BACKGROUND OF THE INVENTION 0001 1. Field of the Invention 0002 The present invention relates to a fingerprint authentication system and a fingerprint authentication method for personal authentication. 0003 2. Description of the Related Art 0004 Conventionally, a personal authentication function, represented by a password, has been used as a login function of a personal computer or for settlement in electronic commerce dealings. As this authentication function, various techniques have been known. The techniques include, for example, an authentication technique by inputting knowledge such as a password, as stated above, and a biometrics authentication technique using a biological feature. Although the authentication technique using personal knowledge such as the password is easy to operate, the technique has disadvantages in that the personal knowledge tends to be forgotten and stolen. In order that particularly high authentication accuracy is to be realized, the number of figures should be increases, thereby disadvantageously, considerably deteriorating user-friendliness. 0005 The biometrics authentication technique using a feature peculiar to each living body such as a fingerprint, a voiceprint, a face, or an iris, by contrast, has advantages in that the biological feature is difficult to lose and forget, and difficult for others to steal. The fingerprinting authentication system is the most promising authentication system among the conventional authentication systems from viewpoints of price, size, and authentication accuracy. 0006 According to the fingerprint authentication technique, a fingerprint is authenticated by detecting a pattern or a feature of fingerprint ridge parts (ridges). The fingerprint authentication system includes at least a fingerprint authentication module comprised of a fingerprint sensor section and an authentication section that authenticates whether a fingerprint detected by the fingerprint sensor section matches to one of registered fingerprints. The sensor includes microscopic sensor pixel cells arranged at a pitch of 50 to 100 microns and detect ridges and furrows of a fingerprint. Various methods are provided as a detection method for this fingerprint sensor. A capacitance method, an optical method, and the like are mainly known. According to the capacitance method, for example, an Si semiconductor element is employed as a substrate as shown in FIG. 3. Each cell detects a capacitance based on a distance and a contact area between a finger surface and the substrate, whereby the ridges and furrows of the finger are detected and a fingerprint pattern is detected. 0007 According to the conventional fingerprint authentication system, fingerprint registration is made first. In the registration processing, a finger is put on a fingerprint read section that serves as a fingerprint sensor, fingerprint data is detected, and the detected fingerprint data is registered in a fingerprint registration data section. In an authentication processing after the registration processing, the finger is put on the fingerprint sensor and the fingerprint data is detected similarly to the registration processing, followed by the transmission of the detected fingerprint data to a fingerprint collation section. The detected fingerprint data is compared and collated with all pieces of fingerprint data already registered in the fingerprint registration data section. If fingerprint data that matches to the detected fingerprint data is present, authentication results in a success. If there is no matching fingerprint data, authentication results in a failure. These fingerprint collation procedures are carried out under control of an operation control section, and an authentication result is displayed on a display section. 0008 Technical literatures relating to the present invention are as follows: 0009 Japanese Patent Application Laid-Open No. 09-171547 0010 Japanese Patent Application Laid-Open No. 09-198501 0011 Japanese Patent Application Laid-Open No. 09-297845 0012 Japanese Patent Application Laid-Open No. 11-312225 0013 Japanese Patent No. 2875053 0014 In recent years, cellular phones have rapidly spread and it is predicted that articles will be purchased and accounts of the articles are settled through the cellular phones in electronic commerce in the future. The cellular phones are used by users of all ages, as compared with personal computers. Conventionally, electronic commerce was intended for adults, fingerprint patters of whom have less change. In contrast, the cellular phones are used even by children. Since children are in a growth process, their fingerprint sizes increase. As a result, it is difficult to collate fingerprint data on each child with fingerprint data previously registered. Further, in an environment in which a finger is worked too hard, a fingerprint of the finger is damaged and a fingerprint surface changes with the passage of time. As a result, there is a case where the fingerprint collation cannot be performed.

SUMMARY OF THE INVENTION 0015 It is an object of the present invention to provide a fingerprint authentication system capable of preventing deterioration of authentication accuracy even for a child in a growth process or a person with a finger surface having dramatic change. 0016 According to a first aspect of the present invention, there is provided a fingerprint authentication system comprising: a fingerprint registration data section in which pieces of fingerprint data are registered; a fingerprint read section which reads one fingerprint data; a fingerprint collation section which inspects whether fingerprint data that matches or almost matches to the fingerprint data read by the fingerprint read section is registered in the fingerprint registration data section; and a control section which replaces the fingerprint data that is registered in the fingerprint registration data section and that matches or almost matches to the fingerprint data read by the fingerprint read section, with the fingerprint data read by the fingerprint read section if the fingerprint data that matches or almost matches to the fingerprint data read by the fingerprint read section is registered in the fingerprint registration data section. 0017 According to a second aspect of the present invention, there is provided a fingerprint authentication system comprising: a fingerprint registration data section in which pieces of fingerprint data are registered; a fingerprint read section which reads one fingerprint data; a fingerprint collation section which inspects whether fingerprint data that matches or almost matches to the fingerprint data read by the fingerprint read section is registered in the fingerprint registration data section; and a control section which registers the fingerprint data read by the fingerprint read section in the fingerprint registration data section additionally to the fingerprint data that is registered in the fingerprint registration data section and that matches or almost matches to the fingerprint data read by the fingerprint read section if the fingerprint data that matches or almost matches to the fingerprint data read by the fingerprint read section is registered in the fingerprint registration data section. 0018 The fingerprint authentication system according to the second aspect may further comprises: deletion means for deleting the fingerprint data having a general similarity that is highest among the pieces of fingerprint data registered in the fingerprint registration data section, from the fingerprint registration data section. 0019 The fingerprint authentication system according to the second aspect may further comprise: general similarity calculation means for calculating similarities between each of the pieces of fingerprint data registered in the fingerprint registration data section and the fingerprint data other than the each fingerprint data, respectively, and for calculating the general similarity based on the similarities. 0020 According to the present invention, whenever authentication succeeds, one of the fingerprint data registered in the fingerprint registration data section is replaced by the fingerprint data input by the fingerprint read section or the fingerprint data input by the fingerprint read section is added to the fingerprint data registered in the fingerprint registration data section. As a result, each time a user uses the system, the fingerprint data registered in the fingerprint registration data section changes. Therefore, it is possible to authenticate even fingerprint data on a child in a growth process without deteriorating authentication accuracy. 0021 In addition, the fingerprint data varies every season according to a roughness, a temperature, a hardness, and the like of a skin. However, by adding the fingerprint data input by the fingerprint read section to the data registered in the fingerprint registration data section as stated above, in order to accumulate fingerprint data on each season, it is possible to match registered fingerprint data during a season when the authentication is performed, to the authentication target fingerprint data, and to stably authenticate the fingerprint data without any influence of a seasonal change in the fingerprint. 0022 Furthermore, according to the conventional fingerprint authentication system, registered fingerprint data having a high similarity to the already registered fingerprint data is discovered so as to improve fingerprint collation performance. In contrast, according to the present invention, by deleting the fingerprint data having a high general similarity from the fingerprint registration data section, the fingerprint data having low general similarities are left in the fingerprint registration data section. This means that the fingerprint data having low mutual similarities are left in the fingerprint registration data section. Therefore, the fingerprint registration data section stores the fingerprint data various in patterns. Accordingly, the fingerprint of even the same person that changes in a various manner according to growth, seasons, and conditions can be detected with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS 0023 FIG. 1 is a flow chart which illustrates the principle of a fingerprint authentication system according to one embodiment of the present invention; 0024 FIG. 2 is an explanatory view for the configuration of the fingerprint authentication system according to the present invention; 0025 FIG. 3 is an explanatory view for the principle of a capacitance type fingerprint sensor; and 0026 FIG. 4 is a flow chart which illustrates the principle of a fingerprint authentication system according to another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 0027 Preferred embodiments of the present invention will be described hereinafter in detail with reference to the drawings. 0028 FIG. 2 is a system block diagram which illustrates the configuration of a fingerprint authentication system according to the present invention. FIG. 1 illustrates an authentication operation of the fingerprint authentication system. 0029 According to this system, fingerprint registration is made first. In the registration processing, fingerprint data is detected from a finger put on a fingerprint read section 10 that serves as a fingerprint sensor, and the detected fingerprint data is registered in a fingerprint registration data section 12. 0030 In an authentication processing after the registration processing, the fingerprint data is detected from the finger put on the fingerprint sensor similarly to the registration processing (in a step S101). The fingerprint data is transmitted to a fingerprint collation section 11. The fingerprint collation section 11 reads all pieces of fingerprint data already registered in the fingerprint registration data section 12 (in a step S102), and compares and collates these pieces of fingerprint data with the present fingerprint data detected by the fingerprint read section 10 (in a step S103). If fingerprint data that matches or almost matches, or is similar, to the present fingerprint data detected by the fingerprint read section 10 is already registered in the fingerprint registration data section 12, authentication results in a success (YES in a step S104). Here, almost match means that the general similarity, which will be described later, is the same as or more than a prescribed threshold. If such fingerprint data is not registered, the authentication results in a failure (NO in the step S104). These fingerprint collation procedures are controlled by an operation control section 13, and an authentication result is displayed on a display section 14. In case of the successful authentication, the fingerprint data registered in the fingerprint registration data section 12 and determined to match or almost match to the present fingerprint data is replaced by the present fingerprint data detected by the fingerprint read section 10, and the present fingerprint data is registered in the fingerprint registration data section 12. Alternatively, the present fingerprint data detected by the fingerprint read section 10 may be registered in the fingerprint registration data section 12 as additional fingerprint data (in the step S105). 0031 If data replacement is carried out, each registered fingerprint data and a registrant have a one-to-one correspondence in a database. If data addition is carried out, registered fingerprint data and a registrant have a many-to-one correspondence. Even in the latter case, similarly to the former case, the authentication target fingerprint data is compared and collated with all pieces of fingerprint data in the database, and the registrant corresponding to the fingerprint data closest to the authentication target fingerprint data among the fingerprint data in the database is determined as an authentication target person. 0032 If data addition is carried out, it is necessary to limit the number of registered fingerprint data to be equal to or less than a certain number. If such a limitation is not set, authentication time unavoidably, considerably increases and the registered fingerprint data exceed a storage capacity of the fingerprint registration data section 12. Therefore, if the number of registered fingerprint data reaches the certain number, it is important that a part of registered fingerprint data is to be deleted from the fingerprint registration data section 12. The second embodiment of the present invention will be described with reference to FIG. 4. In FIG. 4, steps S101 to S105 are the same as those described above with reference to FIG. 1. It is assumed herein that an upper limit of the number of registered fingerprint data is m. In a step S106, if authentication succeeds and the number of all the registered fingerprint data is equal to or smaller than m (YES in the step S106), the processing is finished. If the authentication succeeds and the number of all the registered fingerprint data exceeds m (actually, the number is (m1)) (NO in the step S106), a processing for deleting one out of all the registered fingerprint data is performed. In a step S107, a general similarity of each of all the registered fingerprint data is calculated. The general similarity will be described later. In a step S108, the registered fingerprint data having the highest general similarity is identified. In a step S109, the fingerprint data having the highest general similarity is deleted from all the registered fingerprint data, the number of registered fingerprint data is decreased to m, and the processing is finished. 0033 It is noted that the steps S107 to S109 are executed by the operation control section 13. 0034 The calculation of the general similarity will next be described. The calculation of the similarity between two pieces of registered fingerprint data among all (m1) pieces of registered fingerprint data is performed for all combinations of the selection of two pieces of data from among all the (m1) pieces of data. As a result of the calculation, m similarities are determined for each fingerprint data. The general similarity of each fingerprint data is calculated based on the m similarities. For example, the general similarity is set as a sum of the m similarities of each fingerprint data. Alternatively, the general similarity of each fingerprint data is set as a mean square of the m similarities thereof. Further, the general similarity may be calculated by applying various other calculation formulas to the m similarities. 0035 As described so far, according to the present invention, fingerprint detection can be utilized for personal authentication.