Laser rangefinder is an instrument that uses a parameter of modulated laser to measure the distance of the target. The measuring range of the laser rangefinder is 3.5~5000 meters. According to the ranging method, it can be divided into phase method ranging instrument and pulse method ranging instrument. Pulse type laser ranging instrument is to shoot a beam or a series of short pulse laser beams to the target when working, and the laser beam reflected by the target is received by the photoelectric element. The timer measures the time from the laser beam to the receiving, and calculates the distance from the observer to the target.

The phase method laser rangefinder detects the distance by detecting the phase difference between the emitted light and the reflected light when they propagate in space. The laser rangefinder is light in weight, small in size, simple in operation, fast and accurate, and its error is only one-fifth to one-hundredth of that of other optical rangefinders. In the right figure, there are typical phase method rangefinders and pulse method rangefinders.