A CMOS 64 # 64 pixel area image sensor chip using Sigma-Delta modulation at each pixel for A#D conversion is described. The image data output is digital. The chip was fabricated using a 1.2#mtwo layer metal single layer poly n-well CMOS process. Each pixel block consists of a phototransistor and 22 MOS transistors. Test results demonstrate a dynamic range potentially greater than 93dB, a signal to noise ratio #SNR# of up to 61dB, and dissipation of less than 1mW with a 5V power supply. 1 Boyd Fowler, Abbas El Gamal, and David X. D. Yang 2 Charge-coupled devices #CCD# are at present the most widely used technology for implementing area image sensors. CCD image sensors have their shortcomings, however. They su#er from low yields, they consume too muchpower #3#, and they are plagued with SNR limitations due to the shifting and detection of analog charge packets, and the fact that data is communicated o# chip in analog form. Several alternatives to CCD area image sensors that use st...

Most of today's video and digital cameras use CCD image sensors, where the electric charge collected by the photodetector array during exposure time is serially shifted out of the sensor chip resulting in slow readout speed and high power consumption. Recently developed CMOS image sensors, by comparison, are read out non-destructively and in a manner similar to a digital memory and can thus be operated at very high frame rates. A CMOS image sensor can also be integrated with other camera functions on the same chip ultimately leading to a single-chip digital camera with very compact size, low power consumption and additional functionality. CMOS image sensors, however, generally su#er from lower dynamic range than CCDs due to their high read noise and non-uniformity. Moreover, as sensor design follows CMOS technology scaling, well capacity will continue to decrease, eventually resulting in unacceptably low SNR.