Talk:Fresnel lens

Password Protected References

The four references are all password protected. Would not it be better to use passwords that are not protected? KudzuVine 21:42, 27 May 2007 (UTC)[reply]

Compressed optical lenses

Just a quick word. This whole page is talking about compressed optical lenses. I'm pretty sure that these are not Fresnel Lenses. The ones mentioned here are mistakenly called Freznel lenses because they are essentially flat like a Fresnel Lens. [[zone plate|Fresnel zone plates}} are the actual Fresnel Lenses. --WB-Frontier 11:12, 10 April 2006 (UTC)[reply]

What's the highest resolution for one? lysdexia 11:50, 22 Oct 2004 (UTC)

These aren't that great. And wouldn't be used anywhere were resolution is important. But they work quite well for things like overhead projectors. --WB-Frontier 11:12, 10 April 2006 (UTC)[reply]

Canon makes two lenses that use Diffractive Optics, the EF 400mm f/4 DO IS USM and the EF 70-300mm f/4.5-5.6 DO IS USM http://www.canon.com/camera-museum/tech/report/200106/report.html http://www.canon.com.au/products/cameras_lenses_accessories/super_telephoto_lenses/ef400mmf4isusm.html http://www.canon.com.au/products/cameras_lenses_accessories/telephoto_zoom_lenses/ef70-300mmf4.5-5.6doidusm.html http://www.the-digital-picture.com/Reviews/Canon-EF-400mm-f-4.0-DO-IS-USM-Lens-Review.aspx http://www.luminous-landscape.com/reviews/lenses/400-do.shtml http://www.dpreview.com/news/0009/00090604canon_400do.asp

I was surprised by this engineering prof claiming Fresnel had nothing to do with it. This page implies David Brewster claimed the honor. AZ State Engineering and (according to the snippet in the Google search) Encyclopædia Britannica, credit Buffon. (As does Beavertail Lighthouse Museum, which I found interesting because lighthouse fans seem prone to putting up silly "parrot the answer I want to hear" quizzes. [1] [2] [3] [4] [5]) Fresneltech (pg 2) claims that the famous Condorcet was in on it besides Buffon and Brewster. My read is that the crucial idea of the segmented lens was not Fresnel's, not even as an independent reïnvention; his contribution seems to have been flattening. Kwantus 18:50, 2005 Jan 27 (UTC)

I searched a number of sources, including Encyclopedia Britannica and biographical reference sources available to me through the University of North Carolina Greensboro library. Using what I discovered that way, I added a paragraph about the development of the Fresnel lens. Well, actually, I guess it is about the various people who were involved in its development. I'm not an optics expert, by any means, but I used what I could find from reliable sources. -- Kam Tonnes 20:09, 11 November 2005 (UTC)[reply]

My recent change also added a little more on the prismatic elements found in lighthouse Fresnels. This might want to move out of the "Uses" section, and could use a diagram of the light paths.

If there's standard terminology to describe the planar Fresnel (made by flattening a planoconvex lens) we usually think of versus the full-on constellation including these catadioptric elements, I don't know it.

Eub 07:21, 28 September 2005 (UTC)[reply]

Removing text "A related optical device is the Fresnel zone plate." because I don't see how they're related, beyond the inventor's name. If you do, please re-add this text with explanation. Eub 05:40, 29 September 2005 (UTC)[reply]

Traffic light implementation

The traffic light article states that some new lights use Fresnel lenses to limit the visibility of the light to cars in specific lanes. While I have seen such sytems in some intersections, I don't know enough about the subject to definitively link traffic lights and Fresnel lenses. Could someone more knowledgable than me add a section on this form of implementation, if these lenses are in fact used in traffic lights? — EagleOne\^Talk 18:02, 28 April 2006 (UTC)[reply]

Request

Would be great if someone could create a diagram showing the path of the light rays.

There is a nice web page describing a Fresnel lens that does this. However, I have a different comment about this page http://www.lanternroom.com/misc/freslens.htm If you look at the bottom of the page, the author states that the material is copyrighted (that's fine), but then the author states that people should not hot link to his Fresnel lens site. I doubt that any form of copyright could properly forbid people from hot linking to a site. If my assumption is true, you should be able to link to his site, and accomplish two things--first, see the path of the light, and second, refer users to another place where a good description of a Fresnel lens is located. Possibly if some WP editor sees this comment, he can tell us if forbidding hot links to a web page is enforceable. I suppose the author could always remove the link from the WP article, but would that be vandalism? Thermbal 00:07, 24 December 2006 (UTC)[reply]

Film and video uses

Lighting gaffers use the focusing ability of Fresnel instruments for two purposes: to modify light intensity by spreading or narrowing the beam and to change beam-edge characteristics (from hard to soft). Beam edges are masked by one or both of two methods: by "barn door" flaps mounted on hinges in front of the lens and moved in and out of the light path, and/or by "flags:" (usually) rectangular sheets or paddles placed on separate stands some distance in front of the lighting instrument. Both masking techniques can be fine-tuned by altering the focus of the light beam. A hard line edge may be wanted or a fairly subtle falling off -- or anything in between.

Not sure any of this properly belongs in the Fresnel article though. --Jim Stinson 00:11, 11 July 2007 (UTC)[reply]

minor edit

I touched up the paragraph on theater and motion pictures slightly to improve accuracy (the phrase I cut: "brighter than a typical lens" is too vague. What is a typical lens? Jim Stinson 02:53, 23 October 2007 (UTC)[reply]

what does this mean??

Development The idea of creating a thinner, lighter lens by making it with separate sections mounted in a frame is often attributed to Georges-Louis Leclerc, Comte de Buffon.[1] However, it is difficult to find any other sources that link Buffon to work with optics. French physicist and engineer Augustin-Jean Fresnel is most often given credit for the development of this lens for use in lighthouses. According to Smithsonian, the first Fresnel lens was used in 1822 in a lighthouse on the Gironde River in France, Cardovan Tower; its light could be seen from more than 20 miles out.[2] Scottish physicist Sir David Brewster is credited with convincing the British to use these lenses in their lighthouses.[3][4]

more specificaly. what does this mean???

is often attributed to Georges-Louis Leclerc, Comte de Buffon.[1] However, it is difficult to find any other sources that link Buffon to work with

Any other sources????????, any other sources, other than what????? WTF. Just be glad that you, the person that wrote this idiocy, are not in my presence right now for I would certainly give you a piece o my mind!!!!! Georges-Louis is the subject, I can understand that. What are these previously un mentioned other sources??????? Wouldn't it be better to just leave them out altogether!!!!!!

Oh, and while I am at it, isn't it, "the Smithsonian Institute", or something like that, somone needs to look at a style guide!!!!!