Passive Inter-Photon Imaging

Atul Ingle, Trevor Seets, Mauro Buttafava, Shantanu Gupta, Alberto Tosi, Mohit Gupta, Andreas Velten

Abstract:

Digital camera pixels measure image intensities by converting incident light energy into an analog electrical current, and then digitizing it into a fixed-width binary representation. This direct measurement method, while conceptually simple, suffers from limited dynamic range and poor
performance under extreme illumination — electronic noise
dominates under low illumination, and pixel full-well capacity results in saturation under bright illumination. We
propose a novel intensity cue based on measuring interphoton timing, defined as the time delay between detection of successive photons. Based on the statistics of interphoton times measured by a time-resolved single-photon
sensor, we develop theory and algorithms for a scene
brightness estimator which works over extreme dynamic
range; we experimentally demonstrate imaging scenes with
a dynamic range of over ten million to one. The proposed
techniques, aided by the emergence of single-photon sensors such as single-photon avalanche diodes (SPADs) with
picosecond timing resolution, will have implications for a
wide range of imaging applications: robotics, consumer
photography, astronomy, microscopy and biomedical imaging.