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Space Forum / Astronomy / January 2007Diffraction though an aperture with a rounded edge.
For many applications you want to limit or remove the *diffracted* light though an aperture, so that the light arriving at the imaging plane is more closely described by the geometrical optics approximation. Intuitively, it would seem if the edge of the opening were rounded rather than sharp, less diffracted light would be able to bend around to enter the aperture. This would be particularly true if the radius of curvature of the edge was large with respect to the wavelength. Anyone know of references that address diffraction through apertures with a rounded edge? Bob Clark Dear rgregoryclark: On Jan 29, 1:44 pm, rgregorycl...@yahoo.com wrote: > For many applications you want to limit or remove the *diffracted* > light though an aperture, so that the light arriving at the imaging [quoted text clipped - 6 lines] > Anyone know of references that address diffraction through apertures > with a rounded edge? http://www.smeter.net/propagation/diffrac1.php ... "least diffraction loss occurs [with a] knife edge" I think you end up simply "feathering" the edges, rather than making some sort of discrete "ghost edge". David A. Smith > For many applications you want to limit or remove the *diffracted* > light though an aperture, so that the light arriving at the imaging [quoted text clipped - 3 lines] > rather than sharp, less diffracted light would be able to bend around > to enter the aperture ..... Bent intuition. Crooked physics. For a unidirectional incident wave, binary valued opacity, complete absorption vs. complete transparency, black vs. white, over two dimensions is the intuitive quantum rule. A "Cloudy Crystal Ball" smoothes fringes out. Same post, submitted two days in a row, Clark is a bear for punishment. [Old Man] > Bob Clark >> For many applications you want to limit or remove the *diffracted* >> light though an aperture, so that the light arriving at the imaging [quoted text clipped - 17 lines] > >> Bob Clark yes, and because he's so nasty, we don't tell him that he can improve the diffraction image by using a phase shifting mask. w. On Jan 30, 2:40 am, Helmut Wabnig <.... .-- .- -... -. .. --. @ .- --- -. DOT .- -> wrote: > ><rgregorycl...@yahoo.com> wrote in message > >news:1169829418.545614.276260@a75g2000cwd.googlegroups.com... [quoted text clipped - 20 lines] > > >> Bob Clark yes, and because he's so nasty, we don't tell him that he can improve the diffraction image by using a phase shifting mask. w.- Nasty? - Bob Yay! I was wondering Saturday if you were still induling in newsgroups :-). <snip> /BAH > Yay! I was wondering Saturday if you were still induling in newsgroups > :-). Just sci.physics, after a long absence. Resolved not to titillate the crackpots, it's worse than ever, but there're a few worthwhile posts. [Old Man] > /BAH >> Yay! I was wondering Saturday if you were still induling in newsgroups >> :-). > >Just sci.physics, after a long absence. Resolved not to >titillate the crackpots, it's worse than ever, but there're a >few worthwhile posts. There have been a lot more than usual. /erg is busy again. And there has been about one curious "kid" each month trying to puzzle out a mystery. /BAH > <rgregorycl...@yahoo.com> wrote in message > [quoted text clipped - 23 lines] > > - Show quoted text - Sorry about the double post. You can disregard this one and only respond to the first one. - Bob Clark In sci.physics.research rgregoryclark@yahoo.com wrote: > For many applications you want to limit or remove the *diffracted* > light though an aperture, so that the light arriving at the imaging [quoted text clipped - 6 lines] > Anyone know of references that address diffraction through apertures > with a rounded edge? The usual term for this sort of thing is "apodization". There's a very brief discussion at http://en.wikipedia.org/wiki/Apodization A Scholar.google.com query for "apodization" finds about 11,000 references, of which (for example) http://arxiv.org/abs/astro-ph/0301190 http://arxiv.org/abs/astro-ph/0512421 look like reasonable starting points, including assorted references to past work. Finally, note that further discussion of the astronomical uses of this might usefully be cross-posted to sci.astro.research. [Conflict-of-interest disclosure: I am deputy moderator of s.a.r.] ciao,  Signature-- "Jonathan Thornburg -- remove -animal to reply" <jthorn@aei.mpg-zebra.de> Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut), Golm, Germany, "Old Europe" http://www.aei.mpg.de/~jthorn/home.html "Washing one's hands of the conflict between the powerful and the powerless means to side with the powerful, not to be neutral." -- quote by Freire / poster by Oxfam |
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