Wavefront testing of pinhole based on point diffraction interferometer

Abstract

To overcome the accuracy limitation due to the aberration of reference wavefront in the interferometer testing, the point diffraction interferometer (PDI) uses the pinhole to create an ideal diffraction sphere wavefront as the reference wavefront. Because the perfect pinhole is hard to manufacture, then the imperfect pinhole will cause the wavefront errors which will influence the test accuracy. In this paper we use the absolute testing method to test the wave front of the pinhole. Then the testing accuracy of point diffraction interferometer can be improved by subtracting the error of the pinhole. In this paper a Phase-shifting point diffraction interferometer system is designed to testing the pinhole. We use three pinholes to test each other. According the algorithm of the absolute testing method, we can calculate the wavefront error of the pinhole. Then the testing accuracy of point diffraction interferometer can be improved by subtracting the error of the pinhole.