This article in Laser Focus World describes the progress that Sigma Space Corporation (Lanham, MD) is making with the ongoing development of a single-photon-sensitive airborne LiDAR. The advantages of this approach are to allow large areas to be mapped quickly while still permitting the user to tailor the measurement point density.
By passing a low-power, high-repetition-rate 532 nm green laser beam (140 mW at 20 kHz) through a diffractive optical element (DOE) the are able to generate a 10 × 10 array of low-power (1 mW) beamlets and allowed surface measurement rates up to 2 megapixels per second (Mp/s).
It seems like a promising approach.
