# Megapixel Photon-Counting Color Imaging using Quanta Image Sensor

## TL;DR

This paper introduces the first megapixel color Quanta Image Sensor capable of high-resolution, low-light photon counting, achieved through a novel joint demosaicing-denoising algorithm that effectively reconstructs color images from extremely sparse photon data.

## Contribution

The paper presents a pioneering megapixel color QIS with a specialized reconstruction algorithm, enabling high-resolution color imaging in extremely low-light conditions.

## Key findings

- Successful demonstration of 1024x1024 color QIS imaging
- Effective reconstruction at a mean exposure of a few photons per pixel
- Superior low-light color imaging performance

## Abstract

Quanta Image Sensor (QIS) is a single-photon detector designed for extremely low light imaging conditions. Majority of the existing QIS prototypes are monochrome based on single-photon avalanche diodes (SPAD). Passive color imaging has not been demonstrated with single-photon detectors due to the intrinsic difficulty of shrinking the pixel size and increasing the spatial resolution while maintaining acceptable intra-pixel cross-talk. In this paper, we present image reconstruction of the first color QIS with a resolution of $1024 \times 1024$ pixels, supporting both single-bit and multi-bit photon counting capability. Our color image reconstruction is enabled by a customized joint demosaicing-denoising algorithm, leveraging truncated Poisson statistics and variance stabilizing transforms. Experimental results of the new sensor and algorithm demonstrate superior color imaging performance for very low-light conditions with a mean exposure of as low as a few photons per pixel in both real and simulated images.