基于表面生成法的粗糙基底上半透明涂层的光散射特性

Light Scattering Properties of Semitransparent Coatings on Rough Substrate Based on Surface Generation Method

针对光在半透明涂层和粗糙基底构成的两层粗糙面的散射过程,采用表面生成法,考虑入射遮蔽以及多次散射效应,构建表面散射的蒙特卡罗模型,得到粗糙基底上半透明涂层的反射光的能量分布,研究涂层厚度、表面粗糙度、入射光波长等对双向反射分布函数(Bidirectional Reflectance Distribution Function,BRDF)的影响.结果表明,BRDF受表面的粗糙程度影响较大,其峰值随表面均方根斜率的增加线性递减;半透明涂层厚度影响BRDF峰值的大小,厚度为十分之一波长时,BRDF达最小值;近红外光入射时镜反射方向附近BRDF的局部分布曲线相对于可见光入射时有展宽趋势,且方向半球反射率相对于可见光入射时更大.

For the scattering process of light through the two rough surfaces consisted of semitransparent coatings and rough substrate,considering the shading effect and multiple scattering, Monte Carlo model of surface scattering was established based on surface generation method. The reflected light distribution of the semitransparent coatings on rough substrate was obtained. The effects of coatings thickness, surface roughness and incident light wavelength on Bidirectional Reflectance Distribution Function （BRDF） were studied. Simulation results show that BRDF is largely affected by surface roughness, and the reflection peak decreases linearly with the root-mean-square slope of the surface. The semitransparent coatings thickness changes the value of BRDF. When the thickness is equal to one-tenth of the wavelength,BRDF reaches the minimum value. The local distribution of BRDF in the specular reflection direction with nearinfrared light illumination tends to broaden up in comparison with visible light illumination, and the directional hemispherical reflectance with near-infrared light illumination is also larger.