Classification of photoelectric rangefinders
Photoelectric range finders are roughly divided into three categories according to the range of the instrument:
(1) Short-range photoelectric rangefinder: the range is within 3km, and the ranging accuracy is generally around 1cm. This instrument can be used to measure the starting side of the triangular lock net below the third class, as well as the side length of the corresponding level of precision wire and triangular net, and is suitable for engineering survey and mine survey. There are many instruments for this type of range measurement, such as ME3000 in Switzerland, the accuracy can reach ± (0.2mm+0.5×10-6D); DM502, DI3S, DI4, AGA-112, AGA-116 in Sweden, Hp3820A in the United States, and CD6, Japan's RED2, SDM3E, the original West Germany's ELTA2, ELDI2, etc., the accuracy can reach ± (5mm+5×10-6D); the original East Germany's EOT2000, my country's HGC-1, DCH-2, DCH3, DCH-05 etc.
Gallium arsenide (GaAs or GaAlAs) light-emitting diodes are mostly used as short-range photoelectric range finders. Gallium arsenide light-emitting diode is a device that can directly emit modulated light, that is, the emitted light intensity can be changed by changing the current density of the gallium arsenide light-emitting diode.
(2) Medium-range photoelectric rangefinder: The instrument with a measuring range of about 3-15km is called a medium-range photoelectric rangefinder. This type of instrument is suitable for side length measurement of secondary, tertiary, and quaternary control networks. For example, my country's JCY-2 and DCS-1 have an accuracy of ± (lOmm+1×10-6D), Switzerland's ME5000 has an accuracy of ×(0.2mm+0.2×10-6D), DI5, DI20, and Sweden's AGA -6, AGA-14A and other precision can reach ± (5mm+5ppm).
(3) Long-range laser range finder: a photoelectric range finder with a measuring range of more than 15km, the accuracy can generally reach ± (5mm+1×10-6D), and can meet the side length measurement of the national first-class and second-class control networks. Such as AGA-8 and AGA-600 in Sweden, Rangemaster in the United States, and JCY-3 successfully developed in my country.
Medium and long-distance photoelectric rangefinders mostly use helium-neon (He-Ne) gas lasers as light sources, some use gallium arsenide laser diodes as light sources, and other light sources, such as carbon dioxide (CO2) lasers, etc. Because the laser emitted by the laser has the characteristics of strong directionality, high brightness, good monochromaticity, etc., and the instantaneous power emitted by it is large, so the laser is often used as the carrier in the medium and long-distance range finder, which is called a laser range finder.
