Whatever became of holography? (2011)
americanscientist.org
americanscientist.org
3blue1brown has a great explainer video on what holograms are: https://youtu.be/EmKQsSDlaa4
That's like saying a CRT doesn't display a picture because it energizes pixels only one at a time.
You can also make things like holographic lenses [1].
And, "display" doesn't seem right. If you recorded a still image, it's a (literal) record of the light field of a scene that lets you view the scene in 3d, like a magnifying glass functioning from all perspectives [2]. You do get the "display" of a 3d scene out of it, when used that way.
Fun fact, you can make your own at home with gelatin, some photo chemicals [3], a laser, and a ludicrously stable table. DIY hologram is going to be one of the first things I do when I retire.
[1] Used in HUDs, like in fighter jets. https://en.wikipedia.org/wiki/Holographic_optical_element
[2] https://www.youtube.com/watch?v=iMdvBmePm9U and https://www.youtube.com/shorts/DnjATyPuFFk
I wouldn’t say they “didn’t” take off. They’re gradually acquiring market share.
Its problem seems to be that it was a solution to a problem that was fast disappearing, at the cost of unacceptable tradeoffs.
The Lytro sacrifices a ton of resolution and produces crappy images, in exchange for being able to refocus. And they did that in an age where excellent autofocus was already available.
These days we have cameras with AI models that recognize birds and animals and focus flawlessly almost every single time. And they don't sacrifice any resolution to do it. And they are proper, comfortable cameras rather than a weird stick.
Problem is you can already take a fairly deep focus image (with a stopped down lens) and then fake shallow focus later if you want.....
(I own a similar print, different microscope).
Holograms are cool but it is a finicky technology and speckle makes them visually ugly.
Holography is the display, not the rendering process. It contains, inherently, how the light is focused, so your eyes can refocus on near and far objects within the scene even though it's a static image.
But more to the point, a hologram is less like a computer display and more like a photograph.
It's possible that you haven't actually seen a real hologram. It's quite impressive. The ones I have seen are 3-dimensional objects in the air in front of you, and you can walk around it, typically not the full 360 degrees, but it's just.. there. It's nothing at all like what we normally call a "display".
One can hope we someday have this capability.
It's not exactly like looking through a window, they can do that, but they can render an image in front of the window as well as behind it.
"Screen", sure, that implies 2d. "Display", is a much more general term covering screens, LED readout panels, a shadowbox of physical objects, and more. There are a lot of things that are displays that are 3d already.
"Hologram" is one of those words that has a wide variety of overlapping meanings. You can be a strict prescriptionist about it and insist that a real hologram involves laser light, interference patterns, 3D scene replication, phase preservation etc, but there will always be something that doesn't quite meet your definition that nevertheless is called a "hologram" by large numbers of people, even expert optical scientists:
A digital holographic stereogram prints an array of hogels (holographic pixels); the hogels themselves are holograms, but are mutually incoherent across the plate. When implemented to the highest level, the result is perceptually and behaviorally indistinguishable from an analog hologram.
A rainbow hologram (such as are found on credit cards) has single parallax only - it certainly does not capture all the properties of any particular electromagnetic field. No purity here, it's just a nifty tech for making things look 3D that happens to exploit wave interference. And everyone calls those holograms.
A scratch hologram is, to a first approximation, an extremely coarse version of a rainbow hologram, made by hand by engraving curved grooves in a reflective material. Now we're away from lasers and wave interference, and for this we sacrifice color - but geometrically we are still dealing with directional microreflections on a surface. Hologram? Depends who you ask.
Lenticular holograms use refraction rather than diffraction to achieve essentially the same imaging model as a rainbow hologram, but in a decidedly less finicky way, at the expense of some resolution. The same imaging data could be used to make a lenticular or a rainbow hologram. No lasers, no diffraction. Hologram? Depends who you ask...
My advice, as someone who has worked with holograms for a decade, is to give up. Saying "AKTUALLY Tupac/Abba isn't a hologram" gets old after the 1000th time. In the real world, "hologram" means "intangible optical simulacra", regardless of how it was achieved. If you want more precision than that, you have to specify the actual technology - Denisyuk, rainbow, lenticular, etc...
When someone asks "can you make a hologram of this", you don't lecture them on optical physics. You say "sure, you want the expensive kind or the plastic kind?"
Mutually incoherent hogels ... the mind boggles.
I might quibble with lenticular displays, since they have a name that predates holography.
In the ideal world, a larger umbrella term would have emerged. "Autostereoscopic" describes any display that provides different views without glasses, but that typically suggests discrete views.
"Plenogram" would have been reasonable following Adelson and Bergen's plenoptic function, but that didn't and won't happen.
"Hologram" now basically means a sufficiently advanced three-dimensional display in popular culture. And that even leaves of other real holograms, such as the ones used for non-destructive testing.
*prescriptivist
Red Dwarf may have gotten this one right for comedic purposes :-D
Holograms compete with many other display technologies such as stereograms, VR headsets, as well as volumetric and light field displays. This technology is described as "holographic"
https://lookingglassfactory.com/
but it looks better than holograms because it uses incoherent light field technology that doesn't have the speckle, plus the pipeline to make content for it doesn't require lasers, special equipment or special skills.
The video is a bit old, but it has a few fun demos of the capabilities they've developed.
Much of the supply chain for modern hobbyist holography was sourced out of Russia, and the ongoing wars have made those materials unavailable.
There are some newer processes out there, but there were probably thousands of us that grew up using those HoloKit holography kits distributed by TJ.
That's required because off-axis display holograms have spatial frequencies ranging from about 1200 line pairs per mm for transmission holograms to maybe 5000 for reflection holograms.
Because the grain size is so small, these plates tend to be pretty insensitive to light. That's why they have limited use outside of holography these days.
Other types of emulsions such as dichromated gelatin also exist but are also hard to find. DCG is even less sensitive to light.
In either case, the wavelength the material is sensitive to matters when exposing with a single frequency laser.
Then there are issues about the substrate if the emulsion is on film related to polarization preservation.
You do need to have a decent point light to shine on it, but you can sell that too. You can even sell a frame that has a clip-on light that's just right[1], although a perfect lighting setup is not required.
[1] Like Dutch Holographic Laboratory does: https://holoprint.com/pages/components.php#Telescope
Oh hey, I have worked in exactly this business (taking people's random 3D models and bullying a rendering pipeline into feeding a digital holographic printer). It's hard, for many reasons. Mainly it's that holograms are expensive in materials, labor, and capital outlay (adding up to several k just for something the size of a piece of paper), and mass production of digital holograms isn't really possible without massive further outlay - writing them is time consuming, and copying them is fraught. It's like being a graphic design / print workshop, except everything is way more fiddly and expensive and nobody wants your product.
Analog holograms are a bit more tractable. But that's even more niche on the consumption end.
A very "entry level" not good but maybe enough to kick off an industry digital transmission hologram would be like "hundreds of gigapixels" or at least dozens and thats not realistic for computers of this time. The super cool reflection holograms are much worse, like "many dozens of terapixels" to even begin to play with.
I guess its good news there are still frontiers of computation out there to reach. A lot of people believed progress would cease when computers could do high enough resolution video, and they're mostly correct, progress has halted for the general public. But if we ever get smart phones with low petabyte fast on device storage and display, those could realistically have "star trek" like transmission holograms.
That beings up some interesting issues WRT RF engineering. Shannons law and all that. Even with unimaginably complex compression algos will something like a hand held hologram video conference (similar to sci fi tropes) ever be possible? Maybe 60 PB/s would not be unreasonable. Consider the LHC only generates about 1 PB/s when its running and that takes a rather large distributed system and a lot of electricity. I don't think video conference holograms will be realistic... Strange thought experiment the only way to do a "holographic video conference" with sane data transfer rates and power levels might be to send the other side a LLM prompt and ask for a locally AI generated video hologram. "Here's 1000 jpeg pictures of me as raw data, render a hologram of me saying 'scotty beam me up'"
The display hardware tech would be pretty wild. I think it could be done but it would require a minimum of 1980s nanotechnology hype. Like DLP but using individual atoms not "large" silicon mirrors.
In summary the MVP for digital photography required early 1990s hardware, but the MVP for digital holograms requires a LOT more than 2020s hardware. Maybe in the 2040s, 2100s, who knows.
Though that also is part of the reason that a they're not more common. Each hologram is the film rather than a "print".
If someone wants to make 100 holograms to be able to sell them as more than a one off art piece you're making 100 units of the film.
Film sheets might be doable.
https://www.geola.com/product/pfg-01-film/ for a Lithuanian distributor. 35cm (about 1 foot) isn't that large. Might be able to cut it into 4ths (classic 4"x5") ... 2"x3" is a small size (12 per sheet).
A hologram is much like a window, you can look through a big window or a small window, and see what's at the other side both times, but the big window still gives you a lot more viewing angles than the small one. Cutting a hologram in half gives you half a hologram, not two copies of the hologram, it's just that you can change your viewing angle to still see what's on the other side, but that will be a different image than with the full hologram.
You get pretty much what you would naively expect from chopping up a hologram before reading that kind of misleading "two copies" text: exactly the same view of the object as you had from that part of the hologram before you cut it up.
It shows a hologram that has been cut into 3 pieces and the aspect of the viewpoint changing as you look through it, though each one has the full subject that was imaged.
My point is that while you can see the full subject you get it from the exact same point of view as that part of the hologram before it was chopped up.
If you couldn't see part of the subject from part of the intact plate you won't be able to after either.
The phrasing you used, "two copies of the hologram" is very misleading in the same way that my Usborne book was.
Chopping a hologram in half gives you two copies of the hologram in exactly the same sense that chopping a photo in half gives you two copies of the photo.
In both cases what you can see from that part of the plate/print is the same before and after you chop it up.
This might be true for current processes but it seems like it should be possible to duplicate a hologram - use a hologram as a stand-in for the original scene when creating a new hologram. The result might have some blur (that progressively gets worse the more 'generations' you are from the original) but that seems like a solvable problem if someone worked at it.
I think the real reason we don't see them is more practical - it's amazing tech but a bit too much of a novelty in its current state, it's just not something that most people would want to put on their wall.
The main challenge is that there are, to my knowledge, only two remaining manufacturers of the plates - in France, and in Russia.
I've had the pleasure of working behind the scenes on holography related stuff (primarily optomechanics) for years now. Fascinating field full of phenomenally interesting minds.
These are a couple of links I've just looked up with information about it.
https://tolkienvisualcollectingguide.blogspot.com/2022/09/to...
Its this odd often blurry and hard to see thing that certainly has interesting aspects but is not something you can create easily at home, unlike a photograph. Then the world changed and mobile devices ruled and everyone had a good camera sensor in their pocket, TVs were thinner and higher resolution than ever, games started looking amazing, etc and there really wasn't any room for less practical things like holograms.
I think its one of those things we just weirdly romanticize like a car that is also a boat or a jetpack, but in reality has no real place as a consumer product.
All other variants were degrees of magnitude worse.
There was a short-lived flurry of art establishment interest in high quality glass holograms, but the process is just too expensive and fragile to create non-niche art.
I always expected that at some point we'd have dynamic holographic displays, but the processing and resolution requirements are insane.
Holographic film has a resolution in the region of 100,000 to 250,000 ppi, which is quite a bit more than 300dpi for print or a few thousand PPI for plain old film. If you could build a 27" display with that resolution you'd need maybe 1TB per frame at a minimum.
You could probably apply quite a bit of compression to get that down on input, but that's still the order of a workable frame store memory.
Multiply by three for colour.
It's possible to do this with digital methods, too, but the lower spatial resolution of most digital LCDs and most digital camera sensors (compared to film) limits it somewhat. But I think it'd be more practical than the analog film based analytical holograms.
Depth of reflection holograms depends on the quality of the reference beam. A divergent one gives limited depth but a parallel or convergent one would give much more. But this is much more difficult to achieve.
It’s a microscope, that in the correct angle allows you to actually look down the viewfinder and see what the microscope was displaying.
This works because the hologram is recording the interference pattern of the photons that existed in the actual scene.
I’m really fascinated by these types of holograms and think they hold quite a bit of artistic potential.
So in addition to the skin damage that’s super obvious in this vid, you have this sharp buzzing crackling sound like some turbo sting gun.
Not sure what became of it.
NYC also used to have the "Museum of Holography" which I was fortunately able to visit but may not exist anymore.
3D stuff, in general, seems to not do well. Not sure why! (as I dust off my Vision Pro)
One image that I remember being particularly impressed by was a model of a radio telescope dish. You could look around the dish and see all the support gantry. The contrast between the smooth dish face and the structure on the other side made the 3D nature very dramatic.
On the counter they had a nice mirror illusion¹ of a floating "help" button - not a plate hologram but a really nice effect and you can still get these. They tend to be cheap plastic and dust and scratches affect them over time, but it's still a really nice effect if you've not seen it before.
They also offer classes and a residency program that I have been keenly considering.
Once in the 1980s, their Science Center had some impressive hologram exhibits. There were vivid 3D images that you could walk around and inspect and marvel at. I was seriously amazed. So of course I felt compelled to purchase a hologram from the gift shop.
Well, the "hologram" I purchased was legit. It was a laser-produced headshot of a female model and it was 3D just like in the exhibit. Sadly, it was not really viable once I got it home.
You see, it was sold to me on a sheet of film, and that's it. It was totally inexpensive for them to produce, but it wasn't complete! The instructions or whatever, they said that it needed to be mounted and viewed in a cylinder with a strong light-source mounted inside! In other words, the enclosure and fixture equipment, not included, was essential to a good experience.
As a kid I really did feel cheated by that. Selling those films was sensational but utterly useless. I held onto that thing for years, though. You could kinda see it by holding it near a lightbulb and bending it. But it was a far cry from the exhibit that had commanded my childlike interest. Sadly.
This trend is annoying and is punishing users to stop scraping of their stupid articles. I feel like 20 times a day I have to wait or click a box or something just so they can charge robots to read their public content.
There’s enough sites who don’t have this annoying feature.
https://computerchronicles.tv/#episode/1610 (Video, skip to 11:47)