Design Of An Athermalized MWIR And LWIR Dual-band Optical System

Based on the MWIR and LWIR optical systems can respectively image high temperature and normal temperature objects, a MWIR and LWIR dual-band optical system could effectively improve target detection and recognition ability of IR imagers. As the infrared materials are sensitive to the temperature, the change of the temperature often degrades the image quality. To the imaging characteristic of MWIR and LWIR and the thermal aberration caused by temperature variation, study on an athermalized MWIR and LWIR dual-band optical system is carried out in this thesis.In the first chapter, the significance of this issue is introduced and the development of IR dual-band optical systems is reviewed.In the second chapter, at first, the performance of the infrared detection is introduced. Then, combined with using two-color detection and based on the performance requirement of our optical system, the structural type suitable for its dual-band IR optical system is analyzed and selected. At last, the Cooke structural type is selected.In the third chapter, the design theory of the dual-band IR optical system is given. First, the necessity of its achromatic aberration is introduced. Second, the effect of environmental temperature fluctuation on the single thin lens is researched, educing the necessity of athermalization. Third, compared with various athermalization methods optical passive method is preferred. Finally, the initial layout of the optical system is calculated using the primary aberration theory.In the fourth chapter, an athermalized MWIR and LWIR dual-band optical system is designed. Its optimization method, optimized result and imaging quality are given. The designed system has the advantages of structural compactness, large back focal length and 100% cold shield efficiency. It is not only used combined with two-color detection, but also imaging in MWIR and LWIR separately by inserting a beam splitter in the front of image plane.In the fifth chapter, based on the designed athermalized dual-band IR optical system, the principle of its tolerance analysis and distributing is introduced. Its tolerance is distributed optimally for facilitating its fabrication.In the last chapter, the work and the innovation points are concluded and further researches prospected.