On Friday, October 25, 2002, at 04:21 PM, Guillermo wrote:
----- Original Message -----
From: "Guillermo" <pen...@rogers.com>
I gather that by "aperture of the zone plate" you mean the size of
each of
the rings. Mr.Pinhole formula is what the scientific community uses
for
their high-tech uses of zone plates and my non-scientific tests
(focusing
aerial images produced by zoneplates) have confirmed that. Other use
slightly different formulas.
I was reading my own post and it seems not to be too clear.
What I meant was that when I mount zone plates on my 4x5 view camera
and
focus on the aerial image until it is a "sharp" as they would be, the
distance zone plate to film plane matches very closely with what the
formula
Radius = SQRT(wave length x focal length x ring#) would predict.
Now, the formula can also be written as Diameter = 2 x SQRT(wave
length x
focal length x ring#). Some people use formulas slightly diferent,
what
they change is that number "2", Patton for instance, uses 1.86
http://www.stanford.edu/~cpatton/zoneplatemath.htm
Guillermo
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Hi-
The goal is to calculate f number of the zone plate, for a first
approximation of the exposure. So it sounds like the formula will work.
All I have to do is keep radius and diameter straight.
Thanks for your help
Beaker
