Abstract

Itek has developed methods to generate surfaces to high tolerances using standard numerically controlled five-axis machine tool with 0.005 in. positioning tolerance and 0.0002 in. repeatability. In this approach, the five-axis are used to keep the rotational axis of a diamond cup wheel normal to the surface at all points on the surface. This results in the entire circumference of the cup wheel performing the cutting increasing the cutting efficiencies. The method is applicable to both on and off axis spherical and aspherical surfaces, and is limited only by the size of the machine tool. This is accomplished in a two-stage process. In the first stage, the surface is cut without regards for machine-induced errors. The surface is measured on the Itek profilometer to obtain a surface normal error map. A second surfacing control file is created using this map and the surface is recut. This method has resulted in a 1.5 m parabola with a surface of 3.8-µm RMS and 2.3 m parabola with a 5-µm RMS.

© 1990 Optical Society of America