Fingerprint ID system and method

A fingerprint ID system which compares input fingerprint image data with registered image data, comprising:

• thinning processing means for thinning binary image data, said thinning processing means having thinning determination means which determines a deletable point in said binary image data by a table search in units of eight neighboring cells, and scan control means which reduces the number of times of scanning of said thinning determination means;
• minutia extracting means for extracting minutiae from said image data, said minutia extracting means having means for extracting minutia candidates from said thinned image data by a table search in units of eight neighboring cells, and pseudo minutia removing means for excluding pseudo minutiae from said minutia candidates;
• means for registering true minutiae of said image data, said image data including a plurality of quadrants;
• minutia matching means for matching minutiae of said input fingerprint image data with registered minutiae, said minutia matching means including:
• means for comparing the total number of branch points in said input fingerprint image data and the total number of branch points in said registered fingerprint image data;
• means for selecting a predetermined number of sub-branch points in increasing order of distance to a center point of said input fingerprint image data as master branch point candidates;
• means for determining if one said sub-branch point in each said quadrant in said input fingerprint image data lies in the vicinity of a corresponding sub-branch point in said registered fingerprint image data;
• means for determining if sub-sub-branch points in each said quadrant in said input fingerprint image data each lie in the vicinity of a corresponding one of sub-sub-branch points in said registered fingerprint image data;
• means for scoring a degree of mismatching between said sub-branch points in said input and registered fingerprint image data on the basis of a norm when said sub-branch point in said input fingerprint image data lies in the vicinity of said corresponding sub-branch point in said registered fingerprint image data;
• means for scoring the degree of mismatching between said sub-sub-branch points in said input and registered fingerprint image data on the basis of a norm when said sub-sub-branch points lie in the vicinities of said corresponding sub-sub-branch points in said registered fingerprint image data;
• means for computing a mean mismatching degree of said master branch point candidates;
• means for selecting, as a master branch point in said input fingerprint image data, that one of said master branch point candidates which has a minimum means mismatching degree;
• and
• means for judging an examinee to be a person of said registered fingerprint image data when the mean mismatching degree of said master branch point in said input fingerprint image data is smaller than a predetermined value;
• means for registering template data for template matching;
• and
• template matching means for template matching said input fingerprint image data with registered data.

A fingerprint ID method which compares input fingerprint image data with registered image data, comprising the steps of:

• processing binary image data for thinning, said thinning step including a thinning determination step which determines a deletable point in said binary image data by a table search in units of eight neighboring cells and a scan control step which reduces the number of times of scanning of said thinning determination step;
• extracting minutiae from said image data, said minutia extracting step including a step which extracts minutia candidates from said thinned image data by a table search in units of eight neighboring cells and a step which excludes pseudo minutiae from said minutia candidates;
• registering true minutiae of said image data;
• matching minutiae of said input fingerprint image data with registered minutiae;
• registering template data for template matching;
• template matching said input fingerprint image data with said registered data;
• comparing results of said minutia matching step and results of said template matching steps in terms of recognition rate;
• selecting the results of said minutia matching step for identifying said input fingerprint image data when the results of said minutia matching step have a higher recognition rate than the results of said template matching step;
• and
• selecting the results of said template matching step for identifying said input fingerprint image data when the results of said template matching step have a higher recognition rate than the results of said minutia matching step.

A fingerprint ID method which compares registered fingerprint data and input fingerprint data obtained by automatic contrast control by software, characterized by:

• first matching wherein a bulge-line direction pattern and a bulge-line curvature pattern of said registered fingerprint data are compared with those of said input fingerprint data and aligned with each other;
• the matching degree of said bulge-line direction and curvature patterns in overlapping areas thereof is computed;
• when said matching degree is above an upper threshold value, an examinee is judged to be the person of said registered fingerprint data;
• and when said matching degree is under a lower threshold value, said examinee is judged to be an outsider;
• and
• at least one second matching step wherein when said matching degree is above said lower threshold value and under said upper threshold value, only those areas of said input fingerprint data which match minutia high-density and medium-density areas of said registered fingerprint data are subjected to thinning to extract minutiae;
• the matching degree of said extracted minutiae is computed in terms of their position, kind and direction;
• when said matching degree in said high-density area is above said upper threshold value, said examinee is judged to be the person of said registered fingerprint data, and when said matching degree is under said lower threshold value, said examinee is judged to be an outsider, and when said matching degree is above said lower threshold value and under said upper threshold value, said examinee is judged to be an outsider;
• and when said matching degree in said medium-density area is above said upper threshold value, said examinee is judged to be the person of said registered fingerprint data, and when said matching degree is under said lower threshold value, said examinee is judged to be an outsider, and when said matching degree is above said lower threshold value and under said upper threshold value, said examinee is judged to be an outsider.