Performance Analysis of a Color CMOS Photogate Image Sensor

The performance of a color CMOS photogate image sensor is reported. It is shown that by using two levels of correlated-double sampling, it is possible to effectively cancel all fixed-pattern noise due to read-out circuit mismatch. Instead the fixed-pattern noise performance of the sensor is limited by dark current non-uniformity at low signal levels, and conversion gain non-uniformity at high signal levels. It is further shown that the imaging performance of the sensor is comparable to low-end CCD sensors but inferior to that reported for high-end CCD sensors due to low quantum efficiency, high dark current, and pixel cross-talk. As such, the performance of CMOS sensors is limited at the device level rather than at the architectural level. If the imaging performance issues can be addressed at the fabrication process level without increasing cost or degrading transistor performance, CMOS has the potential to seriously challenge CCD as the solid-state imaging technology of choice due to low power dissipation and compatibility with camera system integration.