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.

When the emitted laser beam power is sufficient, the measuring range can reach about 40 kilometers or even more, and the laser rangefinder can work day and night, but when there is a material with high laser absorption rate in space, its ranging distance and accuracy will decline. The laser rangefinder can also be used to track and range the satellite, measure the flight height of the aircraft, aim and range the target, and conduct topographic mapping and survey.