optical mems for earth observation: an efficient optical
TRANSCRIPT
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Frederic Zamkotsian1, Arnaud Liotard2, Patrick Lanzoni1, Thierry Viard2, Wilfried Noell3, Benedikt Guldimann4, Marco Freire4, Stefan Kraft4
Laboratoire d’Astrophysique de Marseille, FranceThales Alenia Space, France
EPFL, Switzerland ESA / ESTEC, Netherlands
Optical MEMS for Earth Observation: an efficient optical cloud removal technique
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Spectrometer
FPA
Reflective slit
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Instrumental needs using micro-opto-electro-mechanical systems (MOEMS)
Wavefront control- Deformable mirrors
Object selection- Programmable slits
Spectral domain application- Programmable gratings
Phase
Intensity
Wavelength
Instrumental needs
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
MOEMS for Earth Observation
First phase: collecting all necessary data Earth observation instruments or payloadsExisting and potential optical MEMS componentsSecond phase Pre-selection of at least 6 optical payloads following
three different philosophies - pre-selection of 2 market-pull concepts- pre-selection of 3 techno-push concepts- pre-selection of 1 concept coming from outside Earth Observation
Final selection of the 2 most promising optical payloadThird phaseDetailed design of the 2 promising conceptsSynthesis of the study
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Tiltable micromirror arrayActive on intensityHigh contrastDigital mode only : light is switched between ON and OFF positions
Tiltable micromirror arrays
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Single crystalline micromirror array for next generation IR multi-object spectrographCollaboration between LAM and EPFL Goal: high contrast 1500:1 Fill factor > 90 % obtainedConcept
Electrostatic actuationPrecise tilt angle (landing beams)
RealizationCombination surface and bulkmicromachiningWafer level bonding of two wafers: one for th mirrors, one for the electrodes
MIRA
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Surface qualityOn 100µm x 200µm micromirrors: deformation < 10 nmTilt angle precision < 1 arcminActuation voltage < 100 V
Environmental testsVacuum (10-6 mbar)92K and 162 K Mirrors tiltSurface quality < 30 nm PtV in cryo
92K0V
92K90V
MIRA
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Most popular MOEMS deviceMicromirrors
2048x1080 mirrors individually adressablesPitch 13,68µm Tilt angle: 12°
Numerous applications Main application: image display Design modification not possible
Spatial qualification test (ESA contract)-40°C in vacuum (10-5 mbar)Micromirrors hold in position during > 1500 sDMD fully operationalLife test during 1038h, radiations, vibrations No showstopper for space use
DMD from Texas Instruments
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Programmable micro-diffraction gratings (PMDG)Action on phaseBased on 200µm x 4µm ribbons, with piston mouvmentDigital mode: light modulated between ON and OFF positionsAnalog mode: ribbons move in order to cancel partially the input light (“gray” scales)
PMDG
Incident lightReflected light
Incident lightReflected light
Incident lightDiffracted light
Incident lightDiffracted light
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
PMDG from Silicon Light Machines (ESA study)1086 pixels
6 ribbons (3 pairs) / pixel3 fixed ribbons / 3 piston ribbonsPixel pitch 25.5µmRibbon width / gap: 3.775µm / 0.475µmRibbon length 220µmActive area 75 x 28254 µm2
Window with visible coatngMonted on PCBHeat sink on the backVmax = 385V Coded on 1024 levels (10 bits)
PMDG from SLM
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Ribbons images / localized sourceFiltering in Fourier plane
PMDG in operation
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
PMDG performances
Device for wavelength selectionFully programmableSteep edge filters, contrast > 30Long term stability and reproducibilityDynamical response (1 MHz)
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Micro-deformable mirrors (MDM), action on wavefront (phase)Actuators arrayContinuous mirrorBoston Micromachines devicesUp to 4096 actuators, up to 5µm stroke.
MDM
h
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Mirror Surface
ActuatorsSubstrate
Anchoring post
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
First promising concept based on MOEMS : Cloud remover
©ESA Source = MERIS
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
MERIS return of experience :Push-broom spectro-imager for Earth monitoring
Clouds in the field-of-view generates massive straylightSun-glint completely saturates the detector.
Cloud remover
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Spectrometer characteristics (spectrum : 400 nm -> 1020 nm)
Classical design : slit dimensions17mm x 20 microns740 columns
New design : dynamical reflective slitBased on a micro-mirror arrayEnable to reject bright sources
Towards spectrometer
Towards light trap
Cloud remover
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Spectrometer characteristics (spectrum : 400 nm -> 1020 nm)Classical design : transmissive slitNew design : reflective slit
Compliant with the opto-mechanicaldesignEnable to reject bright sources
Spectrometer
FPA
Reflective slit
Cloud remover
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Straylight analysisComplete simulations with ASAPSpectrometer nominal designStraylight ratio :
Straylight level / useful signal
Slit 74x10pLMAX LREF
Pixel 740 Pixel 1
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YLmaxLref
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Straylight without bright sources remover
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Straylight with bright sources remover
6 %
Cloud remover
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
CAD view
Focal plane
Catadioptric objective
Concave grating MEMS / entrance slit
MIRA board
Cloud remover
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Neutral density plates
FOV = clouds + scene
Straylight simulator
L4
Output pupil
CCD camera
White source
DMD
L1
L2
L3
Input pupil
Slit 74x10pLMAX LREF
T6
Slit 74x10p LMAX LREFT6B (X=10)
T6C (X=20)
T6D (X=30)
X times 10p (upon a total de 74)
Pixel 740 Pixel 1
Pixel 740 Pixel 1
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Slit 74x10p LMAX LREFT6Y (X=-38 – out-of-field)
T6Z (X=-30)
X times 10p (upon a total de 74)
Pixel 740 Pixel 1
X
Z
YX
Z
Y
Cloud Ground
Spectrograph simulator
FOV simulator
Cloud remover: demonstration @ LAM
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Bright sources remover experiment results
Profile of the field-of-viewScene @ Lref (left part)Bright source @ Lmax (right part)
green curve: programmable slit is all ONblue curve: the micro-mirrors located on the bright area are switched OFF
Close-up view of the transition areaLight blue curve: perfect scene without the bright source
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Camera pixels
Nor
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S l i t 7 4 x 1 0 pL M A X L R E F
P i x e l 7 4 0 P i x e l 1
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Z
YX
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YLmaxLref
Cloud remover: demonstration @ LAM
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Bright sources remover experiment results
Profile of the field-of-viewScene @ Lref (left part)Bright source @ Lmax (right part)
green curve: programmable slit is all ONblue curve: the micro-mirrors located on the bright area are switched OFF
Close-up view of the transition areaLight blue curve: perfect scene without the bright source
0 200 400 600 8000
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Camera pixels
Nor
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inte
nsity
S l i t 7 4 x 1 0 pL M A X L R E F
P i x e l 7 4 0 P i x e l 1
X
Z
YX
Z
YLmaxLref
Cloud remover: demonstration @ LAM
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Bright sources remover experiment results
Profile of the field-of-viewScene @ Lref (left part)Bright source @ Lmax (right part)
green curve: programmable slit is all ONblue curve: the micro-mirrors located on the bright area are switched OFF
Close-up view of the transition areaLight blue curve: perfect scene without the bright source
0 200 400 600 8000
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Camera pixels
Nor
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MIRA
Cloud remover: demonstration @ LAM
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Second promising concept based on MOEMS : Tuneable spectrometer with field of view
©ESA Source = MERIS
V sat
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Spectrometer concept for push broom acquisitionUse of a micro mirrors array
One dimension for the FOVOne dimension for the spectral dispersion
Entrance slit
Linear detectorarray
Identical gratings
DMD
DMD for spectral tailoring with FOV
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Entrance slit
Linear detectorarray
Identical gratings
DMD
DMD for spectral tailoring with FOV
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
MOEMS (DMD) characteristicsMicro mirror dimension around 15 µm x 15 µmNumber of micro mirrors in spectral direction around 1000Number of micro mirrors in spatial direction around 2000
Design parameters (other operating points are possible)Spatial resolution = 5 m (for altitude = 700 Km)Total field = 10 Km (2000 pixels)Total bandwidth = 200 nm (ex : from 400 nm to 600 nm)Theoretical spectral resolution can be tuned from 0,2 nm to 200 nm
Instrument characteristics (for here above operating point)Entrance pupil dimension ΦPE = 270 mm Afocal magnification ratio G around 5 (grating size = 54 mm)Focusing focal length fFOC = 380 mm (F-number 7.6)Grating period around 300 lines/mm for visible range
DMD for spectral tailoring with FOV
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
VolumeX :669 Y : 480 Z : 568.
DMD for spectral tailoring with FOV
Bench demonstrator will be developed within a CNES study
Frederic Zamkotsian 8th ESA MNT Round table, Noordwijk, 15 – 18 October 2012
Space optical payloads can benefit from MOEMS technology
Optical MOEMS can bring new services/functionalities in Earth ObservationTwo promising concepts have been proposed and studied:- Cloud removal based on Digital Micro-mirror Array- Tunable spectrometer with field-of-view based on TI’s DMD
MOEMS for Earth Observation
100 200 300 400 500 600 700
0.01
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0.04
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Spectrometer
FPA
Reflective slit