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Entry  Thu Jul 24 17:11:18 2014, Evan, DailyProgress, optic, Calibration for scattered light measurement power.pdfccdCal.pdf10.pdf
    Reply  Fri Jul 25 08:12:40 2014, Evan, DailyProgress, optic, Calibration for scattered light measurement ccdCal.pdf
       Reply  Fri Jul 25 14:21:34 2014, Evan, DailyProgress, optic, Calibration for scattered light measurement cal.pdf
Message ID: 1458     Entry time: Fri Jul 25 08:12:40 2014     In reply to: 1457     Reply to this: 1459
Author: Evan 
Type: DailyProgress 
Category: optic 
Subject: Calibration for scattered light measurement 


The first attachment is the BRDF of the diffuser based on the power data. The second is the inferred calibration between total CCD counts (with background counts subtracted) and scattered power. The correlation is not great. We may want to retake this data with the room lights off, and also we may want to take multiple exposures per angle setting (that way we can make some estimate of the uncertainty in the CCD counts).

 I put the boom at 15° and took four sets of five exposures. Then I ran my image processing code again to get an uncertainty in the count values. I get the following:

  • Beam incident, room lights on: 546(31) × 103 cts
  • Beam blocked, room lights on: 417(9) × 103 cts
  • Beam incident, room lights off: 547(34) × 103 cts
  • Beam blocked, room lights off: 410(2) × 103 cts

For each set of five, the nominal value is the mean and the uncertainty is the standard deviation of the total counts within the 200×200 pixel region around the beam. Again the exposure time is 100 µs and there was an RG1000 filter in front of the camera lens.

Using a fractional uncertainty of 31/546 = 0.057 for yesterday's background-subtracted total counts, I reran the calibration code. The new plot is attached. The calibration slope (and its uncertainty) doesn't change much, but we can see that the uncertainties in the total counts are quite large. Do we need to improve this before moving on to the AlGaAs BRDF measurement?

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