制冷型中/长红外双波段双视场全景光学系统设计

Design of cold MWIR/LWIR infrared dual-band/dual-field panoramic optical system

为了同时探测中波红外和长波红外两个波段信息,实现两个不同视场快速切换,采用空间多镜头图像拼接全景成像法,设计了四通道制冷型中/长红外双波段双视场全景成像光学系统。该全景系统由周视方向3个互成120°的红外物镜和顶视方向一个红外物镜构成,每一个成像通道光学系统采用二次成像结构。F数为2,工作波段为中波3.5μm^4.8μm、长波7.8μm^9.8μm,双视场两档焦距之比为5,通过轴向移动变倍组可以完成122°/44.49°双视场转换。利用折/衍混合器件及非球面设计技术,采用光学被动式消热差法对光学系统进行了温度补偿。设计结果表明,该双视场光学系统具有100%冷光阑效率和良好的冷反射抑制能力。在-40℃^+60℃范围内,在奈奎斯特频率18lp/mm位置处,中波红外系统MTF值均大于0.5,长波红外系统MTF值均大于0.3。

In order to identify that two bands information of the medium wavelength infrared radiation （MWIR） and the long wavelength infrared radiation（LWIR）, realize the fast switch of two different fields of view（FOV）, and further enhance the efficiency and range of existing systems to detect, a four-channel cooled infrared dual-band dual-field panoramic imaging optical system was designed by using the method of spatial multi-camera image mosaic panoramic imaging. The panoramic system is consisted of three infrared lenses with mutual intersection angle of 120; in circular-viewing direction and one infrared lens in top view direction, each optical system of imaging channel is designed to be the double imaging configuration. The F-number is 2, the working band is MWIR 3.5 μm;4.8 btm and LWIR 7.8 μm;9.8μm, the full field of view（FOV） is 122; , the ratio of long focal length to short focal length is 5, and it can complete 122 ;/44.49 ; dual-field transformation through the moving of the zoom configuration in axial direction. By adopting the refractive /diffractive hybrid optical elements and introducing aspheric design technique, the system was made temperature compensation by the means of optical passive athermalization. The result indicates that the system has almost 100% efficiency of the cold stop and a good ability of narcissus restraining. At the Nyquist frequency of 18 lp/mm, the modulation transfer function （MTF） values of LWlR optical system are all greater than 0.3 , and that of MWlR are all greater than 0.5. The image plane is stable and the image quality is excellent when the system works on -40 ℃-＋ 60℃.