针对目前低成本、小型化、长焦距非制冷热成像系统要求光学系统具有成像质量高、相对孔径大、结构尺寸小、温度适应性广的特点，在对多种实现超紧凑型光学系统结构的分析比较基础上，选用折反式结构，设计了一种大相对孔径超紧凑型红外光学系统。该光学系统的相对孔径达到了1/0.89，远射比达到了0.67。结合该光学系统的结构特点，仅使用Ge材料即实现了-40 ℃～60 ℃温度范围内的被动无热化设计。采用杂散光分析软件对系统进行了杂散光分析，提出了合理的杂散光抑制措施。设计分析结果表明：该光学系统在工作温度范围内像质优良（其在不同环境温度下的调制传递函数均接近衍射限）、体积结构紧凑，杂散光可控，可满足小型化、长焦距非制冷热成像系统的使用需求。

According to the requirements of high imaging quality, fast F-number, miniaturized dimension and wide environmental adaptability in the low cost, small size and long focal length uncooled thermal imaging systems presently, several compact optical configurations with fast F-number and small obscuration are given. Based on catadioptric structure, a fast F-number compact long infrared optical system with relative aperture of 1/0.89 and telephoto ratio of 0.67 is designed. This optical system can be used for the low-cost uncooled compact infrared imaging system. Optical passive athermalization at -40 ℃~60 ℃ temperature range is realized by using athermalization design method. Stray light influence of the optical system is also analyzed. The result shows that the optical system works well through entire operating temperature range, and obtains the advantages of compact structure, small volume and so on. It can meet the requirements of the small size long focal length uncooled thermal imaging systems.