Study On The System Of Visible And Infrared Target Contrast Characteristic Measurement

In recent years,with the development of target detection technology,the contrast measurement of target and background is widely concerned by many countries,using visible light and infrared to detect target on the ground thus gettinthe contrast between target and background which is a important method to get information in battle.In this papar,the contrast measurement of target and background is deeply analysed,in the visible range,using the illumination on the CCD to define the contrast,in the infrared range,using the brightness to define the contrast,in traditional,the choose of measurement system is single,it has limitation to get target image from one wave range,this paper concentrate on image measurement system,design dual waveband optical system which can get visible and infrared image simultaneous that can improve the accuracy and detection probability,meanwhile,it has advantages to image fusion.By comparing the dual-band design experience at home and abroad,the research of visible/ infrared dual-band optical system design method deeply,design a set of visible / infrared dual-band common aperture optical system,the visible light wavelength is 0.38μm ~0.76μm,infrared is 7.9 μm ~9.7μm,analysis and comparison the general structure design in dual-band optical system,using refractive-diffractive hybrid structure,the optical system adopts prism beam splitter,respectively by the respective imaging detector.The infrared light path by using the refrigeration type infrared detector to receive,for the realization of the 100% cold shield efficiency and reduce the lens diameter,using secondary imaging structure.According to the selection of the system and the parameters of the detector,the main parameters of the optical system of the visible light channel and the infrared channel are calculated respectively.The design parameters are as follows: The focal length of the visiblelight path is 100 mm,and the relative aperture is 1:4.The focal length of the long wave infrared light path is 100 mm,and the relative aperture is 1:2.In order to make the imaging quality of the optical system at the working temperature range of-40℃~+60℃,the image quality meets the requirements of the image quality.The optical passive athermalization design of the system is used.The total field of view of the two band optical path at the Nyquist frequency is more than0.4,and the system meets the requirements of the athermal design.Finally,the narcissus of this system is analyzed by using YNI value and reverse ray tracing.