Review of Quanta Image Sensors for Ultralow-Light Imaging

The quanta image sensor (QIS) is a photon-counting that has been implemented using different electron devices, including impact ionization-gain such as the single-photon avalanche detectors (SPADs), and low-capacitance, high conversion-gain modified CMOS sensors (CIS) with deep subelectron read noise and/or low readout signal chains. This article primarily focuses on CIS QIS, but recent progress of both types addressed. Signal processing progress, denoising, critical to improving apparent signal-to-noise ratio, also reviewed an enabling coinnovation.