Laser length measurement

Precise measurement of length is one of the key technologies in precision machinery manufacturing industry and optical processing industry. Modern length measurement is mostly carried out by using the interference phenomenon of light waves, and its accuracy mainly depends on the monochromaticity of light. Laser is the most ideal light source, which is 100,000 times purer than the best monochromatic light source (krypton-86 lamp) in the past. Therefore, the laser length measurement range is large and the precision is high. According to the optical principle, the relationship between the maximum measurable length L of monochromatic light, the wavelength λ and the spectral line width δ is L=λ2/δ. The maximum length that can be measured with a krypton-86 lamp is 38.5 cm. For longer objects, it needs to be measured in sections, which reduces the accuracy. If a helium-neon gas laser is used, it can measure up to tens of kilometers. Generally measure the length within a few meters, and its accuracy can reach 0.1 microns.

Its principle is the same as that of radio radar. After the laser is aimed at the target and launched, its round-trip time is measured, and then multiplied by the speed of light to obtain the round-trip distance. Because the laser has the advantages of high directivity, high monochromaticity and high power, these are very important for measuring long distances, determining the orientation of the target, improving the signal-to-noise ratio of the receiving system, and ensuring the measurement accuracy. increasingly received attention. The lidar developed on the basis of the laser rangefinder can not only measure the distance, but also measure the azimuth, speed and acceleration of the target. Radar, ranging from 500 to 2000 kilometers, the error is only a few meters. At present, ruby lasers, neodymium glass lasers, carbon dioxide lasers and gallium arsenide lasers are often used as light sources for laser rangefinders.

 thickness measurement

Using the principle of triangular ranging, a precision laser ranging sensor is located on the upper and lower parts of the C-shaped frame. The modulated laser emitted by the laser hits the surface of the object to be measured, and the signal of the linear array CCD is sampled and processed. Under the control of the control circuit, the linear CCD camera obtains the distance between the measured object and the C-frame synchronously, and calculates the thickness of the intermediate measured object through the data fed back by the sensor. Since the detection is carried out continuously, the continuous dynamic thickness value of the measured object can be obtained.

1. Thickness measurement with single laser displacement sensor

The measured object is placed on the measuring platform, the distance from the sensor to the surface of the platform is measured, and then the distance from the sensor to the surface of the measured object is measured, and the thickness is measured after calculation. It is required that there is no air gap between the measured object and the measuring platform, and the measured object is not lifted. These stringent requirements can only be fulfilled offline.

2. Thickness measurement with dual laser displacement sensors

The main principles and applications of two laser sensors

Using the characteristics of high directivity, high monochromaticity and high brightness of the laser can realize non-contact long-distance measurement. Laser sensors are often used for the measurement of physical quantities such as length, distance, vibration, speed, and orientation, as well as for flaw detection and monitoring of atmospheric pollutants. In short, the application fields of laser sensors are becoming more and more extensive. The main principles and applications of the two types of laser sensors are described below.

Laser Displacement Sensor

The laser displacement sensor can realize non-contact long-distance measurement by utilizing the characteristics of high directivity, high monochromaticity and high brightness of the laser. Laser displacement sensor (magnetostrictive displacement sensor) is a new type of measuring instrument made of these advantages of laser. Its appearance greatly improves the accuracy and reliability of displacement measurement, and also provides effective non-contact displacement measurement. measurement method.