When the laser sensor is working, the laser emitting diode first aims at the target and emits laser pulses. The laser light is reflected by the target and scattered in all directions. Part of the scattered light returns to the sensor receiver, where it is picked up by the optical system and imaged on the avalanche photodiode. An avalanche photodiode is an optical sensor with internal amplification, so it can detect extremely weak light signals and convert them into corresponding electrical signals. The most common is a laser ranging sensor, which can determine the distance to a target by recording and processing the time from when a light pulse is emitted to when it is received. Because the speed of light is so fast, laser sensors can accurately measure transit times.

For example, the speed of light is about 3*10^8m/s. In order to achieve a resolution of 1mm, the electronic circuit of the transmission time ranging sensor can distinguish the following extremely short time: 0.001m/(3*10^8m/s)=3ps, it is necessary to distinguish the time of 3ps, that is, the requirements for electronic technology are too high. High, the implementation cost is too high. But today's laser ranging sensor cleverly avoids this obstacle, using a simple statistical principle, that is, the averaging method achieves a resolution of 1mm, and can guarantee the response speed.