Talk:Fresnel lens

Pronunciation

Here: (pronounced ['frɛz.nəl] or [freɪ'nɛl]) In the Fresnel bio article:(French pronunciation: [ɔgystɛ̃ ʒɑ̃ fʁɛnɛl]; pronounced /freɪˈnɛl/ fray-NELL in English) Why would we pronounce the two uses differently? (As far as I know, saying a "z" in the word is bad usage) Hoemaco (talk) 17:35, 19 October 2008 (UTC)

Pronunciation of something named for a person does not always follow pronunciation of the name. Take Mt Everest for example which is pronounced usually as Ever-rest or Ev-rest, while the man for whom it is named pronounced his name as Eave-rest. But I do wonder if it's pronounced Frez-nel. Most dictionaries I've found give a soft s pronounciation. —Preceding unsigned comment added by 67.189.184.5 (talk) 21:17, 2 January 2009 (UTC)

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)

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)

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)

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)

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)

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)

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 knowledegable than I 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)

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)

Request

Would love to see an explanation of the differences between first, second, third, and fourth order Fresnel lenses referenced but not explained in this article. There is a photo of a third order lense and a notation in other locations about the detroit river light house having donated it's fourth oder fresnel lense to a museum and I now wonder just what the differences might be between these types. If anyone can shed some light (pun intended) it would be most appreciated. —Preceding unsigned comment added by 151.166.15.114 (talk) 19:19, 6 July 2010 (UTC)

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)

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)

"any other sources"? Smithsonian?

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??, other than what?? Georges-Louis is the subject, I can understand that. What are these previously unmentioned other sources?? Wouldn't it be better to just leave them out altogether!

I agree. If it means other than EB (mentioned in footnote), then EB needs to be mentioned in the main text, not merely a footnote. Nurg (talk) 02:54, 20 December 2007 (UTC)

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!!!!! —Preceding unsigned comment added by 124.182.67.203 (talk) 04:51, 23 November 2007 (UTC)

First of all, it's the Smithsonian Institution, not the Smithsonian Institute. But no, the excerpt cited above has a footnote in the article (that's the significance of the [2] after the sentence. The footnote is to an article in Smithsonian, the magazine published by the Smithsonian Institution. 140.147.160.34 (talk) 22:43, 2 January 2008 (UTC)Stephen Kosciesza

Retina identification - link fix?

One of the paragraphs in the 'Uses' section contains a redlink to 'retina identification'. I thought I might point it to retinal scan, possibly retaining the original wording - does anyone who knows more than I about the subject know of any reason why that might be a bad or misleading idea? Cooperised (talk) 21:17, 2 April 2008 (UTC)

In the absence of a reply I went ahead and made the change. Cooperised (talk) 21:34, 4 April 2008 (UTC)

Space telescope

Diffractive telescopes with Fresnel lenses fabricated on thin membranes offer several advantages over telescopes that use mirrors: thin-membrane lenses are lightweight, packageable, and space-deployable. Transmissive diffractive lenses are significantly less sensitive to surface deformations than mirrors, and the chromatic effects of the diffractive primary can be completely compensated for. As a first step in developing the Eyeglass technology, LLNL scientists built and tested a small-aperture (20-cm), color-corrected diffractive telescope and obtained a broadband image of the lunar surface. Next, they built and demonstrated an 80-cm-aperture segmented, foldable lens. In 2002, the researchers constructed a 5-m, f/50 Fresnel lens – comprising 72 segments patterned with binary Fresnel arcs in photoresist – and secured it to a 750-μm-thick sheet of glass with UV-curable cement and metal tabs. The assembled lens was mounted in a frame and the focal spot of a white-light source mounted at the opposite focus was imaged. This demonstration lens was not made to give diffraction-limited performance, but to demonstrate assembly and deployment at a scale large enough to be of interest for imaging. The surfacetension gradient between a thin film adhering to a substrate and a free surface of falling film is strong enough to pull etchant off of the substrate surface. Regardless of substrate movement, the wetted zone remains stationary relative to the applicator. The Marangoni effect can also be thermally driven.

https://lasers.llnl.gov/programs/psa/pdfs/technologies/eyeglass_space_telescope.pdf

217.196.160.253 (talk) 00:18, 7 April 2008 (UTC) 217.196.160.253 (talk) 00:21, 7 April 2008 (UTC) 217.196.160.253 (talk) 00:23, 7 April 2008 (UTC)

What Fresnel's orders mean

The references do not seem to support the contention that the order of a lighthouse lens is roughly equal to its power in diopters. The correspondence is extremely rough, and only works for the American ranking, not Fresnel's original system (at least as given in the referenced chart from the LoC). This claim needs a definite citation of its own. Mangoe (talk) 14:34, 4 October 2008 (UTC)

Moving Fresnel reflector info to its own article

Fresnel reflector is currently redirecting here. I don't believe Fresnel reflectors are a type of Fresnel lens so I plan to move the information on Fresnel reflectors to their own article. It will have links back here. Lumenos (talk) 21:28, 10 June 2009 (UTC)

I think the best place to discuss this would be there not here. Lumenos (talk) 21:18, 13 August 2009 (UTC)

Is this an early Fresnel lantern lens?

I was surprised to see what looks to my untutored eye to be a Fresnel lens in a Renaissance painting of Caravaggio, The Taking of Christ.

The unhelmeted soldier on the right raises a lantern that holds the lens. We can see the characteristic light through the lens (or rather what I'm guessing that light might look like) in two bands on the billowing cloak of the terrified St. John, who's running away screaming.

Would you characterize as a crude "Fresnel" lens this lantern glass from the early seventeenth century? It might be worth mentioning in the article if so. Pete142 (talk) 22:58, 14 October 2010 (UTC) Pete Wilson

No, that's not an early Fresnel lens, and not even a lantern glass.

It's a folding paper lantern, much like this one. Jaho (talk) 15:53, 16 December 2010 (UTC)

Description confusion

In the description, it says " <<<Actually 'single-piece' Fresnel lenses have been produced for decades. Such examples are Also, brake, parking, and turn signal lenses, all being of one piece of glass, also use this technology, and have been produced for years without the aid of computers." This is confusing and almost contradictory. Perhaps it should say; "It was not until modern computer-controlled milling equipment (CNC) could turn out large complex pieces that these lenses were manufactured from single pieces of glass. However, smaller fresnel lenses have been widely produced for decades without the aid of computers. Some examples include automobile headlamps, with their multi-faceted lenses that direct the light into a particular pattern and direction."

Manufacturing needed

http://lighthouse-society.org/assets/resources/articles/fresnel_lens_1.pdf

Are the lenses cast as one or individual prisms?--Ericg33 (talk) 08:29, 30 June 2011 (UTC)