Abstract

Aspherization of large, fast aspheric mirrors can be guided by an infrared interferometric version of the commonly used wire test. As in the traditional wire test, measurements are made of the intersection of the surface normals with the optical axis resulting in a determination of the longitudinal spherical aberration (and thus, the conic constant) and radius of curvature of the mirror which completely characterizes the shape of the optical surface. In the interferometric test the determination of the surface normal intersection positions are found not by observing a wire but by observing the location in the pupil of the null position of fringes in an IR interferometer having a spherical reference wavefront. Since a 10.6p wavelength is used, the test can be performed on a ground surface. This test was used to guide the aspherization of the 3.5 m, f/1.75 WIYN primary mirror.

© 1994 Optical Society of America