Image sensor with direct digital correlated sampling

摘要

A CMOS image sensor is provided in which correlated double sampling is performed entirely in the digital domain. In an exemplary embodiment, the image sensor includes a plurality of imager cells arranged in rows and columns, where the imager cells of a particular column are coupled to a column data line of that column. Each active imager cell is capable of selectively providing a first output on an associated column data line indicative of a reset level during a first sampling interval. During a second sampling interval, each active imager cell provides a signal output on the associated column data line indicative of an amount of light incident upon that imager cell. At least one analog to digital (A/D) converter is coupled to the column data lines and converts the first and signal outputs on each column data line to first and second digital codes, respectively, to complete a correlated double sampling operation. The invention eliminates the need for analog capacitors to store the reset and signal levels.