Contactless optical scanning of fingerprints with 180 degrees view

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 degrees 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 degrees 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 degrees 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.