A 25M Points/s Back-Illuminated Stacked SPAD Direct Time-of-Flight Depth Sensor with Equivalent Time Sampling for Automotive LiDAR

Abstract

This paper presents technologies at Single Photon Avalanche Diode (SPAD) direct Time-of-flight (ToF) depth sensor and Light Detection and Ranging (LiDAR). Method of readout by under-pixel differential comparator and the threshold control can select either to prioritize distance accuracy or acquisition of reflectance information. The equivalent time sampling (ETS) at 3 GHz improves depth accuracy. Furthermore, subsequent 250MHz re-sampling and the depth information extraction pipeline relaxes the operation frequency maintaining the depth accuracy and approximately 98% data size reduction. Sensor delivers distance measurement for 520 effective macro pixels with 0.05° vertical angular resolution at 120° horizontal Field of View (FoV) and 20fps, resulting in 25M points/s (pts/s) ranging data and detection of 25cm object at 250m.

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