Create multi touch display for full light
Most multi-touch displays have some form of an input unit, and a display.  

The display can be a front-screen projector, a rear-screen projector, or a flat panel (LCD or plasma).  These are all well understood technologies, and your choice will be driven by cost and how it interacts with the input unit.

The input unit can have more implementations.  When I write 'light' understand that it can be visible light or infrared.


Rear-projected light, reflected by touch points, read by rear camera.
Front-projected light, interrupted by touch points, read by rear camera.
Front-projected light, reflected by the surface, interrupted by touch points, read by front camera.
Side-mounted LEDs and photo-transistors, with row/column scanning.
Touch-sensitive, capacitive grid.


That's just what I can think of off the top of my head.  Any of the back-projection modes can use visible light; for front-projection you'll be better off using infrared.

For a more in-depth review, I suggest you do more research here:


http://en.wikipedia.org/wiki/Multi-touch
http://multi-touchscreen.com/
http://www.billbuxton.com/multitouchOverview.html
http://electronics.howstuffworks.com/iphone2.htm
http://www.google.com/search?hl=en&amp;q=multi-touch+technology