CMOS IMAGE SENSOR WITH PIXEL LEVEL A/D CONVERSION

摘要

An image sensor (10) formed using a CMOS process is described herein which includes a pixel array core (12) of phototransistors whose conduc tivities are related to the magnitude of light impinging upon the phototransistors. The analog signals generated by the phototransistors are converted to a serial bit stream by an A/D converter connected at the output of each phototransistor and formed in the immediate area of each phototransistor within the array core (12). Thus, a separate digital stream for each pixel element (14) is output from the array core (12), and parasitic effects and distortion are minimized. In one embodiment, a filter circuit (16) is connected to an output of the array core (12) for converting the individual digital streams form each pixel element (14) to multi-bit values corresponding to the intensity of light impinging on the phototransistor.