Apollo and early ranging
In 1969, astronauts placed a retroreflector array on the Moon. Earth-based telescopes fire laser pulses at it; the 2.5-second round trip measures the Earth-Moon distance to millimetre precision. This was the first operational LIDAR system, and it proved the concept: short pulses, precise timing, clean returns.
Self-driving and solid-state
Modern automotive LIDAR uses 905 nm or 1550 nm lasers, spinning mirrors or MEMS micro-mirrors to sweep a field of view. 1550 nm is eye-safe at higher power, giving 200+ m range. Solid-state designs (flash LIDAR, OPA) remove moving parts. Every autonomous vehicle stack — Waymo, Tesla (visual-only but disputed), Mobileye — depends on LIDAR for 3D world mapping.
LIDAR limitations
Lasers don't penetrate fog, rain or dust — the wavelength is too close to particle size. They can be blinded by other lasers or the sun. And they scan point-by-point, so frame rate trades against resolution. Radar sees through weather and works at any light level. The two sensors are complementary, not competing.
LADAR: the radar-like variant
When LIDAR is coherent — measuring phase and Doppler like radar — engineers sometimes call it LADAR (Laser Detection and Ranging) or coherent LIDAR. This is common in military targeting and wind sensing. The terminology is fluid, but the physics is clear: coherent light detection is as powerful as coherent radio detection, just at optical wavelengths.