Advanced optical systems, currently under consideration, propose the use of lightweight, segmented, long radii elements. Reaction-bonded silicon carbide (RB SiC) is quickly becoming a contender in the materials market for these large, lightweight mirrors due, in part, to its relatively low thermal expansion and high stiffness to weight ratio. The RB SiC manufacturing processes can be considered advanced in comparison to the polishing and finishing processes on bare RB SiC, or on clad RB SiC substrates. In an effort to improve the polishing and finishing techniques, Eastman Kodak Company has investigated a polishing process for physical vapor deposited silicon (PVD Si) coated RB SiC optics and has demonstrated this process on a lightweight, concave, PVD Si-coated RB SiC hexagonal optic. This discussion includes the modification and redesign of an existing conventional planetary table, durability test results on the PVD Si/RB SiC coating bond, process approach and results for the hexagonal demonstration piece, and the thermal stability analysis of the hexagonal mirror upon completion of polishing and ion figuring the front surface of the mirror.

Date Published: 23 October 1995
PDF: 12 pages
Proc. SPIE 2543, Silicon Carbide Materials for Optics and Precision Structures, (23 October 1995); doi: 10.1117/12.225296

Published in SPIE Proceedings Vol. 2543:
Silicon Carbide Materials for Optics and Precision Structures
Mark A. Ealey, Editor(s)