A Few Good Photons: Active imaging with a little signal and a lot more noise

LIDAR systems use single-photon avalanche diodes to detect very weak signals; in a striking example, a system was recently demonstrated from a distance of 10.5 km using average optical power of only 10 mW. Systems of this sort inspire efficient use of each detected photon and tolerance to significant ambient light. This talk will describe photon-efficient depth and reflectivity imaging techniques that are effective with only 0.5 to 2.0 detected photons per pixel due to the backreflected active illumination. Our initial methods could withstand as much background as signal. With a novel emphasis on unmixing of signal and background contributions, a recent variation performs well with 25 times as much background. Several related works will be covered briefly, including a variation that enables detection of multiple depths per pixel from a moderately stronger signal and methods for transverse super-resolution.