Optical methods of biometric identification by ...

Optical methods of biometric identification by fingerprints In ancient times fingerprints were used as a person`s identity check means. They were used to "sign" various state documents and were left on clay plates and stamps. At the end of the 19th century fingerprints came into use in criminalistics. Nowadays, owing to the development of electronic technologies, identification by fingerprints is used in various other spheres that require effective safeguarding - access control systems, voting systems, electronic payments, information security (network access, access to a personal computer), etc. Fingerprints are relief lines, or the so-called papillary patterns. Their structure is conditioned by rows of ridge-like eminences of the skin separated with grooves. There are several algorithms of fingerprints identification. The most popular of them is the one based on details detection. Optical is one of the existing electronic methods of fingerprints obtaining. Scanners of various types are used nowadays to obtain fingerprints with the optical method. FTIR scanners are devices using the frustrated total internal reflection effect. The effect consists in division of light energy into two parts in case of interface light incidence. The energy divides into two parts, one of which reflects from the interface, and the other penetrates through the interface into the second environment. The proportion of the reflected energy depends on the angle of light flux incidence. Starting with a certain degree of the angle all the light energy reflects from the interface. This phenomenon is called total internal reflection. In case of contact of a denser optical environment (a finger in our case) with a less dense one (i.e. with a prism surface) the light beam penetrates through the interface at the point of full internal reflection. Thus only the beams getting at full internal reflection points to which the papillary pattern of the finger was not applied will reflect from the interface. A special image sensor (CMOS or CCD) is used to capture the obtained light picture of the finger surface. Fiberglass scanners are fiber-optic matrices in which all the waveguides at the output are connected to light detectors. The sensitivity of each detector allows fixation of the trace light penetrating through the finger at the point of the finger contact with the matrix surface. Electro-optical scanners` technology is based on use ...

Category:

Science & Technology