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Advanced Optical Position Sensor for VWS: Tolerances and Possibilities

Explore the detailed transmission, reflection, and focusing capabilities of the optical position sensor developed by Jose Luis Sirvent and Jonathan Emery at the 2012 Student Meeting. Learn about the accuracy improvements, signal appearances, and tolerances achieved in this cutting-edge technology.

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Advanced Optical Position Sensor for VWS: Tolerances and Possibilities

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  1. Optical Position Sensor for the VWS Tolerances and possibilities Jose Luis Sirvent Jonathan Emery Student Meeting 12– February -2012

  2. 1.Transmission • Loss of -3dB: • Horizontal plane: Disk-Fiber +-0.25mm • Vertical plane: Fiber-Fiber misalignment 60um • Angular tolerance: 0.5 deg • Signal received ~ 0.37%

  3. 1.Transmission • Signal appearance • 30Khz • 0.0422 mWpp

  4. 2.Reflection • Loss of -3dB: • Horizontal plane: Disk-Fiber +-0.3mm • Vertical plane: Width of the slides • Angular tolerance ~ +-2.5 deg • Signal received ~ 0.58%

  5. 3.Focusing • 3.1 Focuser with commercial components

  6. 3.Focusing • Loss of -3dB: • Horizontal plane: Fiber-Lens 7mm -+ 250um • Horizontal plane: Lens-Disk 2.23mm -+60um (Too small?) • Vertical plane: Slits width • Angular tolerance ~ +-2deg • Signal received ~ 11% (Improvement > Factor 10!!)

  7. 3.Focusing • Improvement of tolerances: • Defocus  Bigger spot size • Horizontal Plane: Fiber - Lens 4.29mm +- ? • Horizontal Plane: Lens – Disk 4.35mm +- 200um • Vertical plane ~ +-2deg • Signal received ~ 11% 4.35 -+ 0.2 mm

  8. 3.Focusing • Fit with sinusoid

  9. 4.Double Pattern (Work in progress)

  10. 5.Tolerances Table Focuser 800mVpp Transmission (50mVpp) Reflection (80mVpp)

  11. 6. Emiters Receivers Analysis

  12. 6. Emiters Receivers Analysis Laser Components Kyosemi

  13. 6.Accuracy Improvements • Disk D=14cm  8796 slots of 50um • Actual accuracy: 710 uRad. • Specifications: 25 uRad. • Needed Improvement of factor 30. • How to reach specifications (Interpolation): • 1.Offline Processing (Software requirements) • 2.Online Processing (Possible by hardware)

  14. 6.Accuracy Improvements • Disk D=14cm  8796 slots of 50um • Actual accuracy: 710 uRad. • Specifications: 25 uRad. • Needed Improvement of factor 30. • How to reach specifications (Interpolation): • 1.Offline Processing (Software requirements) • 2.Online Processing (Possible by hardware)

  15. 6.Accuracy Improvements • 2.Online Processing • 1. Interpolation with previous cycle reference • Source of errors: Bad measurement in previous cycle = interpolations errors in next. • Allways there will be a delay of 0.5 cycle. • Possible improvement: Histeresys when crosing zero.

  16. 6.Accuracy Improvements • 2.Online Processing • 2. Interpolation of Sin-Cos Encoders: • Two fibers if working with Focuser (displaced 90deg) • No errors or delay: Relationship between signals • Variations in speed applied immediately. • Interpolation Unit + Quadrature decoder

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