基于表面粗糙度的空间周期与光波波长的相对关系，引入大、小尺度粗糙度概念，建立考虑粗糙度时多层膜正入射光谱特性系数的近似计算模型。以紫外波段的单层膜和多层膜为例进行光谱特性仿真计算，对仿真结果进行横向对比，结果表明，无论是对单层膜还是多层膜，该近似计算模型结果正确，计算精度高，具有较好的适用性。

Based on the relative relationship between surface roughnesss lateral period and light wavelength, the concept of large-scale and small-scale roughness is introduced. When considering surface roughness, approximation calculation model of multilayers spectral characteristic at normal incidence is established. Examples of single layer and multilayer film are simulated with their spectral characteristic curves in ultraviolet region. And the simulation results are compared with published results. It shows that the accuracy of the approximation model is good both for single-layer and multilayer thin film system, which implies good applicability of the presented roughness model.