At present, there are many types of laser rangefinders with different functions, but from the perspective of operation mode (or operation principle), there are two types of pulsed laser ranging and continuous wave laser ranging. The following is a description of the principle features of the two rangefinders:

(1) Pulse laser ranging.

The principle of pulsed laser ranging is to use a pulsed laser to transmit a narrow series of light pulses (pulse width less than 50ns) to the policy, and the light is partially reflected after reaching the surface of the policy. After measuring the time of the light pulse from launch to receiver, the interval between the rangefinder and the policy can be calculated. Assuming that the measurement interval is h, the reciprocating time of the optical 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. Strong ranging capability, even with non-cooperative policies, the maximum ranging can reach more than 30,000 meters. 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 climatic measurement of visibility and cloud height, as well as fine interval measurement of artificial satellites.

(2) Continuous wave laser ranging.

The connected wave laser rangefinder usually adopts the phase method to measure the distance. The principle is to first launch a modulated connecting wave laser beam to the policy, and the beam will reflect after reaching the policy surface. Measuring the phase difference between the transmitted modulated laser beam and the echo received by the receiver gives the separation between the policy and the rangefinder.