Mobile devices including phones could be more secure in the future, now that engineers at Fujitsu have completed development of a compact fingerprint sensor designed for use with handsets.
Until now, fingerprint sensor devices have been too large and consumed too much power to be integrated into mobile devices. There are also issues of high cost and questionable reliability, said Chiaki Kuwahara for Fujitsu.
Fujitsu engineers chose to use a capacitance-based sensor system, having rejected the two other main types of sensor — thermal and optical scanners, which are prone to incorrect readings because of interference from external sources of heat and light respectively.
The new capacitance-based scanner has a sensor array which is able to detect ridges and valleys in a fingerprint by measuring the difference in capacitance across the array when a finger is brought into contact with it, Kuwahara said. However, such sensors are usually too large to use in a mobile phone and the main challenge has been making them smaller, Kuwahara said.
Fujitsu solved the problem by switching from a sensor that would scan the whole finger in one pass to a sensor over which the finger needs to be traced. By doing this, the sensor can be made small enough to fit into a mobile.
"By adopting the tracing style, the size is reduced and so is the production cost," Kuwahara said.
The MBF 300 sensor has a surface area of 60.2 sq mm, which is 10 times smaller than the existing Fujitsu sensor, and consumes less than 10 milliamperes, according to the company.