Hybrid depth imaging with sparse subject irradiation

A depth-imaging system comprising:

• an emitter configured to emit a modulated radiant output;
• a redistribution optic arranged optically downstream of the emitter and configured to sparsely project the radiant output onto a subject;
• an imaging sensor array configured to acquire a plurality of raw shutters of the subject;
• a computer configured to:
• modulate the radiant output of the emitter and a charge-carrier collection at the imaging sensor at one or more modulation frequencies,
• construct a phase map of the subject based on the plurality of raw shutters,
• pinpoint in the phase map a plurality of bright areas corresponding each to a sparse-projection feature of the radiant output reflecting from the subject;
• and
• for each of the plurality of bright areas:
• triangulate an estimate of depth to the corresponding sparse-projection feature reflecting from the subject, wherein the estimate is based on a displacement of the bright area from a calibration position along a trajectory, compute an aggregate phasor, and phase unwrap the aggregate phasor based partly on the estimate, to reveal a depth value.

A method enacted in a depth-imaging system, the method comprising:

• modulating radiant output from an emitter at one or more modulation frequencies;
• projecting the radiant output as a plurality of sparse-projection features;
• acquiring a plurality of raw shutters on an imaging sensor array modulated at the one or more modulation frequencies;
• triangulating a geometric estimate of depth to a subject locus reflecting a sparse-projection feature, wherein the geometric estimate of depth is based on a displacement of a bright area in a phase map derived from the plurality of raw shutters from a calibration position along a trajectory, the bright area corresponding to the sparse-projection feature reflected from the subject locus;
• and
• returning a time-of-flight value of the depth based on a phase computed from the plurality of raw shutters and on the geometric estimate of the depth.