ABSTRACT
The mirror designer has at his disposal a number of metallic materials from which to choose. Table 13.1 lists key candidates. Table 13.2 lists properties generally considered in a materials trade-off analysis for a state-of-the-art mirror application. From the fabrication viewpoint, the metal-mirror designer should consider the available process options for each step and select those apparently best suited for the particular application. The typical fabrication cycle includes most, if not all, of the following steps: formation of the substrate, geometric shaping, stress relieving, plating (typically with electroless nickel [ELN]), optical finishing, testing, and coating. The stress-relieving step is especially important as a means for minimizing internal stress within the substrate that will tend to relieve itself with time or with changes in temperature, thereby causing the mirror surface to distort.
