This prototype touch sensing system built in 2010 was developed as a retrofit solution to add touch sensing capabilities to normal displays. The system works by triangulating the finger position from a scanned laser beam. It has the ability to sense single point of touch and a refresh rate of about 160 Hz. The hardware was designed to be low cost, with estimated production cost of about 20 USD for each display.
Demo of mounting the sensors onto a display
Close up of laser sensing modules
The acquisition electronics