Dear Bernhard,
Have a look at the Java applet "Diffraction and Fourier Transform"
located here: http://lcr.epfl.ch/page37304.html
You can draw an image, periodic or not periodic, the application will
compute the FFT. You can then select either phases or magnitudes or
Re/Im components and compute the FFT-1. You can also combine one set of
phases with another set of amplitudes etc. The Fourier spectrum can be
masked to simulate resolution limits, truncation errors etc. Using the
"Advanced" option, you can read in an image file (e.g. jpeg) and then
perform the FFT.
You need to have Java running on you computer.
There are other interesting applets on that page, e.g. "diffractOgram",
which illustrates the Ewald construction. I use many of these applets
for teaching purposes.
best regards
Marc Schiltz
Bernhard Rupp wrote:
Dear All:
I am trying to make FFTs of images of assemblies of
spheres and other shapes to explain diffraction, the
usual thing. So far I do this through cumbersome
cludges, and I bet there are better ways, and I
am looking for free or cheap software to do this.
I load the image into basic mathcad, dump it as a grayscale
array, SFT it with a F90 kludge (s=slow), and load the
transform back into MC and convert it into an image. However, what
I also want to do is generate a false color diffraction
pattern where the color is the phase. I believe this
is quite similar to the Fourier duck transforms Kevin Cowtan
made. I also recall a textbook were two crystallographers
were phase exchanged, so there got to be packages
that to what I want.
The mathcad image processing module is too expensive for my taste.
Any suggestions for software - maybe there is some software
out already to simulate diffraction from one, 2, 3 an array of
objects?
Cheers, br
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Bernhard Rupp
www.ruppweb.org
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--
Marc SCHILTZ http://lcr.epfl.ch
