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Is it possible to have a lens recoated??

Started Jun 27, 2005 | Discussions thread
MitchAlsup Veteran Member • Posts: 5,518
Re: I Agree but.....

Artgrapher wrote:

Hi Mitch,

The way you described how makers coat lens sounds like coating is very expensive, done in vacuum with tolerances in the submicron level. How can Walmart's sunglasses with anti-reflective coatings go as low as $15 a pair? What gives?

Artgrapher

My prescription eye glasses are no better than 2-3 waves of surface error, but since they are only correcting an image (rather than focusing an image) my eye can only tell when I use "optical stuff" to perform the lens analysis. So, where in the image formation process a lens is has a lot to do with how precise its surfaces have to be. Correctors do not have to be as good as focusers.

Secondarily, Walmart sunglasses are make in the millions (maybe millions per month) and at this kind of production rate, a batch of said lenses would consist of a sheet of transparent plastic maybe 20 feet by 8 feet in size that is run through a continuous vacuum chamber, and after coating the lenses are cut and formed (more like cookies before baking than optical parts). Given a high enough manufacturing rate and continuing demand, one can drive cost out of the manufacturing process. So, cheap plastics, coated in tennis court sized batched in a continuous process, and manufacture optimized to remove every cent of excess cost.

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Mitch

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