Also (since I didn't know what a "thin lens" was prior to reading this (I never studied Optics)) I Googled it, and found the Wikipedia page for it:
https://en.wikipedia.org/wiki/Thin_lens
>"In optics, a thin lens is a lens with a thickness (distance along the optical axis between the two surfaces of the lens) that is negligible compared to the radii of curvature of the lens surfaces. Lenses whose thickness is not negligible are sometimes called thick lenses.
The thin lens approximation ignores optical effects due to the thickness of lenses and simplifies ray tracing calculations."
Which makes me wonder if there's a link between Fourier Transformations and Ray Tracing, and if so, how does it express itself?
Although, that's probably going seriously off-topic for this HN article! <g>
Anyway, thanks again for the link/info!
Prisms and diffraction pattern gratings split light according to the frequency of the photons (colours) in the input. That's a Fourier transform in a certain sense, and you'd use that to make a spectral analyzer. But what about the Fourier transform of an image, according to the frequency components of objects in the image? Like fence posts at a regular spacing, and such?
Well you might be excited to learn that optical lenses actually compute the Fourier transform of their input image:
http://web.mit.edu/2.710/Fall06/2.710-wk10-a-sl.pdf (the ideal thin lens as a Fourier transform engine, PDF)