High-speed object detection with a single-photon time-of-flight image sensor

German Mora-Martín, Alex Turpin, Alice Ruget, Abderrahim Halimi, Robert Henderson, Jonathan Leach, Istvan Gyongy

Research output: Contribution to journalArticlepeer-review

Abstract

3D time-of-flight (ToF) imaging is used in a variety of applications such as augmented reality (AR), computer interfaces, robotics and autonomous systems. Single-photon avalanche diodes (SPADs) are one of the enabling technologies providing accurate depth data even over long ranges. By developing SPADs in array format with integrated processing combined with pulsed, flood-type illumination, high-speed 3D capture is possible. However, array sizes tend to be relatively small, limiting the lateral resolution of the resulting depth maps and, consequently, the information that can be extracted from the image for applications such as object detection. In this paper, we demonstrate that these limitations can be overcome through the use of convolutional neural networks (CNNs) for high-performance object detection. We present outdoor results from a portable SPAD camera system that outputs 16-bin photon timing histograms with 64×32 spatial resolution, with each histogram containing thousands of photons. The results, obtained with exposure times down to 2 ms (equivalent to 500 FPS) and in signal-to-background (SBR) ratios as low as 0.05, point to the advantages of providing the CNN with full histogram data rather than point clouds alone. Alternatively, a combination of point cloud and active intensity data may be used as input, for a similar level of performance. In either case, the GPU-accelerated processing time is less than 1 ms per frame, leading to an overall latency (image acquisition plus processing) in the millisecond range, making the results relevant for safety-critical computer vision applications which would benefit from faster than human reaction times.
Original languageEnglish
Pages (from-to)33184-33196
Number of pages13
JournalOptics Express
Volume29
Issue number21
Early online date29 Sep 2021
DOIs
Publication statusPublished - 11 Oct 2021

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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