From the first section, basic principles:<p>"any signal" huh?
"spatial frequency" 2x huh?
"a "DC term" corresponding to zero frequency" #seriously<p>This is intuitive only if you already know this stuff, which I happen to, but I have also tried to explain this to undergrads taking history and english. Terms like these are not intuitive at all.
Here's a tool that let's you try the transform interactively: <a href="http://www.ejectamenta.com/Imaging-Experiments/fourierimagefiltering.html" rel="nofollow">http://www.ejectamenta.com/Imaging-Experiments/fourierimagef...</a>
Curious... If the Fourier transform can be 'calculated' by photons passing through an optical lens, has anyone ever produced a component that could capture the computation numerically? I.e., some sort of capsule/chip with:<p>* A digital-to-analog converter with pixel array on one end
* A lens in the center
* A sensor array with an analog-to-digital converter on the other end