连续变焦镜头焦距输出结构的设计

根据光学设计中变倍组与补偿组的移动量与系统焦距的关系,设计了一种在变焦距镜头连续变焦时能准确输出焦距值的结构。该结构由蜗轮蜗杆驱动,以直线位移传感器为反馈元件,采用一个连接杆将直线位移传感器与变焦镜组进行固定连接来保证镜组的移动量直接反馈为位移传感器的电压值。与传统的通过齿轮传动将焦距变化反馈到旋转电位器的结构相比,该结构消除了由齿轮传动的空回、凸轮带动钉的间隙以及电位器的误差值等带来的影响。精度分析表明,采用这种高精度的直线位移传感器,加在其上的电压的变化可直接换算成焦距的变化,因此提高了焦距输出的精度。

Mechanism design of focal output for zoom lens

A mechanism structure for the focal output of a zoom lens in varifocusing process was designed based on the relation of system focus, variable magnification unit and compensation unit in the optical design. A line displacement sensor was taken as feedback, a worm wheel and a worm as drive-elements in the mechanism structure, and a joint pole was adopted to fix and join the high-precision line displacement sensor and the zoom lens, so that the motion values of zoom lens was directly feeded back to the voltage of line displacement sensor. As compared with traditional mechanism structure that the focal-length was calculated by the relation of the cam rotational angle acquired by gear-driven potentiometer, the precision was low for the last motion error of gear, clearance of cam, drive nail and the potentiometer error. The results of precision analysis show that the focal-length can be obtained immediately based on the voltage of line displacement sensor which reflectes the displaces of zoom lens, therefore the precision for focal output is improved greatly.