What are the technical principles of laser rangefinders?
The principle of pulse laser ranging technology:
The phase method is similar to the method used for ultrasonic velocity measurement and distance measurement. The large measurement distance is usually several hundred meters, which can easily reach the order of millimeters. However, the large measurement distance of the distance measuring instrument designed according to this method is limited and cannot be extended. This method is mainly widely used abroad. Pulse laser ranging generally uses infrared laser, including near-infrared laser and mid infrared laser. There are visible and invisible lasers in this band. And the rangefinder based on this technology has low requirements for coherence, fast speed, simple implementation structure, high peak output power, high repetition frequency, and large range. Therefore, this project uses the pulse method to design a handheld laser rangefinder.
The principle of phase based laser ranging technology:
The mainstream laser rangefinder in the market is based on phase method. This is because laser rangefinders based on phase method can easily overcome a major drawback of ultrasonic rangefinders: excessive error, resulting in measurement accuracy reaching the millimeter level. The main drawbacks of laser rangefinders based on this method are complex circuits and short operating distances (around 100 meters, after the efforts of many scientific workers, there are now phase based laser rangefinders with operating distances of several hundred meters).
The phase method laser ranging technology uses a laser with a radio frequency band to modulate the amplitude and measure the phase difference generated by the distance between the sine modulated light and the target object. Based on the wavelength and frequency of the modulated light, the laser flight time is calculated, and then the measured distance is calculated in sequence. This method generally requires placing a reflector at the object to be measured, reflecting the laser path back to the laser rangefinder, and receiving and processing it by the discriminator of the receiving module. That is to say, this method is a passive laser ranging technology with cooperative target requirements.
