Re[2]: [ATM] A two way null test for convex hyperboloids

[Richard <cnc@cncservo.co.uk>]

Hi Mauritz,

Yes, that's more or less what I'm ray tracing now. It seems that
the null for those specific raidii and K is quite dependant on
the glass type. The 10 wave abberation I saw is with BK7. If I
change the glass to fused silica I can re-optimise focal
distance to get down to about 1/2 wave, but with generic quartz
I can't get any better than 15 waves. What exactly is the
"QUARTZ C" that oslo is using?

Personally, although quite an original idea, I don't see the
benefit over using a plano back to the mirror and getting the
null from a ross or offner null setup. At least that keeps the
number of aspheric surfaces down to one, and you can be sure of
surface that null does represent. With the bi-convex idea, I
would be very worried by the interdependance of the two radii
and conic constants - maybe if the refractive index of the glass
is slightly different, the two surfaces may converge to
something altogether different.

-- 

Best regards,
 Richard



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