Aspheric Measurement Using Phase-Shifting Interferometry

Abstract

Aspheric optical surfaces are difficult to test because these surfaces generally depart too much from a sphere for a conventional interferometer to resolve the interference fringes and allow reconstruction of the test surface. A large number of detector points can provide a brute force approach to measuring these surfaces. More elegant techniques such as using multiple wavelengths or a priori information about the wavefront can enable wavefront reconstruction.^1-3 Once the necessary information has been detected, corrections are needed to account for the propagation of aberrations through the optical system from the test surface to the detector. Combining fringe analysis with lens design software will allow this correction to take place. This paper examines these techniques, and compares them to currently utilized techniques.