Meskernel have mainly focused on the field of laser measurement and control, Laser Ranging Module, Laser Distance Sensor, Laser Rangefinder Module as long as Laser Distance Meter, Laser Rang Finder and 2D 3D LiDAR.
What is a laser rangefinder?
A laser rangefinder is an instrument that uses laser light to accurately measure the distance to a target. The initial laser rangefinder simply measured the distance from point to point. With the continuous advancement of technology, many indirect measurement and automatic calculation functions have been extended.
How laser rangefinder works?
When the laser rangefinder is working, it emits a very thin laser beam to the target. The photoelectric element receives the laser beam reflected by the target. The timer measures the time from transmitting the signal to receiving the laser beam. The time is multiplied by the speed of light and divided by two. Calculate the distance from the observer to the target.
According to different working principles, laser ranging methods can be roughly divided into four types: pulse method, interference method, phase method and trigonometric method.
Laser ranging method:
1. Pulse Ranging Method
The principle of the pulse ranging method is based on the constant propagation speed of light. The pulse emitted by the laser is projected onto the target to be measured through the transmitter. It is received by the receiver through the diffuse reflection of the target, and then converted into After the electrical signal is amplified by an amplifier, the time required for a round trip of light is directly measured using digital circuits or image methods, and then the distance is calculated and displayed.
The main feature of this ranging method is that the light beam can be emitted in the form of pulses, and the distance is measured through the diffuse reflection of the target to be measured. There is no need to set up a special cooperative target, and it is very convenient to use. However, due to the uneven surface of the reflector and the limitations of time measurement technology, the accuracy of this ranging device is low, with a general error of 2-5m.
2. Interference Ranging Method
The interference ranging method is based on the principle of light wave interference for distance measurement. According to the principle of light interference, two beams of light with a fixed phase difference and the same frequency, the same vibration direction or a small angle between the vibration directions overlap each other. Interference will occur. After the incident laser reaches the spectroscope, it is divided into reflected light and transmitted light, which are reflected by the fixed reflector and the movable reflector respectively and then merge into a coherent beam at the spectroscope. The difference in the distance between the two light beams will affect the amplitude of the resultant light and ultimately the light intensity.
It uses this principle to make the laser beam produce alternating light and dark interference fringes, which are received by the photoelectric converter and converted into electrical signals. After processing, they are counted by the photoelectric counter, thereby realizing the detection of the displacement. Since the wavelength of laser is extremely short, especially the laser has good monochromaticity and very accurate wavelength value, the accuracy of distance measurement using laser interference method is very high.
3. Triangulation Method
The object surface, light source and receiving system are placed at three points to form a triangular light path, which is the triangular ranging method. The beam emitted by the laser light source is focused by the lens and irradiated onto the surface of the object to be measured. The light is reflected by the object surface and is received by the photoelectric receiving system. In order to achieve clear imaging on the photosensitive surface, a focusing lens can be added in front of it. If the object surface moves, the movement of the light spot on the photosensitive surface can be calculated based on the triangle similarity principle. On the contrary, if the movement amount of the light spot on the photosensitive surface is known, the movement amount of the object surface can also be calculated.
The laser triangulation ranging method has various forms. It can either make the laser incident on the object surface, and the photoelectric receiving system receive it at an angle; it can also make the laser incident obliquely on the object surface, and the photoelectric receiving system receives it positively or obliquely. How to place the light source and receiving system mainly depends on the target tested by the measurement system, the structure of the measurement system, and the design of other auxiliary equipment of the measurement system.
4. Phase Ranging Method
Phase laser rangefinders use radio band frequencies to amplitude modulate the beam. Measure the phase delay caused by the modulated light traveling back and forth to the measuring line once,and then convert the distance represented by this phase delay based on the wavelength of the modulated light, which is equivalent to using an indirect method to measure the time it takes for light to travel back and forth to the measuring line.
Simply put, the phase method is to calculate the total phase delay and the number of wavelengths of the laser based on the known laser frequency and the phase delay of one round trip per unit distance, and further calculate the part of the signal that is less than one wavelength round trip, so as to the measurement distance is converted into a measurement of the full number of wavelengths and a measurement of less than one wavelength. By measuring less than one wavelength, the phase ranging method can achieve very high accuracy.
Laser Rangefinder Classification:
①Handheld laser rangefinder: The measurement distance is generally within 200 meters, and the accuracy is relatively high, generally around 2mm. In addition to measuring distance, it can also generally calculate the volume of the measured object.
②Telescopic laser rangefinder: The measurement distance is generally around 600-3000 meters, and the accuracy is low, usually around 1 meter. The main application range is long-distance measurement in the field.
One-dimensional laser rangefinder: used for distance measurement and positioning;
Two-dimensional laser rangefinder: used in contour measurement, positioning, area monitoring and other fields;
Three-dimensional laser rangefinder: used in three-dimensional contour measurement, three-dimensional space positioning and other fields.
