Patent ID: 8199225

Claim:
A method for compensating for column fixed pattern noise in an image sensor, wherein the image sensor includes a plurality of photoactive pixels and a plurality of dark reference pixels arranged in rows and columns to form a pixel array, the method comprising: reading out, at a first gain level of pixel readout circuitry, a dark signal value from a given number of dark reference pixels in each column; determining an initial column offset correction for one or more columns in the array using respective dark signals read out at the first gain level; detecting changes to different gain levels of the pixel readout circuitry; repeatedly scaling the initial column offset corrections to generate column offset corrections for each of the different gain levels in response to each detected change to a respective different gain level; and adjusting the column offset corrections for each of the different gain levels based on reading out a varying integer number of the dark reference pixels in each column, wherein the varying integer number varies based on additional data.