摆臂式非球面轮廓仪的原理与试验

介绍了一种新颖的非球面轮廓仪的测量原理和测量试验,它通过测量非球面与某一参考球面之间的偏离量来唯一确定非球面的面形误差,通过调整测量臂长以及回转轴线与光轴之间的夹角实现对不同非球面的测量。系统主要由高精度两维转台,高刚度测量臂,四自由度微调系统和高精度扫描测量传感器组成,并分别在VC++6.0与MATLAB平台上开发了测控软件以及数据处理软件。该测量方法的优点是测量所需传感器量程小,测量运动为一个简单的回转运动;缺点是测量调整自由度多,校准困难。建立了测量系统的数学模型,通过测量数据与名义面形之间的非线性优化,在获得面形误差的同时获得了非球面面形参数误差。通过测量多条截线实现了对非球面面形的全口径检测。最后对直径200 mm,顶点曲率半径1 400 mm的凹形抛物面镜进行了测量,结果表明,系统重复精度优于0.8 μm,精度优于1 μm。

Principle and experiments of swing-arm profilometer

The geometric principle of a swing-arm profilometer as a novel method to measure aspherics are introduced. The surface error of an asphere is obtained by testing its relative departure from some reference sphere,and different reference spheres are realized by adjustment of the length of the swing-arm and the angle between rotary axis and optical axis. A measuring set-up is built based on this principle, which consists of an ultra-precise 2-axes rotating-table, a high stiffness, lightweighted measurement arm, a 4-DOF stage and a scanning sensor,the testing software and data-processing software are programmed with the VC++6.0 and Matlab platform, respectively. The profilometer has advantages in shorter measuring range for a sensor and simple rotary measuring motion,and the disadvantages in complicated calibration and large DOF adjustment. A mathematic model is established to gain the error of conic aspheric parameters and surface error based on the nonlinear optimization of measured data and nominal figure,and the full-apearture of a 3D asphere is tested by measuring several transversals. Finally,a grinded paraboloid (D=200 mm,R=1 400 mm) is tested, results indicate that the system has a good repeatability (<0.8 μm) and accuracy (<1 μm).