Multi-mode sensor for object identification

Optical sensing apparatus, comprising:

• a transmitter, which is configured to transmit outgoing frequency-modulated (FM) coherent optical radiation toward a target scene;
• a receiver, comprising:
• an array of detectors, which are configured to output electrical signals in response to photons that are incident on the detectors, wherein the detectors are single-photon detectors, which are configured to output electrical pulses in response to the incident photons;
• and
• optics configured to image the target scene onto the array while diverting a part of the outgoing FM coherent optical radiation to form a local beam, which mixes with incoming optical radiation from the target scene;
• and
• processing circuitry configured to process the electrical signals output by the detectors to produce a two-dimensional (2D) image of the target scene, to identify an object of interest in the 2D image, which is imaged onto an area within the array, to extract beat frequencies in response to the mixed optical radiation from the electrical signals output by the detectors in the area, and to measure a three-dimensional feature of the object of interest responsively to the beat frequencies,
• wherein the processing circuitry is configured to compute counts of the electrical pulses output as a function of time by the single-photon detectors, wherein the counts of the electrical pulses as the function of time define temporal waveforms, and wherein the processing circuitry is configured to extract the beat frequencies by processing the temporal waveforms.