Two Techniques to Reduce Gain and Offset Errors in CMOS Image Sensors Using Delta-Sigma Modulation
A per-column, delta-sigma, analog-to-digital converter for use in CMOS image sensors is reported. Two techniques, subtraction and preconditioning, are proposed to compensate for the column-to-column mismatches and the resulting fixed-pattern noise introduced into the image. Equations governing the operation of the proposed topology are developed. Experimental results verify that even in the presence of very large offsets, such as a 200 mV mismatch in the MOSFETs' threshold voltages, the proposed topology operates as desired.
Yap, Kuangming and Baker, R. Jacob. (2012). "Two Techniques to Reduce Gain and Offset Errors in CMOS Image Sensors Using Delta-Sigma Modulation". IEEE Workshop on Microelectronics and Electron Devices (WMED), 1-4. http://dx.doi.org/10.1109/WMED.2012.6202621