What Is The Principle Of The Short-range Laser Ranging Sensor?

Laser distance measurement commonly uses pulses and then measures the time difference between the reflected light and the emitted pulse. In fact, there is another method of laser ranging, that is, the phase method. The phase method cannot measure targets that are too far away, but the accuracy is much higher than the pulse.

The phase method is to modulate one or more low frequencies (relative to the frequency of light) on the laser, similar to the modulation of audio signals on radio frequency signals by radio stations. The specific method is: use low-frequency signal to control the laser output power, then the received laser reflected signal power will also change with the low-frequency signal, compare the phase of the received signal with the phase of the output signal, you can calculate the distance of the reflective surface

In order to have both range and accuracy, the usual phase method range finder will use several frequency signals to modulate at the same time, that is, use multiple measuring rulers at the same time.

It should be noted that because the laser used in the phase method distance measurement is continuously output, the peak power is small, so the maximum measurement distance is much smaller than the pulse method,

In the case of very close distances (such as within one or two meters), there is a more precise method of distance measurement: triangulation. Separate the photosensitive optical path from the laser beam by a certain distance, so that the connection between the measured point and the photosensitive unit, the reflected optical path, will form an angle with the laser beam. This angle is measured, so based on the knowledge of triangles, we can calculate the distance from the measured point to the photosensitive unit (the distance between the photosensitive unit and the emitted beam is a known parameter). The accuracy of laser triangulation distance measurement can reach the micron level, and the commonly used coordinate measuring machine uses this principle to measure.

Application of laser ranging sensor: