研究了一种低成本折反式红外系统的光学被动消热差技术，通过理论分析温度变化对二次成像系统性能的影响，在次镜上采用曼金折反镜，将热离焦作为附加的初级像差引入像差平衡关系式，通过常规光学系统消像差和热差4种途径（分配光焦度、有效匹配光学材料与镜筒材料、改变透镜形状、引入非球面）实现全被动补偿。在此基础上建立了一个通用模型，在-45℃~+60℃温度范围内的MTF在17 lp/mm时达到0.5以上，冷反射等效温差在0.52℃以内。

Passive athermalizing technology of low-cost mirror-lens infrared optical system was studied, and the athermalization relationship was deduced and the condition expression for mirror-lens secondary imaging system athermalization was got. Defocusing aberration caused by thermal change could be regarded as a kind of primary aberration, and the Mangin mirror was introduced as secondary mirror to eliminate the thermalization aberration. The same as the normal system, four methods could be used to get an athermalization optical system: appropriate focal power distribution, optical material and housing material matching, lens surface shape changing and asphere surface introducing. A generalized optical model was built, and the results show that the MTF is more than 0.5 at 17 lp/mm in -45℃~+60℃ with less than 0.52℃ Narcissus.