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CHIBA, JAPAN -- Casio Computer has developed a fingerprint sensor layered on top of a 1.2-inch LCD screen, providing a convenient way for phone makers to incorporate biometric security into their handsets, a Casio official said this week at the Ceatec 2004 show here.

"This is the world's first combined LCD screen and fingerprint scanner," claims Jerry Schroeder, a senior engineer with Casio's U.S. division, who demonstrated a prototype of the scanner mounted on a mobile phone at Casio's booth. "It's still under development, but we see applications across a lot of devices."

Incorporating the technology into the display of a mobile phone will help manufacturers save space, which is at a premium on such devices, Schroeder says.

Some cellular telephones in Japan already use fingerprint scanners to provide added data protection, such as Fujitsu's F900i handset offered by NTT DoCoMo.

Optical Sensors

The LCD-type scanner consists of a layer of optical sensors on a 0.7 millimeter-thick sensor substrate, which in turn sits on top of a conventional TFT LCD, says Yasuo Mochizuki, deputy general manager of Casio's device division.

The layer contains thousands of optical sensors, he says, although he didn't say exactly how many were in the demonstration model.

This differs from other biometric scanners which often use a CCD (charge-coupled device) sensor to capture images of fingerprints, or a capacitor-type system that "reads" the ridges and troughs of a fingerprint through variations in the electrical charges produced where the finger touches the sensor.

Mobile phones and PDAs are the initial targets for Casio's fingerprint reader, but Casio hopes it will find a home in any device that requires an extra level of user authentication beyond a password, says Mochizuki.

Superior Technology?

The sensor technology is superior to CCD or capacitor-type systems, according to Mochizuki. CCD sensors tend to have problems reading ink-stained or dirty fingerprints, and capacitor types are poor at reading a print when the skin on the finger is very dry, he says. Casio's LCD approach suffers neither of these drawbacks, he says.

"The light sensors are very close to the skin and able to distinguish the groves in the fingerprint very finely. It's a much better solution," he says.

The sensor technology is complete and could be commercialized within a few months, although the necessary driver chips are still being developed, meaning the technology is unlikely to find its way into products for 12 months to 18 months, he says.

Ceatec, properly known as the Combined Exhibition of Advanced Technologies Providing Image, Information and Communications, runs until Saturday.