Design of Cooled Medium/Long Wave Infrared Dual-band Integrated Reflective Optical System
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摘要: 为避免透射式系统存在的色差问题,采用离轴反射式光学系统,在三镜后加分色片,分别成像到中波探测器及长波探测器的焦面上,实现对中波红外和长波红外两个谱段信息的同时成像。该一体化系统由3个离轴反射镜和一个分色片构成,为校正系统像差,三镜采用XY多项式曲面。采用二次成像结构形式,具有100%冷光阑效率。系统F数为2.67,视场角11.4°×1.8°,工作波段为中波3.55~3.93 μm,长波10.3~12.5 μm。中波红外系统MTF平均值大于0.5@25 lp/mm,长波红外系统MTF平均值大于0.4@12.5 lp/mm,采用光学被动式消热差法对光学系统进行温度补偿,温度适应范围为-40℃~+60℃。Abstract: A three-mirror anastigmatic(TMA) optical system was adopted to prevent chromatic aberration of the refractive system by adding a dichroic beam splitter behind the tertiary mirror to simultaneously implement the image to the MWIR and LWIR detectors. The integrated system included three off-axis mirrors and a dichroic beams plitter. The surface of the tertiary mirror was an XY polynomial freeform surface that could correct system aberrations. The structure of the system was re-imaged with 100% cold shield efficiency. The F-number was 2.67, the full field of view(FOV) was 11.4°×1.8°, the working band is 3.55-3.93 μm for the MWIR channel and 10.3-12.5 μm for the LWIR channel. The modulation transfer function (MTF) average values of MWIR were greater than 0.5 at 25 lp/mm, and the MTF average values of the LWIR were greater than 0.4 at 12.5 lp/mm. The temperature compensation of the optical system was optical passive athermalization. The temperature range was -40℃ to +60℃.
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表 1 光学系统设计指标
Table 1. Optical system design indices
Parameter MWIR LWIR Wavelength/μm 3.55-3.93 10.3-12.5 Focal length/mm 400 400 F/# 2.67 2.67 FOV/° 11.4×1.8 11.4×1.8 MTF ≥0.5@25lp/mm ≥0.4@12.5lp/mm Distortion ≤2% ≤2% Cold stop efficiency ≥98% ≥98% -
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