内壁蜂窝结构是决定遮光罩杂散光抑制性能的主要因素，掌握其各向异性辐射传输特性对遮光罩的杂散光分析和优化设计具有重要意义.针对蜂窝结构单元，建立辐射传输模型，导出了表面双向反射分布函数的离散表达式；通过蒙特卡罗法模拟蜂窝结构单元的辐射传输过程，分析了几何参量和涂层反射率对等效面反射特性的影响；根据模拟所得双向反射分布函数数据库，建立了用于遮光罩杂散光分析的蜂窝结构等效面的反射特性概率模型.分析结果表明，蜂窝结构对杂散光呈现很强的后向散射特征，等效面的反射特性概率模型与直接模拟结果符合很好，可用于遮光罩杂散光分析和设计.

Honeycomb structure on the inner wall of baffle dominates the performance of stray light suppression of the baffle. It is significant to understand the anisotropic radiation transfer characteristics of the honeycomb cell for stray light analysis and optimum design of baffle. A numerical model of radiative propagation was built for honeycomb cell and the discrete BRDF expression was deduced for the equivalent surface. By simulating the stray light propagation with the Monte Carlo method, the effects of geometric parameters and reflectivity of coating on BRDF of the equivalent surface were analyzed. Based on the obvious backscattering of the honeycomb structure predicted by the BRDF analysis, the probability model of anisotropic reflection was established for the equivalent surface. The BRDF results predicted by the probability model show good agreement with that of the direct simulation, and it can be well used in stray light analysis and design of baffle.