确定性抛光非球面光学元件残余误差的评价方法

Abstract

研究非球面光学元件确定性抛光中表面残余误差的评价方法。对两种非球面残余误差的评价方法,分别为轴向误差法和法向误差法,进行理论研究。指出非球面的残余误差理论上应使用法向误差法来评价,并提出一种基于轴向残余误差求解法向残余误差的方法,继而对二者进行比较发现两者存在一定的偏差,并且差值从非球面的中心向边缘方向逐渐增大。以气囊抛光和数控小磨头抛光为例,通过试验表明使用轴向误差法评价残余误差,进行确定性抛光引入了不同程度的加工误差,引入的加工误差的大小与非球面光学元件的口径和顶点曲率半径的比值(即“相对孔径“)成正相关,故对于相对孔径较小的非球面光学元件在确定性抛光中可使用轴向误差法替代法向误差法作为残余误差的评价方法,反之,则应使用法向误差法。

Residual error evaluation method for deterministic polishing of aspheric optics is studied.Two residual error evaluation methods, which are axis-direction error method and normal error method respectively, are researched theoretically.It's inferred that the residual error of aspheric surface should be evaluated by normal error method.A new approach is proposed to calculate normal direction residual error on the basis of the axis-direction residual error of the aspheric surface.There exists difference between these two kinds of error which increases from the center of the aspheric optic to the edge through the comparison of them.Taking bonnet polishing and numerical controlled small tool polishing as examples, experiments are made to quantitatively prove that using axis-direction error method to evaluate residual error in deterministic polishing would introduce different degrees of processing error.It's found that the processing error is positively correlated with the relative aperture of aspheric optics, which is the ratio of the optic's aperture and vertex's curvature radius.Therefore, it is recommended to use axis-direction error method instead of normal error method as the evaluation method of the residual error during deterministic polishing aspheric optics with relatively small relative aperture; the opposite is the other way around.