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Creating 3D Computer Graphics From 2D HDTV Camera
photon jockey writes: "Everyone knows that holograms are cool! But these three dimensional images are hard to make and need special conditions to view. A group from The University of Tokyo have taken a step toward 3D displays with this paper in Optics Express.
Using a HDTV camera they effectively capture the light rays passing through a plane from a lit scene and then reconstruct the three dimensional geometry of the scene. Some pretty movies are available from the same page to show this. The paralax is limited by the size of the CCD and the distance to the object.
From the paper: In the field of computer graphics (CG),the use of real images has been attracting
attention as a method of attaining image synthesis that results in a more photo-realistic
quality. This field of technology is called image-based rendering. The authors have
attempted to solve this problem, by applying the approach of 3-D display technology,
in which light rays are the most primitive elements of visual cues.
"
The property of light you exploit when making of a hologram is called coherency, not polarization. That's why lasers are necessary, since polarized light could be also be generated with a bulb and a filter.
But it probably doesn't matter that much really, since the rest of your explanation also sounds a bit weird to me. I'm not an expert on holography, but AFAIK the trick is to capture not only the light intensity (as a photograph would) but also the phase information of the light (perhaps this is where you got that notion of polarization being necessary from). This is typically done by splitting a laser beam, and recording the interference patterns between the ray that hits the object and its undisturbed counterpart (something like that is only going to work with coherent light). On this interference pattern - which is captured on a special kind of film - a coherent lightsource can be used to reconstruct the entire phase information upon projection, which explains why a laser is also necessary to illuminate classical holograms.
This might not be a 100% correct description of the process, but it is probably more on the mark than your explanation. Then again, it might be not. Go dig up a physics book and check! :-)
Just my $0.2E-32
A.W.
It basically depends on polarization. All light is polarized, meaning that the electric wave and the magnetic wave that make up a photon are orthogonal (at right-angles within a plane) to each other. Most light is randomly polarized... that is, it bounces around at random with no structure to it. That's why lasers are commonly used in holography; it provides a polarized constant.
A traditional hologram is made by bouncing polarized light off an object (possibly from several different angles) and then exposing a piece of film to both the original, highly polarized light, and the light that is reflected off the object. When light is reflected, you change it's polarization to be (typically) parallel to the incident of reflection.
This makes miniature "grooves" in the image... they're virtual grooves, meaning they have no height, but all the same they selectively reflect only light of certain polarizations. Then, by shining the same type of polarized light on the exposed image, different angles of viewing select different polarizations, meaning different angles of viewing on the target object.
As for how this technology works, from what I can tell they're capturing the color and polarization of all the photons. This, combined with the width of the CCD, allows you to capture 3D information about the subject matter. If you were to add a source of polarized light to this thing, you could probably through the use of mirrors capture EVERY angle, just like a traditional hologram.
As a matter of fact, it doesn't even have to be visible light. Infrared will work fine, though you'll only get a rough gray-scale. But then, you don't need to be shining red/green/blue laser light around everywhere...
Won't the matrix people be mad at this! They spent Some Great Value Of Hard Earned Cash (SGVOHEC) to develop bullet-time, and now they can just use what turns out to be existing technology, making that expenditure of SGVOHEC a moot point.
Oh well, maybe the superbowl people will get with it next time so that my super-zooming rotating image of the QB won't jerk around like a 10-year-old computer trying to run quake...
I am disrespectful to dirt! Can you see that I am serious?!
something tells me this will bring a revolution to the kinds of RSI that can be obtained from playing Quake. I wish thee all happy hunting.
People replying to my sig annoy me. That's why I change it all the time.
www.opticsexpress.com, huh? Sure, maybe you can tell the boss they are "Optics Express" but we all know it's reall "Optic Sex Press". Motto: "Where girls push themselves against your eyeballs"
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