激光阴影法探测大气湍流中二维风矢量的可行性  

Feasibility of Laser Shadow Method to Detect Two-Dimensional Wind Vector in Atmospheric Turbulence

作　　者：沈刘晶 梅海平 任益充 张骏昕 Shen Liujing;Mei Haiping;Ren Yichong;Zhang Junxin(Institutes of Physical Science and Information Technology,Anhui University,Hefei,Anhui 230601,China;Key Laboratory of Atmospheric Optics,Anhui Institute of Optical and Fine Mechanics,Chinese Academy of Sciences,Hefei,Anhui 230031,China;Science Island Branch of Graduate School,University of Science and Technology of China,Hefei,Anhui 230026,China;Advanced Laser Technology Laboratory of Anhui Province,Hefei,Anhui 230037,China)

机构地区：[1]安徽大学物质科学与信息技术研究院,安徽合肥230601 [2]中国科学院安徽光学精密机械研究所大气光学重点实验室,安徽合肥230031 [3]中国科学技术大学研究生院科学岛分院,安徽合肥230026 [4]先进激光技术安徽省实验室,安徽合肥230037

出　　处：《中国激光》2021年第13期113-123,共11页Chinese Journal of Lasers

基　　金：国家自然科学基金青年基金(11904369);中国科学院装备预研联合基金(6141A01130202)。

摘　　要：提出了一种利用激光阴影图像探测大气湍流中二维横向风矢量的方法,并开展了数值模拟和实验研究。通过移动无限长的相位屏模拟光传输路径上的横向风,采用基于归一化互相关原理的整像素搜索算法计算激光阴影的移动速度,并分析了路径上的横向风及其非均匀分布对激光阴影移动速度的影响。100 m长的激光阴影成像探测对比实验结果表明,在采样频率足够大时,激光阴影的移动速度与平均横向风速之间满足线性关系。超声风速仪的实测值与激光阴影法的拟合值相关系数达到0.949,这表明利用短曝光激光阴影图像获取路径的平均二维横向风矢量是可行的;且该方法能定量展现激光传输路径上大气湍流涡旋的发展和演化,对于大气湍流风场的遥感监测及相关工程应用具有重要的参考价值。Objective Atmospheric turbulence is a key research topic in the field of atmospheric and environmental science. It greatly influences the development of aerospace, aircraft safety control, and laser communication. Random fluctuations in the refractive index of the atmosphere along the laser propagation path cause a series of transmission effects. Therefore, a laser beam projected onto a large area microcrystalline reflective film appears as irregular dynamic speckles in the far-field plane. In addition, there are constant directional moving shadows in the laser speckle images, which are caused by the path integral effect of transverse wind. Theoretically, two-dimensional(2 D) laser shadow images can be used to detect the path transverse averaged wind velocity. However, due to the deformation of laser shadows and uneven transverse wind distribution, it is uncertain whether the moving velocity of laser shadows calculated using a cross-correlation algorithm can accurately reflect the moving velocity of the flow field and how the sampling frequency of images affects the calculation results. To address these problems, a new method for simulating transverse wind in atmospheric turbulence based on the dynamic phase screen theory is developed for quantitative simulation analysis. In addition, simulation results are substantially verified by experiments. We hope that our study will be helpful in the remote sensing detection of wind and other engineering applications.Methods A complete pixel search algorithm based on normalized cross-correlation is used to calculate the displacement of laser shadows.First,the transverse wind along the laser propagation path is simulated by moving infinitely long and nonstationary phase screens.Images of lasers transmitted through the atmosphere are obtained for uniform and nonuniform transverse wind distributions.Then,the relationships between the velocity of laser shadows and wind speed are analyzed separately when the wind flow field is distributed differently.In addition,the appropriate

关 键 词：大气光学 激光大气传输 大气湍流 横向风 阴影法 

分 类 号：O435[机械工程—光学工程]