A laser rangefinder is an instrument that uses a laser to accurately measure the distance to a target. The laser rangefinder emits a very thin laser beam to the target when it is working, and the laser beam reflected by the target is received by the photoelectric element.

If the laser is fired 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 for long-distance measurement, a good relative accuracy can be achieved.

The world's first laser was first developed in 1960 by the American Hughes Aircraft Company scientist Maiman. The U.S. 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 US military, after which the laser rangefinder soon entered the practical consortium.

The laser rangefinder is light in weight, small in size, simple in operation, fast and accurate, and its error is only one-fifth to several hundredths of other optical rangefinders, so it is widely used in terrain measurement, battlefield measurement, tanks , ranging from 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 high 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 appeared at home and abroad with the advantages of fast ranging, small size and reliable performance, which can be widely used in industrial measurement and control, mines, ports and other fields.

main classification

1D laser rangefinder

For distance measurement and positioning;

Scanning Laser Range finder

For contour measurement, positioning, area monitoring and other fields;

3D Laser Range finder

It is used for 3D contour measurement, 3D space positioning and other fields.

Figure: Schematic diagram of using a laser to measure the distance from the Moon to the Earth

Measuring principle and method of laser rangefinder

1. What is the principle of using infrared ranging or laser ranging?

The principle of ranging can basically be attributed to measuring the time required for the light to travel to and from the target, and then calculate the distance D through the speed of light c = 299792458m/s and the atmospheric refraction coefficient n. Because it is difficult to measure time directly, it is usually to measure the phase of the continuous wave, which is called a phase-measuring rangefinder. Of course, there are also pulsed rangefinders, typically WILD's DI-3000

It should be noted that the phase measurement does not measure the phase of the infrared or laser, but measures the phase of the signal modulated on the infrared or laser. The construction industry has a handheld laser rangefinder for house measurements that works the same way.

2. Must the plane of the object to be measured be perpendicular to the light?

Usually, precise ranging requires the cooperation of a total reflection prism, and the rangefinder used for house measurement is directly measured by reflection from a smooth wall, mainly because the distance is relatively close, and the signal strength of the reflected light is large enough. It can be known from this that it must be vertical, otherwise the return signal is too weak and the precise distance cannot be obtained.

3. Is it OK if the plane of the measured object is diffuse reflection?

Usually it is also possible. In practical projects, a thin plastic plate will be used as a reflective surface to solve the problem of serious diffuse reflection.

4. The accuracy of ultrasonic ranging is relatively low, and it is rarely used now.