TRANSMISSION CHANNEL ALIGNMENT FOR LASER LOCATION SYSTEM

Pronin V.V. Transmission channel alignment for laser location system. Scientific and Technical Journal of Information Technologies, Mechanics and Optics, 2020, vol. 20, no. 1, pp. 39–44 (in Russian). doi: 10.17586/2226-1494-2020-20-1-39-44

Subject of Research. The transmitting channel of the laser location system, composed of a laser and its telescopic radiation expander, forms an output laser beam with specified geometric parameters. In particular, it can be a quasi- parallel beam or have a waist at a given distance. Method. The high-precision equipment setup is developed on the basis of geometrical optics methods providing the formation of a laser beam with preset geometrical parameters. The equipment setup is based on a mirror parabolic collimator and a matrix pyroelectric camera, which is located in its focal plane and is able to move along its axis. Flat diagonal mirrors are installed in such a way that they separate the laser beam coming out of the expander and direct it at the peripheral diametrically opposite collimator light zones. After reflection from the parabola, the beams converge at a sufficiently large angle convenient for further analysis. If the laser location system is aligned with the aim to reduce divergence, the matrix camera is positioned in the focal plane of the collimator. If the alignment is intended to create a waist of laser radiation at a given distance, then the matrix camera is placed at a certain distance from the focal plane. The alignment process is reduced to the registration of the gravity centers for the beams coming from parabola edges with their alternate overlapping. As soon as the difference in the beam coordinates becomes commensurate with the measurement error, the process is completed. Main Results. The technique involves the alignment of the telescopic expander together with the laser and eliminates errors associated with the installation of these two components relative to each other. During the operation, labor-intensive movements of the photodetector in space and subsequent calculations are not required, and fewer optical elements are used. Moreover, the effect of fluctuations in the laser radiation power is excluded. According to the proposed technique, a system is aligned consisting of a CO2 laser with divergence of 7.5 mrad and a telescopic expander with tenfold magnification. The obtained alignment accuracy amounts to 10 % of the laser radiation divergence value. It is shown that the main contribution to alignment accuracy is made by coordinate registration error of the image gravity centers, which largely depends on fluctuations in the laser radiation power. Practical Relevance. The proposed technique has a low labor intensity, sufficient accuracy for practical application and can be implemented in the laboratories of enterprises engaged in the production of laser location systems.

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