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AP Recoating

Started by RussCarroll, 09/13/2011 02:56PM
Posted 09/13/2011 02:56PM Opening Post

Is it possible to send an AP refractor back to the factory for re-coating of the objective?


Posted 09/15/2011 11:18AM #1

There are lots of different kinds of coatings that can adhere to a glass surface, and we cannot assume that each can be easily removed.

For example, the coating of a mirror sits on the surface of the glass and is made of metal that can be etched off. Therefore such a coating can be removed easily without using mechanical means.

The coating of a lens is partially embedded in the glass surface, and is made up of oxides and fluorides, that are similar in composition to glass. They are highly resistant to chemicals and acids, and even if they could be removed this way, they would take part of the glass with them. Therefore the only way to remove them is by polishing. This of course changes the figure of the glass and the lens would have to be refigured, which is a time consuming costly operation.

On the other hand, a coating such as produced by a fingerprint (or roast beef vapor in your kitchen) does not have to be polished off or removed via acid etching, and can be removed easily with simple soap and or alcohol/acetone wiping. A roast beef coating is easy to apply and to remove, whereas an anti-reflection coating is not so easy.