Re: [ATM] Aplanatic Beamsplitter Foucault

["Bob May" <rmay@nethere.com>]

A much easier setup is to do the KE at the output of the
beamsplitter.  The beamsplitter, of course, needs to be small as
you have to be able to gather in the light from the optics at the
backside of the KE but you can do a nice slitless tester that
way.
As I see it, you only need to do one convex surfacce as the slit
and KE in your design will be at the face of the cube which means
that it doesn't matter what the shape of the back and side faces
are.  The front surface only needs to be at the ROC of the
distance from the slit in order to function right.  Rather than
mess up a beamsplitter by putting a curve on it's face, get a
seperate piece of glass, preferably of the same material as the
beamsplitter, and do the lens necessary.  Beamsplitters are
usually BK7 or SF10 or BaK1 and those glasses aren't expensive.
Just make the ROC of the convex surface equal to the distance
from the surface to the KE and you're in there right.  Glue the
lens to the face of the beamsplitter with some canada balsam and
you're done.
Bob May
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