A new manufacturing system for free form and large optics

Abstract

We report a new manufacturing system for free-form large optics. The system enables both polishing and test on an optical surface by a robot arm. The robot arm drags sensors on the surface for measuring cross sections over the test surface. A new algorithm stitches the cross-sectional data to the two dimensional surface shape with improving the accuracy simultaneously. We used the system for an aspheric convex mirror (1 m in diameter) and a flat mirror (major axis of 1m); they are secondary and tertiary mirrors of Seimei telescope, respectively. The system took about one hour to obtain about 100 cross sections over the whole area of the mirror, and showed repeatability of better than 10 nm RMS. We installed the mirrors to Seimei without interferometric test. We confirmed performance of the system by obtaining a Hartmann constant of 0.26 arcsecond as combination of a M1 segment, secondary, and tertiary mirrors with observing natural stars.