(This might belong in "Mad Science", but it pertains to RPTV)
Now I've never taken a RPTV apart, but I understand the basic principles of how it works. I've been looking at these Interactive Multi-Touch Coffee Tables, and they are basically a RPTV laid on it's back, then with the use of IR LEDs and a mod'ed web cam, you can make yourself the multi-touch input. Now all I've seen are people who build custom enclosures based off the principle of a RPTV, but they use a video projector to create the image on the back of the screen material.

My question is, could a RPTV be converted to one of these interactive tables? I've heard that the back of the screen is a big Fresnel lens (which wouldnt work with the camera), is this true? Do some models just have a video projector shine right onto the screen w/o the large lens? I'll need to be able to have a camera see that back of the viewing screen w/o obstructions.

The idea sound great for large strategy games. Here's some plans from Christopher jette. These are for a 60" rptv version. From a straight physics perspective this looks like a simple mod to an existing DIY RPTV. There may be some sag issues in putting it horizontally but that's what DIY is all about.

I currently have a 60" RPTV DIY projector and might give it a try myself.