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!)"

Comments

Just cross your eyes!

[dschuetz]

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."]

Re:Just cross your eyes!

[Anonymous Coward]

I've been a long-time semi-dabbler in stereophotography...

But clearly, you've not studied optics. The article is pretty clear about what is novel and what isn't, and rather than scholarly-looking, I'd say it was, in fact scholaraly.

In order for your brain to properly "fuse" the images together, your eyes will have to perform some tiresome calisthenics ...

Ah, no, the whole point is that you'll focus in front of the screen where the virual object will appear, as clearly depicted in figure 1. Because your eyes will be crossed, the image to be sent to your right eye will perforce be presented on the left side of the screen, and vice versa for the left eye.

The challenge for 3-D image display isn't blocking the "wrong" images from each eye ...

Um, yes, that is exactly what the challenge is: sending the right information to each eye. There are two possibly ways to do this, the first is to emit light at different points in 3d space (eg, with a spining mirror), the second is to send separate images to each eye. Perhaps it's a stretch, but it sounds like you've really not thought through the second possibility.

It all seems pretty useless to me.

When you find yourself writing this sort of comment (as opposed to a more authoritative one like, "this is without question wrong") it's a good sign that you've missed something.

Re:Just cross your eyes!

[i_am_nitrogen]

The lenticular screen idea is similar to what I thought of when I read about this; one could possibly manufacture a laptop screen with a strip of cellophane over every other vertical column, or possibly alternating columns with each row for a kind of "dithered" effect. This could allow normal viewing of 2D images without glasses, and 3D viewing with polarized glasses.

Re:Just cross your eyes!

[brakk]

You've got a lot of responses about what the cellophane is actually doing and random dot stereograph images so I won't go into that.

Here is a site that lets you see what it's like to just cross your eyes with two images displayed on the screen. (just click on the first icon by each pic, the one with the crossed eyes) What you are doing is trying to line up the two images to meet in the middle to make one 3d image. You will also be able to see an image on each side that if you try to look at you will loose the whole thing. These extra images are what the polarization blocks. It is really a neat effect, but your eyes get tired after a while. This is the same position your eyes are going to be in when you're using the laptop viewer here and you eyes are going to get just as tired just as fast.

Another idea

[cybermace5]

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.

Re:RTFA

[dschuetz]

No, because your right eye is wearing a polarizer that blacks out the right half of the screen and lets it see only the left half. See figure 3.

Yes, that's true, but your right eye isn't focused on (isn't pointing at) the left side of the screen -- it's looking where your left eye is, that is, at the right half of the screen, toed in to be where your brain knows the screen is.

So the only way this could work is if you focus your eyes at the center of the screen, and then maybe, your brain will fuse the images into one. Or you'll relax and eventually your eyes will automatically cross to do the fusing for you.

All this does, as another poster pointed out, is to help to hide the "phantom" images that you'd see, and potentially be confused by, when crossing your eyes. But when looking at one or the other image, the other one will always be a peripheral image, unless you cross your eyes to really focus on that side of the screen.

In practice, what you'll probably see with this is an image that sort of shimmers half clear and half black, and a near-duplicate of the image just to the side (perhaps one one side, perhaps on the other). I'll bet that actually fusing the images, in practice, will be difficult and not all that natural. They didn't have any photographs of people actually using their proposed apparatus, so I'm wondering if they didn't just come up with a cool idea, and write a paper about it, without actually testing it.

All questions of image fusing aside, as I also pointed out, I have a hard time believing that the cellophane wouldn't just turn half your screen black.

This has been around for years

[kinshadow]

This idea has been around for years. I first saw in the "Garage VR Handbook", which was published in the early 90's.