红外系统对目标进行搜索与探测时，对连续变焦光学系统的需求日益增强，其中一个措施就是改变两个或两个以上透镜在光学系统中的位置，从而改变光学系统的焦距。根据某中波红外光学系统的设计特点，对连续变焦机构的导向机构和凸轮机构进行了详细分析,给出了设计要点和设计结果。试验结果表明：该机构运行平稳、可靠、精度高，光学系统的成像质量高。

The continuous zooming optical system has become more and more important for an infrared system in target searching and detecting.One method is changing two or more lens's location in order to change focal length in optical system.Based on the optic design features of medium wave infrared system the guide mechanism and cam mechanism of the continuous zooming mechanism are discussed in detail.The key points and result of the design are given.The test result indicates that the mechanism can operate smoothly and reliably with higher precision，and the image quality of optical system is fine.