The handheld high-precision telescopic laser rangefinder's operating principle and features
Laser range finders generally use two methods to measure distance: pulse method and phase method. The process of pulse method ranging is as follows: the range finder emits; the laser is reflected by the measured object and then received by the range finder, and the range finder records the time of the laser back and forth at the same time. Half of the product of the speed of light and the round-trip time is the distance between the rangefinder and the measured object. The accuracy of distance measurement by pulse method is generally around +/-1 meter. In addition, the measurement blind zone of this type of rangefinder is generally about 5-15 meters.
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The instrument works with semiconductor lasers with wavelengths of 905 nm and 1540 nm. For 905nm and 1540nm laser rangefinders, we call them "safe". YAG laser operating at a wavelength of 1064 nm. The wavelength of 1064 nanometers is harmful to human skin and eyes, especially if the eyes accidentally touch the laser with 1064 nanometers wavelength, the damage to the eyes may be fatal. Therefore, in foreign countries, the 1064 nanometer laser is completely banned in the handheld laser rangefinder. In China, some manufacturers also produce 1064nm laser range finders. As for the 1064nm laser range finder, because it is potentially harmful to the human body, we call it "unsafe".
Structure and Composition of Infrared Photoelectric Range Finder
The infrared rangefinder is mainly composed of a modulated light emitting unit, a receiving unit, a phase measuring unit, a counting and displaying unit, a logic control unit and a power converter. The light source is usually gallium arsenide (GaAs) semiconductor light emitting diode. When a considerable current passes through the P-N junction of the GaAs diode, the P-N junction will emit near-infrared light with a wavelength of 0.72 μm and 0.94 μm, which is due to the electron-hole recombination in the doped GaAs semiconductor. , the excess energy is released in the form of photons. Moreover, the emitted light intensity will vary with the injection current. Therefore, if it is used as the light source of the rangefinder, the amplitude modulation of the emitted light intensity can be directly performed by changing the magnitude of the feed current, that is, this semiconductor light-emitting device has the dual functions of "radiation" and "modulation".
The infrared photodetection conversion device used to receive modulated light is usually a silicon photodiode or an avalanche photodiode, and these devices have a "photovoltage effect". When external light is irradiated on its P-N junction, due to the effect of photoelectric energy conversion, a potential difference can be generated at the two poles of P-N, and its magnitude will change with the intensity of incident light, thus playing the role of "demodulation".
