High power fiber lasers can be incoherently combined to form the basis for high energy laser applications. Incoherent combining of fiber lasers has a number of advantages over other laser beam combining methods. However, the far-field beam quality of the incoherently combined laser array can still be significantly degraded by atmospheric optical turbulence. In this article, a general scaling law for propagation of incoherently combined laser array through atmosphere is developed by employing theoretical analysis and the common stochastic wave optics technique, and mainly focus on the effects of diffraction and atmospheric optical turbulence. The scaling law developed in the present work differs from standard scaling laws in its definition of irradiance. We show that the far-field irradiance and beam dispersion of any incoherently combined laser array, regardless of near-field beamlets geometry, can be obtained in terms of four basic parameters: laser power, field effective area, pupil field factor, and the Fried parameter.The results show that the formula is simple but predicts peak irradiance and beam dispersion accurately in the far field with varying levels of atmospheric turbulence, regardless of the near-field beamlets geometry.
Pointing precision of attitude stabilization platform is important for airship during its flight and it is one of the key factors to make sure that the antenna isolates disturbance from airship and tracks target with stable attitude. Therefore, in this paper, a method of real-timely measuring pointing precision of attitude stabilization platform based on image processing is established to test attitude stabilization platform performance. In addition, a method of real-time extraction for target with Harris algorithm based on local Otsu threshold segmentation is established for real-time automatic measurement. This method overcomes the problems of long shooting distance, small imaging area of target and the bad light. The experimental results show our method can real-time measure the pointing precision for attitude stabilization platform and the measured value fits well with the design value .
In range test, for measuring the target attitude in target terminal trajectory, we developed a fast Hough transform to real-timely extract axes of the axes symmetry target in high-speed image processing system. The theoretical analysis shows that the accuracy of this scheme is higher than that of standard Hough transform, and the closer to one the absolute value of slope is, the lower the error is. Experimental result shows that the computing speed for line detection of this scheme is higher than standard Hough transform, and the greater the noise is, the more obvious the advantage of speed is. In addition, the error distribution of the experiment is in agreement with the theoretical error distribution.
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