<title>Aspherical Surface Testing With Shearing Interferometer Using Fringe Scanning Detection Method</title>

Abstract

Described is a technique for accurately measuring the wavefront aberration of aspherical optical surfaces with a lateral shearing interferometer. A computer controlled interference phase measuring technique is employed, which provides greater accuracy and real time data analysis. Key elements of the present system are a lateral shearing interferometer with a prallel plate, a piezoelectric-driven mirror, an areal image detector, and a microcomputer system with a graphic display. The shearing interferometer gives a fringe pattern corresponding to the derivative of the wavefront, which is analyzed by the fringe scanning method. By integrating the drivative of the analyzed data, we have the wavefront aberration of the test optics over an aperture containing 32 x 32 element array. A rms accuracy of measurement is 1/32 wavelength is achieved on the evaluation of a f/4 aspherical mirror.