Have you understood the laser rangefinder? Is it easy to understand from its literal meaning? Here are some basic introductions about it.

What is laser rangefinder

Laser rangefinder is an instrument that accurately measures the distance of the target by using a certain parameter of the modulated laser. Pulse laser rangefinder emits one or a series of short pulse laser beams to the target during operation, and the laser beam reflected by the target is received by the photoelectric element. The timer measures the time from emission to reception of the laser beam, and calculates the distance from the rangefinder to the target.

When the power of the emitted laser beam is sufficient, the measuring range can reach about 40 kilometers or even more. The laser rangefinder can work day and night, but when there are substances with high laser absorption in space, the distance and accuracy of its ranging will decline.

The first laser in the world was the ruby laser 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 stage.

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 is a new technology developed in the 1960s. It is a kind of light with pure color, highly concentrated energy and good directivity. Laser rangefinder is an instrument that uses laser for ranging. Its working principle is very simple: the distance is measured by measuring the time from the beginning of laser emission to the reflection of laser from the target. For example, using a laser rangefinder to measure the distance of the moon, if the time from the start of laser emission to the reflection from the moon is measured as 2.56 seconds, the one-way time of laser emission to the moon is equal to 1.28 seconds, and the speed of laser is the speed of light, equal to 300000 kilometers per second. Therefore, the measured distance from the moon to the earth is the product of one-way time and the speed of light, that is, 384000 kilometers. In order to transmit and receive laser and time, the laser rangefinder is composed of laser transmitter, receiver, clock frequency oscillator and distance counter.

Laser rangefinder can also be used for tracking and ranging satellites, measuring aircraft flight altitude, aiming and ranging targets, topographic mapping and survey.

working principle

1. Use the principle of infrared ranging or laser ranging

The ranging principle can be basically reduced to measuring the time required for light to and from the target, and then calculate the distance d through the light speed c = 299792458m / s and the atmospheric refractive index n. Because it is difficult to measure the time directly, it is usually to measure the phase of continuous wave, which is called phase measuring rangefinder. Of course, there are also pulse rangefinders.

It should be noted that phase measurement is not to measure the phase of infrared or laser, but to measure 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.

2. The plane of the measured object must be perpendicular to the light

Usually, 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.

3. The plane of the object can be measured as diffuse reflection

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.

4. The entertainment grade products of pulse laser rangefinder can reach the display accuracy of 1m and the measurement accuracy of ± 1m. The display accuracy of measurement grade products is 0.1M and the measurement accuracy of ± 0.15m.

5. The accuracy of phase laser rangefinder can reach 1mm error, which is suitable for various high-precision measurement purposes.

Classification of laser rangefinder

Laser rangefinder is divided into laser rangefinder and telescope laser rangefinder.

1. Handheld laser rangefinder: the measurement distance is generally within 200 meters, and the accuracy is about 2mm. This is the most widely used laser rangefinder at present. In terms of function, in addition to measuring distance, it can generally calculate the volume of the measured object.

2. Cloud service laser rangefinder: transmit the measurement data on the laser rangefinder to mobile terminals such as mobile phones and tablet computers in real time through Bluetooth; The data can be transmitted to the cloud server through WiFi networking, and the measurement data can be shared in real time with remote construction partners.

3. Telescope type laser rangefinder: the measurement distance is relatively long. Generally, the measurement range is about 3.5m-2000m. There are also ranging telescopes with a maximum range of about 10km. Due to the collimation requirements of ranging telescopes, the blind area is below 3.5m, and the laser telescope above 2000m is generally used

YAG laser has a wavelength of 1.064 microns. In order to achieve a large measurement range, the laser power is large. Users are advised to pay attention to laser protection.

The main application range is outdoor medium and long-distance measurement.

One dimensional laser rangefinder

Used for distance measurement and positioning; Laser range finder

Scanning laser range finder

Used in contour measurement, positioning, area monitoring and other fields;

3D laser range finder

It is used in 3D contour measurement, 3D spatial positioning and other fields.

Schematic diagram of using laser to measure the distance from the moon to the earth

purpose

Laser rangefinder is widely used in topographic survey, battlefield survey, ranging of tanks, aircraft, ships and artillery, measuring the height of clouds, aircraft, missiles and man-made satellites. It is an important technical equipment to improve the accuracy of high tanks, aircraft, ships and artillery. As the price of laser rangefinder continues to decline, laser rangefinder is gradually used in industry, which can be widely used in industrial measurement and control, mines, ports and other fields.

Routine maintenance

Problems needing attention when using the laser rangefinder: the laser rangefinder cannot be directly measured with the human eye to prevent damage to the human body. At the same time, the general laser rangefinder does not have waterproof function, so we need to pay attention to waterproof. The latest laser rangefinder of Leopold in the United States is mainly suitable for outdoor hunting lovers in the United States, so the advantage of its production is that it can be waterproof and fog proof, and it is equipped with color coating of branches and leaves of jungle trees.

The laser does not have the function of anti falling, so the laser rangefinder is easy to break the illuminator.

Laser rangefinder maintenance:

① Regularly check the appearance of the instrument and timely remove the dust, dirt, grease, mildew, etc. on the surface.

② When cleaning the eyepiece, objective lens or laser emitting window, use a soft dry cloth. It is strictly prohibited to scratch with hard objects to avoid damaging the optical performance.

③ This machine is a high-precision instrument integrating light, machinery and electricity. It should be handled with care in use. It is strictly prohibited to squeeze or fall from a height to avoid damaging the instrument.