A CMOS Pixel With Embedded ADC, Digital CDS and Gain Correction Capability for Massively Parallel Imaging Array

Abstract

In the paper, a CMOS pixel has been proposed for imaging arrays with massively parallel image acquisition and simultaneous compensation of dark signal nonuniformity (DSNU) as well as photoresponse nonuniformity (PRNU). In our solution the pixel contains all necessary functional blocks: a photosensor and an analog-to-digital converter (ADC) with built-in correlated double sampling (CDS) integrated together. It is implemented in standard $0.18~\mu \text {m}$ CMOS technology. The size of the pixel with 9-bit resolution is $21~\mu \text {m}\,\,\times 21\,\,\mu \text {m}$ . Measurements of the $128\times 128$ pixel array confirm functionality of the proposed solution. CDS reduces dark FPN from 12 LSB (3%) to 0.8 LSB (0.2%) and light FPN from 14 LSB (3.7%) to 7 LSB (1.8%). Further reduction of the light FPN (to ~1 LSB) was achieved by compensating PRNU using massively parallel innovative digital multiplication which features good resolution (1/511), does not disturb CDS executed at the same time, and can be implemented within a small pixel area.