高变倍比红外变焦距光学系统设计

 采用长波160×120元非制冷焦平面阵列探测器，设计了工作于8μm～12μm波段折射式红外连续变焦光学系统，该系统具有大相对孔径，F数为1.2，变倍比10×，高成像质量等特点。系统使用锗和氯化钾两种普通红外材料，通过引入非球面校正系统轴外像差和高级像差，在中焦时采用平滑换根快速提高变倍比。系统在空间频率17lp/mm处，全焦距范围内调制传递函数（MTF）均在0.55以上，接近衍射极限；系统在接收半径17μm的探测器敏感元内，能量集中度大于72%，表明该系统具有良好的成像质量。

Design of high zoom ratio thermal infrared zoom optical system

A refractive infrared zoom optical system working in (8～12)μm is designed, based on long-wave uncooled thermal IR focal plane arrays (160 pixel×120 pixel) detector. The system has characteristics of large relative aperture, F#=1.2, high zoom ratio and high imaging quality. Two common infrared materials of Ge and KCl are used in this optical system. The off axis aberration and higher order aberration of the system are corrected by introducing an aspheric surface into the system, and the zoom ratio is rapidly improved by solving the compensated curves at the middle-focus length. The modulation transfer function (MTF) is above 0.55 within the whole focal range at the spatial frequency of 17lp/mm and approaches the diffraction limit. The energy concentration ratio is greater than 72% within the sensing element of the detector whose receiving radius is 17.5μm. The above mentioned parameters show that the optical system has good imaging quality.