Depth sensing apparatus, comprising: a radiation source, comprising a first array of emitters arranged in multiple banks (52, 62), which are configured to emit a first plurality of pulsed beams of optical radiation toward a target scene; a second plurality of sensing elements, which are arranged in a second array and are configured to output signals indicative of respective times of incidence of photons on the sensing elements, wherein the second plurality exceeds the first plurality; objective optics configured to form an image of the target scene on the array of sensing elements, whereby the beams of optical radiation reflected from the target scene form spots on the second array; and processing and control circuitry (26, 28, 35), which is coupled to actuate the multiple banks in alternation to emit the pulsed beams and is coupled to receive the signals from the sensing elements, and which is configured to calibrate locations of the spots on the second array by searching over the sensing elements, in pre-computed regions based on knowledge of the depth sensing apparatus or by identifying in an initialization stage, a small subset of the locations of laser spots, and in a subsequent iterative stage, predicting by a model and verifying the positions of further laser spots, in order to identify, responsively to the signals, areas of the second array on which the pulses of optical radiation reflected from corresponding regions of the target scene are incident, and to process the signals from the sensing elements in the identified areas in order measure depth coordinates of the corresponding regions of the target scene based on the times of incidence. a radiation source, comprising a first array of emitters arranged in multiple banks (52, 62), which are configured to emit a first plurality of pulsed beams of optical radiation toward a target scene; a second plurality of sensing elements, which are arranged in a second array and are configured to output signals indicative of respective times of incidence of photons on the sensing elements, wherein the second plurality exceeds the first plurality; objective optics configured to form an image of the target scene on the array of sensing elements, whereby the beams of optical radiation reflected from the target scene form spots on the second array; and processing and control circuitry (26, 28, 35), which is coupled to actuate the multiple banks in alternation to emit the pulsed beams and is coupled to receive the signals from the sensing elements, and which is configured to calibrate locations of the spots on the second array by searching over the sensing elements, in pre-computed regions based on knowledge of the depth sensing apparatus or by identifying in an initialization stage, a small subset of the locations of laser spots, and in a subsequent iterative stage, predicting by a model and verifying the positions of further laser spots, in order to identify, responsively to the signals, areas of the second array on which the pulses of optical radiation reflected from corresponding regions of the target scene are incident, and to process the signals from the sensing elements in the identified areas in order measure depth coordinates of the corresponding regions of the target scene based on the times of incidence.