Research On Night-vision System Based On Chalcogenide Glass

The illumination system of cars is limited when they run at night and the driver’s stadia is short whichshorten the driver’s reaction time and significantly increase the danger of driving. Therefore, the development ofnew type infrared night-vision system is one of the focuses of improving vehicle safety. In this paper, we take thelimitations of night-vision system into consideration such as complex structure and expensive price, the design oflens structure, material selection and other aspects are analyzed in detail, and the solutions are proposed. At last, aseries of athermal infrared night-vision systems are designed which possess good thermal stability, stronganti-interference ability and high cost-performance. The main contents of this thesis are as followings:(1)The optical and thermal characteristics of chalcogenide glass were discussed, which included the infraredtransmission performance, optical homogeneity, thermal stability and the MTF. The results indicated that thechalcogenide glass had a good transmittance in whole infrared band and the transmittance had reached60%. TheLSF was an ideal Gaussian distribution, the results of MTF test also indicated that the samples were transparentuniform inside without small particles. In addition, the refractive index of thermal coefficient was smaller whichensured the thermal stability.(2)The athermal characteristics of refractive optical elements were analyzed. The thermal property anddispersion property of refractive optical element were described. The temperature effect of the refractive opticalelement was discussed. The results showed that the thermal expansion coefficient of refractive optical elementwas determined by the refractive temperature index and thermal expansion coefficient of the optical materials, andit was usually negative. In addition, the dispersion coefficient was determined by the refractive index, and it wasgenerally be positive.(3) The athermal characteristics of diffractive optical elements had been discussed. The thermal property,dispersion property and the diffraction efficiency of diffractive optical element were analyzed. The results showedthat the thermal expansion coefficient of diffractive optical element was determined by the thermal expansioncoefficient of optical materials, and it was constantly positive. In addition, the dispersion coefficient wasdetermined by the waveband, and it was negative. All these properties were opposite to the refractive opticalelements.(4)The performance of infrared night-vision optical system was analyzed. We designed a series of infraredoptical system by an optical design software Zemax. The image quality was analyzed in different aspects. Theresults indicated that the traditional refractive optical system had some restrictions in athermalization andachromatism which needed various material combinations to guarantee the MTF closed to the diffraction limit in awide temperature range. And the system was a little complex and expensive. The image quality was good and thestructure was brief if used diffractive optical element to constitute a hybrid system. In general, it only needed threelenses or even one lens to guarantee the image quality of system in a wide temperature range.