根据坦克目标搜索/跟踪系统的要求,设计了工作于8-12 μm波段折/衍射混合红外连续变焦距光学系统。该系统解决了传统系统不能同时满足长焦距、大相对孔径、高变倍比、高成像质量和系统结构简单的缺陷,使设计的系统相对孔径大,F数为0.9,变焦倍率为11×,系统在长焦距时,可识别1500 m远的坦克目标。变焦系统仅用7片锗透镜,通过引入二元面和非球面校正系统色差和轴外像差,在空间频率为17 lp/mm处,全焦距范围内调制传递函数(MTF)值均在0.64以上,接近衍射极限;系统在接收半径为17.5 μm的探测器敏感元内,能量集中度大于82%,表明系统具有良好的成像质量,满足坦克目标搜索识别系统的总体要求。

8-12 μm infrared (IR) hybrid refractive/diffractive continuous zoom lenses is designed for the needs of target detecting/tracking system. The defects of conventional systems,such as being insufficient for achieving long focal length,large relative aperture,big zoom ratio,high imaging quality and simple structure,are solved in this system,which has the properities of large relative aperture,F=0.9,zoom ratio 11×,discernment with long focal lengths for tanks at about 1500 m distance. The optical system composes of seven pieces of Germanium lens. To correct chromatic and off axis aberrations,the system applies diffractive optical element (DOE) and aspherical surface. The modulation transfer function (MTF) is above 0.64 in all focal lengths at the spatial frequency of 17 lp/mm,which approaches the diffraction limit. The energy concentration ratio is greater than 82% in the 17.5 μm radius of sensing pixel. It shows that the optical system has good imaging quality and meets the needs of general requirements for the target detecting/tracking system.