Amanda Ghassaei (previously featured on Arduino Blog with Glitchbox and Vocal Effect box ) published the instructions to build an Arduino-powered infrared touchscreen / coffee-table interface that she’s been using to control various music and graphics applications on her computer.

Although the project was done a while ago, she considers it special because it was her first Arduino/electronics project and recently she’s taken it apart to refinish the wood and fix a few things and then published detailed documentation on Instructables:

The touchscreen uses infrared (IR) sensing to detect fingers and other objects on the screen. An IR laser at each corner shines IR light across the surface of the screen. When a finger or other object touches the surface, it causes the IR light to scatter in many directions. Some of this light is directed down into the screen, towards an array of 64 IR sensors. By scanning through the sensors, you can determine the x and y position of the touch event(s) and use this to control a variety of apps.