冷反射是评价制冷型红外光学系统成像质量的一个重要参数。分析了制冷红外光学系统产生冷反射的原因，讨论了在光学设计软件中对冷反射现象的控制与分析方法;提出了采用逆光路追迹光线的方法分析光学系统中各个光学表面产生的冷反射大小;设计了一个工作在长波红外波段的制冷型光学系统，系统焦距为120 mm;采用逆光路追迹像点弥散的方法分析了光学系统各个表面产生的冷反射大小。其结果与采用光学设计软件给出的冷反射评价参数YNI与I/Ibar、以及利用经验公式计算得到的结果一致，且采用逆光路追迹分析冷反射的方法更加直观。

The narcissus is an important parameter for evaluating the imaging quality of the cooled infrared optical system.The cause of narcissus for infrared optical system was analyzed.The method for controlling and analyzing narcissus in optical design software was discussed.A method of inverse path tracing rays was proposed for analyzing the magnitude of narcissus of each surface in the optical system.A cooled optical system working in the LWIR was designedwhich focal length is 120 mm.The method of inverse path tracing rays was used to analyze the magnitude of narcissus of each surface of the optical systemwhich was in accordance with the YNI and I/Ibar parameters given by the optical design softwareand the results calculated by the empirical formula.And the method of inverse path tracing rays for calculating narcissus is more direct.