激光在沙尘暴中的衰减特性研究

Study on Laser Attenuation Character in Sand and Dust Storms

复杂环境中激光传输和散射特性是目标与环境光散射特性研究的基础。主要讨论了激光信号在沙尘中的传输衰减特性。根据 Mie理论研究了具有一定粒径分布沙尘粒子对于激光信号的单次散射衰减特性 ,给出了不同分层沙尘粒子的平均散射截面、粒子平均反照率、平均不对称因子和平均相函数。利用四通量法和蒙特卡罗法研究了激光在分层沙尘大气中的多重散射和斜程传输衰减特性 ,并给出它们与能见度及高度的变化关系。最后 ,在考虑多重散射时 ,分别用以上两种方法数值计算了 1 .0 6 μm激光在斜程沙尘大气中的衰减率 ,并与单次散射结果进行了比较。结果表明 ,能见度较低时 ,不考虑多重散射效应会带来较大的误差 ;在斜程沙尘大气激光传输时 ,随分层数增加 ,数值结果就越精确。

The study on laser transmission and scattering characteristics in complex environments is the basis research of light scattering from target and environment. The severe attenuation caused by laser propagation in sand and dust storms was mainly discussed in this paper. The attenuation characteristic of laser was studied with Mie theory for single scattering of sand and dust particles with special size distribution. Based on Mie theory, the average scattering cross section, albedo, asymmetry factor, and phase function were calculated. The laser multiple scattering and attenuation characteristics of slanting transmission in the layering sand dust atmosphere were studied by using four-flux model method and Monte-Carlo method, and the relationship between attenuation and visibility in difference heights was also given. Finally, after considening of multi-scattering, numerical calculations of specify attenuation were made for laser signal of 1.06 μm in sand and dust atmosphere by using the above two methods respectively, and the results were compared to the condition of single scattering. It is shown that biggish error can be brought in the low visibility take no account of multiple scattering, and that the more layers of the sand and dust atmosphere is divided into for slanting transmission, the more accurate the result is.