粗糙海面对高斯分布激光光束的反射模型推导

Modeling of Gaussian laser beam reflection from rough sea surface

研究激光光束海面反射光强的方向分布特性对海上光电对抗等领域的工程实践具有重要意义.本文采用分形方法模拟粗糙海面,并在海面基准坐标系中建立起描述粗糙海面几何特征的数学方程,然后基于蒙特卡罗方法模拟高斯光束,依据几何光学原理在基准坐标系下推导了高斯光束的海面反射模型,采用该模型可以编程计算激光光束海面反射光强的方向分布.将模拟计算结果与实验结果进行了对比分析,结果表明该模型可以较好地反映激光光束海面反射光强的分布趋势,验证了模型的有效性.

Studies on the direction distribution of laser beam intensity reflected from the sea surface is important for engineering practice in the area of optoelectronic confrontation on the sea surface. In the traditional theory of electromagnetic scattering from rough surfaces, the scattered field from the sea surface can be obtained by solving the Maxwell＇s equations.As is well known, it is difficult to solve the Maxwell＇s equations. Therefore, the numerical calculation method and approximate analytical method are used to obtain the scattered field from the sea surface. However, for the numerical calculation method, it is difficult to meet the computing requirements of large electrically targets such as the sea surface.Meanwhile the approximate analytical method has certain restrictions on the parameters of rough surface in physical approximation. What is more, the inherent error is also caused by the physical approximation. In this paper, we investigate the laser beam reflection from rough sea surface with Monte Carlo method and principles of geometric optics. The rough sea surface which is simulated with the fractal method is divided into a lot of small planes, and the mathematical equations to describe the geometric characteristics of the planes are established in the sea reference coordinate system. After that, based on the simulation of Gaussian beam with Monte Carlo method, the laser beam is divided into a great number of rays and the statistical properties of the rays satisfy the propagation characteristics of Gaussian beam. Then, the laser beam reflection model from the sea surface is derived in the reference coordinate system. The direction distribution of the laser beam intensity reflected from the sea surface is simulated under a certain experiment condition with this model. The results show that the simulation results of laser beam reflection from the sea surface fit the experimental results well.