High-speed vision with a 3D-stacked SPAD image sensor

3D sensing devices are becoming increasingly prevalent in robotics, self-driving cars, human-computer interfaces, as well as consumer electronics. Recent years have seen single-photon avalanche diodes (SPADs) emerging as one of the key technologies underlying 3D time-of-flight sensors, with the capability to capture accurate 3D depth maps in a range of environmental conditions, and with low computational overhead. In particular, direct ToF SPADs (dToF), which measure the return time of back-scattered laser pulses, form the backbone of many automotive LIDAR systems. We here consider an advanced direct ToF SPAD imager with a 3D-stacked structure, integrating significant photon processing. The device generates photon timing histograms in-pixel, resulting in a maximum throughput of 100's of giga photons per second. This advance enables 3D frames to be captured at rates in excess of 1000 frames per second, even under high ambient light levels. By exploiting the re-configurable nature of the sensor, higher resolution intensity (photon counting) data may be obtained in alternate frames, and depth upscaled accordingly. We present a compact SPAD camera based on the sensor, enabling high-speed object detection and classification in both indoor and outdoor environments. The results suggest a significant potential in applications requiring fast situational awareness.