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Atmospheric coherence length represents the diffraction limit of light wave propagation through atmospheric turbulence, which characterises the integrated optical turbulence intensity in the atmospheric transmission path of light waves, and the measurement of atmospheric coherence length is of great significance. A light column turbulence lidar for atmospheric coherence length measurements has been developed based on differential image motion method and oblique range imaging for laser light column, which can obtain atmospheric coherence length profiles at a certain height in the vertical direction with a high spatial resolution, and can overcome the problem of non-active turbulence measurement devices that are not able to measure without suitable beacons or beacons that are occluded. The basic principle and system structure of differential light column lidar are introduced, and the whole lidar system can be divided into laser transmitting unit, signal receiving unit and control unit. The laser transmitter unit adjusts the direction of laser emission through the reflector, CCD camera, diaphragm and stepper motor. The signal receiving unit receives the beam backward scattering signals through the telescope and CCD camera to obtain the light column image, and adjusts the position of the CCD camera through the stepper motor to achieve focusing. The control unit receives and sends signals to control the operation of the entire system. A preliminary detection experiment was carried out with this lidar, and the height distribution profile of atmospheric coherence length was obtained. The variation trend of atmospheric coherence length with altitude is consistent with the theoretical trend, which verified the functionality of the lidar system.
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