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Contactless Optical Scanning of Fingerprints with 180° View

J. Palma, C. Liessner, S. Mil’shtein

Advanced Electronic Technology Center, Electrical and Computer Engineering Department, University of Massachusetts, Lowell, Massachusetts, USA

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Summary: Fingerprint recognition technology is an integral part of criminal investigations. It is the basis for the design of numerous security systems in both the private and public sectors. In a recent study emulating the fingerprinting procedure with widely used optical scanners, it was found that, on average, the distance between ridges decreases about 20% when a finger is positioned on a scanner. Using calibrated silicon pressure sensors, the authors scanned the distribution of pressure across a finger, pixel by pixel, and also generated maps of the average pressure distribution during fingerprinting. Controlled loading of a finger demonstrated that it is impossible to reproduce the same distribution of pressure across a given finger during repeated fingerprinting procedures. Based on this study, a novel method of scanning the fingerprint with more than a 180° view was developed. Using a camera rotated around the finger, small slices of the entire image of the finger were acquired. Equal sized slices of the image were processed with a special program assembling a more than 180° view of the finger. Comparison of two images of the same fingerprint, namely the registered and actual images, could be performed by a new algorithm based on the symmetry of the correlation function. The novel method is the first contactless optical scanning technique to view 180° of a fingerprint without moving the finger. In a machine which is under design, it is expected that the full view of one finger would be acquired in about a second.

Key words: biometrics, fingerprints, optical scanning

PACS: 07.60.-j, 87.59.-e, 87.80.+s