Not those Magic Eye type dealies, but like the Princess Leia holograms. Those exist, right? HowStuffWorks couldn’t help me with a query, and Googling all sorts of stuff didn’t work. Obviously I don’t know exactly what to put in.
Anyway. Do these sorts of holograms have a front/back/top/etc. relative to the machine(s) making them, or to the viewer? Ie. if I have a hologram saying “Hello World”, would it be in reverse if you stood on the wrong side of it? Or for Leia herself, if you stood in the wrong spot, would you see her back, or is it no matter where you stand you see her face? Without myself really understanding how holograms work, I can’t logic it out.
And I humbly apologize if this was asked any time recently - a board search turned up nothing either.
Real holograms, like the dove on a VISA card, are essentially a physical recording of the light reflected off an object, within a certain angle range. It’s possible to create holograms of objects that can’t exist in real life, or angle ranges that can’t be captured in a lab (e.g. by using a computer and a dot-matrix hologram printer), but the hologram is still recorded on one side of a piece of foil or a glass plate.
If you look through the back side of a plate hologram, you do see the hologram reversed. I imagine the 3D would be all wrong, though - unfortunately, I don’t have any plates to look at right now.
Well, it’d be more of a “holovision display”, but I do know of a way to make a moving hologram type thing. (You’d have to be looking at it though, it’s not free-standing, Star Trek holodeck, Total-Recall type thing).
The father of some family friends was a prof (since retired) in the physics dept of the UofA. I visited there once, and a grad student was working on a 3d display -
You can get silicon chips machined to your specs. This student had made a chip with lots of flat “mirrors” attached to the substrate with cantilevered conductor. With the chip clamped in a horseshoe magnet, the idea was to send current through these conductors. The current would create a magnetic field, which would make the “mirrors” move. Shine a laser at the chip, and you have a “holographic array”, I suppose.
I don’t know if it ever worked, but someone in another dept. told me a large company (IBM? Motorola?) makes a similar product now using static charges and an array of tiny mirrors on pegs.
If you mean a hologram projected into thin air (e.g. “Help me obi-wan kenobi, you’re my only hope”), then no, those don’t exist. The best you can do is a hologram captured on a cylindrical piece of plastic, allowing you to walk around the hologram and see it from all angles.
And of course, these are static holograms. I don’t think that anyone has come up with a way to generate moving holograms (I mean actual holograms, not funky mirror shenanigans) yet.
No wonder I couldn’t find any information on Google. At least I had a stupid misunderstanding shot down to where it belongs, I hate thinking something exists when it doesn’t.
There are holograms (and other types of display) that trick you into thinking you’re seeing a free-floating image, but (and this is hard to explain) the moment you position yourself so that the (apparently)free-floating image is not framed by the screen (apparently)behind it, it disappears.
It also disappears if someone walks between you and the screen, which can be very visually disturbing (because your brain is expecting them to walk behind the image).
Another feature of these types of displays is that although the image appears to be floating in mid-air, it is still ‘flat’ - although this is not always immediately noticeable due to the ‘wow’ factor.
There was an (excrable, unplayable) arcade game that took advantage of this technique, but I can’t remember what it was called.
Yes, I think that is the one. It was unplayable (although this is more a general attribute of laserdisc arcade games than it is anything to do with the display type.
Tell me about it. I once had a dream where I owned a kick-ass flying car. My alarm clock quickly intervened, as it is wont to do when I dream of having things like flying cars, a harem of beautiful virgins, or my own personal army of killer robots.
Yes! Texas Instruments manufactures something they call DLP (digital light processor). They’re used in high-quality (expensive) projection TV’s and video projectors. Check out dlp.com for some details (warning: site contains excessive amounts of Flash crap).
Holograms are easiest to understand when the image is behind the plate. There, you can think of the photgraphic plate as a “window”, and you can only see the “object” when it’s behind the window. But other than that, it’ll look like a normal object: Look a little to the side, and you’ll see the side of the object. In fact, it’s this property that leads to the 3-d effect: Your left eye sees the “object” from a different point of view than your right eye, which your brain interprets as being due to the object being 3-d.
In some holograms, though, the image is partially or wholly above the plate. in this case, the image still looks like an ordinary object, viewable from different angles, except that you can never see the image against any background outher than the photographic plate. If part of the image extends past the edge of the plate, the image just cuts off there.
One way to understand why this is so: Every ray of light that hits your eye must come from somewhere. Since we don’t yet have any idea how to make a ray of light come from thin air[sup]*[/sup], that ray has to come from the holographic plate. If you look in any direction other than at the plate, there’s nowhere for the ray to come from.
And depending on what you mean by moving holograms, they do exist. Usually, they rely on a rotating drum: Instead of using different angles of view for spatial information, you put each angle of view at a different time of observation. So as the drum turns, the image you see changes. It’s also possible in principle to embed multiple holograms in a single plate, with each one visible when illuminated from the right direction. In this case, you could change the direction of illumination in such a way as to make the image move. But I don’t think that the current technology is up to anything more than a very jerky motion, this way.
*I’m not going to rule out the possibility that we’ll someday come up with technology to produce rays of light from thin air, and if we do, then we’ll be able to use that technology to produce Princess Leia-style holograms. In turn, any such technology which produced a 3-d image would of necessity show you the back side of the object, if you walked around it (if it didn’t change, then your eyes would both get the same information, and it’d look flat). But such technology, when and if it is developed, is unlikely to have any relation to present holography technology. Although people will probably still call them holograms.
At least I had a stupid misunderstanding shot down to where it belongs, I hate thinking something exists when it doesn’t.