光学系统表面的反射与材料的吸收会降低空间调制傅里叶变换红外光谱仪中光的透过率。 通过对干涉系统透过率函数的计算和对采样干涉图与复原光谱的仿真, 结果显示透过率函数作用下的干涉图像对比度下降, 复原光谱中的谱线强度发生衰减。 分析表明, 干涉图像对比度的下降主要是由分束器对入射光的有效反射引起的, 而谱线强度的衰减则是由与增透膜的光强反射率R1、 分束膜的光强反射率R2和材料的吸收系数α有关的透射效率函数所决定。 通过分析论证, 对于本文所研究的光谱波段, 可以不考虑材料的吸收, 所以透射效率主要由R1和R2决定。 由此, 将透射效率作为设计指标, 根据系统的设计需求, 就可以得到增透膜与分束膜光强反射率的容限值。

The reflection of the optic system surface and the absorption of the infrared material could reduce the transmission of the incident light in spatially modulated Fourier transform infrared spectrometer. Through the calculation of the transmission function of the interference system and the simulation of the interferogram image and recovered spectrum affected by transmission function, it was indicated that the contrast of the interferogram image declined and the spectral line intensity weakened. The theoretical analysis shows that the contrast of the interferogram image was related to the intensity reflectance of the anti-reflection film, and the attenuation of the spectrum was determined by transmission efficiency concerned with intensity reflectance R1 of the anti-reflection film, intensity reflectance R2 of the beam splitter film, and the absorption coefficient. By means of the analysis and argumentation, the absorption of the material could be ignored in our investigative wave band. So the transmission efficiency was determined only by R1 and R2. Then taking the transmission efficiency as the design target, according to the transmission required by system, the tolerance of the R1 and R2 could be gained.