calibration by shot noise.mcd

This note gives a derivation for generating the ADC to electron calibration (electron transfer function) from shot noise. This is a common method and one example can be found at:
http://www.eso.org/~gfinger/sb256/lowdoped/lowdoped-1.html
H. Wieman
Aug. 2005

pixel ADC value from frame 0

pixel ADC value from frame 1

CDS ADC value for a pixel

CDS standard deviation in ADC values, includes shot noise plus pixel read noise (see Eq. 2 below). The shot noise component depends on the the charge integrated between frame reads.

Pixel read noise in ADC values. This is the electronic noise not including shot noise. This is one of the parameters that gets determined in this analysis.

Eq. 1

Number of electrons from CDS ADC values

calibration constant, number of electrons per ADC count. It is this constant that we extract from measurements of noise. In principle separate values of c and sp can be extracted for each pixel

The shot noise, rms number of electrons

The shot noise added in quadrature with the electronics noise for the two reads equals the CDS standard deviation.

Eq. 2

Combine Eq. 1 and 2 to eliminate Ne

Plot

(the variance) vs

for different pixels and integrated charges. 1/c is obtained from the slope and electronic read noise is obtained from the zero intercept.