LIDAR & Direct Time of Flight
LIDAR (Light Detection and Ranging) is a sensor technology for remote object detection and ranging, using a light source and receiver. Emitted light pulses hit objects, reflect, and return to the LiDAR sensor system where the receiver detects the returning light pulse.
The time between sending and receiving a light pulse is dependent on the distance between the LiDAR system and the object. Knowing time allows you to calculate distance. The most straightforward implementation of this principle is Direct Time of Flight (D-ToF). The system emits short pulses of Near Infrared light. A portion of that energy is returned and converted in distance and optionally intensity and ultimately speed. By taking many samples, it is possible to filter out noise (detected light not being a reflection of the emitted pulse).