针对致冷型中波红外640×512凝视型焦平面探测器, 设计了一个30×连续变焦光学系统。介绍了由无后固定组的变焦物镜组和中继透镜组组成的连续变焦系统的设计思路, 不仅给出了系统在短焦、中焦、长焦3个位置的像质情况, 还分析了反映全焦距范围内像质的离焦量和畸变。实验结果表明: 该系统工作波段3.7 μm～4.8 μm, 可以实现18 mm～540 mm连续变焦, 全焦距范围内的离焦量都在焦深以内, 长焦段最大畸变接近于0, 短焦段最大畸变小于3%。该系统具有大变倍比、结构紧凑、变焦轨迹平滑、变焦行程短等优点, 可用于红外光电探测和跟踪系统。

For the cooled 640×512 detector with staring focal plane array, a mid-wave infrared (MWIR) continuous zoom optical system with 30× zoom range was presented .The design idea of the continuous zoom system consisting of the zoom objective lens group and the relay lens group without the rear fixed group was introduced. The image quality of the system at three positions of short effective focal length(EFL), middle EFL and long EFL is given; moreover,the amount of defocus and the distortion of image quality reflected in the full focal length range was analyzed. The experiment results indicate that the optical system with 3.7 μm～4.8 μm working waveband can realize 18 mm ～540 mm continuous zoom,the defocus amount of the full focal length is less than the depth of focus, the maximum distortion of the long EFL area is close to 0, and that of the middle EFL is less than 3%. It has the advantages of large zoom range, simple structure, short zoom path, and smooth zoom locus,which can be used for infrared optical observation and tracking system.