Fujitsu has developed a touchscreen designed to make the displays of mobile devices such as PDAs brighter and easier to read.

Touchscreens sit on top of the light-emitting screen and the brightness of the display therefore depends on the transparency of the touchscreen element. The closer the screen to 100 percent transparency, the clearer the display. This is important in PDAs because of their combination of high resolution, colour and detail.

The new screen from Fujitsu is 0.7mm thick and has a light transparency ratio of 98 percent, compared to a conventional touch-screen's ratio of between 82 and 86 percent. The product is expected to reach the market by the second half of 2003.

Touchscreens are currently made from resistive film and their transparency is limited. Fujitsu’s version uses transducers to turn electrical signals into SAWs (surface acoustic waves) and direct them towards receivers at the far side of the screen. When the screen is touched at a particular location, the SAW is partially blocked. The exact location at which the pressure was applied can be deduced from the new shape of the SAWs as they are picked up by the receiving transducers.

One of the bottlenecks of this technology had been the large size of the piezoelectric thin-film transducer. Fujitsu engineers have redesigned the transducer and are now able to house it in a half-sized 1.4mm panel frame.