Holographic Displays

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tomandlu
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Holographic Displays

Postby tomandlu » Tue Feb 17, 2015 10:16 am UTC

Watching manga with my son yesterday, he asked me whether free-standing, animated holographic displays are plausible or not? Do they have any theoretical basis aside from, well, holograms?

I guess you could break them down into at least 3 distinct flavours:

  • Princess Leia - "Help me, Obi Wan Kenobi" - a visible single beam
  • The map in Avatar - fairly complex bit of kit
  • Total Recall - Arnie's hologram, indistinguishable from reality iirc
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Re: Holographic Displays

Postby Neil_Boekend » Tue Feb 17, 2015 10:29 am UTC

There is much that is available now that would have seemed impossible a hundred years ago so I am not going to say it is not possible.
However it is bloody difficult to turn light beams without a substrate to diffract or reflect them. Indistinguishable from magic and all that.

Who knows? In a hundred years a lot can happen.
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Re: Holographic Displays

Postby speising » Tue Feb 17, 2015 10:36 am UTC

well according to them, it may arrive in time yet.

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Re: Holographic Displays

Postby Neil_Boekend » Tue Feb 17, 2015 10:40 am UTC

The products they offer now are technically as different from the movie magic stuff as the difference between a painting and a statue.
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Re: Holographic Displays

Postby tomandlu » Tue Feb 17, 2015 12:46 pm UTC

Neil_Boekend wrote:However it is bloody difficult to turn light beams without a substrate to diffract or reflect them. Indistinguishable from magic and all that.


This was my thought (and the tech you linked to seems more like a giant 3DS screen afaict). Tnx.
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Re: Holographic Displays

Postby Izawwlgood » Tue Feb 17, 2015 12:56 pm UTC

I saw something a year or so ago about a research group that was using some neat trickery of focused soundwaves to project small amounts of force with millimeter range precision, and their catchline was something to the effect of providing hepatic feedback for holograms. So... that's neat.
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Re: Holographic Displays

Postby Copper Bezel » Thu Feb 19, 2015 10:04 am UTC

I still think it's much more practical to take the Google Glass + Kinect route. You could develop a 3D, "holographic" interface in a few years with that kind of kit, and it's not nearly as obtrusive as even 3D glasses are (so long as we settle for "Princess Leia" over "Total Recall" holograms.) In the race between finding an exotic behavior of light vs. convincing everyone to wear sticks on their heads, I think the latter is going to win.
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Re: Holographic Displays

Postby sevenperforce » Thu Feb 19, 2015 4:10 pm UTC

This is kind of out-there, but we are in fictional science, so...

...are there any subatomic particles with decay lifetimes on the right order such that they could be "tuned" to decay at a particular distance from their source, emitting a flash of light from that point? I'm thinking about how the original CRT monitors worked -- you use a couple of magnets to bend a stream of electrons such that they impact specific points on a 2D pane of glass doped with phosphorous or whatever. If, instead of using electrons, we used a particle with a decay lifetime of 4-5 nanoseconds that would cause a very small flicker of light wherever it decayed, that could be used to produce a floating 3D image with a similar setup.

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Re: Holographic Displays

Postby SDK » Thu Feb 19, 2015 4:23 pm UTC

Is there any particle that decays after a specific time frame? I thought all of them were like a half-life - some random occurence that you can't ever predict on an atomic level, just an average.
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Re: Holographic Displays

Postby sevenperforce » Thu Feb 19, 2015 5:52 pm UTC

SDK wrote:Is there any particle that decays after a specific time frame? I thought all of them were like a half-life - some random occurence that you can't ever predict on an atomic level, just an average.

It's a range, I think, but definitely a bounded one.

I'd be more interested in whether there is any particle which would be able to produce any significant number of photons upon decaying.

Another option is the possibility of using the air itself as an excitation medium of some kind; if you can use tuned lasers or something excite individual nitrogen molecules at a particular point, then the molecule will release light in all directions from that point, which gives you the effect you need.

Too bad there is no way to produce a standing wave without a reflector of some kind. Though I suppose reflector-aided holography would be a good first step.

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Re: Holographic Displays

Postby Izawwlgood » Thu Feb 19, 2015 5:58 pm UTC

You could feasibly do something wherein you fill a chamber with some kind of gas that is excitable at very specific energies, and hit it with multiple lasers?
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Re: Holographic Displays

Postby tomandlu » Thu Feb 19, 2015 6:00 pm UTC

SDK wrote:Is there any particle that decays after a specific time frame? I thought all of them were like a half-life - some random occurence that you can't ever predict on an atomic level, just an average.


Send two particles?
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Re: Holographic Displays

Postby tomandlu » Thu Feb 19, 2015 6:03 pm UTC

Copper Bezel wrote:I still think it's much more practical to take the Google Glass + Kinect route. You could develop a 3D, "holographic" interface in a few years with that kind of kit, and it's not nearly as obtrusive as even 3D glasses are (so long as we settle for "Princess Leia" over "Total Recall" holograms.) In the race between finding an exotic behavior of light vs. convincing everyone to wear sticks on their heads, I think the latter is going to win.


That was one of my thoughts, but why would we have to settle for PL over TR? Hell, with that technology, you could turn on dino-vision and have your day spiced up by random dinosaurs dotting the landscape. I'd definitely want the marvel superhero DLC - "hey, look, the FF are battling Galactus. Phew, Squirrel Girl's just turned up, crisis over - no, not that crisis. You need the DC DLC for that."
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Re: Holographic Displays

Postby speising » Thu Feb 19, 2015 6:12 pm UTC

tomandlu wrote:
SDK wrote:Is there any particle that decays after a specific time frame? I thought all of them were like a half-life - some random occurence that you can't ever predict on an atomic level, just an average.


Send two particles?

so what? they still can decay in the next ns or in 10 billion years.

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Re: Holographic Displays

Postby tomandlu » Thu Feb 19, 2015 6:13 pm UTC

speising wrote:
tomandlu wrote:
SDK wrote:Is there any particle that decays after a specific time frame? I thought all of them were like a half-life - some random occurence that you can't ever predict on an atomic level, just an average.


Send two particles?

so what? they still can decay in the next ns or in 10 billion years.


I was half joking. That said, how many particles do you need to make half-life accurate?
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Re: Holographic Displays

Postby sevenperforce » Thu Feb 19, 2015 6:25 pm UTC

tomandlu wrote:
speising wrote:
tomandlu wrote:
SDK wrote:Is there any particle that decays after a specific time frame? I thought all of them were like a half-life - some random occurence that you can't ever predict on an atomic level, just an average.


Send two particles?

so what? they still can decay in the next ns or in 10 billion years.


I was half joking. That said, how many particles do you need to make half-life accurate?

Particle decay is a Poisson process, not a stochastic process like radioactive decay. Individual particles have a mean lifetime rather than a half-life like radioactive nuclei; the probability of decay goes up exponentially around that mean lifetime.

Izawwlgood wrote:You could feasibly do something wherein you fill a chamber with some kind of gas that is excitable at very specific energies, and hit it with multiple lasers?

That's basically what a neon lamp is, right? Just without the whole finely tuned laser aspect.

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Re: Holographic Displays

Postby tomandlu » Thu Feb 19, 2015 6:37 pm UTC

sevenperforce wrote:Particle decay is a Poisson process, not a stochastic process like radioactive decay. Individual particles have a mean lifetime rather than a half-life like radioactive nuclei; the probability of decay goes up exponentially around that mean lifetime.


Ah - many thanks. I never even realised the two things (particle vs radioactive) were distinct.
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Re: Holographic Displays

Postby sevenperforce » Thu Feb 19, 2015 8:54 pm UTC

tomandlu wrote:
sevenperforce wrote:Particle decay is a Poisson process, not a stochastic process like radioactive decay. Individual particles have a mean lifetime rather than a half-life like radioactive nuclei; the probability of decay goes up exponentially around that mean lifetime.


Ah - many thanks. I never even realised the two things (particle vs radioactive) were distinct.

Radioactive decay happens when lattice of protons and neutrons inside the nucleus is unstable, resulting in less of the strong interaction holding it all together. The threshold for one or more of the protons or neutrons to "tunnel" out of the classical limits is low enough that the nucleus will eventually break apart in one way or another.

Particle decay, on the other hand, is a little different. As far as I understand it, it's more about chance interaction with virtual particles, though it still works through the weak interaction. Both radioactive decay and particle decay are caused by the weak interaction and follow an exponential decay curve, but particle decay has a gamma factor in its equation because the decay rate depends on the velocity of the particle.

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Re: Holographic Displays

Postby Copper Bezel » Thu Feb 19, 2015 9:14 pm UTC

tomandlu wrote:
Copper Bezel wrote:I still think it's much more practical to take the Google Glass + Kinect route. You could develop a 3D, "holographic" interface in a few years with that kind of kit, and it's not nearly as obtrusive as even 3D glasses are (so long as we settle for "Princess Leia" over "Total Recall" holograms.) In the race between finding an exotic behavior of light vs. convincing everyone to wear sticks on their heads, I think the latter is going to win.


That was one of my thoughts, but why would we have to settle for PL over TR?

Because you'd need bulky glasses that obscured your actual vision and fed you an AR stream. You could to the Princess Leia thing exclusively by adding photons, potentially right over your natural vision - just like a hologram, except you're wearing the lasers on your head and don't have to worry about turning them around in midflight.
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Re: Holographic Displays

Postby sevenperforce » Thu Feb 19, 2015 9:41 pm UTC

Izawwlgood wrote:I saw something a year or so ago about a research group that was using some neat trickery of focused soundwaves to project small amounts of force with millimeter range precision, and their catchline was something to the effect of providing hepatic feedback for holograms. So... that's neat.

That does sound interesting. If a single-frequency soundwave were focused to a small point, could it alter the optical properties of air enough to make it scatter light?

Nitrogen in the atmosphere scatters based on wavelength and a few other factors; at ordinary atmospheric pressure and density, about 1/100,000th of the photons in a beam will be scattered with every meter of travel. You'd need to somehow increase the optical density of air by a factor of roughly 1.7 million to get 50% of your light to scatter within a single centimeter of distance...and that's not very good resolution.

EDIT:

Sound waves produce compression and rarefaction of air, so in theory the intersection of two sound waves could produce a single point of denser air. Of course, increasing density by a factor of 1.7 million will be very difficult. If temperature remains constant then density is proportional to pressure, so the sound pressure of each sound wave would have to be around 8.6e10 Pa, which is really far too high to mess around with.

However, if you had something against which to bounce your sound waves, you could produce a standing wave...hopefully one with a really big gain at the center. I don't know much about standing wave gain in sound waves, but if this provided a viable mechanism then you could have something along these lines:

reflector pixel.png

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Re: Holographic Displays

Postby tomandlu » Fri Feb 20, 2015 12:16 pm UTC

Copper Bezel wrote:
tomandlu wrote:
Copper Bezel wrote:I still think it's much more practical to take the Google Glass + Kinect route. You could develop a 3D, "holographic" interface in a few years with that kind of kit, and it's not nearly as obtrusive as even 3D glasses are (so long as we settle for "Princess Leia" over "Total Recall" holograms.) In the race between finding an exotic behavior of light vs. convincing everyone to wear sticks on their heads, I think the latter is going to win.


That was one of my thoughts, but why would we have to settle for PL over TR?

Because you'd need bulky glasses that obscured your actual vision and fed you an AR stream. You could to the Princess Leia thing exclusively by adding photons, potentially right over your natural vision - just like a hologram, except you're wearing the lasers on your head and don't have to worry about turning them around in midflight.


Ah, okay. Personally, if someone could overlay reality in just the glass of a standard pair of glasses, that would be good enough for me. All you'd really lose would be a bit of activity in your peripheral vision.
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Re: Holographic Displays

Postby Izawwlgood » Fri Feb 20, 2015 2:20 pm UTC

What about something like this? The dude does call it dangerous :D
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Re: Holographic Displays

Postby sevenperforce » Fri Feb 20, 2015 3:06 pm UTC

Izawwlgood wrote:What about something like this? The dude does call it dangerous :D

I remember seeing this a while back. It's neat tech, to be sure, but I don't know that it holds much promise. Anything that starts with "So we get a really high-powered laser and focus it until it spontaneously ionizes diatomic nitrogen" is somewhat extreme; it's also pretty self-limiting. If you have to rely on creating bits of plasma then that's more or less a dead end.

If we're going to be playing around with lasers than anything other than a parametric process via scattering is probably not going to work well in the long run. The scattering ratio of nitrogen is just so poor, though. You could fix this by filling a transparent chamber with some gas that is significantly better at scattering, but then you end up with scattering all along the beam.

Could your "pixel" be produced using a positron beam and an electron beam and causing them to cross at the point where you wanted the pixel? Or would the positron beam be annihilated as soon as they hit air? I don't know if the pair of gamma rays produced in electron-positron annihilation would just disappear invisibly or if they would be able to produce some sort of glow.

The most promising approach, logistically, would seem to be something like a CRT monitor where you're using an electron beam to excite something and produce a glow that way. How to make it work in three dimensions is the problem.

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Re: Holographic Displays

Postby Izawwlgood » Fri Feb 20, 2015 3:47 pm UTC

I think we should also back up, and ask how interactive we want this to be. A holographic display that can only produce images in an enclosed space may be less useful. Similarly, a hologram that completely falls apart when you exhale sharply in it's general direction may also be kind of useless.

This is in fictional science, so, 'magnets', right?
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Re: Holographic Displays

Postby Andries » Fri Feb 20, 2015 4:03 pm UTC

Rather than 3 d glasses, I would go with affect people's optic nerves directly. With.... um... ultrasound. Yes, ultrasound it is.

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Re: Holographic Displays

Postby sevenperforce » Fri Feb 20, 2015 4:09 pm UTC

Izawwlgood wrote:I think we should also back up, and ask how interactive we want this to be. A holographic display that can only produce images in an enclosed space may be less useful. Similarly, a hologram that completely falls apart when you exhale sharply in it's general direction may also be kind of useless.

This is in fictional science, so, 'magnets', right?

Hah. Honestly this topic belongs more in science than in fictional science.

As a starting point, simply having the capacity to either:

  • Display a 2-dimensional screen in midair using a projector, or
  • Display a dynamic, decent-resolution 2.5-dimensional image (e.g. relief) inside an enclosed space
would be a huge leap forward compared to our current capabilities.

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Re: Holographic Displays

Postby Copper Bezel » Fri Feb 20, 2015 6:31 pm UTC

tomandlu wrote:Ah, okay. Personally, if someone could overlay reality in just the glass of a standard pair of glasses, that would be good enough for me. All you'd really lose would be a bit of activity in your peripheral vision.

I think the optics would still be a bit of a challenge even then, but I'm not sure how Glass solves it in the first place, either. I mean, obviously, you need to fake a longer focal distance than the plane of the glasses themselves.

My main concern wouldn't be the fact that it wouldn't work in peripheral vision, but the fact that everyone in the room would be walking around with dark glasses on. I mean, it's kind of a silly image, even if they can see what they're doing. I like the perk of Glass not actually obscuring the eyes.

I'm now having the hilarious image of the AR drawing their faces back on.
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Re: Holographic Displays

Postby Andries » Fri Feb 20, 2015 8:47 pm UTC

sevenperforce wrote:You'd need to somehow increase the optical density of air by a factor of roughly 1.7 million to get 50% of your light to scatter within a single centimeter of distance...and that's not very good resolution.


It would also be a tad noisy

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Re: Holographic Displays

Postby sevenperforce » Fri Feb 20, 2015 9:15 pm UTC

Andries wrote:
sevenperforce wrote:You'd need to somehow increase the optical density of air by a factor of roughly 1.7 million to get 50% of your light to scatter within a single centimeter of distance...and that's not very good resolution.


It would also be a tad noisy

Eh, ultrasound or something.

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Re: Holographic Displays

Postby tomandlu » Sat Feb 21, 2015 11:26 am UTC

Copper Bezel wrote:
tomandlu wrote:Ah, okay. Personally, if someone could overlay reality in just the glass of a standard pair of glasses, that would be good enough for me. All you'd really lose would be a bit of activity in your peripheral vision.

I think the optics would still be a bit of a challenge even then, but I'm not sure how Glass solves it in the first place, either. I mean, obviously, you need to fake a longer focal distance than the plane of the glasses themselves.

My main concern wouldn't be the fact that it wouldn't work in peripheral vision, but the fact that everyone in the room would be walking around with dark glasses on. I mean, it's kind of a silly image, even if they can see what they're doing. I like the perk of Glass not actually obscuring the eyes.

I'm now having the hilarious image of the AR drawing their faces back on.


Ah - I was thinking clear glasses, but able to impose images of any colour and opacity on them.

Focal distance would be a problem... how about allowing the light from the images to bounce back and fourth within the layer of glass an arbitrary number of times before finally being released?
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Re: Holographic Displays

Postby Copper Bezel » Sun Feb 22, 2015 5:55 am UTC

Aside from requiring metamaterial shenanigans on par with actual holography, I don't know if bouncing the light back and forth solves the problem. It's position and orientation, not time or distance traveled. You can use fancy optics to create any arbitrary focal distance you choose in a relatively short space and reflection to alter orientation, scale it, whatever - so that a little tube above your ear can handle the whole thing. But the plane of the glasses themselves is still out of focus. So if you're making the glasses themselves selectively opaque, there's no way to make that mask effect have the same focal distance as your actual focus. I trust that a little optical trickery could be sufficient to make something like Google Glass that covers the majority of your field of view, whether or not the glasses are opaque, and you could have either clear lenses (or none at all!) and transparent holograms, or opaque glasses with extra cameras on and opaque holograms . But I don't see any way to make selective opacity work with that paradigm, because the assumption in either situation is that the glasses themselves aren't doing the work - it's a projection that loops over or under them to get to your eyes.
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Re: Holographic Displays

Postby Hypnosifl » Thu Dec 17, 2015 8:06 am UTC

sevenperforce wrote:
Izawwlgood wrote:What about something like this? The dude does call it dangerous :D

I remember seeing this a while back. It's neat tech, to be sure, but I don't know that it holds much promise. Anything that starts with "So we get a really high-powered laser and focus it until it spontaneously ionizes diatomic nitrogen" is somewhat extreme; it's also pretty self-limiting. If you have to rely on creating bits of plasma then that's more or less a dead end.

There's a new form of this tech that uses lasers that turn on and off much more quickly, apparently resulting in much lower-energy plasma "voxels" (volume pixels) that present no danger when they briefly come in contact with human skin (though it sounds like there has to be a sensor that stops trying to project a voxel at a given location when it senses a solid object like a person is occupying it):

http://spectrum.ieee.org/tech-talk/cons ... -can-touch

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Re: Holographic Displays

Postby gmalivuk » Fri Dec 18, 2015 1:45 pm UTC

sevenperforce wrote:
tomandlu wrote:
speising wrote:
tomandlu wrote:
SDK wrote:Is there any particle that decays after a specific time frame? I thought all of them were like a half-life - some random occurence that you can't ever predict on an atomic level, just an average.


Send two particles?

so what? they still can decay in the next ns or in 10 billion years.


I was half joking. That said, how many particles do you need to make half-life accurate?

Particle decay is a Poisson process, not a stochastic process like radioactive decay. Individual particles have a mean lifetime rather than a half-life like radioactive nuclei; the probability of decay goes up exponentially around that mean lifetime.

Are you sure about that? My understanding was that the mathematics were the same, just talked about differently (with mean lifetime being when there's a 1/e probability it's still there instead of 1/2)

Edit: Yeah, it looks like the Wikipedia article on particle decay confirms my impression. They're mathematically the same process, it's just that radioactive decay tends to involve much larger samples and so the idea of a half-life is more conceptually useful than it is for single particles.
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Re: Holographic Displays

Postby SuicideJunkie » Wed Jan 27, 2016 4:58 pm UTC

The interlacing effect seen on screen is clearly due to the differing frame rates of the hologram and the movie projector and/or your TV screen.

Could you filter gasses from the air, and concentrate desired chemicals into your hologram spray to improve the visibility rather than rely on sheer density?

The blue looks related to ion drives.
What if you use a forcefield to clear the projection zone of air, and then lob ionized atoms upwards?
Alternate with waves of ions and electrons, timed so that they recombine and emit light while moving relatively slowly at the desired altitude.

Or, since the shields are generally visible, what about using a standard video projector to throw an image onto a weak shield that sweeps vertically.


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