针对高分辨率 640×512元非制冷探测器，设计了一款 6×长波红外连续变焦光学系统。该系统由 6片透镜构成，工作波长为 8~12 μm，F数为 1~1.1。根据变焦光学系统设计理论，确定了系统的机械补偿式变焦结构并构建了初始结构; 对该系统的光学结构参数及凸轮变焦曲线进行了设计和优化。像质评价结果表明该系统在 20 ~120 mm焦距范围上实现了连续平滑变焦; 在 30 lp/mm空间频率处，全焦距范围调制传递函数值大于 0.45，接近衍射极限; 全焦距范围各视场弥散斑均方根半径小于 6.3 μm，远小于像元尺寸 17 μm。实验证明该系统具有高分辨率、高变倍比、大光圈、大视场范围的特点，且像面稳定，变焦平滑，结构紧凑合理，成本相对较低。

A long-wave infrared continuous 6× zoom optical system with 640×512 uncooled infrared thermal detector is designed and described. It contains 6 lenses and works at 8~12μm wavelength with the F# of 1~1.1. Based on the theory of zoom optical lenses design, a mechanical compensation structure is determined and the initial structure parameters are calculated. Moreover, the optical system parameters and zoom curves are designed and optimized. The image quality assessment shows that system zooms continuously and smoothly in all 20~120 mm focus lengthens range. The Modulation Transfer Function (MTF) values at 30 lp/mm are all above 0.45 and the spot diagrams’ RMS radius are all less than 6.3 μm which is much smaller than the detector pixel size 17 μm in all focus lengths range. The experiment proves that this zoom system has the merits of high resolution, high zoom ratio, big aperture, big field range, and has steady image plane and zooms smoothly with compact structures and low cost.