A CMOS imager with negative feedback pixel circuits and its applications

We investigated a negative feedback method for adding functionality to a CMOS image sensor. Our sensor effectively uses the method to set any intermediate voltage into a photodiode capacitance while a pixel circuit is in motion. The negative feedback reset functions as a noise cancellation technique and can obtain intermediate image data during charge accumulation. As an above application, dynamic range compression is achieved by individually selecting pixels and by setting an intermediate voltage or performing quasi-holding with respect to each pixel. Additionally, we achieved duplicated interlaced processing and were able to output frame-difference images without frame buffers. The experimental results obtained with a chip fabricated using a 0.25-μm CMOS process demonstrate that dynamic range compression and intra-frame motion detection are effective applications of negative feedback resetting.