A Look Beneath the 'Surface'

Hajsky writes "Ars Technica takes a closer look at Microsoft's new "Surface" tabletop device. Turns out that Surface isn't actually a touchscreen at all, but uses five cameras located in the table's base to record movement and touch. 'The five cameras are near-infrared devices, but that's not because they are trying to read heat signatures from fingertips (or other body parts) on the table. Instead, it's because the entire surface of Surface is bathed in light; by illuminating the top of the table, the cameras can easily see when things are placed on it. Shining colored light across the surface of the table would spoil the effect that Microsoft wants, so near-infrared light is used for invisible illumination.' The whole setup runs on a Core 2 Duo and off-the-shelf hardware, and can handle 52 simultaneous touches." jfanning wrote with a link to an overview of similar technology used in the Helsinki 'CityWall'. The article she provides discusses the unique public display, and has an in-depth video on the way these kinds of setups work.

Comments

Jeff Han's work at NYU and Perspective Pixel

[orospakr]

Jeff Han lead project at NYU to produce multi-touch display technology and some demo applications.

Take a look at the original work at NYU: http://cs.nyu.edu/~jhan/ftirtouch/

And the spin-off company by the same guys to develop the technology: http://www.perspectivepixel.com/

Very cool stuff. If you look closely, you can tell that they're running it on GNU/Linux.

Hopefully, they'll chose to collaborate with the X and kernel guys to create proper generic interfaces for multi-touch pointing device input.

Re:Jeff Han's work at NYU and Perspective Pixel

[pelrun]

Actually, the touch technology is identical, FTIR (frustrated total internal reflection). You edgelight a perspex sheet with IR leds so the light bounces inside the sheet (total internal reflection, like an optical fibre), then wherever something touches the perspex the IR light is scattered from the touch point instead of continuing to be reflected (i.e. "frustrated"). Cameras watching the back of the screen then see light wherever the perspex is being touched.

The technology does not detect "varying degrees of force". It's actually a cheat that requires assuming you're using a finger - more of your fingertip squashes against the surface as you press harder, and that means the spot of light detected by the cameras gets larger. Measure the size of the spot and you can roughly map that to pressure.

Microsoft's table does seem to add an extra twist - "dominos" which have a detectable pattern of dots on the bottom, to identify objects placed on the table. That wouldn't be using FTIR, but it is still a well known technique.

DIY Multi Touch

[Picass0]

http://tinker.it/now/2007/02/28/multitouch-table-e xperiment/

        * 1 panel of plexiglass 8mm thickness
        * 2 strips of IR LEDs (18 LED per strip)
        * 2 sheets of tracing paper
        * 1 projector
        * 1 mirror
        * 1 analog camera sensitive to IR light
        * 1 IR filter for the camera
        * 1 computer

The traking was done using vvvv. http://vvvv.org/tiki-index.php

==============

Also See:
http://www.engadget.com/2007/03/01/build-your-own- multi-touch-table/
http://www.slashgear.com/make-your-own-multitouch- projected-table-284137.php

Re:Disappointing

[drinkypoo]

For instance, from what I understand (though I may very well be mistaken), the table can read various things on it. That's great, but your body (or any part of it) better not be obscuring the infrared bath, otherwise it will look like your arm also is supposed to be indexed on it.

The cameras and the IR light source are all inside of the table. You can see this from the diagrams. Nice try though.

Also, the whole multitouch thing seems a bit overrated. Now, before anyone jumps on my back, I understand its implications

If you understood the implications at all you would see that there are benefits for collaborative computing. Have you ever sat around a table (implying the involvement of others) with a pile of photos? Without multitouch you can't pull off the same level of interactivity with a computer screen.

Not only that, but the damned thing isn't all that new.

Yes yes, there are fairly ancient examples of similar interfaces - but none of them have made it to the home or even business market, so this is an utterly irrelevant datum.

Projector.

[pavon]

The article mentioned that the device uses a rear projector for the screen, so they could easily have the scattering surface (what the image is projected onto) be the topmost layer (or beneath a very thin protective layer), resting on top of the thick structural portion (transparent glass or plastic).

Resolution is XGA

[Namarrgon]

The projector resolution is currently 1024 x 768, according to the Popular Mechanics article. The "touchscreen" camera resolution works out to about 1280 x 960. Not exactly high; hopefully this can be improved by the time I need to replace my coffee table...

There's some good details in that article, a nice diagram and some more in-depth videos too.