Spatial Phase-Sweep: Increasing temporal resolution of transient imaging using a light source array

Transient imaging techniques capture the propagation of an ultra-short pulse of light through a scene, which in effect captures the optical impulse response of the scene. Recently, it has been shown that we can capture transient images using commercial, correlation imager based Time-of-Flight (ToF) systems. But the temporal resolution of these transient images are currently limited by high-speed electronics. In this paper, we propose `Spatial Phase-Sweep' (SPS), a technique that exploits the speed of light to increase the temporal resolution of transient imaging beyond the limit imposed by electronic circuits in these commercial ToF sensors. SPS uses a linear array of light sources with a controlled spatial separation between these sources. The differential positioning of these sources introduce sub nano-second time shifts in the light wavefront, improving the time resolution of captured transients. As a proof of concept, we demonstrate a prototype which improves the temporal resolution of transient imaging by a factor of 10x, without any modification to the underlying electronics.