About holograms

[Mr. Peterman]

I have seen images on holographic film where you can look at the film at different angles and the image change, but are all holograms like that? Do you actually only seen an image against the film background or can you now see the image popped up on a real life background like on Star Wars? I've seen videos where the image was against a real background but I thought that they might could have projected it on some type of glass. And if it does pop up like on Star Wars, does the light bend in the air( I don't think so, but I'm still asking), or does it travel directly from the film to your eye and trick it in a way by superposition and interference of waves to make it look like it comes from above. I've never seen Star Wars like holograms except on online videos, so I wasn't sure if they had that technology or if it was movie tricks. Thank you.

[Theory5]

Well it depends I guess. The first time I saw a working "hologram" it was at the Boston museum of science. When I looked into the glass I saw mirrors in a circle angled so they would intercept at on point (the hologram) and the object that was being shown. The object was orange but it was see-through so light could go through it, which got me thinking. Do all objects you want to display as a hologram have to be transparent? If so then how could you take something from a TV screen and make it hologram? I never figured it out. I dont we can make starwars like holograms yet but its possible.

The light does not bend at all. Mirrors make light intersect at a given angle in the air ( there must be mirrors in a complete circle). I belive that if mirrors are missing it wont work.

[CraigD]

I have seen images on holographic film where you can look at the film at different angles and the image change, but are all holograms like that? Do you actually only seen an image against the film background or can you now see the image popped up on a real life background like on Star Wars?

To see an imaged object via a photographic hologram, the holographic “plate” must be in your line of sight to the image. A hologram can be made in which the object appears to be positioned in front of the plate, as if the plate is a wall behind the object, or behind the plate, as if the plate is a window in front of the object. If you’re tricky, the hologram can be of the actual background where it’s place for viewing, fooling you into perceiving the plate as not being there, but this is trickery – if the actual background changes from what was recorded on the plate, the trick fails.

 

Most holograms are still photographs, and require that the object to be photographed be kept extraordinarily still during the photographic plate’s exposure, Motion of even a small fraction of the wavelength of the reference beam light results not in the minor blurring familiar to photographers, but in a near total loss of image. Holographic rigs, therefore, often use elaborate vibration isolation systems, involving such things as air-suspension tables.

 

This makes it practically impossible to holographically photograph moving objects. However, present day display screen technology has achieved high enough resolution that it’s possible for an hologram to be generated using computer programs rather than actual photography, making true holographic moving pictures possible. Combined with motion capture and CGI techniques, such a “holographic movie” can look very much like a real, moving object. This tech, still in its early development, is know as Computer Generated Holography. It’s still necessary for the screen to be in viewer’s line of sight to the image for it to work.

 

So the image that appears to be projected from R2-D2 in the famous “help me, Obi-wan” scene from “Star Wars: A New Hope” can’t be explained as an application of any sort of present day holographic photography of CGI.

 

There are other ways to produce realistic looking 3-D images than holography. One such method involves what’s known as a “volumetric display”, in which an image appears in a “tank” or similar contained volume. A typical real world volumetric display consists of a high-switching speed 2-D display screen mounted on a rapidly spinning motor-driven base, much like the spinning battery-powered LED “party globes” (eg: http:// http://www.flashingblinkylights.com/lightupmagicspinningamericanflags-p-1966.html?osCsid=29ctkbjfcbiug3u8gapsk5msn4 )that can be had for a few US dollars, but capable of producing a realistic-looking 3-D translucent image rather than a crude colorful globe. Such devices are currently in limited use for such things as planning how to treat tumors using beamed radiation based on data about a patient’s body captured by a CAT x-ray scanner.

 

Another sort of volumetric display involve illuminating fog or smoke with light beams. They can make for impressive light shows (they can be made very big, even arena-sized), but fall short in my experience of being convincing 3-D images of actual objects.

 

Yet another sort of volumetric display uses very high-powered, briefly pulsed, precisely focused laser to produce small volumes of glowing plasma in air. In principle, these could be made so high-resolution that they could produce realistic 3-D images in ordinary air, though to date, the best of these I’ve seen can manage only crude shapes that look like floating glowing pebbles.

 

If I had to make a sci-fi guess about how R2-D2’s “holoprojector” worked, I’d guess this last kind of volumetric display. If my guess is right, then in the fictional world of Star Wars, you would not want to piss off an R2 unit, as the sorts of lasers necessary to make this kind of image would be good at burning the retinas off the backs of your eyeballs in less time than it takes for you to blink, making R2 units much scarier than Jedi knights! :)

 

To understand why what a hologram does is possible, and its limitations, it’s necessary to understand what a hologram actually is. Various online articles, such as the wikipedia article “Holography” give good explanations of this.

[Mr. Peterman]

So that must mean this video is a fake. I don't have any idea how to tell if it is or isn't. I have an idea about how holographic film MIGHT be able to trick your eyes so to speak, but I'm not sure if it is possible.

 

YouTube - HOLOGRAGHIC TECHNOLIGY IS HERE COOL STUFF http://www.youtube.com/watch?v=5h8-c7D5yt8&feature=related

 

It comes from this place that says something like "What can your cell phone do?", so I don't know if people commonly make up stuff that they actually can't do.

[Turtle]

So that must mean this video is a fake. I don't have any idea how to tell if it is or isn't. I have an idea about how holographic film MIGHT be able to trick your eyes so to speak, but I'm not sure if it is possible.

 

YouTube - HOLOGRAGHIC TECHNOLIGY IS HERE COOL STUFF

 

It comes from this place that says something like "What can your cell phone do?", so I don't know if people commonly make up stuff that they actually can't do.

 

It's fake. A while back they showed a similiar fakery using cell phones to pop popcorn in a YouTube video. It's a marketing bit. Looks like it's workin'. :)