Re: [ATM] How do I test a convex surface?

[Dominic-Luc Webb <dlwebb@canit.se>]

There is one test you did not list, which has actually been
used in ATMing (by me amongst others). There are tests in which
the lens is placed in a tank filled with fluid of same refractive
index as the lens. This fluid is prepared by mixing two solutions
with slightly lower and lightly higher refractive index in
exacting proportions. Then you would test as a concave.

In some cases, since many people now use very high precision
micrometers, I guess you could get pretty close by measuring with
a spherometer from the start and then polishing a little at a
time to see which strokes on which surface improve the test
results. At least for Schmidt cameras, there are tests for the
completely assembled optical system. I could guess there are
similar tests for assembled refractors, but I have not done this.

Dominic-Luc Webb

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