Abstract:
A device includes a supporting mechanism which movably supports a living body, light sources which emit near infrared rays, an imaging unit which picks up venous images of the living body with light emitted from the light sources and an image processing unit which processes venous images picked up by the imaging unit, wherein the imaging unit picks up a plurality of still images consecutively from the living body which travels supported by the supporting mechanism and the image processing unit forms an image pattern of the living body by subjecting the obtained plurality of still images to processing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a biometrics device, and more particularly to a vein authentication device which authenticates individuals by use of venous information obtained by sweeping finger veins. 
         [0002]    Development of authentication devices as a technique for authenticating individuals by use of biometric information is making progress, and such devices are now coming into practical use in PCs, mobile terminals, automatic telling machines (ATMs) and automobiles. The working principle of vein authentication devices is that a living body is irradiated with near infrared rays, and the rays which are scattered within the body and later transmitted outside the body are formed into a biometric image. As hemoglobin in the blood absorbs near infrared rays, it emerges in the formed image as a dark shadowy pattern, and thereby enables veins to be recognized as such shadowy patterns. A vein authentication device authenticates an individual by computing the correlation between the imaged pattern and a pertinent pattern in biometric information images registered in advance. 
         [0003]    Known vein authentication devices as such include, for instance, those disclosed in JP-A-253989/2005 (Patent Reference 1) and JP-A-235049/2005 (Patent Reference 2). 
         [0004]    Conventional vein authentication devices inevitably have to be structured in larger dimensions than the living objects because of the need to acquire overall information on the objects to be measures. However, larger authentication devices are correspondingly more costly and may be restricted in mounting convenience. Therefore, more compact vein authentication devices are called for. 
       SUMMARY OF THE INVENTION 
       [0005]    An object of the present invention is to provide a less expensive and more compact biometrics device. 
         [0006]    Another object of the invention is to provide a vein authentication device which, when biometric information is to be acquired by having a living body sweep, can provide a constant venous image pattern even if the sweeping velocity varies. 
         [0007]    Preferably, the invention is configured as a biometrics device including a supporting mechanism which movably supports a living body, light sources which emit near infrared rays, an imaging unit which picks up venous images of the living body with light emitted from the light sources and an image processing unit which processes venous images picked up by the imaging unit, wherein the imaging unit picks up a plurality of still images consecutively from the living body which travels supported by the supporting mechanism and the image processing unit forms an image pattern of the living body by subjecting the obtained plurality of still images to processing. 
         [0008]    In a preferable example, the supporting mechanism has a roller over which a finger is to be placed and a lead screw which turns interlocked with the roller, the lead screw is illuminated with light from the light sources, and the imaging unit obtains still images of the lead screw and venous images of the finger. 
         [0009]    Preferably, predetermined positions on the lead screw are marked, and the image processing unit, computing travel distances of the finger with reference to those marks in the still images obtained, processes combination of each plurality of still images of the finger obtained from the imaging unit by use of the computed travel distances. 
         [0010]    Another preferable example of the invention is configured as a biometrics device including a supporting mechanism which movably supports a living body, light sources which emit near infrared rays, reflective light sources which are arranged in a substantially horizontal direction, an imaging unit which picks up a plurality of venous images and a plurality of surface images of the living body while alternately causing the reflective light sources and the light sources of near infrared rays to emit light, and an image processing unit which computes travel distances of characteristic points of the surface images from the plurality of surface images obtained and processes combination of the plurality of venous images into a single image pattern. Preferably, it is further equipped with a luminous energy adjusting unit which adjusts the luminous energy of the reflective light sources arranged in a substantially horizontal direction, wherein, after the luminous energy outputs of the reflective light sources have been stabilized, the imaging unit picks up and acquires an image of the finger for authentication processing. 
         [0011]    According to the invention, since it enables image information on a living body to be acquired processed while moving it, a low-cost and compact vein authentication device can be realized. Further, a constant venous image pattern can be obtained even if the sweeping velocity varies. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Preferred embodiments of the present invention will now be described in conjunction with the accompanying drawings, in which: 
           [0013]      FIG. 1  shows a profile of an image input unit  1  of a vein authentication device, which is a first embodiment of the invention; 
           [0014]      FIG. 2  shows the internal structure of the image input unit  1  in the first preferred embodiment of the invention; 
           [0015]      FIG. 3  is a configurational diagram of the vein authentication device, which is the first embodiment of the invention; 
           [0016]      FIG. 4  shows contents stored in a memory  9  of an authentication processing unit  8  in the first embodiment of the invention; 
           [0017]      FIG. 5  shows an initial input screen in the first embodiment of the invention; 
           [0018]      FIG. 6  shows an input image after a finger has traveled away in the first embodiment of the invention; 
           [0019]      FIGS. 7A and 7B  are intended for use in the description of vein image pasting in the first embodiment of the invention; 
           [0020]      FIG. 8  shows a profile of the image input unit  1  in a second preferred embodiment of the invention; 
           [0021]      FIG. 9  shows a top view of the image input unit  1  in the second preferred embodiment of the invention; 
           [0022]      FIG. 10  shows a venous image of a finger in the second embodiment of the invention; 
           [0023]      FIG. 11  shows contents stored in the memory  9  of the authentication processing unit  8  in the second embodiment of the invention; 
           [0024]      FIGS. 12A to 12C  are intended for use in the description of the generation of a finger surface image in the second embodiment of the invention; and 
           [0025]      FIGS. 13A and 13B  illustrate how a venous image of a finger is formed from its surface image in the second embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Preferred embodiments of the present invention will be described below with reference to the drawings. 
         [0027]    First, the first preferred embodiment of the invention will be described with reference to  FIGS. 1 through 7B . 
         [0028]      FIG. 1  shows a profile of the image input unit  1  of a vein authentication device and  FIG. 2  shows its plan. The image input unit  1  has light sources  3  arranged in two positions and emitting near infrared rays, an imaging unit  2  which picks up venous images of a finger F with light from the light sources  3 , a roller  5  which turns mounted with the finger F, a lead screw  6  which turns interlocked with this roller  5 , and an auxiliary light source  7  which illuminates the lead screw  6 . 
         [0029]    As shown in  FIG. 2 , the structure is such that the roller  5  and the lead screw  6  are fixed to their respective rotation shafts  40  parallel to each other and are mutually interlocked via linking gears  41 . The lead screw  6  is provided with colored grooves  17  at prescribed intervals to clearly measure the sweep quantity. These grooves  17  are colored black and do not reflect the light from the auxiliary light source  7 . Other grooves do reflect the light from the auxiliary light source  7 . In the input images, the colored grooves  17  are seen as black images as shown in  FIG. 5 . 
         [0030]    It is preferable here for the widthwise shape of the roller  5  to be substantially equal to the width of the finger F to be placed over it. This enables the placing position of the finger F of the object to be clearly defined and the sweep of the finger F to be guided to linearity. Also, grooves  51  matched in shape with the finger F are formed in the roller  5 , and these grooves  51  can prevent veins from being flattened. 
         [0031]    Incidentally, though two light sources  3  are arranged in the illustrated case to pick up clear venous images, one light source  3  will suffice if proper images can be obtained. 
         [0032]    As shown in  FIG. 3 , the vein authentication device is configured of an image input unit  1  and an authentication processing unit  8 . The authentication processing unit  8  has a CPU  10 , a memory  9 , a storage unit  11 , a display unit  13  and interfaces  12 . The CPU  10  here performs various processing functions by executing programs stored in the memory  9 . The functions of these programs will be described afterwards. The memory  9  also stores image data acquired by the imaging unit  2 . The storage unit  11  stores predetermined venous image data. The interfaces  12  connect the imaging unit  2 , the storage unit  11  and the image input unit  1 . 
         [0033]    The display unit  13  is connected to the authentication processing unit  8  to display situations including the result of authentication. Incidentally, this display unit  13  is dispensable. Where it is dispensed with, the result of authentication is made known by an alarm and the like. 
         [0034]      FIG. 4  shows the stored contents of the memory  9  of the authentication processing unit  8 . 
         [0035]    The programs stored in the memory  9  include a lead screw detection program  18  for detecting and computing the quantities of variation of the lead screw image, an image data pasting program  24  for composing (pasting together) a biometric image on the basis of the quantities of variation computed according to the lead screw detection program  18 , and a characteristics collation program  21  for extracting characteristics of biometric information data  23 , collating them with a group of characteristic data registered in the storage unit  11  in advance and determining whether or not the biometric information data  23  is valid. The sets of data stored include input image data  15  and the biometric information data  23 . 
         [0036]    Next, the authentication processing by the vein authentication device of this embodiment will be described with reference to  FIGS. 5 through 7B . 
         [0037]    As the image picked up from the initial state, an image of the lead screw  6  is picked up keeping only the auxiliary light source  7  lit. In this state, the positions of the grooves  17  in the lead screw  6  are detected and monitored by the authentication processing unit  8 . Next, when the finger F is placed over the roller  5 , the image of the grooves  17  picked up by the imaging unit  2  varies. By causing the authentication processing unit  8  to recognize this, the light sources  3  are lit to start vein authentication processing. Or, it may be recognized by the method disclosed in Patent Reference 2 that the relative brightness of the input image has surpassed or fallen below a threshold, and the light sources  3  are lit accordingly. 
         [0038]    When the light sources  3  are lit, the finger F is irradiated with near infrared rays. The light scattered within the finger F is picked up as an image  15 A containing a venous image  14 A and a lead screw image  16 A by the imaging unit  2  ( FIG. 5 ). The picked-up image of the finger is stored into the area for the input image data  15  in the memory  9  as the initial input image via the interface  12 . Correspondingly to this image  15 A, the CPU  10  is caused to store the venous image  14 A into the area for the biometric information data  23 , and at the same time the positions of the grooves  17  of the lead screw image  16 A are recognized. 
         [0039]    In this while, the finger of the object is traveling over the roller  5  from its position in the initial state. 
         [0040]    An image  15 B to be picked up next is an image after a travel relative to the initial image  15 A. This image  15 B is shown in  FIG. 6 . 
         [0041]    The CPU  10  cuts a lead screw image  16 B out of the image  15 B, detects a travel distance  19  of the grooves  17  and computes the travel distance  20  ( FIGS. 7A and 7B ) from the initial venous image  14 B. A venous image  14 C equivalent to the travel distance  20  is thereby pasted onto the biometric information data  23 . As the state of the pasted biometric information  23  shown in  FIG. 7B  indicates, the earlier image  14 A and the subsequently acquired image  14 C are pasted together. 
         [0042]    This processing is executed in the following manner. For instance, input image data (n) are inputted, and a lead screw image  16 ( n ) is cut out of the input image data (n). Next, it is compared with a lead screw image  16  (n−1) and a travel distance  19 ( n ) is detected. And a travel distance  20 ( n ) is computed from the travel distance  19 ( n ), and a venous image  14 ( n ) in input image data  15 ( n ) is cut out in an equivalent to the travel distance  20 ( n ) for the biometric information data  23  (n−1) and pasted onto a venous image  14  (n−1). After that, the processing shifts to inputting of input image data (n+1). 
         [0043]    As the travel distance  19  of the grooves  17  here is in direct proportion to the travel distance  20  from the venous image  14 A to the venous image  14 B, the CPU  10  can process pasting by merely performing simple computation of adding or subtracting the overlapping part of the pasting. This enables the required computation of the travel distances of images to be significantly reduced. Further, it is made possible, when pasting the venous image  14 C, to correct the pasting position of the venous image  13 C by comparing and collating the remaining part of the venous image  14 B after the removal of the venous image  13 C with the venous image data  14 A stored in the biometric information  23 , thereby enabling more accurate image pasting to be processed. 
         [0044]    By repeating the processing described so far, venous information  22  on the whole finger F which is the object is stored into the biometric information data area  23 . This processing makes it possible to check whether or not the generated biometric information data  23  matches the pertinent person by executing the characteristics collation program  21  and thereby comparing and collating it with a pattern stored in the storage unit  11 . 
         [0045]    Next, a second embodiment of the present invention will be described with reference to  FIG. 8  and subsequent drawings. 
         [0046]    As shown in  FIG. 8 , the second embodiment of the invention has reflective light sources  31  for a living body in its image input unit  30 . Compared with the image input unit  1  shown in  FIGS. 1 through 3 , it has the same configuration as the vein authentication device of the first embodiment except for the absence of the auxiliary light source  7 , and the same parts will be assigned respectively the same reference signs. Duplication of a description will be dispensed with. 
         [0047]    As shown in  FIG. 9 , in order to more clearly image the shades of the unevenness of the finger F, reflective light sources  31 A and  31 B using visible light are arranged in a substantially horizontal direction. The reflective light sources  31 A and  31 B enables a surface image of the finger F to be picked from both right and left by alternately irradiating the finger. Whereas it is preferable for the reflective light sources  31  here to be long-wavelength blue LEDs in order to obtain the surface image of the finger F clearly, other visible light may as well be used if the image can be obtained clearly. 
         [0048]    As a surface image is obtained by irradiation from the two reflective light sources  31 A and  31 B, areas for right surface image data  35  and left surface image data  36  are also secured for the data to be stored in the memory  9  as shown in  FIG. 11 . 
         [0049]      FIG. 10  shows acquired finger vein image data, wherein reference sign  32 A denotes venous image data inputted for the n-th time and  32 B denotes venous image data inputted for the (n+1)-th time. 
         [0050]      FIG. 11  shows the stored contents of the memory  9 . 
         [0051]    A characteristics extraction program  33  extracts characteristic points of input images (venous image, right surface image and left surface image). An image data pasting program  34  realizes the function of detecting the travel distance of image data from the characteristic points extracted from the characteristics extraction program  33 , correcting the travel distance and pasting the image data. 
         [0052]    Right surface image data  35  stores the right half of the image, and left surface image data  36  stores the left half. Surface image data  37  stores image data resulting from the processing to correct the travel distance of the image according to the characteristic points of the right surface image  35  and of the left surface image  36  which have been cut out. 
         [0053]    The venous image data  32  stores data after the processing to paste an image equivalent to the travel distance cut out of the venous image  32 B onto the venous image  32 A. For instance, this processing is accomplished by computing the travel distance  39  in the x-axis direction and the travel distance  90  in the y-axis direction by comparing the characteristic points of a surface image  37 A which constitutes the n-th input image and of a surface image  37 B which constitutes the (n+1)-th input, cutting an image equivalent to the travel distance out of the venous image  32 B and pasting it onto the venous image  32 A. 
         [0054]    A characteristics collation program  38  compares a finger vein image  41  finished by the image data pasting program  34  with a group of characteristic data registered in the storage unit  11  in advance, and determines whether or not the finger vein image  41  is valid. 
         [0055]    Next, a method of acquiring the venous image of the finger F using this embodiment will be described. 
         [0056]    When the finger F is placed over the image input unit  30 , the finger F is imaged first with the light sources  3  and the reflective light sources  31 A and  31 B. The authentication processing unit  8  checks whether or not the contour of the finger F can be distinguished or whether or not the image is free from halation, and the optimal luminous energy is set for each light source. 
         [0057]    After this setting has been completed, the light sources  3  are lit to pick up a one-frame equivalent of the venous image  32 A, which is stored into the venous image data  32  in the memory  9  via the interface  12 , and the CPU  10  processes extraction of characteristics of the venous image data. Next, the light sources  3  are turned off, the reflective light source  31 A is turned on to pick up a one-frame equivalent of a surface image  35 A, which is stored into the right surface image data  35  in the memory  9  via the interface  12 , followed by similar processing to extract characteristics. 
         [0058]    Then, the reflective light source  31 A is turned off, and the reflective light sources  31 B to pick up a one-frame equivalent of a surface image  36 A, which is stored into the left surface image data  36  in the memory  9  via the interface  12  to be subjected to processing to extract characteristics. Since there is a time lag equivalent to one frame between the right surface image data  35  and the left surface image data  36 , the lag is compensated for by collating characteristic points extracted from the respective central parts of the images of the right surface image data  35  and the left surface image data  36 . Further, the center is extracted from the finger contour of the left right surface image, and the surface image  37 A of the finger F can be formed by pasting together the right half of the right surface image  35  and the left half of the left surface image  36  ( FIGS. 12A to 12C ). 
         [0059]    By repeating the processing described so far, the venous images  32 B and the surface images  37 B of the second and subsequent frames can be obtained. How this is accomplished is shown in  FIGS. 13A and 13B . Since more characteristics can be extracted here from a surface image than from a venous image, by comparing the surface images  37 A and the surface images  37 B with the sweeping method, the travel distance  90  of the finger F in the vertical direction can be computed. Further, as the travel distance  39  in the horizontal direction, which is the positional lag in the right-and-left direction, can also be detected on the basis of contour extraction or detected data of characteristic points of the finger F, it is made possible to paste together the venous image  32 A and the venous image  32 B with high accuracy after the venous images by use of this data and pasting them together. 
         [0060]    Since the travel distance can be consecutively computed from the surface images of the finger F by repeating the processing described so far, it is made possible to obtain venous images matching the computed travel distances, to obtain the overall venous image and characteristic point data of the finger F with high accuracy by pasting them together, and thereby to acquire overall venous image data  91  of the finger F to be authenticated. The overall venous image data  91  so acquired is compared and collated with a pattern stored in the storage unit  11  by executing the characteristics collation program  38 . As a result of this collation, it can be checked whether or not the acquired venous image data  91  fits the legitimate person. 
         [0061]    Further, when surface image information on the finger F is to be authenticated, if the travel distance can be adequately computed from only the left surface image or the right surface image, only one side image will suffice, and in this case, the cost can be saved and the time taken to process computation can be reduced. 
         [0062]    This embodiment of the invention, since it requires no addition of any particular encoder mechanism and can measure the travel distance of sweeping by a living body, a low-cost and compact vein authentication device can be realized.