变焦距镜头凸轮曲线形式的选择

在变焦镜头设计的最后阶段需要进行凸轮曲线的设计,为了平衡成像倍率变化的均匀性与凸轮转角,需要选择合适的凸轮曲线形式,要求建立成像倍率M与凸轮转角θ之间的某种函数关系。根据凸轮曲线所要满足的实际边界条件和函数连续性,建立M与θ几种常见的函数关系,利用Matlab对设计实例进行仿真。结果表明:建立的成像倍率M和凸轮转角θ的幂函数关系及压力升角都不超过允许值时,变倍倍率变化均衡性最好,倍率变化曲线平滑,且无凸轮拐点。该方法可以方便设计人员针对不同设计要求改变凸轮曲线形状,找到最佳变倍凸轮曲线。

Selection of cam curve for zoom lens

In the final course of zoom lens design, the cam curves have to be designed. In addition, in order to balance the uniformity between imaging magnification change and cam corner, the appropriate cam curve should be chosen. So it is important to establish the relationships between imaging magnification M and cam corner θ. Based on the boundary conditions and the continuity of the function whcih cam curves have to meet, some functions are established and discussed. Some design examples were simulated with Matlab, which indicates that the exponential function fits well with M and θ. Besides, the pressure angle is less than the permitted value and the uniformity of cam curves is better and smooth without cam inflexions. Compared with other solutions used before, this method helps the designer to modify the cam curves effectively and find the best cam curves of the zoom lens.