Abstract:
Disclosed is a surveillance system that detects a suspicious person immediately without fail and presents the detected suspicious person to a surveillant even when the system includes a large number of networked surveillance cameras. An imager included in the surveillance system retains a dynamically-updatable suspicious person list within itself and detects a suspicious person in accordance with a feature amount extracted from an image.

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese Patent Application JP2009-209956 filed on Sep. 11, 2009, the content of which is hereby incorporated by reference into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    (1) Field of the Invention 
         [0003]    The present invention relates to an imager and a surveillance system that are used to detect a face image of a suspicious person from a surveillance image. 
         [0004]    (2) Description of the Related Art 
         [0005]    When a suspicious person is to be detected in an image picked up by a surveillance camera, a suspicious person in a surveillance image is automatically detected in accordance with preregistered suspicious person data (hereinafter referred to as a suspicious person list) and presented to a surveillant for the purpose of providing enhanced surveillance efficiency. 
         [0006]    A security system disclosed, for instance, in Japanese Patent Application Laid-Open Publication No. 2009-59222 detects a suspicious person by comparing a face image detected from a surveillance image against a suspicious person face image registered in a suspicious person list. Further, when this security system detects a suspicious action, it registers a face image of a person performing the suspicious action in the suspicious person list even if the face image does not agree with face images preregistered in the suspicious person list. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    Meanwhile, the security system described in Japanese Patent Application Laid-Open Publication No. 2009-59222 is configured so that the functionality for suspicious person detection and registration is independent of surveillance cameras. No problems occur as far as the number of targeted surveillance cameras is small. However, if a large number of surveillance cameras are targeted, the image transmission load on a network increases. This increases the possibility, for instance, of reducing the frame rate for image transmission or causing a transmission delay. This may result in an inability to acquire a surveillance image of a suspicious person with appropriate timing, thereby losing sight of the suspicious person. The present invention has been made to address the above-described problem, and provides a surveillance system that detects a suspicious person immediately without fail and presents the detected suspicious person to a surveillant even when the system includes a large number of networked surveillance cameras. 
         [0008]    In order to address the above-described problem, according to an embodiment of the present invention, there is provided an imager for use in a surveillance system. 
         [0009]    The imager includes a surveillance image acquirer, a face image detector, a feature amount generator, a suspicious person list, a data manager, a suspicious person discriminator, and a data input/output. The surveillance image acquirer acquires a picked-up surveillance image in real time. The face image detector detects a face image in the surveillance image. The feature amount generator generates the feature amount of the detected face image. The suspicious person list contains registered feature amounts that are generated from previously acquired suspicious person face images. The data manager performs an update process and access management for the suspicious person list. The suspicious person discriminator determines the degree of similarity (hereinafter referred to as the similarity) between a feature amount generated by the feature amount generator and a feature amount registered in the suspicious person list, and judges whether the detected face image depicts a suspicious person. The data input/output exchanges data over a network with another imager and a surveillance server that stores and distributes surveillance images. The greatest characteristic of the imager is to retain a dynamically-updatable suspicious person list within itself and detect a suspicious person in accordance with a feature amount extracted from an image. 
         [0010]    The present invention makes it possible to immediately detect a suspicious person from all persons captured by an imager and present the detected suspicious person to a surveillant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    An embodiment of the present invention will be described in detail based on the following figures, wherein: 
           [0012]      FIG. 1  is a schematic diagram illustrating a surveillance system that is equipped with an imager according to an embodiment of the present invention; 
           [0013]      FIG. 2  is a schematic diagram illustrating a surveillance image list display of a surveillance server according to the embodiment of the present invention; 
           [0014]      FIG. 3  is a schematic diagram illustrating a suspicious person list updater of the surveillance server according to the embodiment of the present invention; 
           [0015]      FIG. 4  is a schematic diagram illustrating a person retriever of the surveillance server according to the embodiment of the present invention; 
           [0016]      FIG. 5  is a diagram showing an equation used in accordance with the embodiment of the present invention; 
           [0017]      FIG. 6  is a flowchart illustrating a typical operation of the imager according to the embodiment of the present invention; 
           [0018]      FIG. 7  is a diagram illustrating an operation of the imager according to the embodiment of the present invention; 
           [0019]      FIG. 8  is a flowchart illustrating a typical operation of the imager according to the embodiment of the present invention; 
           [0020]      FIG. 9  is a diagram illustrating an operation of the imager according to the embodiment of the present invention; 
           [0021]      FIG. 10  is a flowchart illustrating a typical operation of the imager according to the embodiment of the present invention; 
           [0022]      FIG. 11  is a diagram illustrating an operation of the imager according to the embodiment of the present invention; 
           [0023]      FIG. 12  is a diagram illustrating the structure of suspicious person list data for the imager; 
           [0024]      FIG. 13  is a diagram illustrating the structure of surveillance data for the imager; 
           [0025]      FIG. 14  is a diagram illustrating the structure of control data; 
           [0026]      FIG. 15  is a diagram illustrating the structure of suspicious person list data for the surveillance server; and 
           [0027]      FIG. 16  is a set of drawings illustrating typical screens displayed by a screen data generator. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    An embodiment of the present invention will now be described with reference to the accompanying drawings. Like elements are designated by the same reference numerals and will not be redundantly described.  FIG. 1  is a schematic diagram illustrating a surveillance system that is equipped with an imager according to the present embodiment of the present invention. 
         [0029]    As shown in  FIG. 1 , the surveillance system  1  according to the present embodiment of the present invention presents surveillance images of a predetermined surveillance region to a user (surveillant), and includes plural imagers  10 , a surveillant device  20 , and a surveillance server  30 . The plural imagers  10 , the surveillant device  20 , and the surveillance server  30  are interconnected through a network NW to permit them to communicate with each other. 
       &lt;Imagers  10 &gt; 
       [0030]    Each imager  10  is a device that picks up images of a predetermined surveillance region and detects a suspicious person in the picked-up surveillance images. This device includes a surveillance image acquirer  11 , a face image detector  12 , a feature amount generator  13 , a suspicious person discriminator  14 , a suspicious person list  15 , surveillance data  17 , a data manager  16 , a data input/output  18 , a controller  19 , and control data  19   a.    
         [0031]    The surveillance image acquirer  11  can acquire a surveillance image as digital data in real time. For example, the surveillance image acquirer  11  may be a color CCD (Charge-Coupled Device). The acquired surveillance image is associated with a unique surveillance image ID and output to the face image detector  12  and surveillance data  17 . In addition to the surveillance image and surveillance image ID, an imaging time and an imager ID that are associated with the surveillance image are also output to the surveillance data  17 . 
         [0032]    The face image detector  12  extracts a person&#39;s face from a surveillance image output from the surveillance image acquirer  11  and generates a face image. More specifically, the face image detector  12  recognizes the position of a face in accordance, for instance, with the size and shape of a skin-tone portion of the surveillance image, and generates a face image in accordance with the recognized face position. The generated face image is associated with a unique face ID and with the surveillance image ID, and output to the feature amount generator  13  and surveillance data  17 . 
         [0033]    The feature amount generator  13  generates the feature amount of a face image output from the face image detector  12 . The feature amount data can be calculated by a publicly known method. A method disclosed, for instance, in Japanese Patent Application Laid-Open Publication 2008-257649 determines the brightness gradient between a target pixel of image data and individual pixels within an area peripheral to the target pixel and the direction of such a gradient, generates a histogram for each predetermined direction, and uses the direction of peak value acquisition as the feature amount of the target pixel. The peripheral area may be simply defined as an area formed by eight pixels around the target pixel. 
         [0034]    The generated feature amount is associated with the surveillance image ID and with the face ID, and output to the suspicious person discriminator  14  and surveillance data  17 . 
         [0035]    The suspicious person discriminator  14  acquires a feature amount of a retained suspicious person list  15  through the data manager  16 , calculates the similarity between a feature amount in the suspicious person list  15  and a feature amount output from the feature amount generator  13 , and checks for highly similar feature amounts to determine whether a target face image depicts a suspicious person. In the present embodiment of the present invention, the similarity is represented by a parameter that decreases with an increase in similarity between two feature amounts. A publicly known method can be used to calculate the similarity. When, for instance, the aforementioned brightness gradient is used for feature amounts, the mean-square distance between feature amounts determined from two face images can be used. When, for instance, the two feature amounts are f(x 1 , y 1 ) and f(x 2 , y 2 ), respectively, the mean-square distance d between them is √{square root over ((x 1 −x 2 ) 2 +(y 1 −y 2 ) 2 )}{square root over ((x 1 −x 2 ) 2 +(y 1 −y 2 ) 2 )} as indicated by the equation in  FIG. 5 . If the calculated similarity parameter value representing the similarity is smaller than a predetermined threshold value, it is judged that the two face images depict the same person. The threshold value is predetermined for a specific imager in accordance with average similarity between face images that should be judged to be the face images of the same person. The above judgment result is associated with the surveillance image ID and the face ID, and output to the data input/output  18 . 
         [0036]    In accordance with information that is output from the suspicious person discriminator  14 , the data input/output  18  extracts the associated data from the surveillance data  17  and generates output data. Data stored as the surveillance data  17  includes a surveillance image, surveillance image ID, imaging time, and imager ID, which are output from the surveillance image acquirer  11 ; a face image and face ID, which are output from the face image detector  12 ; and a feature amount, which is output from the feature amount generator  13 . The generated output data is output to the surveillance server  30 , the surveillant device  20 , or another imager  10  through the network NW. The output data delivered to the surveillance server  30  or surveillant device  20  includes a priority, a suspicious person ID, and the aforementioned surveillance data  17 . The priority is based on information output from the suspicious person discriminator  14 . The priority is set to be high when it is judged that the target face image depicts a suspicious person. The suspicious person ID is a unique number that is set to identify a suspicious person, commonly used in the entire surveillance system, and retained after being associated with a specific feature amount in the suspicious person list  15 . The output data delivered to another imager  10  includes a priority, a suspicious person ID, an imaging time, an imager ID, a face image, and a feature amount. However, the contents of the output data can be changed in compliance with system specifications. The data input/output  18  is controlled in such a manner that surveillance data having high priority is transmitted immediately without fail. Upon receipt of data from the surveillance server  30 , the surveillant device  20 , or another imager  10 , the data input/output  18  outputs the received data to the data manager  16 . In accordance with the data output from the data input/output  18 , the data manager  16  updates the data in the suspicious person list  15 , updates the control data  19   a , or outputs an imaging time and imager ID to the controller  19 . In accordance with the data output from the data manager  16 , the controller  19  acquires a control procedure for the local imager  10  from the control data  19   a  and exercises control accordingly. 
       &lt;Surveillant Device  20 &gt; 
       [0037]    The surveillant device  20  is, for example, a personal computer, and includes an input  21 , an output  23 , and a controller  22 . 
         [0038]    The input  21  is a mouse, a keyboard, or the like, and outputs input data based on a surveillant&#39;s operation to the controller  22 . 
         [0039]    The controller  22  includes, for instance, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read-Only Memory), a HDD (Hard Disk Drive), and an input/output circuit, and controls the operations of the input  21  and the output  23 , and transmits and receives data through the network NW. In the present embodiment, the controller  22  operates in accordance with a surveillant&#39;s input operation, which is performed with the input  22 , to generate face image data and face image selection data and output them to the surveillance server  30  or imagers  10  through the network NW. 
         [0040]    The output  23  is a display. For example, the output  23  presents a surveillance screen, which is output from the surveillance server  30 , or displays the data about a suspicious person, which is output from an imager  10 . 
       &lt;Surveillance Server  30 &gt; 
       [0041]    The surveillance server  30  includes, for instance, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read-Only Memory), a HDD (Hard Disk Drive), and an input/output circuit. Functionally, the surveillance server  30  is divisible into a surveillance image list display  31 , a suspicious person list updater  32 , a person retriever  33 , a face image detector  34 , a feature amount generator  35 , a suspicious person list  36 , a surveillance data memory  37 , and a screen data generator  38 . 
         [0042]      FIG. 2  is a schematic diagram illustrating the surveillance image list display  31 .  FIG. 3  is a schematic diagram illustrating the suspicious person list updater  32 .  FIG. 4  is a schematic diagram illustrating the person retriever  33 . 
         [0043]    As shown in  FIG. 2 , the surveillance image list display  31  displays a list of latest surveillance images that are acquired from the plural imagers  10  through the network NW, and presents the listed surveillance images to the surveillant. The surveillance image list display  31  includes a surveillance data acquirer  31   a , a presentation priority selector  31   b , and a suspicious person discriminator  31   c.    
         [0044]    The surveillance data acquirer  31   a  acquires the surveillance data  17 , priorities, and suspicious person IDs output from the plural imagers  10  through the network NW, and outputs them to the presentation priority selector  31   b  and surveillance data memory  37 . If the data acquired by the surveillance data acquirer  31   a  does not include face image information or feature amounts or if the feature amount of a face image is to be generated anew, a target surveillance image is output to the face image detector  34 , and image data acquired through the feature amount generator  35  and suspicious person discriminator  31   c  is output to the presentation priority selector  31   b . The process performed in the face image detector  34  is the same as the process performed in the earlier-described face image detector  12 . More specifically, a surveillance image ID and a face image associated with a unique face ID are generated. However, the face image detector  34  and the earlier-described face image detector  12  do not have to use the same face detection method. Similarly, the process performed in the feature amount generator  35  is the same as the process performed in the earlier-described feature amount generator  13 . Further, the process performed in the suspicious person discriminator  31   c  is the same as the process performed in the earlier-described suspicious person discriminator  14 . The surveillance data memory  37  stores previous surveillance data for a period defined for a surveillance operation or until it runs out of storage space. 
         [0045]    The presentation priority selector  31   b  selects a surveillance image for presentation by examining the priority, imaging time, and imager included in the surveillance data output from the surveillance data acquirer  31   a  or suspicious person discriminator  31   c , and outputs the selected presentation surveillance image to the screen data generator  38 . The rules for selection vary with the surveillant device  20  and can be defined from the surveillance device  20 . 
         [0046]    The screen data generator  38  is an example of a surveillance image list output that outputs a result produced by the presentation priority selector  31   b , and generates screen data for displaying not only a surveillance image depicting a suspicious person but also surveillance images received from the plural imagers.  FIG. 16  shows typical screens displayed by the screen data generator  38 . The upper drawing in  FIG. 16  shows a surveillance image list screen. This screen shows surveillance images  41   a - 41   j  picked up by the individual imagers. When a suspicious person is detected, the screen data generator  38  displays a screen  43  in addition to the surveillance image list screen as indicated by the lower drawing in  FIG. 16 . This additional screen  43  shows a surveillance image  43   b  depicting the suspicious person, a face image  43   a  of the suspicious person, and relevant information such as an imager ID and imaging time. 
         [0047]    As shown in  FIG. 3 , the suspicious person list updater  32  updates the suspicious person list  36  in accordance with a command received from an imager  10  or the surveillant device  20  through the network NW, and includes a suspicious person data acquirer  32   a , a data manager  32   b , and an update completion notifier  32   c . The data structure of the suspicious person list  36  is shown in  FIG. 15 . The data structure of the suspicious person list  15  is shown in  FIG. 12 . In the suspicious person list  36 , the imager ID is associated with the information about a suspicious person in addition to data entries in the suspicious person list  15  of each imager. Therefore, the suspicious person lists  15  of the individual imagers are integrated into the suspicious person list  36 . However, the values of the individual data entries are unique to the surveillance server and not equal to those in the suspicious person list  15 . Further, the suspicious person list  36  does not have to include the entire data in the suspicious person list  15 . 
         [0048]    The suspicious person data acquirer  32   a  acquires a processing command, an imager ID, a priority, a suspicious person ID, a face image, a feature amount, and other data output from the imagers  10  and surveillant device  20  through the network NW, and outputs the acquired data to the data manager  32   b . If the data acquired by the suspicious person data acquirer  32   a  includes neither a surveillance image ID of the surveillance data memory  37  nor face image information or feature amount, or if the feature amount of a face image is to be generated anew, a target surveillance image is output to the face image detector  34  as well, and a face image and feature amount are acquired from the feature amount generator  35  and output to the data manager  32   b.    
         [0049]    The data manager  32   b  updates the suspicious person list in accordance with a processing command output from the suspicious person data acquirer  32   a  or feature amount generator  35 . If the processing command is “Add” or “Update,” the imager ID, priority, suspicious person ID, face image, feature amount, and other data output from the suspicious person data acquirer  32   a  or feature amount generator  35  are entered into the suspicious person list  36  for registration or update purposes. If, on the other hand, the processing command is “Delete,” the data corresponding to a suspicious person list registration ID output from the suspicious person data acquirer  32   a  or feature amount generator  35  is deleted from the suspicious person list. Further, if the data output from the suspicious person data acquirer  32   a  includes a surveillance data registration ID indicative of data stored in the surveillance data memory  37 , a feature amount stored in the surveillance data memory  37  can be registered in the suspicious person list. 
         [0050]    The update completion notifier  32   c  acquires process completion information from the data manager  32   b , and transmits the process completion information to an imager  10  or the surveillant device  20  that has generated a request for suspicious person list update. 
         [0051]    As shown in  FIG. 4 , the person retriever  33  conducts a similar image search by using the feature amount of a search query face image acquired from the surveillant device  20  through the network NW for the purpose of searching the surveillance data memory  37  for the same person as a person depicted by the search query face image, and includes a search query acquirer  33   a , a similarity calculator  33   b , and a sorter  33   c.    
         [0052]    The search query acquirer  33   a  acquires a search query output from the surveillant device  30  through the network NW, and outputs the acquired search query to the similarity calculator  33   b . If the search query is a surveillance image or if the feature amount of a face image is to be generated anew, a target surveillance image is output to the face image detector  34 , and a face image and feature amount are acquired through the feature amount generator  35  and output to the similarity calculator  33   b.    
         [0053]    The similarity calculator  33   b  calculates the similarity between a feature amount output from the search query acquirer  33   a  or feature amount generator  35  and a feature amount stored in the surveillance data memory  37 . In the present embodiment of the present invention, the similarity is represented by a parameter that decreases with an increase in similarity between two feature amounts. A publicly known method can be used to calculate the similarity. When, for instance, the aforementioned brightness gradient is used for feature amounts, the mean-square distance between feature amounts determined from two face images can be used. When, for instance, the two feature amounts are f(x 1 , y 1 ) and f(x 2 , y 2 ), respectively, the mean-square distance d between them is √{square root over ((x 1 −x 2 ) 2 +(y 1 −y 2 ) 2 )}{square root over ((x 1 −x 2 ) 2 +(y 1 −y 2 ) 2 )} as indicated by the equation in  FIG. 5 . The calculated similarity is output to the sorter  33   c . Here, a surveillance data registration ID in the surveillance data memory  37  can also be used as a search query. If such a surveillance data registration ID is used as the search query, the feature amount of the surveillance data registration ID is acquired from the surveillance data memory  37 , and the similarity between the acquired feature amount and another feature amount stored in the surveillance data memory  37  is calculated. 
         [0054]    The sorter  33   c  sorts all similarities output from the similarity calculator  33   b  in ascending order (from the smallest similarity parameter value to the greatest). In other words, the sorter  33   c  sorts the feature amounts in the surveillance data memory  37  in order from the highest similarity to a search query face image to the lowest. Then, a predetermined number of feature amounts having relatively small similarity parameter values are selected from those arranged in ascending order of similarity parameter values, and output to the screen data generator  38 . 
         [0055]    The screen data generator  38  is an example of a search result output that outputs a result produced by the person retriever  33 , and generates search result display screen data for displaying a surveillance image in the surveillance data memory  37  in accordance with a result generated from the sorter  33   c.    
         [0056]    Further, in accordance with a surveillance image stored in the surveillance data memory  37  or a face image retained by the surveillant device  20 , the screen data generator  38  can also generate query face image designation screen data, which enables the surveillant to display a query image for a person search on the output  23  of the surveillant device  20 . The generated search result display screen data and query face image designation screen data are output to the surveillant device  20  through the network NW. 
         [0057]    A first typical operation of an imager  10  according to the present embodiment of the present invention will now be described with reference to  FIGS. 6 and 7  (and with occasional reference to  FIG. 1 ).  FIG. 6  is a flowchart illustrating a typical operation performed by an imager  10  according to the present embodiment of the present invention.  FIG. 7  illustrates the flow of data during the operation indicated in  FIG. 6 .  FIG. 12  shows the data structure of the suspicious person list  15 .  FIG. 13  shows the data structure of the surveillance data  17 .  FIG. 14  shows the data structure of the control data  19   a.    
         [0058]    First of all, as shown in  FIGS. 6 and 7 , the surveillance image acquirer  11  of an imager  10  acquires a surveillance image by picking up an image of a surveillance region (step S 601 ), and outputs the acquired surveillance image to the face image detector  12  and surveillance data  17  together with a unique surveillance image ID. An imager ID and imaging time are also output to the surveillance data  17  and retained in addition to the surveillance image and surveillance image ID. The face image detector  12  generates a face image by detecting and cutting out a face region in the surveillance image (step S 603 ), and outputs the generated face image to the feature amount generator  13  and surveillance data  17  together with a unique face ID. If no face region is detected from the surveillance image, the process for that surveillance image terminates. If plural face regions are detected from the surveillance image, face IDs are assigned to individual face images and sequentially output to the feature amount generator  13 . The feature amount generator  13  generates the feature amount of a face image (step S 604 ), and outputs the generated feature amount and the associated face ID to the suspicious person discriminator  14  and surveillance data  17 . The suspicious person discriminator  14  calculates the similarity between the feature amount acquired from the feature amount generator  13  and a feature amount registered in the suspicious person list acquired through the data manager  16  (step S 605 ). The suspicious person discriminator  14  then compares the calculated similarity against a predetermined threshold value to determine the priority of a target feature amount (step S 606 ), and outputs the determined priority to the data input/output  18 . In accordance with the priority acquired from the suspicious person discriminator  14 , the data input/output  18  controls the output to the surveillance server  30 . If the priority is high, step S 608  is performed to output the surveillance data  17  and the priority to the surveillance server  30  through the network NW. If, on the other hand, the priority is not high, step S 609  is performed to judge in accordance with the rules of a target surveillance system whether the surveillance data  17  and the priority should be output to the surveillance server  30 . Typical rules would be such that the surveillance data  17  and the priority should not be output if, for instance, the priority is greater than a threshold value and the feature amount is similar to a feature amount that was output to the surveillance server  30  within a predetermined period of time. Meanwhile, the controller  19  controls the pan and tilt of the imager in accordance with the data structure of the control data  19   a  shown in  FIG. 14 . 
         [0059]    A second typical operation of an imager  10  according to the present embodiment of the present invention will now be described with reference to  FIGS. 8 and 9  (and with occasional reference to  FIG. 1 ).  FIG. 8  is a flowchart illustrating a typical operation performed by an imager  10  according to the present embodiment of the present invention.  FIG. 9  illustrates the flow of data during the operation indicated in  FIG. 8 . 
         [0060]    As shown in  FIGS. 8 and 9 , the data input/output  18  acquires a processing command and processing data for the suspicious person list  15  from the surveillance server  30  or another imager  10  through the network NW (step S 801 ), and outputs the acquired processing command and processing data to the data manager  16 . The data manager  16  updates the suspicious person list  15  in accordance with the processing command. If the processing command is “Add,” the processing data includes a suspicious person ID and feature amount; therefore, step S 803  is performed to additionally register the suspicious person ID and feature amount in the suspicious person list  15 . If the processing command is “Update Feature Amount,” the processing data includes a suspicious person list registration ID, suspicious person ID, and feature amount; therefore, step S 805  is performed to update the suspicious person ID and feature amount associated with the suspicious person list registration ID in the suspicious person list  15 . If the processing command is “Delete,” the processing data includes a suspicious person list registration ID; therefore, step S 807  is performed to delete data corresponding to the suspicious person list registration ID in the suspicious person list  15 . After the suspicious person list  15  is updated by the processing command, a process completion notification indicating the completion of such an update is output to the data input/output  18 . The data input/output  18  outputs the process completion notification to the surveillance server  30 , which has issued the processing command, or to another imager  10  (step S 808 ). 
         [0061]    A third typical operation of an imager  10  according to the present embodiment of the present invention will now be described with reference to  FIGS. 10 and 11  (and with occasional reference to  FIG. 1 ).  FIG. 10  is a flowchart illustrating a typical operation performed by an imager  10  according to the present embodiment of the present invention.  FIG. 11  illustrates the flow of data during the operation indicated in  FIG. 10 . 
         [0062]    As shown in  FIGS. 10 and 11 , the data input/output  18  acquires a processing command and a control data registration ID for the controller  19  from the surveillance server  30  or another imager  10  through the network NW (step S 1001 ), and outputs the acquired processing command and control data registration ID to the data manager  16 . If the processing command is “Control Imager,” the data manager  16  outputs the control data registration ID to the controller  19  (step S 1002 ). The controller  19  outputs the control data registration ID to the control data  19   a  and acquires a relevant control procedure from the control data  19   a  (step S 1003 ). The controller  19  then controls the local imager in accordance with the acquired control procedure (step S 1004 ). Upon completion of control exercised in accordance with the acquired control procedure, the controller  19  outputs a control completion notification to the surveillance server  30 , which has issued the processing command, or to another imager  10  through the data manager  16  or the data input/output  18  (step S 1005 ).