Optical Position Sensor for the VWS

Tolerances and possibilities

Jose Luis SirventJonathan Emery

Student Meeting 12– February -2012

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%

Signal appearance◦ 30Khz◦ 0.0422 mWpp

1.Transmission

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

2.Reflection

3.1 Focuser with commercial components

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!!)

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%

3.Focusing

4.35 -+ 0.2 mm

Fit with sinusoid

3.Focusing

4.Double Pattern (Work in progress)

5.Tolerances Table

Transmission (50mVpp) Reflection (80mVpp)

Focuser 800mVpp

LASER DIODES Reception Expected dBmCompany Component Class Max Curr. Max Power (dBm) Max Power (mW) Stability Comments Trans Ref Focus Col

OPTEK OPF372A GaAIAs LED 100mA -10 0.1 Stable Fine, Low Power -34.33 -32.35 -19.55 -KYOSEMI KLD085VC VCSEC 12mA 1.59 1.44 Stable -22.74 -20.76 -7.96 -

LASER COMP PL85B002ST83-T-0 45mA 6.98 5 Noisy Noisy (Reflections) -17.35 -15.37 -2.57 -

Last weeksPHOTODIODES

Company Component Class Sensibility (dBm) Sensibility (mW) Saturation (dBm) Saturation (mW) CommentKYOSEMI KPGX1G GaAs PD-TIA -24 3.98E-03 - -

High-Pass filter F> 1MhzKYOSEMI KPIX150M-H33 Si PD-TIA -31 7.94E-04 - -KYOSEMI KPIXAIG-T-ST Si APD-TIA -33 5.01E-04 - -

OPTEK OPF562A Si PD -41 7.94E-05 -7 0.200

LASER COMP PDSIU500ST83-W-0 Si PD -21.9 6.46E-03 3 1.995 TIA Circ OK but F<2Mhz

6. Emiters Receivers Analysis

6. Emiters Receivers Analysis

Kyosemi Laser Components

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)

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)

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.

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

6.Accuracy Improvements