optical position sensor for the vws. project update
DESCRIPTION
Optical position sensor for the VWS. Project Update . Student Meeting 23/07/2012. 1. Initial remarks. A) Tests have validate the usage of SMF 9/125um assembly B) Focuser configuration has proved to be the best in terms of accuracy and coupling efficiency. - PowerPoint PPT PresentationTRANSCRIPT
Optical position sensor for the VWS. Project Update
Student Meeting 23/07/2012
1. Initial remarks• A) Tests have validate the usage of SMF 9/125um assembly • B) Focuser configuration has proved to be the best in terms of accuracy
and coupling efficiency.• C) Commercial lens 352400 with Thorlabs housing has proved it’s
performance and low aberration (UHV and High Temp comp).• D) Tests to be done:
– 1. Validate usage of commercial focuser from Schafter + Kirhhoff: UHV and High Temp comp, in principle.
– 2. Validate usage of External focuser (calibration from outside very long focal distance 9cm)
– 3. Which side of the disk to use (High ref chrome or Glass side)– 4. Accuracy comparisons with commercial enconder RON 225
2.Components point of view• Laser: BOB1310FP (1310nm) from “BOB Lasers”• Photodiode: PTIN155ST83-N-O (1310nm) from “Laser Comp.”• Circulator: PIOC-3-13-P-2-1-55 from “Fiberer”• Optical fibre air side: Standard Cern Draka RadHard fibre.• Feedthrough + Adapter:FO-SM-1300-16CF + FO-FC CV from “Lewvac” • Optical fibre UHV Side (FC/PC-FC/APC): Sedi-Fibres? NASA connectors• Focuser: 352440 lens + Thorlabs housing from “Thorlabs” or 60FC-4-A4-03
+ 5M-A4-0-03-S from “Schafter + Kirchhoff”
UHV SideAir Side
FeedthroughCF16 Flange
1.5 mm
Laser Diode
Photodiode
Optical Circulator
1x Optical Fiber (250m)
25.4 mm
10.2 mm
D1 = 6.886 mmD2 = 2.23mm +- 25 um
3 mm
Disk
FC/PC FC/PC
FC/APC
UHV FibreFC/PC – FC/APC
Focuser
3. Tests done:• A) Validation Commercial focuser:
oSchafter + Kirchhoff
o352440 Lens + Thorlabs Housing o Lens adjust and fixing: Retaining Ringso Difficult adjust: Change D1 = Change D2o Possible misalignments for vibrationo No glues
o Lens adjust: High precision screwso Lens fixing: Indirect clampingo Independent lens calibrationo Compact systemo No glueso Better coupling eff. (Good aligned)
3. Tests done:• B) Signal Acquisition and analysis:
– 1. Duty Cycle: Why D<< 50%??!! D=43%
• Simulations : 49-50%
• Practical: 42 – 46 %
Cause 1: Reflection parts of each track are smaller than non reflection.
Cause 2: Rectangular tracks, not precise angular information.
3. Tests done:• B) Signal Acquisition and analysis:
– 1.Duty cycle: • Solution -> Detecting only rising edge• Resolution -> Reduced to 1/2