| With the rapid development of panoramic imaging and infrared detection technique, the high-resolution multi-band dual field imaging optical systems gradually instead of single-band single field of view and low-resolution optical systems, becoming a hot point of the military research of science and technology. Quick and timely finding the targets, tracking in real time and then precise measuring the targets have been turning into the main trend of the modern optical system development. Infrared dual-band imaging system can simultaneously acquire the target information in two bands and suppress the complex background, which can significantly reduce the false alarm rate. Dual-field two tranches of zoom optical system has two fields of view that the mode of short-focus and large field of view is used to observe and quickly search the targets; while the long-focus and small field used for target identification, tracking and collimation. Compared with continuous zoom optical system, the structure of dual-field two tranches of zoom optical system is more compact and simple, switching is more quick and efficient, which prevents losing the fast-moving targets during the process of optical path conversion.According to the above issues, this paper adopted a panoramic imaging method of multi-cameras stitching and the field of spatial interaction deployed. Compared and discussed with the two designing approaches of the four-channel infrared panoramic imaging system structure model, integrated each advantages and disadvantages, the paper chose the second designing approach of the four-channel infrared panoramic imaging system structure model that the azimuthal angle of is 360° and the top view is 122°. Each imaging channel is designed as a cooled MWIR & LWIR dual-band dual-field optical system.The configuration design of the optical system is adopted the secondary imaging structure, combined with the Gaussian theory of the zoom optical system, it calculated the initial structural parameters of the dual-field two gears of zoom optical system. The F-number of the optical system is 2, working band is MWIR 3.5～4.8 um and LWIR 7.8-9.8 um, full field of view(FOV) is 122°, the ratio of long focal length and short focal length is 5, and it can complete 122 °/44.49° dual-field transformation through the move of the zoom configuration in axial direction.By adopting the refractive/diffractive hybrid optical elements and introducing aspheric design technique, the system is made temperature compensation by the means of optical passive athermalization. The paper made a narcissus analysis for the cooled optical system and adopt the reverse optical tracing for a comprehensive analysis of narcissus effect to those optical surfaces which YNI value less than 1. The result indicates that the diffuse spots radii of system are all within a pixel size of 28 μm. At the Nyquist Frequency of 181p/mm, the modulation transfer function(MTF) of MWIR system is higher than than 0.6 at the edges of the field of view, and the MTF of LWIR system is higher than 0.4 at the same condition, which all are approaching the diffraction limit. Also, the system has almost 100% efficiency of the cold stop and a good ability of narcissus restraining. The image plane is stable and the image quality is excellent when the system works on -40℃～+60℃, which can meet the using requirement of system. |
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