Laser rangefinders generally measure distance in two ways: pulse method and phase method.
The process of pulse ranging is that the laser emitted by the rangefinder is reflected by the measured object and then received by the rangefinder. The rangefinder records the round-trip time of the laser at the same time. Half of the product of the speed of light and round-trip time is the distance between the rangefinder and the object being measured. The accuracy of distance measurement by pulse method is generally about+/- 1m. In addition, the measurement blind zone of this type of rangefinder is generally about 15 meters.
The phase laser rangefinder uses the frequency of the radio band to modulate the amplitude of the laser beam and measure the phase delay produced by the modulated light to and from the measuring line once, and then converts the distance represented by the phase delay according to the wavelength of the modulated light. That is to say, the time required for light to travel through the round-trip measuring line is measured by indirect method.