Removing Mid-Spatial Frequency (MSF) Errors Using Stress-Polishing

After diamond-turning aluminum aspheric mirrors, we will develop a stressed polishing process to improve surface figure and finish.

This IRAD proposes to evaluate how stress polishing can be used to extend the application of super-polishing to fast aspheres and freeforms, removing sub-aperture MSF errors, such as tool marks, from diamond-turned aluminum optics.  It will leverage an old technique for manufacturing aspheres—stress polishing with a large tool. The aspheric surface will be generated using small tool manufacturing techniques. After the asphere is generated, a mechanical load will be placed onto the optic to deform the asphere into a sphere, using an interferometer to fine tune the deformation.  After the asphere is deformed into a sphere, the sub-aperture tool marks can be removed by post-polishing using the Goddard super-polishing process, a process limited to spheres and flats due to the fact that it requires the use of a tight fitting large polishing tool.