基于像元大小为25 m 的384×288非制冷型凝视焦平面阵列探测器，设计了一种20倍非制冷长波红外连续变焦光学系统。该系统的工作波段为8～12 m，F数为1.3，具有相对孔径大、变倍比大和变焦凸轮曲线平滑等优点。该系统共有7片镜片，使用2种材料组组合，其中多数透镜使用常用的锗材料，以减少使用昂贵材料和便于加工。通过使用1片衍射面元件和2片非球面元件实现了紧凑的结构。该系统的奈奎斯特空间频率为20 lp/mm，短焦、长焦的调制传递函数(Modulation Transfer Function, MTF)大于0.4，中焦MTF大于0.58。 MTF值体现出该系统具有极好的像质特征。

On the basis of a 384×288 uncooled staring focal plane array detector with pixel size of 25 m, a 20-fold uncooled long wavelength infrared continuous zoom optical system is designed. The operation waveband of the system is 8～12m and its F number is 1.3. It has the advantages of larger relative aperture, higher zoom ratio and smooth zoom path etc. The system consists of seven lenses which are made from a combination of two kinds of materials. Most of the lenses are made from common germanium material so as to reduce the use of expensive materials and be easy for processing. By using one diffraction optical element and two aspheric elements, a compact structure of the system is realized. The system has its Nyquist spatial frequency of 20 lp/mm, Modulation Transfer Function (MTF) greater than 0.4 for short focus and long focus and MTF greater than 0.58 for middle focus. These MTF values show that the system has excellent image quality.