JP3574653B2 - Iris coding method, personal authentication method, iris code registration device, iris authentication device, and iris authentication program - Google Patents

Description

  The present invention relates to a technique for performing personal authentication using information on an iris, which is one of biometric information.

  Various personal authentication methods using biometric information such as iris, fingerprint, and face have been proposed. In recent years, the technology of personal authentication using iris recognition has begun to be used for entry / exit management to important facilities, ATM (Automated Teller Machine) of banks and the like, PC log-in applications, and the like.

  The personal authentication using the iris is performed, for example, by the following steps (see Patent Document 1).

1. The iris is illuminated using a near-infrared LED or the like to obtain an iris image. 2. Detect the boundary between the pupil iris and the boundary between the iris sclera (white eye) from the acquired image and extract the iris region. 3. Convert pixel coordinate values of the iris region from rectangular coordinates to polar coordinates. 4. Gabor transform the brightness of the iris area after the polar coordinate transformation. 5. Generate an iris code by binarizing the real part and the imaginary part of the Gabor transform output, respectively. 6. For the registrant, generate an iris code by the above steps 1 to 5 and register it in the registration database. For the certifier, an iris code is generated by the above steps 1 to 5, the iris code in the registration database is compared with the iris code, and the registrant is registered in the registration database due to a difference in the iris code. Judgment Whether or not to use the near-infrared light for illumination in 1 has the advantage that the person to be authenticated does not feel dazzling because the near-infrared light is not perceived by humans. In addition, most people on earth have a brownish iris (though some races have a blue or gray iris, but few in the world), the brownish iris is visible light This is because it is difficult to visually recognize the iris pattern underneath, but it is possible to photograph with near infrared light with rich contrast. In addition, blue and gray irises can be photographed under near-infrared light.
Japanese Patent Publication No. Hei 8-504979

  In recent years, mobile terminals such as mobile phones and PDAs have rapidly become widespread. In the future, the spread of authentication using these mobile terminals (mobile authentication) is expected. In the case of a mobile terminal, the mounted camera has a relatively low performance (low S / N) due to cost and size restrictions.

  When the S / N of the camera is low, in the above-described conventional method, there is a possibility that a difference occurs between the iris code at the time of registration and the iris code at the time of authentication due to bit inversion of the iris code due to video noise, fluctuation of the pupil diameter, and the like. high. If the difference is equal to or larger than a predetermined threshold, the person is not authenticated as a person, that is, so-called false rejection (FR) occurs. That is, there is a problem that the ratio of rejection of the person increases due to the low S / N of the camera.

  In view of the above problems, an object of the present invention is to reduce the occurrence of rejection of an individual in personal authentication using an iris image even when a camera having a low S / N is used.

  In order to solve the above-described problem, the present invention provides a method of determining the bit values of a plurality of iris codes obtained from a plurality of images by performing a rotation compensation on the iris codes and determining a bit value of each of the iris codes by a majority decision for each bit. It is integrated into one iris code. Thereby, the accuracy of each bit of the finally obtained iris code is increased, and the iris code can be stably obtained.

  In addition, the present invention cuts out the iris region from each of the plurality of images, performs polar coordinate conversion, band limitation, and rotation compensation, and then adds the plurality of images, accumulates the images as a single image, and stores the images. An iris code is generated. Thereby, even if the S / N of each original image is not sufficiently high, the noise components cancel each other when the images are accumulated, so that the S / N is improved and the S / N is high. A single image is obtained. Therefore, a stable iris code can be generated.

  In addition, the present invention provides a method of cutting out an iris region from each of a plurality of images, performing polar coordinate conversion and rotation compensation, adding the plurality of images, storing the added images as a single image, and performing band limiting on the stored images. To generate an iris code. Thereby, even if the S / N of each original image is not sufficiently high, the noise components cancel each other when the images are accumulated, so that the S / N is improved and the S / N is high. A single image is obtained. Therefore, a stable iris code can be generated.

  According to the present invention, the iris code can be generated stably without being affected by video noise or the like. Therefore, even if an image is shot with a camera having a low S / N, the occurrence of a false rejection (FR) can be prevented. It can be kept low. That is, stable personal authentication can be performed even with an inexpensive camera, and its practical effect is great.

  According to a first aspect of the present invention, as an iris encoding method, a step of inputting a plurality of images, a step of detecting an iris region from each of the plurality of images, and a method of defining a coordinate system for each detected iris region image. Converting the rectangular coordinate system to the polar coordinate system, performing a band limitation on each image after the coordinate transformation, generating an iris code from each image after the band limitation, and generating each iris code. Provided is a method comprising: compensating rotation in the circumferential direction; and integrating a plurality of iris codes after rotation compensation into a single iris code by determining bit values by majority decision for each bit.

  In a second aspect of the present invention, as an iris coding method, a step of inputting a plurality of images, a step of detecting an iris region from each of the plurality of images, and a method of forming a coordinate system on each of the detected images of the iris regions. Converting from a rectangular coordinate system to a polar coordinate system, performing a band limitation on each image after the coordinate conversion, compensating a rotation of each image after the band limitation in a circumferential direction, and each image after the rotation compensation And accumulating as a single image, and generating an iris code from the accumulated image.

  In a third aspect of the present invention, as an iris coding method, a step of inputting a plurality of images, a step of detecting an iris region from each of the plurality of images, and a method of forming a coordinate system on each of the detected images of the iris regions. Converting from the rectangular coordinate system to the polar coordinate system, compensating the rotation of each image after the coordinate transformation in the circumferential direction, adding the rotation-compensated images and accumulating them as a single image; Provided with a step of performing band limitation on the image and a step of generating an iris code from the image after band limitation.

  According to a fourth aspect of the present invention, there is provided the iris coding method according to any one of the first to third aspects, wherein the band limitation is performed by Gabor transform.

  In a fifth aspect of the present invention, as an individual authentication method using an iris image, an iris code is generated from the iris image at the time of registration, the generated iris code is registered in a database, and the iris image is registered at the time of authentication. Generating an iris code, comparing the generated iris code with the iris code registered in the database, and performing authentication at least one of registration and authentication. To an iris code generation method according to any one of the third to third aspects.

  In a sixth aspect of the present invention, as an iris code registration device, an image input unit, an iris region cutout unit that detects an iris region from an image input to the image input unit, and an iris obtained by the iris region cutout unit For an image of a region, a polar coordinate conversion unit that converts a coordinate system from a rectangular coordinate system to a polar coordinate system, a band limitation unit that performs band limitation on an image after coordinate conversion output from the polar coordinate conversion unit, and the band limitation unit. An iris code generator that generates an iris code from the band-limited image output from the iris code generator; a rotation compensator that circumferentially compensates the iris code output from the iris code generator; and a rotation compensator. A plurality of output iris codes after rotation compensation are received, and the plurality of iris codes are converted into a single iris code by determining a bit value by a majority decision for each bit. Provides a iris code integration unit that case, what the iris code output from the iris code integration unit and a iris code registration section that registers in the database.

  In a seventh aspect of the present invention, as an iris code registration device, an image input unit, an iris region cutout unit for detecting an iris region from an image input to the image input unit, and an iris obtained by the iris region cutout unit For an image of a region, a polar coordinate conversion unit that converts a coordinate system from a rectangular coordinate system to a polar coordinate system, a band limitation unit that performs band limitation on an image after coordinate conversion output from the polar coordinate conversion unit, and the band limitation unit. A rotation compensator for compensating for rotation in the circumferential direction of the band-limited image output from the controller; receiving a plurality of rotation-compensated images output from the rotation compensator; adding the plurality of images; An image storage unit that stores the image as an image, an iris code generation unit that generates an iris code from the image stored in the image storage unit, and a database that stores the iris code output from the iris code generation unit. Providing that a iris code registration section that registers the.

  According to an eighth aspect of the present invention, as an iris code registration device, an image input unit, an iris region cutout unit for detecting an iris region from an image input to the image input unit, and an iris obtained by the iris region cutout unit For the image of the region, a polar coordinate conversion unit that converts a coordinate system from a rectangular coordinate system to a polar coordinate system, a rotation compensation unit that circumferentially compensates for a coordinate-converted image output from the polar coordinate conversion unit, and a rotation compensation unit. An image storage unit that receives a plurality of rotation-compensated images output from the compensation unit, adds the plurality of images, and stores the added image as a single image, and performs band limiting on the images stored in the image storage unit. A band limiting unit, an iris code generating unit that generates an iris code from an image output from the band limiting unit, and registering the iris code output from the iris code generating unit in a database Providing that a chroma code registration section.

  In a ninth aspect of the present invention, as an iris authentication device, an image input unit, an iris region cutout unit that detects an iris region from an image input to the image input unit, and an iris region obtained by the iris region cutout unit For the image of, from a polar coordinate conversion unit that converts the coordinate system from a rectangular coordinate system to a polar coordinate system, a band limiting unit that performs band limiting on the image after the coordinate conversion output from the polar coordinate converting unit, and from the band limiting unit An iris code generator that generates an iris code from the output band-limited image, a rotation compensator that circumferentially compensates the iris code output from the iris code generator, and an output from the rotation compensator. Receiving the rotation-compensated iris codes, and integrating these iris codes into a single iris code by determining a bit value by a majority decision for each bit. Iris code integrating unit, compared with the iris codes registered iris code output to the database from the iris code integration unit, provides that a iris code authentication unit which performs authentication.

  According to a tenth aspect of the present invention, as an iris authentication device, an image input unit, an iris region cutout unit that detects an iris region from an image input to the image input unit, and an iris region obtained by the iris region cutout unit For the image of, from a polar coordinate conversion unit that converts the coordinate system from a rectangular coordinate system to a polar coordinate system, a band limiting unit that performs band limiting on the image after the coordinate conversion output from the polar coordinate converting unit, and from the band limiting unit A rotation compensator for rotationally compensating the output band-limited image in the circumferential direction; and a plurality of rotation-compensated images output from the rotation compensator, and adding the plurality of images to a single image. An iris code generation unit that generates an iris code from an image stored in the image storage unit; and an iris code output from the iris code generation unit in a database. Compared to the iris code being recorded, provides that a iris code authentication unit which performs authentication.

  In an eleventh aspect of the present invention, as an iris authentication device, an image input unit, an iris region cutout unit that detects an iris region from an image input to the image input unit, and an iris region obtained by the iris region cutout unit For the image, a polar coordinate conversion unit that converts the coordinate system from a rectangular coordinate system to a polar coordinate system, a rotation compensation unit that circumferentially compensates for the coordinate-converted image output from the polar coordinate transformation unit, and the rotation compensation An image storage unit that receives a plurality of rotation-compensated images output from the unit, adds the plurality of images, and stores the added image as a single image; and a band that performs band limiting on the images stored in the image storage unit. A limiting unit, an iris code generating unit that generates an iris code from the image output from the band limiting unit, and an iris code output from the iris code generating unit registered in a database. Compared with iris code, provides that a iris code authentication unit which performs authentication.

  In a twelfth aspect of the present invention, as an iris authentication program, an iris code generating step of generating an iris code for authentication by the iris coding method of any of the first to third aspects, and registering the iris code for authentication in a database And performing an authentication step of performing authentication by comparing the iris code with the iris code.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(1st Embodiment)
As the mobile terminal, for example, a mobile phone can be considered. Here, a case where a mobile phone with an authentication function is used will be described as an example.

  FIG. 1 is a flowchart showing a personal authentication method using iris recognition according to the first embodiment of the present invention. FIG. 2 is an overall view of the iris authentication system according to the present invention. In the present embodiment, the person to be authenticated performs iris authentication using a mobile phone with an authentication function as shown in FIG.

  In FIG. 2, the iris authentication server 211 has an iris database 212 that stores iris feature data of a plurality of persons, and is connected to a network 213 such as the Internet, a dedicated line, or a public line. The iris registration device 214 and the iris authentication device 215 are similarly connected to the network 213. The role of the iris authentication server 211 is to manage the iris database 212. The iris registration device 214 transmits the iris code generated at the time of registration to the iris database 212. The iris authentication device 215 performs personal authentication by comparing the iris code generated at the time of authentication with the iris code at the time of registration acquired from the iris database 212.

  Note that a plurality of iris authentication servers 211 may be provided for each region or institution used, or a plurality of iris authentication servers 211 including a mirror server for distributing a load. Further, the iris database 212 may be connected to the iris authentication server 211 via a network.

  In addition, the iris registration device 214 may perform only the photographing of the registration iris image, transmit the photographed iris image to the iris authentication server 211, and generate the iris code by the iris authentication server 211. Further, all functions of the iris registration device 214 may be built in the iris authentication server 211.

  Note that the iris authentication device 215 may perform only photographing of the iris image for authentication, transmit the photographed iris image to the iris authentication server 211, and generate the iris code by the iris authentication server 211. Further, the comparison with the registered iris code may be performed by the iris server 211, and the iris authentication device 215 may receive only the authentication result. In addition, the iris authentication device 215 itself has all the functions of FIG. 2, and registration, holding of iris data, and authentication may be performed by one device.

  The mobile phone with authentication function 10 shown in FIG. 3 has a camera 11 for capturing an iris image added to a normal mobile phone. The size (number of pixels) of an image captured by the camera 11 is CIF size (352 pixels × 288 pixels), QVGA size (320 pixels × 240 pixels), VGA size (640 pixels × 480 pixels), and SVGA size (800 pixels × 800 pixels). 600 pixels), XGA size (1024 pixels × 768 pixels), SXGA size (1240 pixels × 1024 pixels), UXGA size (1600 pixels × 1200 pixels), and the like. In addition to the camera 11, a monitor 13, an operation button 14, a speaker 15, a microphone 16, an antenna 17, and the like are provided. The monitor 13 displays an iris image being captured and an authentication result.

  In the internal configuration shown in FIG. 4, in the authentication unit 21, a camera control unit 22, a monitor control unit 24, and an authentication processing unit 26 are connected to a main control unit 27. The camera control unit 22 controls the camera 11 to capture an iris image, and the captured iris image is stored in the image memory 25. The authentication processing unit 26 performs an authentication process using the iris image stored in the image memory 25.

  Hereinafter, processing in the personal authentication method according to the present embodiment will be described with reference to the flow of FIG. FIG. 1 shows the flow of both the process in the registration unit (iris registration device) 214 and the process in the authentication unit (iris authentication device) 215. Here, the process in the authentication unit 215 will be described as an example. .

  First, as shown in FIG. 19, the person to be authenticated holds the mobile phone 10 with the authentication function shown in FIG. 3 and captures a plurality (N: N is an integer of 2 or more) of iris images (1b). At the time of photographing, the subject has the mobile phone 10 with the authentication function at a position at a predetermined distance from the eye (for example, about 20 cm before the camera 11 has a single focus), and the iris image captured by the camera 11 While confirming that is displayed on the monitor 13, the entire iris is included in the field of view, and the camera is positioned so that it is in focus. Then, the shooting button assigned to one of the operation buttons 14 is pressed. Press. This operation is repeated N times. Alternatively, the shooting start button may be pressed once to continuously acquire N frame images while shooting a moving image.

  Subsequent processes 2b to 7b are executed by the authentication processing unit 26. Here, it is basically assumed that the method disclosed in Patent Document 1 is used. The outline of the technique of Patent Document 1 is as follows.

(I) The iris region is cut out by determining the outer edge of the iris (boundary between the iris and the sclera) and the outer edge of the pupil (the boundary between the pupil and the iris). (II) The cut out iris region is xy orthogonal. Convert from coordinate system to rθ polar coordinate system (III) Determine analysis area (radial direction is divided into 8 rings)
(IV) Applying multi-scale 2-d Gabor transform and binarizing the Gabor-converted signal to obtain an iris code. (V) Registered iris code registered in advance and iris code at the time of authentication. (Exclusive OR) and calculate the Hamming distance between the two codes. (VI) If the Hamming distance is less than or equal to the threshold value, accept as the principal, otherwise reject as another person. FIG. 6 is a diagram showing the positions of the outer edge of the iris and the outer edge of the pupil, and FIG. 6 is a diagram in which an area surrounded by the outer edge of the iris and the outer edge of the pupil is cut out as an iris area and expressed in an xy coordinate system. At this point, the effects of the translation of the iris region are absorbed. FIG. 7 is a diagram expressing the iris region in the rθ polar coordinate system with the center of the pupil as the center (conversion of (II)). By setting the value in the r direction to 0 at the outer edge of the pupil and 1 at the outer edge of the iris, it is possible to absorb the effect of the difference in the degree of opening of the pupil and the effect of scaling.

  FIG. 8 is a diagram illustrating the 8-ring analysis region determined in (III), and FIG. 9 is a diagram illustrating the creation of the iris code in (IV). The luminance signal (a) after the analysis region in FIG. 2) shows a state in which Gabor transform is applied (b) and binarization is performed (c). Although the signal is actually a two-dimensional signal, it is shown here as one-dimensional for simplification of description. (A) is an angular direction luminance signal in one of the eight rings. Actually, a multi-scale Gabor transform is applied, and a Gabor transform output of a single scale has a real part and an imaginary part, but in (b) and (c), the real part of a Gabor transform output of a certain scale is applied. This is the result. The position of each bit in the binarized iris code (c) can be associated with a certain position on the iris image.

  In the present embodiment, the following processing is performed based on the iris authentication processing in Patent Document 1.

  First, N iris images are photographed (1b), iris regions are respectively cut out from the photographed images (2b), and the coordinate system is converted from a rectangular coordinate system to a polar coordinate system for each detected iris region image. After (3b), the feature is extracted by limiting the band by, for example, Gabor conversion (4b). Then, N iris codes (for example, 2048 bits) as iris data, which are feature amounts for authentication, are generated from each image after the band limitation (5b). The processing up to this point may be performed in the same manner as the above-described processing (I) to (IV), whereby, from a plurality of iris images, translation, enlargement / reduction, difference in pupil opening degree, influence of pupil eccentricity Are generated respectively.

  Next, as preprocessing for integrating a plurality of iris codes, rotation compensation between iris codes is performed (6b). That is, since there is a possibility that there is a deviation in the angular direction due to the inclination of the face or the rotation of the eyeball itself among the generated N iris codes, this deviation is compensated. As shown in FIG. 10, one of the N iris codes (for example, the first generated iris code) is used as a reference iris code, and the other iris codes are rotated to a predetermined range to perform matching. The shift amount is determined so that the Hamming distance is minimized, and rotation compensation is performed. FIG. 10 illustrates an iris code in one of the eight rings of the iris region for simplification of the description.

  The human pupil contracts due to changes in the surrounding environment such as brightness, physical condition, emotions, and the like. Therefore, simply adding a plurality of images cannot reduce the influence of video noise on the iris pattern. . For this reason, the above-described processes 2b to 6b realize alignment that absorbs the influence of enlargement / reduction.

  Next, a plurality of iris codes after rotation compensation are synthesized and integrated into a single iris code (7b). Thereby, a final authentication iris code is generated. As shown in FIG. 11, the integration of the iris codes is realized by taking a majority decision as to whether the value of each bit of the N iris codes after the rotation compensation is “0” or “1”. That is, each bit value of the integrated iris code is determined by majority decision for each bit. In the example of FIG. 11, since the bit value of the last bit of each iris code is more “1” than “0”, the bit value of the last bit of the integrated iris code is determined to be “1”. I have.

  Returning to FIG. 1, the iris code integrated in the process 7b is compared with the iris code registered in the iris database 212 in advance, and authentication is performed using the collation score (Humming distance: HD value) (9). If the hamming distance is equal to or less than a predetermined threshold value TH1, the user is accepted as a person, otherwise, the person is rejected as another person. Then, the final authentication result is displayed on the monitor 13 of the mobile phone with authentication function 10 in FIG.

  The processing in the registration unit 214 is almost the same as that described here, and the registration iris code is generated from a plurality of images by the same processing 1a to 7a as the processing 1b to 7b in the authentication unit 215. . Then, the generated registration iris code is registered in the iris database 212 (8).

  As described above, according to the present embodiment, a plurality of iris codes obtained from a plurality of iris images are integrated into a single iris code by performing a majority decision for each bit after positioning in the rotation direction. As a result, an iris code can be obtained stably, and therefore, even when an image captured by a low S / N camera is used, iris authentication can be performed with reduced rejection (FR).

  It should be noted that the majority operation for each bit performed at the time of iris code integration is not limited to the simple majority operation described in the present embodiment, and various methods can be considered. For example, a weight may be determined for each iris code to be integrated, and a majority operation may be performed including the weight. For example, the weight may be determined for each iris code based on the minimum HD value when compared with the registered iris code, based on the relationship shown in FIG. By the weighting as shown in FIG. 12, the information of the iris code that gives a small HD value is used with higher priority in integrating the iris codes.

  In the present embodiment, at the time of authentication, all of the processes 2b to 7b and 9 are performed on the terminal side. However, only the process 1b for capturing a plurality of images is performed on the terminal side, and the captured plurality of images are transmitted via the network. May be transmitted to the server, and the processes 2b to 7b and 9 may be performed on the server. In this case, the authentication result is calculated on the server, the calculation result is transmitted again to the terminal via the network, and the authentication result is displayed on the monitor 13 of the terminal. Similarly, at the time of registration, processing 1a for photographing a plurality of images is performed on the terminal side, the photographed images are transmitted to a server via a network, and processing 2a to 7a and 8 are performed on the server. Good.

  FIG. 20 is a block diagram illustrating an example of a device configuration according to the present embodiment, in which (a) is an iris code registration device, and (b) is an iris authentication device. An iris code registration device 30 illustrated in FIG. 20A includes an image input unit 31, an iris code generation unit 32 that generates an iris code from a plurality of images input to the image input unit 31, and an iris code generation unit 32. An iris code registration unit 33 for registering the generated iris code in the iris database 212; 20B includes an image input unit 41, an iris code generation unit 42 that generates an iris code from a plurality of images input to the image input unit 41, and an iris code generation unit 42. An iris code authentication unit 43 for comparing the iris code generated by the iris code with the iris code registered in the iris database 212 and performing authentication is provided. The iris code generators 32 and 42 generate iris codes by the method described in the present embodiment. The iris code generators 32 and 42 generate iris codes from the images input to the image input units 31 and 41, respectively. 44, the iris region images obtained by the iris region cutout units 34 and 44, the polar coordinate conversion units 35 and 45 for converting the coordinate system from the rectangular coordinate system to the polar coordinate system, and the polar coordinate conversion units 35 and 45 Band limiting units 36 and 46 for performing band limiting on the image after the coordinate transformation, iris code generating units 37 and 47 for generating iris codes from the band-limited images output from the band limiting units 36 and 46, Rotation compensators 38 and 48 for rotationally compensating the iris code output from iris code generators 37 and 47 in the circumferential direction, and rotation compensation output from rotation compensators 38 and 48. Receiving a plurality of iris codes after, the plurality of iris codes, by determining the bit value by majority for each bit, and a iris code integration unit 39, 49 be integrated into a single iris code. Then, the iris codes output from the iris code integration units 39 and 49 are provided to the iris code registration unit 33 or the iris code authentication unit 43.

(Second embodiment)
FIG. 13 is a flowchart showing a personal authentication method using iris recognition according to the second embodiment of the present invention. In FIG. 13, the same reference numerals as in FIG. 1 denote the same processes as in FIG. 1, and a description thereof will not be repeated. In the present embodiment, for each image subjected to Gabor transform (4a, 4b) as band limiting processing, after rotation compensation (108a, 108b), addition and accumulation (109a, 109b), iris code generation (110a, 109b) 110b) is different from the first embodiment.

  As shown in FIG. 14, the rotation compensation for the Gabor conversion output is performed by changing the amount of shift in the angular direction such that the residual (sum of residual squares or absolute sum of residuals) with the reference Gabor converted output is minimized. Do it by deciding. In FIG. 14, for the sake of simplicity, the real part when one of the eight rings of the iris region is subjected to Gabor transformation at a certain scale is shown.

  Then, as shown in FIG. 15, the Gabor conversion outputs after the rotation compensation for a plurality of (N) images are added and accumulated (accumulated) as a single image. Then, an iris code is generated from the stored image.

  As described above, according to the present embodiment, an iris image cut out from each of a plurality of images is subjected to polar coordinate conversion, band limitation, and rotation compensation, and then stored as a single image. Generate As a result, even when the S / N of each original image is not sufficiently high, a high S / N can be obtained because noise components cancel each other out in a single stored image. Therefore, an iris code can be obtained stably, and iris authentication can be performed with reduced rejection (FR).

  Note that, as in the first embodiment, at the time of authentication, only the process 1b of photographing a plurality of images is performed on the terminal side, the photographed images are transmitted to the server via the network, and the processes 2b to 4b are performed on the server. , 108b to 110b, 9 may be performed. Similarly, at the time of registration, the terminal performs processing 1a for capturing a plurality of images, transmits the captured images to a server via a network, and performs processing 2a to 4a, 108a to 110a, and 8 on the server. You may do so.

  FIGS. 21A and 21B are block diagrams illustrating an example of the device configuration according to the present embodiment. FIG. 21A illustrates an iris code registration device, and FIG. 21B illustrates an iris authentication device. 21, the same components as those in FIG. 20 are denoted by the same reference numerals as in FIG.

  An iris code registration device 30A illustrated in FIG. 21A includes an image input unit 31, an iris code generation unit 32A that generates an iris code from a plurality of images input to the image input unit 31, and an iris code generation unit 32A. An iris code registration unit 33 for registering the generated iris code in the iris database 212; 20B includes an image input unit 41, an iris code generation unit 42A that generates an iris code from a plurality of images input to the image input unit 41, and an iris code generation unit 42A. An iris code authentication unit 43 for comparing the iris code generated by the iris code with the iris code registered in the iris database 212 and performing authentication is provided. The iris code generating means 32A, 42A generates an iris code by the method described in the present embodiment, and the iris area cutout section 34, which detects the iris area from the images input to the image input sections 31, 41, 44, the iris region images obtained by the iris region cutout units 34 and 44, the polar coordinate conversion units 35 and 45 for converting the coordinate system from the rectangular coordinate system to the polar coordinate system, and the polar coordinate conversion units 35 and 45 Band limiting units 36 and 46 for performing band limiting on the image after the coordinate transformation, and rotation compensating units 51 and 54 for circumferentially rotating the image after the band limiting output from the band limiting units 36 and 46. An image storage unit 52, 55 for receiving a plurality of rotation-compensated images output from the rotation compensation units 51, 54, adding the plurality of images, and storing the added image as a single image; And a iris code generation unit 53 and 56 for generating an iris code from the stored image to the product portion 52 and 55. Then, the iris codes output from the iris code integration units 53 and 56 are provided to the iris code registration unit 33 or the iris code authentication unit 43.

(Third embodiment)
FIG. 16 is a flowchart showing a personal authentication method using iris recognition according to the third embodiment of the present invention. In FIG. 16, the same processes as those in FIG. 1 or FIG. 13 are denoted by the same reference numerals as those in FIG. 1 or FIG. 13, and description thereof is omitted here. In the present embodiment, each image subjected to the polar coordinate transformation (3a, 3b) is subjected to rotation compensation (111a, 111b), added and accumulated (112a, 112b), and Gabor transformed as a band limiting process (113a). , 113b) and iris code generation (110a, 110b) are different from the first and second embodiments.

  As shown in FIG. 17, the rotation compensation for the image after the polar coordinate conversion is such that the residual (sum of the residual squares or the absolute value of the residual) from the reference iris region image (the one after the coordinate conversion to the polar coordinate system) is minimized. This is performed by determining the amount of shift in the angular direction such that

  Then, as shown in FIG. 18, a plurality of (N) images after the rotation compensation are sequentially added and accumulated as a single image. By accumulating images in this way, random noise components in each image cancel each other, and the S / N of the image is improved. Then, Gabor conversion is performed on the stored image, and an iris code is generated from the image after Gabor conversion.

  As described above, according to the present embodiment, an iris image cut out from each of a plurality of images is subjected to polar coordinate conversion and rotation compensation, and then stored as a single image. Generate This makes it possible to generate an iris code from an image in which noise components cancel each other out and the S / N is improved. Therefore, an iris code can be obtained stably, and iris authentication can be performed with reduced rejection (FR).

  Note that, as in the first or second embodiment, at the time of authentication, only the process 1b of photographing a plurality of images is performed on the terminal side, the photographed images are transmitted to the server via the network, and the process is performed on the server. 2b, 3b, 111b to 113b, 110b, 9 may be performed. Similarly, at the time of registration, the terminal performs processing 1a for photographing a plurality of images, transmits the photographed images to a server via a network, and performs processing 2a, 3a, 111a to 113a, 110a, and 8 on the server. May be performed.

  FIG. 22 is a block diagram illustrating an example of a device configuration according to the present embodiment. FIG. 22A illustrates an iris code registration device, and FIG. 22B illustrates an iris authentication device. In FIG. 22, the same reference numerals as in FIG. 20 denote the same components as in FIG.

  An iris code registration device 30B illustrated in FIG. 22A includes an image input unit 31, an iris code generation unit 32B that generates an iris code from a plurality of images input to the image input unit 31, and an iris code generation unit 32B. An iris code registration unit 33 for registering the generated iris code in the iris database 212; An iris authentication device 40B shown in FIG. 22B includes an image input unit 41, an iris code generation unit 42B that generates an iris code from a plurality of images input to the image input unit 41, and an iris code generation unit 42B. An iris code authentication unit 43 for comparing the iris code generated by the iris code with the iris code registered in the iris database 212 and performing authentication is provided. The iris code generation means 32B and 42B generate an iris code by the method described in the present embodiment. 44, the iris region images obtained by the iris region cutout units 34 and 44, the polar coordinate conversion units 35 and 45 for converting the coordinate system from the rectangular coordinate system to the polar coordinate system, and the polar coordinate conversion units 35 and 45 Rotation compensators 61 and 65 for compensating the rotation of the image after the coordinate transformation in the circumferential direction, and a plurality of rotation-compensated images output from the rotation compensators 61 and 65 are received. Image storage units 62 and 66 for storing images as image data, band restriction units 63 and 67 for performing band restriction on the images stored in the image storage units 62 and 66, and band restriction units 63 and 66. And a iris code generation unit 64, 68 for generating an iris code from the image output from the 7. Then, the iris codes output from the iris code integration units 64 and 68 are provided to the iris code registration unit 33 or the iris code authentication unit 43.

  With respect to the above-described second and third embodiments, a supplementary explanation will be given on the relationship between the number of images and the authentication accuracy.

  When registration and authentication are performed using a single registered image and a single authentication image, the relationship between the S / N of the camera and the FRR is as shown in FIG. That is, as shown in FIG. 23, when the S / N of the camera is low, the FRR increases, and when the S / N of the camera is high, the FRR decreases. The relationship between the S / N of the camera and the FRR is determined by the strength of the iris pattern in each iris image and the resolution of the iris image.

When the S / N (S / N ₀ in the figure) of the camera to be used is determined from the relationship shown in FIG. 23, the FRR (R / R) for performing registration and authentication using a single registered image and a single authentication image FRR ₀ ) in the figure is also determined. On the other hand, a case where registration and authentication are performed using a registration code generated from a plurality of images and an authentication code generated from the plurality of images will be described below.

に対して、ｎ枚の画像を加算蓄積した場合のＳ／Ｎは、

となり、Ｓ／Ｎが１０ｌｏｇｎだけ向上する。 When n images having the same noise level (the image after the band limitation or the image after the polar coordinate conversion in the second and third embodiments) are added and accumulated, the signal level becomes n times, while the noise level becomes √. n times and S / N is improved. That is, S / N for a single image

In contrast, the S / N when adding and accumulating n images is

And the S / N is improved by 10 logn.

In FIG. 23, from the difference (ΔS / N) between the target S / N (S / N ₁ ) corresponding to the target FRR (FRR ₁ ) and the S / N (S / N ₀ ) of the camera to be used, The number n of input images can be determined. FIG. 24 shows the relationship between the number n of input images and the S / N improvement amount ΔS / N. FIG. 24 shows that when the number of input images is set to, for example, 2, 4, 8, 16, or 32, the S / N is improved by about 3 dB, 6 dB, 9 dB, 12 dB, and 15 dB, respectively.

  In each of the above embodiments, an example has been described in which an iris code is generated using the same method at the time of registration and at the time of authentication. However, the method of generating an iris code is always the same at the time of registration and at the time of authentication. No need. For example, at the time of registration, an iris code is generated from a single iris image using a high-performance (high S / N) camera by the method of Patent Document 1, and at the time of authentication, any one of the methods according to the embodiments of the present invention is used. May be used to generate an iris code. In addition, when using any of the methods of the embodiments of the present invention both at the time of registration and at the time of authentication, different methods may be used.

  In each of the above-described embodiments, the band limitation for feature extraction is performed by Gabor transform. However, the method of feature extraction is not limited to this. For example, a band using another band-pass filter may be used. It may be performed by restriction.

  In each of the above embodiments, the case where the mobile phone with the authentication function is used has been described as an example. However, the effect of the present invention is not limited to the mobile phone with the authentication function, but can be similarly obtained in other authentication devices. It is clear and included in the present invention.

  Note that the processing described in each of the above embodiments can be implemented in whole or in part by causing a computer to execute a program. For example, the iris authentication device includes a computer and a memory for storing an iris authentication program. This iris authentication program compares the iris code for authentication with an iris code registered in a database, and an iris code generation step of generating an iris code for authentication by the iris coding method described in each of the above embodiments. The authentication step of performing the authentication may be performed by a computer.

  The iris coding method according to the present invention is less susceptible to video noise and fluctuations of the pupil diameter, and can stably generate an iris code. For example, there is a high possibility that a camera having a low S / N ratio will be mounted. It is useful in applications such as personal authentication using a mobile terminal.

4 is a flowchart illustrating an iris authentication method according to the first embodiment of the present invention. 1 is an overall view of an iris authentication system according to the present invention. 1 is an external view of a mobile phone with an authentication function according to each embodiment of the present invention. FIG. 4 is a diagram schematically illustrating an internal configuration of the mobile phone in FIG. 3. It is a figure which shows a pupil outer edge and an iris outer edge. FIG. 3 is a diagram representing an iris image in an xy orthogonal coordinate system. FIG. 3 is a diagram expressing an iris image in an rθ polar coordinate system. FIG. 7 is a diagram illustrating an analysis band obtained by dividing an iris into eight rings. FIG. 4 is a diagram illustrating a method for generating an iris code. FIG. 4 is a diagram illustrating a method for rotationally compensating an iris code. It is a figure showing the method of integrating each bit of an iris code by majority decision. It is a figure which shows the distribution of the weight used for the integration by the weighted majority decision of the iris code. 6 is a flowchart illustrating an iris authentication method according to a second embodiment of the present invention. FIG. 6 is a diagram illustrating a method of performing rotation compensation on a Gabor conversion output. FIG. 7 is a diagram illustrating accumulation of Gabor conversion output after rotation compensation. 9 is a flowchart illustrating an iris authentication method according to a third embodiment of the present invention. FIG. 4 is a diagram illustrating a method of rotationally compensating an iris image subjected to polar coordinate conversion. FIG. 9 is a diagram illustrating accumulation of an iris image after rotation compensation. FIG. 3 is a diagram illustrating a state of use of a mobile phone with an authentication function. FIG. 1 is a block diagram illustrating a device configuration according to a first embodiment of the present invention. It is a block diagram showing a device configuration according to a second embodiment of the present invention. FIG. 13 is a block diagram illustrating a device configuration according to a third embodiment of the present invention. 4 is a graph showing a relationship between S / N of a camera and FRR. 13 is a graph showing the relationship between the number n of input images and the improvement amount ΔS / N of S / N in the second and third embodiments of the present invention.

Explanation of reference numerals

10 Mobile Phone with Authentication Function 30, 30A, 30B Iris Code Registration Device 31, 41 Image Input Unit 33 Iris Code Registration Unit 34, 44 Iris Area Cutout Unit 35, 45 Polar Coordinate Transformation Unit 36, 46, 63, 66 Band Limiting Unit 37 , 47, 53, 64 iris code generation units 38, 48, 51, 54, 61, 65 rotation compensation units 39, 49 iris code integration units 40, 40A, 40B iris authentication device 43 iris code authentication units 52, 55, 62, 66 Image storage unit 211 Iris authentication server 212 Iris database 213 Network 214 Iris registration device 215 Iris authentication device

Claims (12)

Inputting a plurality of images;
Detecting an iris region from each of the plurality of images;
For the image of each detected iris region, converting the coordinate system from a rectangular coordinate system to a polar coordinate system;
Performing a band limitation on each image after the coordinate transformation;
Generating an iris code from each band-limited image,
Compensating the rotation of each generated iris code in the circumferential direction;
Integrating the plurality of rotation-compensated iris codes into a single iris code by determining a bit value by a majority decision on a bit-by-bit basis. Inputting a plurality of images;
Detecting an iris region from each of the plurality of images;
For the image of each detected iris region, converting the coordinate system from a rectangular coordinate system to a polar coordinate system;
Performing a band limitation on each image after the coordinate transformation;
A step of compensating the rotation of each image after the band limitation in the circumferential direction;
Adding each image after rotation compensation and accumulating as a single image;
Generating an iris code from the stored image. Inputting a plurality of images;
Detecting an iris region from each of the plurality of images;
For the image of each detected iris region, converting the coordinate system from a rectangular coordinate system to a polar coordinate system;
A step of compensating rotation of each image after the coordinate transformation in the circumferential direction;
Adding each image after rotation compensation and accumulating as a single image;
Performing band limiting on the stored images;
Generating an iris code from the band-limited image. In any one of claims 1 to 3,
An iris coding method, wherein the band limitation is performed by Gabor transform. A personal authentication method using an iris image,
At the time of registration,
Generate an iris code from the iris image,
Register the generated iris code in the database,
At the time of authentication,
Generate an iris code from the iris image,
The generated iris code is compared with the iris code registered in the database to perform authentication,
An individual authentication method, wherein an iris code is generated by at least one of registration and authentication by the iris code generation method according to any one of claims 1 to 3. An image input unit;
From the image input to the image input unit, an iris region cutout unit that detects an iris region,
For an image of an iris region obtained by the iris region cutout unit, a polar coordinate conversion unit that converts a coordinate system from a rectangular coordinate system to a polar coordinate system,
For the image after the coordinate transformation output from the polar coordinate transformation unit, a band limiting unit that performs band limitation,
An iris code generator that generates an iris code from the band-limited image output from the band limiter;
A rotation compensation unit that compensates for rotation in the circumferential direction of the iris code output from the iris code generation unit,
An iris code integration unit that receives a plurality of rotation-compensated iris codes output from the rotation compensation unit and integrates the plurality of iris codes into a single iris code by determining a bit value by a majority decision for each bit. Department and
An iris code registration device, comprising: an iris code registration unit that registers an iris code output from the iris code integration unit in a database. An image input unit;
From the image input to the image input unit, an iris region cutout unit that detects an iris region,
For an image of an iris region obtained by the iris region cutout unit, a polar coordinate conversion unit that converts a coordinate system from a rectangular coordinate system to a polar coordinate system,
For the image after the coordinate transformation output from the polar coordinate transformation unit, a band limiting unit that performs band limitation,
A rotation compensating unit that compensates for rotation in the circumferential direction of the band-limited image output from the band limiting unit,
An image storage unit that receives a plurality of rotation-compensated images output from the rotation compensation unit, adds the plurality of images, and accumulates the images as a single image;
An iris code generation unit that generates an iris code from an image stored in the image storage unit;
An iris code registration device, comprising: an iris code registration unit that registers an iris code output from the iris code generation unit in a database. An image input unit;
From the image input to the image input unit, an iris region cutout unit that detects an iris region,
For an image of an iris region obtained by the iris region cutout unit, a polar coordinate conversion unit that converts a coordinate system from a rectangular coordinate system to a polar coordinate system,
A rotation compensation unit that compensates for rotation in the circumferential direction of the image after the coordinate transformation output from the polar coordinate transformation unit,
An image storage unit that receives a plurality of rotation-compensated images output from the rotation compensation unit, adds the plurality of images, and accumulates the images as a single image;
A band limiting unit that performs band limiting on the image stored in the image storage unit,
An iris code generation unit that generates an iris code from an image output from the band limiting unit;
An iris code registration device, comprising: an iris code registration unit that registers an iris code output from the iris code generation unit in a database. An image input unit;
From the image input to the image input unit, an iris region cutout unit that detects an iris region,
For an image of an iris region obtained by the iris region cutout unit, a polar coordinate conversion unit that converts a coordinate system from a rectangular coordinate system to a polar coordinate system,
For the image after the coordinate transformation output from the polar coordinate transformation unit, a band limiting unit that performs band limitation,
An iris code generator that generates an iris code from the band-limited image output from the band limiter;
A rotation compensation unit that compensates for rotation in the circumferential direction of the iris code output from the iris code generation unit,
An iris code integration unit that receives a plurality of rotation-compensated iris codes output from the rotation compensation unit and integrates the plurality of iris codes into a single iris code by determining a bit value by a majority decision for each bit. Department and
An iris authentication device, comprising: an iris code authentication unit that compares an iris code output from the iris code integration unit with an iris code registered in a database and performs authentication. An image input unit;
From the image input to the image input unit, an iris region cutout unit that detects an iris region,
For an image of an iris region obtained by the iris region cutout unit, a polar coordinate conversion unit that converts a coordinate system from a rectangular coordinate system to a polar coordinate system,
For the image after the coordinate transformation output from the polar coordinate transformation unit, a band limiting unit that performs band limitation,
A rotation compensating unit that compensates for rotation in the circumferential direction of the band-limited image output from the band limiting unit,
An image storage unit that receives a plurality of rotation-compensated images output from the rotation compensation unit, adds the plurality of images, and accumulates the images as a single image;
An iris code generation unit that generates an iris code from an image stored in the image storage unit;
An iris authentication device, comprising: an iris code authentication unit that compares an iris code output from the iris code generation unit with an iris code registered in a database and performs authentication. An image input unit;
From the image input to the image input unit, an iris region cutout unit that detects an iris region,
For an image of an iris region obtained by the iris region cutout unit, a polar coordinate conversion unit that converts a coordinate system from a rectangular coordinate system to a polar coordinate system,
A rotation compensation unit that compensates for rotation in the circumferential direction of the image after the coordinate transformation output from the polar coordinate transformation unit,
An image storage unit that receives a plurality of rotation-compensated images output from the rotation compensation unit, adds the plurality of images, and accumulates the images as a single image;
A band limiting unit that performs band limiting on the image stored in the image storage unit,
An iris code generation unit that generates an iris code from an image output from the band limiting unit;
An iris authentication device, comprising: an iris code authentication unit that compares an iris code output from the iris code generation unit with an iris code registered in a database and performs authentication. An iris code generating step of generating an authentication iris code by the iris coding method according to any one of claims 1 to 3,
An authentication step of comparing the authentication iris code with an iris code registered in a database and performing authentication.

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