Patent Publication Number: US-2020280699-A1

Title: Display device, imaging and display system, and train

Description:
TECHNICAL FIELD 
     The present invention relates to display devices, imaging and display systems, and trains. 
     The present application claims the benefit of priority to Japanese Patent Application, Tokugan, No. 2017-223817 filed on Nov. 21, 2017, the entire contents of which are incorporated herein by reference. 
     BACKGROUND ART 
     Conventional display technology includes at least one video-capturing camera installed on a station platform (hereinafter may be referred to as “platform”) and display devices for displaying a captured video, so that the train driver, conductor, and station staff can watch the displayed video to check and ensure safety on the station platform. Two or more cameras may be installed at places where the cameras will be free from blind areas if the railway staff cannot find a long line-of-sight, particularly if the train consists (primarily) of many carriages or the station platform is situated on a curved track. The technology is very useful because it enables the train driver, conductor, and station staff to monitor the entire station platform without having to walking up and down the platform. Video-based safety monitoring is also useful in reducing manpower in checking and ensuring safety on station platforms. 
     Patent Literature 1 describes an example of such platform safety monitoring technology where a safety monitoring device displays multiple videos captured by a plurality of cameras on a single monitor in the conductor&#39;s cabin. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication, Tokukaihei, No. 9-93565 (Publication Date: Apr. 4, 1997) 
     SUMMARY OF INVENTION 
     Technical Problem 
     The safety monitoring device described in Patent Literature 1, however, is built without paying attention to the relationship between the imaging direction of a camera and that of another or the relationship between the imaging directions of the cameras and the location of the person who checks the videos and also without paying attention to how the videos should be arranged on a single monitor. A display may be produced in which it is difficult to recognize the relative positions of the carriages and the subject on the platform, depending on the imaging directions of the cameras and the layout of the images on a single monitor. 
     The present invention, in an aspect thereof, has an object to produce a display of a train and a vicinity thereof in a manner suitable for monitoring. 
     Solution to Problem 
     To address these issues, the present invention, in an aspect thereof, is directed to a display device installed on a train including a plurality of carriages on at least one of which an imaging device is installed, the display device including: an image processing unit configured to generate a display image based on an image captured by the imaging device and on relative positions of the carriage on which the imaging device is installed and a carriage on which the display device is installed; and a display unit configured to display the display image generated by the image processing unit. 
     Advantageous Effects of Invention 
     The present invention, in an aspect thereof, can produce a display of a train and a vicinity thereof in a manner suitable for monitoring. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Portion (a) of  FIG. 1  is a block diagram of a configuration of major components of a display system installed in a train in accordance with Embodiment 1 of the present invention, (b) of  FIG. 1  is a side view of the train in accordance with Embodiment 1 of the present invention, and (c) of  FIG. 1  is a plan view of the train in accordance with Embodiment 1 of the present invention. 
         FIG. 2  is a set of plan views of the train in accordance with Embodiment 1 of the present invention. 
         FIG. 3  is an illustration of exemplary displays of camera-captured images arranged next to each other in accordance with Embodiment 1 of the present invention. 
         FIG. 4  is an illustration of exemplary displays of camera-captured images arranged next to each other in accordance with Embodiment 1 of the present invention. 
         FIG. 5  is an illustration of an exemplary display of camera-captured images arranged next to each other in accordance with Embodiment 1 of the present invention. 
         FIG. 6  is an illustration of a display screen of a display device in accordance with Embodiment 1 of the present invention. 
       Portion (a) of  FIG. 7  is a side view of a carriage in accordance with Embodiment 2 of the present invention, and (b) of  FIG. 7  is a plan view of the carriage in accordance with Embodiment 2 of the present invention. 
         FIG. 8  is a plan view of a train in accordance with Embodiment 2 of the present invention. 
         FIG. 9  is a plan view of a portion of a train in accordance with Embodiment 2 of the present invention. 
         FIG. 10  is a set of side views of a train in accordance with Embodiment 3 of the present invention. 
         FIG. 11  is an illustration of a display screen of a display device in accordance with Embodiment 4 of the present invention. 
       Portion (a) of  FIG. 12  is an illustration of display images for monitoring the left side of carriages of a train in accordance with Embodiment 4 of the present invention when the train is moving to the right in the figure, and (b) of  FIG. 12  is an illustration of display images for monitoring the right side of the carriages of a train in accordance with Embodiment 4 of the present invention when the train is moving to the right in the figure. 
         FIG. 13  is an illustration of an overhead view of a train and camera-captured images being displayed on a display screen in accordance with Embodiment 4 of the present invention. 
         FIG. 14  is an illustration of an overhead view of a train and camera-captured images being displayed on a display screen in accordance with Embodiment 5 of the present invention. 
         FIG. 15  is an illustration of an overhead view of a train and camera-captured images being displayed on a display screen in accordance with Embodiment 6 of the present invention. 
         FIG. 16  is an illustration of an overhead view of a train and camera-captured images being displayed on a display screen in accordance with Embodiment 6 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
     The following will describe in detail a display device  1  in accordance with Embodiment 1 of the present invention with reference to  FIGS. 1 to 6 . 
     Portion (a) of  FIG. 1  is a block diagram of a configuration of major components of a display system (imaging and display system)  50  installed in a train  100  in accordance with the present embodiment. The display system  50  installed in the train  100  primarily includes display devices  1  and cameras (imaging devices)  106  to  117  (portion (a) of  FIG. 1  shows the camera  106  alone and none of the other cameras). Each display device  1 , installed in the train  100 , is connected to the cameras  106  to  117  via wired or wireless communication, to acquire images captured by the cameras  106  to  117  for display. The cameras  106  to  117  are installed on at least some of the carriages making up the train  100  to capture images of the exterior of the carriages. 
     The display device  1  includes an image processing unit  11  and a display unit  12 . The image processing unit  11  generates display images from images captured by the cameras  106  to  117  on the basis of the relative positions of the carriages where the cameras  106  to  117  are installed and the carriages where the display device  1  is installed. The display unit  12  displays the display images generated by the image processing unit  11 . 
     Portion (b) of  FIG. 1  is a side view of the train  100  in accordance with the present embodiment as the train  100  is viewed from a side thereof. Portion (c) of  FIG. 1  is a plan view of the train  100  in accordance with the present embodiment as the train  100  is viewed from above. 
     The train  100  consists (primarily) of a set of coupled carriages  101 ,  102 , and  103 . The carriage  101  has a driver&#39;s cab  104 , and the carriage  103  has a driver&#39;s cab  105 . The carriage  101  has the cameras  106 ,  107 ,  112 , and  113 , the carriage  102  has the cameras  108 ,  109 ,  114 , and  115 , and the carriage  103  has the cameras  110 ,  111 ,  116 , and  117 . The cameras  106  to  117  are all located substantially along a straight line on the sides of the carriages. In an aspect of the invention, there is no need to provide a camera on every carriage, It is only required that a camera be provided on at least one of the carriages. 
     The display device  1  is installed each driver&#39;s cab  104  and  105 . 
     Portions (a), (b), (c), and (d) of  FIG. 2  are plan views of the train  100  in accordance with the present embodiment as the train  100  is viewed from above. Portion (a) of  FIG. 2  illustrates an imaging range  206  of the camera  106  installed on a side of the carriage  101 , an imaging range  208  of the camera  108  installed on a side of the carriage  102 , and an imaging range  210  of the camera  110  installed on a side of the carriage  103 . The cameras  106 ,  108 , and  110  are provided so as to respectively capture images of the sides of the carriages, for the purpose of monitoring a station platform. The cameras  106 ,  108 , and  110  are pointed in the same direction. 
     Portion (b) of  FIG. 2  illustrates an imaging range  207  of the camera  107  installed on a side of the carriage  101 , an imaging range  209  of the camera  109  installed on a side of the carriage  102 , and an imaging range  211  of the camera  111  installed on a side of the carriage  103 . The cameras  107 ,  109 , and  111  are provided so as to respectively capture images of the sides of the carriages, for the purpose of monitoring a station platform. The cameras  107 ,  109 , and  111  are pointed in the same direction. 
     Portion (c) of  FIG. 2  shows the imaging ranges  206 ,  208 , and  210  in (a) of  FIG. 2  superimposed over the imaging ranges  207 ,  209 , and  211  in (b) of  FIG. 2 . The cameras  106 ,  108 , and  110  are pointed in the opposite direction from the cameras  107 ,  109 , and  111  as shown in (c) of  FIG. 2 . The imaging range  206  partially overlaps the imaging range  207 , the imaging range  208  partially overlaps the imaging range  209 , and the imaging range  210  partially overlaps the imaging range  211 . 
     Assuming that the train  100  is moving to the right in (c) of  FIG. 2  (which is the forward direction), the cameras  106 ,  108 , and  110  have imaging ranges covering the forward direction with respect to the train  100 , and the cameras  107 ,  109 , and  111  have imaging ranges covering the backward direction with respect to the train  100 . 
     In accordance with this, if there is a camera installed in a carriage located forward of the carriage where the display device  1  under consideration is installed, the image processing unit  11  selects an image captured by the camera having an imaging range covering the forward direction (i.e., an image having such an angle of view as to cover the forward direction with respect to the train  100 ) from those images captured by the camera installed in the carriage located forward. if there is a camera installed in a carriage located backward of the carriage where the display device  1  under consideration is installed, the image processing unit  11  selects an image captured by the camera having an imaging range covering the backward direction (i.e., an image having such an angle of view as to cover the backward direction with respect to the train  100 ) from those images captured by the camera installed in the carriage located backward. The image processing unit  11  then generates a display image from the selected image. 
     Portion (d) of  FIG. 2  shows that the cameras  106 ,  108 , and  110  in (a) of  FIG. 2  are capable of imaging the backward direction as well as the forward direction. The cameras  106 ,  108 , and  110 , in (a) and (d) of  FIG. 2 , allow for imaging range control. 
     In accordance with this, if there is a camera installed in a carriage located forward of the carriage where the display device  1  under consideration is installed, the image processing unit  11  controls the camera installed in the carriage located forward in such a manner that the imaging range of the camera covers the forward direction with respect to the train  100 . If there is a camera installed in a carriage located backward of the carriage where the display device  1  under consideration is installed, the image processing unit  11  controls the camera installed in the carriage located backward in such a manner that the imaging range of the camera covers the backward direction with respect to the train  100 . The image processing unit  11  then generates a display image from the image captured by the camera thus controlled. 
       FIG. 3  is an illustration of exemplary displays of camera-captured images arranged next to each other in accordance with Embodiment 1 of the present invention. When the display image is to include a plurality of images, the image processing unit  11  arranges the images in such a manner that the carriages where the cameras capturing the images are installed appear lined up along a specific direction in the approaching order when viewed from the carriage where the display device  1  is installed. The specific direction is parallel to the direction from the distant view to the near view in each image. These specifics are applied to both cases where each camera has an imaging range covering the forward direction with respect to the train  100  or the backward direction with respect to the train  100  and cases where each camera allows for imaging range control. 
     Portion (a) of  FIG. 3  illustrates an exemplary display in accordance with the present embodiment where an image  301  captured by the camera  106 , an image  302  captured by the camera  108 , and an image  303  captured by the camera  110  are arranged next to each other. Each image shows the train  100  in the left and a station platform in the right. Each image further shows a passenger  304  standing on the platform. The cameras  106 ,  108 , and  110  are pointed in the same direction. Each captured image  301 ,  302 , and  303  shows a near view in the bottom thereof and a distant view in the top thereof. All the captured images  301 ,  302 , and  303  hence share the same near-view-to-distant-view direction. As shown in (a) of  FIG. 2 , the camera  106  is pointed in the direction of the cameras  108  and  110 , and the camera  108  is pointed in the direction of the camera  110 . 
     Therefore, the captured images  301 ,  302 , and  303 , when arranged in the order shown in (a) of  FIG. 3 , show the distant view in each of the three captured images contiguously to the near view in a next one of the three captured images. The display device  1  can thus display captured images covering the length of the train  100  along the moving direction of the train  100 , so that one can easily recognize the relative positions and directions represented by the images. The produced display is suitable for the monitoring of the station platform by the user. 
     Meanwhile, similarly to (a) of  FIG. 3 , (b) of  FIG. 3  illustrates an exemplary display in accordance with the present embodiment where the image  301  captured by the camera  106 , the image  302  captured by the camera  108 , and the image  303  captured by the camera  110  are arranged next to each other. A difference lies where the captured image  301  and the captured image  303  are transposed in the display shown in (b) of  FIG. 3  from (a) of  FIG. 3 . In the display order shown in (b) of  FIG. 3 , the display device  1  displays the images captured by the camera  108  and the camera  110 , which are disposed away from the camera  106 , below the image  301  captured by the camera  106 . In other words, the display device  1  displays the captured images  302  and  303 , which are distant view images for the camera  106 , next to the near view side of the captured image  301 . 
     This arrangement does not place the distant view in each of the three captured images contiguously to the near view in a next one of the three captured images, which makes the relative positions and directions represented by the images complicated when compared with the display order shown in (a) of  FIG. 3 . The display order shown in (a) of  FIG. 3  is hence more suitable because it is easier to recognize the relative positions and directions represented by the images in the display order shown in (a) of  FIG. 3 . 
     Portion (a) of  FIG. 4  illustrates an exemplary display in accordance with the present embodiment where an image  305  captured by the camera  107 , an image  306  captured by the camera  109 , and an image  307  captured by the camera  111  are arranged next to each other. Each image shows the train  100  in the right and a station platform in the left. The captured image  307  further shows the passenger  304  standing on the platform. The cameras  107 ,  109 , and  111  are pointed in the same direction. Each captured image  305 ,  306 , and  307  shows a near view in the bottom thereof and a distant view in the top thereof. All the captured images  305 ,  306 , and  307  hence share the same near-view-to-distant-view direction. As shown in (b) of  FIG. 2 , the camera  111  is pointed in the direction of the cameras  107  and  109 , the camera  109  is pointed in the direction of the camera  107 . 
     Therefore, the captured images  305 ,  306 , and  307 , when arranged in the order shown in (a) of  FIG. 4 , show the distant view in each of the three captured images contiguously to the near view in a next one of the three captured images. The display device  1  can thus display captured images covering the length of the train  100  along the direction of the train  100 , so that one can easily recognize the relative positions and directions represented by the images. The produced display is suitable for the monitoring of the station platform by the user. 
     Accordingly, the near and distant views in the three captured images are displayed contiguously by arranging the three captured images in a proper order, regardless of whether the display device  1  is to display the images captured by the cameras  106 ,  108 , and  110  or the images captured by the cameras  107 ,  109 , and  111  pointed in the opposite direction from the cameras  106 ,  108 , and  110 . The display device  1  can thus display captured images covering the length of the train  100  along the moving direction of the train  100 , so that one can easily recognize the relative positions and directions represented by the images. The produced display is suitable for the monitoring of the station platform by the user. A method will be described later in detail as to how to display the images captured by one of two oppositely pointing groups of cameras that is more suitable for monitoring. 
     Portion (b) of  FIG. 4  illustrates exemplary display in accordance with the present embodiment where an image  308  captured by the camera  112 , an image  309  captured by the camera  114 , and an image  310  captured by the camera  116  are arranged next to each other. These captured images  308 ,  309 , and  310  are captured on the other side of the train  100 , that is, on the side where the cameras  112 ,  113 ,  114 ,  115 ,  116 , and  117  shown in (c) of  FIG. 1  are installed. Each image shows the train  100  in the right and a station platform in the left. The captured image  308  and the captured image  309  further show a passenger  311  standing on the platform. The cameras  112 ,  114 , and  116  are pointed in the same direction. Each captured image  308 ,  309 , and  310  shows a near view in the bottom thereof and a distant view in the top thereof. All the captured images  308 ,  309 , and  310  hence share the same near-view-to-distant-view direction. 
     The display device  1  can thus display captured images covering the length of the train  100  along the moving direction of the train  100 , so that one can easily recognize the relative positions and directions represented by the images. The produced display is suitable for the monitoring of the station platform by the user. One should monitor boarding and alighting passengers on different sides of the carriages (train), depending on stations (one should monitor passengers on the side on which the doors are opened to allow passengers to board and alight, the train). The display device  1  is however capable of displaying suitable images for monitoring by the user regardless of on which side passengers board and alight the train, by displaying the images captured by the cameras installed on the side of the train that should be monitored as shown in (a) of  FIG. 3  and (b) of  FIG. 4 . 
       FIG. 5  illustrates an exemplary display of the captured images  301 ,  302 , and  303  arranged in an order in accordance with the present embodiment, Each captured image  301 ,  302 , and  303  shows a near view in the bottom thereof and a distant view in the top thereof. Note that in terms of the left-right direction, the images may be interpreted as showing a near view in the right and a distant view in the left because the images have a vanishing point (infinitely distant point in the perspective drawing) in the upper left. Therefore, the captured images  301 ,  302 , and  303 , when arranged in this order from the right to the left as shown in  FIG. 5 , show the distant view in each of the three captured images contiguously to the near view in a next one of the three captured images, so that one can easily recognize the relative positions and directions represented by the images. The produced display is suitable for the monitoring of the station platform by the user. 
     The display device  1 , which displays captured images, may be installed, for example, in the driver&#39;s cab so that the train driver can monitor the platform from the inside of the carriage or in a crew&#39;s cabin used by a conductor. As another alternative, the display device  1  may be installed, for example, on a station platform or in a room located in a prescribed location in a station. 
       FIG. 6  illustrates the display screen of the display device  1  in accordance with the present embodiment. Referring to (a) of  FIG. 6 , the display device  1  may display a plurality of images next to each other on a single display screen  501 . Alternatively, referring to (b) of  FIG. 6 , when there is provided a plurality of display screens  502 ,  503 , and  504  next to each other, the display device  1  may display the captured image  301  on the display screen  502 , the captured image  302  on the display screen  503 , and the captured image  303  on the display screen  504 . In other words, the images need only to be arranged such that the near and distant views in the images are displayed contiguously. 
     Advantages of Embodiment 1 
     As described in the above, there is provided a plurality of cameras with the same imaging direction substantially along a straight line on the sides of the train  100 . A plurality of images captured by the cameras is displayed such that the near and distant views in the captured images represent the same direction and that the near and distant views in the images appear contiguous. This configuration enables the images to be displayed at positions suitable for monitoring by the user. 
     When the train  100  is on a curved track, the cameras, installed on a plurality of carriages, are located on a curved line. The above-described advantages are achieved when the train  100  is on a curved track similarly to when the train  100  is on a straight track. The cameras therefore need only to be located on a substantially straight line when the train  100  is on a straight track. 
     Embodiment 2 
     A detailed description will be given next of a display device  1  in accordance with Embodiment 2 of the present invention with reference to  FIGS. 7 to 9 . The present embodiment produces a display that is more suitable for monitoring by taking into account the location of the user (e.g., the train driver, conductor, or station staff) who checks the displayed image(s). 
     Portion (a) of  FIG. 7  is a side view of a carriage  601  in accordance with the present embodiment. The carriage  601  has cameras  602  and  603  on a side thereof. The carriage  601 , which is the front car of the train  100 , has a driver&#39;s cab  604 . Carriages can move in both directions. Assume in this embodiment that the carriage  601  is moving in the direction indicated by an arrow  605  in  FIG. 7 . 
     Portion (b) of  FIG. 7  is a plan view of the carriage  601  in accordance with the present embodiment as the carriage  601  is viewed from above, Portion (b) of  FIG. 7  shows the carriage  601  and a station platform  606 . When the carriage  601  and the platform  606  are located in the relative positions shown in (b) of  FIG. 7 , a train driver (not shown) in the driver&#39;s cab  604  will find the platform  606  on his/her left-hand side if he/she is looking in the moving direction indicated by the arrow  605 . The train driver therefore will look at the left rear to visually check the platform  606 . 
     Referring to  FIG. 7 , the cameras  602  and  603  are disposed in locations where the cameras  602  and  603  can capture images of the left side of the carriage  601 . The camera  602  is pointed in the backward direction with respect to the carriage  601  to capture images in an imaging range  607  shown in (b) of  FIG. 7 . Meanwhile, the camera  603  is pointed in the forward direction with respect to the carriage  601 . The cameras  602  and  603  have an imaging range covering the platform  606 . Since the train driver monitors the left rear, the imaging direction of the camera  602  matches the visual monitoring direction of the train driver. The produced display therefore appears natural to the train driver. In contrast, the imaging direction of the camera  603  is opposite to the visual monitoring direction of the train driver. The produced display therefore appears less natural to the train driver than the display produced from the image captured by the camera  602 . Therefore, the image captured by the camera  602  is more suitable for the monitoring of the platform by the train driver. 
       FIG. 8  is a plan view of a train  700  in accordance with the present embodiment as the train  700  is viewed from above.  FIG. 8  shows the train  700  and a station platform  712 . The train  700  consists (primarily) of a set of coupled carriages  701 ,  702 , and  703 . The carriage  701  has a driver&#39;s cab  704 , and the carriage  703  has a driver&#39;s cab  705 . Each carriage is provided with cameras.  FIG. 8  shows only those cameras that are located on one of the sides of the car (i.e., those on the “lower” side of the car in  FIG. 8 ). The carriage  701  has cameras  706  and  707 , the carriage  702  has cameras  708  and  709 , and the carriage  703  has cameras  710  and  711 . The cameras  706 ,  708 , and  710  are positioned to have an imaging direction that matches the direction indicated by an arrow  714 . The cameras  707 ,  709 , and  711  are positioned to have an imaging direction that matches the direction indicated by an arrow  713 . 
     Assume that there are a train driver (not shown) in the driver&#39;s cab  704 , a conductor (not shown) in the driver&#39;s cab  705  and that both the train driver and the conductor monitor the platform  712 . The train driver looks in the direction indicated by the arrow  714  to check the platform  712 . Accordingly, the train driver can preferably view the images captured by the cameras  706 ,  708 , and  710  which have an imaging direction that matches the direction indicated by the arrow  714 . In contrast, the conductor looks in the direction indicated by the arrow  713  to check the platform  712 . Accordingly, the conductor can preferably view the images captured by the cameras  707 ,  709 , and  711  which have an imaging direction that matches the direction indicated by the arrow  713 . 
     In other words, there are provided two groups of cameras having opposing imaging directions substantially along a straight line on the carriages. The display device  1  then selectively displays, as monitoring images for the user, those images captured with an imaging direction that matches the near-view-to-distant-view direction when viewed from the location of the user such as the train driver or the conductor. 
     This configuration enables a display to be produced that is suitable for monitoring by the user. If the displayed images are to be selected on the basis of the location of the user, the images can be displayed at positions suitable for the monitoring by, as described in Embodiment 1, displaying the images such that the near and distant views in the images appear contiguous. 
       FIG. 9  is a plan view of a portion of a train  800  in accordance with the present embodiment as the train  800  is viewed from above.  FIG. 9  shows a portion of the train  800  and a station platform  811 . The train  800  consists (primarily) of a set of coupled carriages  801 ,  802 , and  803 . The carriage  802  has a crew&#39;s cabin  804 . Each carriage is provided with cameras.  FIG. 9  shows only those cameras that are located on one of the sides of the car (i.e., those on the “lower” side of the car in  FIG. 9 ). The carriage  801  has cameras  805  and  806 , the carriage  802  has cameras  807  and  808 , and the carriage  803  has cameras  809  and  810 . The cameras  805 ,  807 , and  809  are positioned to have an imaging direction that matches the direction indicated by an arrow  813 . The cameras  806 ,  808 , and  810  are positioned to have an imaging direction that matches the direction indicated by an arrow  812 . 
     Assume that there is a conductor (not shown) in the crew&#39;s cabin  804  and that the conductor monitors the platform  811 . The conductor monitors the platform  811  from the crew&#39;s cabin  804  (the location of the conductor). Accordingly, when the conductor looks in the direction indicated by the arrow  812  to monitor the left-hand side of the crew&#39;s cabin  804  (i.e., to monitor the platform  811  in the direction indicated by the arrow  812 ), the conductor can preferably view the image captured by the camera  806  which has an imaging direction that matches the direction indicated by the arrow  812 . In contrast, when the conductor looks in the direction indicated by the arrow  813  to monitor the right-hand side of the crew&#39;s cabin  804  (i.e., to monitor the platform  811  in the direction indicated by the arrow  813 ), the conductor can preferably view the images captured by the cameras  807  and  809  which have an imaging direction that matches the direction indicated by the arrow  813 . 
     Advantages of Embodiment 2 
     As described in the above, a display can be produced that is suitable for monitoring by the user by selectively displaying, as monitoring images for the user, those images captured with an imaging direction that matches the near-view-to-distant-view direction when viewed from the location of the user such as the conductor. In addition, when the user such as the conductor is somewhere between the front and the end of the train, a display can be produced that is suitable for the monitoring of both the forward direction and the backward direction by displaying, as monitoring images for the user, those images captured with an imaging direction that matches the near-view-to-distant-view direction when viewed from the location of the user, regardless of whether the user is looking in the forward direction or the backward direction as viewed from the location. If a plurality of images is to be displayed regardless of whether the user is either in the front or end of the train or somewhere between the front and end of the train, the images can be displayed at positions suitable for the monitoring by displaying the images such that the near and distant views in the images appear contiguous regardless of whether the user is looking in the forward direction or the backward direction. 
     Embodiment 3 
     A detailed description will be given next of a display device  1  in accordance with Embodiment 3 of the present invention with reference to  FIG. 10 . The present embodiment cuts out portions of images captured by the cameras installed on carriages, to display the cut-out portions. 
     Portion (a) of  FIG. 10  is a side view of a train  900  in accordance with the present embodiment as the train  900  is viewed from a side thereof. The train  900  consists (primarily) of a set of coupled carriages  901  and  902 . The carriage  901  has a driver&#39;s cab  903 . The carriage  901  has a camera  904 , and the carriage  902  has a camera  905 . Portion (a) of  FIG. 10  shows an imaging range  906  of the camera  904  and an imaging range  907  of the camera  905 . Referring to (a) of  FIG. 10 , the cameras  904  and  905  may be cameras with a wide angle of view such as cameras with a fisheye lens and may be cameras with a lens capable of imaging both the forward and backward directions. 
     A camera with a wide angle of view will capture an image covering large areas including and beyond the station platform to be monitored. Consequently, the captured image contains areas that do not need to be monitored by the user. Accordingly, in the present embodiment, the display device  1  cuts out portions of captured images to display images suitable for monitoring. 
     Specifically, the cameras  904  and  905  have an imaging range that includes the forward and backward directions with respect to the train  100 . In accordance with this configuration, if there is installed a camera on a carriage located forward of the carriage where the display device  1  is installed, the image processing unit  11  extracts portions corresponding to the forward direction with respect to the train  100  from the images captured by the cameras installed on the carriage located forward (from the images captured with an angle of view covering the front-back direction with respect to the train  100 ). If there is installed a camera on a carriage located backward the carriage where the display device  1  is installed, the image processing unit  11  extracts portions corresponding to the backward direction with respect to the train  100  from the images captured by the cameras installed on the carriage located backward (from the images captured with an angle of view covering the front-back direction with respect to the train  100 ). The image processing unit  11  generates a display image on the basis of the extracted portions of the images. 
     The display device  1  cuts out images containing an area to be monitored from captured images in such a manner that the cut-out images share the same near-view-to-distant-view direction and displays the cut-out images such that the near and distant views in the images appear contiguous. 
     In other words, when the display image is to include a plurality of images, the image processing unit  11  arranges the images in such a manner that the carriages where the cameras capturing the images are installed appear lined up along a specific direction in the approaching order when viewed from the carriage where the display device  1  is installed. The specific direction is parallel to the direction from the distant view to the near view in each image. 
     Portion (b) of  FIG. 10  is a side view of the train  900  in accordance with the present embodiment as the train  900  is viewed from a side thereof, similarly to (a) of  FIG. 10 . Portion (b) of  FIG. 10  shows a display area  909  cut out, from the imaging range  906  of the camera  904  and a display area  910  cut out from the imaging range  907  of the camera  905 . The display area  909  and the display area  910  cover the same direction. Accordingly, the display device  1  displays the display area  909  and the display area  910  by arranging the display area  909  and the display area  910  in such a manner that the near and distant views in the images appear contiguous. 
     When portions are cut out from wide-angle-of-view images shown in (a) of  FIG. 10  for display, the display device  1  similarly produces a display by taking the location of the user into account. This configuration produces a more suitable display for monitoring by the user. In (b) of  FIG. 10 , a train driver (not shown) in the driver&#39;s cab  903  monitors in the direction indicated by an arrow  908 . Accordingly, the display device  1  cuts out portions of the wide-angle-of-view images in such a manner that the near-view-to-distant-view direction in the portions of the images matches the direction indicated by the arrow  908 . 
     Advantages of Embodiment 3 
     As described in the above, the display device  1  is capable of producing a suitable display for monitoring by the user by arranging and displaying a plurality of cut-out display areas in such a manner that the near and distant views in the images appear contiguous. The display device  1  is also capable of producing a suitable display for monitoring by the user by cutting out portions of wide-angle-of-view captured images in such a manner that the near-view-to-distant-view direction in the portions of the images matches the direction in which the user monitors the platform, because the direction in which the user visually checks the platform matches the near-view-to-distant-view direction in the cut-out portions of the images. 
     Embodiment 4 
     A detailed description will be given next of a display device  1  in accordance with Embodiment 4 of the present invention with reference to  FIGS. 11 to 13 . The present embodiment displays a captured image and an overhead view of a vicinity of the carriage next to each other to produce a more suitable display for monitoring. 
       FIG. 11  illustrates a display screen  1000  of the display device  1  in accordance with the present embodiment. The display device  1  displays an overhead view of a train  1001  on the display screen  1000  as the train  1001  is viewed from above. The train  1001  consists (primarily) of a set of coupled carriages  1002 ,  1003 , and  1004 . The carriage  1002  has a driver&#39;s cab  1008 . The carriage  1002  has a camera  1005 , the carriage  1003  has a camera  1006 , and the carriage  1004  has a camera  1007 . All the cameras are positioned to point and capture images in the left-hand side of  FIG. 11 . 
     The display device  1  displays an image  1009  captured by the camera  1005 , an image  1010  captured by the camera  1006 , and an image  1011  captured by the camera  1007  on the display screen  1000 . The display device  1  then displays the image  1009  above the carriage  1002 , the image  1010  above the carriage  1003 , and the image  1011  above the carriage  1004 . Thus, the display device  1  produces a display in which the positions of the carriages and cameras are associated with the positions of the images captured by the cameras. 
     The display method illustrated in  FIG. 11  not only associates the relative positions of the carriages, cameras, and images, but also gives the same near-view-to-distant-view direction for the three images in such a manner that near and distant views in the images appear contiguous. Owing to these features, the display method produces a suitable display for monitoring by the user. The display method illustrated in  FIG. 11  is also suitable for recognizing the left and right sides of the train. 
     The captured images  1009 ,  1010 , and  1011  are all captured by cameras installed on the left side of the train  1001  (the left side of the carriages assuming that the cars move to the right in  FIG. 11 ). Since the captured images  1009 ,  1010 , and  1011  are displayed to the left of the train  1001  (in the top of  FIG. 11 ) on the display screen  1000 , the left-right positions in the captured images with respect to the carriages match the display positions of the images with respect, to the overhead view of the carriages. Therefore, the user can easily recognize the left-right positions in the displayed image. One should monitor boarding and alighting passengers on different sides of the carriages, depending on stations. This display, which enables the user to easily recognize which side of the carriages is being displayed, is suitable for monitoring by the user. 
     In addition, the display screen  1000  displays an imaging range  1012  of the camera  1005 , an imaging range  1013  of the camera  1006 , and an imaging range  1014  of the camera  1007  superimposed on the overhead view of the respective carriages. The user can hence easily recognize which part of the vicinity of the car is being represented by each of the captured images  1009 ,  1010 , and  1011 . A description will be given next of a display method used when one should monitor different (left and right) sides of the carriages. Portion (a) of  FIG. 12  illustrates a display image  1100  for monitoring the left side of carriages in accordance with the present embodiment when the train is moving to the right in the figure. Meanwhile, portion (b) of  FIG. 12  illustrates a display image  1101  for monitoring the right side of the carriages in accordance with the present embodiment when the train is moving to the right in the figure. In (a) of  FIG. 12 , captured images are displayed in the top, and an overhead view of a train is displayed in the bottom. In other words, captured images are displayed on the monitored side (the left side of the carriages). Meanwhile, in (b) of  FIG. 12 , captured images are displayed in the bottom, and an overhead view of the train is displayed on the top. In other words, captured images are displayed on the monitored side (the right side of the carriages). The display positions of the captured images and the overhead view of the train are switched in accordance with the monitored side of the train, as shown in (a) and (b) of  FIG. 12 . 
     Portion (a) of  FIG. 13  illustrates an overhead view of a train and camera-captured images being displayed on a display screen  1200  in accordance with the present embodiment. Portion (b) of  FIG. 13  illustrates an overhead view of a train and camera-captured images being displayed on a display screen  1201  in accordance with the present embodiment. 
     Refilling to (a) and (b) of  FIG. 13 , the overhead view of the train is displayed in the same position on the display screen  1200  and on the display screen  1201 . In other words, when the display screen  1200  and the display screen  1201  are compared, the position of the overhead view of the train is not changed on the display device  1 , whereas the display position of the captured images is changed on the display device  1  in accordance with which of the left and right sides of the carriages should be monitored. 
     Advantages of Embodiment 4 
     As described in the above, the display device  1  is capable of producing a suitable display for monitoring by the user by associating the positions of the carriages and cameras with the positions of the images captured by the cameras in such a manner that the user can easily recognize which part of the train is represented by each display image. The display device  1  is suitably capable of producing such a display that the user can easily recognize the left-right positions since the display device  1  always displays captured images on the side of the overhead view of the carriages to be monitored, by switching the display position of the overhead view of the train and the display position of the captured images in accordance with which side of the train is to be monitored. The display device  1  is capable of producing a suitable display for monitoring by the user by changing the display position of captured images in accordance with which of the left and right sides of the carriages should be monitored in such a manner that the user can easily recognize the left-right positions with respect to the carriages. 
     Embodiment 5 
     A detailed description will be given next of a display device  1  in accordance with Embodiment 5 of the present invention with reference to  14 .  FIG. 14  illustrates an overhead view of a train and camera-captured images being displayed on a display screen  1300  in accordance with the present embodiment. 
     The display device  1  displays on the display screen  1300  an overhead view of a train  1301  as the train  1301  is viewed from above as shown in  FIG. 14 . The train  1301  consists (primarily) of a set of coupled carriages  1302 ,  1303 , and  1304 . The carriage  1302  has a camera  1305 , the carriage  1303  has a camera  1306 , and the carriage  1304  has a camera  1307 . All the cameras are positioned to point and capture images in the left-hand side of  FIG. 14 . 
     The display device  1  displays an image  1309  captured by the camera  1305 , an image  1310  captured by the camera  1306 , and an image  1311  captured by the camera  1307  on the display screen  1300 . The display device  1  then displays the image  1309  above the carriage  1302 , the image  1310  above the carriage  1303 , and the image  1311  above the carriage  1304  on the display screen  1300 . 
     The display device  1  displays over the image  1309  a detection frame  1312  that represents the detection of a person in the image  1309 . The display device  1  further displays over the image  1311  a detection frame  1313  that represents the detection of a person in the image  1311 . The display device  1  then displays in the overhead view of the train  1301  a detection point  1314  that represents the location corresponding to the detection frame  1312  and a detection point  1315  that represents the location corresponding to the detection frame  1313 . 
     Advantages of Embodiment 5 
     As described in the above, the display device  1  is capable of producing a suitable display for monitoring by the user by displaying the location of a person in an overhead view in such a manner that the user can easily recognize where the person shown in the image is on the station platform. 
     Embodiment 6 
     A detailed description will be given next of a display device  1  in accordance with Embodiment 6 of the present invention with reference to  FIGS. 15 and 16 . 
       FIG. 15  illustrates an overhead view of a train and camera-captured images being displayed on a display screen  1400  in accordance with the present embodiment. 
     The display device  1  displays on the display screen  1400  an overhead view of a train  1401  as the train  1401  is viewed from above as shown in  FIG. 15 . The train  1401  consists (primarily) of a set of coupled carriages  1402 ,  1403 ,  1404 ,  1405 ,  1406 , and  1407 . The carriage  1402  has a camera  1408 , the carriage  1404  has a camera  1409 , and the carriage  1406  has a camera  1410 . All the cameras are positioned to point and capture images in the left-hand side of  FIG. 15 . 
     The display device  1  displays on the display screen  1400  an image  1411  captured by the camera  1408 , an image  1412  captured by the camera  1409 , and an image  1413  captured by the camera  1410 . The display device  1  further displays an imaging range  1414  of the camera  1408 , an imaging range  1415  of the camera  1409 , and an imaging range  1416  of the camera  1410  in the overhead view of the train  1401 . 
     Referring to  FIG. 15 , a carriage provided with a camera and a carriage provided with no camera are alternately coupled in the train  1401 . The number of carriages does not match the number of cameras. However, the camera  1408  captures images on and near a side of the carriages  1402  and  1403 , the camera  1409  captures images on and near a side of the carriages  1404  and  1405 , and the camera  1410  captures images on and near a side of the carriages  1406  and  1407 . One can therefore monitor an entire side of the train  1401  using the three cameras. 
     The cameras  1408 ,  1409 , and  1410  are all located substantially along a straight line and pointed in such a direction as to share the same imaging direction, similarly to the configuration where each carriage has a camera. The display device  1  displays the images  1411 ,  1412 , and  1413  in such a manner that the images  1411 ,  1412 , and  1413  share the same near-view-to-distant-view direction and the near and distant views in the images appear contiguous. This configuration enables a display of a plurality of images in suitable locations for monitoring by the user. If the train  1401  includes a carriage that has no camera, a portion of an image captured by a camera installed on another carriage may be cut out for display. 
       FIG. 16  illustrates an overhead view of a train and camera-captured images being displayed on a display screen  1500  in accordance with the present embodiment. The composition of the train and the layout and imaging ranges of the cameras on the display screen  1500  are the same as those on the display screen  1400  in  FIG. 15 . The display screen  1500  differs from the display screen  1400  in how captured images are displayed. 
     Referring to  FIG. 16 , the display device  1  displays on the display screen  1500  an image  1511  obtained by cutting out a part of the captured image  1411  that corresponds to the carriage  1403 , an image  1512  obtained by cutting out a part of the captured image  1412  that corresponds to the carriage  1405 , and an image  1513  obtained by cutting out a part of the captured image  1413  that corresponds to the carriage  1407 , as well as the images  1411 ,  1412 , and  1413  captured by the cameras  1408 ,  1409 , and  1410 . The display device  1  may scale up the images  1511 ,  1512 , and  1513  approximately to the size of the captured images  1411 ,  1412 , and  1413  before displaying them as shown in  FIG. 16 . 
     Advantages of Embodiment 6 
     As described in the above, the display device  1  is capable of displaying images in suitable locations for monitoring by the user even when there is a carriage that has no camera. The display device  1  is also capable of producing a suitable display for monitoring by the user by cutting out and displaying an image corresponding to a carriage that has no camera in such a manner that an image is displayed for each carriage, which helps the user recognize the relationship between the imaging ranges for the images and the locations of the carriages. 
     General Description 
     The present invention, in aspect 1 thereof, is directed to a display device ( 1 ) installed on a train ( 100 ) including a plurality of carriages on at least one of which an imaging device (camera  106 ) is installed, the display device including: an image processing unit ( 11 ) configured to generate a display image based on an image captured by the imaging device and on relative positions of the carriage on which the imaging device is installed and a carriage on which the display device is installed; and a display unit ( 12 ) configured to display the display image generated by the image processing unit. 
     According to this structure and configuration, the display image is generated and displayed based on the images captured by the imaging devices and on the relative positions of the carriages on which the imaging devices are installed and the carriage on which the display device is installed. A display of the train and a vicinity thereof can be hence produced in a manner suitable for monitoring. 
     In aspect 2 of the present invention, the display device of aspect 1 may be configured such that the imaging device includes an imaging device with an imaging range covering a forward direction with respect to the train and an imaging device with an imaging range covering a backward direction with respect to the train, and the image processing unit, if the imaging device is installed on a carriage located forward of the carriage on which the display device is installed, selects an image captured by the imaging device installed on the carriage located forward, the selected image being captured by the imaging device with an imaging range covering the forward direction, and if the imaging device is installed on a carriage located backward of the carriage on which the display device is installed, selects an image captured by the imaging device installed on the carriage located backward, the selected image being captured by the imaging device with an imaging range covering the backward direction, and generates the display image based on the selected image. 
     According to this structure and configuration, if there is an imaging device installed on a carriage located either forward or backward of the carriage on which the display device is installed, an image captured by the imaging device with an imaging range covering that direction is selected for display from the images captured by the imaging device installed on the carriage located in the direction. A display of the train and a vicinity thereof can be hence produced in a manner suitable for monitoring. 
     In aspect 3 of the present invention, the display device of aspect 1 may be configured such that the imaging device has an imaging range covering a forward direction and a backward direction with respect to the train, and the image processing unit, if the imaging device is installed on a carriage located forward of the carriage on which the display device is installed, extracts a range corresponding to the forward direction with respect to the train from an image captured by the imaging device installed on the carriage located forward, and if the imaging device is installed on a carriage located backward of the carriage on which the display device is installed, extracts a range corresponding to the backward direction with respect to the train from an image captured by the imaging device installed on the carriage located backward, and generates the display image based on the extracted range of the image. 
     According to this structure and configuration, if there is an imaging device installed on a carriage located either forward or backward of the carriage on which the display device is installed, a range corresponding to that direction with respect to the train is extracted for display from the image captured by the imaging device installed on the carriage located in the direction. A display of the train and a vicinity thereof can be hence produced in a manner suitable for monitoring. 
     In aspect 4 of the present invention, the display device of aspect 1 may be configured such that the image processing unit, if the imaging device is installed on a carriage located forward of the carriage on which the display device is installed, controls the imaging device installed on the carriage located forward to have an imaging range covering the forward direction with respect to the train, and if the imaging device is installed on a carriage located backward of the carriage on which the display device is installed, controls the imaging device installed on the carriage located backward to have an imaging range covering the backward direction with respect to the train, and generates the display image based on an image captured by the controlled imaging device. 
     According to this structure and configuration, if there is an imaging device installed on a carriage located either forward or backward of the carriage on which the display device is installed, the imaging device installed on the carriage located in that direction is controlled to have an imaging range covering the direction with respect to the train in producing a display. A display of the train and a vicinity thereof can be hence produced in a manner suitable for monitoring. 
     In aspect 5 of the present invention, the display device of any one of aspects 1 to 4 may be configured such that the image processing unit arranges a plurality of images in the display image in such a manner that carriages on which imaging devices capturing the images are installed appear lined up along a specific direction in an approaching order when viewed from the carriage on which the display device is installed, and the specific direction is parallel to a direction from a distant view to a near view in each image. 
     According to this structure and configuration, the image processing unit arranges a plurality of images in the display image in such a manner that carriages on which imaging devices capturing the images are installed appear lined up along a specific direction in an approaching order when viewed from the carriage on which the display device is installed, and the specific direction is parallel to a direction from a distant view to a near view in each image. A display of the train and a vicinity thereof can be hence produced in a manner suitable for monitoring. 
     The present invention, in aspect 6 thereof, is directed to an imaging and display system (display system  50 ) including: the display device of any one of aspects 1 to 5; and the imaging device. 
     The present invention, in aspect 7 thereof, is directed to a train including: the display device of any one of aspects 1 to 5; and the imaging device. 
     The present invention is not limited to the description of the embodiments above and may be altered within the scope of the claims. Embodiments based on a proper combination of technical means disclosed in different embodiments are encompassed in the technical scope of the present invention. Furthermore, new technological features can be created by combining different technological means disclosed in the embodiments.