A 3.96-μm, 124-dB Dynamic-Range, Digital-Pixel Sensor With Triple- and Single-Quantization Operations for Monochrome and Near-Infrared Dual-Channel Global Shutter Operation

Abstract

This article presents a 3.96- μm, 640 × 640 pixel stacked digital pixel sensor capable of capturing co-located monochrome (MONO) and near-infrared (NIR) frames simultaneously in a dual-channel global shutter (GS) operation. A super-pixel structure is proposed with diagonally arranged 2 × 2 MONO and NIR sub-pixels. To enhance visible light sensitivity, large and small non-uniform micro-lenses are formed on the MONO and NIR sub-pixels, respectively. Each floating diffusion (FD) shared super-pixel is connected to an in-pixel analog-to-digital converter and two banks of 10-bit static random access memories (SRAMs) to enable the dual-channel GS operation. To achieve high dynamic range (DR) in the MONO channel, a triple-quantization (3Q) operation is performed. Furthermore, a single-channel digital-correlated double sampling (D-CDS) 3Q operation is implemented. The fabricated sensor achieved 6.2-mW low power consumption at 30 frames/s with dual-channel capture. The MONO channel achieved 124-dB DR in the 3Q operation and 60 dB for the NIR channel. The sensor fits the stringent form-factor requirement of an augmented reality headset by consolidating MONO and NIR imaging capabilities.