When the laser sensor is working, the laser emitting diode is aimed at the target to emit laser pulses. After being reflected by the target, the laser light is 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 onto the avalanche photodiode. The avalanche photodiode is an optical sensor with an internal amplification function, so it can detect extremely weak light signals and convert them into corresponding electrical signals. The most common is the laser ranging sensor, which can determine the distance to the target by recording and processing the time elapsed from when the light pulse is sent out to when it is received back. Laser sensors must determine the transit time extremely precisely because the speed of light is so fast.

For example, the speed of light is about 3*10^8m/s. To achieve a resolution of 1mm, the electronic circuit of the transit time ranging sensor must be able to distinguish the following extremely short times: 0.001m/(3*10^8m/ s)=3ps

To distinguish the time of 3ps, this is a high requirement for electronic technology, and the cost is too high to realize. But today's laser ranging sensors cleverly circumvent this obstacle, using a simple statistical principle, the law of averaging, to achieve a resolution of 1mm and a guaranteed response speed.