"Low-intensity pulses of visible laser light scan an object of interest. The laser fires a pulse at a given location until a single reflected photon is recorded by a detector; each illuminated location corresponds to a pixel in the final image. Variations in the time it takes for photons from the laser pulses to be reflected back from the object provides depth information about the body — a standard way of revealing three-dimensional structure. However, the algorithm developed by Kirmani and his colleagues provides that information using one-hundredth the number of photons required by existing light detection and ranging techniques."
From the abstract:
"Imagers that use their own illumination can capture three-dimensional (3D) structure and reflectivity information. With photon-counting detectors, images can be acquired at extremely low photon fluxes. To suppress the Poisson noise inherent in low-flux operation, such imagers typically require hundreds of detected photons per pixel for accurate range and reflectivity determination. We introduce a low-flux imaging technique, called first-photon imaging, which is a computational imager that exploits spatial correlations found in real-world scenes and the physics of low-flux measurements. Our technique recovers 3D structure and reflectivity from the first detected photon at each pixel. We demonstrate simultaneous acquisition of sub-pulse duration range and 4-bit reflectivity information in the presence of high background noise. First-photon imaging may be of considerable value to both microscopy and remote sensing."