利用曲面计算全息图进行非球面检测

Aspheric surface testing with CGH on curved surface

研究了利用曲面计算全息图进行非球面检测。分析了曲面计算全息图的衍射特性,给出了曲面计算全息图与传统检测方法相结合检测凹非球面和凸非球面的原理及特点,并进行了具体设计。利用激光直接写入设备,在口径为110mm、曲率半径为504mm的曲面基底上制作出了计算全息图,并对金刚石车床车削的凸面非球面进行了检测。利用两步测量法解决了凸非球面的中心部位难以检测的难题,同时利用旋转相减法消除了调节误差,非球面的面形精度为234nm(P V),与金刚石车床的精度相符。

A research on aspheric surface testing by using a computer-generated hologram (CGH) on curved surface is presented. The diffractive property of CGH on curved surface is briefly analyzed, and the principle, property and design examples are given for testing concave and convex aspheric surface, respectively. Compared with the traditional testing methods, this method not only simplifies the optical system, but also decreases the fabrication accuracy of the computer-generated hologram. A CGH on a concave surface with diameter of 110 mm and radius curvature of 504 mm was fabricated by using a laser direct writer, and used to test a convex aspheric surface produced by diamond-turning successfully. Two methods were developed, one that utilizes the strategy in measuring twice can overcome the difficulty in measuring the center areas of the aspheric surface under test, the other that utilizes the strategy of rotating and subtracting can eliminate adjustment errors. We have successfully measured a 110 mm diameter convex surface with the error of 234 nm P-V, which well agree with the fabrication accuracy of the surface produced by diamond-turning.