This is how pulsed and continuous wave laser rangefinders work.
There are currently many types of laser rangefinders with different functions, but from the perspective of operation methods (or operating principles), there are no more than two types of pulse laser rangefinders and continuous wave laser rangefinders. The following is a description of the principles and characteristics of the two rangefinders:
(1) Pulse laser ranging.
The principle of pulse laser ranging is to use a pulse laser to emit a series of very narrow light pulses (pulse width less than 50ns) to the target, and the light is partially reflected after reaching the surface of the target. By measuring the time it takes for a light pulse to travel from launch to receiver, the separation between the rangefinder and the target can be calculated. Assume that the measurement interval is h, the light pulse round-trip time is t, and the propagation speed of light in the air is c, then:
h=ct/2
Pulse laser rangefinders can emit intense laser light. Ranging can be very strong. Even with a non-cooperative policy, the maximum measurement range can reach more than 30,000 meters. Its ranging accuracy is generally 5 meters and can reach up to 0.15 meters. Pulse laser rangefinders can be used not only for ranging in various non-cooperative military policies, but also for visibility and cloud height measurements on climate, as well as fine interval measurements on artificial satellites.
(2) Continuous wave laser ranging.
Continuous wave laser rangefinders generally use the phase method for distance measurement. The principle is to first emit a modulated continuous wave laser beam to the target. After the beam reaches the surface of the target, it is reflected. After measurement, the emitted continuous wave laser beam is received by the receiver. The phase difference between the echoes determines the distance between the target and the rangefinder.
