Tim wrote:
> These two links were posted on a forum I frequent. Ok yes one Bill Gates is in
> the first video but look past that and watch the video. Some of the stuff
> they are playing with in the second video is quite amazing
>
> http://www.youtube.com/watch?v=7WIkrQu0-v0
>
> http://www.youtube.com/watch?v=HD8Sg21m4AM&NR=1
>
> Tim
>
The technology involved in that is call FTIR - Frustrated Total Internal
Reflection.
It is actually surprisingly easy to make a touch screen like this - you
basically need a sheet of acrylic, some IR LEDs, a slightly modified
webcam and a projector. Some people have managed to build them (without
the projector) for well under £100.
The way it works is quite clever - several beams of IR light are shone
into the side of the acrylic sheet, and the webcam is placed behind the
sheet. When your finger presses on the sheet, it causes IR light to be
reflected towards the webcam, which, with a slightly modified lens, it
is able to pick up. This leaves you with an image consisting of several
blobs where your fingers are touching the screen. From there it is a
relatively simple algorithm to actually pick out the points of contact.
I've probably oversimplified something, or missed out bits, but that is
the general idea of how they work. More information can be found at
http://multitouch.nl/
and
http://nuigroup.com/
There is also the #ftir IRC channel on irc.freenode.net
Chris Oattes.
