Patent ID: 8269864

Claim:
A method for determining outlier dark signals when producing column offset corrections used to compensate 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: obtaining a global offset window for all of the columns in the pixel array, wherein the global offset window defines an acceptable maximum dark signal and an acceptable minimum dark signal for all of the columns; reading out a dark signal from a given number of dark reference pixels in each column; determining whether one or more of the dark signals from each column are outside the global offset window, and if so, compensating for each dark signal outside the global offset window; determining a column offset correction for each column using dark signals within the global offset window; and after a given number of dark signals have been read out of the pixel array, determining a local offset window for each column in the pixel array, wherein the local offset window defines an acceptable maximum dark signal and an acceptable minimum dark signal for each column.