Fingerprint authentication system, fingerprint authentication method, and fingerprint authentication program

A fingerprint authentication method comprising:

• dividing a captured image of an authentication subject, via an image division unit, to be subjected to fingerprint authentication into a plurality of small regions;
• performing a frequency analysis, via a frequency analysis unit, on each of the small regions;
• extracting frequency components, via a ridge candidate extraction unit, corresponding to ridge candidates in the small regions from frequency components obtained in the frequency analysis;
• comparing the ridge candidates between adjacent small regions, via a continuous ridge candidate group generation unit, and when the ridge candidates satisfy a condition enabling the ridge candidates to be determined continuous, generating a continuous ridge candidate group including the ridge candidates;
• and
• determining that an abnormality exists in the image, via a determination unit, when overlap exists between the image regions corresponding to the continuous ridge candidate group;
• wherein one or more of the image division unit, the frequency analysis unit, the ridge candidate extraction unit, the continuous ridge candidate group generation unit, and the determination unit are implemented by a CPU.