Types of Laser Ranging Sensors
Laser ranging sensors are divided into two categories: triangulation and time-of-flight methods. Time-of-flight laser ranging can be divided into three types: pulsed laser ranging, phase-based laser ranging and interferometric laser ranging.
1. Pulse laser ranging
Pulsed laser ranging sensor technology takes advantage of the relatively concentrated energy of laser pulses in time, and the instantaneous power is very large (usually up to watts). In the case of cooperative targets, pulsed laser ranging can achieve edge measurement, and general-purpose pulsed laser ranging sensors can measure distances of tens or even tens of thousands of kilometers, achieving a measurement accuracy of more than 10 cm. When performing a short-range range from a few kilometers to several tens of kilometers, even if the cooperative target is not used, the distance measurement can be performed only by using the measurement target to diffusely reflect the signal to the pulse tube. The disadvantage is that the absolute ranging accuracy is not very high.
2. Phase laser ranging
The phase laser ranging sensor uses a fixed frequency high frequency sinusoidal signal to continuously modulate the luminous intensity of the laser source, and measures the phase delay generated by the modulated laser back and forth once. The measured distance is calculated from the phase delay.
Phase-based ranging is to indirectly measure the signal propagation time by measuring the phase delay generated by the continuous amplitude modulated signal propagating back and forth over the distance to be measured, thereby obtaining the measured distance. This method has high measurement accuracy, usually on the order of millimeters.
3. Interferometric laser ranging
The interferometric ranging method is also a phase ranging method. The difference from the general phase ranging method is that it does not measure the distance by measuring the phase of the laser modulation signal, but measures the distance by measuring the interference fringe changes. The laser itself.
What Is The Safety Of Laser Distance Meter
As the name suggests, laser distance meters use laser as the main working substance. At present, the working materials of handheld laser distance meters on the market mainly include: semiconductor lasers with working wavelengths of 905 nanometers and 1540 nanometers, and YAG lasers with working wavelengths of 1064 nanometers. The 1064 nm wavelength is harmful to human skin and eyes, especially if the eyes accidentally come into contact with the 1064 nm wavelength laser, the possible damage to the eyes will be great. Therefore, in foreign countries, 1064 nanometer lasers have been completely banned from being used in handheld laser distance meters. In China, some manufacturers also produce 1064nm laser distance meters.
For the 905 nm and 1540 nm laser distance meters, we call them "safe". For the 1064nm laser distance meter, we call it "unsafe" because it is potentially harmful to the human body. The laser ranging sensor uses a monochromatic light source, and the laser with very concentrated energy is incident on the pulsed laser beam. Therefore, when using it, do not look directly at the launch port or use a telescope to observe the smooth reflecting surface, so as not to hurt people's eyes. Therefore, the operator must perform the measurement in accordance with the safety specifications in the manual. During the on-site measurement, do not point the transmitter port of the instrument to the sun, so as not to burn the photosensitive element of the instrument.