Holograms

[MirceaKitsune]

Every high-tech fan is probably fascinated by the idea of holograms. Whether it's to have their TV or computer monitor projected in mid air, or to see floating transparent images replacing the old rusty billboards in their city. Unfortunately however, I've yet to see any holograms in real life... even videos of a functional one being tested in a NASA lab. The best I've seen are transparent screens and smartphones, or persistence-of-vision clocks (a fast spinning blade with LED's on it). Still, this shouldn't be too far from becoming possible, and I'd like to know what could be realistically expected and when.

 

From a scientific perspective, it's not hard to see why they're so difficult to do. Light typically has to reflect into the eye from something solid, in order for you to see something there... so making light reflect in mid air is an unique and difficult task. At the same time however, given what we know about particles, it wouldn't be impossible either. The trick is finding a way to knock particles of light in a different direction mid-air, so when they reach the eye they cause the impression that the point where they were knocked at is actually where they originated from.

 

This could be achieved if we could create a special particle that can't be seen or touched, and that's "rigged" to explode into photons after a very precise amount of time. A screen could then be a "sprinkler" that sprays such particles upward, each particle timed to detonate into photons based on the vertical line of the screen it represents. Radioactive decay somewhat comes to mind, although I think an entirely different process would be involved here... such as a changing the particle's composition and creating energy in the process. Since the color of each pixel must also be respected, the frequency of the light emitted by each reaction must also be predetermined and controlled. Therefore this sounds like a very distant possibility.

 

So a different but more plausible alternative would be to create a field of particles which can collide with photons and knock them in the desired direction. In this case, you could use a standard projector like those that exist today, and just point them upward. Parallel to it and aligned to person's face however, must lie another device which throws particles that shoot photons with enough force to knock them in the desired direction... in this case toward the person's eyes. Obviously those special particles should be invisible, and not cause cancer when they reach the person's body. Alternately, those special particles could instead be launched forth into a square pattern, in order to create an invisible and untouchable surface that can bend light, which the projector could then shine on directly.

 

If all of the above methods are still too difficult to do, we might have to stick with transparent glass screens, which can be pretty cool if done properly. One way is to beam the light of each pixel from one edge or corner of the glass toward its center. The glass would contain unnoticeable impurities meant to reflect each pixel, and each ray of light would be built with extreme precision so that it hits its intended impurity to reflect it. The easiest design could be making the thickness of the glass pyramidal, so the front face is flat but the back warps into a point. A tiny projector that creates the rays for each pixel is installed on said junction, and each pixel is reflected in the right direction and at the right depth so it's refracted by the glass where it needs to be as it exits its volume.

 

Any images or videos of what exists in this domain so far? When can we expect to see hologram screens becoming a reality, and what would be the steps this technology will go through?

Edited October 2, 2014 by MirceaKitsune

[andrewcellini]

how does the field control where a photon is projected? how stable are interference patterns in this field?

 

also i believe this should be in the physics section.

more importantly how is this related to holography at all?

Edited October 2, 2014 by andrewcellini

[MirceaKitsune]

how does the field control where a photon is projected? how stable are interference patterns in this field?

 

also i believe this should be in the physics section.

more importantly how is this related to holography at all?

 

I guess it would depend on the method used? A real physicist and computer engineer would know... I'm not one myself. I was primarily speaking out an idea... don't even know which known particles could kick photons.

 

And that's related since I imagine holography implies changing the direction of a light particle in mid air, or making one appear in mid air. Without using an invisible reflecting object, I don't see another logical solution.

[andrewcellini]

i don't know much about holography myself, it's just this seems a lot like this illusion, at least your final option does: https://en.wikipedia.org/wiki/Pepper%27s_ghost

i believe i read they used a sort of angled glass screen at coachella for projecting the tupac "hologram" though i could be mistaken on that.

Edited October 2, 2014 by andrewcellini

[MirceaKitsune]

i don't know much about holography myself, it's just this seems a lot like this illusion, at least your final option does: https://en.wikipedia.org/wiki/Pepper%27s_ghost

i believe i read they used a sort of angled glass screen at coachella for projecting the tupac "hologram" though i could be mistaken on that.

 

I didn't know about that term, thanks. But well, holograms are illusions more or less. From what I know, a hologram is simply an image that can be projected mid-air, not as light bouncing off a surface the way we're used to it. So it must involve a way of invisibly changing the trajectory of light rays so you see them coming out of empty space.

[andrewcellini]

 

But well, holograms are illusions more or less.

i'm not so sure, holograms don't play around with how we perceive things to be, rather they have an underlying physical explanation as to how the light interference pattern is recorded and projected as a virtual image.

 

http://en.wikipedia.org/wiki/Holography#Physics_of_holography

http://en.wikipedia.org/wiki/Virtual_image

 

edit: this isn't to say there isn't an explanation as to how pepper's ghost and the like works, just that in principle it's much different.

Edited October 3, 2014 by andrewcellini

[andrewcellini]

http://en.wikipedia.org/wiki/Specular_holography - i just recently came across this and it also seems related and is a form of holography somewhat similar to your 3rd option. note however that like wavefront holograms like have a medium from which the virtual image is projected.

Edited October 3, 2014 by andrewcellini

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Your exploding particles idea is a bit far fetched, as there is no way I know of to create a particle which dissolves into photons on a timer. However, you have developed some interesting ideas here.

Edited October 4, 2014 by /backslash/