Single-Shot Pulsed-LiDAR SPAD Sensor with on-chip Peak Detection for Background Rejection

Abstract

In recent years, direct Time-of-Flight techniques have been exploited with single-photon detectors to provide long distance ranges and high-frame rates measurements. Detectors based on Silicon Photon Multipliers commonly collect repetitive laser shots to reconstruct a histogram of the TOF of returning pulsed-laser photons, so to discriminate between signal, background light, and detector noise. Instead of performing multi-shot measurements, we propose a single-shot technique capable to provide just one useful TOF per laser pulse, corresponding to the returning peak signal with the highest number of concurrent photons. In this way, ambient background photons and dark counts are rejected, being mostly randomly distributed over time compared to the laser pulse photons. Therefore, there is no need for repetitive laser shots, neither to acquire and store multiple TOFs, nor to post-process any TOF histogram, since each laser shot can provide the useful distance information. We present a sensor chip based on a pixel with 272 SPADs, which concurrently provide an analog signal to a peak detector triggering a multi-hit TDC each time the number of concurrent photons exceeds the previous peak. We report preliminary tests up to 25 m, rejecting 60 klux solar background, with > 95% single-shot success ratio. copy 1995-2012 IEEE.