Design of Airborne Miniaturized Middle Wavelength Infrared Continuous Zoom Optical System
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摘要: 为适应机载光电系统对红外热像仪光学系统小型化、轻量化的要求,采用前端无焦扩展倍镜与后端连续变焦光学系统组合的方式,实现了30~660 mm的22倍连续变焦光学系统。该系统的光学总长为244 mm,总长/最大焦距比为0.37,系统具有光学总长小、变倍比大的特点,适用于远距离目标探测的大型机载光电吊舱系统中。将前端无焦扩展倍镜去掉后,后端连续变焦光学系统可以实现15~330 mm的22倍连续变焦光学系统,该系统的光学总长为138 mm,总长/最大焦距比为0.42,可作为独立的连续变焦系统应用于近距离目标探测的中小型机载光电吊舱系统中。设计结果显示,该系统在两种状态下均成像良好,在探测器对应的特征频率33 1p/mm处,中心视场的MTF值均在0.3附近,接近衍射极限,0.7视场的MTF值均在0.2附近,边缘视场的MTF均在0.15附近,能够满足应用需求。Abstract: To satisfy the requirements of an airborne electro-optical system for miniaturized and lightweight optical system of an infrared thermograph, a 22× continuous zoom optical system of 30–660 mm was realized by combining front-end afocal extender and back-end continuous zoom optical system. The total optical length of the system was 244 mm, and the total length/maximum focal length ratio was 0.37. The system had a small optical length and large zoom ratio, which makes the system suitable for large airborne electro-optical pod systems for long-distance detection. Upon removing the front afocal extender, the back-end system could achieve a 22× continuous zoom optical system of 15 to 330 mm. The total optical length of the system was 138 mm, and the total length/maximum focal length ratio was 0.42. The system can be used as a continuous zoom optical system in small-and medium-sized airborne electro-optical pod systems for close-range target detection. The design results exhibit that the system can capture images effectively in both states: at the characteristic frequency of 33 lp/mm corresponding to the detector, all the MTF values of the central field view were approximately 0.3, close to the diffraction limit, all the MTF values of the 0.7 field view were approximately 0.2, and all the MTF values of the edge field view were approximately 0.15, which satisfies the application requirements.
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Key words:
- miniaturization /
- optical design /
- continuous zoom system /
- middle wavelength infrared
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表 1 光学系统技术指标
Table 1. Optical design parameters
Parameter Value Detector size 640×512(cooled) Pixel size 15 μm Wavelength 3.7 to 4.8 μm F number 4 Focal length 15 to 330 mm(without extender) 30 to 660 mm(with extender) Total length 138 mm(without extender) 244 mm (with extender) -
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