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Using Cellophane For 3D Displays On Your Laptop
prestidigital writes "From the abstract:
[the authors] present a novel, inexpensive, stereoscopic technique for generating 3D displays from cellophane and a laptop computer screen.
(Once again my physnews update sends me email that doesn't suck!)"
Okay, I just had to respond to this. I've been a long-time semi-dabbler in stereophotography, and naturally anything 3-D related on /. just jumps right out at me (sorry about the pun). This article, while organized in a scholarly-looking fashion, really doesn't present anything new whatsoever. In fact, if I'm reading it correctly, you can achieve exactly the same results with no cellophane at all!
They talk a lot about cellophane having natural polarizing characteristics (I'd never heard that, but okay). Then they talk about how laptops have polarizers built into them -- sure, I've known that ever since the glasses for Starchaser: Legend of Orin made my digital watch look funky. Where their article breaks down is in the actual application of polarizing technology on the laptop.
They suggest putting the right eye's image on the left half of the screen, and the left eye's image on the right, then using polarizing filters to ensure that each eye only sees what's appropriate for it. Great. No problem. Except that there is one problem -- when your left eye is looking at the right half of the screen, your right eye is looking there, too!!
In order for your brain to properly "fuse" the images together, your eyes will have to perform some tiresome calisthenics -- that is, your left eye is going to have to turn slightly right, to face the right half of the screen, while your right eyes turns slightly left. Basically, you're crossing your eyes.
If you're just going to cross your eyes anyway, drop all the cumbersome cellophane goggles and overlays and crap, and simply look at two images side by side.
Also, I'm not convinced that placing a polarizer over half the screen wouldn't just turn that half of the screen totally black (as shown in figure 2 of the paper).
The challenge for 3-D image display isn't blocking the "wrong" images from each eye, it's blocking the wrong images when they're displayed in the same space -- overlaid in a single frame. For that, you need colors (anaglyphic glasses), or polarizing filters (again, though, both images displayed in the same space), or lcd shutters (multiplexing the images in time, rather than in color or polarization). Or you can use a lenticular screen, that bends the images left or right and draws them in a series of interlaced vertical stripes.
But not what they're suggesting here. It all seems pretty useless to me.
[obCaveat: "Unless I'm missing the point entirely."]
I believe displays that use this technique already exist, but couldn't you print a transparency with a special dot pattern, and place it over the laptop screen? The dots would be arranged so that the parallax from your eye spacing would block the pixels that the other eye can see. Laser printers have much more resolution than LCD screens, so you could adjust for the changing viewing angle from the center to the edges of the screen. You'd have to be able to control the distance from the mask to the screen pretty accurately, and there would be pretty much only one viewing position.
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