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Re: [ATM] Null Test for strong corrections

At 01:45 PM 8/9/2004 -0700, Gert Gottschalk wrote:



>My question. Has someone come up with a design for a
>Null-test system (2 lenses) that can be based on
>catalog lenses and is robust to tolerances (kitchen
>table proof) ??


Gert

Offner ( 2 lens ) null systems generally have very tight lens separation 
tolerances. You'll find by double passing a plano-convex lens ( Ross test ) 
you'll get a much smaller residual error. The down side is that the  lens 
surfaces have to be extremely good. Any errors on the lens surfaces will 
appear faithfully in your wavefront because the lens is double passed.  An 
off the shelf lens is unlikely to be good enough  unless you can buy a much 
larger aperture than you need.    There is Ross software available on the 
net , to calculate all the info you need.

Hope this helps

Mark






















>Thanks,
>
>Gert
>
>
>
>
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