设计了一种应用于特定机载平台上的变焦距镜头。为了减小轴向尺寸，后镜组进行了2次折反，光学系统的轴向尺寸96 mm，满足了空间的要求。镜头变倍比为20倍，焦距6～120 mm,相对孔径1/5.6。采用了机械补偿方法和滑架导向机构。该镜头轴向尺寸小、精度高、变焦过程光轴晃动小。通过试验,检测出变焦过程光轴晃动不大于34″。通过飞行试验实现了短焦距搜索目标、长焦距跟踪目标的功能，并且变焦快速，像面稳定，视频跟踪图像清晰。

A zoom lens is designed for a specific airborne platform. In order to decrease the axial dimensions, the rear-view mirror group is folded twice. It meets the space requirements since the axial dimension of the optical system is 96 mm. The zoom ratio of lens is 20, and the focal length is 6~120 mm, and the relative aperture is 1/5.6. The lens uses a method of mechanical compensation and a guiding mechanism of carriage. The lens has a small axial size, with high accuracy and a small optical axis shaking. Through the test, the optical axis shaking is found to be no more than 34″ in the process of continuous zoom. Through flight test, it is proved that the zoom lens can search objectives in the short focal length and track the target in the long focal length. In addition, the zoom lens can quickly change the focal length, the obtained image is stable, and the tracking video image is clear.