FTIR touchscreens

A PhD student at the University of Bath recently told me about a (relatively) new type of touchscreen, which relies on “Frustrated Total Internal Reflection”. (see here). Basically, Infra-Red light is shone down the inside of a sheet of acrylic. When something touches the acrylic, the light is reflected away from the object, where it can be picked up by a (slightly modified) webcam.

Found at http://www.whitenoiseaudio.com/touchlib/

This image shows what a webcam underneath the touch screen picks up (Image from http://www.whitenoiseaudio.com/touchlib/). This image can then be processed to pick out the bright “spots”, and the coordinates on the touch screen worked out.

The big advantage of using this method to detect interactions with the screen is that you are not limited to just 1 point of interaction at a time. For example, in a paint application, each finger could be a separate pen/ paintbrush. This also means that the number of users that are able to interact at the same time is only limited by space around the touchscreen.

These touchscreens are also relatively cheap to make. The main expense is a projector (which cost around £300), but all of the other components can be obtained for < £100. Someone has blogged their attempts to make a screen.

Below is a demo of a FTIR touchscreen:

Get the Flash Player to see this player.

And a link in case the player doesn’t work.

It also seems like there aren’t too many problems getting this to work in Ubuntu, so I’m hoping that I may be able to build one myself sometime soon 😀

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