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Proceedings Paper

Far-field focusing of laser beam based on digital image processing techniques
Author(s): He-yong Zhang; Shuai Zhao; Jin Guo; Li-sheng Liu; Yu-zhen Tian
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Paper Abstract

In order to lead the laser beam transmit in the atmosphere convergently, an experiment of laser focus at the distance of 450m and 300m has been operated in the outdoor place. The actual manipulations are as follows: Firstly, the laser was collimated by a beam expander, then the near-parallel laser beam was transmitted with a Galileo telescope system, and the distance between the concave lens and the convex lens can be tuned through a precise displacement platform, so the focus of the system changed due to the tiny displacement of the concave lens. Secondly, the average power of the laser spot can be measured using power meter, the power is 47.67mW and the standard deviation is 0.67mW while the focal length is 450m. Thirdly, the energy distribution was found through the laser beam analyzer. The spot images were saved using the beam analyzer, then the saved image can be processed with Matlab software afterwards. The function named EDGE and Sobel operator was used in the pre-processing of the saved image, then method of median filter was used in the course of image de-noising and 53H filter was adopted in the signal analysis. The diameter of laser spot was obtained by the method above, the diameter is 5.56mm and the standard deviation is 0.24mm. The spot center excursion is 0.56mm, it is 10.43% of the total diameter of the laser spot. At last, the key factors of the energy dissipation in the focusing system can be summarized as follows: restriction of the diffraction limit, attenuation in the atmosphere, geometrical aberration of optical system, and the diffraction limit and the geometrical aberration are significant in the three factors above, so we can reduce the impact of the both factors during the design of optical system. The reliable referenced data of the system design can be acquired through the primary experiment research.

Paper Details

Date Published: 10 November 2010
PDF: 9 pages
Proc. SPIE 7850, Optoelectronic Imaging and Multimedia Technology, 78502N (10 November 2010); doi: 10.1117/12.871656
Show Author Affiliations
He-yong Zhang, Changchun Institute of Optics, Fine Mechanics and Physics (China)
Shuai Zhao, Changchun Institute of Optics, Fine Mechanics and Physics (China)
Jin Guo, Changchun Institute of Optics, Fine Mechanics and Physics (China)
Li-sheng Liu, Changchun Institute of Optics, Fine Mechanics and Physics (China)
Yu-zhen Tian, Changchun Institute of Optics, Fine Mechanics and Physics (China)

Published in SPIE Proceedings Vol. 7850:
Optoelectronic Imaging and Multimedia Technology
Toru Yoshizawa; Ping Wei; Jesse Zheng; Tsutomu Shimura, Editor(s)

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