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Detecting Ridge Slope and the Core of a Fingerprint

IP.com Disclosure Number: IPCOM000094075D
Original Publication Date: 1966-May-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Levine, WJ: AUTHOR [+2]

Abstract

This method of determining the core of a fingerprint by identifying the slope of each ridge crossed by a line scanner, detecting the ridges which have opposite slopes, selecting the two of these oppositely sloped ridges which come closest to each other as the inner most ridge, and investigating the recurring portion of the ridge to make sure no tail is thrusting upward as in the case of a bifurcation.

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Detecting Ridge Slope and the Core of a Fingerprint

This method of determining the core of a fingerprint by identifying the slope of each ridge crossed by a line scanner, detecting the ridges which have opposite slopes, selecting the two of these oppositely sloped ridges which come closest to each other as the inner most ridge, and investigating the recurring portion of the ridge to make sure no tail is thrusting upward as in the case of a bifurcation.

In order to detect the slope of a ridge, two devices are used which scan the image simultaneously. By being placed very close to each other, the output of one lags behind the other when the ridge crossed is not perpendicular to the direction of scanning, i.e., is inclined. The slope of the ridge crossed is stored temporarily until next ridge slope is determined.

If this ridge slope is identical to the previous ridge, it replaces the previous ridge in storage and the process is then repeated.

If this ridge slope is of opposite sign, then it is stored separately. Once a ridge is crossed, the distance or time to the next crossing is determined. When the next scan indicates a smaller distance between opposite slopes, the previous count is dropped. As the center, or core, is approached, the relationship between slope and distance reaches a minimum. On all but the center curve there is a curve with smaller readings.

The conditions for the center are opposite slope of adjacent scan crossings, minimum distance between thes...