Patent ID: 8275213

Claim:
An electronic method of correcting a column gain mismatch in an image sensor, implemented in circuitry to perform the method, the method comprising: reading a test signal from at least one test pixel in the image sensor; comparing the test signal to a target value; calculating a correction value based on comparing the test signal to the target value; storing the correction value in a memory; reading a photo-pixel signal; determining a black reference value from a black reference pixel, wherein the black reference pixel is a pixel which has not been exposed to light; and modifying the photo-pixel signal based on the correction value stored in memory and the black reference value, in order to form a modified photo pixel signal; and outputting the modified photo-pixel signal; wherein for each column in the sensor, each photo-signal is modified according to: data out=(data in−blackref)×(1+Δ i )+blackref where Δ i equals n i /2 s ; n i is the signed correction values stored in the memory for each column; and s is a scaling parameter.