Research on Dark Current Compensation Method of Analog Front end Based on Synchronous Adaptive Matching

In order to suppress the influence of dark current of pixel array in the exposure stage on the dynamic range and output image quality of image sensor, based on the synchronous adaptive dark current tracking mechanism, this paper proposes an integrated compensation method for dark current at the front of the readout circuit. While sampling and outputting the effective photoelectric signal, the influence of dark current is eliminated synchronously in the passive processing stage. This method not only compensates for the influence of dark current in different areas on the effective photoelectric signal, but also solves the attenuation problem of the dynamic range of the readout circuit by the traditional dark current elimination method. Based on this scheme, our team has carried out a 752$\times$ 512 array scale CMOS image sensor on 55 nm CMOS process, including detailed circuit design, layout design and back-end physical verification. The verification results show that the minimum compensation accuracy of the sampling amplifier circuit with integrated dark current correction technology can reach 12 bit, the maximum compensation range can reach 500 mV, and the single column power consumption is only 15.84 $\mu$ W. At the same time, $1 \sim 4$ times of gain amplification can be achieved, and the minimum gain step is 6.25%. The effect of dark current on the image quality and dynamic range of CMOS image sensor is eliminated from the analog front-end, which provides a theoretical support for high-end, high-performance CMOS image sensor design.