Differential image sensor with high common mode rejection

Abstract

Image processing applications like tracking of moving objects typically involve the subtraction of two successive images. Doing this without the need for a large digital memory requires a sensor chip that does the subtraction in the analog domain. This paper provides insight in the critical issues of the design of such a differential image sensor. The presented sensor has two operation modes: a very low noise correlated double sampling (CDS) mode and a differential image (DI) mode. This sensor is optimized to have a high common mode rejection ratio (CMRR) which results in a small influence from the content of the image onto the differential image.