Talk:Holography

Merge from Rainbow hologram

Rainbow hologram should be merged here, being that Hologram redirects here, and the average joe curious about holograms will be looking for the type consumers see every day, which is currently only mentioned here in a fleeting Overview sentence. Many applications of the Rainbow type are listed here, but the technology description entirely skips over them, making the whole article rather cryptic in its present state (in fact I'm willing to bet many people have been reading this page, mistakenly thinking they were reading a description of the technology that produces the holograms they are accustomed to seeing). The disambiguation link at the top of the page isn't immediately obvious as the place where people looking for "run-of-the-mill" holograms should look. Equazcion ^(talk) 01:05, 22 Aug 2011 (UTC)

Sounds like a sensible proposal. Needs some thought to integrate it coherently. Epzcaw (talk) 00:20, 23 August 2011 (UTC)

It shouldn't be too difficult as long as we have someone who understands the commonalities between the two (not me, but from browsing this page, perhaps you). Simply create subsections under the "How they work" header for each, explaining the differences, and leave the commonalities as they are, more or less. Applications of both are already listed here, and the Overview is easily expanded to include a short summary of the Rainbow type. Equazcion ^(talk) 01:10, 23 Aug 2011 (UTC)

I'm on holiday at the moment, but will look at it when I am home next week, if someone else has not done so. need to look at my books....Epzcaw (talk) 02:25, 23 August 2011 (UTC)

I have now had a look at this. I am proposing to replace the section "Reconstructing and viewing the hologram" with "Reconstructing and viewing the holographic image" which I have drafted at User:Epzcaw/holographic reconstruction. Comments/constructive criticism welcome before I make the change. I will add a reference to Hariharan, which covers some of the material, but most of the material which I copied from the Rainbow hologram article is unreferenced. I will try and find some in the next few days, but would welcome input, particularly for these:

• Stereopsis and horizontal motion parallax, two relatively powerful cues to depth, are preserved.

• The holograms found on credit cards are examples of rainbow holograms.

• These very common holograms are technically transmission holograms mounted onto a reflective surface like a metalized polyethylene terephthalate substrate commonly known as PET.

I think it is worth having a separate article describing in detail how rainbow holograms work, and will do something on this if no-one else does so in the next few weeks. The current article has no verifiable sources, and should probably be deleted as it stands, but I'm not sure what the protocol for this is. I will add a note in the 'Discussion' section, and see what happens.

Epzcaw (talk) 17:42, 28 August 2011 (UTC)

I have now amended the article as above. I will add to the Rainbow hologram soon. Epzcaw (talk) 23:29, 31 August 2011 (UTC)

I have now expanded the Rainbow Hologram article to include a moderately detailed explanation of how they work, so don't think the merge is necessary now.Epzcaw (talk) 14:46, 19 September 2011 (UTC)

Revamp

I made some changes to the "how they work" section. The explanation geared towards laymen that was once present seemed to have been replaced by an excessively technical explanation that would make the average reader's head spin.

A few points:

• Noting the argument about the word "random" above, it is still misleading to say that the pattern is actually random. Regardless of the way the source material is worded, a truly random pattern can not contain information, and therefore a hologram's surface pattern is not actually random. Mathematically, technically, it could be said to be random, given that it is produced by the inevitable chaos of diffuse objects' surfaces -- but the pattern must have a degree of predetermined structure, even one that is not immediately obvious, in order for it to actually represent something and be of some use. The term "random" connotes to a reader that the pattern is entirely determined by chance, and is therefore meaningless and useless in producing anything meaningful, when it is actually not any of those things. Rather than confuse the reader by essentially saying "we record holograms by making a useless recording of completely random specks," it is more useful to leave the brutally-technical rap to another section.
• Which brings me to my next point. There was already a basic separation between "here's the explanation" and "here's the technical explanation", though not named as such; I have now named them as such, and I think it would be useful to maintain this separation in the future. Wikipedia is for laymen and specialized techies alike, so for subjects like this, where the two must be served in different ways, it behooves us to do so.
• I expanded the simplified section significantly in order to more fully explain the process. The word "laser", for example, was conspicuously missing, as were many other crucial aspects necessary for readers to comprehend what's going on. Feel free to make corrections, but kindly remember that the priority in that section is easy understanding by those without a degree in theoretical physics, and therefore certain confusing details that might lend accuracy may still not be appropriate for that section. Use judgement thusly.
• The line at the top of the "how they work" section seems to be announcing the source material, which isn't necessary. The source description should be limited to an inline reference tag or to a separate references section at the bottom of the article. I moved it into a ref tag for now.
• Talk page sections, as article sections, are always posted as ==level-2 headers==, FYI. Wikipedia tradition, but a uniform one. =level-1 headers= are only used in certain rare instances.

Thanks. Equazcion ^(talk) 10:01, 25 Aug 2011 (UTC)

This is definitely a necessary improvement in the article.

A few suggestions:

Omit 'A rudimentary description' - just call it 'How holography works'.

Put 'Recording a hologram' before 'Holography vs photography'.

Mention that other media can be used to record as well as photographic film.

Epzcaw (talk) 14:40, 26 August 2011 (UTC)

I think the 'How holography works' section needs a further few amendments.

The requirements for a reference beam should be mentioned at the beginning

It should be made clear that the complicated arrangement of multiple mirrors and beams-splitters is not necessary for making a hologram - a point made by 71.218.130.13 in the disucssion unded the heading 'Hologram Kit'.

I have created a modified version at user:epzcaw and would welcome comments. Epzcaw (talk) 16:43, 4 February 2012 (UTC)

Further re-vamp

I think the article needs some re-structuring and re-writing. It is repetitive in parts, and also has some missing elements. Things are not necessarily in the right order. I have written quite a bit of the article, so much of this is my doing.

I will work on this on a user page, and when finished, invite comments and criticism. Epzcaw (talk) 17:28, 1 September 2011 (UTC)

I have re-written the article up to section 5, "Applications". It can be found at User:Epzcaw/holography. Comments, corrections and constructive criticism welcome.

All of the major changes relate to my own contributions. I have changed the phrasing in some other places, re-ordered some material, and made small additions or removals.

I would like to delete the "Holography in Fiction" and "Things that are not holograms" sections - views welcome on this.

I propose to remove the "Holoprinters" section since that is unsupported by any references and has had a notice to this effect for a long time.

There are still many topics which have not been covered and will look to this in the future.

I hope to write an article doing detailed mathematical description of holography, and the mathematical bit could then be removed from here.

Epzcaw (talk) 10:32, 15 September 2011 (UTC)

Amended version now substituted. Section on Holoprinters now removed Epzcaw (talk) 08:25, 18 September 2011 (UTC)

Lazer?

Is holography not also the study of lazers?Peace is a lie (talk) 18:29, 29 September 2011 (UTC)

Found your question!! The answer is no - optical holograms are not possible without lasers, but lasers exist independent of holography.

Holography is a very clever way of racording light fields.

Lasers are light sources with specific properties, the most important of which if probably the very narrow bandwidth (i.e. very close to a singel wavelength or colour) and secdonly (probably) the very small area into which they can be concentrated.

I hope this helps. Epzcaw (talk) 21:28, 29 September 2011 (UTC)

Hologram kit

There is a hologram kit on the market now which might spur an update to this article. I know we don't want to endorse a particular product or serve as an advertisement (so I won't give the name here - it is easily available by Googling), but it is interesting how they found a couple of clever ways to put holograms into the hands of anyone, not even a hobbyist. The "kit" can be configured for transmission or reflection holograms.

The clever bits (to me anyway) are 1) using the natural spread of a standard red laser diode without a lens to provide both object and reference beam without beam splitters/mirrors, or other optical components and 2) self-developing film (glass plates) that expose and develop with red light, so there are no additional processing steps needed. Secondarily, they make a fixture that insures the correct angles on everything and doesn't require access to a sand table or whatever. The whole process is very error-tolerant, as explored in this article in The Physics Teacher. (that is on this company's website, the original source is available, but you need to be a subscriber)

How does this affect this article?

• In the first paragraph of Recording a Hologram, some of those items are obviated (though obviously the principles behind them are not). Additionally, while all the caveats about movement remain true, the implication from the article that this type of stability is difficult to achieve and requires special equipment to do so probably now overstates that difficulty. Without optical components , vibrational and thermal stability is substantially easier to achieve. Setting the fixture on a sink worked just fine for me.
• In Holographic Recording Media section, I am not sure what the film in this kit is - it appears to be a self-developing emulsion on one side of a plate of glass with a polycarbonate coversheet So that table might or might not need to have something added.
• Additional information could be added to the Hobbyist Use section indicating that an all-in-one kit with an error-tolerant process is available.

I am not a Wiki author, so I am not sure where to go from here. I don't want to mistakenly cross a line into endorsement, so I am wondering if someone with more Wiki experience could guide me, or better yet, take this and run :) --71.218.130.13 (talk) 20:53, 6 January 2012 (UTC)

I would be happy to have a look at the information about this and see how it relates to what is in the Wiki article. I don't think it would be in breach of Wikipedia principles if you were to give the name of the company. It was not obvious from a quick Google search what company you meant. Epzcaw (talk) 14:47, 10 January 2012 (UTC)

I have now read the article in Physics Teacher. Comments:

Stability problems are much less if the object is small, and is located very close to the holographic recording medium as is the case here. This is not new in itself - in the early 1980s, the Open University (UK) was sending out kits to make holograms at home using the same sort of arrangement. It is when you want to make holograms of larger objects that you need more powerful lasers, and better stability. I will ass something to this effect in the article.

No information is provided about the composition of the recording material used - I think we would need more detail to add this to the table of recording materials. Epzcaw (talk) 16:52, 10 January 2012 (UTC)

Thanks for taking a look Epzcaw. The company is Litiholo. To me the difference from previous kits (and the thing that might merit adding something to the holography article) is the combination of cheap LED laser (I'll bet that 1980's kit required you to have a He-Ne laser), no optics, and self-developing error-tolerant film. Even a tyro like me made a holograph on the first try. When I read that section about hobbyists and green laser pointers, I thought to myself, "But now it is even a LOT easier than that!" If you are thinking about making a holograph and you run into the very detailed (and imposing) instructions available on the internet about the optics and optical table, vibration isolation, film, film development/shrinkage, etc. it sounds like something only a University could do. Thanks again!--71.218.130.13 (talk) 21:44, 10 January 2012 (UTC)

I have done some amendments to the 'Items required' which take on board your comments

Now is your chance to become a Wikipedia editor if you would like to make further changes. Anyone can do it. It is worth looking in the HELP section (left of page) to get some guidance on what you should and shouldn't do. One of the most important requirements is that anything you say must be supported by reliable reference sources. If you get it wrong, it won't be long before someone says so!!

It is also good practice to discuss changes in the 'Talk' page before doing them - you have already done this. Epzcaw (talk) 18:13, 11 January 2012 (UTC)

That looks great to me Epzcaw! I wish the spec sheet on that film had more information about how it worked - that would clarify if anything needed to be added in the film section.

I am a writer and researcher by trade (though not in physics) so properly sourcing and writing is no problem. But that also leaves me hesitant to just go change stuff!

How about this added to the bottom of "Hobbyist use"

Holography kits with self-developing film plates have now entered the consumer market. The kits make true holographs and have been found to be fairly error tolerant., bringing holography into reach of even the most casual hobbyist.--71.218.130.13 (talk) 08:05, 16 January 2012 (UTC)

Fine but maybe leave out the 'true'. Also, I think the last sentence is a bit too 'advertisey'. Maybe something along the lines of 'and enable holograms to be made without any other specialised equipment'. Epzcaw (talk) 00:53, 17 January 2012 (UTC)

Yep, I am with you on that. OK, I went ahead and made the changes - see what you think! Thanks for the guidance!--71.218.130.13 (talk) 08:46, 19 January 2012 (UTC)

References

Light-Field Camera and Holography

Perhaps someone with more physics than I would clarify: as I understand it, light-field cameras (e.g. http://en.wikipedia.org/wiki/4D_light_field) capture white light direction and intensity. Heretofore, holograms have been the only way to do that. Would a light-field photo be considered "holographic" in that it digitally captures the same information as the laser-based hologram? (Albeit quite differently and with lower resolution.) Similar effects can be rendered from light-field cameras as holograms (e.g. http://www.lytro.com/living-pictures/2326 you can change point of focus, use lenses/refracting materials in a light-field photo to change focal plane, and at least a modicum of parallax). However, while all the information is there, I have yet to see it rendered into a 3-D image without something like an anaglyph. So I guess my question boils down to, "What does holograph 'whole drawing' mean?" Capturing light direction and intensity (which would seemingly include light-field) or doing so with coherent light interference fringes on film and recreating the 3-D image from such (which would exclude it). --71.218.130.13 (talk) 21:34, 6 January 2012 (UTC)

In my opinion (but could be wrong!!), I think this is a matter of usage. I think most people involved in 'conventional' holography would consider the term to relate purely to the process of recording with interference and reconstructing with diffraction. However, specular holography does not involve either of these but still uses the word 'holography' So if someone involved in making or using these cameras decided to call it 'holography', I have no doubt there would be objections, but if the term gained general usage, it would then become 'correct'.

People have used the term 'TV holography' for what is more generally known as Electronic speckle pattern interferometry although there is no 3-d reconstruction involved. The term has been used in published journals so presumably must be deemed to be a correct usage.

So, as with any word, it ultimately means what people want it it mean. But which people.....Epzcaw (talk) 14:59, 10 January 2012 (UTC)

Interesting - specular "holography" doesn't involve recording light direction at all, it is more like an optical illusion of depth. I guess I would personally object to calling that a hologram, it is more of a kind of stereogram. It doesn't capture a "whole picture." (Though on second thought, it emulates ray traces, so maybe.) Light field cameras are pretty new to the scene so usage is in flux. I would say that laser holograms and light field pictures share more in common with each other than either does with a scratch or specular "holograph" or stereograms. In common usage the term "holograph" is muddled. In common usage, all 3-D pictures are not called holographs (e.g. anaglyphs, lenticulars, stereograms) but some things are called holographs that are really different from each other and don't necessarily capture the "whole picture" (e.g. laser holographs, specular holographs, the CNN "holograph" camera effect).--71.218.130.13 (talk) 22:07, 10 January 2012 (UTC)

I did think of removing the reference to specular holography, but decided against because I couldn't really justify doing so except as my own opinion. One of the references provided in the main article about specular holography is from an article from the proceedings of a SPIE conference which I think would be accepted as a reasonably reliable source (though it's not a peer-reviewed journal).

Unless light-field camera images have already been described as holograms in appropriate reference sources, then the inclusion of this description in Wikipedia is likely to be attacked and removed. The goal of an WP article is "to create comprehensive and verifiable encyclopedia articles about topics" and WP is "not a publisher of original thoughts".

Maybe a matter to be discussed in the light-field camera page? Epzcaw (talk) 17:28, 11 January 2012 (UTC)

References

History/date of invention

Hello,

I am not an expert, but have found a contradicting information.

I thought that the pioneering work on holography was done by Mieczysław Wolfke in 1920 and so he should be named the inventor of this method. It was first realized later due to technological issues.

The article says: "Holography was invented in 1947 by the Hungarian-British physicist Dennis Gabor (Hungarian name: Gábor Dénes),[1][2] work for which he received the Nobel Prize in Physics in 1971. Pioneering work in the field of physics by other scientists including Mieczysław Wolfke resolved technical issues that previously had prevented advancement. The discovery was an unexpected result of research into improving electron microscopes at the British Thomson-Houston Company in Rugby, England, and the company filed a patent in December 1947 (patent GB685286). " making it unclear whether Wolfke's work was before or after 1947.

A separate article on Mieczysław Wolfke, states that his development on holography was done in 1920 (and not in 1947 by Dennis Gabor), so one of the two articles is not telling the whole truth or is not precise. Am I right?

Kind regards, WK — Preceding unsigned comment added by 86.25.205.143 (talk) 02:27, 26 January 2012 (UTC)

Gabor is credited with the invention of holography in all the sources I have seen including the Nobel Prize for Physics committee (see mian article for a reference). The Wikipedia article on Wolfke gives gives no reference sources to justify its statement that Wolfke worked on optical holography. For example, according to Hariharan , “The roots of holographic imaging can be traced back to work by Wolfke [1920] and Bragg [1939, 1942] in x-ray crystallography.“ and “The similarities of Gabor’s experiments to Bragg’s x-ray microscopes are evident, but the differences are also extremely significant”.

If there is evidence that Wolfke did invent optical holography, it would need to be supported by reliable references sources. It seems a bit implausible (but not impossible) that Gabor has been credited all these years with the invention of holography, and awarded a Nobel prize for this, if indeed it had all been done 30 years before by someone else.

The WP holography article is, however, rather misleading, and I will alter it. I will also add a request in the Wolfke article for the comments about his work on holography to be supported by some evidence, or removed, in accordance with Wikipedia policy on citiation of sources.

Well spotted! Epzcaw (talk) 11:22, 28 January 2012 (UTC)

References

Gabor was physicist or electrical engineer?

the page about Gabor says he was electrical engineer, not a physicist — Preceding unsigned comment added by 62.1.244.19 (talk) 19:44, 14 March 2012 (UTC)

He trained as an electrical engineer, but given he was awarded the Nobel prize for Physics, it is not unreasonable to assume that he was also a physicist! Epzcaw (talk) 20:17, 16 March 2012 (UTC)

Wrish one?

The text says: Total Recall (1990 film), the main character uses a device, similar to a wrisch, to produce a hologram of himself and deceive his foes. Is "wrish" a typo for wrist watch?P0M (talk) 04:45, 27 March 2012 (UTC)

Kinebar image?

I don't think we should use the Kinebar image in this article (under security) because the Kinegram image displayed isn't actually a hologram. To quote the article on Kinebars, "Note that a Kinegram is not a hologram; a Kinegram displays a flat diffractive design, while a hologram is a diffractive device that displays a three-dimensional image."

FinrodFelagund9 (talk) 19:32, 12 April 2012 (UTC)

I go along with this. Maybe remove it in a few days time if not one presents a contrary view? Epzcaw (talk) 16:38, 14 April 2012 (UTC)

Now done Epzcaw (talk) 16:10, 6 May 2012 (UTC)

Tupac Hologram

A "hologram" of Tupac Shakur appeared at the cocahella music festival. http://www.huffingtonpost.com/2012/04/16/tupac-coachella-hologram-snoop-dre-video_n_1427925.html

Reference to the Tupac hologram should be removed as it's not really a hologram but a usage of Pepper's Ghost (even listed on the Pepper's Ghost page): http://arstechnica.com/science/news/2012/04/tupac-hologram-merely-pretty-cool-optical-illusion.ars

Tupac was not a hologram. The company that did the projection even states they only project hologram illusions

http://www.avconcepts.com/holographic-projection/ http://www.mtv.com/news/articles/1683173/tupac-hologram-coachella.jhtml

Yes, it should be mentioned as a Peppers Ghost. Or in http://en.wikipedia.org/wiki/Holography#Things_often_confused_with_holograms 67.49.102.91 (talk) 06:09, 17 April 2012 (UTC)

Hatsune Miku Concerts Not Pepper's Ghost

The Vocaloid concerts featuring Hatsune Miku amongst others has never used Musion Eyeliner or any Form of pepper's ghost. These concerts use a much more simple method of rear projection onto a semi-transparent "DILAD" screen. — Preceding unsigned comment added by 68.184.109.8 (talk) 20:56, 20 April 2012 (UTC)

Could you elaborate this a bit more? "Rear projection onto a semi-transparent screen" seems to me pretty much the definition of Pepper's ghost. --Danh (talk) 10:53, 23 April 2012 (UTC)

Overly pedantic intro?

A layman reading this, "...so that when an imaging system (a camera or an eye) is placed in the reconstructed beam, an image of the object will be seen even when the object is no longer present."

sounds kind of ridiculous, esp the "will be seen even when the object is no longer present" part. Photography could be described the same way... to a bushman perhaps. It's like defining an automobile as a metal box that you sit in and after turning a key and moving some controls around, you get out and you are in a different place than you were before.

97.122.207.171 (talk) 04:12, 12 May 2012 (UTC)

I think you have a point but it is not easy to come up with something clearer which is also accurate. How about

Holography (from the Greek ὅλος hólos, "whole" + γραφή grafē, "writing, drawing") is a technique in which the light scattered from an object is recorded in such a way that a three-dimensional image of the object can be observed.

One problem is that not all holograms are recordings which produce three-dimensional images, for example holographic elements, computer generated holograms. But I guess it is ok to start with the first type of hologram which is what most people think of a hologram as being.Epzcaw (talk) 19:44, 10 July 2012 (UTC)

Or even

Holography (from the Greek ὅλος hólos, "whole" + γραφή grafē, "writing, drawing") is a technique which enables three-dimensional images to be made.

Comments? Epzcaw (talk) 15:01, 11 July 2012 (UTC)

Or

Holography (from the Greek ὅλος hólos, "whole" + γραφή grafē, "writing, drawing") is a technique which enables three-dimensional images to be made. It involves the use of a laser, interference, diffraction, light intensity recording and suitable illumination of the recording.

The difficulty is that the simpler you make the definition, the less information it provides, and the more acurate you try and make it, the more complex/pedantic it becomes. Epzcaw (talk) 18:26, 14 July 2012 (UTC)

Holograms and "holograms"

The terminology of holograms has become a hairy subject in modern times - the popular SF media has plagued us with wrong usage of the word for very different technologies, mostly the spatial projections which are neither holograms nor should be possible using holography. I'd say the biggest culprit here is Star Trek (although perhaps Star Wars started the trend first?) which absolutely incorrectly calls their 3D projections "holograms", although their technology is quite clearly described as obviously NOT holography - it is explained as a combination of forcefields and directly projected photons (not depending on light interference effects), placed at arbitrary positions in space. Also those projections are TANGIBLE, something that doesn't seem doable with holography, neither now nor then.

To add insult to injury, SF fans have got the habit of calling every spatial 3D projection they see - "holograms", even when it's not presented as such which adds to the confusion - they too are popularly referred to as "holograms" as can also be seen in this article's list of holography in fiction! So, it would be nice if someone reviews the list and tags or removes the items you know are wrong. I've already tagged a few, but I'm not familiar with some of them (e.g. animated series) or not really sure how exactly is it called in-universe (e.g Stargate). Please help in clarifying the confusion if you can. Thanks, Arny (talk) 09:13, 12 August 2012 (UTC)

I agree with your comments but think it would be quite difficult to dispute entries here unless you have a reasonable understanding of what is or is not holography, and have seen the movies or read the books. Not something I am planning to do!! And even then, you would probably get disputes about which items satisfy the criteria. Citations in this case simply involve giving the name or movie. Books could perhaps be contested by quoting from the books, but in the case of movies, it is hard to see how a definitive view could be reached.

I have already said I would prefer to see this as a separate article (and other people agreed but I think the relevant section of the discussion has now been archived) but no-one seems to have either the will or conviction to do so. Epzcaw (talk) 16:57, 13 August 2012 (UTC)

Suggested merge of holographic display page

The "Holographic display" page consists of two sentences with no references. It needs either to be expanded and references added, or deleted. It should not be merged with the Holography page in its current form]]. Epzcaw (talk) 22:40, 22 August 2012 (UTC)

It needs expansion and references but it should at least be mentioned in this article and not only deleted. --134.109.227.112 (talk) 21:38, 29 August 2012 (UTC)

Without references, the article does not follow Wikipedia criteria. I have put an unreferenced tag on it which means that it will be deleted in due course unless references are added. Epzcaw (talk) 14:30, 30 August 2012 (UTC)

References have been added, but neither "holographic display" nor "Electroholography" are explained in the article so there is nothing to merge.Epzcaw (talk) 03:09, 8 September 2012 (UTC)

Nobody has made a case for this merge - the article @holographic Display' contains no information. I am therefore removing the suggested merge link. Epzcaw (talk) 13:13, 19 September 2012 (UTC)

Holography in fiction/popular culture

I think it is now time to take the bull by the horns, and remove this section from the "Holography" article, particularly in the light of the recent comment.

I propose to create a new article called "Holography in Fiction" and move all the content to the new page. This can then survive or not on its own merits, rather than cluttering up a serious article about holography, unless people strongly object to this. Epzcaw (talk) 18:24, 22 September 2013 (UTC)

Go for it, I also don't see any other way to keep the section from growing indefinitely. --Danh (talk) 21:16, 22 September 2013 (UTC)

I have now created a new article Holography in fiction and moved all the content, plus the comment about "trivial or minor references to popular culture" to teh new article. Epzcaw (talk) 13:51, 29 September 2013 (UTC)

Poor grammar: http://en.wikipedia.org/wiki/Hologram#Holography_in_fiction 174.45.224.10 (talk) 10:53, 19 May 2014 (UTC)

Vague phrasing?

Hi, I'm currently browsing this article and some parts I find difficult to understand. One example: the attached graphic "Recording a hologram" puts the viewer on the other side of the photographic plate. Which, imo, indicates that the graphic shows a transmission hologram. However, this paragraph: "Reconstructing and viewing the holographic image When the hologram plate is illuminated by a laser beam identical to the reference beam which was used to record the hologram, an exact reconstruction of the original object wavefront is obtained. An imaging system (an eye or a camera) located in the reconstructed beam 'sees' exactly the same scene as it would have done when viewing the original. When the lens is moved, the image changes in the same way as it would have done when the object was in place. If several objects were present when the hologram was recorded, the reconstructed objects move relative to one another, i.e. exhibit parallax, in the same way as the original objects would have done. It was very common in the early days of holography to use a chess board as the object and then take photographs at several different angles using the reconstructed light to show how the relative positions of the chess pieces appeared to change." says that regardless of the hologram type, the viewer is located in the reconstructed beam, which would be the location of the referene beam. Isn't that only correct for reflexion holograms? Imo, a lot of the paragraphs seem to be very vague so I'm really not sure. — Preceding unsigned comment added by 95.130.160.193 (talk) 10:35, 16 October 2013 (UTC)

These Are Not Holograms

Hologram should not redirect to this page, as there should be a page about holograms, of the ilk in science fiction, which has been invented in real life. I came onto Wikipedia to find a page on that. I want to know the name of the man who invented actual holograms (via projecting the images onto tiny water droplets), because I want to name a character after him. But, instead, you guys rigged Wikipedia to point me to this... Thank you, for being a nuisance.--174.19.244.195 (talk) 09:54, 9 April 2014 (UTC)

Not knowing the difference between a hologram, and a holograph is like not knowing the difference between a pentagram, and a pentacle. It's a common problem, but that doesn't make people calling things the wrong word right.--174.19.244.195 (talk) 09:56, 9 April 2014 (UTC)

"Projecting the images onto tiny water droplets" would be a form of 3D display, not a hologram. The reason you got to the wrong page was because you failed to enter the correct search term. First of all read this article to find out what a hologram is, it will also tell you what it is not, and then find out what the display technique that involves "projecting the images onto tiny water droplets" is actually called and search for that. You may have better luck.86.148.103.129 (talk) 09:09, 30 October 2014 (UTC)

Microsoft HoloLens

Microsoft announced their HoloLens glasses a few days ago. Since it are augmented reality glasses and doesn't involve holography (except for the marketing part), I would propose to add it to the list of 'Things often confused with holograms'. Jerisson (talk) 21:41, 26 January 2015 (UTC)

You have no way of knowing that HoloLens doesn't involve holography. There are quite a few reasons to believe it does involve holography, including direct quotes from the project lead that the device has "holographic lenses". Moving into original research territory, hands-on reports with the HoloLens suggest that it does not focus all virtual objects at a fixed distance which implies optical technology that likely involves holography. I don't feel the need to add this information to Wikipedia at the moment as it is somewhat speculative and based on original research, but it would be absurd to add the HoloLens as an example to this section on the basis of the unverified sentiment that it's a misnomer. 128.189.233.115 (talk) 02:55, 28 February 2015 (UTC)

There seems to be a consensus that the virtual objects are augmented reality and not true holography. I did not consider the possibility of focusing on virtual objects, or simulating its effects, back then. Indeed, I cannot say for sure that the HoloLens does not involve holography. But from what I know electronic color (RGB) holograms (for example NICT's display http://spie.org/x107477.xml ) still requires a lot of room and there is still a lot of research going on to get a decent quality. However, focusing (accommodation) does not require holography, but can be achieved by much cheaper and easier to implement technologies such as lightfield displays (lenslet based, multiple LCD layers, ...). These displays are often considered as a much more feasible solution than holography for this kind of 3D video. Headmounted lightfield displays that allow the eyes to focus on virtual objects have already been presented. Knowing this, it is reasonable to assume that the HoloLens might, at most, use lightfield technology.Jerisson (talk) 22:35, 1 March 2015 (UTC)

Viewing broken holograms, please be more specific.

> a hologram can be broken up into small pieces and each one will enable the whole of the original object to be imaged. One does, however, lose information and the spatial resolution gets worse as the size of the hologram is decreased — the image becomes "fuzzier". The field of view is also reduced, and the viewer will have to change position to see different parts of the scene.

What happens, when the hologram plate is not broken per se, but a large hole (oval or rectangular) is cut into it? I would assume the cut-away part will behave as a lower resolution version of the full hologram. However, what happens to the mutilitated whole plate? For example, if the hologram depicted an Earth globe and a part of it showing Australia was cut off? Please clarify this aspect! Thanks in advance! 92.52.225.75 (talk) 20:30, 2 June 2015 (UTC)

As you say, if a small part was cut out, it would still enable you to see the whole globe. Your second question does not have an answer however, because no particular part of the hologram represents Australia. Every point on the object sends light to every point on the holographic recording, so Australia is represented all over the plate. This is why the whole image can be viewed using any part of the hologram. Perhaps a useful way of understanding this is to imagine the hologram as being a window through which you can view the object. if you block off part of the window, you can still see the object, except when you try to look through the blocked off bit. Hope this helps. Epzcaw (talk) 15:49, 18 July 2015 (UTC)

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Physics of broken hologram

There should be a section dedicated to explaining the physics of this phenomena, since no-one seems to know, and this paragraph has no refererences.

From the article:
"Since each point in the object illuminates all of the hologram, the whole object can be reconstructed from a small part of the hologram. Thus, a hologram can be broken up into small pieces and each one will enable the whole of the original object to be imaged. One does, however, lose information and the spatial resolution gets worse as the size of the hologram is decreased — the image becomes "fuzzier". The field of view is also reduced, and the viewer will have to change position to see different parts of the scene."

Artificial holography

The current Wikipedia definition for holography states that it should be a "physical recording of an interference pattern which uses diffraction to reproduce a three-dimensional light field, resulting in an image which retains the depth, parallax, and other properties of the original scene". This seems to exclude computer-generated holography and any other artificial holographic imagery that may exist. The current Wikipedia definition of Holographic display simply states that it is "a type of display that utilizes light diffraction to create a virtual three-dimensional image" and thus could arguably include artificial holographic imagery. Can the current holography definition be adjusted to also include artificial imagery, or can it be more clearly differentiated form artificial holography?

I suppose this is like comparing photo-realistic CGI to authentic photography. However, since most people already seem to think of a hologram simply as a 3D image, I believe this desperately needs disambiguation/clarification. Maybe the "physical recordings" will be commonly named holophotography (and possibly holocinematography?) in the future? Joortje1 (talk) 07:38, 16 March 2020 (UTC)

This is a valid point. I will think about how it could be re-phrased and publish it here first. Epzcaw (talk) 15:28, 9 August 2020 (UTC)

I've written an amended version of the Introduction. It is on my sandbox page. Comment/ amendments welcome. Epzcaw (talk) 11:20, 13 August 2020 (UTC)

I'll add detailed comments to the sandbox talk page as and when I get time. I'm not sure I really understand Joortje1's comment above: it's inconsistent about "artificial imagery". A CGI image of an imaginary space alien displayed on a computer monitor doesn't actually have anything to do with photography. Likewise a CGH of an imaginary space alien is a synthetic construct that's meaningless until you create the physical plate to display and view the image. Given the widespread confusion about what holography actually is, I think it's more important for the article intro to stress that we're using the reference beam to record the phase, (rather than just any 3-d image). The phrase "computer-generated holography" is already explicit that it's using a computer to do something that otherwise doesn't need one, isn't it? Louis Knee (talk) 16:25, 28 August 2020 (UTC)

Louis Knee - I've amended my introduction to take your comments into account at my User:Epzcaw/sandboxpage. Further comments welcome. Epzcaw (talk) 18:54, 13 September 2020 (UTC)

Hi Epzcaw - I left comments at the sandbox talk page... Louis Knee (talk) 21:13, 15 September 2020 (UTC)

Change the name to Optical Holography

Most people think of holography as purely an optical process. To ensure that the article covers only this,I suggest that the name is changed to Optical Holography.

Someone may want to do a more general article on holography which could link to articles about the various forms of holography. There is already an article on Electron HolographyEpzcaw (talk) 10:05, 25 September 2020 (UTC)

'FMCG industry' sub-heading within the article does not have an editing pencil icon next to it

I am confused as to why the 'FMCG industry' sub-heading contained within the article does not have an editing pencil icon next to it but the others do. Xboxsponge15 (talk) 16:10, 20 November 2020 (UTC)

Introduction

This has become very long and muddled. I've had discussions with other authors about how it should be changed, but we did not get to a final agreement, so I've done it myself. I've written a new much shorter introduction. I've moved nearly all of the previous introduction content into the next section, and re-ordered it to make more sense. This section now needs some work as it is a bit rambling. Epzcaw (talk) 09:25, 28 April 2021 (UTC)

Too technical template

I propose to address this issue by moving the detailed physics discussion to a separate article.

I've written this article Draft:Physics of Optical Holography which is now awaiting approval. Epzcaw (talk) 10:22, 28 April 2021 (UTC)

This article has now been published as Physics of Optical Holography where I have moved the mroe technical details and added a more detailed physical description. I will now remove the ""Too technical " template. Epzcaw (talk) 09:49, 12 July 2021 (UTC)

Overview and History

I've amended this to make it more coherent. I've mainly moved bits either around or to other parts of the article. May still be too detailed.Epzcaw (talk) 19:37, 13 May 2021 (UTC)

Remove recent contribution is it is not relevant and has no references

This has been added but it containts no references, and is not actually about holography but about "holographic illusions"

Simple holographic art can be made by overlaying 3D color transparency layers produced from a computer printer. Thickness of transparency and spacing between layers produces the final piece to the holographic illusion.

I will remove it in a few days if it is not amended.

I agree with your removing it - but ironically this is exactly what we used to do back when I was doing origination of embossed holograms! (It was to give us and the customer an idea of what image/effect was intended - no-one was pretending this was anything like a hologram per se.) Louis Knee (talk) 12:48, 2 September 2021 (UTC)

THat's very interestting! I would have maybe moved it to the False holograms section if it had included a reference. Maybe you have one? Epzcaw (talk) 08:29, 3 September 2021 (UTC)

Re. hologram origination: unfortunately not - the most likely place I can think of would be some "reminiscence" article in one of the holography newsletters. The closest I can find is the discussion of artwork for 2D-3D images in the "Embossed Holograms" chapter of Saxby, but even that is about preparing it for exposure, rather than mounting it up for QA/customer approval.

But the problem with that inserted paragraph is the use of "holographic" and the usual confusion that "holographic" = 3-d; using a stack of transparencies to create a parallax effect is a valid and established technique: e.g. Disney used it to create parallax between the foreground and background in tracking shots (I've not got a reference for that either :( At some point I'll go have a look if the Fantasia DVD has a "making-of" on it!) Louis Knee (talk) 16:21, 3 September 2021 (UTC) No, but the "Roy Disney Intro" on the Fantasia 2000 DVD includes footage of loading the glass plates into the mounting frames and the resulting motion parallax effect. Louis Knee (talk) 23:16, 3 September 2021 (UTC)

References

Mathematics

I think there needs to be a section on the Mathematics of Holography. The word 'Math' doesn't even appear in the article. Given the close relationship between Holography and many kinds of mathematics and mathematical problems. CessnaMan1989 (talk) 18:48, 14 October 2021 (UTC)

The mathematics is all laid out in the Physics of optical holography article. What do you think is missing from there? Louis Knee (talk) 16:07, 15 October 2021 (UTC)

Perhaps more linking and clearer references to that article are in order. CessnaMan1989 (talk) 16:13, 15 October 2021 (UTC)

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I can find no explanation for why this request for deletion had been made Epzcaw (talk) 10:34, 3 September 2022 (UTC)

Optical and non-optical holography

A recent edit has changed the title "Non-optical holography" to "Other applications of holography" saying that "Electron holography, and atom holography are just as 'optical' as laser holography. Optical means so much more than the visible light reflected by the surfaces of anything that you can see with the naked eye.".

I believe (suported by dictionary definitions) that "optical" refers to light, and "light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye". I would like to have other opinions before reverting to the original title. In the meantime, I've dodged the issue by renaming the section as"Holography using other types of waves" but would prefer "non-optical" Epzcaw (talk) 10:53, 3 September 2022 (UTC)

I agree that in general use "optical" refers to electromagnetic radiation, and that "non-optical" is a better name for that section. Yes, I know terms like "electron optics" are well established, but for a general-purpose encyclopedia I think "non-optical" makes the point best. Incidentally, Hariharan titled one of the classic books on the subject "Optical Holography", but I can't recall after all this time what (if anything) he wrote about non-EM wave holography in it... anyone got access to a copy? Louis Knee (talk) 22:14, 3 September 2022 (UTC)

I have the book (2nd edtion, 1996). In the preface to the 1st edition (1986) -

"To make the best use of the available space, the scope of the book has been restricted to optical holography. No attempt has been made to cover related techniques such as acoustical and microwave holography which have not made such rapid progress."

No further comment is made in the preface to the 2nd edition.

So I think Hariharan would be happy with "non-optical". Epzcaw (talk) 08:32, 4 September 2022 (UTC)

Stumbled on a copy of Collier, Burckhardt and Lin; that's also titled "Optical Holography", and all I found that wasn't about visible light were some mentions of X-rays (Bragg) and electrons (microscopy) in the origins of holography historical section. Louis Knee (talk) 18:02, 8 September 2022 (UTC)