Professional Knowledge

laser distance measurng


laser distance measurng uses a laser as a light source for ranging. According to the way the laser works, it is divided into continuous optical devices and pulse lasers. Ammonia, gas ions, atmosphere temperature and other gas detectors work in a continuous forward state, used for phase laser ranging, dual heterogeneous semiconductor lasers, used for infrared ranging, ruby, gold glass and solid-state lasers , used for pulsed laser ranging. Due to the characteristics of good monochromaticity and strong directivity of laser, coupled with the integration of electronic circuits into semiconductors, laser rangefinders can not only operate day and night, but also improve the distance measurement accuracy and significantly improve the distance measurement accuracy compared with photoelectric rangefinders. By reducing weight and power consumption, it becomes a reality to measure the distance to distant targets such as artificial earth satellites and the moon.

A laser rangefinder is an instrument that uses laser light to accurately measure the distance to a target (also called laser ranging). When the laser rangefinder is working, it emits a very thin laser beam towards the target. The photoelectric element receives the laser beam reflected by the target. The timer measures the time from emission to reception of 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 40 kilometers, 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 when used for long-distance animal measurements. The world's first laser was successfully developed in 1960 by Maiman, a scientist from the American Hughes Aircraft Company. The U.S. military quickly launched research on military laser devices on this basis. In 1961, the first military laser rangefinder passed the demonstration test of the US military. After that, the laser rangefinder quickly entered the practical community. The laser rangefinder is light in weight, small in size, simple to operate, fast and accurate in reading, and its error is only one-fifth to one percent of that of other optical rangefinders. Therefore, it is widely used in terrain surveying and battlefield surveying. , ranging from tanks, aircraft, ships and artillery to targets, measuring the height of clouds, aircraft, missiles and artificial satellites, etc. It is an important technical equipment to improve the accuracy of tanks, aircraft, ships and artillery. As the price of laser rangefinders continues to drop, the industry has gradually begun to use laser rangefinders. A number of new miniature rangefinders have emerged at home and abroad with the advantages of fast ranging, small size, and reliable performance, and can be widely used. In industrial measurement and control, mining, ports and other fields.

Laser rangefinders generally use two methods to measure distance: pulse method and phase method. The process of pulse method ranging is as follows: the laser emitted by the rangefinder is reflected by the object being measured and then received by the rangefinder. The rangefinder records the round trip time of the laser. Half of the product of light evolution and round-trip time is the distance between the rangefinder and the object being measured. The accuracy of distance measurement by pulse method is generally about +- 1 meter. In addition, the measurement blind zone of this type of rangefinder is generally about 15 meters. Laser ranging is a distance measurement method in light wave ranging. If light travels in the air at a speed C and the time required to travel back and forth between two points A and B is known, then the distance D between two points A and B can be used as follows express.


In the formula:

D: The distance between measuring points A and B:

c: speed;

t: The time it takes for light to travel back and forth between A and B.

It can be seen from the above formula that to measure the distance between A and B is actually to measure the time of light propagation. According to the different time measurement methods, laser rangefinders can usually be divided into two measurement forms: pulse type and phase type. It should be noted that phase measurement does not measure the phase of infrared or laser, but the phase of the signal modulated on infrared or laser. There is a handheld laser rangefinder used in the construction industry for house surveying that works on the same principle.