The laser technology is mainly used to detect the work, and it is realized by using the excellent characteristics of the laser as a light source and corresponding photoelectric elements. It has the advantages of high precision, large measuring range, short detection time, non-contact type, etc. It is often used to measure parameters such as length, displacement, speed and vibration. When the object to be measured is irradiated with laser light, certain characteristics of the laser light are changed, and the shape, physical and chemical characteristics of the measured object, and the amount of change thereof can be known by measuring the response such as strength, speed or kind. The types of response include the release of products such as light, sound, heat, ions, and neutral particles, and changes in amplitude, phase, frequency, polarization direction, and propagation direction of reflected light, transmitted light, and scattered light.
â—†Laser ranging
The basic principle of laser ranging is to direct the laser with a speed of light C to the target to be measured, and measure the time it returns, thereby obtaining the distance d between the laser and the target to be measured. That is: d=ct/2 where t is the time interval between the laser emitting and receiving the return signal. It can be seen that the accuracy of such laser ranging depends on the accuracy of the time measurement. Since it utilizes a pulsed laser beam, in order to improve the accuracy, the laser pulse width is required to be narrow, and the light receiver has a fast response speed. Therefore, long-distance measurement uses a solid-state laser with a large output power and a carbon dioxide laser as a laser source; a close-range measurement uses a gallium arsenide semiconductor laser as a laser source.
â—†Laser length measurement
It can be seen from the optical principle that the relationship between the maximum measurable length L of the monochromatic light and the wavelength λ of the light source and the line width Δλ is measured by a common monochromatic light source, and the maximum measurable length is 78 cm. If the measured object exceeds 78cm, it must be measured in sections, which will reduce the measurement accuracy. If a HeNe laser is used as the light source, the maximum measurable length can be several tens of kilometers. Generally, the measurement length is less than 10m, and the measurement accuracy is guaranteed to be within 0.1μm.
â—†Laser interferometry
The principle of laser interferometry is to use the characteristics of the laser - coherence to process the information of the phase change. Since light is a kind of high-frequency electromagnetic wave, it is difficult to directly observe the phase change. Therefore, it is much easier to observe the phase difference by converting the phase difference into the light intensity. Generally, the distance between the reference light of the reference reflection surface and the observation light reflected by the observation object, or the interference between the reference light and the light whose phase changes after the observation of the object is used, the distance of the object to be measured can be measured non-contactly and The size, shape, etc. of an object whose measurement accuracy reaches the wavelength of light. Since the wavelength of light is very short, the measurement accuracy is quite high.
â—†Lidar
Lidar is used to emit laser beam into the air, and analyze and process the scattered signal light to know the type and quantity of suspended molecules in the air and the distance. With short pulse laser, it can be observed in time series.
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