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Published byCory Newman Modified over 8 years ago
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Keyence reproducibility study D. Lawrence P. O’Connor 2/2/09
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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: 1.Gantry centered over optical flat 2.Gantry repeatedly move to 5 widely-spaced reference points on flat 3.Gantry perform dense (2x2mm) scan of flat, interrupt dense scan every ~ 60s to measure 5 reference points
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Keyence noise vs. averaging choose 128-point averaging to keep noise below 0.1um
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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:
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Cond. 1, 43 minute moving average full dataset 33 minute section
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Cond. 1, correlation (moving average Disp – Temp over 65 hrs)
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Cond. 1, 11 min moving average
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Cond. 1, 160s moving average
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Cond. 1, 88hr run started 1/29/09, fan off temp vs. time z vs. time correlation
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Condition 1, long run started 1/29/09, 88 hrs., fan off temp. vs. timez vs time evidence of oscillation
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Condition 1, 88hr scan started 1/29/09 Rate of change of temperature and time during scan
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Condition 2: gantry scan of 5 reference points Reference points located at N,S,E,W, and center of flat 12 3 4 5
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Plane fit to the 5 points vs. time Z-intercept X-slopeY-slope
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z (rel) vs. timetemperature vs. time z-intercept vs. temperature
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Condition 2, longer scan slopes intercept z-height of 5 refpoints temperature
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Cond. 2, 1/29/09, fan off 3.5um/deg C
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Cond. 2, fans off
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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
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scan patternz-height of 5 reference points vs time 16 repeat scans Condition 3: z-height vs. time
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z vs. x and y (first scan)
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first pass residuals, uncorrected
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residuals before and after correction for drift blue – no drift correction green – drift corrected
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