A pipelined temporal difference imager

A 189×182 active pixel sensor (APS) for temporal difference computation is presented. The temporal difference imager (TDI), fabricated in 0.5-μm CMOS process, contains in-pixel storage elements for a previous image frame. Difference double-sampling circuits are used to suppress the fixed pattern noise in both images and to compute the difference between the corrected images. The pixel area occupies 25 μm by 25 μm (using 0.7-μm scalable rules), with fill factor of 30%. A novel pipelined readout technique is described, which is used to improve the accuracy of the temporal difference computation. With this pipelined readout architecture, >8-bit precision for the difference image and low spatial droop across the difference image is achieved. The chip consumes 30 mW at 50 fps from a 5-V power supply.