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Technology Marches On! 3D-TV.

Discussion in 'LCD & LED LCD TVs' started by jimsan, Apr 14, 2005.

  1. jimsan

    jimsan
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    Just been Googling around and came across an article on LCD advances.....

    Seems that Philips are developing an LCD screen that is actually 3D! The front of the screen has a very fine array of tiny bubble-like lenses that means that your left eye sees a slightly different image from your right eye. This doesn't require special specs or anything and can be watched from any angle and by as many people as you can get in the room!

    Resolution isn't great yet, and I suspect that the picture might take some getting used to....but, my goodness, what next? Hologram TV may not be that far off!

    http://www.research.philips.com/technologies/display/3d/index.html

    Jimmy
     
  2. NicolasB

    NicolasB
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    If you stop and think about that for a moment, you'll realise that it's physically impossible. For a stereoscopic 3D display to work without glasses, the left-eye and right-eye images have to be fed directly to the viewer's eyes - in other words, at the point in space where his left eye is, it must only be possible to view the left-eye image, and at the point in space where his right eye is, it must only be possible to view the right-eye image.

    If the viewer moves his head a few inches to the left, so that his right-eye ends up where his left eye was just now, then he must be viewing the left-eye image with his right eye, and the effect stops working.

    Screens like this have been around for several years, incidentally.
     
  3. jimsan

    jimsan
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    When I read the article, I was also somewhat perplexed about issues like this. Did you read the piece yourself, Nicolas? They go to great lengths to explain how it works, and I have a fairly open technical mind, but I'm damned if I can understand it!

    Jimmy
     
  4. NicolasB

    NicolasB
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    Well, I skimmed it. I've seen similar articles about similar screens in the past.

    The way they work is quite simple. You have a series of vertical cylindrical lenses in front of each column of pixels. The effect of this is that the image of that column of pixels is only visible from certain angles and not from others.

    I'm sure you must have seen one of those pictures where there are two different pictures that you can see depending on where you're standing - you move your head to and fro (or tilt the picture to and fro) and it shifts from one picture to the other. They've been doing that with children's toys for many years (often a happy face and a sad face of the same cartoon character, or something like that) and, more recently, they've done it with posters too.

    That's basically doing the same thing. The picture is divided up into vertical strips. The odd-numbered strips show one of the pictures. The even-numbered strips show the other one. The cylindrical lenses are arranged so that, from any given angle, you either see only the odd-numbered strips (apparently edge-to-edge), or only the even-numbered strips.

    With the 3D screen the effect is the same except that the places where you can see the two different images from are closer together. So, with your head in the correct position, one eye is seeing the odd-numbered pixel columns, and the other eye is seeing the even-numbered ones.

    They're obviously experimenting with the geometry of the lenses so as to try and make more places in the room where you can stand and have it work correctly. With the earliest screens like this you had to be a specific distance away from the screen as well as directly in front of it. Here there are several different viewing angles, and the viewing distance doesn't have to be so precise. But you still have to be standing in a place where the correct images coincide with the position of your eyes.
     
  5. jimsan

    jimsan
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    Yup, I understand all that, but it seems to me that it's really only going to be a good way to get a migrain!

    Jimmy
     
  6. NicolasB

    NicolasB
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    Pretty much all 3D imaging systems eventually lead to eyestrain. It's not as bad as it was with the early "virtual reality" systems - they had such a low frame-rate that there was a perceptible lag between moving your head and the image updating, which actually gave a lot of people motion sickness.

    But any stereoscopic system will always eventually lead to eyestrain simply because the image isn't truly three-dimensional. That means that what your brain thinks is going on in stereoscopic terms doesn't agree with what your eyes need to do to look at it, either in terms of convergence, or in terms of focusing.

    The closest you can get to "true" 3D in that respect is a hologram - but you can't do holograms in real time (or at least not yet). I do remember hearing (while I was at university) about a system that attempted to produce a real-time holographic image by using an acousto-optic modulator. This works by introducing carefully controlled sound waves into a certain type of crystal. As the sound passes through it creates alternate regions of compression and rarefaction and, in certain types of crystals, that leads to variations in refractive index, so the whole thing effectively becomes a dynamically controllable diffraction grating. At the time the resolution they could achieve was absolutely miserable (I mean 20x20 pixels, or something) That was... 12 years ago, maybe? But even so, I'm not persuaded that it'll ever be functionally useful.

    Holograms look really cool, but sadly they have some rather significant limitations. In particular, the standard science-fiction-film thing of a holographic projector - a 3D image projected into empty space - is impossible: by their nature, holograms depend on a solid surface to work.

    Other approaches I've heard about include a conventional display surface that rapidly rotates so that the screen is actually physically different distances from you while displaying elements of the picture that are supposed to be different distances from the eye. And I've also heard of a fascinating idea using non-linear optics. Under the right circumstances some materials can cause two non-visible infra-red photons to combine into a single visible photon. By shining infra-red beams through a large chunk of this material, and switching beams on and off so as to control which regions of the material have two beams intersecting and which don't, you could end up with a genuinely 3-dimensional image within the device. (But it would be transparent - there's no way for a voxel closer to you to obscure anything behind it).

    Personally I'd like to see people going back to a VR-style display. All of the various systems since then (like this Philips display, or shutter glasses, or red/blue glasses, or even autostereograms) all deal only with the stereoscopic aspect of VR. To my mind the much more significant aspect of VR is the ability to track head movements and update the view accordingly. With any other system, as soon as you move your head, the 3D illusion is destroyed, because you don't get the correct parallax. And from a domestic display point of view it makes the difference between looking at a 3D world through a small window and being completely inside it.
     
  7. jimsan

    jimsan
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    It all makes the mind boggle! You have obviously immersed yourself in this to a fairly extensive degree, so I am struggling to keep up!

    To my mind, the hologram thing, as you say, is a bit of a non starter, as you need a substrate to project onto, and air probably isn't it. However, the idea of intersecting beams from three or four different locuses would seem plausible.

    I had always imagined that the best way would be to have something like a tranparent three dimensional LCD-like block of gawd-knows-what that would have a true X-Y-Z field of light emmitting gizmos that could produce a true, walk-around 3D image.

    I should be working on Dr.Who!

    Jimmy
     
  8. NicolasB

    NicolasB
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    Not so much these days, but the official title of my university degree is "BSc (Hons) Laser Physics and Optoelectronics" - this was basically a normal Physics degree, but with some extras on things like lasers and non-linear optics (for which the University of St Andrews was recognised as being a national centre of excellence at that time).

    Maintaining sub-micron accurate markings in the surface of a gas is certainly not a simple task. :)

    The thing I was talking about with infra-red beams wouldn't work in air either. That's an example of non-linear optics, which only works in certain very specific types of material (crystals, usually - possibly also glasses, I forget).

    It would be very difficult to use LCD because that works by the LCD panel occluding an always-on backlight, and you'd have to have the light shining through several hundred LCD layers unaffected before being blocked by the one active cell. It's similarly difficult to use LEDs, or some type of individually-wired light-emitter, because the structure of each emitting cell would tend to obscure light coming from an LED behind it. (That's an awful lot of wires, anyway!

    All in all, some type of stereoscopic system is likely to be much less hard work!

    Or maybe we should go back to using 18th century technology and project images on carefully controlled clouds of smoke. :)
     
  9. jimsan

    jimsan
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    I reckon we just need a couple more days of this techno chit-chat and we'll get it sussed!

    The Solid block of whatever would have to be something akin to a 3D CRT or Plasma ball type of thing where regularly arranged invisible particles could be activated by remote 3 axis 'guns' firing charges of some sort that intersected with other guns at a certain XYZ location....this need not be a cube, of course, but perhaps just a 2 -3inch thick panel. A cube would be preferable, however, to allow the true 'walk around' experience!

    Have I got the job yet?

    Jimmy.
     
  10. Flimber

    Flimber
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    Face it, someone's going to have a right laugh reading this thread in 10 years. I need provide no more detail than that (do I ?).

    Mike.
     
  11. jimsan

    jimsan
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    Hi Mike,

    I'm having a right laugh writing it! It's just my overactive imagination running riot. Hey, you never know, this could all be an amazing prophecy of what we might actually have! Doubt it though....I expect in 10 years time we'll all just be watching really good High Definition 2D images on superb SED (or similar) panels. Bet you that the Ambilight will have recieved some major attention by then though.....this is a feature that will grow and grow.

    Now, in say 30 years time......

    Jimmy
     

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