Patents and FTIR:

Prior Art:
The clearest example of prior art identified thus far is Richard Greene’s Drawing Prism.  He used FTIR to interface with a computer in 1984.  He was specifically interested in using internal reflection to see things like the breadth of a brushstroke or the number of hairs within it.  He focused on visible light (but did mention the ability to use it with IR with the right filters) and digital art applications.
http://freepatentsonline.com/4561017.pdf

The Digital Desk (’91) provides some nice examples of a touch-driven interface with a camera and projector.
http://video.google.com/videopopup?q=http://vp.video.google.com/videodownload?version=0&secureurl=tgAAAJBoNfJKz4ySfAZ55TRDlMm_RhTzoNNeohhOuqxSxhTgEfwERmABJLj0X_vnhlJekqR8FoxO6csOqYqMYIciNiLKzQqEm1_qfgEWPiqDRUSdSbmtOl-kfD0ZLwMhWQnuP7RpAgXH0wJrw8pMGrN50YaYTg_KEyvLyMNotpSBeElfQmqUCsjrNKv34bWgaIE1h_U5-be8N0I6q9uzaA73DtYQR2jdJ4BxOg0NoCj1QkxzVp6pgwE5NaQWHw066hmEAg&sigh=cozLk5SfbulgT6XQV4ZBU8gQEQ8&begin=1829&len=484933&docid=5772530828816089246&docid=5772530828816089246&fscid=fsc_604838419&windowtitle=Digital+Desk+by+Pierre+Wellner+-+Google+Video+-+Full+Screen

Current patents with claims in FTIR:

This May 2000 patent by David Tulbert of Canada claims the use of FTIR as a multitouch medium.  He uses FTIR in conjunction with backlighting.  He calculates the size and shape of the FTIR print in relation to that of the backlit finger to determine how much pressure has been applied and the angle of force.
http://www.freepatentsonline.com/20030137494.pdf

This November 2001 patent by Klony Lieberman et al. of Israel claims everything under the sun regarding camera-based touch screens.  It’s quite long and convoluted, but makes a few references to FTIR as a claim.
http://freepatentsonline.com/20040108990.pdf

A December 1996 patent by Ken Fujimoto of Los Angeles claims creating an FTIR screen with a back diffuser and external light source.  He projects light onto the diffuser, which sends it up into the acrylic for FTIR.
http://www.freepatentsonline.com/6061177.pdf