Cleaning and Protecting Large Mirrors Using a Polymer Solution

Polymer cleaning solution eliminates residue on optical surfaces.

Cleaning and protecting optics is a challenge — contamination must be removed without damaging the surface. Preventing recontamination for extended periods of time after cleaning was unattainable prior to use of polymer strip coat films. The SLRSC Western Range Depot Optics Group, WRDOG, at Vandenberg Air Force Base, is a pioneer in the cleaning and protection of precision glass optics, lenses, and large mirrors using polymer solution technology.

Contaminants on optical surfaces cause problems ranging from moderate to severe performance degradation to catastrophic destruction. Traditional optical cleaning is a mixture of art and science requiring good technique in combination with high-purity solvents for satisfactory results. Since airborne contaminants immediately begin to recontaminate the optical surface when the cleaning process stops, traditional cleaning methods (such as drag wiping or CO₂ snow) require significant effort to prevent recontamination during the cleaning process.

An ideal optics cleaning process allows treatment of all optics regardless of shape, size, or material composition. An effective cleaning process leaves no residue and removes particulates, oils, fingerprints, etc. from the optic surface. In a more perfect world, a cleaned optic will stay clean up to time of use, regardless of when the cleaning process was performed.

A new polymer solution effectively and safely cleans all glass optics, coated optics, silicon surfaces, sensors, crystals, and first surface mirrors, provided the substrate/coating interface is strong and intact. Cleaning is not recommended for poorly adhered coatings since if the coating/substrate interface is weak or in poor condition, the coating may be removed by any cleaning activity. This caution applies to traditional cleaning methods as well as strip coat cleaning.

The polymer solution has about one-tenth the adhesion to surfaces as standard Scotch tape. A practical application of the polymer in quality control would be its use as an effective optical component Acceptance Test since poor quality coatings or coating imperfections would be revealed when the polymer is removed from a brand new optic.