摘要:
本文研究了大气湍流和探测光空间相干性对倾斜离轴激光束通过猫眼光学镜头反射光光强特性的影响.研究表明:由于光阑效应以及光束倾斜或离轴,反射光光强出现振荡和非对称分布现象.大气湍流不会改变其非对称性,但湍流中其光强不再振荡.当猫眼光学镜头存在微弱正离焦δmax情况下,轴上光强可达到最大值.猫眼光学镜头焦距越大,所需δmax越大.但是,大气湍流和探测光相干性好坏都不会改变所需δmax值.在大气湍流中传输距离足够远时,反射光强会成为离轴类高斯分布.随着传输距离的增大,相干性越差的探测光的反射光束扩展可以更小,这与部分相干光自由空间传输规律完全不同.探测光相干性越好,其反射光强受湍流的影响越大,但差异不大.本文所得结果对激光主动探测的应用具有意义.
Abstract:
The influences of atmospheric turbulence and the beam coherence on the average intensity of tilted and off-axis laser beams propagating through a cat-eye optical lens in the turbulence are studied. It is shown that the oscillatory behavior and the skewness of average intensity may appear because there exist apertures and active detection laser beams are tilted or off-axis. The skewness is independent of turbulence, but the oscillatory behavior disappears due to turbulence. For a small positive defocus of a cat-eye optical lens, the on-axis average intensity reaches its maximum. The a positive defocus value becomes small as the focal length of the cat-eye optical lens decreases, but it is independent of atmospheric turbulence and the coherence of active detection laser beams. And the average intensity becomes an off-Gaussian-like profile when the propagation distance is large enough in turbulence. However, less beam spreading may occur with increasing propagation distance for active detection laser beams with less coherence, which is quite different from the behavior of laser beams propagating in free space. The better the coherence of active detection laser beams is, the more the average intensity is affected by the turbulence, but the difference is small. The results obtained in this paper are very useful for the applications is active laser detection.
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