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Optical position sensor for the VWS. Project Update

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.

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Optical position sensor for the VWS. Project Update

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  1. Optical position sensor for the VWS. Project Update Student Meeting 23/07/2012

  2. 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

  3. 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” • Opticalfibre air side: Standard CernDrakaRadHardfibre. • 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”

  4. 3. Tests done: • 352440 Lens + Thorlabs Housing • Lens adjust and fixing: Retaining Rings • Difficult adjust: Change D1 = Change D2 • Possible misalignments for vibration • No glues • A) Validation Commercial focuser: • Schafter + Kirchhoff • Lens adjust: High precision screws • Lens fixing: Indirect clamping • Independent lens calibration • Compact system • No glues • Better coupling eff. (Good aligned)

  5. 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.

  6. 3. Tests done: • B) Signal Acquisition and analysis: • 1.Duty cycle: • Solution -> Detecting only rising edge • Resolution -> Reduced to 1/2

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