设计了一款高性能的紧凑型双视场长波红外光学系统, 该光学系统由前固定组、变倍调焦组、后固定组、中继组组成。采用机械补偿变焦方式、光瞳匹配技术、二次成像和二次折叠, 有效地对光学系统纵向和横向尺寸进行了约束, 外形包络在 220 mm×95 mm(局部 135 mm)×50 mm(局部 110 mm)范围内, 系统紧凑, 体积小。通过光学和结构材料的优选搭配及光学系统参数优化配置, 在-40℃～70℃范围内, 控制了光学系统热差, 光学系统光轴稳定, 小视场光轴稳定性＜0.04 mrad, 大/小视场转换光轴平行性＜0.1 mrad; 应用该光学系统的热像仪性能高, MRTD(3 cyc/mrad)＝0.07 K, NETD＝30 mK。设计结果表明光学系统像质良好, 满足热像仪使用要求。

A compact dual fields of view infrared optical system with high performance is designed, which consists of a front fixed group, a zoom focus group, a rear fixed group and a relay group. The vertical and horizontal dimensions of the optical system are designed to be minimum by adopting mechanically compensated zoom, the entrance pupil matching the exit pupil, reimage, and twice folding optical axis. The three-dimensional figure is 220 mm×95 mm×50 mm. The thermal aberration is controlled between －40 to 70℃ by choosing optical material and structural material, and optimizing the optical system parameters. The line of sight of the optical system is stabilized. The error of the line of sight of the narrow field of view is less than 0.04 mrad after environment test, the error of the line of sight between the narrow field of view and the wide field of view is less than 0.1mrad. The performance of the imager of the LWIR optical system is improved, the MRTD value is 0.07 K at 3 cyc/mrad, the NETD valueis 30 mK. The optical systems' imaging quality is perfect, it can be satisfied to the imager.