39 000-Subexposures/s Dual-ADC CMOS Image Sensor With Dual-Tap Coded-Exposure Pixels for Single-Shot HDR and 3-D Computational Imaging
Rahul Gulve, Navid Sarhangnejad, Gairik Dutta, Motasem Sakr, Don Nguyen, Roberto Rangel, Wenzheng Chen, Zhengfan Xia, Mian Wei, Nikita Gusev, Esther Y. H. Lin, Xiaonong Sun, Leo Hanxu, Nikola Katic, Ameer Abdelhadi, Andreas Moshovos, Kiriakos N. Kutulakos, Roman Genov
Abstract
A dual-tap coded-exposure-pixel (CEP) image sensor is presented and validated in two computational imaging applications. The NMOS-only data-memory pixel (DMP) reduces the transistor count yielding a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7{-}\mu \text {m}$ </tex-math></inline-formula> pitch. One frame period can include up to 900 subexposures when operating at 30 frames/s, corresponding to 39 000 coded subexposures/s. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$320\times 320$ </tex-math></inline-formula> -pixel sensor features two readout modes using column-parallel analog-to-digital converters (ADCs). ADC1 is a conventional high-accuracy <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \Sigma $ </tex-math></inline-formula> -modulated ADC that digitizes pixel voltage at the end of every frame period, and ADC2 is a fast energy-efficient comparator that compares the pixel voltage with a constant reference voltage during each subexposure. The outputs of the 12-bit frame-rate ADC1 and the 1-bit subexposure-rate ADC2 are adaptively combined to boost the native dynamic range of the uncoded pixel by over 57 dB, demonstrating over 101-dB dynamic range in intensity imaging. In the second demonstrated application, combined with machine-learned projected illumination patterns, the CEP camera enables single-shot structured-light 3-D imaging at the native resolution and the nominal 30 frames/s video rate.