对同步辐射红外光束线中由两个相同光学参数的超环面镜组成的对称式光学系统的像差和超环面镜缩放比之间的关系进行分析。计算结果表明，使用3倍压缩比的超环面镜可将上海光源同步辐射红外光束线站BL06B的500 μm波长的红外光在金刚石化学蒸汽沉积（CVD）窗上的透射率优化到50%左右；光学设计软件Zemax光线追迹结果表明，该对称式结构的像差不影响中红外光束的聚集性能。Synchrotron Radiation Workshop模拟计算结果表明，使用3倍压缩比的超环面镜和直径15 mm的金刚石CVD窗获得的光子通量与使用1倍压缩比的超环面镜和直径45 mm的金刚石CVD窗获得的光子通量相当，但前者的碳峰吸收约为后者的37%。由两个3倍压缩比的超环面镜组成的对称式光学结构在兼顾近中红外性能的同时，优化了同步辐射红外光束线在远红外波段的性能。

The relationship for synchrotron radiation infrared beamline between the aberration of symmetric optical system formed by two toroidal mirrors with the same optical parameters and pantograph ratio of the toroidal mirrors is analyzed. Computation results show that toroidal mirror with 3∶1 compression ratio can optimize the infrared beamline transmittance of chemical vapor deposition (CVD) windows to 50% at the working wavelength of 500 μm on the Synchrotron Radiation Infrared beamline BL06B at Shanghai Synchrotron Radiation Facility. The ray trace results by the optical design software Zemax show that the aberrations of the symmetrical structure do not affect the aggregation performance of the infrared beamline. Synchrotron Radiation Workshop simulation results show that the photon flux obtained with a pair of three times compression ratio toroidal mirrors and a diameter of 15 mm CVD diamond window is equal to a pair of 1 time compression ratio toroidal mirrors and a diameter of 45 mm CVD diamond window, while the former carbon peak absorption is about 37% of the latter. The symmetric optical structure formed by two toroidal mirrors with 3 times compression ratio can be used to optimize the performance of the SRIR beamline in the far infrared wave band, while the performance in the near and middle infrared wave band are also take into account.