At present, there are many types of laser rangefinders with different functions, but from the perspective of operation mode (or operating principle), there are only two types of pulsed laser rangefinders and continuous wave laser rangefinders. The following is a description of the principle characteristics of the two rangefinders:
(1) Pulse laser ranging. The principle of pulsed laser ranging is to use a pulsed laser to launch a very narrow light pulse (pulse width less than 50ns) towards the target, and the light is partially reflected after reaching the target surface. After measuring the time of the light pulse from launch to receiver, the interval between the rangefinder and the target can be calculated. Assuming that the measurement interval is h, the reciprocating time of the light pulse is t, and the propagation speed of light in the air is c, then:
h=ct/2
Pulsed laser rangefinders can emit intense laser light. Ranging can be strong. Even with a non-cooperative policy, the maximum range can reach more than 30,000 meters. Its ranging accuracy is generally 5 meters, up to 0.15 meters. Pulsed laser rangefinders can be used not only for distance measurement of various non-cooperative policies in the military, but also for the measurement of visibility and cloud height in climate, and for fine interval measurement of artificial satellites.
(2) Continuous wave laser ranging.
The continuous wave laser rangefinder generally uses the phase method for distance measurement. The principle is to first emit a modulated continuous wave laser beam to the target, and the beam reaches the target surface and then reflects, and the continuous wave laser beam emitted by the measurement is received by the receiver. The phase difference between the echoes gives the distance between the target and the rangefinder.
