Mirror substrates with highly finishable corrosion-resistant coating

Abstract

The disclosure is directed to optical elements including a performance-enhancing coating on the surface of a metal or ceramic substrate and to methods for making the optical elements. The optical elements are suitable for use in harsh environments, including salt fog and high humidity environments. The performance-enhancing coating and substrate have similar thermal expansion properties and the performance-enhancing coating has a diamond-turned surface. The performance-enhancing coating may also be polished with a solution of colloidal silica in glycol to an RMS surface roughness less than 30 Å.

Dependencies are inferred from the claim text.