High dynamic range CMOS image sensor with conditional reset

In this paper, we propose a new image pixel structure for high dynamic range operation, which is based on a multiple sampling scheme and conditional reset circuits. To expand the dynamic range of the sensor, the output of the pixel is sampled multiple times in an integration time. In each sampling, the output of the pixel is compared with a reference voltage, and the result of this comparison activates the conditional reset circuit. The times of conditional reset during the integration contribute to the increase of the dynamic range of the sensor. Dynamic range can be increased to N, where N is the sampling times in an integration time. The test chip was fabricated with a 0.65-μm CMOS technology (2-P, 2-M).