Sources of Noise

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Photon Transfer Function

total noise Sources of Noise

Total Noise

measuring noise Sources of Noise

Measuring Noise

  • With the well behaved Poisson statistics of photon noise, sP2=P, if we vary P (the amount of light) and measure s2 and ADU, we can estimate K and stotal
  • Method
    • Sample pair of images with uniform illumination
    • Subtract and measure variance (s2) over an area to remove fixed pattern noise
    • Measure mean gray level (ADU) from the same area
    • Increase the signal and repeat
    • Plot corrected variance (s2/2) as a function of the mean ADU

      mean adu Sources of Noise

See James R. Janesick, Scientific Charge-Coupled Devices,  SPIE Press, 2001.

Log-log plot of s2 vs ADU

photon transfer curve Sources of Noise 

  • ADU = K(QEP+stotal) (Analog to Digital Units)

sp2 = (QEP) = Ne

  • At Ne >> stotal , s2 =sp2
  • s2 = (ADU + stotal)/K

Linear plot of variance (s2) versus mean (ADU)
Slope = 1/K

See James R. Janesick, Scientific Charge-Coupled Devices, SPIE Press, 2001.