Patent Publication Number: US-2021182538-A1

Title: Face recognition system, face recognition method, display control apparatus, display control method, and display control program

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a Continuation Application of U.S. application Ser. No. 16/129,275 filed on Sep. 12, 2018, which is a Continuation Application of U.S. application Ser. No. 15/758,185 filed on Mar. 7, 2018, which issued as U.S. Pat. No. 10,671,837, which is a National Stage of International Application No. PCT/JP2016/066778 filed on Jun. 6, 2016, and which claims priority based on Japanese Patent Application No. 2015-176534 filed on Sep. 8, 2015, the contents of all of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a face recognition system, a face recognition method, a display control apparatus, a display control method, and a display control program. 
     BACKGROUND ART 
     In the above technical field, patent literature 1 discloses a technique of searching for an image from an image database by collation for each pair of portions (eyes, mouths, or noses) of face images. Patent literature 2 discloses a technique of notifying a user of a corresponding response sentence based on a similarity obtained by collation for each pair of portion regions (eye regions, mouth regions, or nose regions) of face images. 
     CITATION LIST 
     Patent Literature 
     Patent literature 1: Japanese Patent Laid-Open No. 2010-146581 
     Patent literature 2: Japanese Patent Laid-Open No. 2005-078413 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     In the techniques described in the above patent literatures, however, only information based on a face recognition result is output. Therefore, an operator cannot grasp a factor leading the face recognition result at a glance to confirm or modify the face recognition result on the spot. 
     The present invention enables to provide a technique of solving the above-described problem. 
     Solution to Problem 
     One example aspect of the present invention provides a display control apparatus comprising: 
     a similarity acquirer that acquires a similarity between each pair of partial regions of face images by performing collation processing between the each pair of partial regions of the face images; and 
     a display controller that controls to overlay, on the face images, at least one of a first region the similarity of which exceeds a threshold and a second region the similarity of which does not exceed the threshold, and display the overlaid face images. 
     Another example aspect of the present invention provides a display control method comprising: 
     acquiring a similarity between each pair of partial regions of face images by performing collation processing between the each pair of partial regions of the face images; and 
     controlling to overlay, on the face images, at least one of a first region the similarity of which exceeds a threshold and a second region the similarity of which does not exceed the threshold, and display the overlaid face images. 
     Still other example aspect of the present invention provides a display control program for causing a computer to execute a method, comprising: 
     acquiring a similarity between each pair of partial regions of face images by performing collation processing between the each pair of partial regions of the face images; and 
     controlling to overlay, on the face images, at least one of a first region the similarity of which exceeds a threshold and a second region the similarity of which does not exceed the threshold, and display the overlaid face images. 
     Still other example aspect of the present invention provides a face recognition system comprising: 
     an image capturer that generates a first face image; 
     an accumulator that accumulates a second face image; 
     a deriving unit that derives a similarity between each pair of a partial region of the first face image and a partial region of the second face image by performing collation processing between the each pair of partial regions of the first face image and the second face image;
         a face recognizer that recognizes the first face image based on derived similarities of the partial regions; and       

     a display unit that overlays, on at least one of the first face image and the second face image, a result of recognizing the first face image and at least one of a first region the similarity of which exceeds a threshold and a second region the similarity of which does not exceed the threshold, and displays the overlaid face images. 
     Still other example aspect of the present invention provides a face recognition method comprising: 
     deriving a similarity between each pair of a partial region of a first face image generated by an image capturer and a partial region of a second face image accumulated by an accumulator by performing collation processing between the each pair of partial regions of the first face image and the second face image; 
     recognizing the first face image based on derived similarities of the partial regions; and 
     overlaying, on at least one of the first face image and the second face image, a result of recognizing the first face image and at least one of a first region the similarity of which exceeds a threshold and a second region the similarity of which does not exceed the threshold, and displaying the overlaid face images on a display unit. 
     Advantageous Effects of Invention 
     According to the present invention, since an operator can grasp a factor leading a face recognition result at a glance, he/she can confirm or modify the face recognition result on the spot. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram showing the arrangement of a display control apparatus according to the first example embodiment of the present invention; 
         FIG. 2A  is a view showing an outline of a display screen according to the second example embodiment of the present invention; 
         FIG. 2B  is a view showing another outline of the display screen according to the second example embodiment of the present invention; 
         FIG. 3  is a block diagram showing the arrangement of a face recognition system according to the second example embodiment of the present invention; 
         FIG. 4  is a sequence chart showing the operation procedure of the face recognition system according to the second example embodiment of the present invention; 
         FIG. 5  is a block diagram showing the functional arrangement of a display control apparatus according to the second example embodiment of the present invention; 
         FIG. 6  is a table showing the structure of a face image storage according to the second example embodiment of the present invention; 
         FIG. 7  is a table showing the structure of a threshold storage according to the second example embodiment of the present invention; 
         FIG. 8A  is a table showing the structure of a mark storage according to the second example embodiment of the present invention; 
         FIG. 8B  is a table showing the structure of an overlaying image data generation table according to the second example embodiment of the present invention; 
         FIG. 9  is a table showing the structure of an overlaid display data generation table according to the second example embodiment of the present invention; 
         FIG. 10  is a block diagram showing the functional arrangement of a face recognition apparatus according to the second example embodiment of the present invention; 
         FIG. 11A  is a table showing the structure of a captured face image database according to the second example embodiment of the present invention; 
         FIG. 11B  is a table showing the structure of a collation target face image database according to the second example embodiment of the present invention; 
         FIG. 12  is a table showing the structure of a partial region database according to the second example embodiment of the present invention; 
         FIG. 13  is a table showing the structure of a face recognition table according to the second example embodiment of the present invention; 
         FIG. 14  is a block diagram showing the functional arrangement of an operator terminal according to the second example embodiment of the present invention; 
         FIG. 15  is a table showing the structure of an operation processing table according to the second example embodiment of the present invention; 
         FIG. 16  is a block diagram showing the hardware arrangement of the display control apparatus according to the second example embodiment of the present invention; 
         FIG. 17  is a flowchart illustrating the processing procedure of the display control apparatus according to the second example embodiment of the present invention; 
         FIG. 18A  is a flowchart illustrating an example of the procedure of mark generation processing according to the second example embodiment of the present invention; 
         FIG. 18B  is a flowchart illustrating another example of the procedure of the mark generation processing according to the second example embodiment of the present invention; 
         FIG. 19  is a block diagram showing the hardware arrangement of the face recognition apparatus according to the second example embodiment of the present invention; 
         FIG. 20  is a flowchart illustrating the processing procedure of the face recognition apparatus according to the second example embodiment of the present invention; 
         FIG. 21  is a view showing an outline of a display screen according to the third example embodiment of the present invention; 
         FIG. 22  is a block diagram showing the functional arrangement of a display control apparatus according to the third example embodiment of the present invention; 
         FIG. 23  is a table showing the structure of a region connection table according to the third example embodiment of the present invention; 
         FIG. 24  is a flowchart illustrating the procedure of the region connection processing of the display control apparatus according to the third example embodiment of the present invention; 
         FIG. 25  is a view showing an outline of a display screen according to the fourth example embodiment of the present invention; 
         FIG. 26  is a sequence chart showing the operation procedure of a face recognition system according to the fourth example embodiment of the present invention; 
         FIG. 27  is a block diagram showing the functional arrangement of a display control apparatus according to the fourth example embodiment of the present invention; 
         FIG. 28  is a flowchart illustrating the procedure of the display control processing of the display control apparatus according to the fourth example embodiment of the present invention; 
         FIG. 29  is a view showing an outline of a display screen according to the fifth example embodiment of the present invention; 
         FIG. 30  is a sequence chart showing the operation procedure of a face recognition system according to the fifth example embodiment of the present invention; 
         FIG. 31  is a block diagram showing the functional arrangement of a display control apparatus according to the fifth example embodiment of the present invention; 
         FIG. 32  is a flowchart illustrating the procedure of the display control processing of the display control apparatus according to the fifth example embodiment of the present invention; 
         FIG. 33  is a view showing an outline of a display screen according to the sixth example embodiment of the present invention; 
         FIG. 34  is a sequence chart showing the operation procedure of a face recognition system according to the sixth example embodiment of the present invention; 
         FIG. 35  is a block diagram showing the functional arrangement of a display control apparatus according to the sixth example embodiment of the present invention; 
         FIG. 36  is a flowchart illustrating the procedure of the display control processing of the display control apparatus according to the sixth example embodiment of the present invention; 
         FIG. 37  is a block diagram showing the functional arrangement of a face recognition apparatus according to the sixth example embodiment of the present invention; 
         FIG. 38  is a table showing the structure of a face recognition history (learning) database according to the sixth example embodiment of the present invention; 
         FIG. 39  is a table showing the structure of a region-of-interest and region-of-non-interest generation table according to the sixth example embodiment of the present invention; 
         FIG. 40  is a flowchart illustrating the procedure of region-of-interest and/or region-of-non-interest generation processing according to the sixth example embodiment of the present invention; 
         FIG. 41  is a block diagram showing the arrangement of a face recognition system according to the seventh example embodiment of the present invention; 
         FIG. 42A  is a block diagram showing the arrangement of a face recognition system according to the eighth example embodiment of the present invention; 
         FIG. 42B  is a block diagram showing another arrangement of the face recognition system according to the eighth example embodiment of the present invention; and 
         FIG. 43  is a block diagram showing the functional arrangement of a communication terminal as a face recognition system according to the ninth example embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Example embodiments of the present invention will now be described in detail with reference to the drawings. It should be noted that the relative arrangement of the components, the numerical expressions and numerical values set forth in these example embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. 
     First Example Embodiment 
     A display control apparatus  100  according to the first example embodiment of the present invention will be described with reference to  FIG. 1 . The display control apparatus  100  is an apparatus that controls display of a face image to undergo face recognition. 
     As shown in  FIG. 1 , the display control apparatus  100  includes a similarity acquirer  101  and a display controller  102 . The similarity acquirer  101  acquires a similarity between each pair of partial regions of face images by performing collation processing between the each pair of partial regions of the face images. The display controller  102  controls to overlay, on the face images, at least one of the first region the similarity of which exceeds a threshold and the second region the similarity of which does not exceed the threshold, and display the overlaid face images. 
     According to this example embodiment, when the degree of similarity for each pair of partial regions of face images is overlaid and displayed on the face images, the operator can grasp a factor leading a face recognition result at a glance, and thus can confirm or modify the face recognition result on the spot. 
     Second Example Embodiment 
     A face recognition system including a display control apparatus according to the second example embodiment of the present invention will be described next. The display control apparatus according to this example embodiment acquires a similarity derived by performing collation for each pair of partial regions of face images in a face recognition apparatus, and controls to overlay and display, on the face images, marks each indicating whether the acquired similarity exceeds a threshold or not. This allows the user or operator to grasp a factor for a face recognition result at a glance, and confirm or modify the face recognition result on the spot. 
     &lt;&lt;Display Screen of Face Recognition Result&gt;&gt; 
       FIG. 2A  is a view showing an outline of the display screen of a terminal  210  according to this example embodiment. Note that the display screen shown in  FIG. 2A  is not limited, and may be the display screen of a mobile terminal, the display screen of a PC (Personal Computer), or the display screen of an apparatus dedicated for face recognition or surveillance. 
     In the display screen of the terminal  210  shown on the left side of  FIG. 2A , a mark “◯” indicating that the similarity of each pair of partial regions (in  FIG. 2A, 5  (vertical)×5 (horizontal)=25) exceeds a predetermined threshold as a result of comparison is overlaid on a captured face image or recognition target face image  211 . The size of the mark “◯” corresponds to a difference value obtained by subtracting the predetermined threshold from the similarity. That is, a mark “◯”  212  of a large size indicates a partial region whose similarity is much larger than the predetermined threshold. On the other hand, a mark “◯”  213  of a small size indicates a partial region whose similarity is not much larger than the predetermined threshold. In this way, the marks “◯” are overlaid and displayed so as to discriminate between the high and low similarities. Note that in the display screen on the left side, a mark “●” indicates a partial region whose similarity does not exceed the predetermined threshold. From the display screen on the left side, the user or operator can understand at a glance that the peripheral regions of eyes and the central region of a mouth are similar regions. 
     In the display screen of the terminal  210  shown on the right side of  FIG. 2A , a mark “□” indicating that the similarity of each pair of the partial regions (in  FIG. 2A, 5  (vertical)×5 (horizontal)=25) exceeds a predetermined threshold as a result of comparison is overlaid on the captured face image or recognition target face image  211 . The size of the mark “□” corresponds to a difference value obtained by subtracting the predetermined threshold from the similarity. That is, a mark “□”  214  of a large size indicates a partial region whose similarity is much larger than the predetermined threshold. On the other hand, a mark “□”  215  of a small size indicates a partial region whose similarity is not much larger than the predetermined threshold. Note that in the display screen on the right side, a mark “●” indicates a partial region whose similarity does not exceed the predetermined threshold. Similarly to the display screen on the left side, from the display screen on the right side, the user or operator can understand at a glance that the peripheral regions of the eyes and the central region of the mouth are similar regions. 
     Note that  FIG. 2A  shows the marks “O” of large and small sizes and the marks “□” of large and small sizes are shown as marks each indicating the similarity. The shape of the mark is not limited to them shown in  FIG. 2A . The degree of similarity corresponds to the size of the mark but may be represented by the type or chromaticity of the color of the mark, the density of the mark, or the transparency when the mark is overlaid on the face images. 
       FIG. 2B  is a view showing another outline of the display screen of the terminal  210  according to this example embodiment. 
     A captured face image  221  and an accumulated recognition target face image  222  are displayed in the display screen of the terminal  210  shown on the left side of  FIG. 2B . In the accumulated recognition target face image  222 , a similar portion  223  of 5 (vertical)×4 (horizontal)=20 partial regions is filled with a predetermined transparent color (represented by backward diagonal hatching in  FIG. 2B ). On the other hand, a dissimilar portion  224  is not filled. The similar portion indicates a region where the partial region similarity exceeds the predetermined threshold. Note that this overlay and display processing is implemented by overlaying, as similar region marks, frames filled with the transparent color on the partial regions of the face image  222 . 
     A captured face image  231  and an accumulated recognition target face image  232  are displayed in the display screen of the terminal  210  shown on the right side of  FIG. 2B . In the accumulated recognition target face image  232 , a dissimilar portion  233  of 5 (vertical)×4 (horizontal)=20 partial regions is filled with a predetermined transparent color (represented by forward diagonal hatching in  FIG. 2B ). On the other hand, a similar portion  234  is not filled. The dissimilar portion indicates a region where the partial region similarity does not exceed the predetermined threshold. Note that this overlay and display processing is implemented by overlaying, as dissimilar region marks, frames filled with the transparent color on the partial regions of the face image  232 . 
     Note that  FIG. 2B  shows an example in which the similar region marks or dissimilar region marks are overlaid on the accumulated recognition target face image  222  or  232 . However, the similar region marks or dissimilar region marks may be overlaid on the captured face image  221  or  231 . Alternatively, one or both of a similar region mark and a dissimilar region mark may be overlaid on the face images. If both the marks are overlaid, the similar region mark and the dissimilar region mark are displayed to be collated. A face image overlaid and displayed on the screen may be one of the captured face image  221  or  231  and the accumulated recognition target face image  222  or  232 . 
     In  FIGS. 2A and 2B , the captured face image is compared with the accumulated recognition target face image to calculate the similarity. However, a plurality of captured face images or a plurality of accumulated face images may be compared with each other. The mark includes a symbol of a predetermined shape, a colored partial region, or a filled partial region. 
     &lt;&lt;Face Recognition System&gt;&gt; 
     The arrangement and operation of a face recognition system  300  according to this example embodiment will be described with reference to  FIGS. 3 and 4 . 
     (System Arrangement) 
       FIG. 3  is a block diagram showing the arrangement of the face recognition system  300  according to this example embodiment. 
     The face recognition system  300  includes image capturing apparatuses (cameras)  320  to  32   m , terminals  210  to  21   n , a display control apparatus  330 , and a face recognition apparatus  340 , all of which are connected by a network  350 . 
     The image capturing apparatuses (cameras)  320  to  32   m  include surveillance cameras arranged in an airport and the like. The terminals  210  to  21   n  may include the operator terminal  210  for surveillance arranged in an airport or the like, and the note PC  21   i  or a mobile terminal (smartphone, tablet, or the like) as a user terminal. The display control apparatus  330  compares, with a threshold, a similarity as a result of comparison for each pair of partial regions of face images in the face recognition apparatus  340 , and controls display on the terminals  210  to  21   n  by overlaying the result on the face images. The face recognition apparatus  340  extracts a face image from an image captured by one of the image capturing apparatuses (cameras)  320  to  32   m , derives a similarity by comparing each partial region of the extracted face image with a corresponding partial region of a face image read out from an accumulator, and recognizes a face based on the similarities. The face recognition apparatus  340  transmits the face recognition result and the similarities of the pairs of partial regions to the display control apparatus  330 , and also transmits the face recognition result to the terminals  210  to  21   n.    
     Note that the display control apparatus  330  and the face recognition apparatus  340  may be connected by a local network, as indicated by a dashed line. 
     (Operation Sequence) 
       FIG. 4  is a sequence chart showing the operation procedure of the face recognition system  300  according to this example embodiment. Note that in  FIG. 4 , the image capturing apparatuses (cameras)  320  to  32   m  are represented by the camera  320 , and the terminals  210  to  21   n  are represented by the operator terminal  210 . 
     In step S 401 , the face recognition system  300  is initialized. In step S 403 , the camera  320  captures a person and transmits a captured image to the face recognition apparatus  340 . Note that the camera  320  may capture a crowd in the lobby of an airport or on a road instead of a specific person, and the face recognition apparatus  340  or the like extracts each person, and extracts a face image of each person. An arrangement in which an advanced image processor is provided in the camera  320  and only the feature of a face image is transmitted to the face recognition apparatus  340  may be adopted. 
     Upon receiving the captured image from the camera  320 , the face recognition apparatus  340  divides the face image into partial regions in step S 405 . Note that the partial regions may be rectangular regions having different areas in accordance with the importance of face recognition or regions each surrounded by a curve, instead of regions obtained by dividing the image in a grid pattern shown in  FIG. 2A or 2B . Furthermore, the partial regions may be regions respectively including portions such as eyes, a nose, and a mouth extracted from the captured face image but are not limited to them. 
     In step S 407 , the face recognition apparatus  340  calculates a similarity by comparing corresponding partial regions of the captured face image and each face image read out from a face image database in which face images are accumulated. Note that enlargement/reduction processing for associating the partial regions of the face images is also performed. However, the aspect ratio of the face in each of the face images captured at the same angle desirably remains the same. To calculate the similarity between the partial regions, for example, the accumulation of comparison results of luminances, colors, or the like on a pixel basis, the accumulation of the features of regions obtained by subdividing each partial region, or the feature of the luminance or color of each entire partial region or the feature of an edge in each partial region is used. The present invention, however, is not limited to them. For example, an SSD (Sum of Squared Difference), an SAD (Sum of Absolute Difference), a normalized correlation value, or the like may be calculated as the similarity using the arrangement of the luminance values of the respective pixels of each partial region or each of regions obtained by subdividing each partial region. 
     In step S 409 , the face recognition apparatus  340  accumulates the similarity of each pair of partial regions in consideration of a weight, and comparing the accumulated values with a threshold, thereby performing face recognition of determining similarity or dissimilarity. If there exists a similar face, the user is notified of the face as a recognition result. At the same time, in step S 411 , the face recognition apparatus  340  transmits, to the display control apparatus  330 , the face recognition result and the collation result (similarity) of each pair of partial regions of the face images. Note that the operator terminal  210  may be directly notified of the face recognition result. 
     In step S 413 , the display control apparatus  330  compares, with a predetermined threshold, each partial region similarity received from the face recognition apparatus  340 . In step S 415 , the display control apparatus  330  generates an overlaid display image data by overlaying a predetermined mark on the partial region of the face image whose similarity exceeds the predetermined threshold and/or the partial region whose similarity does not exceed the predetermined threshold. In step S 417 , the display control apparatus  330  transmits the overlaid display image data to the operator terminal  210 . 
     In step S 419 , the operator terminal  210  displays an overlaid image received from the display control apparatus  330 . Note that the operator terminal  210  displays the face recognition result (similarity or dissimilarity) by the face recognition apparatus  340  at the same time. In step S 421 , the operator terminal  210  transmits, to the camera  320 , the display control apparatus  330 , and the face recognition apparatus  340 , an operation performed by the operator by viewing the overlay and display. 
     Note that  FIG. 4  shows a case in which the display control apparatus  330  generates an overlaid display image. An image indicating the mark transmitted from the display control apparatus  330  may be overlaid on the face images in the operator terminal  210 . 
     &lt;&lt;Functional Arrangement of Display Control Apparatus&gt;&gt; 
       FIG. 5  is a block diagram showing the functional arrangement of the display control apparatus  330  according to this example embodiment. 
     The display control apparatus  330  includes a communication controller  501 , a face image acquirer  502 , a face image storage  503 , a similarity acquirer  504 , a comparator  505 , and a threshold storage  506 . The display control apparatus  330  further includes a mark generator  507 , a mark storage  508 , an image overlay unit  509 , and an overlaid image transmitter  510 . 
     The communication controller  501  controls communication with the face recognition apparatus  340  or the operator terminal  210  via the network  350 . The face image acquirer  502  acquires a face image having undergone face recognition from the face recognition apparatus  340  via the communication controller  501 . The face image having undergone face recognition includes at least one of a captured face image and an accumulated recognition target face image. 
     The similarity acquirer  504  acquires each partial region similarity in association with a partial region ID (Identifier) from the face recognition apparatus  340 . The comparator  505  compares each partial region similarity with the predetermined threshold, and outputs a comparison result (data indicating whether the similarity exceeds the threshold). The threshold storage  506  stores the threshold to be compared with each partial region similarity in the comparator  505 . As the threshold, one threshold used to determine whether the similarity exceeds the threshold, or two thresholds used to determine whether the similarity exceeds the first threshold or the second threshold (first threshold&gt;one threshold&gt;second threshold) may be stored. Furthermore, various thresholds can be set in accordance with information of which the operator is notified by an overlaid image. 
     The mark generator  507  generates a mark to be overlaid on each partial region of the face image in accordance with the output from the comparator  505 . Note that a mark is generated by selecting, in accordance with the output from the comparator  505 , a mark to be used from the mark storage  508 . The mark storage  508  stores a mark to be overlaid on each partial region of the face image in accordance with the output from the comparator  505 . Note that the mark includes the fill of the partial region. 
     The image overlay unit  509  overlays, on the face images stored in the face image storage unit  503 , the mark generated by the mark generator  507  and indicating whether the similarity exceeds the threshold. The overlaid image transmitter  510  transmits, to the operator terminal  210  via the network  350 , the face image in which the marks are overlaid on the partial regions by the image overlay unit  509 . 
     Note that in  FIG. 5 , the comparator  505 , the threshold storage  506 , the mark generator  507 , the mark storage  508 , the image overlay unit  509 , and the overlaid image transmitter  510  correspond to the display controller  102  shown in  FIG. 1 . 
     (Face Image Storage) 
       FIG. 6  is a table showing the structure of the face image storage  503  according to this example embodiment. The face image storage  503  stores the face image and the face recognition result in the face recognition apparatus  340  for generating an overlaid image with the marks. Note that the structure of the face image storage  503  is not limited to that shown in  FIG. 6 . 
     The face image storage  503  stores a face recognition ID  601  for identifying face recognition processing, a captured image ID  602  for identifying an image captured by the camera  320 , an accumulated image ID  603  for identifying an accumulated image as a recognition target in the face recognition apparatus  340 , and a face recognition result  604  in the face recognition apparatus  340 . The face image storage  503  also stores an overlaying image flag  605  indicating whether a face image to undergo overlay is one or both of a captured image and an accumulated image. 
     (Threshold Storage) 
       FIG. 7  is a table showing the structure of the threshold storage  506  according to this example embodiment. The threshold storage  506  stores a threshold that corresponds to an overlaying mark and is to be compared with the similarity of each pair of partial regions of the face images. Note that the structure of the threshold storage  506  is not limited to that shown in  FIG. 7 . 
     The threshold storage  506  stores a threshold  702  in association with an application  701  of the threshold in comparison with the similarity. In  FIG. 7 , for example, one threshold Th 0  for dividing the partial region based on the similarity, which is used to determine whether the similarity exceeds the threshold, and two thresholds Th 1  (first threshold) and Th 2  (second threshold) for separating the partial region of a high similarity exceeding the first threshold and separating the partial region of a low similarity not exceeding the second threshold are stored. Note that a threshold for separating the similarity may be further provided to finely change the overlaying mark. 
     (Mark Storage) 
       FIG. 8A  is a table showing the structure of the mark storage  508  according to this example embodiment. The mark storage  508  stores various marks to be selected in consideration of the condition of the comparison result between each partial region similarity and the threshold and the condition of the mark indicating the comparison result to the operator. Note that the structure of the mark storage  508  is not limited to that shown in  FIG. 8 . 
     The mark storage  508  stores, in association with a mark ID  811  for identifying a mark, a shape  812  of the mark, basic image data  813  of the mark, and a change  814  corresponding to the similarity. The basic image data  813  stores the size, color, and density as the basis of the mark, image data on a pixel basis, or the like. 
     (Overlaying Image Data Generation Table) 
       FIG. 8B  is a table showing the structure of an overlaying image data generation table  820  according to this example embodiment. The overlaying image data generation table  820  is used in processing up to the mark generator  507  to generate overlaying image data of each partial region. 
     In association with each partial region ID  822  of a display face image ID  821  for identifying a face image on which a mark is overlaid and displayed, the overlaying image data generation table  820  stores a partial region similarity  823 , a comparison result  824  indicating whether or not the threshold is exceeded, a mark ID  825  for indicating the comparison result  824 , and a level  826  corresponding to the comparison result  824 , for example, (similarity-threshold) or (threshold-similarity). The overlaying image data generation table  820  stores overlaying image data  827  to be overlaid on each partial region. 
     (Overlaid Display Data Generation Table) 
       FIG. 9  is a table showing the structure of an overlaid display data generation table  900  according to this example embodiment. The overlaid display data generation table  900  is used in the processing of the image overlay unit  509  to generate display image data by overlaying the overlaying image data of each partial region on each partial region of the face image. 
     The overlaid display data generation table  900  stores face image data  902  in association with the display face image ID  821 . The overlaid display data generation table  900  stores the overlaying image data  827  of each partial region generated by the mark generator  507  and overlaid result data  904  of each partial region. In addition, the overlaid display data generation table  900  stores display image data  905  obtained by setting the overlaid result data  904  of the respective partial regions as the entire face image. 
     Note that in  FIG. 9 , an overlaying image is generated for each partial region. However, overlaying image data may be generated by individually collecting the marks, and the display face image data and the overlaying image data may be collectively overlaid. 
     &lt;&lt;Functional Arrangement of Face Recognition Apparatus&gt;&gt; 
       FIG. 10  is a block diagram showing the functional arrangement of the face recognition apparatus  340  according to this example embodiment. 
     The face recognition apparatus  340  includes a communication controller  1001 , a captured image acquirer  1002 , a face image extractor  1003 , a captured face image database  1004 , a collation target face image database  1005 , and a partial region database  1006 . The face recognition apparatus  340  includes a partial region generator  1007 , a partial region similarity calculator  1008 , a face recognizer  1009 , a face recognition result and similarity transmitter  1010 , and an operator&#39;s operation acquirer  1011 . 
     The communication controller  1001  controls communication with the image capturing apparatus (camera)  320 , the operator terminal  210 , and the display control apparatus  330  via the network  350 . The captured image acquirer  1002  acquires a captured image from the image capturing apparatus (camera)  320  via the communication controller  1001 . The face image extractor  1003  extracts a face image from the captured image acquired by the captured image acquirer  1002 . Note that if the image capturing apparatus (camera)  320  transmits a face image or the feature of the face image, the face image extractor  1003  is unnecessary. The captured face image database  1004  accumulates the captured face image to be searchable. 
     The collation target face image database  1005  accumulates a reference face image to undergo collation for recognition of the captured face image to be searchable. In this example embodiment, the partial region database  1006  stores a partial region, for which the similarity is calculated by collation, to be searchable. Note that the partial region database  1006  may store not only data for a partial region but also an algorithm of generating a partial region. 
     The partial region generator  1007  generates partial regions of the captured face image found from the captured face image database  1004  and the captured face image found from the collation target face image database  1005  based on the defined partial region selected from the partial region database  1006 . The partial region similarity calculator  1008  associates the partial regions of the captured image and those of the collation target face image, which have been generated by the partial region generator  1007 , and compares them, thereby calculating the similarity of each pair of partial regions. The face recognizer  1009  includes a face recognition table  1091 , and recognizes whether the face images are similar based on the pattern or the accumulation of the similarities of the pairs of partial regions calculated by the partial region similarity calculator  1008 . 
     The face recognition result and similarity transmitter  1010  transmits, to the display control apparatus  330  via the communication controller  1001 , the face recognition result indicating whether the faces are similar, which has been output from the face recognizer  1009 , and the similarities of the pairs of partial regions output from the partial region similarity calculator  1008 . Note that the face recognition result may be directly sent to the operator terminal  210 . The operator&#39;s operation acquirer  1011  receives an operator operation from the operator terminal  210  via the communication controller  1001 , and executes processing corresponding to the operator operation. 
     Note that the face recognition apparatus  340  shown in  FIG. 10  performs face recognition based on the captured face image and the collation target face image. However, if both the face images are captured face images or collation target face images, the face images are read out from the same database. 
     (Captured Face Image Database) 
       FIG. 11A  is a table showing the structure of the captured face image database  1004  according to this example embodiment. Note that the structure of the captured face image database  1004  is not limited to that shown in  FIG. 11A . 
     In association with a captured face image ID  1111  for identifying a captured face image, the captured face image database  1004  stores an image capturing apparatus ID  1112  for identifying an image capturing apparatus, an image capturing date and time  1113 , captured face image data  1114 , and a feature  1115  of the face image data. 
     (Collation Target Face Image Database) 
       FIG. 11B  is a table showing the structure of the collation target face image database  1005  according to this example embodiment. Note that the structure of the collation target face image database  1005  is not limited to that shown in  FIG. 11B . 
     In association with a target face image ID  1121  for identifying a target face image to be collated, the collation target face image database  1005  stores face image attributes  1122  added to the face image, person attributes  1123  added to the person of the face image, face image data  1124 , and a feature  1125  of the face image data. The face image attributes  1122  store the acquisition date and time of the face image, the acquisition location of the face image, and the like. The person attributes  1123  store the name, age, sex, address, and the like of the person. 
     (Partial Region Database) 
       FIG. 12  is a table showing the structure of the partial region database  1006  according to this example embodiment. Note that the structure of the partial region database  1006  is not limited to that shown in  FIG. 12 . 
     The partial region database  1006  stores a partial region generation algorithm  1202  in association with a partial region ID  1201  for identifying a partial region obtained by dividing the face image. For example, as the partial region generation algorithm  1202 , the size of mesh division of the face image, that is, H (vertical)×W (horizontal), regions respectively including feature portions such as eyes, a nose, and mouth, a mixture of a feature portion and a mesh (a smaller size of h (vertical)×w (horizontal)), a mixture of a mesh (a size of H (vertical)×W (horizontal)) and a mesh (a smaller size of h (vertical)×w (horizontal)), and the like are shown. 
     However, the algorithm is not limited to those shown in  FIG. 12 . For example, a fine region is set as an important region for face recognition and a coarse region is set as an unimportant region, or vice versa. The partial region generation algorithm  1202  can be changed in accordance with a method (similarity calculation method) of performing collating each pair of partial regions. The following partial region generation method is also included. ⋅A region is generated as a mesh by a polygon such as a triangle or hexagon, or a closed curve such as a circle, instead of a rectangle. ⋅Regions in which two or more regions overlap each other are generated. ⋅Partial regions are generated based on an operator operation. 
     (Face Recognition Table) 
       FIG. 13  is a table showing the structure of the face recognition table  1091  according to this example embodiment. The face recognition table  1091  is used to perform face recognition based on the similarities of the pairs of partial regions in the face recognizer  1009 . 
     The face recognition table  1091  stores a similarity score  1303  obtained by assigning a score to the similarity of each pair of partial regions and a total score  1304  in association with a captured face image ID  1301  for identifying a captured face image and a collation target face image ID  1302  for identifying a collation target face image. The face recognition table  1091  also stores a comparison result  1305  between the total score  1304  and a face similarity threshold stored in advance, and a face recognition result  1306  of similarity or dissimilarity corresponding to the comparison result  1305 . Note that the total score  1304  may be calculated by giving a region weight to the similarity score  1303  of the pair of partial regions. The face similarity threshold is preferably set in accordance with the partial region division method, the similarity calculation method, and the scoring method. 
     &lt;&lt;Functional Arrangement of Operator Terminal&gt;&gt; 
       FIG. 14  is a block diagram showing the functional arrangement of the operator terminal  210  according to this example embodiment. 
     The operator terminal  210  includes a communication controller  1401 , a display image receiver  1402 , a display unit  1403 , an operation unit  1404 , and an operator&#39;s operation transmitter  1405 . If the image capturing apparatus (camera)  320  is locally connected to the operator terminal  210 , the operator terminal  210  includes a captured image acquirer  1406  and a captured image transmitter  1407 . 
     The communication controller  1401  controls communication with the image capturing apparatus (camera)  320 , the face recognition apparatus  340 , and the display control apparatus  330  via the network  350 . The display image receiver  1402  receives, via the communication controller  1401 , normal image data, overlaying image data, image data to be overlaid, or the like to be displayed on the display unit  1403 . For example, a captured image is received from the image capturing apparatus (camera)  320 . A notification image of a face recognition result is received from the face recognition apparatus  340 . Image data obtained by overlaying, on each partial region of the face image, a mark indicating a result of comparison with the similarity threshold is received from the display control apparatus  330 . The display unit  1403  displays the image received by the display image receiver  1402 . 
     The operation unit  1404  includes an operation processing table  1441 , and determines operation contents input by the operator from a touch panel or the like. Note that in the case of the touch panel, the operation contents are also associated with the display contents of the display unit  1403 . The operator&#39;s operation transmitter  1405  transmits, via the communication controller  1401 , the operation contents by the operator to the respective apparatuses that implement the operation. The captured image acquirer  1406  acquires a captured image from the locally connected image capturing apparatus (camera)  320 . The captured image transmitter  1407  transmits the captured image to the face recognition apparatus  340  via the communication controller  1401 . Note that a communication terminal incorporating a camera, such as a smartphone or tablet, includes the captured image acquirer  1406  and the captured image transmitter  1407 . 
     (Operation Processing Table) 
       FIG. 15  is a table showing the structure of the operation processing table  1441  according to this example embodiment. The operation processing table  1441  is used to determine an operation input from the operator to, for example, a touch panel, and convert the operation input into an appropriate operation instruction. 
     The operation processing table  1441  stores operation contents  1503  in association with an operation position (coordinates)  1501  on the touch panel serving as the operation unit  1404  and an operation type  1502  of the operator (especially, a finger). Note that practical examples of the operation action and operation contents by the operator will be omitted. 
     &lt;&lt;Hardware Arrangement of Display Control Apparatus&gt;&gt; 
       FIG. 16  is a block diagram showing the hardware arrangement of the display control apparatus  330  according to this example embodiment. 
     Referring to  FIG. 16 , a CPU (Central Processing Unit)  1610  is an arithmetic control processor, and implements the functional components shown in  FIG. 5  by executing a program. A ROM (Read Only Memory)  1620  stores permanent data such as initial data and a program, and programs. The communication controller  501  controls communication with the face recognition apparatus  340 , the operator terminal  210 , and other apparatuses via the network  350 . 
     A RAM (Random Access Memory)  1640  is a random access memory used as a temporary storage work area by the CPU  1610 . An area to store data necessary for implementation of the example embodiment is allocated to the RAM  1640 . A similarity  1641  serves as an area to store the similarity of each pair of partial regions received from the face recognition apparatus  340 . A threshold  1642  serves as an area to store a threshold to be compared with the similarity  1641 . A determination result  1643  serves as an area to store a result of comparing the similarity  1641  of each pair of partial regions with the threshold  1642 . A generated mark  1644  serves as an area to store a mark corresponding to the determination result  1643 , with which the similarity can be recognized at a glance. A face image  1645  serves as an area to store a face image on which the generated mark  1644  is overlaid. The overlaid display data generation table  900  serves as an area to store a table for generating overlaid display data, as shown in  FIG. 9 . Transmission/reception data  1646  serves as an area to store data transmitted/received via the communication controller  501 . 
     A storage  1650  stores a database, various parameters, or the following data or programs necessary for implementation of the example embodiment. As shown in  FIG. 6 , the face image storage  503  stores a face image in which a mark is overlaid on each partial region. As shown in  FIG. 7 , the threshold storage  506  stores a threshold to be compared with the similarity of each pair of partial regions. As shown in  FIG. 8A , the mark storage  508  stores a mark to be overlaid, in accordance with a result of comparing the similarity of each pair of partial regions with the threshold. The storage  1650  stores the following programs. A display control apparatus control program  1651  is a program for controlling the overall display control apparatus  330 . A similarity determination module  1652  is a module for generating a determination result by comparing the similarity of each pair of partial regions with the threshold. A mark generation module  1653  is a module for generating a mark corresponding to the determination result of the similarity determination module  1652  with reference to the mark storage  508 . An overlaid image generation module  1654  is a module for generating overlaid display data by overlaying the generated mark  1644  on the face image  1645  and controlling display in the operator terminal  210 . 
     Note that programs and data which are associated with the general-purpose functions of the display control apparatus  330  and other feasible functions are not shown in the RAM  1640  or the storage  1650  of  FIG. 16 . 
     &lt;&lt;Processing Procedure of Display Control Apparatus&gt;&gt; 
       FIG. 17  is a flowchart illustrating the processing procedure of the display control apparatus  330  according to this example embodiment. This flowchart is executed by the CPU  1610  of  FIG. 16  using the RAM  1640 , thereby implementing the functional components of  FIG. 5 . 
     In step S 1701 , the display control apparatus  330  receives face images, and stores them in the face image storage  503 . In step S 1703 , the display control apparatus  330  acquires the similarity of each pair of partial regions of the face images from the face recognition apparatus  340 . In step S 1705 , the display control apparatus  330  executes mark generation processing of generating a corresponding mark by comparing the similarity of each pair of partial regions with the threshold. 
     After generating the mark corresponding to each pair of partial regions, the display control apparatus  330  determines in step S 1707  based on an operator operation in the operator terminal  210  whether the mark is to be overlaid and displayed. If the operator instructs to display the mark, the display control apparatus  330  overlays, in step S 1709 , the mark corresponding to the similarity on the partial region of the face image. 
     In step S 1711 , the display control apparatus  330  determines whether the all partial regions have been processed. If the all partial regions have not been processed, the display control apparatus  330  returns to step S 1703  to acquire the similarity of each of the remaining pairs of partial regions, and repeats the processes up to step S 1709 ; otherwise, the display control apparatus  330  executes, in step S 1713 , display control processing so that the face image on which the marks are overlaid is displayed on the display unit  1403  of the operator terminal  210 . 
     (Mark Generation Processing: Threshold) 
       FIG. 18A  is a flowchart illustrating an example of the procedure of the mark generation processing (S 1705 ) according to this example embodiment.  FIG. 18A  shows an example in which corresponding marks are generated using one threshold when the similarity of the pair of partial regions exceeds the threshold and when the similarity of the pair of partial regions does not exceed the threshold. 
     In step S 1811 , the display control apparatus  330  determines whether the similarity of each pair of partial regions exceeds the threshold Th 0 . If the similarity exceeds the threshold Th 0 , the display control apparatus  330  generates, in step S 1813 , a mark indicating that the partial regions are similar regions whose similarity exceeds the threshold Th 0  so as to represent the similarity level. On the other hand, if the similarity does not exceed the threshold Th 0 , the display control apparatus  330  generates, in step S 1815 , a mark indicating that the partial regions are dissimilar regions whose similarity does not exceed the threshold Th 0  so as to represent the similarity level. 
     Note that if the mark is overlaid only when the threshold is or is not exceeded, one of steps S 1813  and S 1815  is necessary. Alternatively, both the marks may be generated and one of the marks may be selected to be overlaid at the time of overlaying. 
     (Mark Generation Processing: First and Second Thresholds) 
       FIG. 18B  is a flowchart illustrating another example of the procedure (S 1705 ) of the mark generation processing according to this example embodiment.  FIG. 18B  shows an example in which corresponding marks are generated using the two thresholds when the similarity of the pair of partial regions exceeds the higher threshold and when the similarity of the pair of partial regions is smaller than the lower threshold. 
     In step S 1821 , the display control apparatus  330  determines whether the similarity of each pair of partial regions exceeds the threshold Th 1  (&gt;Th 0 ). If the similarity exceeds the threshold Th 1 , the display control apparatus  330  generates, in step S 1823 , a mark indicating that the partial regions are similar regions whose similarity exceeds the threshold Th 1  so as to represent the similarity level. On the other hand, the display control apparatus  330  determines in step S 1825  whether the similarity of each pair of partial regions is smaller than the threshold Th 2  (&lt;Th 0 ). If the similarity is smaller than the threshold Th 2  (&lt;Th 0 ), the display control apparatus  330  generates, in step S 1827 , a mark indicating that the partial regions are dissimilar regions whose similarity is smaller than the threshold Th 2  so as to represent the similarity level. 
     Note that if the mark is overlaid only when the threshold is or is not exceeded, only steps S 1821  and S 1823  or steps S 1825  and S 1827  are necessary. Alternatively both the marks may be generated and one of the marks may be selected to be overlaid at the time of overlaying. 
     &lt;&lt;Hardware Arrangement of Face Recognition Apparatus&gt;&gt; 
       FIG. 19  is a block diagram showing the hardware arrangement of the face recognition apparatus  340  according to this example embodiment. 
     Referring to  FIG. 19 , a CPU  1910  is an arithmetic control processor, and implements the functional components shown in  FIG. 5  by executing a program. A ROM  1920  stores permanent data such as initial data and a program, and programs. The communication controller  1001  controls communication with the display control apparatus  330 , the operator terminal  210 , and other apparatuses via the network  350 . 
     A RAM  1940  is a random access memory used as a temporary storage work area by the CPU  1910 . An area to store data necessary for implementation of the example embodiment is allocated to the RAM  1940 . A captured face image and partial region image  1941  serve as areas to store a captured face image and its partial region images. A collation target face image and partial region image  1942  serve as areas to store an accumulated collation target face image and its partial region images. A partial region similarity  1943  serves as an area to store a similarity as a result of collating the corresponding partial regions of the captured face image and collation target image. The face recognition table  1091  serves as an area to store a table for performing face recognition based on the similarities of the pairs of partial regions, as shown in  FIG. 13 . A face recognition result  1944  serves as an area to store a result of performing face recognition using the face recognition table  1091 . Transmission/reception data  1945  serves as an area to store data transmitted/received to/from the display control apparatus  330 , the operator terminal  210 , and the image capturing apparatus (camera)  320  via the communication controller  1001 . 
     A storage  1950  stores a database, various parameters, or the following data or programs necessary for implementation of the example embodiment. As shown in  FIG. 11B , the collation target face image database  1005  is a database for accumulating collation target images. As shown in  FIG. 11A , the captured face image database  1004  is a database for storing face images captured by the image capturing apparatus (camera)  320 . As shown in  FIG. 12 , the partial region database  1006  is a database for defining a partial region appropriate for collation of the face images. A similarity calculation algorithm  1951  stores an algorithm for calculating the similarity of each pair of partial regions of the face images. A face recognition algorithm  1952  stores an algorithm for performing face recognition based on the similarities of the pairs of partial regions. The storage  1950  stores the following programs. A face recognition apparatus control program  1953  is a program for controlling the overall face recognition apparatus  340 . A partial region collation module  1954  is a module for performing comparison and collation to generate partial regions of the captured face image and collation target face image and generate the similarity of each pair of partial regions. A face recognition module  1955  is a module for recognizing the face image based on the similarities of the pairs of partial regions. A face recognition result and similarity output module  1956  is a module for outputting, to the display control apparatus  330  or the operator terminal  210 , the face recognition result as an output from the face recognition module  1955  and the similarities of the pairs of partial regions as an output from the partial region collation module  1954 . 
     Note that programs and data which are associated with the general-purpose functions of the face recognition apparatus  340  and other feasible functions are not shown in the RAM  1940  or the storage  1950  of  FIG. 19 . 
     &lt;&lt;Processing Procedure of Face Recognition Apparatus&gt;&gt; 
       FIG. 20  is a flowchart illustrating the processing procedure of the face recognition apparatus  340  according to this example embodiment. This flowchart is executed by the CPU  1910  of  FIG. 19  using the RAM  1940 , thereby implementing the functional components of  FIG. 10 . 
     In step S 2001 , the face recognition apparatus  340  receives a captured face image from the image capturing apparatus (camera)  320 . Alternatively, the face recognition apparatus  340  receives a captured image and extracts a face image. In step S 2003 , the face recognition apparatus  340  acquires a collation target face image from the collation target face image database  1005 . Note that acquisition of the collation target face image may be implemented by sequentially reading out the images without any algorithm, but it is desirable to read out a collation target face image within a selected range in accordance with the feature of the captured image or an instruction from the operator, and perform collation. 
     In step S 2005 , the face recognition apparatus  340  divides each of the captured face image and the collation target face image into identical partial regions, and calculates the similarity of each pair of partial regions. In step S 2007 , the face recognition apparatus  340  performs face recognition processing based on the similarities of the pairs of partial regions. In step S 2009 , the face recognition apparatus  340  outputs a face recognition result and the similarities of the pairs of partial regions to the display control apparatus  330  or the operator terminal  210 . 
     According to this example embodiment, by controlling to overlay and display, on a face image, marks each indicating whether the similarity exceeds the threshold or not, the operator can grasp a factor for a face recognition result at a glance, and confirm or modify the face recognition result on the spot. 
     Third Example Embodiment 
     A face recognition system including a display control apparatus according to the third example embodiment of the present invention will be described next. The display control apparatus according to this example embodiment is different from that according to the second example embodiment in that a new connected region is generated by connecting adjacent partial regions having similarities falling within a predetermined range, and overlaid and displayed on a face image. The remaining components and operations are the same as those in the second example embodiment. Hence, the same reference numerals denote the same components and operations, and a detailed description thereof will be omitted. 
     &lt;&lt;Display Screen of Face Recognition Result&gt;&gt; 
       FIG. 21  is a view showing an outline of the display screen of a terminal  210  according to this example embodiment. The display screen shown in  FIG. 21  is not limited, and may be the display screen of a mobile terminal, the display screen of a PC, or an apparatus dedicated for face recognition or surveillance. Note that in  FIG. 21 , the same reference numerals as those in  FIG. 2A  denote the same components and a repetitive description thereof will be omitted. 
     The display screen of the terminal  210  shown at the left end of  FIG. 21  is the same as that shown on the left side of  FIG. 2A . Display screens shown at the center and right end on the upper side of  FIG. 21  are obtained by connecting similar regions whose partial region similarities exceed a threshold in the display screen at the left end to more readily recognize the similar regions. On the other hand, display screens shown at the center and right end on the lower side of  FIG. 21  are obtained by connecting dissimilar regions whose partial region similarities do not exceed the threshold in the display screen at the left end to more readily recognize the dissimilar regions. 
     The display screen of the terminal  210  shown at the center on the upper side of  FIG. 21  displays regions  2122  to  2124  obtained by connecting regions where marks “◯”  212  of a large size or marks “◯”  213  of a small size are adjacent to each other in the display screen at the left end. The display screen of the terminal  210  shown at the right end on the upper side of  FIG. 21  displays regions  2132  to  2134  obtained by further connecting the regions  2122  to  2124  in the display screen at the center on the upper side. On the upper side of  FIG. 21 , similar regions whose similarities exceed the threshold are combined (connected) based on a result of collating the similarities of the pairs of subdivided partial regions of the face images with the threshold, thereby changing the partial regions to the similar regions divided more coarsely. 
     The display screen of the terminal  210  shown at the center on the lower side of  FIG. 21  displays regions  2142  to  2144  obtained by connecting regions where marks “●” are adjacent to each other in the display screen at the left end. The display screen of the terminal  210  shown at the right end on the lower side of  FIG. 21  displays regions  2152  to  2154  obtained by further connecting the regions  2142  to  2144  in the display screen at the center on the lower side. On the lower side of  FIG. 21 , dissimilar regions are combined (connected) based on a result of collating the similarities of the pairs of subdivided partial regions of the face images with the threshold, thereby changing the partial regions to the dissimilar regions divided more coarsely. 
     Note that the similar regions or dissimilar regions are connected by processing of connecting adjacent similar regions or adjacent dissimilar regions, by processing of changing the threshold and connecting remaining portions as similar regions or dissimilar regions, or by changing the initial size (corresponding to the division number) of the partial regions.  FIG. 21  shows only three stages. However, partial regions of multiple stages can be implemented and the number of stages at which the operator recognizes a similarity factor more easily when referring to the face images can be selected. Since an appropriate number of stages is influenced by the size of the display screen, the size and density of the face image, the shape of the overlaying mark, and the like, the operator may select the number of stages. 
     &lt;&lt;Functional Arrangement of Display Control Apparatus&gt;&gt; 
       FIG. 22  is a block diagram showing the functional arrangement of a display control apparatus  2230  according to this example embodiment. Note that in  FIG. 22 , the same reference numerals as those in  FIG. 5  denote the same functional components and a repetitive description thereof will be omitted. 
     A partial region connector  2211  includes a region connection table  2212 , and connects adjacent similar regions or adjacent dissimilar regions based on a comparison result indicating similar regions or dissimilar regions as an output from a comparator  505 , and causes a mark generator  507  to generate a larger mark indicating a connected region. 
     Note that as described with reference to  FIG. 21 , if the initial size (corresponding to the division number) of the partial regions is gradually changed, a face recognition apparatus  340  in the face recognition system according to this example embodiment changes the size (corresponding to the division number) of the partial regions. However, an apparatus or system in which a display control apparatus  330  and the face recognition apparatus  340  are integrated can uniformly, gradually change the size (corresponding to the division number) of the partial regions. 
     (Region Connection Table) 
       FIG. 23  is a table showing the structure of the region connection table  2212  according to this example embodiment. The region connection table  2212  is used by the partial region connector  2211  to connect similar regions or dissimilar regions and by the mark generator  507  to generate a connection mark corresponding to a new connected region. 
     In association with a partial region ID  2301  for identifying a partial region, the region connection table  2212  stores a similarity condition  2302  for connection, a position condition  2303  for connection, and a result  2304  of whether or not to connect regions. The region connection table  2212  also stores connected region coordinates  2305  of the connected region on the face image after connecting the partial regions, and a connection mark  2306  to be overlaid on the connected region of the face image. Note that as for the connected region coordinates  2305  and the connection mark  2306 , the same coordinates and connection mark are assigned to connected partial regions  2310 . 
     &lt;&lt;Region Connection Processing Procedure&gt;&gt; 
       FIG. 24  is a flowchart illustrating the procedure of the region connection processing of the display control apparatus  2230  according to this example embodiment. This flowchart is executed by a CPU  1610  of  FIG. 16  using a RAM  1640 , thereby implementing the functional components of  FIG. 22 . Note that processing of overlaying the mark of the similarity on the face images is similar to the processing procedure shown in  FIG. 17  and a description thereof will be omitted. 
     In step S 2401 , the display control apparatus  2230  sets a similarity range to connect partial regions. In step S 2403 , the display control apparatus  2230  extracts partial regions within the set similarity range. In step S 2405 , the display control apparatus  2230  selects adjacent partial regions from the extracted partial regions within the similarity range. If there are adjacent partial regions, the display control apparatus  2230  connects, in step S 2407 , the adjacent partial regions within the set similarity range. 
     In step S 2409 , the display control apparatus  2230  determines whether all the partial regions extracted in step S 2403  have been processed. Steps S 2405  to S 2409  are repeated until all the partial regions are processed. If the processing of all the extracted partial regions ends, the display control apparatus  2230  generates, in step S 2411 , a mark corresponding to the larger connected region generated by connecting the partial regions. In step S 2413 , the display control apparatus  2230  overlays the connection mark indicating the connected region of the face image, and controls display on the operator terminal  210 . 
     Note that the connection mark may also represent the similarity level by changing the shape, color, density, transparency, or the like. 
     According to this example embodiment, since a new connected region is generated by connecting adjacent partial regions having similarities falling within the predetermined range, and overlaid and displayed on a face image, the operator can readily grasp a factor for a face recognition result, and confirm or modify the face recognition result on the spot. 
     Fourth Example Embodiment 
     A face recognition system including a display control apparatus according to the fourth example embodiment of the present invention will be described next. The display control apparatus according to this example embodiment is different from those according to the second and third example embodiments in that partial regions as a factor for erroneous face recognition are generated, and overlaid and displayed on face images. The remaining components and operations are the same as those in the second and third example embodiments. Hence, the same reference numerals denote the same components and operations, and a detailed description thereof will be omitted. 
     &lt;&lt;Display Screen of Face Recognition Result&gt;&gt; 
       FIG. 25  is a view showing an outline of the display screen of a terminal  210  according to this example embodiment. The display screen shown in  FIG. 25  is not limited, and may be the display screen of a mobile terminal, the display screen of a PC, or an apparatus dedicated for face recognition or surveillance. Note that in  FIG. 25 , the same reference numerals as those in  FIG. 2A  denote the same components and a repetitive description thereof will be omitted. 
     The display screen of the terminal  210  shown on the upper side of  FIG. 25  displays a captured face image  2510  and a collation target face image  2520  which have been determined by a face recognition apparatus  340  to be dissimilar, as denoted by reference numerals  2511  and  2521 . However, the face images are actually identical except that the person wears glasses in the collation target face image  2520 . If the face recognition apparatus  340  erroneously recognizes that the face images are dissimilar, the display control apparatus according to this example embodiment determines specific partial regions or connected regions as a factor to determine that the face images are dissimilar to cause erroneous recognition, in response to re-recognition by the face recognition apparatus  340  or indication by the operator from the operator terminal  210 . The display control apparatus according to this example embodiment notifies the operator that partial regions or connected regions  2512  and  2522  cause erroneous recognition. 
     The display screen of the terminal  210  on the lower side of  FIG. 25  displays a captured face image  2530  and a collation target face image  2540 , which have been determined by the face recognition apparatus  340  to be similar, as denoted by reference numerals  2531  and  2541 . However, the captured face image  2530  includes a male and the collation target face image  2540  includes a female, and thus the face images are actually different. If the face recognition apparatus  340  erroneously recognizes that the face images are similar, the display control apparatus according to this example embodiment determines specific partial regions or connected regions as a factor for determining that the face images are similar to cause erroneous recognition, in response to re-recognition by the face recognition apparatus  340  or indication by the operator from the operator terminal  210 . The display control apparatus according to this example embodiment notifies the operator that the similarity of the same pairs of glasses in partial regions or connected regions  2532  or  2542  causes erroneous recognition. 
     Note that  FIG. 25  shows the rectangular partial regions or connected regions. However, regions indicating a factor for erroneous recognition are not limited to the rectangular shape or the number of regions on each face image is not necessarily one. 
     &lt;&lt;Face Recognition System&gt;&gt; 
       FIG. 26  is a sequence chart showing the operation procedure of the face recognition system according to this example embodiment. Note that in  FIG. 26 , the same step numbers as those in  FIG. 4  denote the same steps and a repetitive description thereof will be omitted. 
     After performing overlay and display according to  FIG. 4  in steps S 401  to S 419 , if the operator notices erroneous recognition by the face recognition apparatus  340 , he/she instructs the operator terminal  210  to display a factor for erroneous recognition. In step S 2621 , the operator terminal  210  requests a display control apparatus  2630  according to this example embodiment to display a factor for erroneous recognition. 
     If faces are erroneously recognized to be dissimilar, the display control apparatus  2630  generates, in step S 2623 , overlaid image data by overlaying a mark on each of low similar regions. On the other hand, if the faces are erroneously recognized to be similar, the display control apparatus  2630  generates, in step S 2625 , overlaid image data by overlaying a mark on each of high similar regions. In step S 2627 , the display control apparatus  2630  transmits, to the operator terminal  210 , overlaid images respectively indicating the regions as an erroneous recognition factor. In step S 2629 , the operator terminal  210  notifies the operator of the regions as the erroneous recognition factor by displaying the overlaid images, as shown in  FIG. 25 . 
     &lt;&lt;Functional Arrangement of Display Control Apparatus&gt;&gt; 
       FIG. 27  is a block diagram showing the functional arrangement of the display control apparatus  2630  according to this example embodiment. Note that in  FIG. 27 , the same reference numerals as those in  FIG. 5 or 22  denote the same functional components and a repetitive description thereof will be omitted. 
     An erroneous recognition region selector  2714  receives an instruction to display the regions as the erroneous recognition factor from the operator terminal  210  and the recognition result of the face recognition apparatus  340 , and selects, if the face images are erroneously recognized to be similar based on a result of comparing the similarity of each pair of partial regions with a threshold by a comparator  505 , regions having particularly high similarities. On the other hand, if the face images are erroneously recognized to be dissimilar, the erroneous recognition region selector  2714  selects regions having particularly low similarities. Then, the erroneous recognition region selector  2714  causes a partial region connector  2211  to generate a connected region of the selected partial regions. 
     &lt;&lt;Display Control Processing Procedure&gt;&gt; 
       FIG. 28  is a flowchart illustrating the procedure of the display control processing of the display control apparatus  2630  according to this example embodiment. This flowchart is executed by a CPU  1610  of  FIG. 16  using a RAM  1640 , thereby implementing the functional components of  FIG. 27 . Note that processing of overlaying the mark of the similarity on the face images is similar to the processing procedure shown in  FIG. 17  and a description thereof will be omitted. 
     In step S 2801 , the display control apparatus  2630  determines whether the operator terminal  210  has instructed to display the regions as the erroneous recognition factor. If an instruction to display the regions as the erroneous recognition factor has been sent, the display control apparatus  2630  acquires the recognition result of the face recognition apparatus  340  in step S 2803 . 
     In step S 2805 , the display control apparatus  2630  determines whether the acquired face recognition result indicates “similar”. If the face recognition result indicates “similar”, in step S 2807  the display control apparatus  2630  generates a connected region of partial regions that have particularly high similarities and have influenced the face recognition result indicating “similar”, and generates a mark indicating the connected region as the erroneous recognition factor. If the face recognition result indicates no “similar”, the display control apparatus  2630  determines in step S 2809  whether the acquired face recognition result indicates “dissimilar”. If the face recognition result indicates “dissimilar”, in step S 2811  the display control apparatus  2630  generates a connected region of partial regions that have particularly low similarities and have influenced the face recognition result indicating “dissimilar”, and generates a mark indicating the connected region as the erroneous recognition factor. 
     In step S 2813 , the display control apparatus  2630  overlays the generated mark on each face image, and controls display of the overlaid images on the operator terminal  210 , as shown in  FIG. 25 . 
     According to this example embodiment, since partial regions as a factor for erroneous face recognition are generated, and overlaid and displayed on face images, the operator can readily grasp a factor for erroneous face recognition, and confirm or modify the face recognition result on the spot. 
     Fifth Example Embodiment 
     A face recognition system including a display control apparatus according to the fifth example embodiment of the present invention will be described next. The display control apparatus according to this example embodiment is different from those according to the second to fourth example embodiments in that partial regions as a factor for recognizing that faces are similar are generated, and overlaid and displayed on face images. The remaining components and operations are the same as those in the second to fourth example embodiments. Hence, the same reference numerals denote the same components and operations, and a detailed description thereof will be omitted. 
     &lt;&lt;Display Screen of Face Recognition Result&gt;&gt; 
       FIG. 29  is a view showing an outline of the display screen of a terminal  210  according to this example embodiment. The display screen shown in  FIG. 29  is not limited, and may be the display screen of a mobile terminal, the display screen of a PC, or an apparatus dedicated for face recognition or surveillance. Note that in  FIG. 29 , the same reference numerals as those in  FIG. 2A  denote the same components and a repetitive description thereof will be omitted. 
     The display screen of the terminal  210  on the upper side of  FIG. 29  displays a captured face image  2910  and a collation target face image  2920 , which have been determined by a face recognition apparatus  340  as similar faces  2911 . The display screen on the upper side of  FIG. 29  displays face images of a parent and child. Note that both the images may be captured face images or collation target face images. If the face recognition apparatus  340  recognizes the images as the similar faces  2911 , when the operator or user inquires about similar portions from the operator terminal  210  or the mobile terminal, the operator or user is notified of particularly similar portions by overlaying and displaying, on the face images, partial regions or connected regions  2912  and  2922  as a main factor for recognizing the images as the similar faces  2911 . 
     The display screen of the terminal  210  on the lower side of  FIG. 29  displays a captured face image  2930  and a collation target face image  2940 , which have been determined by the face recognition apparatus  340  as similar faces  2931 . The display screen on the lower side of  FIG. 29  displays a face image of a celebrity on the right side. Note that both the images may be captured face images or collation target face images. If the face recognition apparatus  340  recognizes the images as the similar faces  2931 , when the operator or user inquires about similar portions from the operator terminal  210  or the mobile terminal, the operator or user is notified of particularly similar portions by overlaying and displaying, on the face images, partial regions or connected regions  2932  and  2942  as a main factor for recognizing the images as the similar faces  2931 . 
     Note that  FIG. 29  shows the rectangular partial regions or connected regions. However, regions indicating a factor for the recognition result indicating similar faces are not limited to the rectangular shape or the number of regions on each face image is not necessarily one. 
     &lt;&lt;Face Recognition System&gt;&gt; 
       FIG. 30  is a sequence chart showing the operation procedure of the face recognition system according to this example embodiment. Note that in  FIG. 30 , the same step numbers as those in  FIG. 4 or 26  denote the same steps and a repetitive description thereof will be omitted. 
     After performing overlay and display according to  FIG. 4  in steps S 401  to S 419 , if the operator obtains a recognition result indicating “similar faces” by the face recognition apparatus  340 , the operator or the user instructs the operator terminal  210  or the mobile terminal to display a factor for determining “similar faces”. In step S 3021 , the operator terminal  210  requests a display control apparatus  3030  according to this example embodiment to display a factor for determining “similar faces”. 
     In step S 3025 , the display control apparatus  3030  generates overlaid image data by overlaying a mark on each of high similar regions. In step S 2627 , the display control apparatus  3030  transmits, to the operator terminal  210 , overlaid images respectively indicating the regions as a factor for recognizing the “similar faces”. In step S 2629 , the operator terminal  210  displays the overlaid images, as shown in  FIG. 29 , thereby notifying the operator of the regions as the factor for recognizing the “similar faces”. Note that the instruction to display the recognition factor from the operator terminal  210  has been explained with reference to  FIG. 30 . However, the same applies to processing of a user instruction from the mobile terminal. 
     &lt;&lt;Functional Arrangement of Display Control Apparatus&gt;&gt; 
       FIG. 31  is a block diagram showing the functional arrangement of the display control apparatus  3030  according to this example embodiment. Note that in  FIG. 31 , the same reference numerals as those in  FIG. 5 or 22  denote the same functional components and a repetitive description thereof will be omitted. 
     A similar region selector  3114  receives an instruction to display the regions as a factor for recognizing the “similar faces” from the operator terminal  210 , selects regions having particularly high similarities based on an output of a result of comparing the similarity of each pair of partial regions with a threshold by a comparator  505 , and causes a partial region connector  2211  to generate a connected region of the selected partial regions. 
     &lt;&lt;Display Control Processing Procedure&gt;&gt; 
       FIG. 32  is a flowchart illustrating the procedure of the display control processing of the display control apparatus  3030  according to this example embodiment. This flowchart is executed by a CPU  1610  of  FIG. 16  using a RAM  1640 , thereby implementing the functional components of  FIG. 31 . Note that processing of overlaying the mark of the similarity on the face images is similar to the processing procedure shown in  FIG. 17  and a description thereof will be omitted. 
     In step S 3201 , the display control apparatus  3030  determines whether the operator terminal  210  or the mobile terminal has instructed to display the regions as the factor for recognizing the similar faces. If an instruction to display the regions as the factor for recognizing the similar faces has been sent, in step S 3203  the display control apparatus  3030  generates a connected region of the partial regions that have particularly high similarities and have influenced the face recognition result indicating “similar”, and generates a mark indicating the connected region as the factor for recognizing the similar faces. In step S 3205 , the display control apparatus  3030  overlays the generated mark on each face image, and controls display of the overlaid images on the operator terminal  210 , as shown in  FIG. 29 . 
     According to this example embodiment, since partial regions as a factor for recognizing that faces are similar are generated, and overlaid and displayed on face images, the operator can readily grasp the factor for recognizing that the faces are similar. 
     Sixth Example Embodiment 
     A face recognition system including a display control apparatus according to the sixth example embodiment of the present invention will be described next. The display control apparatus according to this example embodiment is different from those according to the second to fifth example embodiments in that face recognition results are accumulated and learned, and a region of interest or a region of non-interest for performing collation for a generated face image is overlaid and displayed on the face images. The remaining components and operations are the same as those in the second to fifth example embodiments. Hence, the same reference numerals denote the same components and operations, and a detailed description thereof will be omitted. 
     &lt;&lt;Display Screen in Face Recognition&gt;&gt; 
       FIG. 33  is a view showing an outline of the display screen of a terminal  210  according to this example embodiment. The display screen shown in  FIG. 33  is not limited, and may be the display screen of a mobile terminal, the display screen of a PC, or an apparatus dedicated for face recognition or surveillance. Note that in  FIG. 33 , the same reference numerals as those in  FIG. 2A  denote the same components and a repetitive description thereof will be omitted. 
     The display screen of the terminal  210  on the upper side of  FIG. 33  displays a captured face image  3310  and a collation target face image  3320  on which partial regions or connected regions  3312  and  3322  as a factor for erroneous recognition are overlaid as regions of non-interest  3311  by accumulating a history of recognition results and learning it in the face recognition apparatus  340 . Note that both the images may be captured face images or collation target face images. Alternatively, one of the captured face image and the collation target face image may be displayed. Based on the accumulation of the history of recognition results, for example, even if face images are the same, if the person wears glasses, the eyes and their peripheral regions are erroneously recognized to be dissimilar in the general face images or these face images. Thus, marks are overlaid on the face images to exclude the eyes and their peripheral regions from a recognition target. With reference to the overlaid images, the operator can determine whether the remaining regions are similar or dissimilar without paying attention to the eyes and their peripheral regions, thereby reducing the possibility that the images are erroneously recognized to be dissimilar. 
     The display screen of the terminal  210  on the lower side of  FIG. 33  displays a captured face image  3330  and a collation target face image  3340  on which partial regions or connected regions  3332  and  3342  as a factor for erroneous recognition are overlaid as regions  3331  of interest by accumulating the history of recognition results and learning it in the face recognition apparatus  340 . Note that both the images may be captured face images or collation target face images. Alternatively, one of the captured face image and the collation target face image may be displayed. It is leaned based on the accumulation of the history of recognition results that, for example, if eyes and noses and their peripheral regions in general face images or these face images are similar, the influence of similarity or dissimilarity of the remaining regions on a recognition result is small. Marks are then overlaid on the face images to exclude the regions other than the eyes and noses and their peripheral regions from a recognition target. With reference to the overlaid images, the operator can avoid erroneous recognition caused by similarity or dissimilarity of the remaining regions, by paying attention to the eyes and noses and their peripheral regions. 
     Note that  FIG. 33  shows the rectangular partial regions or connected regions. However, regions indicating the regions of non-interest or regions of interest are not limited to the rectangular shape or the number of regions on each face image is not necessarily one. 
     &lt;&lt;Face Recognition System&gt;&gt; 
       FIG. 34  is a sequence chart showing the operation procedure of the face recognition system according to this example embodiment. Note that in  FIG. 34 , the same step numbers as those in  FIG. 4  denote the same steps and a repetitive description thereof will be omitted. 
     After performing overlay and display according to  FIG. 4  in steps S 401  to S 419 , a face recognition apparatus  3440  accumulates, in step S 3411 , a face recognition result and a face image partial region collation result (similarity) in a face recognition history (learning) database to be analyzable. 
     The operator inputs, to the operator terminal  210 , an instruction to overlay a region of interest and/or a region of non-interest before face recognition of himself or herself. Alternatively, a setting may be made in advance in the operator terminal  210 . In step S 3421 , the operator terminal  210  requests the face recognition apparatus  3440  to overlay and display the region of interest and/or region of non-interest. 
     In step S 3425 , the face recognition apparatus  3440  extracts the region of interest and/or region of non-interest from the information accumulated in the learning database. Then, in step S 3427 , the face recognition apparatus  3440  transmits the extracted region of interest and/or region of non-interest to a display control apparatus  3430 . 
     The display control apparatus  3430  acquires, in step S 3424 , the region of interest and/or region of non-interest from the face recognition apparatus  3440 , and overlays, in step S 3431 , the region of interest and/or region of non-interest on the captured face image and/or collation target face image. In step S 3433 , the display control apparatus  3430  transmits an overlaid image indicating the region of interest and/or region of non-interest to the operator terminal  210 . In step S 3435 , the operator terminal  210  displays the overlaid image, as shown in  FIG. 33 , to notify the operator of the region of interest and/or region of non-interest. 
     Note that  FIG. 33  shows the rectangular partial regions or connected regions. However, regions indicating the factor for the recognition result indicating that the faces are similar are not limited to the rectangular shape or the number of regions on each face image is not necessarily one. In addition, if the display control apparatus  3430  and the face recognition apparatus  3440  are integrally formed, extraction of the region of interest and/or region of non-interest and overlaying on the face images are executed simultaneously. 
     &lt;&lt;Functional Arrangement of Display Control Apparatus&gt;&gt; 
       FIG. 35  is a block diagram showing the functional arrangement of the display control apparatus  3430  according to this example embodiment. Note that in  FIG. 35 , the same reference numerals as those in  FIG. 5  denote the same functional components and a repetitive description thereof will be omitted. 
     Under an instruction from the operator terminal  210 , a region-of-interest/region-of-non-interest acquirer  3515  acquires, by communication, a mark of the region of interest and/or the region of non-interest extracted and transmitted by the face recognition apparatus  3440 . An image overlay unit  3509  generates overlaid image data by overlaying the mark of the partial region obtained from the mark generator  507  or the region of interest and/or the region of non-interest acquired by the region-of-interest/region-of-non-interest acquirer  3515  on the face images obtained from a face image storage  503 . 
     Note that the mark may be another mark such as a mark corresponding to a connected region. 
     &lt;&lt;Display Control Processing Procedure&gt;&gt; 
       FIG. 36  is a flowchart illustrating the procedure of the display control processing of the display control apparatus  3430  according to this example embodiment. This flowchart is executed by a CPU  1610  of  FIG. 16  using a RAM  1640 , thereby implementing the functional components of  FIG. 35 . Note that processing of overlaying the mark of the similarity on the face images is similar to the processing procedure shown in  FIG. 17  and a description thereof will be omitted. 
     In step S 3601 , the display control apparatus  3430  determines whether a region to be overlaid is a region of interest. If a region of interest is to be overlaid and displayed, the display control apparatus  3430  acquires, in step S 3603 , the region of interest from the face recognition apparatus  3440 . If the region to be overlaid is not a region of interest, the display control apparatus  3430  determines in step S 3605  whether the region to be overlaid is a region of non-interest. If a region of non-interest is to be overlaid and displayed, the display control apparatus  3430  acquires, in step S 3607 , the region of non-interest from the face recognition apparatus  3440 . In step S 3609 , the display control apparatus  3430  overlays the acquired region of interest or non-interest on the face images, and controls display on the operator terminal  210 . 
     Note that an illustration and description of the flowchart when the region of interest and the region of non-interest are displayed will be omitted. 
     &lt;&lt;Functional Arrangement of Face Recognition Apparatus&gt;&gt; 
       FIG. 37  is a block diagram showing the functional arrangement of the face recognition apparatus  3440  according to this example embodiment. Note that in  FIG. 37 , the same reference numerals as those in  FIG. 10  denote the same functional components and a repetitive description thereof will be omitted. 
     A face recognition history (learning) database  3712  accumulates a recognition result based on the similarities of the pairs of partial regions in the face recognition apparatus  3440  and a history of recognition target face images and recognition factors. A region-of-interest/region-of-non-interest generation transmitter  3713  includes a region-of-interest/region-of-non-interest generation table  3714 , and generates a region of interest/region of non-interest with reference to the face recognition history (learning) database  3712 . 
     (Face Recognition History Database: Learning Database) 
       FIG. 38  is a table showing the structure of the face recognition history (learning) database  3712  according to this example embodiment. The structure of the face recognition history (learning) database  3712  is not limited to that shown in  FIG. 38 . 
     The face recognition history (learning) database  3712  accumulates a recognition result  3803  by the face recognition apparatus and a recognition result  3804  by the operator in association with a captured image ID  3801  for identifying a captured face image and a collation target face image ID  3802  for identifying a collation target face image. The face recognition history (learning) database  3712  stores learning contents  3805 . The recognition result  3803  by the face recognition apparatus includes, for example, a recognition result and a region influencing the determination. The recognition result  3804  by the operator includes, for example, a recognition result and a region of interest. The learning contents  3805  include a match or mismatch result between the recognition result by the face recognition apparatus and that by the operator, a factor for the match, and a factor for the mismatch. 
     Note that although not shown in  FIG. 38 , recognition conditions such as a face recognition date and time may be accumulated as long as they are necessary for learning. 
     (Region-of-Interest and Region-of-Non-Interest Generation Table) 
       FIG. 39  is a table showing the structure of the region-of-interest and region-of-non-interest generation table  3714  according to this example embodiment. The region-of-interest and region-of-non-interest generation table  3714  is used by the region-of-interest/region-of-non-interest generation transmitter  3713  to generate a region of interest and a region of non-interest based on the history accumulated in the face recognition history (learning) database  3712 . 
     The region-of-interest and region-of-non-interest generation table  3714  stores partial region coordinates  3902  on the face image and a degree  3903  of influence on a recognition result in association with a partial region ID  3901  for identifying a partial region of the face image. The degree  3903  of influence on the recognition result includes a high influence score that highly influences the recognition result and a low influence score that does not highly influence the recognition result. The region-of-interest and region-of-non-interest generation table  3714  stores data  3904  indicating whether the partial region is set as a region of interest, and data  3905  indicating whether the partial region is set as a region of non-interest. Note that in  FIG. 39 , each of upper two partial regions is determined as a region of interest, the third region is determined as a region of non-interest, and the fourth region is determined as neither a region of interest nor a region of non-interest. 
     Note that  FIG. 39  shows only the partial regions. However, the same applies to a connected region and the like. 
     &lt;&lt;Region-of-Interest and/or Region-of-Non-Interest Generation Processing Procedure&gt;&gt; 
       FIG. 40  is a flowchart illustrating the procedure of region-of-interest and/or region-of-non-interest generation processing according to the example embodiment. This flowchart is executed by a CPU  1910  of  FIG. 19  using a RAM  1940 , thereby implementing the functional components of  FIG. 37 . Note that processing of overlaying the mark of the similarity on the face images is similar to the processing procedure shown in  FIG. 17  and a description thereof will be omitted. 
     In step S 4001 , the face recognition apparatus  3440  determines whether the operator terminal  210  has instructed to generate a region of interest and/or region of non-interest. If an instruction to generate a region of interest and/or region of non-interest has been sent, the face recognition apparatus  3440  acquires, in step S 4003 , a captured face image from an image capturing apparatus (camera)  320 . In step S 4005 , the face recognition apparatus  3440  acquires a collation target face image to recognize the acquired captured face image. In step S 4007 , the face recognition apparatus  3440  generates a region of interest and a region of non-interest from the acquired captured face image and collation target face image with reference to the history accumulated in the face recognition history (learning) database  3712 . In step S 4009 , the face recognition apparatus  3440  transmits the generated region of interest and/or region of non-interest and the face images to the display control apparatus  3430  to undergo overlay and display. 
     According to this example embodiment, face recognition results are accumulated and learned, and a region of interest and a region of non-interest for performing collation for a generated face image is overlaid and displayed on the face images. Thus, the operator can readily perform face recognition. 
     Seventh Example Embodiment 
     A face recognition system including a display control apparatus according to the seventh example embodiment of the present invention will be described next. The display control apparatus according to this example embodiment is different from those according to the second to sixth example embodiments in that it is included in functional components forming the face recognition system. The remaining components and operations are the same as those in the second to sixth example embodiments. Hence, the same reference numerals denote the same components and operations, and a detailed description thereof will be omitted. 
     &lt;&lt;Face Recognition System&gt;&gt; 
       FIG. 41  is a block diagram showing the arrangement of a face recognition system  4100  according to this example embodiment. The face recognition system  4100  is represented by the minimum number of functional components forming the face recognition system. 
     The face recognition system  4100  includes an image capturer  320 , a face recognition apparatus  340 , and a display unit  4110 . The display unit  4110  includes a display control apparatus  330  that generates a mark indicating whether the similarity of each pair of partial regions exceeds a threshold, and overlays the mark on a face image, and an operator terminal  210  with a display unit  1403  that displays an overlaid image. The face recognition apparatus  340  includes an accumulator, a generator that generates partial regions on a captured face image, a generator that generates partial regions on an accumulated face image, a similarity calculator that calculates the similarity of each pair of partial regions, and a face recognizer based on the similarities of the pairs of partial regions. 
     According to this example embodiment, the effects of the above example embodiments can be implemented by different combinations of various functional components. 
     Eighth Example Embodiment 
     A face recognition system including a display control apparatus according to the eighth example embodiment of the present invention will be described next. The display control apparatus according to this example embodiment is different from those according to the second to seventh example embodiments in that it is implemented as a display control server in a cloud server. The remaining components and operations are the same as those in the second to seventh example embodiments. Hence, the same reference numerals denote the same components and operations, and a detailed description thereof will be omitted. 
     &lt;&lt;Face Recognition System&gt;&gt; 
       FIG. 42A  is a block diagram showing the arrangement of a face recognition system  4201  according to this example embodiment. Note that in  FIG. 42A , the same reference numerals as those in  FIG. 3  denote the same components and a repetitive description thereof will be omitted. 
     The face recognition system  4201  includes a cloud server  4260  connected to a network  350 . The cloud server  4260  includes a display control server  4230  corresponding to the display control apparatus described in the above example embodiments and a face recognition server  4240  corresponding to the face recognition apparatus. 
     In accordance with a request to overlay, on a face image, a mark as support of various face recognition processes, which has been received from an operator terminal  210  for surveillance arranged in an airport or the like, and a note PC  21   i  or a mobile terminal (smartphone, tablet, or the like) as a user terminal, the cloud server  4260  executes integration processing to control display of the overlaid image on each of terminals  210  to  21   n.    
       FIG. 42B  is a block diagram showing the arrangement of a face recognition system  4202  according to this example embodiment. Note that in  FIG. 42B , the same reference numerals as those in  FIG. 3 or 42A  denote the same components and a repetitive description thereof will be omitted. 
     In the face recognition system  4202 , terminals  4211  to  421   n  are mobile terminals (smartphones, tablets, or mobile phones) of users. If a video captured by a camera incorporated in the mobile terminal of the user is transmitted to a cloud server  4260 , the cloud server  4260  displays, on the screen of the mobile terminal of the user, a mark overlaid image as support of face recognition processing desired by the user. 
     According to this example embodiment, the effect of each of the above example embodiments can be implemented by requesting the cloud server even if the self apparatus has no function. 
     Ninth Example Embodiment 
     A face recognition system including a display control apparatus according to the ninth example embodiment of the present invention will be described next. The display control apparatus according to this example embodiment is different from those according to the second to eighth example embodiments in that it is included as part of a face recognition application in a communication terminal serving as a face recognition system. The remaining components and operations are the same as those in the second to eighth example embodiments. Hence, the same reference numerals denote the same components and operations, and a detailed description thereof will be omitted. 
     &lt;&lt;Face Recognition System&gt;&gt; 
       FIG. 43  is a block diagram showing the functional arrangement of a communication terminal  4310  serving as a face recognition system according to this example embodiment. Note that  FIG. 43  shows new reference numerals “ 43 XX” which denote functional components obtained by centrally incorporating the functional components shown in  FIGS. 5 and 10  in the communication terminal  4310 . The functional components having the same names have the same processing functions, and a repetitive description thereof will be omitted. 
     The communication terminal  4310  includes a communication controller  4301 , a face recognition application  4302 , an image capturer (camera)  4303 , a display unit  4304 , and an operation unit  4305 . The face recognition application  4302  corresponds to an application program downloaded to the communication terminal  4310 . The face recognition application  4302  may be incorporated in the communication terminal  4310  in advance. 
     The face recognition application  4302  includes a collation target face image acquirer  4321 , a collation target face image database  4322 , a partial region generator  4323 , and a similarity calculator  4324 . Furthermore, the face recognition application  4302  includes a mark generator  4325  that generates a mark based on a threshold and mark information, a face recognizer  4326  that recognizes a face image based on the similarities of pairs of partial regions, and an overlaid image generator  4327  that overlays the mark on a collation target face image and/or a face image captured by the image capturer (camera)  4303 , and displays the image on the display unit  4304 . 
     According to this example embodiment, the effect of each of the above example embodiments can be implemented by only the terminal. 
     Other Example Embodiments 
     Note that the above example embodiments have explained the example in which the display control apparatus and the face recognition apparatus are separately provided. However, the apparatuses may be integrated into one apparatus or part of one of the apparatuses may be included in the other apparatus. For example, the display control apparatus may have a partial region collation function, and notify the face recognition apparatus of a collation result. Furthermore, a new apparatus that collates partial regions and outputs the result to the display control apparatus and the face recognition apparatus may be provided as a partial region collation apparatus. That is, this arrangement may be adopted as long as it is possible to implement the functions included in the display control apparatus and face recognition apparatus according to this example embodiment. 
     While the invention has been particularly shown and described with reference to example embodiments thereof, the invention is not limited to these example embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims. 
     The present invention is applicable to a system including a plurality of devices or a single apparatus. The present invention is also applicable even when a display control program as an information processing program for implementing the functions of example embodiments is supplied to the system or apparatus directly or from a remote site. Hence, the present invention also incorporates the program installed in a computer to implement the functions of the present invention by the computer, a medium storing the program, and a WWW (World Wide Web) server that causes a user to download the program. Especially, the present invention incorporates at least a non-transitory computer readable medium storing a program that causes a computer to execute processing steps included in the above-described example embodiments.