Treatment method for optically transmissive body

Abstract

A method of treating a transmissive body of zinc sulfide or zinc selenide includes placing a non-platinum metal layer, such as a layer of cobalt, silver, or iron on a surface of the transmissive body, and improving the optical properties of the transmissive body by subjecting the body and the layer to an elevated temperature and elevated pressure. The zinc sulfide or zinc selenide may be chemical vapor deposited material. The non-platinum metal of the layer may be such that a Gibbs free energy of formation of a most stable sulfide (or selenide) of the non-platinum metal is more negative than a Gibbs free energy of formation of a most stable zinc sulfide (or zinc selenide) configuration that is thermodynamically capable of reacting with the non-platinum metal. With this condition the non-platinum metal preferentially chemically bonds with free sulfur (or free selenium) in preference to zinc sulfide (or zinc selenium).

Description

BACKGROUND OF THE INVENTION[0001]1. Technical Field of the Invention[0002]This invention relates generally to optical elements and methods for treating optical elements.[0003]2. Description of the Related Art[0004]As it is known in the art, some optical imaging systems include one or more externally mounted optical elements that shield the remainder of the imaging system from an external environment. For example, with infrared airborne imaging systems, an IR transparent optical element, such as a window or dome, may be part of the airborne system, used to isolate the remainder of the imaging system from exposure to humid, corrosive, and abrasive environments. Such elements often find applications on missiles, for example as part of a radar dome for a missile.[0005]Zinc sulfide and zinc selenide have been used in the past as a material for such domes. These materials are capable of providing a degree of mechanical durability and of providing reasonable optical performance in the long...

AI Technical Summary

Benefits of technology

[0009]According to another aspect of the invention a method of treating a transmissive body of zinc sulfide or zinc selenide includes the steps of: placing a non-platinum metal layer on a surface of the transmissive body; and improving optical properties of the transmissive body by heating the metal layer and the transmissive body. The heating is performed at an elevated temperature above normal ambient temperature and at an elevated pressure above normal ambient pressure.

Problems solved by technology

However platinum is an expensive material, and its use increases the cost of the treatment.

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