Flat-Panel Displays Get Touchy

Touchscreens are back in vogue with flat-panel display makers, if the prototypes on show at the FPD Expo in Yokohama this week are anything to go by.

Gone are the clunky screens that relied on a touch layer added over the display, and in are models that integrate the sensor elements into the display itself. That means the displays are brighter, thinner and in many cases more responsive. It also means that some can offer a "multi-touch" capability similar to that of Apple Inc.'s iPhone.

The largest of the multi-touch screens on display was a 47-inch model from LG.Philips LCD Co. Ltd. that attracted a crowd thanks to the same novelty feature that's been amusing iPhone owners for a few months: the ability to zoom in and out of images with two fingers. In this case the display showed satellite images from Google Maps, so many show-goers used the screen to find and zoom-in on their own home, thus unwittingly letting all those around know where they live.

Taiwan's AU Optronics Corp. had a pair of 4.3-inch panels on display. One used a voltage-sensing touch system and the other relied on a charge-sensing touch system. The same photo zoom technique was being demonstrated on the two screens. The former appeared much more responsive but comes with a catch: it can be operated with a fingernail but not a finger. Conversely, the charge system worked fine with a finger but didn't respond when touched with a fingernail.

Japan's Sharp Corp. also attracted a crowd with a multi-touch screen that it first debuted earlier this month at the Ceatec show. The 3.5-inch screen integrates an optical scanner pixel alongside each LCD pixel, so it can not only recognize the location of multiple fingers but also be used to scan name cards and the like.

Integrating image sensor pixels along side LCD pixels in screens isn't new. Toshiba Matsushita Display Technology Co. Ltd. unveiled such a prototype at the Electronic Display Expo in Tokyo in 2003 but not much was heard of it since.

At FPD Expo, which began Wednesday, the company was demonstrating its latest prototypes and admitted that it had let rivals catch-up on its lead. The screens have failed to take off partly because panel makers don't have sophisticated enough software libraries to work with the displays.

That means consumer electronics makers have to do a fair amount of software work to interface with the screens, and that's a hurdle to adoption, said Yutaka Okada, a spokesman for the company, which is a joint venture between Toshiba Corp. and Matsushita Electric Industrial Co. Ltd. (Panasonic).

The latest prototypes work by sensing either light or shadow. The light-sensing model responded to a light pen and allowed users to perform such tasks as draw on a picture displayed on the screen, while the shadow sensing model could be operated with a finger. The latter has the advantage of working well in both bright and dark conditions and doesn't even require the user to physically touch the screen. Just bringing a finger within a few millimeters of the display is enough for it to respond.

Despite the large number of prototypes on display, none of the companies would say when a product might be on the market.