目前的焦距仪为了增大测量范围, 会配备一组测量镜头。在测量不同范围焦距时需要进行更换, 过程繁杂, 影响工作效率。解决这一问题, 设计一个五档变倍的测量镜头, 通过了变焦与变物距两个方法实现变倍, 用档位之间的切换代替目前的更换测量镜头提升工作效率。设计完成后, 放大率变化为8.0~0.16X, 物距变化为20~1000mm, 测量范围: (-1000mm,-5mm) U (5mm,1000mm)。通过ZEMAX模拟仿真实验表明: 设计得光学系统测量范围大, 各个变倍位置成像质量良好, MTF曲线接近衍射极限, 可以替代原有的测量镜头组。

The focometer, as a traditional optical instrument for measuring focal length, is equipped with a set of fixed focus measuring lenses. When measuring focal distances of different ranges, the focal length instrument needs to replace different measuring lenses. It is complicated and inefficient. A five gears zoom lens is designed to instead of the set of fixed focus measuring lenses. The zoom of magnificent range from 8.0X to 0.16X. And the zoom of work distance range from 20mm to 2000mm. The range of focal length from this focometer is(-1000mm,-5mm)U(5mm,1000mm). The image quality of five gears have reached the requirements, through the analysis of the measurement results. It can be concluded that the five gears zoom lens meets the design requirements.