Talk:Anti-reflective coating

message: Should this page be merged with Optical_coating#Antireflection_coatings? They seem to have extremely similar contents.
:The contents of that section should be merged here, and then that section should be reduced to a summary, with the "main article" template linking to the broader description here. Antireflection coatings are an important enough special case to have their own article.--Srleffler 17:12, 30 April 2006 (UTC)
thread_title: Merge #1

message: I also think Anti-reflection lens should be merged here. An "anti-reflection lens" is just a lens with an anti-reflective coating. Besides this, though, that term is AFAIK not used at all in optics. From the content of the article, it is presumably used in the consumer eyewear industry. I don't see why opthalmic uses of antireflection coatings can't be covered in a section here instead.--Srleffler 00:36, 18 January 2007 (UTC)
replies: text: Merge complete. --Srleffler 13:15, 30 January 2007 (UTC)
thread_title: Merge #2

message: I recall reading some time ago that certain insect eyes have a natural AR coating that works completely differently to the types described in the article. It was a type of nanostructure involving pillars of material on the surface. Scientists were studying the structure with an eye to using it for engineered coatings. Anybody know anything about this? It would make a good addition to the article.--Srleffler 05:41, 18 January 2007 (UTC)
replies: text: I found some articles on it and added a section.--Srleffler 06:02, 18 January 2007 (UTC)
thread_title: Nanostructure?

message: What does the term used in the text, "light deep," mean? Is this a mistake? P0M (talk) 06:23, 28 March 2008 (UTC)
replies: text: The whole phrase was "one-quarter of the wavelength of the light deep", i.e. "having depth equal to ¼ wavelength". Not a mistake, but it was very poorly phrased. I've rephrased it.--Srleffler (talk) 16:06, 28 March 2008 (UTC)
thread_title:  odd term 

message: Dear users. Unfortunately, many of us editors about inventions arent aware of an important category: :Category:Inventions by country. This article fits Russian inventions, because Smakula was originaly from the Russian Empire, German inventions, because he have done it in Germany, and Ukrainian inventions, because even thought there was no Ukraine when he was bornm he was ethnicaly Ukrainian and today Kherson, where he was born, is Ukraine.
If you have the question of but wait a minute!!! Many people took part in thar invention, many theries. To who of them it goes?
To the one who is widely considered. For example. The Tank. Before the British made the tank that became commercialy succesful many people built models of it. Some succesful. But the British made it really famous, commercialy succesful. They made the model that counts, lets say it like that. Thats why the tank goes to British inventions.
Another point. If a man is of one nationality, but made the invention in another country, the invention fits both categories, and that is the case here. See the example of Rubber band. It enters the category of English inventions even though it was invented in Australia, why? It's inventor was English.
Please be aware of that type of categorising to. Kostan1 (talk) 10:30, 4 August 2008 (UTC)
thread_title:  Russian, Ukrainian, German inventions categories 

message: I was wondering if the figure in the section "Interference in a quarter-wave anti-reflection coating" is misleading. It shows that the thickness of the coating is lambda/4 and the lambda is the wavelength of the incident wave in the air. However, the wavelength of the wave inside the coating is not lambda. It is less than lambda because the wave now is in a different medium than air. The thickness of the coating should have been (1/4) of the wavelength of the wave inside the coating. Am I right? I am not sure. Someone with knowledge of anti-reflective coating should check this. Thanks.  — Preceding unsigned comment added by 165.91.183.249 (talk) 21:24, 28 May 2011 (UTC)
replies: text: Well, the lambda \lambda symbol represents the wavelength of light, but doesn't neccessarily specify the wavelength as being in air, vacuum, or some other medium. The refractive index of the coating also has to be taken into account, and so does the angle of incidence and the color of the light. A \lambda/4 (wavelength/4 or 1/4 wavelength) coating means that the thickness of the coating is 1/4 of the wavelength of the light that the transmission is centered on, taking into account that the wavelength is shorter in a higher refractive material. For multiple coating stacks, the refractive index of each layer must also be taken into account, because the center-wavelength will shift in each of them. Not only that, but the desired angle of incidence must also be taken into account. For an AR coating with a 0 degree angle of incidence the coating will be thicker than a coating centered on the same wavelength but at a 45 degree angle. Zaereth (talk) 03:40, 29 May 2011 (UTC)
thread_title:  Figure in "Interference in a quarter-wave anti-reflection coating" 

message: I remember when Pentax (Asahi) introduced the first multi-coated lenses in the early '70s, under patents from an American firm (whose name I forget). (That alone is remarkable, that a Japanese firm would license American patents to manufacture someithing it hadn't invented.) There were people who said it couldn't possibly work. This bit of history ought to be included. WilliamSommerwerck (talk) 15:16, 25 August 2011 (UTC)
replies: text: Well, according to the book Thin-film optical filters, W. Geffken created the first interference filters, using multi-layer stacks, back in 1939. The book says nothing about the first multi-layer stacks in AR coatings. (It does say that Joseph Fraunhofer created the first intentionally produced AR coatings back in 1817, but that was a single layer.) It seems to me that 30 years would be a long time between multi-layer filters and AR coatings, but stranger things have happened. While I don't doubt your memory, what we'd really need is a reliable source so Wikipedia can verify the information. I don't have time to research it right now, but if you can find something, I'm sure it would make a wonderful addition to the article. Zaereth (talk) 16:29, 25 August 2011 (UTC)
replies: text: OK, I had a few minutes at break today to do a little research. It appears, according to Applied optics and optical engineering, that Geffken is indeed responsible for creating the first multi-layer stacked AR coarings back in Germany, during World War II. Geffken apparently based his work on Thelen's theoretical designs, coming up with the standard quarter-half-quarter design. I hope that helps. Zaereth (talk) 18:20, 26 August 2011 (UTC)
thread_title: history of multi-coating

message: The discussion above is great, but has drifted quite far from what I see as the central issue for this article. That issue is that Alexander Smakula did not invent the antireflection coating, so it is nonsense to tag the article Anti-reflective coating with either the "Ukrainian inventions" or the "German inventions" tags. The presence of these tags on this article implies that anti-reflective coatings were first invented in either Ukraine or Germany, which is false. I propose to remove these tags from the article, and welcome any discussion on that subject. The "British invention" tag is also open to discussion.--Srleffler (talk) 01:00, 3 May 2013 (UTC)
thread_title: Discussion more specific to this article

message: I'm going to remove the new "calculus details" section, for the following reasons:
*The article has a theory section, and this material belongs there.
*The new section is partly redundant with the existing theory section.
*To the extent that the new material is not redundant, I don't see an easy way to work it into the existing theory section.
*The new section treats interference without considering or even mentioning the phase of the waves. 
*Wikipedia is not a textbook
--Srleffler (talk) 07:23, 27 November 2014 (UTC)
thread_title:  Calculus details 

message: The figure titled "Interference in a quarter-wave anti-reflection coating" appears to not show the correct phase change upon reflection.  The phase flips 180 deg when reflecting from low to high index.  This occurs in both reflections here, so both reflected waves appear 180 deg off.
http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/antiref.html
199.46.200.230 (talk) 16:59, 6 January 2016 (UTC)
replies: text: The figure is correct. Both reflected waves cannot be 180 degrees out of phase. One must be 180 degrees out of phase with the other, which is what the figure depicts. If they were both 180 out, they would both in fact be in phase, and, thus, reflection would be doubled instead of eliminated. To achieve that you need a half-wave coating. Zaereth (talk) 22:03, 7 January 2016 (UTC)
thread_title:  Figure  

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thread_title:  External links modified 

message: There is a revert concerning the use of AR coatings other than interfaces with air.  It would seem that they could be used with water-glass or oil-glass interfaces with immersion microscopy, but I don't see any evidence of the use. Even more, in confocal microscopy, where light is coming in through the same lens, and the reflection could be more problematic. As I have no evidence of such use, I won't change it, but it would be interesting to know if there were some uses other than air. Water at 1.33 is probably different enough from glass to make a reasonable reflection. Gah4 (talk) 07:17, 1 August 2017 (UTC)
replies: text: I've never heard of it, but that doesn't mean they don't exist. Most dye lasers use Brewster's angle rather than coatings to reduce reflections. Some microscopes use index-matching fluids, that equal the refractive index of the glass, to eliminate reflections. Liquids generally have a refractive index close to, or sometimes greater than glass or plastic substrates, so the normal reflection is usually much lower tan the air-to-glass interface. (Cassia oil has probably the highest refractive index of any natural liquid, of 1.62, nearly matching that of lead glass, but most oils are in that 1.4--1.5 range.) For these reasons it is unlikely tat the benefits of such a coating would outweigh the cost. Zaereth (talk) 08:40, 1 August 2017 (UTC)
replies: text: Reminds me of some year ago when I was trying to find high index liquids.  The ones I remember are iodized hydrocarbons.  It seems that diiodomethane is 1.741, tri and quad might be higher. But I suppose that isn't natural. It might be that sometimes there is a need for water, but otherwise it does seem that coatings are usually used with air interfaces. Gah4 (talk) 09:29, 1 August 2017 (UTC)
replies: text: Yeah, the refractive index is linked to the polarizability of the substrate, and that is also linked to the cohesive forces that turn a liquid into a solid. I've seen artificial liquids that go above 1.8. For relatively low-cost, natural liquids, though, it's mostly the essential oils that go higher than 1.5. (Cedar oil is 1.52, clove oil is 1.53, anise oil is 1.56, cinnamon oil is 1.58, etc...) The drawback is that they often leave whatever you're testing with a very strong odor, but the difference is typically a few hundred dollars per ounce. On the other and, most solvents, like ethanol, methanol, isopropyl, hexane, cyclohexane, etc., have indices very close to that of water. These are often used in dye lasers, yet I've never seen specialized coatings for them. Zaereth (talk) 09:52, 1 August 2017 (UTC)

text: Hi Gah. I reverted it. My main concern was to keep the explanation of the simplest interference coating simple and clear, for readers new to the concept. I don't doubt that glass-liquid AR coatings exist, but this is at best an uncommon application. The text now does mention that the described coating is for use in air.--Srleffler (talk) 11:56, 1 August 2017 (UTC)
thread_title:  Air 

message: You just added "It also had an aesthetic effect in the history of photography," to the lead paragraph. I removed it. Can we say something more specific? Saying that it had "an aesthetic effect" doesn't tell me anything useful. I also don't understand what it means to say that something had an aesthetic effect "in the history of" something. Did it make the history books prettier? I agree that photography was a glaring omission (pun intended), and that we should say something about the effect that this technology has had on photography, but can we say something that is clear and understandable and specific?--Srleffler (talk) 23:43, 27 December 2021 (UTC)
thread_title:  It also had an aesthetic effect in the history of photography.