Imaging systems and methods for reducing dark signal non-uniformity across pixels

Abstract

An image sensor may include an array of image pixels. Control circuitry coupled to the array of pixels may be configured to operate the image pixels in an overflow mode of operation, in which each pixel generates an overflow image signal and a complete image signal from a single exposure time period. The overflow image signals and the complete image signals from the pixels may be used to generate a high dynamic range image. While the floating diffusion region in each pixel is not in use, control circuitry may control that pixel to generate a reference signal at the floating diffusion region indicative of pixel-specific dark signal noise. Processing circuitry may mitigate for dark signal non-uniformity across the pixels by correcting the complete image signals using the reference signal to remove dark signal noise in the complete image signals.