B-3 0.825 0.025 3.39927 0.00068 120
W-1 0.709 0.011 3.41940 0.00068 120
W-2 0.702 0.011 3.42046 0.00068 120
W-3 0.731 0.011 3.43496 0.00069 120
D-1 0.0987 0.0018 3.37456 0.00067 75
D-2 0.0746 0.0013 3.46610 0.00069 75
5.8. METAS
METAS of Switzerland measured the artifact set #7 in its first round from 08 Sept. 2008
to 17 Sept. 2008. The laboratory conditions are reported as temperature of (25.0 ± 0.5)
ºC and relative humidity of (43 ± 5) %. Table 5-8 shows the reported results of METAS.
Table 5-8. Measurement results of METAS.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#7
R-1 0.6902 0.0095 1.9340 0.0082 290
R-2 0.7577 0.0109 1.9145 0.0082 101
R-3 0.6904 0.0096 1.9328 0.0082 103
G-1 2.8012 0.0483 3.3136 0.063 119
G-2 2.6865 0.0439 3.3798 0.063 82
G-3 2.9087 0.0484 3.3176 0.063 162
B-1 0.8823 0.0287 3.4816 0.075 135
B-2 0.8901 0.0302 3.4282 0.075 96
B-3 0.8471 0.0289 3.4464 0.075 104
W-1 0.6862 0.0091 3.4934 0.083 183
W-2 0.6414 0.0087 3.3792 0.083 88
W-3 0.6359 0.0090 3.4322 0.083 100
D-1 0.07577 0.00140 3.4599 0.063 139
D-2 0.08483 0.00156 3.3877 0.063 176
5.9. NMC-A*STAR
NMC-A*STAR of Singapore measured the artifact set #8 in its first round from 10 July
2008 to 28 August 2008. The laboratory conditions are reported as temperature of (23 ±
2) ºC and relative humidity of (60 ± 10) %. Table 5-9 shows the reported results of NMC-
A*STAR.
APMP.PR-S3a Averaged LED Intensity Final Report
125
Table 5-9. Measurement results of NMC-A*STAR.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#8
R-1 0.713 0.016 1.8921 0.0022 76
R-2 0.702 0.015 1.8957 0.0022 57
R-3 0.735 0.016 1.9003 0.0022 54
G-1 2.678 0.051 3.5356 0.0024 60
G-2 2.701 0.051 3.2954 0.0024 59
G-3 2.648 0.050 3.2957 0.0024 45
B-1 0.865 0.019 3.4489 0.0025 65
B-2 0.873 0.019 3.3652 0.0025 44
B-3 0.856 0.019 3.4672 0.0025 45
W-1 0.666 0.012 3.4293 0.0041 65
W-2 0.604 0.011 3.4291 0.0041 58
W-3 0.627 0.011 3.4633 0.0041 52
D-1 0.0876 0.0018 3.3133 0.0021 43
D-2 0.0925 0.0018 3.3017 0.0021 57
5.10. VSL
VSL of the Netherlands measured the artifact set #1 in its second round from 13 October
2008 to 12 January 2009. The laboratory conditions are reported as temperature of (24.0
± 0.5) ºC and relative humidity of (45 ± 10) %. Table 5-10 shows the reported results of
VSL.
Table 5-10. Measurement results of VSL.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#1
R-1 0.728 0.011 1.8870 0.0031 115
R-2 0.711 0.012 1.8913 0.0031 108
R-3 0.717 0.010 1.9239 0.0031 166
G-1 2.746 0.049 3.2986 0.0056 353
G-2 2.586 0.039 3.4396 0.0059 462
G-3 2.745 0.057 3.3170 0.0054 358
B-1 0.814 0.012 3.3805 0.0055 146
B-2 0.833 0.012 3.3806 0.0058 143
B-3 0.852 0.016 3.3491 0.0055 310
W-1 0.698 0.008 3.4444 0.0057 135
W-2 0.644 0.013 3.4646 0.0059 133
W-3 0.712 0.018 3.4193 0.0059 176
D-1 0.0870 0.0014 3.4712 0.0056 38
D-2 0.0919 0.0025 3.3291 0.0115 90
APMP.PR-S3a Averaged LED Intensity Final Report
126
5.11. NMIA16
NMIA of Australia measured the artifact set #2 in its second round from January 2009 to
May 2009. However, as the red LEDs of this set is replaced in the previous round of CMS-
ITRI, the three red LEDs are measured by NMIA as the first round. The laboratory
conditions are reported as temperature of (21.0 ± 0.5) ºC and relative humidity of (50 ±
10) %. Table 5-11 shows the reported results of NMIA.
Table 5-11. Measurement results of NMIA.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#2
R-1 0.793 0.023 1.90209 0.00014 2350
R-2 0.800 0.012 1.91198 0.00014 430
R-3 0.806 0.016 1.91743 0.00014 75
G-1 2.600 0.050 3.52445 0.00025 70
G-2 2.540 0.050 3.43681 0.00025 75
G-3 2.456 0.040 3.34151 0.00025 1010
B-1 0.729 0.016 3.49167 0.00025 310
B-2 0.813 0.018 3.41229 0.00025 70
B-3 0.737 0.014 3.38591 0.00025 105
W-1 0.729 0.010 3.34000 0.00025 155
W-2 0.745 0.010 3.46348 0.00025 70
W-3 0.662 0.009 3.49266 0.00025 965
D-1 0.0906 0.0010 3.43581 0.00025 75
D-2 0.0754 0.0009 3.52608 0.00025 195
5.12. NIST
NIST of the USA measured the artifact set #3 in its second round from 18 February 2009
to 25 February 2009. The laboratory conditions are reported as temperature of 25 ºC and
relative humidity of 17 %. Table 5-12 shows the reported results of NIST.
Table 5-12. Measurement results of NIST.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#3
R-1 0.728 0.018 1.889 0.005 60
R-2 0.741 0.018 1.892 0.005 80
R-3 0.746 0.018 1.896 0.005 80
G-1 2.898 0.076 3.504 0.009 80
G-2 2.599 0.068 3.374 0.008 60
G-3 2.541 0.067 3.332 0.008 60
16 The final version of the results of NMIA is received on 01 July 2010 after the review of uncertainty budgets in the pre-draft A process.
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B-1 0.828 0.032 3.428 0.008 60
B-2 0.888 0.034 3.417 0.008 80
B-3 0.722 0.028 3.508 0.009 60
W-1 0.702 0.016 3.434 0.008 60
W-2 0.686 0.015 3.336 0.008 60
W-3 0.713 0.016 3.306 0.008 60
D-1 0.0898 0.0017 3.310 0.008 60
D-2 0.1007 0.0019 3.313 0.008 60
5.13. VNIIOFI
VNIIOFI of Russia measured the artifact set #5 in its second round from 28 November
2008 to 05 December 2008. The laboratory conditions are reported as temperature of
(22.0 ± 0.5) ºC and relative humidity of (62 ± 2) %. Table 5-13 shows the reported results
of VNIIOFI.
Table 5-13. Measurement results of VNIIOFI.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#5
R-1 0.7558 0.0027 1.933 0.001 82
R-2 0.7782 0.0063 1.938 0.001 70
R-3 0.7284 0.0043 1.898 0.001 70
G-1 2.6734 0.0211 3.341 0.001 72
G-2 2.3866 0.0515 3.483 0.001 83
G-3 2.5716 0.0404 3.412 0.001 74
B-1 0.7218 0.0106 3.443 0.001 73
B-2 0.8477 0.0147 3.445 0.001 70
B-3 0.8178 0.0180 3.460 0.001 70
W-1 0.6892 0.0038 3.346 0.001 69
W-2 0.7186 0.0025 3.477 0.001 69
W-3 0.7019 0.0025 3.486 0.001 71
D-1 0.0645 0.0002 3.514 0.002 189
D-2 0.0619 0.0004 3.525 0.002 117
5.14. MKEH
MKEH of Hungary measured the artifact set #6 in its second round from 20 November
2008 to 09 December 2008. The laboratory conditions are reported as temperature of
(22.8 ± 0.8) ºC and relative humidity of (30 ± 10) %. Table 5-14 shows the reported
results of MKEH. Note that two LEDs (#5-R-3 and #5-G-2) are damaged during the
measurement in MKEH.
Table 5-14. Measurement results of MKEH.
artifact LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V) burning
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set time (min)
#5
R-1 0.7211 0.0095 1.911 0.0011 90
R-2 0.6712 0.0069 1.898 0.0010 90
R-3 N.A. N.A. N.A. N.A. N.A.
G-1 2.6823 0.0298 3.319 0.0016 100
G-2 N.A. N.A. N.A. N.A. N.A.
G-3 2.5935 0.0209 3.3425 0.0008 80
B-1 0.9729 0.0162 3.442 0.0021 100
B-2 0.8645 0.0113 3.397 0.0016 80
B-3 0.8548 0.0137 3.401 0.0017 110
W-1 0.6944 0.0055 3.4245 0.0010 90
W-2 0.6908 0.0068 3.423 0.0006 70
W-3 0.7207 0.0060 3.439 0.0014 70
D-1 0.0970 0.0007 3.373 0.0011 60
D-2 0.0728 0.0006 3.471 0.0011 60
5.15. INM
INM of Romania measured the artifact set #7 in its second round from 13 December
2008 to 16 December 2008. The laboratory conditions are reported as temperature of
(25.0 ± 0.2) ºC and relative humidity of (30 ± 5) %. Table 5-15 shows the reported results
of INM.
Table 5-15. Measurement results of INM.
artifact
set LED ILED (cd) U(ILED) (cd) Vj (V) U(Vj) (V)
burning
time (min)
#7
R-1 0.748 0.082 1.925 0.006 5
R-2 0.810 0.089 1.906 0.006 5
R-3 0.765 0.084 1.926 0.006 5
G-1 3.134 0.345 3.303 0.010 5
G-2 2.958 0.325 3.366 0.010 5
G-3 3.221 0.354 3.306 0.010 5
B-1 0.942 0.104 3.467 0.010 5
B-2 0.960 0.106 3.403 0.010 5
B-3 0.930 0.102 3.436 0.010 5
W-1 0.746 0.082 3.478 0.010 5
W-2 0.706 0.078 3.367 0.010 5
W-3 0.697 0.077 3.421 0.010 5
D-1 0.090 0.010 3.452 0.010 5
D-2 0.100 0.011 3.453 0.010 5
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6. Pre-draft A Process
After the measurement process is completed, the preparation of the comparison report is
conducted according to the CCPR Guidelines. 17 The pre-draft A process consists of
verification of reported results, review of uncertainty budgets, and review of relative data.
In this chapter, we also describe the temperature-corrected results and the identification
of outliers.
6.1. Verification of Reported Results
The verification of reported results started in November 2009 after most of the
participants have submitted their results. The pilot sent to each participant the submitted
result values and the technical report including the uncertainty budgets. The participant
reviewed it to correct any error. After the participant confirmed the final version, no
correction is applied in the results and in the technical reports of the participants.
6.2. Temperature Correction and Artifact Drift
After the results are finalized by the verification, the pilot applied the temperature
correction based on the Eq. (3-1). By using the temperature sensitivity coefficients a, b,
and c of each LED and the measured junction voltages reported by the participants, all
the results could be converted to the values expected at the same junction voltage, i.e.,
at the same reference condition with a temperature of T0. We took the initial control
measurement of the pilot for each round as the reference condition for correction.
The tables below summarize the results before and after the temperature correction
for each measurement round. The relative differences of the participant’s results and of
the pilot’s results by the temperature correction are also calculated in the last two
columns to show the magnitudes of the correction. Note that the uncertainty of the
temperature correction was estimated to be 0.5 % as a relative standard uncertainty (see
Chapter 3), while all the participants claimed the uncertainty of the junction voltage
measurement much lower than this.
Table 6-1. Results of temperature correction for the round to MIKES.
artifact LED 1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected
relative
difference
relative
difference
17 CCPR Key Comparison Working Group, Guidelines for CCPR Comparison Report Preparation, Rev. 2 (Sept. 18, 2009), available at http://www.bipm.org/en/committees/cc/ccpr/publications_cc.html
APMP.PR-S3a Averaged LED Intensity Final Report
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set IP1 (cd) IL (cd) IP2 (cd) IL* (cd) IP2
* (cd)
IL* - IL IP2
* – IP2
#1
R-1 0.7067 0.729 0.7111 0.7124 0.7070 -2.33% -0.57%
R-2 0.6954 0.724 0.7025 0.7049 0.6962 -2.71% -0.91%
R-3 0.6967 0.721 0.7030 0.7039 0.6982 -2.43% -0.69%
G-1 2.6916 2.753 2.6834 2.7294 2.6778 -0.87% -0.21%
G-2 2.5223 2.576 2.5127 2.5578 2.5084 -0.71% -0.17%
G-3 2.6824 2.731 2.6904 2.7076 2.6843 -0.86% -0.23%
B-1 0.8124 0.827 0.8032 0.8289 0.8034 0.23% 0.03%
B-2 0.8394 0.847 0.8310 0.8483 0.8311 0.15% 0.01%
B-3 0.8476 0.865 0.8456 0.8628 0.8451 -0.26% -0.07%
W-1 0.6423 0.709 0.6872 0.6986 0.6864 -1.50% -0.12%
W-2 0.6356 0.658 0.6323 0.6492 0.6318 -1.35% -0.08%
W-3 0.7009 0.725 0.6992 0.7157 0.6988 -1.30% -0.05%
D-1 0.0848 0.0872 0.0844 0.0868 0.0844 -0.47% -0.02%
D-2 0.0904 0.0926 0.0902 0.0921 0.0902 -0.53% -0.07%
Table 6-2. Results of temperature correction for the round to CMS-ITRI.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#2
R-1 0.6856 0.700 0.6944 0.6781 0.6804 -3.23% -2.05%
R-2 0.6905 0.699 0.6981 0.6781 0.6835 -3.08% -2.13%
R-3 0.7083 0.716 0.7143 0.6943 0.6986 -3.12% -2.25%
G-1 2.4467 2.581 2.5733 2.5591 2.5643 -0.85% -0.35%
G-2 2.5335 2.565 2.5322 2.5419 2.5236 -0.91% -0.34%
G-3 2.7702 2.790 2.7863 2.7578 2.7750 -1.17% -0.41%
B-1 0.7669 0.748 0.7560 0.7479 0.7557 -0.02% -0.05%
B-2 0.8380 0.826 0.8306 0.8221 0.8284 -0.47% -0.27%
B-3 0.7736 0.762 0.7698 0.7624 0.7695 0.06% -0.03%
W-1 0.6715 0.685 0.6786 0.6751 0.6756 -1.47% -0.45%
W-2 0.6863 0.695 0.6875 0.6849 0.6843 -1.48% -0.47%
W-3 0.6173 0.625 0.6183 0.6137 0.6138 -1.84% -0.72%
D-1 0.0892 0.090 0.0890 0.0899 0.0890 -0.15% 0.03%
D-2 0.0743 0.075 0.0738 0.0749 0.0738 -0.19% 0.00%
Table 6-3. Results of temperature correction for the round to PTB.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#3
R-1 0.7154 0.7226 0.6983 0.7248 0.7079 0.30% 1.36%
R-2 0.7383 0.7324 0.7190 0.7382 0.7318 0.79% 1.74%
R-3 0.7344 0.7394 0.7146 0.7432 0.7263 0.51% 1.60%
G-1 2.7833 2.8081 2.7444 2.8112 2.7598 0.11% 0.56%
G-2 2.5187 2.5521 2.5048 2.5503 2.5166 -0.07% 0.47%
G-3 2.4658 2.4880 2.4366 2.4859 2.4511 -0.08% 0.59%
B-1 0.8172 0.8139 0.8120 0.8132 0.8117 -0.09% -0.04%
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B-2 0.8755 0.8516 0.8604 0.8502 0.8602 -0.16% -0.03%
B-3 0.7054 0.7097 0.6980 0.7085 0.6985 -0.17% 0.07%
W-1 0.6831 0.6912 0.6711 0.6933 0.6783 0.31% 1.06%
W-2 0.6695 0.6789 0.6572 0.6805 0.6639 0.24% 1.01%
W-3 0.6931 0.7064 0.6827 0.7072 0.6889 0.11% 0.91%
D-1 0.0857 0.0860 0.0849 0.0865 0.0853 0.55% 0.53%
D-2 0.0964 0.0973 0.0956 0.0979 0.0961 0.58% 0.49%
Table 6-4. Results of temperature correction for the round to NMIJ.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#4
R-1 0.7335 0.718 0.7229 0.7226 0.7293 0.67% 0.88%
R-2 0.6829 0.674 0.6746 0.6748 0.6799 0.11% 0.78%
R-3 0.7061 0.698 0.6979 0.6995 0.7029 0.19% 0.71%
G-1 2.6564 2.727 2.6238 2.7359 2.6305 0.32% 0.25%
G-2 2.8201 2.887 2.7930 2.8957 2.8006 0.30% 0.27%
G-3 2.6927 2.753 2.6636 2.7564 2.6718 0.12% 0.30%
B-1 0.9329 0.937 0.9182 0.9369 0.9180 -0.01% -0.02%
B-2 0.8038 0.835 0.7942 0.8349 0.7939 -0.02% -0.03%
B-3 0.8905 0.930 0.8769 0.9297 0.8764 -0.04% -0.06%
W-1 0.7076 0.711 0.6897 0.7148 0.6947 0.53% 0.72%
W-2 0.6977 0.704 0.6846 0.7047 0.6878 0.16% 0.47%
W-3 0.7112 0.721 0.6991 0.7220 0.7019 0.17% 0.40%
D-1 0.0636 0.0652 0.0631 0.0655 0.0634 0.50% 0.44%
D-2 0.0887 0.0909 0.0879 0.0912 0.0882 0.33% 0.34%
Table 6-5. Results of temperature correction for the round to CENAM.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#5
R-1 0.6939 0.4675 0.6977 0.4598 0.6978 -1.66% 0.01%
R-2 0.7185 0.4888 0.7190 0.4806 0.7190 -1.70% 0.00%
R-3 0.6691 0.4605 0.6745 0.4531 0.6733 -1.64% -0.17%
G-1 2.6549 2.3458 2.6840 2.3282 2.6834 -0.75% -0.02%
G-2 2.4914 2.2183 2.4800 2.1989 2.4784 -0.88% -0.06%
G-3 2.5619 2.3287 2.5746 2.3078 2.5721 -0.91% -0.10%
B-1 0.7896 0.7490 0.8006 0.7511 0.8006 0.29% 0.00%
B-2 0.8971 0.8259 0.9120 0.8270 0.9118 0.14% -0.02%
B-3 0.9084 0.8289 0.9145 0.8304 0.9143 0.19% -0.02%
W-1 0.6718 0.5544 0.6699 0.5488 0.6725 -1.02% 0.38%
W-2 0.7006 0.5815 0.7018 0.5750 0.7036 -1.14% 0.25%
W-3 0.6810 0.5654 0.6822 0.5586 0.6832 -1.21% 0.14%
D-1 0.0653 0.0576 0.0653 0.0571 0.0650 -0.89% -0.39%
D-2 0.0620 0.0544 0.0621 0.0539 0.0618 -0.97% -0.44%
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Table 6-6. Results of temperature correction for the round to LNE.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#6
R-1 0.7000 0.745 0.7136 0.7257 0.7076 -2.66% -0.84%
R-2 0.6563 0.692 0.6635 0.6740 0.6575 -2.67% -0.91%
R-3 0.7023 0.750 0.7144 0.7298 0.7082 -2.77% -0.88%
G-1 2.8398 2.985 2.8575 2.9632 2.8493 -0.74% -0.29%
G-2 2.7226 2.861 2.7450 2.8443 2.7372 -0.59% -0.29%
G-3 2.4871 2.603 2.4902 2.5850 2.4814 -0.70% -0.35%
B-1 0.9185 0.934 0.9231 0.9337 0.9224 -0.03% -0.08%
B-2 0.8098 0.816 0.8125 0.8158 0.8116 -0.03% -0.11%
B-3 0.8244 0.825 0.8236 0.8251 0.8228 0.01% -0.09%
W-1 0.6933 0.709 0.6739 0.7026 0.6716 -0.91% -0.34%
W-2 0.6828 0.702 0.6709 0.6941 0.6680 -1.13% -0.43%
W-3 0.7091 0.731 0.7016 0.7236 0.6986 -1.02% -0.44%
D-1 0.0935 0.0987 0.0937 0.0980 0.0933 -0.67% -0.40%
D-2 0.0706 0.0746 0.0707 0.0742 0.0705 -0.53% -0.34%
Table 6-7. Results of temperature correction for the round to METAS.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#7
R-1 0.6807 0.6902 0.6852 0.6713 0.6870 -2.81% 0.26%
R-2 0.7452 0.7577 0.7481 0.7386 0.7494 -2.58% 0.18%
R-3 0.6825 0.6904 0.6859 0.6694 0.6864 -3.14% 0.07%
G-1 2.7469 2.8012 2.7600 2.7822 2.7613 -0.68% 0.05%
G-2 2.6392 2.6865 2.6432 2.6702 2.6451 -0.61% 0.07%
G-3 2.8487 2.9087 2.8590 2.8892 2.8621 -0.67% 0.11%
B-1 0.8634 0.8823 0.8619 0.8835 0.8619 0.13% 0.00%
B-2 0.8611 0.8901 0.8635 0.8938 0.8634 0.41% -0.01%
B-3 0.8316 0.8471 0.8390 0.8459 0.8393 -0.14% 0.03%
W-1 0.6735 0.6862 0.6723 0.6773 0.6726 -1.32% 0.05%
W-2 0.6323 0.6414 0.6321 0.6341 0.6332 -1.16% 0.18%
W-3 0.6261 0.6359 0.6268 0.6291 0.6284 -1.09% 0.25%
D-1 0.0747 0.07577 0.0745 0.0757 0.0747 -0.15% 0.19%
D-2 0.0841 0.08483 0.0833 0.0846 0.0835 -0.32% 0.22%
Table 6-8. Results of temperature correction for the round to NMC-A*STAR.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#8
R-1 0.6941 0.713 0.6945 0.7087 0.6965 -0.61% 0.29%
R-2 0.6875 0.702 0.6850 0.6984 0.6866 -0.52% 0.24%
R-3 0.7175 0.735 0.7180 0.7319 0.7195 -0.43% 0.20%
G-1 2.6454 2.678 2.6504 2.6811 2.6531 0.12% 0.10%
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G-2 2.6749 2.701 2.6693 2.7020 2.6721 0.04% 0.11%
G-3 2.6376 2.648 2.6278 2.6518 2.6319 0.14% 0.15%
B-1 0.8573 0.865 0.8567 0.8651 0.8569 0.01% 0.02%
B-2 0.8583 0.873 0.8621 0.8732 0.8624 0.03% 0.04%
B-3 0.8428 0.856 0.8433 0.8560 0.8433 0.00% 0.01%
W-1 0.6586 0.666 0.6569 0.6666 0.6585 0.09% 0.25%
W-2 0.5997 0.604 0.5965 0.6050 0.5982 0.17% 0.27%
W-3 0.6224 0.627 0.6195 0.6285 0.6212 0.24% 0.28%
D-1 0.0871 0.0876 0.0867 0.0879 0.0868 0.31% 0.15%
D-2 0.0913 0.0925 0.0912 0.0927 0.0913 0.25% 0.07%
Table 6-9. Results of temperature correction for the round to VSL.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#1
R-1 0.7111 0.728 0.7107 0.7279 0.7131 -0.01% 0.33%
R-2 0.7025 0.711 0.6999 0.7118 0.7049 0.11% 0.71%
R-3 0.7030 0.717 0.7039 0.7179 0.7080 0.13% 0.58%
G-1 2.6834 2.746 2.6964 2.7499 2.7031 0.14% 0.25%
G-2 2.5127 2.586 2.5178 2.5887 2.5249 0.10% 0.28%
G-3 2.6904 2.745 2.6687 2.7489 2.6762 0.14% 0.28%
B-1 0.8032 0.814 0.8051 0.8141 0.8047 0.02% -0.05%
B-2 0.8310 0.833 0.8197 0.8329 0.8196 -0.01% -0.01%
B-3 0.8456 0.852 0.8438 0.8523 0.8448 0.04% 0.11%
W-1 0.6872 0.698 0.6822 0.6993 0.6854 0.19% 0.47%
W-2 0.6323 0.644 0.6224 0.6447 0.6258 0.11% 0.55%
W-3 0.6992 0.712 0.6863 0.7125 0.6904 0.06% 0.59%
D-1 0.0844 0.0870 0.0837 0.0871 0.0839 0.15% 0.16%
D-2 0.0902 0.0919 0.0900 0.0915 0.0901 -0.46% 0.13%
Table 6-10. Results of temperature correction for the round to NMIA.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#2
R-1 0.6795 0.793 0.6856 0.7660 0.6890 -3.53% 0.50%
R-2 0.6855 0.800 0.6905 0.7722 0.6938 -3.60% 0.48%
R-3 0.6996 0.806 0.7083 0.7745 0.7114 -4.07% 0.44%
G-1 2.5733 2.600 2.5856 2.5659 2.5889 -1.33% 0.13%
G-2 2.5322 2.540 2.5485 2.5079 2.5517 -1.28% 0.13%
G-3 2.7863 2.456 2.8055 2.4216 2.8090 -1.42% 0.12%
B-1 0.7560 0.729 0.7630 0.7305 0.7632 0.20% 0.02%
B-2 0.8306 0.813 0.8344 0.8108 0.8349 -0.27% 0.06%
B-3 0.7698 0.737 0.7741 0.7395 0.7741 0.34% 0.00%
W-1 0.6786 0.729 0.6753 0.7140 0.6773 -2.10% 0.30%
W-2 0.6875 0.745 0.6857 0.7285 0.6889 -2.27% 0.46%
W-3 0.6183 0.662 0.6147 0.6468 0.6153 -2.35% 0.10%
D-1 0.0890 0.0906 0.0880 0.0895 0.0881 -1.20% 0.10%
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D-2 0.0738 0.0754 0.0733 0.0745 0.0733 -1.15% 0.08%
Table 6-11. Results of temperature correction for the round to NIST.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#3
R-1 0.6983 0.728 0.7026 0.7319 0.7054 0.53% 0.40%
R-2 0.7190 0.741 0.7200 0.7454 0.7223 0.60% 0.32%
R-3 0.7146 0.746 0.7178 0.7517 0.7199 0.76% 0.30%
G-1 2.7444 2.898 2.7466 2.9070 2.7496 0.31% 0.11%
G-2 2.5048 2.599 2.4973 2.6045 2.5007 0.21% 0.13%
G-3 2.4366 2.541 2.4403 2.5506 2.4441 0.38% 0.15%
B-1 0.8120 0.828 0.8068 0.8283 0.8068 0.04% 0.00%
B-2 0.8604 0.888 0.8602 0.8884 0.8603 0.04% 0.01%
B-3 0.6980 0.722 0.6938 0.7228 0.6939 0.11% 0.02%
W-1 0.6711 0.702 0.6697 0.7059 0.6698 0.55% 0.02%
W-2 0.6572 0.686 0.6538 0.6895 0.6538 0.50% -0.01%
W-3 0.6827 0.713 0.6807 0.7161 0.6814 0.44% 0.10%
D-1 0.0849 0.0898 0.0844 0.0901 0.0844 0.35% 0.01%
D-2 0.0956 0.1007 0.0951 0.1010 0.0951 0.28% 0.03%
Table 6-12. Results of temperature correction for the round to VNIIOFI.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#5
R-1 0.6977 0.7558 0.6966 0.7318 0.6961 -3.27% -0.08%
R-2 0.7190 0.7782 0.7205 0.7524 0.7191 -3.42% -0.19%
R-3 0.6745 0.7284 0.6757 0.7061 0.6752 -3.16% -0.07%
G-1 2.6840 2.6734 2.6498 2.6427 2.6485 -1.16% -0.05%
G-2 2.4800 2.3866 2.4426 2.3600 2.4412 -1.13% -0.06%
G-3 2.5746 2.5716 2.5854 2.5445 2.5839 -1.06% -0.06%
B-1 0.8006 0.7218 0.7948 0.7254 0.7948 0.50% 0.00%
B-2 0.9120 0.8477 0.9085 0.8506 0.9087 0.35% 0.01%
B-3 0.9145 0.8178 0.9085 0.8212 0.9085 0.41% 0.00%
W-1 0.6699 0.6892 0.6655 0.6756 0.6669 -2.01% 0.21%
W-2 0.7018 0.7186 0.6975 0.7044 0.6994 -2.02% 0.27%
W-3 0.6822 0.7019 0.6804 0.6869 0.6796 -2.18% -0.11%
D-1 0.0653 0.0645 0.0645 0.0641 0.0644 -0.62% -0.06%
D-2 0.0621 0.0619 0.0616 0.0615 0.0616 -0.60% 0.01%
Table 6-13. Results of temperature correction for the round to MKEH.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#6 R-1 0.7136 0.7211 0.7108 0.7051 0.7121 -2.26% 0.18%
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R-2 0.6635 0.6712 N.A. 0.6547 N.A. -2.52% N.A.
R-3 0.7144 N.A. N.A. N.A. N.A. N.A. N.A.
G-1 2.8575 2.6823 N.A. 2.6614 N.A. -0.78% N.A.
G-2 2.7450 N.A. N.A. N.A. N.A. N.A. N.A.
G-3 2.4902 2.5935 2.4712 2.5765 2.4744 -0.66% 0.13%
B-1 0.9231 0.9729 0.9130 0.9739 0.9132 0.10% 0.02%
B-2 0.8125 0.8645 0.8037 0.8661 0.8038 0.18% 0.01%
B-3 0.8236 0.8548 N.A. 0.8554 N.A. 0.07% N.A.
W-1 0.6739 0.6944 0.6714 0.6879 0.6715 -0.94% 0.02%
W-2 0.6709 0.6908 0.6651 0.6844 0.6655 -0.94% 0.06%
W-3 0.7016 0.7207 0.6949 0.7143 0.6958 -0.90% 0.13%
D-1 0.0937 0.0970 0.0933 0.0968 0.0933 -0.22% -0.04%
D-2 0.0707 0.0728 N.A. 0.0726 N.A. -0.27% N.A.
Table 6-14. Results of temperature correction for the round to INM.
artifact
set LED
1. meas.
of pilot
participant
lab
2. meas.
of pilot temperature corrected relative
difference
IL* - IL
relative
difference
IP2* – IP2 IP1 (cd) IL (cd) IP2 (cd) IL
* (cd) IP2
* (cd)
#7
R-1 0.6852 0.748 0.6656 0.7406 0.6707 -1.00% 0.76%
R-2 0.7481 0.810 0.7323 0.8045 0.7389 -0.69% 0.90%
R-3 0.6859 0.765 0.6743 0.7531 0.6798 -1.58% 0.80%
G-1 2.7600 3.134 2.7171 3.1262 2.7271 -0.25% 0.37%
G-2 2.6432 2.958 2.6188 2.9537 2.6283 -0.15% 0.36%
G-3 2.8590 3.221 2.8165 3.2142 2.8275 -0.21% 0.39%
B-1 0.8619 0.942 0.8221 0.9421 0.8223 0.01% 0.02%
B-2 0.8635 0.960 0.8425 0.9603 0.8428 0.03% 0.03%
B-3 0.8390 0.930 0.8138 0.9290 0.8151 -0.11% 0.16%
W-1 0.6723 0.746 0.6616 0.7441 0.6691 -0.26% 1.12%
W-2 0.6321 0.706 0.6242 0.7032 0.6295 -0.40% 0.83%
W-3 0.6268 0.697 0.6174 0.6935 0.6226 -0.50% 0.83%
D-1 0.0745 0.090 0.0741 0.0899 0.0742 -0.07% 0.23%
D-2 0.0833 0.100 0.0828 0.0965 0.0830 -3.60% 0.23%
Based on the temperature-corrected results of the pilot, the drift of the artifact LEDs
could be analyzed. Each LED is measured by the pilot two or three times depending on
the measurement rounds. The relative changes of the averaged LED intensity measured
by the pilot for each artifact LED are shown in the following figures, separated to a plot
without temperature correction and to a plot after correction. They show that the effect
of the temperature correction is small because the laboratory condition of the pilot was
little changed during the comparison. The most of the artifact LEDs show a drift smaller
than ±1 % for each round that is comparable to the measurement uncertainty of the
pilot. However, a few LEDs underwent a large drift and should be excluded from the data
analysis. The exclusion of the non-stable artifact LEDs is decided by the participant
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through the procedure of review of relative data.
Fig. 6-1. Drift of the artefact set #1.
Fig. 6-2. Drift of the artefact set #2.
Fig. 6-3. Drift of the artefact set #3.
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Fig. 6-4. Drift of the artefact set #4.
Fig. 6-5. Drift of the artefact set #5.
Fig. 6-6. Drift of the artefact set #6.
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Fig. 6-7. Drift of the artefact set #7.
Fig. 6-8. Drift of the artefact set #8.
6.3. Review of Relative Data
The review of relative data started in December 2009. The pilot sent to the participants a
document with the relative data of each participant, which are the data reduced to check
only the stability of the artifact LEDs and the internal consistency of each participant. The
document circulated for the review of relative data is included in Appendix B: Review of
Relative Data as an electronic file. Note that both the uncorrected and temperature-
corrected data are separately presented.
The review comments of the participants are collected by the pilot and their
summary is included in Appendix C: Comments from Review of Relative Data. As a result
of the review of relative data, the data of the following artifact LEDs will be excluded
from the analysis on request of the participants and also due to damages during a
comparison round.
- #1-W-1 measured by MIKES (large drift)
- #2-G-1 measured by CMS-ITRI (large drift)
- #4-B-1/B-3/W-1 measured by NMIJ (large drift)
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- #6-R-2/R-3/G-1/G-2/B-3/D-2 measured by MKEH (damage)
- #7-B-1 measured by INM (large drift)
6.4. Review of Uncertainty Budgets
The review of relative data started in March 2010 and completed in June 2010. The pilot
summarized the technical reports and uncertainty budgets of the participants to one
document and sent it to all the participants. We note that two participants, NMIA and
VNIIOFI, could not participate to the review process because their submission of the
technical report was delayed for NMIA and abandoned for VNIIOFI. The discussion
among the participants and the revisions of the budgets are conducted according to the
CCPR Guidelines. The review comments of the participants are collected by the pilot and
their summary is included in Appendix D: Comments from Review of Uncertainty Budgets.
The final version of the uncertainty budgets is summarized in Chapter 4.
6.5. Identification of Outliers
For the identification of outliers that can significantly skew the reference value of the
comparison, the pilot prepared a document with the relative deviation data of each
participant from the simple mean values of all the participants without disclosing the
participant’s identity and the absolute results. The document sent to the participant in
June 2010 is included in Appendix E: Identification of Outliers. As a result of the
discussion, it was agreed in September 2010 that the data with a relative deviation of
more than ±10 % from the mean are to identify as outliers. As the measurements of
each type (color) of LEDs are taken as each separate comparison, the outlier will be
excluded only from the analysis for the related LED type.
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7. Data Analysis
The data analysis is performed based on the example in Appendix B of the CCPR
Guidelines.18 The only difference was the sequence of each round: “pilot – participant –
pilot” in the LED comparison, while “participant – pilot – participant” in the example of
the Guidelines. In this chapter, the equations of each analysis step are described. The
complete data of the calculation is included as an electronic file (Excel spreadsheet) at
the end of the chapter. Note that the analysis is repeated for each type of LEDs, and also
for the data without and with the temperature-correction.
7.1. Calculation of Difference to Pilot
For each participant with index i and for each LED with index j, the two measurement
results of the pilot (index P), before (index P1) and after (index P2) the participant, are
averaged by
1 2
, , ,
1
2
P P P
i j i j i jI I I . (7-1)
The relative standard uncertainty of the pilot’s average value Ii,jP is calculated from the
relative standard uncertainty ur,corP of the correlated components (scale uncertainty) and
the relative standard uncertainty ur,ucP of the uncorrelated components (transfer
uncertainty) according to
2
2 2
, , ,21
1( )
2
P P Pk
r i j r cor r uc
k
u I u u
. (7-2)
The values of ur,corP and ur,uc
Pk are determined by combing the related components in the
reported uncertainty budgets of the pilot in Table 4-1 ~ Table 4-5. Note that the pilot
reported and applied the upper boundary values for all the uncertainty components in
the budgets so that the relative standard uncertainty of each measurement remained the
same for each LED type.
The relative difference Δi,j between the participant i and the pilot (index P) for each
LED j is then calculated by
,
,
,
1i j
i j P
i j
I
I (7-3)
and its uncertainty by
2 22
, , , , ,( ) P
i j r i j r uc r add i ju u I u u I . (7-4)
18 CCPR Key Comparison Working Group, Guidelines for CCPR Comparison Report Preparation, Rev. 2 (Sept. 18, 2009), available at http://www.bipm.org/en/committees/cc/ccpr/publications_cc.html
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Here, ur,add(Ii,j) denotes the additional uncertainty in the measurement of LED j by the
participant i due to non-ideal characteristics of the artifact LEDs. For the results without
temperature correction, we used the drift of the LED for the corresponding round as the
value of ur,add(Ii,j), which is calculated from the relative difference of the two measurement
results of the pilot. For the results with temperature correction, the relative standard
uncertainty of the correction procedure of 0.5 % is additionally combined to ur,add(Ii,j). The
relative standard uncertainty of the participant ur(Ii,j) is determined from the reported
expanded results in Chapter 5.
Finally, the results of the multiple LEDs for each type are averaged for the participant
i by
,
1
3i i j
j
. (7-5)
Under assumption that the results of multiple LEDs measured by the same participant are
strongly correlated, the uncertainty of the relative differences is calculated simply by
,
1
3i i j
j
u u . (7-6)
For the pilot, we use now the index i = 0 and set Δ0 = 0. According to Eq. (7-4), the
uncertainty u(Δ0) for the pilot is the same as the total relative standard uncertainty
averaged over all the measurements by the pilot. For case of the temperature corrected
results, we added also the uncertainty of the correction to u(Δ0).
7.2. Calculation of Comparison Reference Value
The Reference Value (RV) of the comparison for each LED type is calculated using
weighted mean with cut-off. The cut-off value ucut is calculated by
for ; 0,...,cut r i r i r iu average u I u I median u I i N . (7-7)
Note that the outliers are not included in the calculation of the RV so that the number N
denotes the number of the participants whose comparison results are not identified as
outliers (the pilot not counted as a participant here).
The total relative standard uncertainty ur(Ii) of each participant i, averaged over LEDs
with different j, is adjusted by the cut-off (i = 0, …, N):
,
,
for
otherwise
r adj i r i r i cut
r adj i cut
u I u I u I u
u I u
(7-8)
Also, the uncertainty of Δi is adjusted after cut-off by
2 2
,adj i r adj i T iu u I u . (7-9)
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Here, uT(Δi) denotes the transfer uncertainty component in u(Δi), which is separated by
2 2
T i i r iu u u I . (7-10)
These uncertainties are used to calculate the weights wi for each participant i given by
2
2
0
adj i
i N
adj i
i
uw
u
. (7-11)
Finally, the RV is determined by
0
N
RV i i
i
w
. (7-12)
The uncertainty of the comparison RV is given by
2
40
2
0
Ni
i adj i
RV N
adj i
i
u
uu
u
. (7-13)
7.3. Calculation of Degree of Equivalence
The unilateral degree of equivalence (DoE) of the participant i is defined by
i i RVD . (7-14)
The DoE is calculated according to Eq. (7-13) also for the participants whose comparison
results are identified as outliers. However, the uncertainty of DoE is different. For the
participants whose results are included in the calculation of the RV, the uncertainty of
DoE is given, as an expanded uncertainty with a coverage factor k = 2, by
2
2 2 2
20
2N
i
i i RV adj i
iadj i
uU k u u u
u
. (7-15)
For the participants whose results are excluded in the calculation of the RV, the
uncertainty of DoE is simplified to
2 2
i i RVU k u u . (7-16)
7.4. Data Analysis Spreadsheet
The Excel-file can be opened by a double-click on the icon below.
DoE_intensity_rev.xlsx
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8. Comparison Results
8.1. Red LEDs
The comparison RV for averaged LED intensity of red LEDs is calculated to be
0.02292, 0.80% ( 2)RV rU k
for the results without temperature correction, and
0.01091, 0.84% ( 2)RV rU k
for the results after temperature correction. Table 8-1
and Table 8-2 summarize the comparison results for red LEDs without and with
temperature correction, respectively. The last column of each table shows the En criteria
of each participant, which is defined as the absolute ratio of Di and U(Di). Note that the
results of CENAM and NMIA are identified as outliers and not included in the calculation
of the RV.
Table 8-1. Comparison results for red LEDs without temperature correction.
participant Δi u(Δi) wi Di U(Di) En
MIKES 0.03151 2.06% 0.03960 0.009 0.040 0.225
CMS-ITRI 0.00929 2.40% 0.02933 -0.014 0.047 0.298
PTB 0.01596 2.90% 0.02007 -0.007 0.057 0.123
NMIJ -0.00891 1.96% 0.04403 -0.032 0.038 0.842
CENAM -0.32086 2.98% N.A. -0.344 0.060 5.733
LNE 0.05384 2.10% 0.03832 0.031 0.041 0.756
METAS 0.01149 1.26% 0.10168 -0.011 0.024 0.458
NMC-
A*STAR 0.02462 1.43% 0.08192 0.002 0.027 0.074
VSL 0.01912 1.21% 0.11592 -0.004 0.023 0.174
NMIA 0.15655 1.72% N.A. 0.134 0.035 3.829
NIST 0.03693 1.58% 0.06753 0.014 0.030 0.467
VNIIOFI 0.08143 0.97% 0.11827 0.059 0.019 3.105
MKEH 0.01255 1.19% 0.10954 -0.010 0.022 0.455
INM 0.10887 6.00% 0.00468 0.086 0.120 0.717
KRISS 0.00000 0.86% 0.22911 -0.023 0.015 1.533
Table 8-2. Comparison results for red LEDs after temperature correction.
participant Δi u(Δi) wi Di U(Di) En
MIKES 0.01006 1.98% 0.04708 -0.001 0.039 0.026
CMS-ITRI -0.01104 2.49% 0.02973 -0.022 0.049 0.449
PTB 0.01346 1.76% 0.05980 0.003 0.034 0.088
NMIJ -0.00961 1.64% 0.06896 -0.021 0.032 0.656
CENAM -0.33182 3.05% N.A. -0.343 0.062 5.532
LNE 0.03061 1.66% 0.06715 0.020 0.032 0.625
METAS -0.01732 1.44% 0.08511 -0.028 0.028 1.000
NMC-
A*STAR 0.01811 1.53% 0.07883 0.007 0.029 0.241
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VSL 0.01713 1.38% 0.09624 0.006 0.026 0.231
NMIA 0.11230 2.11% N.A. 0.101 0.043 2.349
NIST 0.04173 1.77% 0.05923 0.031 0.034 0.912
VNIIOFI 0.04763 1.09% 0.10799 0.037 0.021 1.762
MKEH -0.01077 1.25% 0.10717 -0.022 0.024 0.917
INM 0.09245 5.84% 0.00542 0.082 0.116 0.707
KRISS 0.00000 0.99% 0.18728 -0.011 0.018 0.611
The DoEs and its uncertainties for red LEDs are plotted in Fig. 8-1 as dot symbols
and error bars, respectively. The red lines indicate the expanded relative uncertainty of
the comparison RV.
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Fig. 8-1. DoE for red LEDs without and with temperature correction.
8.2. Green LEDs
The comparison RV for averaged LED intensity of green LEDs is calculated to be
0.01408, 0.76% ( 2)RV rU k
for the results without temperature correction, and
0.01174, 0.80% ( 2)RV rU k
for the results after temperature correction. Table
8-3 and Table 8-4 summarize the comparison results for green LEDs without and with
temperature correction, respectively. The last column of each table shows the En criteria
of each participant, which is defined as the absolute ratio of Di and U(Di). Note that the
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146
results of CENAM and INM are identified as outliers and not included in the calculation
of the RV.
Table 8-3. Comparison results for green LEDs without temperature correction.
participant Δi u(Δi) wi Di U(Di) En
MIKES 0.02140 1.96% 0.03875 0.007 0.038 0.184
CMS-ITRI 0.00846 2.16% 0.03172 -0.006 0.043 0.140
PTB 0.01569 1.54% 0.05974 0.002 0.030 0.067
NMIJ 0.02985 1.87% 0.04243 0.016 0.037 0.432
CENAM -0.10736 3.53% N.A. -0.121 0.071 1.704
LNE 0.04678 1.41% 0.07451 0.033 0.027 1.222
METAS 0.01791 1.25% 0.09450 0.004 0.024 0.167
NMC-
A*STAR 0.00933 1.31% 0.08664 -0.005 0.025 0.200
VSL 0.02447 1.36% 0.08058 0.010 0.026 0.385
NMIA -0.03792 1.40% 0.07540 -0.052 0.027 1.926
NIST 0.04558 1.58% 0.05920 0.032 0.031 1.032
VNIIOFI -0.01040 1.62% 0.05609 -0.024 0.032 0.750
MKEH 0.04547 1.22% 0.07834 0.031 0.024 1.292
INM 0.13459 5.73% N.A. 0.121 0.115 1.052
KRISS 0.00000 0.82% 0.22211 -0.014 0.014 1.000
Table 8-4. Comparison results for green LEDs after temperature correction.
participant Δi u(Δi) wi Di U(Di) En
MIKES 0.01418 2.05% 0.03986 0.002 0.040 0.050
CMS-ITRI -0.00002 2.22% 0.03402 -0.012 0.044 0.273
PTB 0.01282 1.34% 0.08598 0.001 0.026 0.038
NMIJ 0.03100 1.79% 0.05210 0.019 0.035 0.543
CENAM -0.11460 3.58% N.A. -0.126 0.072 1.750
LNE 0.04139 1.43% 0.08172 0.030 0.027 1.111
METAS 0.01088 1.37% 0.08903 -0.001 0.026 0.038
NMC-
A*STAR 0.00972 1.39% 0.08663 -0.002 0.027 0.074
VSL 0.02441 1.47% 0.07803 0.013 0.028 0.464
NMIA -0.05123 1.55% 0.06967 -0.063 0.030 2.100
NIST 0.04803 1.66% 0.06081 0.036 0.032 1.125
VNIIOFI -0.02107 1.73% 0.05569 -0.033 0.034 0.971
MKEH 0.03797 1.25% 0.08369 0.026 0.024 1.083
INM 0.13019 5.69% N.A. 0.118 0.114 1.035
KRISS 0.00000 0.96% 0.18276 -0.012 0.017 0.706
The DoEs and its uncertainties for green LEDs are plotted in Fig. 8-2 as dot symbols
and error bars, respectively. The red lines indicate the expanded relative uncertainty of
the comparison RV.
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Fig. 8-2. DoE for green LEDs without and with temperature correction.
8.3. Blue LEDs
The comparison RV for averaged LED intensity of blue LEDs is calculated to be
0.00139, 0.86% ( 2)RV rU k
for the results without temperature correction, and
0.00035, 0.92% ( 2)RV rU k
for the results after temperature correction. Table
8-5 and Table 8-6 summarize the comparison results for blue LEDs without and with
temperature correction, respectively. The last column of each table shows the En criteria
of each participant, which is defined as the absolute ratio of Di and U(Di). Note that the
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results of INM are identified as outliers and not included in the calculation of the RV.
Table 8-5. Comparison results for blue LEDs without temperature correction.
participant Δi u(Δi) wi Di U(Di) En
MIKES 0.01988 2.07% 0.04539 0.021 0.040 0.525
CMS-ITRI -0.01338 2.42% 0.03319 -0.012 0.048 0.250
PTB -0.00280 1.86% 0.05641 -0.001 0.036 0.028
NMIJ 0.04507 2.19% 0.04057 0.046 0.043 1.070
CENAM -0.07850 3.39% 0.01695 -0.077 0.067 1.149
LNE 0.00717 1.76% 0.06287 0.009 0.034 0.265
METAS 0.02303 1.96% 0.05075 0.024 0.038 0.632
NMC-
A*STAR 0.01319 1.42% 0.09650 0.015 0.027 0.556
VSL 0.01005 1.41% 0.08744 0.011 0.027 0.407
NMIA -0.03628 1.52% 0.08461 -0.035 0.029 1.207
NIST 0.03089 2.17% 0.04125 0.032 0.043 0.744
VNIIOFI -0.08889 1.39% 0.09696 -0.088 0.026 3.385
MKEH 0.06477 1.58% 0.06883 0.066 0.031 2.129
INM 0.12319 6.55% N.A. 0.125 0.131 0.954
KRISS 0.00000 0.88% 0.21829 0.001 0.016 0.063
Table 8-6. Comparison results for blue LEDs after temperature correction.
participant Δi u(Δi) wi Di U(Di) En
MIKES 0.02035 2.13% 0.04765 0.021 0.042 0.500
CMS-ITRI -0.01421 2.52% 0.03388 -0.014 0.050 0.280
PTB -0.00421 1.93% 0.05813 -0.004 0.037 0.108
NMIJ 0.04506 2.27% 0.04203 0.045 0.044 1.023
CENAM -0.07657 3.42% 0.01845 -0.076 0.068 1.118
LNE 0.00749 1.82% 0.06505 0.008 0.035 0.229
METAS 0.02437 2.03% 0.05258 0.025 0.039 0.641
NMC-
A*STAR 0.01324 1.51% 0.09460 0.014 0.029 0.483
VSL 0.01013 1.49% 0.08592 0.010 0.029 0.345
NMIA -0.03558 1.61% 0.08340 -0.035 0.031 1.129
NIST 0.03147 2.23% 0.04348 0.032 0.044 0.727
VNIIOFI -0.08508 1.47% 0.09396 -0.085 0.028 3.036
MKEH 0.06616 1.64% 0.06998 0.067 0.032 2.094
INM 0.12254 6.54% N.A. 0.123 0.131 0.939
KRISS 0.00000 1.01% 0.21088 0.000 0.018 0.000
The DoEs and its uncertainties for blue LEDs are plotted in Fig. 8-3 as dot symbols
and error bars, respectively. The red lines indicate the expanded relative uncertainty of
the comparison RV.
APMP.PR-S3a Averaged LED Intensity Final Report
149
Fig. 8-3. DoE for blue LEDs without and with temperature correction.
8.4. White LEDs
The comparison RV for averaged LED intensity of white LEDs is calculated to be
0.02539, 0.64% ( 2)RV rU k
for the results without temperature correction, and
0.01870, 0.70% ( 2)RV rU k
for the results after temperature correction. Table
8-7 and Table 8-8 summarize the comparison results for white LEDs without and with
temperature correction, respectively. The last column of each table shows the En criteria
of each participant, which is defined as the absolute ratio of Di and U(Di). Note that the
APMP.PR-S3a Averaged LED Intensity Final Report
150
results of CENAM are identified as outliers and not included in the calculation of the RV.
Table 8-7. Comparison results for white LEDs without temperature correction.
participant Δi u(Δi) wi Di U(Di) En
MIKES 0.03679 1.80% 0.03376 0.011 0.035 0.314
CMS-ITRI 0.01271 2.13% 0.02432 -0.013 0.042 0.310
PTB 0.02372 1.91% 0.03001 -0.002 0.038 0.053
NMIJ 0.02013 2.18% 0.02304 -0.005 0.043 0.116
CENAM -0.17163 2.91% N.A. -0.197 0.059 3.339
LNE 0.03690 2.13% 0.02415 0.012 0.042 0.286
METAS 0.01646 0.92% 0.13083 -0.009 0.017 0.529
NMC-
A*STAR 0.01072 1.16% 0.08128 -0.015 0.022 0.682
VSL 0.02458 1.79% 0.03418 -0.001 0.035 0.029
NMIA 0.07855 1.01% 0.10666 0.053 0.019 2.789
NIST 0.04653 1.32% 0.06320 0.021 0.025 0.840
VNIIOFI 0.02982 0.83% 0.11148 0.004 0.016 0.250
MKEH 0.03288 1.06% 0.08677 0.007 0.020 0.350
INM 0.12096 5.73% 0.00334 0.096 0.114 0.842
KRISS 0.00000 0.67% 0.24695 -0.025 0.011 2.273
Table 8-8. Comparison results for white LEDs after temperature correction.
participant Δi u(Δi) wi Di U(Di) En
MIKES 0.02358 1.91% 0.03484 0.005 0.037 0.135
CMS-ITRI -0.00047 2.18% 0.02657 -0.019 0.043 0.442
PTB 0.02087 1.24% 0.08203 0.002 0.024 0.083
NMIJ 0.01958 1.91% 0.03474 0.001 0.037 0.027
CENAM -0.18187 2.99% N.A. -0.201 0.060 3.350
LNE 0.02847 2.53% 0.01977 0.010 0.050 0.200
METAS 0.00373 1.07% 0.11121 -0.015 0.020 0.750
NMC-
A*STAR 0.01108 1.20% 0.08772 -0.008 0.023 0.348
VSL 0.02307 1.53% 0.05424 0.004 0.030 0.133
NMIA 0.05339 1.09% 0.10640 0.035 0.021 1.667
NIST 0.05157 1.40% 0.06463 0.033 0.027 1.222
VNIIOFI 0.00832 0.90% 0.10696 -0.010 0.017 0.588
MKEH 0.02303 1.13% 0.08459 0.004 0.022 0.182
INM 0.11145 5.62% 0.00402 0.093 0.112 0.830
KRISS 0.00000 0.83% 0.18228 -0.019 0.015 1.267
The DoEs and its uncertainties for white LEDs are plotted in Fig. 8-4 as dot symbols
and error bars, respectively. The red lines indicate the expanded relative uncertainty of
the comparison RV.
APMP.PR-S3a Averaged LED Intensity Final Report
151
Fig. 8-4. DoE for white LEDs without and with temperature correction.
8.5. Diffuser-type Green LEDs
The comparison RV for averaged LED intensity of diffuser-type green LEDs is calculated
to be 0.02219, 0.60% ( 2)RV rU k
for the results without temperature correction,
and 0.02068, 0.64% ( 2)RV rU k
for the results after temperature correction.
Table 8-9 and Table 8-10 summarize the comparison results for diffuser-type green LEDs
without and with temperature correction, respectively. The last column of each table
shows the En criteria of each participant, which is defined as the absolute ratio of Di and
APMP.PR-S3a Averaged LED Intensity Final Report
152
U(Di). Note that the results of CENAM and INM are identified as outliers and not
included in the calculation of the RV.
Table 8-9. Comparison results for diffuser-type green LEDs without temperature correction.
participant Δi u(Δi) wi Di U(Di) En
MIKES 0.02808 0.91% 0.10905 0.006 0.017 0.353
CMS-ITRI 0.01191 2.23% 0.01819 -0.010 0.044 0.227
PTB 0.01080 1.25% 0.05846 -0.011 0.024 0.458
NMIJ 0.02927 1.48% 0.04120 0.007 0.029 0.241
CENAM -0.12031 3.35% N.A. -0.143 0.067 2.134
LNE 0.05492 1.04% 0.08364 0.033 0.020 1.650
METAS 0.01437 1.25% 0.05819 -0.008 0.024 0.333
NMC-
A*STAR 0.01084 1.17% 0.06663 -0.011 0.023 0.478
VSL 0.02746 1.36% 0.04935 0.005 0.026 0.192
NMIA 0.02472 1.16% 0.06732 0.003 0.022 0.136
NIST 0.05872 1.22% 0.06076 0.037 0.024 1.542
VNIIOFI -0.00231 1.15% 0.05622 -0.025 0.023 1.087
MKEH 0.03739 0.76% 0.11945 0.015 0.014 1.071
INM 0.20781 5.59% N.A. 0.186 0.112 1.661
KRISS 0.00000 0.65% 0.21152 -0.022 0.012 1.833
Table 8-10. Comparison results for diffuser-type green LEDs after temperature correction.
participant Δi u(Δi) wi Di U(Di) En
MIKES 0.02318 1.06% 0.09758 0.002 0.020 0.100
CMS-ITRI 0.01012 2.29% 0.02078 -0.011 0.045 0.244
PTB 0.01398 1.06% 0.09758 -0.007 0.020 0.350
NMIJ 0.03155 1.39% 0.05672 0.011 0.027 0.407
CENAM -0.12663 3.43% N.A. -0.147 0.069 2.130
LNE 0.05055 1.17% 0.07937 0.030 0.022 1.364
METAS 0.01099 1.27% 0.06730 -0.010 0.025 0.400
NMC-
A*STAR 0.01312 1.25% 0.07022 -0.008 0.024 0.333
VSL 0.02514 1.40% 0.05580 0.004 0.027 0.148
NMIA 0.01235 1.20% 0.07347 -0.008 0.023 0.348
NIST 0.06197 1.31% 0.06353 0.041 0.025 1.640
VNIIOFI -0.00823 1.28% 0.05560 -0.029 0.025 1.160
MKEH 0.03532 0.92% 0.10164 0.015 0.018 0.833
INM 0.18510 5.69% N.A. 0.164 0.114 1.439
KRISS 0.00000 0.82% 0.16042 -0.021 0.015 1.400
The DoEs and its uncertainties for diffuser-type green LEDs are plotted in Fig. 8-5 as
dot symbols and error bars, respectively. The red lines indicate the expanded relative
uncertainty of the comparison RV.
APMP.PR-S3a Averaged LED Intensity Final Report
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Fig. 8-5. DoE for diffuser-type green LEDs without and with temperature correction.
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154
9. Discussion
9.1. Test of Consistency
In order to test the consistency of the comparison results, the Birge ratio RB is calculated
by the equation
2
RV
B 20 adj
1
( )
Ni
i i
RN u
, (9-1)
where N is the number of the participants, without counting the pilot, whose results are
used for the calculation of the RV. For this calculation, the data of the outliers are not
used. Note that the consistency is satisfied, if RB ≤ 1.
Table 9-1 shows the calculated Birge ratios of the comparison S3a without and with
temperature correction. The values of RB range from 1.4 to 2.4, which indicate that the
uncertainties of the participants are underestimated. Table 9-1 also shows that the
temperature correction has the effect of decreasing the Birge ratios and, hence,
improving the consistency. This verifies that the temperature correction based on the
junction voltage measurement described in Chapter 3 is capable to correct the
systematic errors of the artifact LEDs due to different measurement conditions.
Table 9-1. Birge ratio of the comparison S3a.
LED type Birge ratio
without T correction
Birge ratio after T
correction
Red 1.847 1.434
Green 1.714 1.738
Blue 2.409 2.247
White 1.992 1.465
Diffuse green 1.833 1.629
9.2. Accuracy of Alignment
As LEDs have a narrow angular distribution of emission, the mechanical alignment of
LEDs is known as one of the most critical components in practice affecting the
measurement accuracy of averaged LED intensity. In order to check this, the pilot
circulated the specially-designed diffuser-type green LED that shows a spatial angular
distribution being not sensitive to the alignment. Difference between the results for the
normal and diffuser-type green LEDs of each participant can give information if the
measurement of the participant contains any significant error in alignment. Table 9-2
shows the summary of the DoEs for the normal and diffuser-type green LEDs with their
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155
differences expressed in per cent.
Table 9-2. DoEs for the normal and diffuser-type green LEDs (after temperature correction).
participant DoE for normal
green LEDs
DoE for
diffuser-type
green LEDs
difference
MIKES 0.002 0.002 0.0%
CMS-ITRI -0.012 -0.011 0.1%
PTB 0.001 -0.007 -0.8%
NMIJ 0.019 0.011 -0.8%
CENAM -0.126 -0.147 -2.1%
LNE 0.030 0.030 0.0%
METAS -0.001 -0.010 -0.9%
NMC-A*STAR -0.002 -0.008 -0.6%
VSL 0.013 0.004 -0.8%
NMIA -0.063 -0.008 5.5%
NIST 0.036 0.041 0.5%
VNIIOFI -0.033 -0.029 0.4%
MKEH 0.026 0.015 -1.2%
INM 0.118 0.164 4.6%
KRISS -0.012 -0.021 -0.9%
9.3. Accuracy of Color Correction
The narrow spectral bandwidth of LEDs is another important source of systematic errors
in the photometric measurement of LEDs. If a photometer is used for LED measurements,
correction of spectral mismatch, often referred to as color correction, is essential to
achieve high accuracy, which requires both relative spectral distribution of the test LED
and relative spectral responsivity of the photometer. The technical reports of the
participants in Chapter 4 inform that every participant of the comparison S3a uses a
photometer and applies color correction. As we have circulated four different colors of
LEDs (R/G/B/W), analysis of the dependence of the comparison results upon the LED
colors can provide important information on the accuracy of color correction. Table 9-3
summarizes the DoEs of each participant for different colors of LEDs, which are based on
the temperature corrected data.
Table 9-3. DoEs for different LED colors (after temperature correction).
participant DoE for red
LEDs
DoE for green
LEDs
DoE for blue
LEDs
DoE for white
LEDs MIKES -0.001 0.002 0.021 0.005
CMS-ITRI -0.022 -0.012 -0.014 -0.019
PTB 0.003 0.001 -0.004 0.002
NMIJ -0.021 0.019 0.045 0.001
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CENAM -0.343 -0.126 -0.076 -0.201
LNE 0.020 0.030 0.008 0.010
METAS -0.028 -0.001 0.025 -0.015
NMC-A*STAR 0.007 -0.002 0.014 -0.008
VSL 0.006 0.013 0.010 0.004
NMIA 0.101 -0.063 -0.035 0.035
NIST 0.031 0.036 0.032 0.033
VNIIOFI 0.037 -0.033 -0.085 -0.010
MKEH -0.022 0.026 0.067 0.004
INM 0.082 0.118 0.123 0.093
KRISS -0.011 -0.012 0.000 -0.019
Fig. 9-1 shows plots of the data in Table 9-3. We classified the participants to three
groups. The first group shown on the top plot in Fig. 9-1 have only a weak (< 1 %)
dependence of DoE on the LED colors. The second group shown on the middle plot in
Fig. 9-1 have a moderate (2 % ~ 5 %) dependence of DoE on the LED colors. Especially,
the results of many participants have a maximum or a minimum for blue LEDs. The last
group shown on the bottom plot in Fig. 9-1 have a large (> 5 %) dependence of DoE on
the LED colors. The results of Table 9-3 and Fig. 9-1 can be useful for the participants to
investigate the unknown systematic errors in their color correction.
APMP.PR-S3a Averaged LED Intensity Final Report
157
Fig. 9-1. Plots of DoEs for different colors of LEDs (R, G, B, W). The participants are classified to three groups.
APMP.PR-S3a Averaged LED Intensity Final Report
158
10. Summary
The measurement of averaged LED intensity in the CIE-B condition is compared by
circulating five different types of artifact LEDs (red, green, blue, white, and diffuser-type
green) to 15 NMIs (including the pilot). The artifact LEDs are prepared by the functional
seasoning to enable a temperature correction based on the junction voltage
measurement. The comparison reference values and the unilateral degrees of equivalence
(DoEs) of each participant are calculated for each type of LEDs from the reported
measurement results. Table 10-1 shows the summary of the DoEs and their uncertainties
of each participant for each type of LEDs as the comparison result.
Table 10-1. Summary of the unilateral DoEs and their uncertainties for APMP.PR-S3a (temperature correction applied).
NMI
RED GREEN BLUE WHITE DIFFUSE
DoE U of
DoE DoE
U of
DoE DoE
U of
DoE DoE
U of
DoE DoE
U of
DoE
MIKES -0.001 0.039 0.002 0.040 0.021 0.042 0.005 0.037 0.002 0.020
CMS-ITRI -0.022 0.049 -0.012 0.044 -0.014 0.050 -0.019 0.043 -0.011 0.045
PTB 0.003 0.034 0.001 0.026 -0.004 0.037 0.002 0.024 -0.007 0.020
NMIJ -0.021 0.032 0.019 0.035 0.045 0.044 0.001 0.037 0.011 0.027
CENAM -0.343 0.062 -0.126 0.072 -0.076 0.068 -0.201 0.060 -0.147 0.069
LNE 0.020 0.032 0.030 0.027 0.008 0.035 0.010 0.050 0.030 0.022
METAS -0.028 0.028 -0.001 0.026 0.025 0.039 -0.015 0.020 -0.010 0.025
NMC-
A*STAR 0.007 0.029 -0.002 0.027 0.014 0.029 -0.008 0.023 -0.008 0.024
VSL 0.006 0.026 0.013 0.028 0.010 0.029 0.004 0.030 0.004 0.027
NMIA 0.101 0.043 -0.063 0.030 -0.035 0.031 0.035 0.021 -0.008 0.023
NIST 0.031 0.034 0.036 0.032 0.032 0.044 0.033 0.027 0.041 0.025
VNIIOFI 0.037 0.021 -0.033 0.034 -0.085 0.028 -0.010 0.017 -0.029 0.025
MKEH -0.022 0.024 0.026 0.024 0.067 0.032 0.004 0.022 0.015 0.018
INM 0.082 0.116 0.118 0.114 0.123 0.131 0.093 0.112 0.164 0.114
KRISS -0.011 0.018 -0.012 0.017 0.000 0.018 -0.019 0.015 -0.021 0.015
APMP.PR-S3a Averaged LED Intensity Final Report
159
Acknowledgement
The pilot work of this comparison is partly supported by the Korean Ministry of
Knowledge and Economy under the project of LED standardization, grant B0010209.
APMP.PR-S3a Averaged LED Intensity Final Report
160
Appendix A: Technical Protocol
The pdf-file can be opened by a double-click on the image below.
APMP.PR-S3a Averaged LED Intensity Final Report
161
Appendix B: Review of Relative Data
The pdf-file can be opened by a double-click on the image below.
APMP.PR-S3a Averaged LED Intensity Final Report
162
Appendix C: Comments from Review of Relative Data
The pdf-file can be opened by a double-click on the image below.
APMP.PR-S3a Averaged LED Intensity Final Report
163
Appendix D: Comments from Review of Uncertainty Budgets
The pdf-file can be opened by a double-click on the image below.
APMP.PR-S3a Averaged LED Intensity Final Report
164
Appendix E: Identification of Outliers
The pdf-file can be opened by a double-click on the image below.
APMP.PR-S3a Averaged LED Intensity Final Report
165
Appendix F: Comments and Revision to Draft A Report
Comments from PTB to Data Analysis
Results on 11 April 2011
Replies by the pilot on 17 June 2011
Enclosed please find copies of your files
with some marked blue cells. We think
there are some small bugs.
I have checked them and corrected. Thank
you!
It is possible to refer this comparison to
KCRV using link laboratories.
In principle yes. But the related KC, e.g. of
luminous flux, was done with a different
artifact so that it cannot be directly
compared to this LED comparison. That is
also the reason why this is a
supplementary comparison. We can try to
do such a linkage as an interesting study,
but not as a part of the comparison report.
The resulting excel graphic looks a little bit
strange. We feel is should look similar like
the following graphic (uDoE should be
plotted around DoE):
I agree and I checked that this is also
common for KCs. I will modify the graphs
as you suggest.
It may be helpful to calculate the Birge
ratio to get information about the
consistency of the comparisons. It is
calculated from the internal and external
This is a good suggestion. I will surely try
to calculate both the Birge ratio and the En
values and include the results in the final
report. This will provide valuable
APMP.PR-S3a Averaged LED Intensity Final Report
166
consistency. A value of close to 1 or less
indicates that the results are consistent.
Values greater than 1 are not.
in
extB
u
uR with
n
i
i
n
i
ii
Dun
DuD
u
1
2
1
2
ext
)()1(
)](/[
and
2/1
1
2
in )(
n
i
iDuu .
For luminous flux we found values around
2 for most cases. For luminous intensity
(without diffuse LEDs) we found values
around 1. Please see enclosed jpg files (I
apologize this jpg, but is takes a while to
get nice prints with mathematica). We also
calculated the criteria by
)(2Absin,
i
i
DoEu
DoEE
Values greater than 1 indicate a too small
uncertainty of the participant. So we
suggest to use specific enlargements of the
participant uncertainties in that way that
the Birge ratio is equal or less 1 and
criteria is close to 1. This procedure also
would solve the problem of outliers.
information to the next version of the KC
guidelines which should include a
procedure of consistency check and of a
better outlier selection.
Comments from PTB to Draft A Report
on 19 Oct 2011
Replies by the pilot on 22 Nov 2011
We found some typing errors in the draft
A paper. Enclosed please find our errata
ZIP-file.
I have checked the errors. But all the errors
you found were the corrections of the
uncertainty budgets of PTB. These,
however, cannot be corrected in the draft
A report stage, because they are already
APMP.PR-S3a Averaged LED Intensity Final Report
167
reviewed by the participants. This is
communicated via email on 21.10.2011.
PTB has acknowledged this and confirms
that these corrections do not affect the
comparison results. Therefore, the
corrections are not considered in the
revision of the draft A report.
The Plots Fig. 9-1 of S3a and S3b are very
helpful. It would be great to have these
plots for S3c, too.
In case of S3c, the plots such as Fig. 9-1 of
S3a and S3b were not easy because a 2
dimensional plot is required to make
systematic effects visible. I will try to realize
this in the next revision of the S3c report,
but I should also manage the workload.
Based on the results data, however, each
participant can make such analysis to
investigate the systematic effect of his
results.
The appendices should include all
important comments, suggestions and
recommendations of the participants to
simplify future comparisons. For example
our Suggestions PTB.docx of 15.04.2011.
I will make another appendix to record the
comments during the draft A report
procedure.
The tables in chapter 8 should include the
criteria
)(2Absin,
i
i
DoEu
DoEE
that would be helpful to evaluate the
stated uncertainty by each participants.
I will consider this in the revision.
The Birge ratios stated in table 9-1
especially for S3a and S3a are often
significant greater than 1. I think the
I agree that the large Birge ratio means
that the uncertainties of the participants
are underestimated. I wrote this also in the
APMP.PR-S3a Averaged LED Intensity Final Report
168
meaning of that is, that some stated
uncertainties are too small. Please, refer
the related En criteria.
Here we have an additional hint for that.
The first diagram from S3a (intensity)
shows a relative flat DoE around 0% of PTB
results. But the second diagram from S3b
(flux) shows relative big differences
between (R,G) and (B,W) LEDs. The
luminous flux values were determined by a
goniophotometer directly after the
luminous intensity measurement with the
same operation state of the LED and in the
same system without new alignment of the
LED. So there is no reason for that
difference. We know from hundreds of
measurements that the integration
capability of the goniophotometer has a
very high reproducibility.
So I think this a hint for an inconsistency
of the data as we know from the Birge
ratios.
report. Your statement will be documented
in the Appendix of the revised report.
APMP.PR-S3a Averaged LED Intensity Final Report
169
List of Revisions from A-1 to A-2
Draft A-1 Draft A-2
Page 121, section 5.4, the first line: “June ~
July 2008 (the exact dates not reported)”
Corrected to “from 16 June to 2 July 2008”
based on the result verification records.
Chapter 8, the first paragraph of each
section.
Addition of a sentence “The last column of
each table Table 8-2shows the En criteria of
each participant, which is defined as the
absolute ratio of Di and U(Di).”
Chapter 8, Table 8-1 ~ Table 8-10. Addition of a new column with the
calculated En criteria values.
After Chapter 10 Addition of <Acknowledgment> by the
pilot.
After Appendix E Addition of <Appendix F: Comments and
Revision to Draft A Report>
APMP supplementary comparison 1
Technical Protocol on
APMP Supplementary Comparisons of
LED Measurements
APMP.PR-S3a Averaged LED Intensity
APMP.PR-S3b Total Luminous Flux of LEDs
APMP.PR-S3c Emitted Colour of LEDs
Approved in January 2008, Revised in November 2008 due to change of participants list
Contents
1. INTRODUCTION........................................................................................................................................ 2
2. ORGANIZATION........................................................................................................................................ 2
2.1. CONDITION OF PARTICIPATION ............................................................................................................... 2 2.2. LIST OF PARTICIPANTS............................................................................................................................ 3 2.3. FORM OF COMPARISON ........................................................................................................................... 4 2.4. TIMETABLE............................................................................................................................................. 4 2.5. TRANSPORT AND HANDLING OF ARTEFACTS ........................................................................................... 6
3. DESCRIPTION OF ARTEFACTS ............................................................................................................ 7
4. MEASUREMENT INSTRUCTIONS ........................................................................................................ 9
4.1. AVERAGED LED INTENSITY (S3A) ......................................................................................................... 9 4.2. TOTAL LUMINOUS FLUX (S3B).............................................................................................................. 11 4.3. EMITTED COLOUR (S3C) ....................................................................................................................... 12
5. REPORTING OF RESULTS AND UNCERTAINTIES ........................................................................ 12
5.1. AVERAGED LED INTENSITY (S3A) ....................................................................................................... 12 5.2. TOTAL LUMINOUS FLUX (S3B).............................................................................................................. 13 5.3. EMITTED COLOUR (S3C) ....................................................................................................................... 13
6. PREPARATION OF COMPARISON REPORT.................................................................................... 14
APPENDIX 1: INSPECTION REPORT ON RECEIPT OF ARTEFACTS................................................. 15
APPENDIX 2: RESULT REPORT OF AVERAGED LED INTENSITY (S3A).......................................... 16
APPENDIX 3: RESULT REPORT OF TOTAL LUMINOUS FLUX (S3B) ................................................ 17
APPENDIX 4: RESULT REPORT OF EMITTED COLOUR (S3C) ........................................................... 18
Technical protocol on comparison of LED measurements
APMP supplementary comparison 2
Technical protocol on comparison of LED measurements
1. INTRODUCTION
Under the Mutual Recognition Arrangement (MRA), the metrological equivalence of national measurement standards will be determined by a set of key comparisons chosen and organized by the consultative committees of CIPM working closely with regional metrology organizations (RMOs). In addition, RMOs can organize supplementary comparisons which should be carried out in the same procedure as that of key comparisons following the guidelines established by BIPM1.
At its meeting in December 2006, Asia Pacific Metrology Programme (APMP) Technical Committee of Photometry and Radiometry (TCPR) proposed several regional comparisons in the field of optical radiation metrology. One of those, a set of photometric quantities of light-emitting diodes (LEDs) has been agreed to be conducted with Korea Research Institute of Standards and Science (KRISS) of Republic Korea as the pilot institute. It is also decided that APMP TCPR invites the institutes of other RMOs to participate this supplementary comparison.
In March 2007, the first invitation to participate is distributed to the members of Consultative Committee of Photometry and Radiometry (CCPR) of CIPM by the chairperson of APMP TCPR. Based on the responses to this invitation, a provisional list of participants is prepared.
Three measurement quantities of LEDs are selected for the comparison, which are listed as service categories for Calibration and Measurement Capabilities (CMCs): averaged LED intensity defined by International Commission on Illumination (CIE), total luminous flux of LEDs, and emitted colour of LEDs expressed as chromaticity coordinates (x, y) according to the CIE 1931 standard colorimetric system.2
It should be noted that total luminous flux is the measurement quantity for CCPR-K4. The current supplementary comparison of total luminous flux of LEDs is, however, not to be linked to this KC, but can be regarded as a pilot study testing the suitability of LEDs as an alternative artefact for CCPR-K4.
This document is to treat the technical protocol for the comparison of LED measurements, and has been prepared by KRISS and agreed by all the participants on the preliminary list.
2. ORGANIZATION
2.1. CONDITION OF PARTICIPATION
KRISS is acting as the pilot institute in the comparison among the participants.
Three comparisons for three measurement quantities are conducted simultaneously by circulating one artefact set. The participant can decide to take part in only one or two of the three comparisons by selecting the measurement quantities. However, it should be declared with the confirmation of participation and stated in the technical protocol.
All the participants must be able to demonstrate traceability to an independent realization of each quantity, or make clear the route of traceability via another named laboratory.
By their declared intention to participate in this comparison, the laboratories accept the general instructions and the technical procedures written down in this document and commit themselves to follow the procedures strictly.
1 Guidelines for CIPM Key Comparisons, March 1999 (modified in October 2003). Available at http://www.bipm.fr/en/convention/mra/guidelines_kcs/ 2 Measurement of LEDs, CIE Technical Report 127-1997.
APMP supplementary comparison 3
Technical protocol on comparison of LED measurements
Once the protocol has been agreed, no change to the protocol may be made without prior agreement of all the participants.
2.2. LIST OF PARTICIPANTS
(Nr.) NMI
country contact person email address post address participating comparisons
(1) KRISS
Rep. Korea Seongchong
Park, Dong-Hoon Lee
[email protected] [email protected]
Division of Physical Metrology Korea Research Institute of Standards
and Science 1 Doryong-Dong, Yuseong-Gu Daejeon 305-340, Rep. Korea
all (S3a, S3b,
S3c)
(2)3 NMC-
A*STAR Singapore
Yuanjie Liu, Gan Xu
Optical Metrology Department National Metrology Centre
1 Science Park Drive Singapore 118221
all
(3) MIKES
Finland Pasi Manninen [email protected]
Metrology Research Institute Helsinki University of Technology
P.O.Box 3000 FI-02015 TKK, Finland
all
(4) NIST
USA Cameron Miller,
Yoshi Ohno Yuqin Zong
[email protected]@nist.gov
Optical Technology Division National Institute of Science and
Technology 100 Bureau Drive, Mailstop 8442
Gaithersburg, MD 20899-8442, USA
all
(5) CMS-ITRI
Chinese Taipei
Cheng-Hsien Chen
CMS/ITRI Rm. 301, Bldg. 16, 321, Sec. 2,
Kuang Fu Rd. Hsinchu, Taiwan 300, R.O.C.
all
(6) PTB
Germany Matthias
Lindemann Robert Maass
Physikalisch-Technische Bundesanstalt
AG 4.15, Goniophotometrie Bundesallee 100,
D-38116 Braunschweig, Germany
all
(7) CENAM
Mexico
Laura P. González, Anayansi Estrada,
Eric Rosas
[email protected]@[email protected]
División de Óptica y Radiometría Centro Nacional de Metrología
km 4,5 Carretera a Los Cués 76241, El Marqués, Querétaro,
México
all
(8)
NMIJ Japan
Kenji Godo, Terubumi Saito
[email protected] [email protected]
Optical Radiation Section Photometry and Radiometry Division
National Institute of Advanced Industrial Science and Technology 1-1-1, Umezono, Tsukuba, Ibaraki,
JAPAN 305-8563
all
(9) METAS
Switzerland Peter Blattner Peter.Blattner@metas
.ch
Federal Office of Metrology Lindenweg 50, 3003 Bern-Wabern
Switzerland all
(10) NPL
UK Paul Miller, Nigel Fox
National Physical Laboratory Hampton Road, Teddington, Middx,
TW11 0LW, UK all
(11) LNE
France Jimmy Dubard [email protected]
Laboratoire National de Métrologie et d’Essais
29, avenue Roger Hennequin 78197 TRAPPES, FRANCE
all
3 Formerly SPRING
APMP supplementary comparison 4
(12) NMi VSL
The Netherlands
Eric W.M. van der Ham, M.Charl
Moolman
[email protected]@NMi.nl
NMi Van Swinden Laboratorium B.V. Department Electricity, Radiation and
Length Section Optics Thijsseweg 11, 2629 JA Delft
Zuid-Holland, The Netherlands
all
(13) NMIA
Australia Philip Lukins Philip.Lukins@measu
rement.gov.au
National Measurement Institute of Australia
2 Bradfield Rd Lindfield, NSW 2070, Australia
all
(14) VNIIOFI
Russia Tatiana
Gorshkova [email protected]
All-Russian Research Institute for Optical and Physical Measurements
Ozernaya 46 119361 Moscow, Russia
all
(15) MKEH
Hungary George Andor [email protected]
Magyar Kereskedelmi és Engedélyezési Hivatal (MKEH)
Németvölgyi út 37-39 H-1124 Budapest XII.
Hungary
all
(16) INM
Romania Mihai
Simionescu mihai.simionescu@in
m.ro
Institutul National de Metrologie Sos. Vitan Barzesti nr.11, Sector 4
Bucharest, Romania all
2.3. FORM OF COMPARISON
The comparison is carried out by distributing 8 sets of the artefact standard LEDs prepared and provided by the pilot. Each set of the artefact LEDs contains 14 pieces of LED, consisting of 12 lamp-type, 5-mm diameter LEDs (3 x Red, 3 x Green, 3 x Blue, 3 x White) and 2 specially-designed diffuser-type green LEDs. The specifications, preparation, and characteristics of the standard LEDs are described in Chapter 3.
The comparison runs as a star-type. The pilot sends to each participant one set of the artefact LEDs after preparation and characterisation. The participant measures (1) the averaged LED intensity in the CIE condition B, and/or (2) the total luminous flux, and/or (3) the chromaticity coordinate CIE1931 (x,y) of every artefact LEDs according to the introductions described in Chapter 4. After the measurement, the participant sends the artefact set back to the pilot, who characterises it again to check out a possible drift or change. The measurement results should be reported to the pilot as soon as possible after the measurement is finished according to the guidelines in Chapter 5.
The timetable given below shows an overview on how the comparison is to be preceded. Since the preparation of the artefact LEDs takes much time (over 300 hours) due to seasoning process, the pilot requires at least one month preparing the artefact LEDs ready for delivery. The pilot tries to provide as many artefact sets as possible so that the circulation runs without significant loss of time (multiple star-type circulation).
Each participant has two months for measurement after the receipt of the artefact set. With its confirmation to participate, each participant has confirmed that it is capable of performing the measurements in the time allocated to it. If anything happens so that it can not meet the timetable, the participant must contact the pilot immediately.
2.4. TIMETABLE
Time Activity of pilot Activity of participants
July 2007 ~ January 2008
- Preparation of artefact sets (#1 ~ #8) - Preparation of technical protocol draft
- Review of technical protocol draft
Technical protocol on comparison of LED measurements
APMP supplementary comparison 5
January 2008 - Finalization and approval of technical protocol by APMP TCPR
February 2008
- Control measurement of artefact set #1 and #2
- Delivery of artefact set #1 to MIKES - Delivery of artefact set #2 to CMS-ITRI
March 2008
- Control measurement of artefact set #3 and #4
- Delivery of artefact set #3 to PTB - Delivery of artefact set #4 to NMIJ
- Receipt of artefact set #1 in MIKES, Finland
- Receipt of artefact set #2 in CMS-ITRI, Taiwan
April 2008
- Control measurement of artefact set #5 and #6
- Delivery of artefact set #5 to CENAM- Delivery of artefact set #6 to LNE
- Receipt of artefact set #3 in PTB, Germany
- Receipt of artefact set #4 in NMIJ, Japan
May 2008
- Control measurement of artefact set #7 and #8
- Delivery of artefact set #7 to METAS - Delivery of artefact set #8 to NMC-A*STAR
- Receipt of artefact set #5 in CENAM, Mexico
- Receipt of artefact set #6 in LNE, France
- Return of artefact set #1 and #2 to KRISS (MIKES, CMS-ITRI)
June 2008
- Control measurement of artefact set #1 and #2
- Delivery of artefact set #1 to NMi-VSL
- Delivery of artefact set #2 to NMIA
- Receipt of artefact set #7 in METAS, Switzerland
- Receipt of artefact set #8 in NMC-A*STAR, Singapore
- Return of artefact set #3 and #4 to KRISS (PTB, NMIJ)
July 2008
- Control measurement of artefact set #3 and #4
- Delivery of artefact set #3 to NIST - Delivery of artefact set #4 to NPL
- Receipt of artefact set #1 in NMi-VSL, The Netherlands
- Receipt of artefact set #2 in NMIA, Australia
- Return of artefact set #5 and #6 to KRISS (CENAM, LNE)
August 2008
- Control measurement of artefact set #5 and #6
- Delivery of artefact set #5 to VNIIOFI- Delivery of artefact set #6 to MKEH
- Receipt of artefact set #3 in NIST, USA
- Receipt of artefact set #4 in NPL, UK
- Return of artefact set #7 and #8 to KRISS (METAS, NMC-A*STAR)
September 2008 - Control measurement of artefact set #7 and #8
- Receipt of artefact set #5 in VNIIOFI, Russia
- Receipt of artefact set #6 in MKEH, Hungary
- Return of artefact set #1 and #2 to KRISS (NMi-VSL, NMIA)
October 2008 - Control measurement of artefact set #1 and #2
- Delivery of artefact set #7 to INM
- Return of artefact set #3 and #4 to KRISS (NIST, NPL)
Technical protocol on comparison of LED measurements
APMP supplementary comparison 6
November 2008 - Control measurement of artefact set #3 and #4
- Return of artefact set #5 and #6 to KRISS (VNIIOFI, MKEH)
- Receipt of artefact set #7 in INM, Romania
December 2008
- Control measurement of artefact set #5 and #6
- Control measurement of artefact set #7
- Return of artefact set #7 to KRISS (INM)
January 2009 ~ April 2009
- Pre-Draft A process 1: distribution of uncertainty budget - Pre-Draft A process 2: review of relative data
May 2009 ~ June 2009
- Draft A report: preparation and distribution
July 2009 ~ August 2009
- Draft A report: review and approval by the participants
Sept. 2009 ~ October 2009
- Draft B report: preparation and submission to TCPR (Or Draft A-2 report process, if required)
2.5. TRANSPORT AND HANDLING OF ARTEFACTS
Each set of 14 artefact LEDs is transported in a wooden box (size 90 cm x 90 cm x 80 cm) with conductive foam matting, where the LEDs are pinned down at the specified positions. Packaging of the box should be sufficiently robust to be sent by courier, but precautions must be taken to prevent any damage by mechanical impact, heat, water, and moisture. The artefact set will be accompanied by a suitable customs carnet (where appropriate) or documentation identifying the items uniquely.
Each participating laboratory covers the cost for its own measurements, transportation and any customs charges as well as for any damages that may have occurred within its country.
The artefact LEDs should be visually inspected immediately upon receipt. However, care should be taken to ensure that the LEDs have sufficient time to acclimatise to the laboratory environment thus preventing any condensation, etc. The condition of the artefact LEDs and associated packaging should be noted and communicated via email and fax to the pilot by using the form APPENDIX 1: INSPECTION REPORT ON RECEIPT OF ARTEFACTS.
The artefact LEDs should be handled only by the authorized persons, who are well aware of the cautions stated in the manufacturer’s specification sheets of the artefact LEDs.
LEDs can be damaged by static electricity or surge voltage. Using an anti-static wrist band is strongly recommended. When the LEDs are not installed for measurement, they should always be kept at the specified positions on the conductive foam matting in the package box, which prevents not only electrostatic and mechanical damages but also confusion in identifying each LED.
The LEDs should never be touched with bare hands. Please use an anti-static vinyl glove in handling the LEDs. No cleaning of LEDs should be attempted except using dry air.
The mechanical condition of the LEDs should never be changed by actions such as soldering, cutting, polishing, and bonding.
If an artefact LED is damaged or shows any unusual property during operation, the operation should immediately be terminated and the pilot should be contacted.
After measurement, the artefact LEDs should be repackaged as received. Ensure that the content of the package is complete before shipment.
Technical protocol on comparison of LED measurements
APMP supplementary comparison 7
Technical protocol on comparison of LED measurements
3. DESCRIPTION OF ARTEFACTS
The artefact LEDs are prepared from the commercially available “raw” LEDs in the following procedure:
1. Seasoning: the raw LEDs are pre-burned for more than 300 hours while the temporal change of their electrical and optical properties are recorded. The temporal drift and the temperature dependence of the optical characteristics of each LED are determined during the seasoning process.
2. Selection: based on the seasoning characteristics, the LEDs with predictable seasoning characteristics are selected as the artefact LEDs for the comparison.
3. Test measurement: the photometric quantities of the artefact LEDs are measured by the pilot before sent to each participant. The measurement by the pilot is repeated when the artefacts are received back from the participant after the measurement. If the measured drift of an artefact is greater than expected from the seasoning, it should be replaced by another seasoned LED of the same type for the next measurement round.
The “raw” LEDs used in this comparison are manufactured by Nichia Corporation.4 The selected models are listed in the following table with the specifications provided by the manufacturer (pdf-files included).
colour model initial characteristics in specifications
(forward current 20 mA, 25 ºC) specification sheets (file)
RED NSPR518S
forward voltage 2.2 V luminous intensity 1 cd dominant wavelength 625 nm spectral bandwidth 15 nm (FWHM) angular directivity 50º (FWHM)
Adobe Acrobat 7.0 Document
GREEN NSPG518S
forward voltage 3.5 V luminous intensity 2 cd dominant wavelength 525 nm spectral bandwidth 40 nm (FWHM) angular directivity 40º (FWHM)
Adobe Acrobat 7.0 Document
BLUE NSPB518S
forward voltage 3.6 V luminous intensity 0.6 cd dominant wavelength 470 nm spectral bandwidth 30 nm (FWHM) angular directivity 40º (FWHM)
Adobe Acrobat 7.0 Document
WHITE NSPW515BS
forward voltage 3.6 V luminous intensity 0.7 cd chromaticity near x = 0.31, y = 0.32 angular directivity 70º (FWHM)
Adobe Acrobat 7.0 Document
The mechanical dimensions are the same for every raw LED as summarized below. The detailed drawing of the LEDs can be found in the specification sheets.
- lamp diameter: 5 mm (diffusion type, epoxy resin mold)
- lamp base diameter: 5.6 mm (LED’s outer diameter)
- lamp length (length of the lamp part with diameter ≤ 5 mm): 7.3 mm
4 More information on the LEDs available at http://www.nichia.co.jp/
APMP supplementary comparison 8
Technical protocol on comparison of LED measurements
- wire length (measured from backside of lamp): 20.3 mm for cathode, 22.3 mm for anode
- wire thickness: 0.5 mm
- wire distance: 2.5 mm
In the seasoning process, the relative luminous intensity and spectral distribution of each LED is recorded together with its junction temperature as a function of time for burning time of longer than 300 hours, while the ambient temperature is periodically varied from 18 ºC to 33 ºC. From the recorded data, the temperature dependence and the slow-varying drift characteristics of the LED’s photometric and colorimetric quantities can be separately determined.5 The pilot keeps and uses the measured data and characteristics of each artefact LED during the seasoning, first, to monitor and compensate the temperature effect of the measurands and, second, to control if the drift of the artefact LEDs occurred during the comparison is within the expected range. Note that the record of the junction voltage with the comparison measurands for each artefact LED is essential for this purpose.
Since the mechanical alignment of a LED is known as one of the most critical components affecting the measurement accuracy of averaged LED intensity, the pilot circulates, in addition to the 12 standard-type artefact LEDs, two samples of a specially-designed diffuser-type LED that shows a spatial emission distribution being not sensitive to the alignment. This diffuser-type artefact LED is constructed by putting a green LED (NSPG518S) into a cylinder-type cap with an opal diffuser, as shown in Fig. 1, and should provide a possibility to analyze the result of the comparison. Note, however, that this diffuser-type artefact LEDs are not used in the measurement of total luminous flux.
Fig. 1 Schematic drawing of a diffuser-type artefact LED.
One artefact set finally contains 14 artefact LEDs, and the pilot prepares and circulates 8 different sets for the 14 participants. Each participant receives and measures one among these artefact sets according to the timetable in Section 2.4. Each artefact set is identified with a serial number (set #1, set #2, etc.) and the 14 LEDs in one set is identified and positioned in a package box as shown in Fig. 2. Note that one artefact LED is uniquely identified in a form #N-X-M with three codes: (1) #N as artefact set number (N = 1, 2, …, 8), (2) X as LED colour and type code (X = R for red, G for green, B for blue, W for white, D for diffuser-type), and (3) M as sample serial number for each type (M = 1, 2, 3). As the individual LED could not be indicated by writing the full identification code on the LED due to the small size, only the sample number M of each LED is marked on the wires according to the colour code as shown in the right-hand part of Fig. 2.
5 Seongchong Park et al., Metrologia 43, 299 (2006); Proc. SPIE 6355, 63550G-1 (2006)
13.5 mm
8.3 mm
diffuser diameter 8.3 mm
[side view] [front view]
APMP supplementary comparison 9
Technical protocol on comparison of LED measurements
Fig. 2 Identification of individual LEDs in the box of one artefact set.
4. MEASUREMENT INSTRUCTIONS
4.1. AVERAGED LED INTENSITY (S3A)
The averaged LED intensity (unit: cd) of each artefact LED is to be measured in the standard condition B defined by CIE, as depicted in Fig. 3. 6 Either an illuminance meter or a spectroradiometer is used as the detector measuring the illuminance Ev for a circular area with size A = 100 mm2 at a distance d = 100 mm from the front tip of the LED. This is also valid for the diffuser-type LEDs with a flat front tip (see Fig. 1).
Fig. 3 Measurement condition for averaged LED intensity (CIE standard condition B).
The LED should be mounted so that the geometric axis of the LED is aligned to coincide with the normal of the reference plane of the detector head at the centre of the aperture area. The geometric axis of a LED is defined as the axis of rotational symmetry of the LED lamp cap,
6 Measurement of LEDs, CIE Technical Report 127-1997.
R-1 R-2 R-3
G-1 G-2 G-3
B-1 B-2 B-3
D-1 D-2
[wire marking]
- black for X-1
- red for X-2
- blue for X-3
(X = R/G/B/W/D)
W-1 W-2 W-3
Detector head
distance d
d = 100 mm ( = 0.01 sr)
circular aperture with size A =100 mm2
APMP supplementary comparison 10
which, in general, does not coincide with the optical axis of the light emission, as depicted in Fig. 4. Each participant may use a different method to achieve the target alignment condition with high reproducibility. For instance, one can confirm the target alignment condition by visually inspect the LED from the detector head position to check the rotational symmetry of the cap, as shown in Fig. 5.
optical axis
Technical protocol on comparison of LED measurements
Fig. 4 Definition of the geometric axis of a LED used for alignment to measure its averaged LED intensity.
Fig. 5 Inspection of alignment for the averaged LED intensity measurement by viewing the LED from the detector head position using a camera.
The LED should be mounted so that the backward emission, i.e. radiation emitted from the LED back surface to the direction of the connection wires, does not contribute to the detector signal. For this purpose, it is recommended to design the LED holder so that the backward emission is effectively scattered out of the measurement axis and blocked by a baffle.
The measurement should be performed by applying a constant forward current of 20 mA at an ambient temperature as close as 25 ºC for every artefact LED. In order to determine the junction temperature of the LED, the junction voltage between the anode and cathode should be measured in a 4-wire connection and recorded simultaneously with the value of averaged LED intensity, as shown in Fig. 6.
geometric axis LED front tip
[side view] [front view]
LED lamp cap
well-aligned slightly tilted
APMP supplementary comparison 11
anode
cathode
current source
+
−
+
voltmeter
I = 20 mA
−
Fig. 6 Circuit diagram of the 4-wire connection used to measure the junction voltage of a LED while applying the forward current.
The measurement of averaged LED intensity and junction voltage should be performed after a warming-up time of longer than 5 minutes. The turn-on time and turn-off time of each measurement sequence should be recorded so that the total burning time of each artefact LED can be determined and reported.
The measurement should be repeated and reproduced so that its uncertainty can be evaluated with sufficient confidence.
4.2. TOTAL LUMINOUS FLUX (S3B)
The luminous flux integrated for the whole 4 direction (unit: lm) of each artefact LED is to be measured using either a goniophotometer or an integrating sphere. Note, however, that the two diffuser-type LEDs are excluded for the measurement of total luminous flux.
The LED should be mounted so that the contribution of the backward emission is properly included in the total luminous flux. For this purpose, it is recommended to mount the LED back surface as far as possible from the holder and to minimize the near-field absorption in the holder.
The measurement should be performed by applying a constant forward current of 20 mA at an ambient temperature as close as 25 ºC for every artefact LED. In order to determine the junction temperature of the LED, the junction voltage between the anode and cathode should be measured in a 4-wire connection and recorded simultaneously with the value of total luminous flux, as shown in Fig. 6.
The measurement of total luminous flux and junction voltage should be performed after a warming-up time of more than 5 minutes. The turn-on time and turn-off time of each measurement sequence should be recorded so that the total burning time of each artefact LED can be determined and reported.
The measurement should be repeated and reproduced so that its uncertainty can be evaluated with sufficient confidence.
Technical protocol on comparison of LED measurements
APMP supplementary comparison 12
Technical protocol on comparison of LED measurements
4.3. EMITTED COLOUR (S3C)
The chromaticity coordinate CIE1931 (x,y) of the emitted colour of each artefact LED is to be determined by measuring the spectral distribution in the geometric condition of averaged LED intensity as shown in Fig. 3.7
The measurement should be performed by applying a constant forward current of 20 mA at an ambient temperature as close as 25 ºC for every artefact LED. In order to determine the junction temperature of the LED, the junction voltage between the anode and cathode should be measured in a 4-wire connection and recorded simultaneously with chromaticity coordinate, as shown in Fig. 6.
The measurement of chromaticity coordinate and junction voltage should be performed after a warming-up time of more than 5 minutes. The turn-on time and turn-off time of each measurement sequence should be recorded so that the total burning time of each artefact LED can be determined and reported.
The measurement should be repeated and reproduced so that its uncertainty can be evaluated with sufficient confidence.
5. REPORTING OF RESULTS AND UNCERTAINTIES
5.1. AVERAGED LED INTENSITY (S3A)
The measurement results should be reported to the pilot via email and fax by using the form APPENDIX 2: RESULT REPORT OF AVERAGED LED INTENSITY (S3A) immediately after the measurement is finished.
In addition to the result report, the participant is requested to provide the pilot a technical report containing the information listed in the following. This free-form report should be sent to the pilot via email as a Microsoft Word file within one month after the completion of measurement.
- Measurement setup and instruments used
- Mounting and alignment method, including a picture of the LED holder
- Traceability of measurement
- Detailed uncertainty budget for averaged LED intensity including values, evaluation type, probability distribution, degree of freedom, and sensitivity coefficient of each uncertainty component
- Detailed uncertainty budget for junction voltage including values, evaluation type, probability distribution, degree of freedom, and sensitivity coefficient of each uncertainty component
In the uncertainty budgets of the technical report, the participant should state whether and how an uncertainty component is artefact-dependent.
The pilot requests the participants to explicitly include the following uncertainty components in the uncertainty budgets to analyze the critical contributions:
- Component due to axis alignment. Note that the sensitivity to both angular (tilting) and translational (centring) misalignment should be separately considered.
7 This corresponds to a solid angle of 0.01 sr with a detector aperture size of 100 mm2. In case, however, that the aperture size of the instrument cannot be 100 mm2, the emitted colour should be measured for a solid angle of 0.01 sr at an appropriate distance, and the uncertainty budget should include components due to the different geometric condition.
APMP supplementary comparison 13
Technical protocol on comparison of LED measurements
- Component due to current feeding accuracy.
- Component due to stray light in the optical bench. Note that the backward emission of the LED scattered from the LED holder/mount can also contribute to the stray light.
- Component due to spectral mismatch correction, when a filter-type illuminance meter is used. Note that the spectral quantities used for spectral mismatch correction can be strongly correlated.
- For junction voltage: component due to position of junction.8
5.2. TOTAL LUMINOUS FLUX (S3B)
The measurement results should be reported to the pilot via email and fax by using the form APPENDIX 3: RESULT REPORT OF TOTAL LUMINOUS FLUX (S3B) immediately after the measurement is finished.
In addition to the result report, the participant is requested to provide the pilot a technical report containing the information listed in the following. This free-form report should be sent to the pilot via email as a Microsoft Word file within one month after the completion of measurement.
- Measurement setup and instruments used
- Mounting and alignment method, including a picture of the LED holder
- Traceability of measurement
- Detailed uncertainty budget for total luminous flux including values, evaluation type, probability distribution, degree of freedom, and sensitivity coefficient of each uncertainty component
- Detailed uncertainty budget for junction voltage including values, evaluation type, probability distribution, degree of freedom, and sensitivity coefficient of each uncertainty component
In the uncertainty budgets of the technical report, the participant should state whether and how an uncertainty component is artefact-dependent.
The pilot requests the participants to explicitly include the following uncertainty components in the uncertainty budget to analyze the critical contributions:
- Component due to near-field absorption of backward emission
- Component due to current feeding accuracy.
- Component due to stray light, when a goniophotometer is used.
- Component due to spectral mismatch correction, when a filter-type illuminance meter is used. Note that the spectral quantities used for spectral mismatch correction can be strongly correlated.
- Component due to spatial correction, when an integrating sphere is used.
- For junction voltage: component due to position of junction.
5.3. EMITTED COLOUR (S3C)
The measurement results should be reported to the pilot via email and fax by using the form APPENDIX 4: RESULT REPORT OF EMITTED COLOUR (S3C) immediately after the measurement is finished.
8 That means an uncertainty component due to the different distance from the LED junction to the voltage measurement point.
APMP supplementary comparison 14
Technical protocol on comparison of LED measurements
In addition to the result report, the participant is requested to provide the pilot a technical report containing the information listed in the following. This free-form report should be sent to the pilot via email as a Microsoft Word file within one month after the completion of measurement.
- Measurement setup and instruments used
- Traceability of measurement
- Detailed uncertainty budget for chromacitycoordinates including values, evaluation type, probability distribution, degree of freedom, and sensitivity coefficient of each uncertainty component
- Detailed uncertainty budget for junction voltage including values, evaluation type, probability distribution, degree of freedom, and sensitivity coefficient of each uncertainty component
In the uncertainty budgets of the technical report, the participant should state whether and how an uncertainty component is artefact-dependent.
The pilot requests the participants to explicitly include the following uncertainty components in the uncertainty budget to analyze the critical contributions:
- Component due to axis alignment. Note that the sensitivity to both angular (tilting) and translational (centring) misalignment should be separately considered.
- Component due to current feeding accuracy.
- Component in calculating the chromaticity coordinate from the measured spectral distribution. Note that the spectral quantities used for calculation can be strongly correlated.
- For junction voltage: component due to position of junction.
6. PREPARATION OF COMPARISON REPORT
After the measurement schedule of every participant is completed, the pilot prepares the report of the comparisons according to the guidelines by CCPR.9
Since three comparisons are performed together by using one artefact LED set, three reports are to be separately prepared.
Before starting the Pre-Draft A process, the pilot will re-confirm its reception of the artefact sets, the measurement results, and the technical reports from every participant. If any result or report is missing until this time, the pilot will announce a deadline for re-submission. After this deadline, the pilot proceeds the report preparation only with the data submitted so far.
9 Guidelines for CCPR Comparison Report Preparation, Rev. 1 of March 2006. Available at http://www.bipm.org/utils/en/pdf/ccpr_guidelines.pdf
APMP supplementary comparison 15
Technical protocol on comparison of LED measurements
APPENDIX 1: INSPECTION REPORT ON RECEIPT OF ARTEFACTS
Has the artefact set package been opened during transit? (e.g. by Customs) …… Y / N
If Yes, please give details.
Is there any damage to the package box? …… Y / N
If Yes, please give details.
Are the 14 artefact LEDs inside the package box complete and properly fixed into the conductive
matting? …… Y / N
If No, please give details.
Are there any visible signs of damage to the artefact LEDs? …… Y / N
If Yes, please give details (e.g. scratches or contaminations on the lamp, bending of wires, etc).
Is the LED identification sheet prepared by the pilot found in the package? …… Y / N
Laboratory: ………………………………………………………………………………………………
Date: …………………………………………… Signature: ………………………………..……
APPENDIX 2: RESULT REPORT OF AVERAGED LED INTENSITY (S3A)
Artefact set number:
Measurement dates: from to
Laboratory condition: temperature ( ± ) ºC , relative humidity ( ± ) %
LED
measurement value of
averaged LED intensity (cd)
expanded uncertainty* of averaged LED intensity (cd)
measurement value of
junction voltage (V)
expanded uncertainty* of junction voltage
(V)
total burning time (min)
R-1
R-2
R-3
G-1
G-2
G-3
B-1
B-2
B-3
W-1
W-2
W-3
D-1
D-2
* estimated for a 95 % confidence level (normally with a coverage factor k = 2)
Laboratory: ………………………………………………………………………………………………
Date: …………………………………………… Signature: ………………………………..……
APPENDIX 3: RESULT REPORT OF TOTAL LUMINOUS FLUX (S3B)
Artefact set number:
Measurement dates: from to
Laboratory condition: temperature ( ± ) ºC , relative humidity ( ± ) %
LED
measurement value of total luminous flux
(lm)
expanded uncertainty* of total luminous
flux (lm)
measurement value of
junction voltage (V)
expanded uncertainty* of junction voltage
(V)
total burning time (min)
R-1
R-2
R-3
G-1
G-2
G-3
B-1
B-2
B-3
W-1
W-2
W-3
* estimated for a 95 % confidence level (normally with a coverage factor k = 2)
Laboratory: ………………………………………………………………………………………………
Date: …………………………………………… Signature: ………………………………..……
APPENDIX 4: RESULT REPORT OF EMITTED COLOUR (S3C)
Artefact set number:
Measurement dates: from to
Laboratory condition: temperature ( ± ) ºC , relative humidity ( ± ) %
measurement value of chromaticity
coordinate
expanded uncertainty* of
chromaticity coordinate LED
x y x y
measurement value of
junction voltage (V)
expanded uncertainty* of junction voltage (V)
total burning
time (min)
R-1
R-2
R-3
G-1
G-2
G-3
B-1
B-2
B-3
W-1
W-2
W-3
D-1
D-2
* estimated for a 95 % confidence level (normally with a coverage factor k = 2)
Laboratory: ………………………………………………………………………………………………
Date: …………………………………………… Signature: ………………………………..……
Summary of Comments in Review of Relative Data
VSL
Mail on Dec 14, 2009
Looking to the data of VSL we see a big instability for some of the LEDs. Can you tell me how
you are going to deal with this and what the effect will be for the KCRV values or final
presentation of the results?
Response of KRISS on Dec 22, 2009
I think the stability for the LEDs used for VSL is not so bad (all below 1 % drift). I propose to
average the LEDs of the same type (three of red, three of green, etc.) and take the instability as an
uncertainty component of the difference from the reference value. (There will be no KCRV and
DoE because these are supplementary comparisons.)
Of course, we will exclude particular LEDs which show bad stability based on the opinion and
agreement of the participant.
Mail on March 17, 2010
Looking to the remarks of the temperature correction data we are wondering if the inconsistence
for some of the data has to do with the measurement of the junction voltage. As I can remember
there was a relative large variation in voltage over the legs of the LEDs. So in some cases
depending on the position of the junction measurement this can affect the correction for
temperature. Of course one needs to take this variation into the uncertainty for the voltage
measurement at the junction but maybe some of the inconsistencies can be explained looking to
the uncertainty for junction measurements versus temperature correction and the variation of
junction voltage over the legs of the LEDs.
Response of KRISS on March 24, 2010
It is true that there is a change of junction voltage when the measurement position of the LED
electrodes changes. We have noticed this at the stage of the artefact preparation, and therefore
arranged that this variation due to the junction position should be checked and reported by each
participant as an uncertainty component of junction voltage.
Because we have all the sensitivity data of photometric quantity to junction voltage for each
artefact LED, we can analyze the inconsistency caused by the inaccurate measurement of junction
voltage. We will surely include this in the result report. From our experience, however, the
uncertainty of photometric quantities propagated from the uncertainty of junction voltage
measurement, including the junction position variation, was much lower than 0.5 %, which is the
principal accuracy limit of the temperature correction method via junction voltage.
METAS
Mail on Dec 15, 2009
I have no special observation.
Mail on Feb 10, 2010
I have no special comments in respect to our relative data except that applying the temperature
correction will increase non-consistency of our data. I’ve done this analysis for all participants (see
enclosed excel-file) and it is interesting to see that only for few laboratories the consistency
increases.
Response of KRISS on Feb 12, 2010
You showed that the consistency decreases after the temperature correction, i.e. the standard
deviation of all the relative data for a participant increases. I think this is reasonable because the
process of temperature correction contains also the uncertainty, which is the limitation of the
theoretical model for temperature correction via junction voltage. We estimate this uncertainty to
be less than 0.5 % (see our publication in Metrologia, 43, 299, 2006). Therefore, we expect that
the application of temperature correction unavoidably causes a slight decrease of the consistency
of the relative data. Based on your calculation, the standard deviations of the relative data lie, for
most of the participants, between 0.5 % and 1 % without temperature correction, but the
(absolute) change of them due to temperature correction remains much below 0.5 %. From this,
we can confirm the accuracy of the temperature correction method.
In addition, we could also see the validity of temperature correction in the change of the absolute
data (not published yet) that the consistency between the pilot and the participants clearly
increases after temperature correction.
MKEH
Mail on Jan 20, 2010
After the overview of the MKEH relative data of the comparisons APMP-S3a (averaged LED
intensity) we have two remarks:
The LED G1, which was strongly different, died after the MKEH measurement. So this diode does
not have remeasured value. It might be damaged before the MKEH measurement. We ask for
remove the data of this diode.
The LED B3, which was different as well, died after the MKEH measurement. So this diode does
not have remeasured value. It might be damaged before the MKEH measurement as well. We ask
for remove the data of this diode.
Mail on Feb 17, 2010
We accept the data you have sent. (with respect to S3c)
MIKES
Mail on Jan 21, 2010
Could we remove the W-1 LED from the both comparisons?
NIST
Mail on Jan 29, 2010
We think that the LED set measured by NIST was not so bad if KRISS' measurement results for R1
and R2 were reliable. So we want to confirm that the differences (shown in your relative data)
between the measurement results of R1 and R2 are acceptable to us.
NMIJ
Mail on Dec 28, 2009 (not delivered in time)
By the way, it is the matter of review of relative data, in order to estimate whether it is drift of
LEDs, I would like to know the information of total burning time of our artifact(set #4) including
measurement burning time in KRISS.
I know the burning time in our measurement, but I don't know it in KRISS.
In addition, I would like to know about the seasoning result of our artifact.
Unless KRISS clarifies these information, it is very difficult to judge against our result of relative
data whether it is a drift of LEDs or some issue.
Mail on Feb 19, 2010
I would like to request to remove the result of B-1, B-3, W-1 from our APMP.PR-S3a results. In
addition, I would like also to request to remove the result of W-1 from our APMP.PR-S3b results.
Because, I think that the change of those LED result is large.
ASTAR
Mail on Feb 23, 2010
Thanks for the relative data. We have reviewed the data. The data looks in order and we have not
further comments for the relative data of all three comparisons.
Summary of Comments in Review of Uncertainty Budgets
Part 1. General Comments and Revisions
INM (Romania)
Mail on April 02, 2010
As far as the INM reports are concerned, the uncertainty budgets for Green, Blue, White and
Diffuse LEDs were not included in the APMP PR S 3a and APMP PR S3b reports just because they
are very close to our uncertainty budgets for the Red LEDs so we thought not necessary to repeat
the almost exactly same figures. But do you think this is necessary or should we merely mention
this in the reports? Anyway, in order to comply I`ll revise and sent you our reports today, provided
it`s not already too late.
Here attached are our revised reports for APMP PR S3a and APMP PR S3b comparisons, incliding
the uncertainty budgets for all tipes of LEDs.
Please notice that changes only concerned the spectral correction factors for the various LEDs and
while the combined standard uncertainties were of about 5.5 %, the various spectral correction
factors induced quite small changes (less than +/- 0,5 %) in the combined uncertainties values.
That`s why, initially we only reported the uncertainty budgets for the red LEDs.
Response of KRISS on April 12, 2010
I have properly received your two documents including the uncertainty budgets for all color-types
of LEDs. The formats you sent me are ok.
Because your revision deals only with an addition of information, I see no problem to accept your
revision for the report. I will wait for a while for other revisions or corrections, and distribute the
revised files then.
METAS
Mail on April 15, 2010
Please find enclosed an update of our description of the uncertainty budget of the chromaticity
coordinates. I’m sorry to have it sent after your deadline. In the updated version I stated explicitly
uncertainty budgets for the 4 types of LEDs. It’s just to give more information, no value has been
changed.
I also would like to recall our worries in respect to the correlation of chromaticity coordinates (see
the attached file).
APMP.PR-S3 Correlation of chro
Response of KRISS on April 15, 2010
I have received your files well. I will revise the uncertainty review document for S3c and distribute
it again. (But I will wait for a while to collect the revisions also from other participants.)
I think that your suggestion of reporting the correlation can be discussed open. Do you agree to
forward your document directly to all the participants to ask for their opinions?
A*STAR
Mail on June 21, 2010
We found not error in the three files containing technical information and uncertainty budgets.
However we added a paragraph in section 10.3 (in red colour text) of the “uncertainty
budgets_S3b” to mention the absorption correction in integrating sphere calibration and
measurement. The modified file is attached.
All Participants (open discussion)
Mail from KRISS on May 10, 2010
I have a comment which is sent from METAS to all the participants. Peter agreed to discuss this
issue openly.
This deals with a suggestion that, for the uncertainty budgets of chromaticity coordinates (x, y) for
APMP-S3c, the correlation between u(x) and u(y) should be considered by submitting the
correlation coefficient u(x,y)/u(x)u(y). Please see also the attached letter from Peter.
I personally think that it is meaningful to compare also the correlation coefficients among the
participants. However, it may be difficult at this stage to make the report of the correlation
mandatory because we did not mention this in the technical protocol. What we can do instead is
to encourage the participants to voluntarily report the correlation analysis as far as possible. If we
have many volunteers, we can include this part in the comparison report. If we have only a few
participants reporting the correlation, we can prepare this issue to an extra publication.
I would like to ask first who can submit the results of the correlation coefficients for the
chromaticity coordinates as supplementary to the uncertainty budget report. (METAS surely, and
KRISS can also do it.)
Mail from PTB on May 12, 2010
Correlation (x,y): If needed we can add the correlation of (x,y). Please let us know what is the
decision.
Mail from A*STAR on June 21, 2010
Regarding the issue our response is that we cannot submit the correlation coefficients for the uncertainty of the chromaticity coordinates.
Communication from KRISS on June 21, 2010
Typical values of correlation coefficient r(x,y) = u(x,y)/u(x)u(y) are -0.69 for RED, +0.41 for GREEN, -
0.86 for BLUE, and +0.96 for WHITE. The values do not change much as the artifact set changes.
Part 2. Questions and Answers
KRISS
Question to KRISS on May 10, 2010
-S3a average LED intensity
What are the uncertainty of the axis alignment (angular, translational) and distance: expressed in °
and mm?
-S3c, chromaticity coordinates, red LED
For the red LED the main contribution of the uncertainty is given by the spectral straylight. Has
the data been corrected for straylight? Why the contribution for red is much large then for the
others (red x: 0.00148, blue x: 0.00032) and why x and y are so different (usually there is full
correlation for the chromaticity coordinates for red LEDs).
-S3c, chromaticity coordinates, wavelength
For the other LED’s the main contribution of the uncertainty is given by the wavelength accuracy.
It would be useful to know the absolute uncertainty of the wavelength scale (expressed in nm).
Have there been some spectral correlations taking to account in the analysis?
Answers from KRISS on June 21, 2010 -S3a average LED intensity What are the uncertainty of the axis alignment (angular, translational) and distance: expressed in ° and mm? Response: The standard uncertainty of angular axis alignment, translation axis alignment, and distance setting is 0.82°, 0.41 mm and 0.25 mm, respectively. For translational axis alignment, the uncertainty contribution has been revised such as 0.2 % for red (Other else remain the same). -S3c, chromaticity coordinates, red LED For the red LED the main contribution of the uncertainty is given by the spectral stray light. Has the data been corrected for stray light? Why the contribution for red is much large then for the others (red x: 0.00148, blue x: 0.00032) and why x and y are so different (usually there is full correlation for the chromaticity coordinates for red LEDs). Response: The spectral stray light of spectral data is not corrected. We estimated the spectral stray light as an uncertainty based on the spectrograph response under He-Ne laser illumination. Most of stray light readout is distributed around the laser wavelength except the in-band region, which means that the spectral stray light has a similar spectral distribution with the input illumination. Thus, the contribution of the stray spectrum on chromaticity is more or less proportional to that of the input illumination. While the stray spectrum gives more contribution to x in case of a red LED, the stray spectrum of a green LED and a blue LED give more contribution to y and z, respectively. In our calculation, the correlation coefficient r(x, y) of a red LED turned out to -0.69. -S3c, chromaticity coordinates, wavelength For the other LED’s the main contribution of the uncertainty is given by the wavelength accuracy. It would be useful to know the absolute uncertainty of the wavelength scale (expressed in nm). Have there been some spectral correlations taking to account in the analysis? Response: The standard uncertainty of wavelength scale is (0.45 ~ 0.48) nm depending on wavelength. Of the uncertainty,
0.2 nm is a global wavelength offset, which mainly contributes on the chromaticity uncertainty. The spectral correlations are taken account in.
MIKES
Question to MIKES on May 10, 2010
-S3a average LED intensity
The uncertainty is by far dominated by the repeatability of the measurement. What is the origin of
this? Were measurement noisy? In the case of the diffuse type LED this contribution is smaller
than for the other type. Is it related to the geometry of the source? Is it really repeatability and
not reproducibility (i.e. were the LED realigned?)?
-S3b, luminous flux
The most important contribution (expect for the blue LED) originates from the near field
absorption (1%, with rectangular distribution!). How this value has been determined?
-S3c, chromaticity coordinates, white LED, angular alignment
The uncertainties of the chromaticity coordinates of the white LED are much higher than the other
coloured LEDs (except to the one with diffuser). The main contribution seems to be originated for
the angular alignment, although the sensitivity coefficient of that quantity seems to be the similar.
What is the origin of this?
-S3c, chromaticity coordinates, green LED
The uncertainty of the green LED with diffuser is dominated by the noise. How this contribution
has been determined as it as of Type B with rectangular probability? Usually noise contributions
are included in the repeatability of the measurement (Type A).
Answers from MIKES on May 31, 2010 > /-S3a average LED intensity / > > The uncertainty is by far dominated by the repeatability of the > measurement. What is the origin of this? Were measurement noisy? In > the case of the diffuse type LED this contribution is smaller than for > the other type. Is it related to the geometry of the source? Is it > really repeatability and not reproducibility (i.e. were the LED > realigned?)? > Answer: The uncertainty of repeatability originates mainly from the alignment accuracy of the measurement setup, i.e. the realignment of the LED before each repeat measurement. For the diffuser type of LEDs, the uncertainty due to the alignment was not found as sensitive as for the other type of LEDs. This could be partly explained by the optical properties of the measured LEDs. The LEDs without diffusing output may have nonuniform structure in the light output. > > /-S3b, luminous flux/ > > The most important contribution (expect for the blue LED) originates
> from the near field absorption (1%, with rectangular distribution!). > How this value has been determined? > Answer: The uncertainty of the near field absorption (type B) was estimated by considering the geometry and materials used in the LED holder and the amount of light emitted backward by the measured LEDs. > /-S3c, chromaticity coordinates, white LED, angular alignment/ > > The uncertainties of the chromaticity coordinates of the white LED are > much higher than the other coloured LEDs (except to the one with > diffuser). The main contribution seems to be originated for the > angular alignment, although the sensitivity coefficient of that > quantity seems to be the similar. What is the origin of this? > Answer: In the case of white LEDs, the spectral output may change as a function of angle of observation due to the phosphor coating. Therefore they are more sensitive to the alignment than the other type of LEDs. > /-S3c, chromaticity coordinates, green LED/ > > The uncertainty of the green LED with diffuser is dominated by the > noise. How this contribution has been determined as it as of Type B > with rectangular probability? Usually noise contributions are included > in the repeatability of the measurement (Type A). > Answer: The uncertainty of the diffuser type of LED was obtained by calculating the color coordinates for the original measurement data and for another data, in which the noise of the low signal values was replaced with extrapolated modelled values of the measured LED spectrum.
CMS-ITRI
Question to CMS-ITRI on May 10, 2010
-S3a average LED intensity, LED spatial light distribution
Why the quantity “LED spatial light distribution” is the same for all type of LEDs even the spatial
distribution is very different for the different LEDs (in particular the one with diffuser to the one
without diffuser)
-S3a average LED intensity, red LED,
The uncertainty of the spectral mismatch correction seems to be exceptionally small for the red
LED in respect to the other colours. What is the f1’ of the photometer?
-S3c, chromaticity coordinates, red LED
The uncertainty of the “x” - chromaticity coordinate of the red LED is dominated by two
contributions (repeatability :0.0015 and mechanical alignment: 0.0014). Why the combined
uncertainty is only 0.0014?
-S3c, chromaticity coordinates, mechanical alignment
why the uncertainty contribution due to mechanical alignment is the same for all type of LEDs? Is
there an evidence that a misalignment causes the same amount of shift in colour coordinates?
-S3c, chromaticity coordinates, green LED and green LED with diffusor
why the contribution of the wavelength shift of the green LED with diffusor is much higher than
the green LED without diffuser (more than 20x), the spectral distribution of both type of LEDs
being very similar?
PTB
Question to PTB on May 10, 2010
-S3a average LED intensity
It would be interesting to know the area of the sensitive surface of the photometer head, and in
the case that it is different to 100mm2 how that results were corrected.
-S3a average LED intensity, Correction for LED angular align,
Why the uncertainty due to the correction for angular alignment of the blue LED (0.57%) is much
larger than for the other LEDs (green: 0.11%) although the spatial distribution of is very similar?
-S3b, luminous flux, Integrated photocurrent, solid angle weighted
The most important contribution of uncertainty is originated from the quantity “Integrated
photocurrent, solid angle weighted”. It would be useful to have further information about this
quantity (i.e. eventl. citation). How it has been determined?
-S3c, chromaticity coordinates, red LED
The uncertainty of the chromaticity coordinates of the red LED is mainly given by the spectral
bandpass correction and the straylight correction of the spectrometer. There is however no
information about the amount of correction that has been applied and the spectrometer used for
the measurement(bandpass, wavelength accuracy, level of straylight,…)
-There is no information about the uncertainty contributions (input quantities and their
uncertainties) used in the Monte Carlo simulation.
Answers from PTB on May 12, 2010 Here are the answers of PTB concerning some questions of a participant: -S3a average LED intensity It would be interesting to know the area of the sensitive surface of the photometer head, and in the case that it is different to 100mm2 how that results were corrected. PTB: According to CIE Pub. 127 in all cases (S3a, S3b and S3c) the sensitive area of photometers or spectrometer input optics were 100 mm2. So no corrections for a different sensitive area were applied.
-S3a average LED intensity, Correction for LED angular align, Why the uncertainty due to the correction for angular alignment of the blue LED (0.57%) is much larger than for the other LEDs (green: 0.11%) although the spatial distribution of is very similar? PTB: From goniophotometric luminous flux measurements we know the spatial distribution of all LEDs. Especially the spatial distribution of green and blue LEDs are not similar in the interesting range of approx. 0° < ϑ < 2.5° ! Please, see figures below (on the left: example of green LED, on the right: example of blue LED). We describe the spatial distribution with cos[ϑ]g. In case of the green LED we found g=8.9 and in case of the blue LED we found g=39. Please, compare blue plots.
Now we are able the estimate the uncertainty contribution of angular alignment and translational alignment of the LED for luminous intensity measurements by help of a mathematical simulation. The figure below on the left shows a LED aligned in front of a photometer. The angular and aerial responsivity oft he photometer is simulated by a number of hexagons. For our estimations we used a larger number of smaller hexagons (see figure on the right). Based on the knowledge of uncertainty for angular alignment and translational alignment we are able to calculate the estimated uncertainty contributions.
Total area = 100 mm2
5
10
15
20
2530
3540
4550
5560
6570758085
0.2 0.4 0.6 0.8 1.0
0.2
0.4
0.6
0.8
1.0
LEDG101.evk, redmeasured datablueFit Cosg with g8.92036, dashedCos
5
10
15
20
25
30
3540
4550
5560
6570758085
0.2 0.4 0.6 0.8 1.0
0.2
0.4
0.6
0.8
1.0
LEDB101.evk, redmeasured datablueFit Cosg with g39.0866, dashedCos
-S3b, luminous flux, Integrated photocurrent, solid angle weighted The most important contribution of uncertainty is originated from the quantity “Integrated photocurrent, solid angle weighted”. It would be useful to have further information about this quantity (i.e. eventl. citation). How it has been determined? PTB: The figure below on the left shows the goniophotometric measurement of the LEDs in principle. The averaged zonal illuminance is derived from the measured averaged zonal photocurrent ( )ϑj . The figure on the right shows it as a function of the angle ϑ .
Since the determination of this averaged zonal photocurrent is a complex system which consists of several dc motor drives, a current/voltage converter and a digital voltmeter a correction factor czone
was introduced. The averaged value of czone = 1, but to consider the uncertainty caused by an
unsharp start and stop angle ( EndStart ϕϕ , ) it is necessary and defined as follows :
πϕϕ
2EndStart
zonec −=
Now we can start the MC-simulation: Repeat the following with normal distributed varied KVVEndStart j,,, ϑϕϕ
( ) ( ) ( ) ϑϑϑϑϑπ
ϑ
d1Sin0
zone ⋅+⋅+⋅+⋅= ∫=
KVVV jjcX
and in principle from X you will get the so called “Integrated photocurrent, solid angle weighted”
( )Xj Mean=Φ with ( ) ( )XU j viationStandardde=Φ .
-S3c, chromaticity coordinates, red LED The uncertainty of the chromaticity coordinates of the red LED is mainly given by the spectral bandpass correction and the straylight correction of the spectrometer. There is however no information about the amount of correction that has been applied and the spectrometer used for the measurement(bandpass, wavelength accuracy, level of straylight,…) -There is no information about the uncertainty contributions (input quantities and their uncertainties) used in the Monte Carlo simulation.
0.5 1.0 1.5 2.0 2.5 3.0Radian
2.107
4.107
6.107
8.107
Photocurrent AMeasured averaged zonal photocurrent as function of zone angle
PTB: As you can see in our uncertainty budgets the correction values of bandpass and spectrometer straylight is always 0. That means no correction was applied. But we estimated the uncertainty contributions by help of some MC simulations. The following figure shows an example result of a similar simulation.
Varied input parameters of the simulation were mainly spectrometer response data during measurement the LED and the halogen lamp used for sensitive calibration with an uncertainty of their spectral irradiance expressed as an uncertainty of the distribution temperature of a planckian radiator (approx. 10 K), an estimated straylight correction matrix (similar to the figure below, which is the real strayight correction matrix of the used array spectrometer from knowledge we have today ), an assumed triangle-shaped bandpass (halfwidth approx. 3nm ), the function between channel-no and wavelengths with a wavelength uncertainty of approx. 0.8nm, etc.
NMIJ
Question to NMIJ on May 10, 2010
0.6998 0.7002 0.7004 0.7006x
0.2988
0.2992
0.2994
0.2996
y
500 500
1000 1000
-S3a average LED intensity, illuminance responsivity
It is very unusual to see a rectangular probability function for the uncertainty of the illuminance
responsivity. Usually this value is either taken from a calibration certificate or determined by
another measurement (traceable to the radiometric scale). In both cases the distribution is
typically Gaussian type. Furthermore the uncertainty seems to be rather large (much larger than
declared CMC values in the KCDB with k=2…).
-S3b, luminous flux, Angular resolution, etc.
Why the contribution of the quantity called « angular resolution, etc » is much larger for the red
LED than for the others (red: 0.91%, green: 0.28%) even if the angular distribution of the LEDs are
very similar (the green LED is even narrower than the red)?
-S3c, chromaticity coordinates, red LED
It would be useful to report in the uncertainty budget of the chromaticity coordinates of the red
LED one additional digit (in the column “contribution”). The GUM recommands to report
uncertainty with two significant digit.
Answers from NMIJ on June 02, 2010
I am submitting two file (Reply to Question and Revised verification report).
Revised points in verification file are edited the Word files with red characters. New verification
report is revised according to the comment (Uncertainty Component name, Deg. of freedom, add
to new figure etc,).
But, there is no modify of the combined standard uncertainty .
Q1:-S3a average LED intensity, illuminance responsivity
It is very unusual to see a rectangular probability function for the uncertainty of the illuminance
responsivity. Usually this value is either taken from a calibration certificate or determined by
another measurement (traceable to the radiometric scale). In both cases the distribution is
typically Gaussian type. Furthermore the uncertainty seems to be rather large (much larger than
declared CMC values in the KCDB with k=2…).
Re1:
Thank you for good advice. I made a mistake about probability function of illuminance
responsivity. I would like to correct about probability function and freedom of it.
Next, I would like to explain about uncertainty of illuminance responsivity. In order to consider a
near-field effects which CIE 127:2007 (5.4 P17) described, illuminance responsivity of our
photometer for LED measurement is calibrated by luminous intensity standard lamp at far-field
condition, and then it is calibrated by an integrating sphere source(operated at 2856K) at the
distance corresponding to CIE condition B. Our uncertainties of illuminance responsivity include
uncertainty of near-filed effect. Therefore it becomes larger than uncertainty of CMC.
Q1:-S3b, luminous flux, Angular resolution, etc.
Why the contribution of the quantity called ≪ angular resolution, etc ≫is much larger for the
red LED than for the others (red: 0.91%, green: 0.28%) even if the angular distribution of the LEDs
are very similar (the green LED is even narrower than the red)?
Re2:
Firstly, I would like to change the contribution of the quantity's name from "angular resolution,
etc" to "measurement angle step and angular resolution". I send the modified uncertainty budget.
Sorry, my expressions confuse.
Fig1 indicate an angular distribution of red and green LED. The angular distributions of red LED
is not smoother than it of green LED .I think the angular distribution of the red LED is not the
same as others. Red LED have an irregular angular distribution. For this reasons, the uncertainty of
"measurement step and angular resolution" on red LED became larger than green LED in our
budget.
Fig1: angular distribution
Q3:-S3c, chromaticity coordinates, red LED
It would be useful to report in the uncertainty budget of the chromaticity coordinates of the red
LED one additional digit (in the column "contribution”). The GUM recommends reporting
uncertainty with two significant digits.
A3:
Thank you for good advice. I send the modified uncertainty budget. I add one additional digit to
uncertainty values of contribution, but the combined standard uncertainty isn't changed.
CENAM
Question to CENAM on May 10, 2010
-S3a, average LED intensity, Spectral mismatch correction
Why the uncertainty of the spectral mismatch correction is almost constant for all type of LED’s?
Usually the uncertainty is much lower for white LEDs than for blue LEDs?
-S3b, luminous flux, Standard lamps spectral mismatch correction
The quantity “Standard lamps spectral mismatch correction” seems to be rather large. What kind
of standard lamps was used (usually incandescent lamps are used which are not too far from CIE
illuminant A)? What is the f1’ value of the photometer? What is the estimated relative spectral
throughput of the sphere (i.e. how “flat” is the painting)?
-S3c, chromaticity coordinates
What is the quantity “Propagation from spectral distribution measurement”? Why is it constant for
all colours (15.66% , 13.96%) and why the sensitivity coefficient so small 0.00002 (% per %?) and
constant?
-S3c, chromaticity coordinates
uncertainty of chromaticity coordinates are usually reported as absolute value as chromaticity
coordinates are highly non-linear quantities.
-S3c, chromaticity coordinates, red LED
in the case of the red LED the absolute uncertainty are as following: ux= 0.006 and uy=0.0006
(hence a factor of 10 between both coordinates). Is there are an explication for this behavior?
Usually the chromaticity of red LED are fully (negative) correlated resulting in similar uncertainties
in x an y?
Answers from CENAM on May 20, 2010
Please find below the answers to the questions done for CENAM. -S3a, average LED intensity, Spectral mismatch correction
Why the uncertainty of the spectral mismatch correction is almost constant for all type of LED’s?
Usually the uncertainty is much lower for white LEDs than for blue LEDs?
RE: Unfortunately the resolution of the spectrorradiometer we used to measure the LEDs spectra was very bad; thus causing this component to be dominant over the other, and making the spectral mismatch uncertainties to look almost constant.
-S3b, luminous flux, Standard lamps spectral mismatch correction
The quantity “Standard lamps spectral mismatch correction” seems to be rather large. What kind
of standard lamps was used (usually incandescent lamps are used which are not too far from CIE
illuminant A)? What is the f1’ value of the photometer? What is the estimated relative spectral
throughput of the sphere (i.e. how “flat” is the painting)?
RE: Unfortunately the resolution of the spectrorradiometer we used to measure the spectra was very bad; thus causing this spectral mismatch corrections to be very large. We used incandescent lamps operated as CIE Standard illuminant A. The f1=13,36. The estimated relative spectral throughput of the sphere is fairly plain.
-S3c, chromaticity coordinates
What is the quantity “Propagation from spectral distribution measurement”? Why is it constant for
all colours (15.66% , 13.96%) and why the sensitivity coefficient so small 0.00002 (% per %?) and
constant?
RE: We call “Propagation from spectral distribution measurement” to the uncertainty component due to the calculation method from the spectral irradiance lectures. This is constant because we used the average value obtained from the standard lamps used. This also produced such a sensitivity coefficient values, and almost constants.
-S3c, chromaticity coordinates
uncertainty of chromaticity coordinates are usually reported as absolute value as chromaticity
coordinates are highly non-linear quantities.
RE: We reported our final results for those values as absolute to the pilot laboratory; however, according to the final report format, we were requested to report those as relative, and we did it as well.
-S3c, chromaticity coordinates, red LED
in the case of the red LED the absolute uncertainty are as following: ux= 0.006 and uy=0.0006
(hence a factor of 10 between both coordinates). Is there are an explication for this behavior?
Usually the chromaticity of red LED are fully (negative) correlated resulting in similar uncertainties
in x an y?
RE: We do not find such a values as they are mentioned. We have double-checked the results we send to the pilot laboratory; as well as those the pilot laboratory sent back for revision; and we found they are ok, within the same magnitude order. Would you please let us know where you found those?
LNE
Question to LNE on May 10, 2010
-S3c, chromaticity coordinates
uncertainty of chromaticity coordinates are usually reported as absolute value as chromaticity
coordinates are highly non-linear quantities.
NMC-A*STAR
Question to A*STAR on May 10, 2010
-S3b, luminous flux,
A*STAR has not used an auxiliary lamp for compensating changes of the integration properties of
the sphere resulting in the different configuration between the LED measurement and the sphere
calibration. Has this influence being estimated?
-S3c, chromaticity coordinates
uncertainty of chromaticity coordinates are usually reported as absolute value as chromaticity
coordinates are highly non-linear quantities.
Answers from A*STAR on June 21, 2010
Question for: -S3b, luminous flux, A*STAR has not used an auxiliary lamp for compensating changes of the integration properties of the sphere resulting in the different configuration between the LED measurement and the sphere calibration. Has this influence being estimated? Reply: The one-meter integrating sphere that we used for LED flux measurement do have a tungsten auxiliary lamp. The absorption corrections were carried out over the whole wavelength range of 380 nm to 780 nm in 1 nm interval for both the LED measurement and the sphere calibration. An additional paragraph explaining this is added in section 10.3 of the uncertainty budgets_S3b. Please refer to the revised file attached. (Dong-Hoon, the revised file is actually attached in my last email to you so I didn’t repeat here) Question for: -S3c, chromaticity coordinates uncertainty of chromaticity coordinates are usually reported as absolute value as chromaticity coordinates are highly non-linear quantities. Reply: The uncertainty of chromaticity coordinates that we reported for the -S3c results are indeed in absolute values.
VSL
Question to VSL on May 10, 2010
-S3a, average LED intensity
What is the quantity “Non-uniformity of source”? Is this due to the non-coincidence of the optical
and mechanical axis? In Figure 11-6 of the report a measurement of the illuminance in function of
different (azimuthal) angles is shown. It is written that this is due to the non-coincidence of the
mechanical axis and the optical axis. However we believe that it is to a misalignment of the
photometer in respect to the rotation axis as illustrated below.
-S3b, luminous flux, Near-field absorption of backward emission
The most important contribution to uncertainty is the quantity “Near-field absorption of backward
emission”. Has the flux also being corrected with this quantity, if yes what was the estimated ratio
from the backwards flux to the total flux?
-S3b, luminous flux
The goniophotometrical measurements were done at an angular increment of 5° (polar angle).
Has the uncertainty due to this rather large increment been estimated (The half angle of the
green LED is only 22°)?
Answers from VSL on May 10, 2010 -S3a, average LED intensity What is the quantity “Non-uniformity of source”? Is this due to the non-coincidence of the optical and mechanical axis? In Figure 11-6 of the report a measurement of the illuminance in function of different (azimuthal) angles is shown. It is written that this is due to the non-coincidence of the mechanical axis and the optical axis. However we believe that it is to a misalignment of the photometer in respect to the rotation axis as illustrated below. Answer VSL As the reference axis for alignment is not defined in the protocol, one needs to make a choice which axis is used for alignment (optical or mechanical). From our research we believe that the mechanical axis for alignment is the best choice for comparability of the measurement results. When using the mechanical axis as a reference axis you will need to check what this means with respect to the azimuthal angle direction in respect to the uncertainty. As measurements show (figure 11-6 of the report) one needs to take the non-coincidence of the mechanical and optical axis into account, again: if you are using the mechanical axis as reference. Please notice that when you align on optical axis you will introduce an angular shift between the optical axis of your LED and the rotation axis of your goniometer. This will also introduce an uncertainty. -S3b, luminous flux, Near-field absorption of backward emission The most important contribution to uncertainty is the quantity “Near-field absorption of backward emission”. Has the flux also being corrected with this quantity, if yes what was the estimated ratio from the backwards flux to the total flux?
Answer VSL The flux has not been corrected for the “Near-field absorption of backward emission”.
-S3b, luminous flux The goniophotometrical measurements were done at an angular increment of 5° (polar angle). Has
the uncertainty due to this rather large increment been estimated (The half angle of the green LED is only 22°)?
Answer VSL As the detector size of our photometer is 10 mm^2 one can calculate the smallest step size that is required to have overlap between the measurement points measuring at a distance of 100 mm. With a step size of 5º we still have an overlap from point to point. Next to this we have taken the green LED and measured ones in steps of 5º and ones in steps of 1º. The results showed that there is a small difference in respect to the total uncertainty between a step of 5º compared to a step size of 1º. We have taken the difference into the uncertainty component for the integration method.
NIST
Question to NIST on May 10, 2010
-S3c, chromaticity coordinates
What is the estimated wavelength uncertainty of the spectrometer measurement (expressed in
nm)? Have there been some spectral correlations taking to account in the analysis?
-S3c, chromaticity coordinates, contributions due to alignment of the LED
Minor comment: It is very unusually that Type A has an infinite number of degree of freedom.
Either the contribution has been determined experimentally and then a statistics is used (Type A
with limited number of degrees of freedom) or a model was used (perhaps also based on
experimental results) to describe the specific input quantity (Type B with infinite number of
degrees of freedom).
MKEH
Question to MKEH on May 10, 2010
-S3a, average LED intensity
Several important contributions are missing: temperature, readout of the photometer (Type A).
Why the calibration accuracy has a rectangular distribution, usually it should be Gaussian
distributed.
-S3c, chromaticity coordinates
Why the uncertainty is stated as a minimum value (>0.0004 and >0.0002). The uncertainty analysis
is used to determine the estimates of the output quantity and its uncertainty (for a given
confidence interval). If only a minimum value is stated either the uncertainty budget is incomplete
or the estimation of some of the contributions are believed to be too small (and should therefore
be adapted).
Answers from MKEH on June 1, 2010
1. In the luminous intensity error budget our main source of error comes from the detector
calibration. We do not have cryogenic radiometer we have Si selfcalibration as an absolute
method. In this case the main source of error is not statistical, but the practical uncertainty of the
method (the internal QE is not measured just believed, based on the literature).
Therefore this is a type B error. All the other participants have cryogenic radiometer……
2. In the color uncertainty budget I have left out data. YOU ARE right…
Revised budget:
source of uncertainty
standard uncertainty
probability distribution
sensitivity coefficient
standard uncertainty in
∆x
standard uncertainty in
∆y spectral
irradiance calibration
1,5% rectangular type B
sample dependent
∆x1 <0,002 0,0003 < ∆x1
∆y1 <0,002 0,0001 < ∆y1
wavelength error 0,1 nm rectangular
type B sample
dependent ∆x2 <0,001
0,00005 < ∆x2 ∆y2 <0,001
0,00005 < ∆y2
linearity 0,05% rectangular type B
sample dependent
∆x3 <0,0005 0,00005 < ∆x3
∆y3 <0,0005 0,00005 < ∆y3
stray light 10-15 – 10-13W rectangular type B
sample dependent
∆x4 <0,0014 0,00005 < ∆x4
∆y4 <0,002 0,00005 < ∆y4
dark noise 2*10-15 W rectangular type B
sample dependent
∆x5 <0,002 0,00003< ∆x5
∆y5 <0,003 0,00001 < ∆y5
room temp. dependence 1 K rectangular
type B sample
dependent ∆x6 <0,00005 ∆y6 <0,00005
light source repeatability as measured normal
type A sample
dependent as calculated as calculated
geometry error rectangular type B
sample dependent as calculated as calculated
combined standard
uncertainty 0,0004 < ∆x
∆x < 0,0026 0,0002 < ∆y ∆y < 0,0032
APMP Supplementary Comparisons of
LED Measurements
APMP.PR-S3a Averaged LED Intensity
APMP.PR-S3b Total Luminous Flux of LEDs
APMP.PR-S3c Emitted Colour of LEDs
Identification of Outliers
1. INTRODUCTION
The relative deviations from the mean value are calculated for each participant and for each type of LEDs and distributed in order to identify the obvious outliers, which can significantly skew the Reference Values of the comparison. Each participant should recommend which data should be removed in the calculation of the Reference Values. The name of the participant is not disclosed in this stage.
The relative deviations from the mean value are obtained as follows:
1. The ratios r1(Xi) and r2(Xi) are calculated for each artefact LED (Xi = R-i, G-i, B-i, W-i, or D-i with i = 1, 2 or 3):
1 21 2
( ) ( )( ) ; ( )( ) ( )
L i L ii i
P i P i
y X y Xr X r Xy X y X
= = . (1)
Here, yL(Xi), yP1(Xi), yP2(Xi) denote the measurement result of the participant laboratory, of the pilot laboratory before travel, and of the pilot laboratory after travel, respectively, for the artefact LED Xi.
2. The difference of the ratios corresponding to the artefact drift is calculated for each artefact LED Xi:
2 1( ) ( ) ( )i i id X r X r X= − . (2)
3. The mean value of each type of LEDs is calculated for each type of the artefact LEDs:
,
,
,
,
,
( ) ( ) ,
( ) ( ) ,
( ) ( ) ,
( ) ( ) ,
( ) ( ) .
i j i j
i j i j
i j i j
i j i j
i j i j
m R Mean r R
m G Mean r G
m B Mean r B
m W Mean r W
m D Mean r D
=
=
=
=
=
. (3)
Here, the following data are excluded in the calculation of the mean: firstly, the data which are requested to be removed by the participant in the process of review of relative data, secondly, the data with its drift in Eq. (2) larger than 4 % after the temperature correction.
Note that the mean values of the ratios in Eqs. (3) correspond to the relative deviations of the participant’s data with respect to the pilot’s data.
4. The mean values in Eqs. (3) are normalized to the mean value of the measurement data of all the participants for the same type of the artefact LEDs:
[ ]
[ ]
[ ]
[ ]
[ ]
( )( ) ,( )
( )( ) ,( )
( )( ) ,( )
( )( ) ,( )
( )( ) .( )
Lab xLab x
Lab n n
Lab xLab x
Lab n n
Lab xLab x
Lab n n
Lab xLab x
Lab n n
Lab xLab x
Lab n n
m RM RMean m R
m GM GMean m G
m BM BMean m B
m WM WMean m W
m DM DMean m D
−−
−
−−
−
−−
−
−−
−
−−
−
=
=
=
=
=
(4)
5. The deviations of the mean values in Eqs.(4) from 1 are calculated for each participant and for each type of the artefact LED:
( ) ( ) 1,( ) ( ) 1,( ) ( ) 1,( ) ( ) 1,( ) ( ) 1.
Lab x Lab x
Lab x Lab x
Lab x Lab x
Lab x Lab x
Lab x Lab x
R M RG M GB M BW M WD M D
− −
− −
− −
− −
− −
∆ = −∆ = −∆ = −∆ = −∆ = −
(5)
Note that the deviations in Eq. (5) correspond to the relative deviations of each participant from the mean value over all the participants for each type of the artefact LEDs.
In the case of the LED measurement, the quantity to be measured is a function of junction temperature. Therefore, the junction voltage is simultaneously measured and reported with the comparison quantity. Based on the reported junction voltage data and the characteristic parameters of each artefact LED determined by the pilot laboratory in the preparation stage, the measured comparison quantities can be corrected to one junction voltage.
In the following, the relative deviations in Eqs.(5) of all the participants are listed in a table and plotted for visualization. There are two sets of the data: the first set is based on the submitted measurement data without any correction. The second set is based on the data corrected to one junction voltage as a result of the temperature correction.
In the data table, the relative deviations larger than 10 % are indicated as red, which seem to be the obvious outliers. Note that we have considered here only the result data with an artefact drift much smaller than 4 %.
2. WITHOUT CORRECTION
Lab1 Lab2 Lab3 Lab4 Lab5 Lab6 Lab7
R -1.64% 1.46% -0.72% -0.05% -2.51% -33.20% 3.67%
G -1.71% 0.39% -0.88% -0.17% 1.22% -12.26% 2.89%
B -0.85% 1.12% -2.17% -1.12% 3.62% -8.63% -0.14%
W -2.23% 1.37% -0.99% 0.09% -0.26% -19.01% 1.39%
D -2.74% 0.00% -1.58% -1.68% 0.11% -14.44% 2.61%
Lab8 Lab9 Lab10 Lab11 Lab12 Lab13 Lab14 Lab15
-0.51% 0.78% 0.24% 13.76% 2.00% 6.37% -0.40% 9.09%
0.05% -0.80% 0.69% -5.44% 2.77% -2.73% 2.76% 11.52%
1.43% 0.46% 0.15% -4.45% 2.21% -9.66% 5.57% 11.60%
-0.62% -1.18% 0.18% 5.45% 2.32% 0.68% 0.98% 9.60%
-1.34% -1.68% -0.06% -0.33% 2.98% -2.96% 0.90% 17.48%
3. WITH TEMPERATURE CORRECTION
Lab1 Lab2 Lab3 Lab4 Lab5 Lab6 Lab7
R -0.02% 0.98% -1.12% 1.33% -0.98% -33.20% 3.04%
G -1.23% 0.17% -1.23% 0.04% 1.84% -12.54% 2.86%
B -0.90% 1.12% -2.31% -1.32% 3.57% -8.49% -0.16%
W -1.38% 0.94% -1.43% 0.68% 0.55% -19.32% 1.44%
D -2.36% -0.10% -1.37% -1.00% 0.72% -14.73% 2.57%
Lab8 Lab9 Lab10 Lab11 Lab12 Lab13 Lab14 Lab15
-1.75% 1.79% 1.69% 11.21% 4.15% 4.74% -1.10% 9.23%
-0.15% -0.27% 1.19% -6.28% 3.52% -3.30% 2.52% 11.64%
1.51% 0.41% 0.10% -4.43% 2.22% -9.33% 5.66% 11.45%
-1.01% -0.29% 0.90% 3.88% 3.71% -0.56% 0.89% 9.61%
-1.29% -1.08% 0.09% -1.15% 3.69% -3.16% 1.09% 15.71%
APMP Supplementary Comparisons of
LED Measurements
APMP.PR-S3a Averaged LED Intensity
APMP.PR-S3b Total Luminous Flux of LEDs
APMP.PR-S3c Emitted Colour of LEDs
Pre-draft A Process
Review of Relative Data
1. INTRODUCTION
The relative data are calculated and distributed for review to check the stability of the artefact LEDs for each participant before and after travel, and the internal consistency of the artefact LEDs measured at each participant lab.
The relative data are obtained as follows:
1. The ratio R1(Xi) and R2(Xi) are calculated for each artefact LED (Xi = R-i, G-i, B-i, W-i, or D-i with i = 1, 2 or 3)
)()()( ;
)()()(
22
11
iP
iLi
iP
iLi Xy
XyXRXyXyXR == . (1)
Here, yL(Xi), yP1(Xi), yP2(Xi) denote the measurement result of the participant laboratory, of the pilot laboratory before travel, and of the pilot laboratory after travel, respectively, for the artefact LED Xi.
2. The ratios in Eq. (1) are normalized to the mean value of the measurement data for the same type (colour) of artefact LEDs:
[ ] [ ]jiji
ii
jiji
ii XRMean
XRXrXRMean
XRXr,
22
,
11 )(
)()( ;)(
)()( == . (2)
We refer these normalized ratios r1(Xi) and r2(Xi) as to the relative data for the artefact LED Xi. Note that the normalization in Eq. (2) removes any relationship of the absolute scale of the participant laboratory and leaves only internal consistency information within the sub-set of the same LED types.
In the case of the LED measurement, the quantity to be measured is a function of junction temperature. Therefore, the junction voltage is simultaneously measured and reported with the comparison quantity. Based on the reported junction voltage data and the characteristic parameters of each artefact LED determined by the pilot laboratory in the preparation stage, the measured comparison quantities can be corrected to one junction voltage. It is expected that this temperature correction via junction voltage can improve the stability and internal consistency of the artefact LEDs.
In the next chapters, the relative data of all the participants are listed and plotted for visualization. There are two sets of the relative data: the first set is based on the submitted measurement data without any correction. The second set is based on the data corrected to one junction voltage as a result of the temperature correction. By comparison of the two relative data, one can check if the temperature correction via junction voltage works properly by improving the stability of the artefact LEDs. The scale of all the plot of relative data is fixed (from 0.96 to 1.04) for a better comparison. Note that the non-correlated uncertainty of the pilot lab is smaller than 0.7 % (k = 1) for all the type of LEDs.
2. MIKES (SET #1)
2.1. WITHOUT CORRECTION
r1 r2
R-1 1.0001 0.9939
R-2 1.0093 0.9991
R-3 1.0033 0.9943
G-1 1.0014 1.0045
G-2 0.9999 1.0037
G-3 0.9968 0.9938
B-1 0.9981 1.0095
B-2 0.9893 0.9994
B-3 1.0007 1.0030
W-1 1.0541 0.9853
W-2 0.9886 0.9938
W-3 0.9879 0.9902
D-1 1.0007 1.0051
D-2 0.9958 0.9983
2.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 0.9981 0.9976
R-2 1.0035 1.0024
R-3 1.0003 0.9981
G-1 0.9999 1.0050
G-2 0.9999 1.0054
G-3 0.9953 0.9946
B-1 0.9999 1.0111
B-2 0.9904 1.0004
B-3 0.9976 1.0006
W-1 1.0525 0.9849
W-2 0.9885 0.9945
W-3 0.9883 0.9912
D-1 1.0008 1.0054
D-2 0.9953 0.9985
3. CMS-ITRI (SET #2)
3.1. WITHOUT CORRECTION
r1 r2
R-1 1.0116 0.9988
R-2 1.0029 0.9920
R-3 1.0015 0.9932
G-1 1.0390 0.9879
G-2 0.9972 0.9977
G-3 0.9920 0.9862
B-1 0.9885 1.0028
B-2 0.9990 1.0079
B-3 0.9984 1.0033
W-1 1.0073 0.9967
W-2 1.0000 0.9981
W-3 0.9997 0.9982
D-1 0.9971 0.9999
D-2 0.9982 1.0048
3.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 1.0001 1.0077
R-2 0.9929 1.0031
R-3 0.9912 1.0050
G-1 1.0384 0.9908
G-2 0.9960 0.9999
G-3 0.9883 0.9866
B-1 0.9892 1.0040
B-2 0.9952 1.0068
B-3 0.9998 1.0051
W-1 1.0058 0.9997
W-2 0.9984 1.0012
W-3 0.9946 1.0002
D-1 0.9974 0.9999
D-2 0.9981 1.0046
4. PTB (SET #3)
4.1. WITHOUT CORRECTION
r1 r2
R-1 0.9940 1.0183
R-2 0.9762 1.0024
R-3 0.9908 1.0182
G-1 0.9933 1.0074
G-2 0.9976 1.0031
G-3 0.9934 1.0053
B-1 0.9987 1.0051
B-2 0.9754 0.9925
B-3 1.0089 1.0195
W-1 0.9883 1.0060
W-2 0.9905 1.0091
W-3 0.9955 1.0107
D-1 0.9922 1.0023
D-2 0.9985 1.0070
4.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 0.9996 1.0102
R-2 0.9865 0.9954
R-3 0.9985 1.0097
G-1 0.9972 1.0057
G-2 0.9997 1.0006
G-3 0.9954 1.0014
B-1 0.9992 1.0060
B-2 0.9752 0.9925
B-3 1.0086 1.0185
W-1 0.9941 1.0012
W-2 0.9956 1.0041
W-3 0.9995 1.0055
D-1 0.9946 0.9993
D-2 1.0013 1.0048
5. NMIJ (SET #4)
5.1. WITHOUT CORRECTION
r1 r2
R-1 0.9873 1.0019
R-2 0.9958 1.0081
R-3 0.9977 1.0093
G-1 0.9976 1.0099
G-2 0.9947 1.0044
G-3 0.9913 1.0021
B-1 0.9689 0.9844
B-2 1.0020 1.0142
B-3 1.0074 1.0230
W-1 0.9856 1.0113
W-2 0.9892 1.0082
W-3 0.9942 1.0115
D-1 0.9957 1.0044
D-2 0.9956 1.0043
5.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 0.9947 1.0005
R-2 0.9976 1.0021
R-3 1.0003 1.0048
G-1 0.9990 1.0088
G-2 0.9959 1.0029
G-3 0.9929 1.0006
B-1 0.9688 0.9845
B-2 1.0019 1.0144
B-3 1.0071 1.0233
W-1 0.9907 1.0092
W-2 0.9906 1.0049
W-3 0.9957 1.0089
D-1 0.9983 1.0027
D-2 0.9969 1.0021
6. CENAM (SET #5)
6.1. WITHOUT CORRECTION
r1 r2
R-1 0.9920 0.9866
R-2 1.0017 1.0010
R-3 1.0134 1.0053
G-1 0.9898 0.9791
G-2 0.9975 1.0020
G-3 1.0183 1.0133
B-1 1.0293 1.0152
B-2 0.9990 0.9827
B-3 0.9902 0.9836
W-1 0.9962 0.9990
W-2 1.0019 1.0002
W-3 1.0022 1.0005
D-1 1.0033 1.0031
D-2 0.9972 0.9964
6.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 0.9917 0.9863
R-2 1.0011 1.0004
R-3 1.0134 1.0070
G-1 0.9905 0.9799
G-2 0.9968 1.0020
G-3 1.0174 1.0133
B-1 1.0301 1.0159
B-2 0.9983 0.9822
B-3 0.9900 0.9835
W-1 0.9985 0.9976
W-2 1.0030 0.9988
W-3 1.0026 0.9995
D-1 1.0016 1.0053
D-2 0.9948 0.9983
7. LNE (SET #6)
7.1. WITHOUT CORRECTION
r1 r2
R-1 1.0098 0.9906
R-2 1.0005 0.9897
R-3 1.0133 0.9961
G-1 1.0042 0.9979
G-2 1.0039 0.9957
G-3 0.9998 0.9986
B-1 1.0096 1.0046
B-2 1.0004 0.9972
B-3 0.9936 0.9946
W-1 0.9861 1.0146
W-2 0.9915 1.0091
W-3 0.9941 1.0047
D-1 1.0002 0.9985
D-2 1.0012 1.0000
7.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 1.0058 0.9950
R-2 0.9964 0.9946
R-3 1.0082 0.9999
G-1 1.0020 0.9986
G-2 1.0032 0.9978
G-3 0.9980 1.0004
B-1 1.0090 1.0047
B-2 0.9998 0.9976
B-3 0.9935 0.9954
W-1 0.9852 1.0171
W-2 0.9884 1.0102
W-3 0.9921 1.0070
D-1 0.9977 0.9999
D-2 1.0001 1.0023
8. METAS (SET #7)
8.1. WITHOUT CORRECTION
r1 r2
R-1 1.0024 0.9959
R-2 1.0052 1.0014
R-3 1.0001 0.9951
G-1 1.0018 0.9971
G-2 1.0000 0.9985
G-3 1.0031 0.9995
B-1 0.9988 1.0006
B-2 1.0104 1.0076
B-3 0.9957 0.9869
W-1 1.0024 1.0041
W-2 0.9979 0.9983
W-3 0.9992 0.9981
D-1 0.9999 1.0024
D-2 0.9942 1.0036
8.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 1.0035 0.9944
R-2 1.0086 1.0029
R-3 0.9981 0.9924
G-1 1.0019 0.9967
G-2 1.0008 0.9986
G-3 1.0033 0.9986
B-1 0.9988 1.0007
B-2 1.0132 1.0105
B-3 0.9930 0.9839
W-1 1.0019 1.0031
W-2 0.9990 0.9976
W-3 1.0010 0.9974
D-1 1.0018 1.0023
D-2 0.9944 1.0015
9. A*STAR (SET #8)
9.1. WITHOUT CORRECTION
r1 r2
R-1 1.0025 1.0019
R-2 0.9966 1.0002
R-3 0.9997 0.9991
G-1 1.0030 1.0011
G-2 1.0004 1.0025
G-3 0.9947 0.9984
B-1 0.9958 0.9966
B-2 1.0039 0.9994
B-3 1.0024 1.0018
W-1 1.0004 1.0031
W-2 0.9965 1.0018
W-3 0.9967 1.0014
D-1 0.9953 0.9995
D-2 1.0021 1.0031
9.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 1.0028 0.9994
R-2 0.9978 0.9990
R-3 1.0018 0.9991
G-1 1.0037 1.0008
G-2 1.0004 1.0014
G-3 0.9957 0.9979
B-1 0.9959 0.9964
B-2 1.0041 0.9993
B-3 1.0024 1.0018
W-1 1.0010 1.0012
W-2 0.9978 1.0004
W-3 0.9988 1.0007
D-1 0.9961 0.9989
D-2 1.0024 1.0026
10. VSL (SET #1)
10.1. WITHOUT CORRECTION
r1 r2
R-1 1.0046 1.0051
R-2 0.9931 0.9968
R-3 1.0008 0.9995
G-1 0.9989 0.9941
G-2 1.0046 1.0025
G-3 0.9959 1.0040
B-1 1.0033 1.0010
B-2 0.9924 1.0061
B-3 0.9975 0.9996
W-1 0.9913 0.9986
W-2 0.9940 1.0099
W-3 0.9938 1.0125
D-1 1.0034 1.0113
D-2 0.9914 0.9939
10.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 1.0065 1.0036
R-2 0.9962 0.9927
R-3 1.0041 0.9969
G-1 1.0004 0.9931
G-2 1.0057 1.0008
G-3 0.9974 1.0027
B-1 1.0034 1.0016
B-2 0.9923 1.0061
B-3 0.9978 0.9988
W-1 0.9946 0.9973
W-2 0.9966 1.0069
W-3 0.9960 1.0086
D-1 1.0072 1.0135
D-2 0.9890 0.9902
11. NIST (SET #3)
11.1. WITHOUT CORRECTION
r1 r2
R-1 1.0054 0.9992
R-2 0.9939 0.9926
R-3 1.0067 1.0023
G-1 1.0099 1.0091
G-2 0.9924 0.9953
G-3 0.9974 0.9959
B-1 0.9891 0.9956
B-2 1.0011 1.0014
B-3 1.0033 1.0095
W-1 0.9995 1.0017
W-2 0.9975 1.0026
W-3 0.9979 1.0009
D-1 0.9992 1.0055
D-2 0.9951 1.0002
11.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 1.0061 0.9959
R-2 0.9952 0.9907
R-3 1.0097 1.0024
G-1 1.0107 1.0088
G-2 0.9922 0.9938
G-3 0.9988 0.9958
B-1 0.9889 0.9953
B-2 1.0009 1.0012
B-3 1.0039 1.0098
W-1 1.0002 1.0021
W-2 0.9977 1.0029
W-3 0.9976 0.9995
D-1 0.9997 1.0059
D-2 0.9948 0.9997
12. VNIIOFI (SET #5)
12.1. WITHOUT CORRECTION
r1 r2
R-1 1.0017 1.0032
R-2 1.0008 0.9987
R-3 0.9986 0.9969
G-1 1.0065 1.0195
G-2 0.9724 0.9873
G-3 1.0093 1.0051
B-1 0.9895 0.9967
B-2 1.0202 1.0241
B-3 0.9815 0.9880
W-1 0.9990 1.0057
W-2 0.9942 1.0004
W-3 0.9990 1.0017
D-1 0.9904 1.0030
D-2 0.9997 1.0069
12.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 1.0013 1.0036
R-2 0.9989 0.9988
R-3 0.9993 0.9982
G-1 1.0057 1.0192
G-2 0.9720 0.9875
G-3 1.0096 1.0059
B-1 0.9903 0.9976
B-2 1.0195 1.0232
B-3 0.9815 0.9879
W-1 1.0002 1.0048
W-2 0.9953 0.9988
W-3 0.9986 1.0024
D-1 0.9902 1.0034
D-2 0.9997 1.0068
13. MKEH (SET #6)
13.1. WITHOUT CORRECTION
r1 r2
R-1 0.9983 1.0023
R-2 0.9994 *
R-3 * *
G-1 0.9295 *
G-2 * *
G-3 1.0313 1.0392
B-1 0.9948 1.0058
B-2 1.0043 1.0154
B-3 0.9797 *
W-1 0.9976 1.0013
W-2 0.9969 1.0055
W-3 0.9945 1.0041
D-1 1.0005 1.0046
D-2 0.9949 *
* damaged
13.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 0.9998 1.0019
R-2 0.9984 *
R-3 * *
G-1 0.9291 *
G-2 * *
G-3 1.0322 1.0387
B-1 0.9946 1.0054
B-2 1.0049 1.0159
B-3 0.9793 *
W-1 0.9978 1.0014
W-2 0.9971 1.0051
W-3 0.9951 1.0034
D-1 1.0005 1.0051
D-2 0.9944 *
* damaged
14. INM (SET #7)
14.1. WITHOUT CORRECTION
r1 r2
R-1 0.9844 1.0133
R-2 0.9764 0.9974
R-3 1.0057 1.0229
G-1 1.0008 1.0166
G-2 0.9863 0.9955
G-3 0.9929 1.0079
B-1 0.9727 1.0199
B-2 0.9896 1.0141
B-3 0.9866 1.0171
W-1 0.9898 1.0059
W-2 0.9964 1.0089
W-3 0.9919 1.0070
D-1 0.9999 1.0062
D-2 0.9936 1.0004
14.2. WITH TEMPERATURE CORRECTION
r1_cor r2_cor
R-1 0.9894 1.0107
R-2 0.9843 0.9965
R-3 1.0050 1.0140
G-1 1.0022 1.0143
G-2 0.9887 0.9943
G-3 0.9947 1.0058