Usually, in order to reduce errors, the laser rangefinder will put a reflective surface on the measured end to reduce the errors caused by diffuse reflection. How does the telescope-type laser rangefinder used by snipers overcome this problem? The working principle and Sonar is about the same, but can the signal receiving the reflected light be easily disturbed by other wavelengths and intensities of light in the environment?

The detection device of the laser rangefinder (pulse type) generally uses an avalanche photodiode, which is only sensitive to light of a specific wavelength. If the wavelength matches, a very small light intensity can be detected by it. If the wavelength does not match, even if the light intensity is very large , also cannot be detected. The laser has the characteristics of good monochromaticity, and the commonly used wavelength is 905nm. So the signal receiving the reflected light is not simply disturbed by other wavelengths and intensities of light in the environment.

There are two commonly used laser ranging schemes: pulse method and phase method.

The phase method measures the distance by measuring the phase deviation of the returned wave. This requires a cooperative target, that is, the so-called measured end is placed on a reflective surface. In this case, the transmit power of the rangefinder is small.

The telescope-type laser rangefinders used by snipers generally use the pulse method, that is, announcing a pulse, starting the timing, and stopping the timing after receiving the reflected pulse to achieve the purpose of ranging. In this case, when there is no cooperative target, the loss of light wave energy by diffuse reflection is very serious, but generally does not affect the measurement. The reason is as mentioned above. Generally, the transmitting power of the rangefinder will be increased to make certain compensation.