A Dual-Mode CMOS Image Sensor Based on in-Pixel Frame Differencing

In this article, we introduce a dual-mode CMOS image sensor designed for pixel-level motion detection. A compact computational pixel structure is designed with a pitch of 8 mu m and a fill factor of 22.1%. We have implemented a current-mode motion detection module to generate motion signals and control the operation of the column-level analog-todigital converter (ADC) to optimize power efficiency. The data rate can be adjusted by tuning the threshold currents. A 128 x 128 image sensor is fabricated in a 0.18-mu m CMOS process. Test results indicate that the imager can output full image at 60 frames per second (fps). Of significant note are the substantial power consumption reductions achieved in both of the two motion detection modes, amounting to 30.7% and 60%, respectively. In data compression mode, a 3.02 pJ/pixel/frame Figure of Merit (FoM) is achieved.