Seigo Igaki

Real-time fingerprint sensor using a hologram

A holographic fingerprint sensor has been developed for a system that identifies a person by his or her fingerprints. The sensor uses a laser as its light source and consists of a light-conducting plate, which is a transparent glass plate with a plain grating-type hologram, and a focusing lens system just under the hologram. Since the sensor uses a plane-parallel plate, all the optical paths from each point of a fingerprint to the hologram are equal, and a bright fingerprint can be created without the trapezoidal distortion that is inherent in conventional prism-type sensors.

Moving-window algorithm for fast fingerprint verification

Fingerprint verification as a means of identification requires speed and reliability. The authors describe a moving-window algorithm that is developed to fulfil these requirements. This algorithm uses pattern matching of the images of the areas around each minutia. It is fast and uses a stepping-stone scan. It verifies thin-ridged fingerprints, whose acceptance rate gets low with the stepping-stone scan, by moving the start point of the scan. The authors tested this method by computer simulation. This technique verifies fingerprints in an average of 0.7 s and at a maximum of 3 s. However, the average time that a person is kept waiting is 0.3 s, and the longest waiting time is less than 1 s. It is concluded that the average recognition time is less than 0.2 s. An average acceptance rate of 97.0% is achieved.<<ETX>>

Holographic Fingerprint Sensor

The fingerprint sensor that we developed uses a hologram. Two requirements are important for actual use; laser safety and high-contrast images. The illumination method we developed uses total reflection and a new type of detection. For safety, total-reflection lighting ensures that laser beams cannot enter an operators eyes. To obtain high-contrast images, signal and noise light were separated.