Analysis of Diffuse Reflection in Laser Rangefinder
Usually, in order to reduce errors, those laser rangefinders will have a reflective surface on the measured end to reduce the error caused by diffuse reflection. So, how did the telescope style laser rangefinders used by snipers overcome this problem? The working principle of a laser rangefinder is similar to that of sonar, but is the signal of the reflected light easily disturbed by other wavelengths and intensities of light in the environment?
The detection device of laser rangefinder (pulse type) generally uses avalanche photodiodes, which are only sensitive to specific wavelengths of light. If the wavelength matches, even very small light intensities can be detected by it. If the wavelength does not match, even if the light intensity is large, it cannot be detected. Laser has the characteristic of good monochromaticity, with a commonly used wavelength of 905nm. So the signal of receiving reflected light is not easily disturbed by other wavelengths and intensities of light in the environment.
Additionally:
There are two commonly used laser ranging methods: pulse method and phase method.
The phase method measures distance by measuring the phase deviation of the returned wave, which needs to be coordinated with the target, which is the reflection surface on the side of the measured end. In this case, the transmission power of the rangefinder is relatively small.
The telescope type laser rangefinder used by snipers generally uses the pulse method, which emits a pulse to start timing and stops timing after receiving the reflected pulse, achieving the purpose of ranging. In this case, when there is no cooperative target, relying on diffuse reflection light wave energy loss can be very serious, but it generally does not affect the measurement. The reason is as mentioned earlier. Generally, the transmission power of the rangefinder is increased to provide some compensation.
