Depth sensor calibration using internal reflections

Abstract

Depth sensing apparatus includes a radiation source, which emits a first array of beams of light pulses through a window toward a target scene. Objective optics image the target scene onto a second array of sensing elements, which output signals indicative of respective times of incidence of photons. A first calibration, which associates the beams in the first array with respective first locations on the second array onto which the beams reflected from the target scene are imaged, is used in processing the signals in order to measure respective times of flight of the light pulses. A second calibration indicates second locations on which stray radiation is incident on the second array due to reflection of the beams from the window. Upon detecting a change in the second locations relative to the second calibration, the first calibration is corrected so as to compensate for the detected change.