[ATM] A ronchi question

[Jeremy Royston]

Hello David,
     There's a program for drawing inverse Ronchi gratings 
<http://www.atmpage.org/contrib/Holm/invron/invron.html>
You need a slow (ISO 25 or 100) high contrast b/w film and a camera - 
non-digital cameras have almost died out and the film is only available 
from professional photo shops. It's better to develop the film yourself. 
I have the equipment, but haven't made such gratings yet - my hobbyhorse 
is 2D-Hartmann

Best wishes, Jerry
> We have always used straight lines on our ronchi testers.  What effect, if
> any, would occur if we used lines of a different shape, i.e. curved lines.
> Could a matched set of curved lines be used for a null test on a paraboloid?
>
> David Davis
> Toledo, OR 97391
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