  Traditional paradigms for imaging rely on the use of a spatial structure,
either in the detector (pixels arrays) or in the illumination (patterned
light). Removal of the spatial structure in the detector or illumination, i.e.,
imaging with just a single-point sensor, would require solving a very strongly
ill-posed inverse retrieval problem that to date has not been solved. Here, we
demonstrate a data-driven approach in which full 3D information is obtained
with just a single-point, single-photon avalanche diode that records the
arrival time of photons reflected from a scene that is illuminated with short
pulses of light. Imaging with single-point time-of-flight (temporal) data opens
new routes in terms of speed, size, and functionality. As an example, we show
how the training based on an optical time-of-flight camera enables a compact
radio-frequency impulse radio detection and ranging transceiver to provide 3D
images.
