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Re: [ATM] Simple Foucault tester for astigmatism


Hi All,

>Another approach to measuring astigmatism with a foucault tester
>is to rotate the tester itself.

First we had the L-shaped KE idea, but you have to rotate the mirror 45 degrees. So then we had the V-shaped KE idea, which is better. Now we get to rotate the entire tester. Sure, it'll work, but...

Isn't it easier to start with a CURVED edge? The more strongly curved the better, until diffraction becomes a problem. It is easy to make curved edges with a very small radius. And it is easy to make or buy a matching curved light source. And yes, it's real easy to use them. There is no rotating the mirror or the tester. It just works already.

John







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