This article discusses a single detector, 1550 nm, lidar that uses a photon counting receiver, referred to as a SPAD (single-photon avalanche diode), or a GmAPD (Geiger-mode avalanche photodetector), detector. 1550 nm is of course an eye safe wavelength region. The lidar uses a fiber laser, and isolates the transmitter from the receiver by timing the emitted pulses when the detector will not receive them. Acousto-optical modulators, AOMs, are used to control this timing. The lidar uses a 2.5 cm effective diameter MEMs aperture to keep the lidar compact.  It has 0.5 ns pulses, at a 1 MHz pulse rate, so it should have excellent range resolution.  The operating temperature is 223 K, with a 30% QE, and a dark count of 1200 per second. They imaged a tower in Shanghai 12.8 km away, imaging with 100×128 pixels in a few minutes, using 9.3 photons per pixel, in an urban environment. Shorter range images are created quicker. They demonstrated 5 frames per second at a range of >1 km.

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