Measurement of the surface form error of a spherical surface with a wedge phase shifting Fizeau interferometer

Abstract

A new technique for the measurement of surface form error of a test spherical surface with respect to a reference spherical surface, using wedge phase shifting Fizeau interferometer, is presented. A two stage measurement method is discussed. The individual surface form error of the test and reference spherical surfaces along with the residual wave front aberration introduced by the common optical elements in the Fizeau cavity are measured with respect to a plane reference surface using phase shifting interferometry. Finally, data subtraction is used to eliminate the effect of the residual wave front aberration introduced by common optical elements and thereby transforming the result as the surface form error of the test spherical surface with respect to the reference spherical surface. Results obtained for a test spherical surface is presented.