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Fast conversion factor measurement of a CCD

using Images withvertical gradient

Charge Transfer Efficiency based on

The variance of the signal in flat

Field images, gain correction

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Fast conversion factor measurement of a CCD using Images with vertical gradient

Introduction

Fast way to realize Photon Transfer CurveAppropriate to use this technique during CCD tuning

The method

Im1 + Im2

For each line i of Im: The mean is calculated (Si)

2Im =

Is = Im1 - Im2For each line i of Is: The variance is calculated (σi

2)

Each (Si, σi2) pair is plotted

Im1 and Im2, two TDI images

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Results.

1. Preliminary work. Mask cosmetic defects.2. Flat Field of TDI images.3. Weighted least square method.4. Automatic detection of the beginning of the non

linearity regime.5. User friendly program.

Future work.

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Charge Transfer Efficiency based on the variance of the signal in flat Field images, gain correction.

Change in Variance in Flat Field (CVF) Method.

Is = Im1 - Im2For each line (column) i of Is: The variance is calculated (σi

2)Each (i, σi

2) pairis plotted

Results

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How can I correlate previous plots to the CTE?

Expression of the variance affected by the CTE (a = 1- b)

Conclusion

The best fit line of the previous plot:

Gives us the Charge Transfer Efficiency:

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Results, Simulated data.

Results, Real data.Conclusion

Results promising.• Mask cosmetic defects• Work in 2d instead of 1d• Direct comparison CVF versus

ESO Fe55 setup• User friendly program