Talk:Zone plate

message: The zone plate seems to have been invented by Lord Rayleigh, as evidenced by his notebook entry  on 4/11/1871: "The experiment of blocking out the odd Huygens zones so as to increase the light at centre succeeded very well."  —Preceding unsigned comment added by 128.112.50.118 (talk) 20:15, 14 April 2008 (UTC)
thread_title: Not Invented by Fresnel

message: Zone plates are useful for more than just lenses. They are good for testing video systems, printing processes, image scaling algorithms, alpha blending, gamma correction errors... AlbertCahalan 01:20, 16 Jun 2005 (UTC)
replies: text: Then you should add descriptions of these uses here.  The general rule of thumb is to write on one topic until the article becomes long enough to spin subtopics out as their own articles rather than vice versa.  In other words, this article should strive to collect all uses of zone plates until enough material is here for spin-offs, at which point the appropriate spin-off topics should be apparent by the article's organization.  So far I only wrote about uses I know of personally, and no one has added to that section since then.  --Laura Scudder | Talk 07:29, 16 Jun 2005 (UTC)
thread_title:  should move this to "zone plate lens" 

message: The Formula given for the radius is only valid as an approximation when the radius of the zone plate is much less than the focal distance, otherwise higher order terms come into play. The exact formula can be found by application of Pythagoras: The distance from a point at radius r on the zone plate to the focus, a perpenidcular distance f from the the zone plate, is \sqrt{r^2 + f^2}. Thus the optical path difference (OPD) as r varies is \sqrt{r^2 + f^2} - f. The radius of the nth half-period zone, rn occurs when the OPD is n half-wavelengths: \sqrt{r_n^2 + f^2} - f = n\lambda/2. Expanding this square root with the binomial expansion and taking only the first two terms yields the approximate formula r_n = \sqrt{n \lambda f}, but rearranging without making any approximations gives the correct formula r_n = \sqrt{n \lambda f + \frac{n^2\lambda^2}{4}}.131.111.213.211 14:38, 16 January 2006 (UTC)
thread_title:  Given formula for radii only approximate 

message: Regarding the discussion in relation to video resolution: Is this really a zone plate? Isn't it just a high-frequency test sample? That is, doesn't it have nothing to do with diffraction? 155.212.242.34 17:52, 29 October 2007 (UTC)
thread_title:  "Video" section 

message: The article uses the focal length f as the free parameter in the early part but then switches to another parameter k which is not defined.
Comparing the r_n for n=1 with the zero of the cosine (pi/2) gives me k=2*pi/(4*lambda*f+lambda^2), but I'm not sure if that interpretation is correct.
--Ralf Muschall (talk) 19:01, 20 February 2012 (UTC)
thread_title:  Relation between free parameters 

message: Just in case, this page has two free as in Creative Commons Zero/Public Domain zone plates: http://www.thetenthplanet.de/archives/3859  — Preceding unsigned comment added by 37.209.110.47 (talk) 16:46, 23 April 2014 (UTC)
thread_title:  Free plate pictures (CC0) 

message: I removed the following material, because the claimed connection between the Fresnel zone plate and the Fresnel lens is not supported by a citation. It's not clear to me that the claimed connection is true. --Srleffler (talk) 05:02, 28 May 2014 (UTC)
thread_title:  Relation to a Fresnel lens 

message: I propose to merge Aragoscope into Zone Plate. I think that the content in the Aragoscope stub can easily be explained in the context of Zone Plate, and the Aragoscope article is of a reasonable size that the merging of Zone Plate will not cause any problems as far as article size is concerned. Blablabliam (talk) 15:57, 22 May 2019 (UTC)
replies: text: I don't see any advantage in doing that. An Aragoscope is a distinct enough thing to have its own article.--Srleffler (talk) 06:11, 23 May 2019 (UTC)
replies: text: I think the Aragoscope is distinct in that it is a specific type of zone plate, but with the page the way it is, it is too short to stand alone. To flesh out the page would be essentially just copying info from the Zone Plate page, which does not add anything useful to Wikipedia. It would be like having zone plate gun scope having a page while zone plate gun scope is already listed here. I think it would be easy to merge it into the Applications section. That being said, you clearly have more experience with these things and know a lot more about it than I do. Blablabliam (talk) 22:07, 28 May 2019 (UTC)
thread_title:  Merger proposal