基于谐衍射的红外中波/长波双波段视景仿真光学系统设计

针对红外中波/长波双波段制导系统性能测试与评估的需求，设计了一套基于数字微镜器件的红外双波段视景仿真光学系统，包括投影镜头和照明系统。讨论了大出瞳距、大后工作距情况下红外双波段投影系统的像差特性及设计方法，采用反摄远结构和谐衍射面结合的方案，解决了由双波段、大出瞳距离和大后工作距带来的系统彗差、像散、畸变以及色差难以平衡的问题。采用柯勒式直接照明的方案，解决了斜入射情况下均匀照明的问题，提高了光能利用率并有效地控制了杂光的影响。最终仿真系统全视场角为5，F#为2.4，出瞳距离190 mm，出瞳直径84 mm，系统畸变小于0.1%，中波时系统奈奎斯特频率36 lp/mm下各视场调制传递函数大于0.4，长波时中间频率20 lp/mm处传递函数均大于0.38；照明均匀性高于98.5%。满足红外中波/长波双波段高质量模拟仿真的需求。

Optical design of MWIR/LWIR scene projector with hamonic diffraction element

For the requirements of performance testing and evaluation of IR guidence system which works in dual-bands of MW/LW, a DMD based dual-bands infrared scene simulation system was designed, including a projection lens and illumination optical system. The aberration characteristics and design methods of the IR dual-bands projection system with long exit pupil relief and back focal length were discussed. An inverted-telephoto structure with a harmony diffraction surface was used to solve the aberrations such as coma, astigmatism, distortion and chromatic aberration which were difficult to balance. In the design of the illumination system, directly irradiation combined with the Khler illumination principle was adopted to achieve a uniform illumination in the case of oblique incidence, also the improvement of light energy utilization and suppression of the stray light as well. The designed IR MW/LW scene simulator has a full field of view of 5, F# of 2.4, and exit pupil relief of 190 mm. The distortion of the lens is less than 0.1%. At the Nyquist frequency of 36 lp/mm, the modulation transfer function(MTF) is higher than 0.4 in the band of MWIR; at the intermediate frequency of 20 lp/mm, the MTF is higher than 0.38 in the band of LWIR, at every field of view. The relative illumination is higher than 98.5%, which meets the requirement of the scene simulation.