Microsoft surface used DI (Direct illumination) technique in his table in which IR rays are passed from below the projection surface (the screen which you touch). When there is some object, including human touch, on the glass IR is reflected back and is being captured by array of IR cameras which is further being processed by vision system and interpreted as touch.
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Having advantage of Object recognition (termed as tag recognition) this technology cannot be used when you are using LCD for your table. Reason, in this method the IR has to pass the LCD 2 times which makes then week while reaching back to camera.
The best approaches known for LCD based Table are LLP (Light Laser Plane) and FTIR (Frustrated Total Internal Reflection).
In LLP method a laser Light is being spread over the screen and when some object is placed it is illuminated and is captured by camera. Being best method the draw backs are Laser can be harmful if by mishap is penetrating to cornea (there may be some other health issues but I have not researched through them. The other drawback is the corners or the edges of the screen has to be protruded to accommodate laser light which is not a good design for coffee table or if you are needing a plane surface.
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So I have left with FTIR method. The major drawback of this method is it could not recognize tags or objects. Hmmm, is it really needed for your first project? The other draw back is, it asks much labor (at least I found that) and specific material.
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In this method IR is passed through edges of Acrylic, due to specific Total Internal Reflection property of Acrylic IR rays cannot move out of the sheet and when touch is made the IR is frustrated and reflected to Camera below. To achieve better reflection either you have to put some compliant surface over the sheet of you need wet hands (via water or oil). I may use Silicon spray for compliant surface.
This is the Surface part now comes the display. A projector or a LCD can be used to display contents on surface. Microsoft uses Projector which will cost much more for a RnD stuff so I am using a 18.5 LCD screen.
Below the projection surface a IR camera (or a modified camera to see IR) is needed to track the reflected IRs.
This is the hardware scheme, now the software. The tracker software tracks images reflected back from surface and creates usable images and then the contact points are converted into blob (Blob is a image created by the touch reflection) then these blobs are converted into messages which can be used by client applications do what they want. Most common tracker software are CCV, touchlib, Vision system etc.
Microsoft surface his own vision system software to track images and convert them into windows messages and tags. Microsoft Surface SDK utilize these messages (and tags) to create application. If you don't have windows 7 or you don't want Microsoft surface solution then you can use CCV, touchlib etc. to track IR images and create blobs from them. If you want to use Microsoft surface software (which is hell hard to find) you must have a best configuration system.
Thanks to Daniel D for creating HID drivers that can be used to send messages and now we can use Microsoft Surface without his Vision system (I am sure Daniel will come up with a solution for Tag recognition).
