针对常规红外干扰技术存在的能量无法集中、隐蔽性差且无法进行变倍切换等实际问题，提出一种离轴双反射式激光干扰扩束系统的设计方案，并对离轴双反射镜组，转向平面反射镜及支撑固定机构等主要组成部分进行了光机结构设计.为实现扩束比的变倍切换功能，采用新型离轴副镜组件设计;为减小镜面变形，离轴主副镜组均采用微应力设计.分析结果表明，在－20～+60℃温度范围内，主副镜组轴向最大位移小于等于0.01 mm，主副镜组的反射镜面形误差小于等于71.9 nm;系统一阶固有频率108.3 Hz，其支撑结构应力响应远小于材料的屈服极限.实际测试发现，系统可实现1:10.02(19.92,25.02)扩束比，满足设计技术指标要求.分析及试验结果表明，系统光机结构设计合理，完全满足实际应用要求.

In view of the actual problems existed in the routine infrared jamming technology, such as failure to meet required energy concentration, poor concealment and unable to be realized zoom, a design scheme regarding a new offaxis double mirror type of laser jamming applied at beam expander was put forward. The opticalmechanical structures of such key components as the battery of offaxis double mirrors, the steering mirror and supporting and fixing mechanisms, etc. were designed and analyzed. A newstyle structural design of offaxis was adopted, realizing zoom function of the expansion ratio; the design of microstress was adopted for components of both the main and secondary mirrors and the components of steering mirror. Analysis results show that the first order natural frequency is 108.3 Hz, and stress responses of the structure is also smaller than yield limit of the material; in the temperature range of －20℃ to +60℃, the maximum displacement of the main and secondary mirrors is below or equal to 0.01mm and the surface accuracy is below to 71.9 nm. After the actual detection, the beam expanding ratio obtained is 1:10.02(19.92, 25.02), meeting the requirement of designed technical index. Analysis and experimental results demonstrate that designs of the optical and mechanical structure are effective that can meet the requirements of actual applications.