How Does Multi-Touch Screen Technology Work?

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taylaron
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ok everybody,
recently I've come across some seriously amazing computer hardware and applications. I've viewed numerous sites with Jeff Hann demonstrating the Multi-Touch screen technology. I looked up frustrated internal reflection but i don't understand how it works and on what platform (OS). I'm unclear how this amazing technology works and why i am not hearing more about it than i already am.
please enlighten me.

one of the videos is on this link from Google
http://itsartmag.com/news/archives/919-New-Multi-touch-Computer-Screen-Demonstration.html

with a brief diagram of frustrated total internal reflection at
http://cs.nyu.edu/~jhan/ftirsense
 
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The idea is that you're bouncing light along a sheet of acrylic plastic. If you direct the light into the side of the sheet of acrylic at the right angles, it will repeatedly bounce off the inside surfaces of the acrylic, where it meets the air. All of the light energy will remain inside the acrylic. This is called total internal reflection. It's the same concept that allows fiber optic cables to work.

Keep in mind that the reason total internal reflection works is that there's a difference in the index of refraction between the acrylic and the surrounding air. The ratio of these indices is what determines the appropriate angles to use, etc.

If you put a finger on the surface, though, you spoil "frustrate" the total internal reflection, because the index of refraction of your finger is very much different than that of air. The result is that some of the light now gets out of the acrylic.

A camera views the rear side of the acrylic. Wherever it sees a spot of light, a finger was touching the acrylic.

The technology is not OS-dependent in any way -- it's just like a fancy mouse.

The reasons why you don't see it everywhere:

1) It's expensive.
2) It seems to make sense only for very large displays. Large LCD displays are expensive, too.
3) There really aren't that many consumer applications that demand the technology. As it becomes cheaper, of course companies will begin integrating it anyway, because it's a lot of fun!

- Warren