Cleaning Optical Filters

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Cleaning Filters

Cleaning of Optical Components

Note: You follow this advice at your own risk.

All optical elements are delicate and should be handled as carefully as possible. The glass and antireflective (AR) coated surfaces will be damaged by any contact, especially if abrasive particles have come into contact with the surface. In most cases, it is best to leave minor debris on the surface.

Use of oil-free dry air or nitrogen under moderate pressure is the best tool for removing excessive debris from an optical surface. In the case that the contamination is not dislodged by the flow of gas, please use the following protocol for cleaning the part:

1. Clean the part using an absorbent towel such as Kimwipes™, not lens paper. Use enough toweling so that solvents do not dissolve oils from your hands which can make their way through the toweling onto the coated surface.

2. Wet the towel with an anhydrous reagent grade ethanol.

3. The use of powder-free gloves will help to keep fingerprints off the part while cleaning.

4. Drag the trailing edge of the ethanol soaked Kimwipe across the surface of the component, moving in a single direction. A minimal amount of pressure can be applied while wiping. However, too much pressure will damage the component.

5. If the surface requires additional cleaning, always switch to a new Kimwipe before repeating the process.

The purpose of the solvent is only to dissolve any adhesive contamination that is holding the debris on the surface. The towel needs to absorb both the excessive solvent and entrap the debris so that it can be removed from the surface. Surface coatings on interference filters and dichroics are typically less hard than the substrate. It is reasonable to expect that any cleaning will degrade the surface at an atomic level. Consideration should be given as to whether the contamination in question is more significant to the application than the damage that may result from cleaning the surface. In many cases, the AR coatings that are provided to give maximum light transmission amplify the appearance of contamination on the surface.