A Pipelined Temporal Difference Imager

A 189/spl times/182 active pixel sensor (APS) for temporal difference computation is presented. The temporal difference imager (TDI), fabricated in 0.5-/spl mu/m 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 /spl mu/m by 25 /spl mu/m (using 0.7-/spl mu/m 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.