Patent Publication Number: US-2007122011-A1

Title: Face authentication system and gate management system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-345511, filed Nov. 30, 2005, the entire contents of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a face authentication system which authenticates a visitor, i.e., checks whether the visitor is a preregistered person by collating a face image obtained from the visitor with preregistered dictionary information. The present invention also relates to a gate management system which manages entrance/exit with respect to an area such as a room or facility requiring security by using the face authentication system.  
      2. Description of the Related Art  
      Jpn. Pat. Appln. KOKAI Publication No. 2001-266152 discloses a technique concerning a gate management system using a face authentication apparatus. This gate management system has a camera such as a video camera as an image sensing means. When a person to be authenticated stops in front of the camera and turns his or her face to the lens of the camera, the camera records and inputs the face image of the person. The gate management system then checks whether the person is a preregistered person by collating face feature information obtained from the input face image and unique to the person with preregistered dictionary information. If the person is a preregistered person, the gate management system opens the door (gate) of an entrance/exit target area (a room or facility).  
      As described above, a face authentication apparatus of this type records the face of a person to be authenticated when he or she stops in front of the camera. Therefore, a demand has arisen for authenticating the face of a visitor (moving person) to be authenticated before the visitor comes close to the door. However, it is difficult to appropriately records the face of a walking person, so this demand cannot be met.  
      Accordingly, a face authentication apparatus which authenticates the face of a visitor before the visitor comes close to the door is recently developed. It is also possible to arrange a plurality of face authentication apparatuses in parallel and authenticate the faces of a plurality of visitors at once, in order to manage a large traffic volume.  
      Problems arising when a plurality of face authentication apparatuses are arranged in parallel will be explained below.  
      [Problem 1] 
      A person in an adjacent passage may appear in an input image of a face authentication apparatus, so the apparatus may authenticate this person in the adjacent passage by mistake.  
      [Problem 2] 
      A display unit in an adjacent passage comes in sight of a visitor. If the visitor watches this display unit in the adjacent passage, a face authentication apparatus supposed to authenticate the face of the visitor cannot accurately obtain a front face. This may decrease the accuracy of face authentication.  
      [Problem 3] 
      A visitor who has not passed face authentication must return a passage in the opposite direction. This causes a traffic jam.  
     BRIEF SUMMARY OF THE INVENTION  
      It is, therefore, an object of the present invention to provide a face authentication system and gate management system which, when a plurality of face authentication apparatuses are arranged in parallel, prevent a person in a passage other than a passage of interest from appearing in an input image, thereby preventing a person in an adjacent passage from being authenticated by mistake.  
      It is another object of the present invention to provide a face authentication system and gate management system which, when a plurality of face authentication apparatuses are arranged in parallel, allow a passing person to easily find a target display means to watch, and stabilize the direction of the face of the passing person, thereby increasing the accuracy of face authentication.  
      It is still another object of the present invention to provide a face authentication system and gate management system which, when a plurality of face authentication apparatuses are arranged in parallel, can prevent a traffic jam even if face authentication has failed.  
      A face authentication system as an example of the present invention is a face authentication system which authenticates faces of persons passing through at least two parallel passages before the persons reach predetermined positions. This face authentication system comprises a plurality of image sensing means arranged in the predetermined positions of the plurality of passages to record images of persons passing through the passages, a plurality of face authenticating means for checking whether the persons are preregistered persons, on the basis of the images obtained from the plurality of image sensing means, and a blind plate installed between every two adjacent passages making a pair among the plurality of passages to prevent the image sensing means installed in one passage to record a person passing through the passage from recording a person passing through the other passage, wherein a recording direction of the image sensing means installed in one passage points to the other passage.  
      Also, a gate management system as an example of the present invention is a gate management system which authenticates faces of persons passing through at least two parallel passages before the persons reach entrance/exit gates, and controls opening/closing of the entrance/exit gates on the basis of authentication results. This gate management system comprises a plurality of image sensing means arranged in predetermined positions corresponding to the entrance/exit gates of the plurality of passages to record images of persons passing through the passages, a plurality of face authenticating means for checking whether the persons are preregistered persons, on the basis of the images obtained from the plurality of image sensing means, a plurality of gate control means for controlling opening/closing of the plurality of entrance/exit gates, on the basis of determination results from the plurality of face authenticating means, and a blind plate installed between every two adjacent passages making a pair among the plurality of passages to prevent the image sensing means installed in one passage to record a person passing through the passage from recording a person passing through the other passage, wherein a recording direction of the image sensing means installed in one passage points to the other passage.  
      Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
      The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the generation description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
       FIG. 1  is a schematic view showing the configuration of a gate management system to which a face authentication system according to an embodiment of the present invention is applied;  
       FIG. 2  is a block diagram showing the arrangement of a face authentication apparatus according to the embodiment of the present invention;  
       FIG. 3  is a flowchart for explaining an example of the procedure of processing of a gate controller;  
       FIG. 4  is a flowchart for explaining an example of the procedure of processing of a display/authentication controller;  
       FIGS. 5A  to  5 E are views showing examples of display windows on a display unit;  
       FIG. 6  is a view showing an example of an input image obtained from a camera;  
       FIG. 7  is a schematic view showing an example of a state in which a display unit is viewed in the directions of two adjacent passages;  
       FIG. 8  is a schematic view showing the arrangement of another face authentication apparatus which authenticates the face of a visitor before the visitor comes close to the door;  
       FIG. 9  is a schematic view showing a case in which a plurality of face authentication apparatuses shown in  FIG. 8  are arranged in parallel in a place where many visitors pass;  
       FIG. 10  is a plan view of  FIG. 9 ;  
       FIG. 11  is a view showing another example of the input image obtained from the camera;  
       FIG. 12  is a schematic view showing another example of the state in which the display unit is viewed in the directions of two adjacent passages; and  
       FIG. 13  is a schematic view for explaining the operation timings of the face authentication apparatus.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      First, another example of face authentication will be explained below with reference to FIGS.  8  to  11 . In face authentication which checks whether a visitor is a preregistered person by using a face image, recording the front face of a person is normally important to increase the accuracy of face authentication. As shown in  FIG. 8 , therefore, a camera  2  and display unit  3  are arranged close to each other to record a front face by guiding a visitor M to watch the display unit  3 . More specifically, the display unit  3  zooms and displays the recorded face of the visitor M.  
      To install the face authentication apparatus as shown in  FIG. 8  in a place where many visitors pass, it is possible to arrange a plurality of apparatuses in parallel as shown in  FIG. 9  and authenticate the faces of a plurality of visitors at once.  FIG. 10  is a plan view of  FIG. 9 .  
       FIGS. 9 and 10  illustrate an example in which four face authentication apparatuses are arranged in parallel. Visitors Ma, Mb, Mc, and Md respectively pass through parallel passages  4   a ,  4   b ,  4   c , and  4   d . Note that these visitors pass from the left to the right in the drawing. Face authentication apparatuses  5   a ,  5   b ,  5   c , and  5   d  respectively authenticate the faces of the visitors Ma, Mb, Mc, and Md. The face authentication apparatuses  5   a ,  5   b ,  5   c , and  5   d  respectively have cameras  2   a ,  2   b ,  2   c , and  2   d . In addition, the face authentication apparatuses  5   a ,  5   b ,  5   c , and  5   d  respectively have display units  3   a ,  3   b ,  3   c , and  3   d . Recording fields  6   a ,  6   b ,  6   c , and  6   d  respectively indicate recording directions corresponding to the cameras  2   a ,  2   b ,  2   c , and  2   d.    
      Passage partitions  7   a ,  7   b ,  7   c ,  7   d , and  7   e  are plates which partition the passages  4   a ,  4   b ,  4   c , and  4   d . The passage partitions prevent visitors who have once entered passages from moving to adjacent passages.  
      Problems will be explained in detail below. For example, the visitor Mb passing along the passage  4   b  shown in  FIG. 10  enters the recording field  6   a  of the camera  2   a  of the face authentication apparatus  5   a , so an input image from the camera  2   a  contains the face of the visitor Mb in the adjacent passage  4   b  as shown in  FIG. 11 . In this case, the face authentication apparatus  5   a  may authenticate the visitor Mb by mistake.  
      To solve this problem, it is possible to check whether a visitor in an input image is a person in a passage of interest by obtaining the position of the visitor by stereoscopic vision. However, this method requires the recording timings of a plurality of cameras to be the same. This increases both the apparatus cost and processing cost.  
       FIG. 12  shows a state in which the display units  3   a  and  3   b  are viewed from the passages  4   a  and  4   b . As is apparent from  FIG. 12 , both the display units  3   a  and  3   b  come in sight of the visitor Mb, so the visitor Mb may watch the display unit  3   a . If the visitor Mb turns his or her face to the display unit  3   a , the camera  2   b  cannot obtain a front face of the visitor Mb. If a front face cannot be stably obtained, the accuracy of face authentication decreases.  
      The operation timings of the face authentication apparatus will be explained below with reference to  FIG. 13 .  FIG. 13  specifically shows the passage  4   a  shown in  FIG. 10 . In a face recording start position A, the camera  2   a  starts recording the face of the visitor Ma. In an authentication end position D, the display unit  3   a  displays a message indicating whether face authentication is successful or unsuccessful. “Face authentication is successful” means that the face authentication apparatus  5   a  determines that the visitor is a preregistered person. “Face authentication is unsuccessful” means that the face authentication apparatus  5   a  cannot determine that the visitor is a preregistered person.  
      If face authentication is successful, the visitor Ma moves toward the entrance (door). If face authentication is unsuccessful, the visitor Ma returns from the authentication end position D in the direction opposite to the passing direction (from the right to the left in the drawing). While the visitor Ma who has not passed face authentication is returning the passage  4   a , a traffic jam occurs in the passage, so the face authentication apparatus  4   a  cannot be efficiently used.  
      An embodiment of the present invention will be explained below with reference to the accompanying drawing.  
      Note that in the following explanation, the same reference numerals as in FIGS.  8  to  13  described above denote the same parts.  
       FIG. 1  schematically shows the configuration of a gate management system to which a face authentication system according to this embodiment is applied. Referring to  FIG. 1 , a plurality of (four in this example) parallel passages  4   a ,  4   b ,  4   c , and  4   c  respectively communicate with gate apparatuses (entrance/exit gates)  11   a ,  11   b ,  11   c , and  11   d  installed at the entrance of an entrance/exit target area (e.g., a room or facility). Visitors (persons) Ma, Mb, Mc, and Md respectively pass along the passages  4   a ,  4   b ,  4   c , and  4   d  toward the gate apparatuses  11   a ,  11   b ,  11   c , and  11   d  (from the left to the right in the drawing).  
      The passages  4   a ,  4   b ,  4   c , and  4   d  have passage partitions (plates)  7   a ,  7   b ,  7   c ,  7   d ,  7   e , and  7   f  which prevent visitors who have once entered passages from moving to adjacent passages.  
      Face authentication apparatuses  5   a ,  5   b ,  5   c , and  5   d  are respectively installed on the sides of the passages  4   a ,  4   b ,  4   c , and  4   d  and in positions before and close to the gate apparatuses  11   a ,  11   b ,  11   c , and  11   d . The face authentication apparatuses  5   a ,  5   b ,  5   c , and  5   d  respectively include video cameras (to be simply abbreviated as cameras hereinafter)  2   a ,  2   b ,  2   c , and  2   d  as image sensing means for recording images containing at least the faces of the visitors Ma, Mb, Mc, and Md, and display units  3   a ,  3   b ,  3   c , and  3   d  as display means for displaying, e.g., the present face authentication statuses to the visitors Ma, Mb, Mc, and Md. The face authentication apparatuses  5   a ,  5   b ,  5   c , and  5   d  respectively authenticate the faces of the visitors Ma, Mb, Mc, and Md.  
      Assume that two adjacent passages make a pair and two face authentication apparatuses installed in these two passages also make a pair. In this example, the passages  4   a  and  4   b , the face authentication apparatuses  5   a  and  5   b , the passages  4   c  and  4   d , and the face authentication apparatuses  5   c  and  5   d  make pairs. As shown in  FIG. 1 , recording fields  6   a  and  6   b  of the cameras  2   a  and  2   b  of the paired face authentication apparatuses  5   a  and  5   b  point to each other&#39;s passages, and recording fields  6   c  and  6   d  of the cameras  2   c  and  2   d  of the paired face authentication apparatuses  5   c  and  5   d  point to each other&#39;s passages. That is, the recording direction of the camera  2   a  installed in the passage  4   a  points to the passage  4   b , and the recording direction of the camera  2   b  installed in the passage  4   b  points to the passage  4   a . Also, the display screens of the display units  3   a ,  3   b ,  3   c , and  3   d  respectively point to the same directions as the recording fields  6   a ,  6   b ,  6   c , and  6   d  of the corresponding cameras  2   a ,  2   b ,  2   c , and  2   d . That is, the camera  2   a  and display unit  3   a  corresponding to the face authentication apparatus  5   a  are paired, and the display direction of the display unit  3   a  is set to point to the same direction as the recording direction of the camera  2   a.    
      Blind plates  12   a  and  12   b  stand upright between the paired passages  4   a  and  4   b  and between the paired passages  4   c  and  4   d , respectively. Each of the blind plates  12   a  and  12   b  is a blind plate which prevents a visitor passing through one passage from entering the recording field of the camera of the face authentication apparatus in the other passage. More specifically, the blind plates  12   a  and  12   b  are respectively installed on the passage partitions  7   b  and  7   e.    
      The blind plate  12   a  prevents the camera  2   a  from recording the visitor Mb passing through the passage  4   b , and prevents the camera  2   b  from recording the visitor Ma passing through the passage  4   a . Similarly, the blind plate  12   b  prevents the camera  2   c  from recording the visitor Md passing through the passage  4   d , and prevents the camera  2   d  from recording the visitor Mc passing through the passage  4   c . Also, the blind plate  12   a  is formed on only a portion of the passage partition  7   b , and does not cover the whole of the passages  4   a  and  4   b  (covers only parts of the passages  4   a  and  4   b ). Likewise, the blind plate  12   b  is formed on only a portion of the passage partition  7   e , and does not cover the whole of the passages  4   c  and  4   d  (covers only parts of the passages  4   c  and  4   d ). The blind plates  12   a  and  12   b  are arranged as described above so as not to obstruct the view of, e.g., one security guard who checks the whole of the passages  4   a ,  4   b ,  4   c , and  4   d.    
      Return passages  13   a ,  13   b , and  13   c  which allow visitors who have not passed face authentication to return are respectively formed outside the paired passages  4   a  and  4   b , between the paired passages  4   a  and  4   b  and the paired passages  4   c  and  4   d , and outside the paired passages  4   c  and  4   d . In the example shown in  FIG. 1 , a visitor Me who has not passed face authentication walks along the return passage from the right to the left in the drawing.  
      As shown in  FIG. 1 , if the visitor Ma has passed face authentication in the passage  4   a , the visitor Ma passes through the gate apparatus  11   a  as indicated by an arrow A near the entrance of the passage  4   a . If the visitor Ma has not passed face authentication, the visitor Ma moves to the return passage  13   a  through a connection gate  14   a  formed near the entrance of the passage  4   a  as indicated by an arrow B near the entrance, and returns in the direction (from the right to the left in the drawing) opposite to that when he or she enters. This similarly applies to the passages  4   b ,  4   c , and  4   d.    
      The arrangement of the face authentication apparatuses  5   a ,  5   b ,  5   c , and  5   d  will be explained below with reference to  FIG. 2 . Note that the face authentication apparatuses  5   a ,  5   b ,  5   c , and  5   d  have the same arrangement, so only the face authentication apparatus  5   a  will be explained as a representative.  
      The face authentication apparatus  5   a  comprises the camera  2   a , the display unit  3   a , and a processor  20 . The processor  20  comprises a face detector  21 , face authentication dictionary  22 , face authentication unit  23 , gate controller  24 , and display/authentication controller  25 . The face detector  21  is a face detecting means for detecting the face region of the visitor Ma from each image recorded by the camera  2   a . The face authentication dictionary  22  is a dictionary storage means in which a plurality of pieces of dictionary information are preregistered (prestored). The face authentication unit  23  is an authenticating means for determining whether the visitor Ma is a preregistered person by collating an image of the face region detected by the face detector  21  with the dictionary information preregistered in the face authentication dictionary  22 . The controller  24  is a gate control means for controlling the gate apparatus  11   a  on the basis of the determination result from the face authentication unit  23 . The display/authentication controller  25  is a control means for controlling the overall operation.  
      The individual constituent elements will be explained in detail below.  
      The face detector  21  detects a region where the face exists in an image obtained from the camera  2   a . The face region detecting process uses, e.g., a method described in reference (Mita, Kaneko, and Hori, “Proposal of Spatial Difference Probability Template Suited to Collation of Images Including Fine Differences”, The 9th Image Sensing Symposium Lecture Papers, SSII03, 2003). This method forms detection dictionary patterns from face learning patterns beforehand, and searches an input image for a pattern having high similarity to the dictionary patterns.  
      The face authentication unit  23  checks whether the image in the face region from the face detector  21  is preregistered. More specifically, as described in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2001-266152, the face authentication unit  23  prepares face images of registrants (visitors), and prestores (preregisters) unique feature information extracted from the face images in the face recognition dictionary  22 . The face authentication unit  23  then collates an image (feature information) of a face region detected by the face detector  21  with the dictionary information preregistered in the face recognition dictionary  22 , thereby obtaining the similarity between them. If the obtained similarity is equal to or larger than a preset threshold value, the face authentication unit  23  determines that the visitor Ma is a preregistered person. If the obtained similarity is smaller than the threshold value, the face authentication unit  23  determines that the visitor Ma is not a preregistered person.  
      When the gate apparatus  11   a  is a door, the gate controller  24  unlocks the door if a passing enable signal from the display/authentication controller  25  is ON. When the gate apparatus  11   a  is a flapper, the gate controller  24  generates an alarm sound and closes the flapper if the visitor Ma enters the gate apparatus  11   a  although the passing enable signal is OFF, thereby inhibiting the passing of the visitor Ma. More specifically, the gate controller  24  performs control as indicated by a flowchart shown in  FIG. 3 .  
      The display/authentication controller  25  controls the whole apparatus. A flowchart in  FIG. 4  shows the procedure of processing. This flowchart shown in  FIG. 4  will be explained below. Assume that points A, B, and C shown in  FIG. 4  are points in the passage  4   a  shown in  FIG. 13 .  
      First, the display/authentication controller  25  acquires the processing result of the face detector  21  (step S 1 ), and checks whether the person (visitor Ma) to be authenticated is closer to the camera  2   a  than the point A (step S 2 ). If the visitor Ma is not closer to the camera  2   a  than the point A, the display/authentication controller  25  displays an image from the camera  2   a  on the display unit  3   a  (step S 3 ), and returns to step S 1  to repeat the same operation.  
      If the result of the check in step S 2  indicates that the face region of the visitor Ma is detected and the visitor Ma having this face is closer to the camera  2   a  than the point A, the display/authentication controller  25  regards the visitor Ma as an object of face authentication, and checks whether the visitor Ma is between the points A and B in the passage  4   a  (step S 4 ). Note that the display/authentication controller  25  predicts the position of a person from, e.g., the size of the detected face.  
      If the result of the check in step S 4  indicates that the visitor Ma to be authenticated is between the points A and B, as shown in  FIG. 5A , the display/authentication controller  25  displays an overall input image  31  obtained from the camera  2   a  on the display unit  3   a , and simultaneously displays a frame  32  indicating the detected face region (step S 5 ). After that, the display/authentication controller  25  returns to step S 1  to repeat the same operation.  
      If the result of the check in step S 4  indicates that the visitor Ma to be authenticated is not between the points A and B, the display/authentication controller  25  checks whether the visitor Ma is between the points B and C in the passage  4   a  (step S 6 ). If the visitor Ma is between the points B and C, as shown in  FIG. 5B , the display/authentication controller  25  displays the detected face image in an enlarged scale on the display unit  3   a  (step S 7 ), and returns to step S 1  to repeat the same operation.  
      If the result of the check in step S 6  indicates that the visitor Ma is not between the points B and C, the display/authentication controller  25  checks whether the number of collected face images of the detected object to be authenticated is equal to or larger than a minimum predetermined number (N_IMG) necessary for authentication (step S 8 ). If the number of collected face images of the object to be authenticated is smaller than the predetermined number (N_IMG), the display/authentication controller  25  displays a message representing the failure of authentication on the display unit  3   a  (step S 9 ), and returns to step S 1  to repeat the same operation.  
      If the result of the check in step S 8  indicates that the number of face images of the object to be authenticated is equal to or larger than the predetermined number (N_IMG), the display/authentication controller  25  supplies the images (face images) of the face region detected by the face detector  21  to the face authentication unit  23 , and starts face authentication (step S 10 ). As shown in  FIG. 5C , the display/authentication controller  25  displays a message “Authenticating . . . ” on the display unit  3   a  (step S 11 ), and waits until the face authentication process is complete (step S 12 ).  
      If the face authentication process is complete, the display/authentication controller  25  checks whether the authentication result is successful or unsuccessful (step S 13 ). If the authentication result is successful, as shown in  FIG. 5D , the display/authentication controller  25  displays a message “Authentication OK Please Pass” on the display unit  3   a  (step S 14 ), and turns on the passing enable signal to the gate controller  24  for a predetermined time (step S 15 ). This allows the visitor Ma to pass through the gate apparatus  11   a .    
      After that, the display/authentication controller  25  waits until a predetermined time elapses since the passing enable signal is turned on or a passing completion signal is received from the gate controller  24  (step S 16 ). If the predetermined time has elapsed since the passing enable signal is turned on or the passing completion signal is received from the gate controller  24 , the display/authentication controller  25  returns to step S 1  to repeat the same operation.  
      If the result of the check in step S 13  indicates that the authentication result is unsuccessful, as shown in  FIG. 5E , the display/authentication controller  25  displays a message “Authentication NG” on the display unit  3   a  for a predetermined time (step S 17 ), and returns to step S 1  to repeat the same operation.  
      As explained above, this embodiment can reduce the number of blind plates. That is, two face authentication apparatuses and two passages are paired, and the cameras of the paired face authentication apparatuses are turned to each other&#39;s passages. Therefore, a blind plate need only be installed between the two passages making a pair. This makes the number of blind plates smaller than that in the conventional arrangement as shown in  FIG. 9 . This arrangement shown in  FIG. 9  requires blind plates between all passages.  
      Also, no person in a passage other than a passage of interest appears in an input image. Therefore, no visitor in an adjacent passage is detected as an object of authentication by mistake. That is, as indicated by an example of an input image shown in  FIG. 6 , the input image does not contain any person in an adjacent passage owing to the blind plate  12 , and contains only a visitor M in a passage of interest. Consequently, no visitor in an adjacent passage is detected as an object of authentication by mistake.  
      In addition, a visitor can easily find a target display unit to watch, so the direction of the face of the visitor stabilizes. This increases the authentication accuracy.  FIG. 7  shows the display unit  3   b  viewed in the directions of the passages  4   a  and  4   b . Since the blind plate  12   a  prevents the visitor Mb from watching the display unit  3   a  in the adjacent passage  4   a , the visitor Mb can readily watch the display unit  3   b  carefully and stably turns his or her face to the display unit  3   b . Consequently, the camera  2   b  can stably record a front face, so the accuracy of face authentication increases.  
      It is also possible to prevent a traffic jam when face authentication is unsuccessful. That is, return passages are formed for visitors who have not passed face authentication. Therefore, a visitor who has not passed face authentication need not return the passage for authentication unlike in the conventional system, and this prevents a traffic jam.  
      Furthermore, the insta 11   a  tion space can be reduced because the return passages for visitors who have not passed face authentication can be shared. That is, when a plurality of paired passages are arranged in parallel, adjacent pairs can share one return passage. This effectively reduces the insta 11   a  tion space.  
      The passages  4   a ,  4   b ,  4   c , and  4   d  of the face authentication system of this embodiment described above can also be autowalks or escalators. Since a person often stands still on an autowalk or escalator, it is possible to stably obtain a person image and increase the authentication accuracy.  
      Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.