Patent Publication Number: US-10789447-B2

Title: Fingerprint authentication method and electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 106141447, filed on Nov. 28, 2017. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a fingerprint authentication method and an electronic device. 
     Description of Related Art 
     As fingerprint recognition techniques gradually become prevalent, fingerprint recognition techniques are commonly used in electronic devices such as laptops and smartphones to authenticate an owner to manage access to the electronic devices. Generally, after a fingerprint authentication mechanism is activated, a user is required to store his or her own fingerprint information to the electronic device in a fingerprint enrollment procedure to be used later as the basis for performing fingerprint authentication. 
     However, as a sensing area of a fingerprint sensor is designed to be smaller and smaller, it becomes difficult for the user to enroll complete fingerprint information in the fingerprint enrollment procedure. Moreover, once exiting the fingerprint enrollment procedure, the user cannot modify and/or extend the enrolled fingerprint anymore. In other words, if the user intends to update his or her fingerprint information, the user can only re-start the fingerprint enrollment procedure. Accordingly, the current fingerprint authentication mechanism obviously lacks flexibility in use. 
     SUMMARY 
     The disclosure provides a fingerprint authentication method and an electronic device that, after a fingerprint enrollment operation is completed, update enrolled fingerprint information according to authenticated fingerprint information successfully passing a fingerprint authentication operation, thereby enhancing operation convenience in a fingerprint authentication mechanism. 
     An embodiment of the disclosure provides a fingerprint authentication method for an electronic device including a fingerprint sensor and a storage circuit, the fingerprint authentication method including: performing a fingerprint enrollment operation through the fingerprint sensor and storing enrolled fingerprint information to the storage circuit; sensing to-be-authenticated fingerprint information through the fingerprint sensor in a fingerprint authentication operation; and performing a default function corresponding to an authentication success of the fingerprint authentication operation and updating the enrolled fingerprint information according to authenticated fingerprint information if a similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to a default condition. 
     Another embodiment of the disclosure provides an electronic device including a fingerprint sensor, a storage circuit, and a processor. The processor is coupled to the fingerprint sensor and the storage circuit. The processor is configured to perform a fingerprint enrollment operation through the fingerprint sensor and store enrolled fingerprint information to the storage circuit. The processor is further configured to sense to-be-authenticated fingerprint information through the fingerprint sensor in a fingerprint authentication operation. The processor is further configured to perform a default function corresponding to an authentication success of the fingerprint authentication operation and update the enrolled fingerprint information according to authenticated fingerprint information if a similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to a default condition. 
     Accordingly, one fingerprint enrollment operation is performed through the fingerprint sensor, and the enrolled fingerprint information is stored to the storage circuit. Afterwards, in the fingerprint authentication operation, the to-be-authenticated fingerprint information is sensed through the fingerprint sensor. If the similarity between the sensed to-be-authenticated fingerprint information and the stored enrolled fingerprint information conforms to the default condition, a default function corresponding to the authentication success of the fingerprint authentication operation is performed, and the enrolled fingerprint information is updated according to the authenticated fingerprint information, thereby enhancing operation convenience in the fingerprint authentication mechanism. 
     To provide a further understanding of the aforementioned and other features and advantages of the disclosure, exemplary embodiments, together with the reference drawings, are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an electronic device according to an exemplary embodiment of the disclosure. 
         FIG. 2  is a schematic diagram illustrating an appearance of an electronic device according to an embodiment of the disclosure. 
         FIG. 3  is a schematic diagram illustrating swipe-type fingerprint sensing according to an embodiment of the disclosure. 
         FIG. 4  to  FIG. 6  are schematic diagrams illustrating a fingerprint image comparison according to an embodiment of the disclosure. 
         FIG. 7  is a schematic diagram illustrating updating enrolled fingerprint information according to an embodiment of the disclosure. 
         FIG. 8  is a flowchart illustrating a fingerprint authentication method according to an embodiment of the disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a schematic diagram illustrating an electronic device according to an exemplary embodiment of the disclosure. Referring to  FIG. 1 , an electronic device  10  includes a fingerprint sensor  11 , a storage circuit  12 , and a processor  13 . The fingerprint sensor  11  senses fingerprint information of a finger of a user. For example, the fingerprint sensor  11  may be a capacitive fingerprint sensor or an optical fingerprint sensor, but the disclosure does not limit the type of the fingerprint sensor  11 . A fingerprint sensing mechanism of the fingerprint sensor  11  is, for example, swipe sensing or press sensing. If the fingerprint sensing mechanism of the fingerprint sensor  11  is swipe sensing, the user swipes the finger on a sensing surface of the fingerprint sensor  11 , and the fingerprint sensor  11  senses the fingerprint information of the user through the sensing surface. Alternatively, if the fingerprint sensing mechanism of the fingerprint sensor  11  is press sensing, the user places the finger on the sensing surface of the fingerprint sensor  11 , and the fingerprint sensor  11  senses the fingerprint information of the user through the sensing surface. To facilitate illustration, the fingerprint sensor  11  using swipe sensing is described in the following embodiments as an example. 
     The storage circuit  12  is configured to store information. For example, the storage circuit  12  includes various non-volatile storage circuits, such as a conventional hard disk (HDD), a solid state disk (SSD), and/or a flash memory. Therefore, information stored in the non-volatile storage circuit is not lost due to a power disconnection of the electronic device  10 . For example, the storage circuit  12  stores information including enrolled fingerprint information and program codes required for operation of the electronic device  10 . Moreover, the storage circuit  12  may also include a volatile storage circuit such as a random access memory (RAM) to store temporary information generated during operation of the electronic device  10 . 
     The processor  13  is coupled to the fingerprint sensor  11  and the storage circuit  12 . The processor  13  is, for example, a central processing unit (CPU), a programmable microprocessor for general or specific purposes, a digital signal processor (DSP), a programmable controller, an application specific integrated circuit (ASIC), a programmable logic device (PLD), another similar device, or a combination of the devices above. 
     In an embodiment, the processor  13  is only responsible for operations related to a fingerprint authentication mechanism, such as fingerprint sensing, fingerprint enrollment, fingerprint authentication, etc. In an embodiment, the processor  13  is further responsible for overall operation or other operations of the electronic device  10 . In an embodiment, the electronic device  10  further includes an input/output (I/O) device and a power supply device. For example, the I/O device includes a mouse, a keyboard, a touch panel, a display, a touch screen, a microphone, a speaker, or a network interface card, and the type of the I/O device is not limited hereto. Moreover, the power supply device includes, for example, various power supply units or batteries. 
     In the description of the following embodiments, as an example, the electronic device  10  is a notebook computer. However, in another embodiment, the electronic device  10  may also be various electronic devices such as a smartphone, a tablet computer, a digital photo frame, a desktop computer, or an e-reader, and the disclosure is not limited hereto. 
       FIG. 2  is a schematic diagram illustrating an appearance of an electronic device according to an embodiment of the disclosure.  FIG. 3  is a schematic diagram illustrating swipe-type fingerprint sensing according to an embodiment of the disclosure. Referring to  FIG. 2  and  FIG. 3 , an electronic device  20  is provided with a fingerprint sensor  21  and a touch panel  22 . In the present embodiment, the fingerprint sensor  21  is disposed on the touch panel  22 . However, in another embodiment, the fingerprint sensor  21  may also be disposed at another surface position of the electronic device  20 , and the disclosure is not limited hereto. A sensing device  31  is disposed in a recess  32  of the fingerprint sensor  21 . A finger  301  of the user contacts an upper surface of the sensing device  31  and is swiped back and forth on the upper surface of the sensing device  31 . The sensing device  31  senses fingerprint information of the finger  301  that is being swiped. 
     Referring back to  FIG. 1 , the processor  13  performs a fingerprint enrollment operation and a fingerprint authentication operation. The fingerprint enrollment operation is configured to initially enroll fingerprint information of the user. For example, in the fingerprint enrollment operation, the processor  13  senses fingerprint information of a specific user through the fingerprint sensor  11  and matches the sensed fingerprint information with the specific user. Then, the processor  13  stores the sensed fingerprint information and relevant matching information to the storage circuit  12  to be used as enrolled fingerprint information. In an embodiment, the enrolled fingerprint information stored through the fingerprint enrollment operation is also referred to as initially enrolled fingerprint information. It is noted that, in the fingerprint enrollment operation, the processor  13  may also sense the fingerprint information of the specific user multiple times through the fingerprint sensor  11  and combine the sensed fingerprint information to generate the initially enrolled fingerprint information. After the fingerprint enrollment operation is completed, the enrolled fingerprint information may be used in the fingerprint authentication operation to authenticate an identity of a user currently operating the electronic device  10 . 
     In the fingerprint authentication operation, the processor  13  senses fingerprint information (also referred to as to-be-authenticated fingerprint information) through the fingerprint sensor  11 . The processor  13  compares the to-be-authenticated fingerprint information and the enrolled fingerprint information stored in the storage circuit  12  and determines whether a similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to a default condition. If the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to the default condition, the processor  13  determines that the sensed fingerprint information is successfully authenticated and performs a default function corresponding to an authentication success of the fingerprint authentication operation. In an embodiment, the successfully authenticated fingerprint information is also referred to as authenticated fingerprint information. However, if the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information does not conform to the default condition, the processor  13  determines that the sensed fingerprint information is not successfully authenticated and does not perform the default function. 
     In an embodiment, the default function includes, for example, various application functions that are allowed to be executed (only) after a successful identity authentication, such as logging in a specific application procedure, online purchase, device unlocking, etc. In other words, the fingerprint authentication operation may serve as an alternative means to conventional password authentication. In an embodiment, the fingerprint authentication operation may be used together with a password authentication operation. For example, if the fingerprint authentication mechanism and the password authentication mechanism are both activated, the user needs to simultaneously pass the fingerprint authentication operation and the password authentication operation before he or she can control the processor  13  to perform the default function. In another embodiment, the fingerprint authentication operation may also be used in combination with various other authentication mechanisms such as face authentication and/or iris authentication, and the disclosure is not limited hereto. 
     In an embodiment, the processor  13  performs a fingerprint image comparison according to the to-be-authenticated fingerprint information and the enrolled fingerprint information to determine whether the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to the default condition. For example, the processor  13  may compare the to-be-authenticated fingerprint information and the enrolled fingerprint information to obtain image overlap information. Then, the processor  13  may determine whether the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to the default condition according to the image overlap information. The image overlap information reflects a degree of match between the to-be-authenticated fingerprint information and the enrolled fingerprint information. If the degree of match between the to-be-authenticated fingerprint information and the enrolled fingerprint information reflected by the image overlap information is higher than a default degree, the processor  13  determines that the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to the default condition. Conversely, if the degree of match between the to-be-authenticated fingerprint information and the enrolled fingerprint information reflected by the image overlap information is not higher than the default degree, the processor  13  may determine that the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information does not conform to the default condition. 
       FIG. 4  to  FIG. 6  are schematic diagrams illustrating a fingerprint image comparison according to an embodiment of the disclosure. Referring to  FIG. 4  to  FIG. 6 , the processor  13  may convert the to-be-authenticated fingerprint information and the enrolled fingerprint information respectively into a to-be-authenticated fingerprint image  41  and an enrolled fingerprint image  51 . After the fingerprint image comparison is performed, the processor  13  may obtain an image overlap region  601  between the to-be-authenticated fingerprint image  41  and the enrolled fingerprint image  51 . In other words, the to-be-authenticated fingerprint information corresponds to the to-be-authenticated fingerprint image  41 , the enrolled fingerprint information corresponds to the enrolled fingerprint image  51 , and the image overlap information corresponds to the image overlap region  601  between the to-be-authenticated fingerprint image  41  and the enrolled fingerprint image  51 . 
     In an embodiment, the processor  13  compares the to-be-authenticated fingerprint image  41  and the enrolled fingerprint image  51 . According to a comparison result, the processor  13  sets at least two feature points respectively on the to-be-authenticated fingerprint image  41  and the enrolled fingerprint image  51 . Taking feature points  401 ,  402  on the to-be-authenticated fingerprint image  41  and feature points  501 ,  502  on the enrolled fingerprint image  51  as an example, after the to-be-authenticated fingerprint image  41  is rotated clockwise by 90 degrees, an image content in a coverage of the feature point  401  is substantially identical to an image content in a coverage of the feature point  501 , and an image content in a coverage of the feature point  402  is substantially identical to an image content in a coverage of the feature point  502 . By rotating, by a specific degree, at least one of the to-be-authenticated fingerprint image  41  and the enrolled fingerprint image  51  and performing an image comparison, the processor  13  can determine the feature points  401 ,  402 ,  501 , and  502 . 
     After the feature points  401 ,  402 ,  501 , and  502  are determined, the processor  13  causes the to-be-authenticated fingerprint image  41  and the enrolled fingerprint image  51  to at least partially overlap with each other according to the feature points  401 ,  402 ,  501 , and  502  to obtain the image overlap region  601 . For example, after the to-be-authenticated fingerprint image  41  is rotated clockwise by 90 degrees, the processor  13  positions the feature point  401  to the feature point  501  and positions the feature point  402  to the feature point  502  to thereby superimpose the to-be-authenticated fingerprint image  41  and the enrolled fingerprint image  51  to form a superimposed image  61 . The processor  13  may recognize the image overlap region  601  in the superimposed image  61 . In the image overlap region  601 , an image content of the to-be-authenticated fingerprint image  41  is substantially identical to an image content of the enrolled fingerprint image  51 . It is noted that being substantially identical as mentioned in the foregoing embodiment may mean being completely identical or being approximately identical considering errors caused by noise signals. In an embodiment, the processor  13  may also recognize the image overlap region  601  by using other image comparison techniques, and the disclosure is not limited hereto. 
     In an embodiment, the processor  13  determines whether an area of the image overlap region  601  is greater than a default area. If the area of the image overlap region  601  is greater than the default area, it means that the degree of match between the to-be-authenticated fingerprint information and the enrolled fingerprint information is higher than the default degree, and the processor  13  thus determines that the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to the default condition. Conversely, if the area of the image overlap region  601  is not greater than the default area, it means that the degree of match between the to-be-authenticated fingerprint information and the enrolled fingerprint information is not higher than the default degree, and the processor  13  thus determines that the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information does not conform to the default condition. 
     In an embodiment, the area of the image overlap region  601  is, for example, measured based on a number of pixels or a number of another unit of image. Moreover, although the image overlap region  601  is, as an example, a continuous region in the embodiment of  FIG. 6 , in another embodiment, the image overlap region  601  may also be discontinuous regions (for example, including a plurality of regions separate from each other). Alternatively, in another embodiment, the processor  13  may determine whether the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to the default condition according to factors related to the image overlap region  601 , e.g., whether a ratio of the area of the image overlap region  601  to a total area of the enrolled fingerprint image  51  is greater than a default ratio, and the disclosure is not limited hereto. 
     In an embodiment, if it is determined that the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to the default condition, the processor  13  further updates the enrolled fingerprint information according to the successfully authenticated fingerprint information (i.e., the authenticated fingerprint information). For example, the processor  13  may filter out a portion of the fingerprint information (also referred to as first portion fingerprint information) in the authenticated fingerprint information and combines the enrolled fingerprint information and another portion of the fingerprint information (also referred to as second portion fingerprint information) in the authenticated fingerprint information. 
     Taking  FIG. 6  as an example, after it is determined that the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to the default condition, the processor  13  filters out a fingerprint image in the authenticated fingerprint image  41  that corresponds to the image overlap region  601  (i.e., the fingerprint image in the authenticated fingerprint image  41  that is included in the image overlap region  601 ) and combines the enrolled fingerprint image  51  and the remaining fingerprint image in the authenticated fingerprint image  41  (i.e., the unfiltered fingerprint image in the authenticated fingerprint image  41 ) to form a fingerprint image similar to the superimposed image  61 . Moreover, in a combination operation of fingerprint images, the processor  13  may also perform operations including edge smoothing, image filling, etc., and the disclosure is not limited hereto. The fingerprint information (i.e., the updated enrolled fingerprint information) corresponding to the fingerprint image generated by the image combination above is stored to the storage circuit  12  to replace the enrolled fingerprint image  51  and is to be used in a next fingerprint authentication operation. 
       FIG. 7  is a schematic diagram illustrating updating enrolled fingerprint information according to an embodiment of the disclosure. Referring to  FIG. 7 , it is supposed that the enrolled fingerprint information corresponding to a fingerprint image  71  is enrolled and stored in the fingerprint enrollment operation. The fingerprint image  71  is also referred to as an initial fingerprint image. After a specific fingerprint authentication operation using the fingerprint image  71  is performed, the enrolled fingerprint information corresponding to the fingerprint image  71  is updated to enrolled fingerprint information corresponding to a fingerprint image  73 . An area of the fingerprint image  73  is greater than an area of the fingerprint image  71 . Compared to the fingerprint image  71 , the fingerprint image  73  further includes a fingerprint image  72 . For example, the fingerprint image  73  is obtained by combining the fingerprint image  71  and the fingerprint image  72 . The enrolled fingerprint information corresponding to the fingerprint image  73  may be used in a next fingerprint authentication operation. 
     After the next fingerprint authentication operation using the fingerprint image  73  is performed, the enrolled fingerprint information corresponding to the fingerprint image  73  is updated to enrolled fingerprint information corresponding to a fingerprint image  75 . An area of the fingerprint image  75  is greater than the area of the fingerprint image  73 . Compared to the fingerprint image  73 , the fingerprint image  75  further includes a fingerprint image  74 . For example, the fingerprint image  75  is obtained by combining the fingerprint image  73  and the fingerprint image  74 . The enrolled fingerprint information corresponding to the fingerprint image  75  may be used in a next fingerprint authentication operation. After the next fingerprint authentication operation using the fingerprint image  75  is performed, the enrolled fingerprint information corresponding to the fingerprint image  75  is updated to enrolled fingerprint information corresponding to a fingerprint image  77 . An area of the fingerprint image  77  is greater than the area of the fingerprint image  75 . Compared to the fingerprint image  75 , the fingerprint image  77  further includes a fingerprint image  76 . For example, the fingerprint image  77  is obtained by combining the fingerprint image  75  and the fingerprint image  76 . 
     In other words, after the fingerprint authentication operation is successfully completed at least once, it is not required to re-perform the fingerprint enrollment operation, and the fingerprint information reflecting fingerprint at different positions on the same finger of the same user can be gradually collected and combined into new enrolled fingerprint information to enhance efficiency in performing the fingerprint authentication afterwards. 
       FIG. 8  is a flowchart illustrating a fingerprint authentication method according to an embodiment of the disclosure. Referring to  FIG. 8 , in step S 801 , a fingerprint enrollment operation is performed through a fingerprint sensor and enrolled fingerprint information is stored to a storage circuit. In step S 802 , to-be-authenticated fingerprint information is sensed through the fingerprint sensor in a fingerprint authentication operation. In step S 803 , it is determined whether a similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to a default condition. If the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information does not conform to the default condition, in step S 804 , it is determined that authentication fails and a default function corresponding to an authentication success of the fingerprint authentication operation is not performed. However, if the similarity between the to-be-authenticated fingerprint information and the enrolled fingerprint information conforms to the default condition, in step S 805 , the default function corresponding to the authentication success of the fingerprint authentication operation is performed. In step S 806 , the enrolled fingerprint information is updated according to the authenticated fingerprint information. 
     The steps in  FIG. 8  have been detailed described above and will not be repeatedly described here. It is noted that the steps in  FIG. 8  may be implemented as a plurality of program codes or circuits, which is not limited in the disclosure. Moreover, the method of  FIG. 8  may operate with the foregoing exemplary embodiments or operate on its own, which is not limited in the disclosure. 
     In summary of the above, after the fingerprint enrollment operation is completed, the (initial) enrolled fingerprint information is stored. Afterwards, during the user&#39;s operation of the electronic device, it is not required to re-perform the fingerprint enrollment operation, and the enrolled fingerprint information can still be automatically updated in the background as the user performs the fingerprint authentication operation each time. Moreover, by setting the update operation of the enrolled fingerprint information to be performed along with the fingerprint authentication operation, the fingerprint area required to be detected in the fingerprint enrollment operation is also reduced, and/or the count of detection of the fingerprint information performed in the fingerprint enrollment operation is reduced, which thereby accelerates execution of the fingerprint enrollment operation. Particularly, in a fingerprint sensor having a smaller sensing surface, since the fingerprint of the user can hardly be completely inputted in a rapid manner in the fingerprint enrollment operation, the effects of shortening the time for performing the fingerprint enrollment operation and enhancing an authentication success rate in a later fingerprint authentication operation as achieved in the disclosure become even more outstanding. 
     Although the disclosure is disclosed as the embodiments above, the embodiments are not meant to limit the disclosure. Any person skilled in the art may make slight modifications and variations without departing from the spirit and scope of the disclosure. Therefore, the protection scope of the disclosure shall be defined by the claims attached below.