Fingerprint fingertip orientation detection method and device

• US 5,848,176 A
• Filed: 04/04/1996
• Issued: 12/08/1998
• Est. Priority Date: 04/04/1995
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Sato, Kan, Hara, Masanori
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): MEHTA, BHAVESH M
• Application Number:
  US08/628,242
• Time in Patent Office: 978 Days
• Field of Search: 382/124-126, 382/115, 356/71
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1347 Preprocessing; Feature extraction

Abstract

The present invention has the object of accurately detecting fingerprint fingertip orientation by a process of calculating inner products of ridge directions in the peripheral areas of an inputted fingerprint and radial line directions, finding an inner product sequence in which the inner products are sequenced upon making one revolution from a certain initial point, finding sequence errors between the inner product sequence and a plurality of inner product sequence patterns of differing fingertip orientations for a standard fingerprint, and establishing the fingertip orientation of the inputted fingerprint as the fingertip orientation of the standard fingerprint having the minimum sequence error.

Claims

1. A fingerprint fingertip orientation detection method comprising the steps of:

storing a plurality of inner product sequence patterns for differing fingertip orientations for a standard fingerprint;

calculating inner products of ridge directions and radial line directions around a circumference of an inputted fingerprint, finding an inner product sequence in which said inner products are sequenced upon completing one revolution from a certain initial point, and finding sequence errors between the inner product sequence and each of the stored plurality of inner product sequence patterns for differing fingertip orientations for a standard fingerprint; and

taking as the fingerprint orientation of the inputted fingerprint the fingerprint orientation of a standard fingerprint for which said sequence error is a minimum.

2. A fingerprint fingertip orientation detection method according to claim 1 wherein a plurality of typical fingerprints having differing patterns are used as standard fingerprints.

3. A fingerprint fingertip orientation detection method according to claim 2 wherein a plurality of fingerprints of the same pattern type are averaged and used as a typical fingerprint.

4. A fingerprint fingertip orientation detection method comprising the steps of:

storing a plurality of inner product sequence patterns for differing fingertip orientations for a standard fingerprint;

calculating inner products of ridge directions and radial line directions around a circumference of an inputted fingerprint, finding an inner product sequence in which said inner products are sequenced upon making one revolution from a certain initial point, and finding cross-correlation between the inner product sequence and each of the stored plurality of inner product sequence patterns for differing fingertip orientations for a standard fingerprint; and

taking as the fingerprint orientation of the inputted fingerprint the fingerprint orientation of a standard fingerprint for which said cross-correlation is a maximum.

5. A fingerprint fingertip orientation detection method according to claim 4 wherein a plurality of typical fingerprints having differing patterns are used as standard fingerprints.

6. A fingerprint fingertip orientation detection method according to claim 5 wherein a plurality of fingerprints of the same pattern type are averaged and used as a typical fingerprint.

7. A fingerprint fingertip orientation detection device comprising:

a ridge direction storage section that registers fingerprint ridge directions existing in picture elements of an inputted fingerprint image that has been quantized into picture elements of two-dimensional array form;

a fingerprint center coordinate storage section that registers center coordinates of an inputted fingerprint image;

an inner product sequence pattern dictionary that registers in advance inner product sequence patterns that are defined for a plurality of fingerprints serving as standards and fingertip orientations corresponding to these inner product sequence patterns;

an inner product sequence calculation section that calculates, from fingerprint ridge directions in picture elements of an inputted fingerprint image stored in said ridge direction storage section and from center coordinates stored in said fingerprint center coordinate storage section, inner products of radial line directions and ridge directions at coordinate values separated from the center coordinates by a fixed distance on radial lines, and finds an inner product sequence in which results of one revolution from a particular initial point are sequenced;

an inner product sequence temporary storage section that registers inner product sequences found in said inner product sequence calculation section;

an inner product sequence error calculation section that finds a plurality of sequence errors for each of a plurality of fingerprints that serve as standards by finding sequence errors by comparing inner product sequences of inputted fingerprint images registered in said inner product sequence temporary storage section with a plurality of inner product sequence patterns of fingerprints that serve as standards registered in said inner product sequence pattern dictionary while varying fingertip orientation by rotating the inner product sequence patterns of fingerprints serving as standards;

a sequence error temporary storage section that registers each sequence error found using said inner product sequence error calculation section and a corresponding fingertip orientation;

an orientation detection section that outputs fingertip orientations corresponding to a sequence error having a minimum value among those registered in said sequence error temporary storage section; and

a control section that controls timing of each operation of said inner product sequence calculation section, inner product sequence error calculation section, and orientation detection section.

8. A fingerprint fingertip orientation detection device comprising:

a ridge direction storage section that registers fingerprint ridge directions existing in picture elements of an inputted fingerprint image that has been quantized into picture elements of two-dimensional array form;

a fingerprint center coordinate storage section that registers center coordinates of an inputted fingerprint image;

an inner product sequence pattern dictionary that registers in advance inner product sequence patterns that are defined for a plurality of fingerprints serving as standards and fingertip orientations corresponding to these inner product sequence patterns;

an inner product sequence calculation section that calculates, from fingerprint ridge directions in picture elements of an inputted fingerprint image stored in said ridge direction storage section and from center coordinates stored in said fingerprint center coordinate storage section, inner products of radial line directions and ridge directions at coordinate values separated from the center coordinates by a fixed distance on radial lines, and finds an inner product sequence in which results of one revolution from a particular initial point are sequenced;

an inner product sequence temporary storage section that registers inner product sequences found in said inner product sequence calculation section;

an inner product sequence error calculation section that finds a plurality of cross-correlations for each of a plurality of fingerprints that serve as standards by finding cross-correlations by comparing inner product sequences of inputted fingerprint images registered in said inner product sequence temporary storage section with inner product sequence patterns of a plurality of fingerprints that serve as standards registered in said inner product sequence pattern dictionary while varying fingertip orientation by rotating the inner product sequence patterns of fingerprints serving as standards;

a sequence error temporary storage section that registers each cross-correlation found using said inner product sequence error calculation section and a corresponding fingertip orientation;

an orientation detection section that outputs a fingertip orientation corresponding to a cross-correlation having a maximum value among those registered in said sequence error temporary storage section; and

a control section that controls timing of each operation of said inner product sequence calculation section, inner product sequence error calculation section, and orientation detection section.

9. A fingerprint fingertip orientation detection method comprising the steps of:

finding ridge directions at prescribed positions around a circumference of an inputted fingerprint;

computing respective dot products of the ridge directions at the prescribed positions and a plurality of radial lines extending from a prescribed center point of the inputted fingerprint that intersect the respective prescribed positions;

obtaining a dot product sequence for a complete revolution with respect to the prescribed center point based on the respective dot products computed in the computing step; and

comparing the obtained dot product sequence with a plurality of stored dot product sequences of a standard fingerprint at different orientations,

wherein a particular one of the different orientations that corresponds to one of the stored dot product sequences that most closely matches the obtained dot product sequence is determined as the fingerprint orientation of the inputted fingerprint.

10. A fingerprint fingertip orientation detection method according to claim 9, wherein the plurality of radial lines respectively extend from a starting point a first fixed radial distance away from the prescribed center point to an ending point a second fixed radial distanced away from the prescribed center point.