Laser rangefinder is an instrument that uses laser to accurately measure the distance of the target (also known as laser rangefinder). When the laser rangefinder works, it emits a very thin laser beam to the target, and the photoelectric element receives the laser beam reflected by the target. The timer measures the time from transmitting to receiving the laser beam, and calculates the distance from the observer to the target. If the laser is emitted continuously, the measuring range can reach about 40km, and the operation can be carried out day and night. If the laser is pulsed, the absolute accuracy is generally low, but it can achieve good relative accuracy for long-distance measurement. The world‘s first laser was first developed by Mayman, a scientist of Hughes Aircraft Company in 1960. The US military soon carried out research on military laser devices on this basis. In 1961, the first military laser rangefinder passed the demonstration test of the U.S. military. After that, the laser rangefinder soon entered the practical consortium. Laser rangefinder has the advantages of light weight, small volume, simple operation, fast and accurate speed, and its error is only one fifth to one hundredth of that of other optical rangefinders. Therefore, it is widely used in topographic survey, battlefield survey, target ranging of tanks, aircraft, ships and artillery, and measuring the height of clouds, aircraft, missiles and man-made satellites. It is an important technical equipment to improve the accuracy of tanks, aircraft, ships and artillery. As the price of laser rangefinder continues to decline, the industry has gradually begun to use laser rangefinder. A number of new micro rangefinders with the advantages of fast ranging, small volume and reliable performance have emerged at home and abroad, which can be widely used in industrial measurement and control, mines, ports and other fields.
Laser rangefinder generally uses two methods to measure distance: pulse method and phase method. The process of pulse ranging is as follows: the laser emitted by the rangefinder is reflected by the measured object and then received by the rangefinder. The rangefinder records the round-trip time of the laser at the same time. Half 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 about + / - 10cm. In addition, the measurement blind area of this kind of rangefinder is generally about 1m. Laser ranging is a ranging method in light wave ranging. If the light propagates in the air at speed C and the time required for a round trip between points a and B is t, the distance d between points a and B can be expressed as follows. D=ct/2 Where: D -- distance between station a and B; C - speed; T -- time required for one round trip of light a and B. It can be seen from the above formula that to measure the distance a and B is actually to measure the light propagation time T. according to different measurement time methods, the laser rangefinder can usually be divided into pulse type and phase type. Typical are the di-3000 of wild and the ldm30x of real world. It should be noted that phase measurement does not measure the phase of infrared or laser, but the signal phase modulated on infrared or laser. There is a hand-held laser rangefinder in the construction industry, which is used for house measurement, and its working principle is the same.
Generally, precision ranging requires the cooperation of total reflection prism, while the range finder used for house measurement is directly measured by the reflection of smooth wall, mainly because the distance is relatively close and the signal intensity reflected by light is large enough. From this, we can know that it must be vertical, otherwise the return signal is too weak to get the accurate distance. It is usually possible. In practical engineering, thin plastic plate will be used as the reflecting surface to solve the serious problem of diffuse reflection. The precision of laser rangefinder can reach 1mm error, which is suitable for various high-precision measurement purposes.
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