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Keyence reproducibility study

Keyence reproducibility study. D. Lawrence P. O’Connor 2/2/09. Setup. Optical flat on 3-ball stage spanning cutout in optical table Softwall cleanroom fans may be turned on or off Temperature measurement from Netbotz appliance on W wall of lab

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Keyence reproducibility study

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  1. Keyence reproducibility study D. Lawrence P. O’Connor 2/2/09

  2. Setup • Optical flat on 3-ball stage spanning cutout in optical table • Softwall cleanroom fans may be turned on or off • Temperature measurement from Netbotz appliance on W wall of lab • Alternate temperature measurement from Cryo-con PtRTDs on optical bench near CCD test Dewar • Keyence averaging parameter 128 to keep noise < 0.1um • Log time, temperature, Keyence reading, gantry XY-position for 3 motion conditions: • Gantry centered over optical flat • Gantry repeatedly move to 5 widely-spaced reference points on flat • Gantry perform dense (2x2mm) scan of flat, interrupt dense scan every ~ 60s to measure 5 reference points

  3. Keyence noise vs. averaging choose 128-point averaging to keep noise below 0.1um

  4. Condition 1: no gantry motion • log z-displacement, temp every 20s for 65 hours starting 1/9/09 17:10 • fan ON continuously • raw data:

  5. Cond. 1, 43 minute moving average 33 minute section full dataset

  6. Cond. 1, correlation (moving average Disp – Temp over 65 hrs)

  7. Cond. 1, 11 min moving average

  8. Cond. 1, 160s moving average

  9. Cond. 1, 88hr run started 1/29/09, fan off correlation temp vs. time z vs. time

  10. Condition 1, long run started 1/29/09, 88 hrs., fan off temp. vs. time z vs time evidence of oscillation

  11. Condition 1, 88hr scan started 1/29/09 Rate of change of temperature and time during scan

  12. 4 1 2 5 3 Condition 2: gantry scan of 5 reference points • Reference points located at N,S,E,W, and center of flat

  13. Plane fit to the 5 points vs. time Z-intercept X-slope Y-slope

  14. z (rel) vs. time temperature vs. time z-intercept vs. temperature

  15. Condition 2, longer scan slopes z-height of 5 refpoints intercept temperature

  16. 3.5um/deg C Cond. 2, 1/29/09, fan off

  17. Cond. 2, fans off

  18. Condition 3: dense scan with periodic re-measurement of reference points • scan entire surface of 8” diameter optical flat at 2mm grid • approx 4300 points • scan at ~ 1.02s/point  about 1.6 hrs to scan, serious temperature drift error likely • to compensate temperature drift: • assume SHAPE of flat doesn’t change • track rigid body motion (tip,tilt,piston) • choose 5 reference points (N,S,E,W,Center) • return to reference points every ~ 1 minute to track common-mode motion due to temperature • choose diagonal scan pattern to distribute x- and y-gantry motion equally in time • repeat scan 16 times over Jan. 17 – 18 2009

  19. Condition 3: z-height vs. time scan pattern z-height of 5 reference points vs time 16 repeat scans

  20. z vs. x and y (first scan)

  21. first pass residuals, uncorrected

  22. residuals before and after correction for drift blue – no drift correction green – drift corrected

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