Research On Rotational Absolute Testing Of The Optical Surface

Due to the rapid development of science, the requirement on testing accuracy ofoptical surface becomes higher and higher, and rms of figure error is demanded tonanometer even sub-nanometer. As a high-precision technology, absolute testing cancancel out reference surface by multiple measurements, and obtain the absoluteinformation of the tested surface.This article focuses on rotational absolute testing. Firstly several rotationalalgorithms, such as single rotation, rotation averaging and extended averagingmethod are introduced and their applicability is analyzed. A compensation methodbased on rotation-averaging needs a different rotation measurement besides Nequally spaced azimuthal measurements. The losing surface of rotation-averagingmethod can be obtained with the additional measurement data and Zernikepolynomial fitting. The theoretical formulas are derived and the validity ofcompensation method is simulated. The impact of additional rotation angle onalgorithm accuracy is presented. The experimental result is consistent withsimulation very well. It is proved that the compensation method can compensate thelosing surface effectively with an appropriate rotation angle and improve themeasurement accuracy.Based on single-rotation method, this article proposes an algorithm believed tobe new for interferometric measurements of rotationally asymmetric surface deviation of optics. This method tests and calculates each angular surface bychoosing specified optimal rotation angles, which can guarantee the results have alowest error. The entire figure can be obtained by superimposing these sub-surfaces.Systematic simulation and experiment studies for verifying the proposed algorithmare presented. To the single-rotation method, its accuracy is related with rotationangle in large extent, so the instability can’t always guarantee a high precision. Onthe contrary, just with several measurements, the accuracy of the proposed method ishigher than single-rotation algorithm and almost comparable to therotation-averaging algorithm. So the new algorithm can achieve a balance betweenthe efficiency and accuracy.