Picosecond time-resolved imaging using SPAD cameras

The recent development of 2D arrays of single-photon avalanche diodes (SPAD) has driven the development of applications based on the ability to capture light in motion. Such arrays are composed typically of 32x32 SPAD detectors, each having the ability to detect single photons and measure their time of arrival with a resolution of about 100 ps. Thanks to the single-photon sensitivity and the high temporal resolution of these detectors, it is now possible to image light as it is travelling on a centimetre scale. This opens the door for the direct observation and study of dynamics evolving over picoseconds and nanoseconds timescales such as laser propagation in air, laser-induced plasma and laser propagation in optical fibres. Another interesting application enabled by the ability to image light in motion is the detection of objects hidden from view, based on the recording of scattered waves originating from objects hidden by an obstacle. Similarly to LIDAR systems, the temporal information acquired at every pixel of a SPAD array, combined with the spatial information it provides, allows to pinpoint the position of an object located outside the line-of-sight of the detector. A non-line-of-sight tracking can be a valuable asset in many scenarios, including for search and rescue mission and safer autonomous driving.