Laptop using rear illumination to add multi touch to an off the shelf laptop.
Granted not very practical at the moment, due to the hacking of the screen

http://www.istartedsomething.com/20070620/msr-multi-touch-laptop/

check out this topic nick …
http://nuigroup.com/forums/viewthread/379/

its already been posted
but i do wonder what kind of sensors is being used…

Sorry about that, must have missed the post.

I wondered if it was using LEDs as sensors, which is mentioned on Jeff Hans site http://cs.nyu.edu/~jhan/ledtouch/index.html, because there is not a lot of space for a camera or anything like that.

Nick - 25 June 2007 04:53 AM

Sorry about that, must have missed the post.

I wondered if it was using LEDs as sensors, which is mentioned on Jeff Hans site http://cs.nyu.edu/~jhan/ledtouch/index.html, because there is not a lot of space for a camera or anything like that.

perhaps some old (large, low res) ccd/cmos… LED sensors seem to take more space.

I think it was using the LEDs as the sensors themselves. When light is reflected back into a normal LED, a small electrical current is generated. The LED’s are probably connected to some sort of advanced power supply that monitors the small amounts of electricity the LEDs generate from the reflected light. Then that data is fed to a computer that displays this data in real time.

This is really interesting.  Using triangulation techniques, you can get away with a much smaller actual sensor resolution, and still achieve a relatively high effective resolution.  This could easily be manufactured into a wafer thin PCB with Surface Mount IR detectors and/or IR LEDs in a simple matrix.