Patent Publication Number: US-2015077281-A1

Title: Dump truck

Description:
FIELD 
     The present invention relates to a dump truck that includes a periphery monitoring system for monitoring the periphery and is used in a mine. 
     BACKGROUND 
     Various mining machines, such as a dump truck and an excavator, operate in a working site or a quarry site of a mine. Since the width and length of a dump truck used in a mine are significantly larger than those of a general vehicle, it is difficult for an operator to check a situation around the dump truck and take in a situation around the dump truck by side view mirrors and the like. For this reason, there is proposed a device that monitors the periphery of a vehicle, as a technique that supports driving by making a driver or an operator easily take in a situation around a vehicle. As such a device for monitoring the periphery, there is, for example, a device for forming an image, which shows the periphery of a vehicle, by imaging the periphery of a vehicle by using cameras and the like mounted on the vehicle and synthesizing the obtained images (for example, Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent Application Laid-open No. 03-099952 
       
    
     SUMMARY 
     Technical Problem 
     A dump truck used in a mine forms a shadow by oneself. Since a dump truck used in a mine is very large, a difference in the contrast of light and shade between a bright portion (sunny spot), which is irradiated with sunlight, and a shadow (shady spot) that is formed by the dump truck itself is large. In this case, if an object such as a vehicle is present in the shadow formed by the dump truck, a dark portion (a black portion) of an image taken by an imaging device collapses, so that there is a possibility that the vehicle or the like present in the shadow portion may not be recognized. Since this is not considered in Patent Literature 1, there is a room for improvement. 
     An object of the invention is to display vehicles or other objects, which are present around a dump truck, on an image even in an environment where a difference in the contrast of light and shade is large when monitoring the periphery of the dump truck by using images taken by imaging devices. 
     Solution to Problem 
     According to the present invention, a dump truck comprises: a vehicle body portion that includes an upper deck on which a cab is disposed and a frame which is disposed in a longitudinal direction; a vessel that is disposed above the frame; and a rear wide dynamic range camera that is disposed below the vessel at a rear end of the frame and images a rear side of the vehicle body portion. 
     In the present invention, it is preferable that the dump truck further comprises: a front wide dynamic range camera that is disposed on a front portion of the upper deck and images a front side of the vehicle body portion; side wide dynamic range cameras that are disposed on left and right side portions of the upper deck, respectively, and image areas between an oblique front side and the rear side of the vehicle body portion; and a monitoring control device that monitors a periphery of the vehicle body portion by using a bird&#39;s-eye image formed by combination of images obtained by the rear wide dynamic range camera, the front wide dynamic range camera, and the respective side wide dynamic range cameras. 
     In the present invention, it is preferable that the side wide dynamic range cameras include a first side wide dynamic range camera that images the oblique front side of the vehicle body portion, and a second side wide dynamic range camera that images an oblique rear side of the vehicle body portion. 
     In the present invention, it is preferable that the dump truck further comprises: a plurality of radar devices that are provided on the vehicle body portion and detect objects present in an entire peripheral range of the vehicle body portion. 
     According to the present invention, a dump truck comprises: a vehicle body portion that includes an upper deck on which a driver&#39;s seat is disposed and a frame which is disposed in a longitudinal direction; a vessel that is disposed above the frame; a rear wide dynamic range camera that is disposed below the vessel at a rear end of the frame and images a rear side of the vehicle body portion; a front wide dynamic range camera that is disposed on a front portion of the upper deck and images a front side of the vehicle body portion; side wide dynamic range cameras that are disposed on left and right side portions of the upper deck, respectively, and image areas between an oblique front side and the rear side of the vehicle body portion; a monitoring control device that monitors a periphery of the vehicle body portion by using a bird&#39;s-eye image formed by combination of images obtained by the rear wide dynamic range camera, the front wide dynamic range camera, and the respective side wide dynamic range cameras; and a monitor that is disposed in the cab and displays the bird&#39;s-eye image. 
     The invention can display vehicles or other objects, which are present around a dump truck, on an image even in an environment where a difference in the contrast of light and shade is large when monitoring the periphery of the dump truck by using images taken by imaging devices. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating a dump truck according to this embodiment. 
         FIG. 2  is a view illustrating the structure of a cab of the dump truck according to this embodiment. 
         FIG. 3  is a view illustrating a periphery monitoring system according to this embodiment. 
         FIG. 4  is a perspective view illustrating the dump truck on which imaging devices of the periphery monitoring system according to this embodiment are mounted. 
         FIG. 5  is a schematic view illustrating a bird&#39;s-eye image that is created on the basis of information on images taken by a plurality of imaging devices and areas that are imaged by a plurality of imaging devices. 
         FIG. 6  is a perspective view illustrating the disposition of radar devices. 
         FIG. 7  is a view illustrating an image converting method using a virtual projection plane. 
         FIG. 8  is a plan view illustrating a relation between the dump truck and a vehicle that is present around the dump truck. 
         FIG. 9  is a front view illustrating the relation between the dump truck and the vehicle that is present around the dump truck. 
         FIG. 10  is a view illustrating an example of an imaging device to which a wide dynamic range camera is applied. 
         FIG. 11  is a view illustrating an imaging range of the imaging device of the periphery monitoring system according to this embodiment in a height direction. 
         FIG. 12  is a view illustrating the imaging range of the imaging device of the periphery monitoring system according to this embodiment in the height direction. 
         FIG. 13  is a view illustrating the imaging ranges of the imaging devices of the periphery monitoring system according to this embodiment in the height direction. 
         FIG. 14  is a view illustrating a case where a vehicle moves around the dump truck. 
         FIG. 15  is a view illustrating a case where a vehicle moves around the dump truck. 
         FIG. 16  is a view illustrating a case where a vehicle moves around the dump truck. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the invention will be described in detail with reference to the drawings. The invention is not limited by the content disclosed in the following embodiment. In the following description, front, rear, left, and right are terms based on an operator seated in a driver&#39;s seat. A vehicle width direction has the same meaning as a lateral direction. 
     &lt;Dump Truck&gt; 
       FIG. 1  is a perspective view illustrating a dump truck according to this embodiment.  FIG. 2  is a view illustrating the structure of a cab of the dump truck according to this embodiment. In this embodiment, a dump truck (referred to as an off-highway truck)  1  is a self-traveling extra large vehicle that is used for a work in a mine, and the like. The dump truck  1  includes a vehicle body portion  2 , a cab  3 , a vessel  4 , front wheels  5 , and rear wheels  6 . The vehicle body portion  2  includes an upper deck  2   b  and a frame  2   f  that is disposed along a longitudinal direction. Further, the dump truck  1  includes a periphery monitoring system that monitors its own peripheral area and displays the result of the monitoring. The detail of the periphery monitoring system will be described below. 
     In this embodiment, the dump truck  1  drives an electric motor by electric power, which is generated by the drive of a generator performed by an internal combustion engine such as a diesel engine, and drives the rear wheels  6 . The dump truck  1  uses a so-called electric drive system as described above, but the drive system of the dump truck  1  is not limited thereto. For example, the dump truck  1  may transmit power of an internal combustion engine to the rear wheels  6  through a transmission in order to drive the rear wheels  6 , and may drive an electric motor by power supplied from an overhead wire through a trolley in order to drive rear wheels  6  by the electric motor. 
     The frame  2   f  supports power generating mechanisms, such as an internal combustion engine and a generator, and auxiliary equipment thereof. Left and right front wheels  5  (only a right front wheel is illustrated in  FIG. 1 ) are supported at the front portions of the frame  2   f . Left and right rear wheels  6  (only a right rear wheel is illustrated in  FIG. 1 ) are supported at the rear portion of the frame  2   f . The diameter of each of the front and rear wheels  5  and  6  is about 2 to 4 m (meter). The frame  2   f  includes a lower deck  2   a  and the upper deck  2   b . As described above, the dump truck  1  used in a mine has a double-deck structure that includes the lower deck  2   a  and the upper deck  2   b.    
     The lower deck  2   a  is mounted on the lower portions of the front surface of the frame  2   f . The upper deck  2   b  is disposed above the lower deck  2   a . A movable ladder  2   c , which is used when an operator climbs up to the cab  3 , is disposed below the lower deck  2   a . An inclined ladder  2   d , which is used when an operator goes up and down between the lower deck  2   a  and the upper deck  2   b , is disposed between the lower deck  2   a  and the upper deck  2   b . Further, a radiator is disposed between the lower deck  2   a  and the upper deck  2   b . A fence-like handrail  2   e  is disposed on the upper deck  2   b . In this embodiment, the ladder  2   c  and the inclined ladder  2   d  are a part of the upper deck  2   b  and the lower deck  2   a.    
     As illustrated in  FIG. 1 , the cab  3  is disposed on the upper deck  2   b . The cab  3  is disposed on the upper deck  2   b  so as to be shifted to one side from the middle in the vehicle width direction. Specifically, the cab  3  is disposed on the upper deck  2   b  on the left side from the middle in the vehicle width direction. As illustrated in  FIG. 2 , the cab  3  includes a ROPS (Roll-Over Protection System) that includes a plurality of (four in this embodiment) pillars  3   a ,  3   b ,  3   c , and  3   d . The ROPS protects an operator present in the cab  3  if the dump truck  1  rolls over. A driver of the dump truck  1  drives the dump truck in a state where the driver can easily check the shoulder of a road that is positioned on the left side of the vehicle body portion  2 . However, the driver needs to significantly move one&#39;s head in order to check the peripheral area of the vehicle body portion  2 . Further, a plurality of side view mirrors (not illustrated) is provided on the upper deck  2   b  in order to check the peripheral area of the dump truck  1 . Since these side view mirrors are disposed at the positions distant from the cab  3 , the driver needs to significantly move one&#39;s head even when the driver checks the periphery of the vehicle body portion  2  with the side view mirrors. 
     As illustrated in  FIG. 2 , a driver&#39;s seat  31 , a steering wheel  32 , a dash cover  33 , a wireless device  34 , a radio receiver  35 , a retarder  36 , a shift lever  37 , a trainer&#39;s seat  38 , a controller (of which the detail will be described below) serving as a monitoring control device not illustrated in  FIG. 2 , a monitor  50 , an accelerator pedal, a brake pedal, and the like are provided in the cab  3 . Meanwhile, the controller not illustrated in  FIG. 2  and the monitor  50  are a part of a periphery monitoring system  10  to be described below. 
     The vessel  4  illustrated in  FIG. 1  is a container into which freight such as broken stone is loaded. The rear portion of the bottom of the vessel  4  is rotatably connected to the rear portion of the frame  2   f  by a rotating pin. The vessel  4  can take a loading posture and an upright posture by an actuator such as a hydraulic cylinder. The loading posture is a posture where the front portion of the vessel  4  is positioned above the cab  3  as illustrated in  FIG. 1 . The upright posture is a posture where freight is discharged, and is a posture where the vessel  4  is inclined rearward and downward. When the front portion of the vessel  4  is rotated upward, the vessel  4  is changed into the upright posture from the loading posture. The vessel  4  includes a flange portion  4 F at the front thereof. The flange portion  4 F extends to the upper side of the cab  3  and covers the cab  3 . The flange portion  4 F, which extends to the upper side of the cab  3 , protects the cab  3  from the collision of broken stone and the like. 
     &lt;Periphery Monitoring System&gt; 
       FIG. 3  is a view illustrating the periphery monitoring system according to this embodiment.  FIG. 4  is a perspective view illustrating the dump truck on which imaging devices of the periphery monitoring system according to this embodiment are mounted.  FIG. 5  is a schematic view illustrating a bird&#39;s-eye image that is created on the basis of information on images taken by a plurality of imaging devices and areas that are imaged by a plurality of imaging devices. Areas, which are illustrated in  FIG. 5  and are imaged by a plurality of imaging device, are areas based on the ground. The periphery monitoring system  10  includes a plurality of (six in this embodiment) imaging devices  11 ,  12 ,  13 ,  14 ,  15 , and  16 , a plurality of (eight in this embodiment) radar devices  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 , and  28 , the monitor  50 , and a controller  100  serving as a monitoring control device. Meanwhile, in this embodiment, the periphery monitoring system  10  does not necessarily require the radar devices  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 , and  28 . 
     &lt;Imaging Device&gt; 
     The imaging devices  11 ,  12 ,  13 ,  14 ,  15 , and  16  are mounted on the dump truck  1 . The imaging devices  11 ,  12 ,  13 ,  14 ,  15 , and  16  are cameras using, for example, a CCD (Charge Coupled Device). The imaging devices  11 ,  12 ,  13 ,  14 ,  15 , and  16  image the peripheral areas of the dump truck  1  and output the images as image information. In the following description, appropriately, the imaging device  11  is referred to as a first imaging device  11 , the imaging device  12  is referred to as a second imaging device  12 , the imaging device  13  is referred to as a third imaging device  13 , the imaging device  14  is referred to as a fourth imaging device  14 , the imaging device  15  is referred to as a fifth imaging device  15 , and the imaging device  16  is referred to as a sixth imaging device  16 . Further, when these do not need to be distinguished from each other, these are appropriately referred to as the imaging devices  11  to  16 . 
     As illustrated in  FIG. 4 , the six imaging devices  11  to  16  are mounted on the outer peripheral portions of the dump truck  1 , respectively, in order to image the range corresponding to 360° around the dump truck  1 . In this embodiment, each of the imaging devices  11  to  16  has a viewing range of 120° in the lateral direction (60° on each of the right and left sides) and a viewing range of 96° in a height direction, but the viewing ranges are not limited thereto. 
     As illustrated in  FIG. 4 , the first imaging device  11  is mounted on the front surface of the dump truck  1 . Specifically, the first imaging device  11  is disposed at the upper end portion of the inclined ladder  2   d , more specifically, at the lower portion of the top landing portion. The first imaging device  11  is fixed by a bracket, which is mounted on the upper deck  2   b , so as to face the front side of the dump truck  1 . As illustrated in  FIG. 5 , the first imaging device  11  images a first area  11 C of areas present around the dump truck  1  and outputs first image information serving as image information. The first area  11 C is an area that spreads out to the front side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 4 , the second imaging device  12  is mounted on one side portion of the front surface of the dump truck  1 . Specifically, the second imaging device  12  is disposed on the right side portion of the front surface of the upper deck  2   b . The second imaging device  12  is fixed by a bracket, which is mounted on the upper deck  2   b , so as to face the oblique front right side of the dump truck  1 . As illustrated in  FIG. 5 , the second imaging device  12  images a second area  12 C of areas present around the dump truck  1  and outputs second image information serving as image information. The second area  12 C is an area that spreads out to the oblique front right side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 4 , the third imaging device  13  is mounted on the other side portion of the front surface of the dump truck  1 . Specifically, the third imaging device  13  is disposed on the left side portion of the front surface of the upper deck  2   b . Further, the third imaging device  13  is disposed so as to be symmetrical to the second imaging device  12  with respect to an axis that passes through the middle of the dump truck  1  in a width direction. The third imaging device  13  is fixed by a bracket, which is mounted on the upper deck  2   b , so as to face the oblique front left side of the dump truck  1 . As illustrated in  FIG. 5 , the third imaging device  13  images a third area  13 C of areas present around the dump truck  1  and outputs third image information serving as image information. The third area  13 C is an area that spreads out to the oblique front left side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 4 , the fourth imaging device  14  is mounted on one side surface of the dump truck  1 . Specifically, the fourth imaging device  14  is disposed on the front portion of the right side surface of the upper deck  2   b . The fourth imaging device  14  is fixed by a bracket, which is mounted on the upper deck  2   b , so as to face the oblique rear right side of the dump truck  1 . As illustrated in  FIG. 5 , the fourth imaging device  14  images a fourth area  14 C of areas present around the dump truck  1  and outputs fourth image information serving as image information. The fourth area  14 C is an area that spreads out to the oblique rear right side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 4 , the fifth imaging device  15  is mounted on the other side surface of the dump truck  1 . Specifically, the fifth imaging device  15  is disposed on the front portion of the left side surface of the upper deck  2   b . Further, the fifth imaging device  15  is disposed so as to be symmetrical to the fourth imaging device  14  with respect to an axis that passes through the middle of the dump truck  1  in the width direction. As illustrated in  FIG. 5 , the fifth imaging device  15  images a fifth area  15 C of areas present around the dump truck  1  and outputs fifth image information serving as image information. The fifth area  15 C is an area that spreads out to the oblique rear left side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 4 , the sixth imaging device  16  is mounted on the rear portion of the dump truck  1 . Specifically, the sixth imaging device  16  is disposed on the rear end of the frame  2   f  above an axle housing, which connects two rear wheels  6  and  6 , near a rotating shaft of the vessel  4 . The sixth imaging device  16  is fixed by a bracket, which is mounted on a cross bar connecting the left and right portions of the frame  2   f , so as to face the rear side of the dump truck  1 . As illustrated in  FIG. 5 , the sixth imaging device  16  images a sixth area  16 C of areas present around the dump truck  1  and outputs sixth image information serving as image information. The sixth area  16 C is an area that spreads out to the rear side of the vehicle body portion  2  of the dump truck  1 . 
     The periphery monitoring system  10  according to this embodiment can acquire image information by imaging the entire peripheral area, which corresponds to 360°, of the dump truck  1  with the above-mentioned six imaging devices  11  to  16  as illustrated at the center of  FIG. 5 . The six imaging devices  11  to  16  send the first to sixth image information, which serve as the image information acquired by the respective imaging devices, to the controller  100  illustrated in  FIG. 3 . 
     The first imaging device  11 , the second imaging device  12 , the third imaging device  13 , the fourth imaging device  14 , and the fifth imaging device  15  are provided on the upper deck  2   b  that is at a relatively high position. For this reason, the controller  100  can obtain images, which are obtained when a driver looks down upon the ground from above, by the first to fifth imaging devices  11  to  15 , and can extensively image objects such as vehicles present on the ground. Further, even though a visual point is changed when a bird&#39;s-eye image  200  is created from the first to sixth image information acquired by the first to sixth imaging devices  11  to  16 , the controller  100  can suppress the degree of the deformation of a three-dimensional object since the first to fifth image information among them are information that are obtained when an image is taken from above. 
     &lt;Radar Device&gt; 
       FIG. 6  is a perspective view illustrating the disposition of the radar devices. In this embodiment, each of the radar devices  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 , and  28  (hereinafter, appropriately referred to as radar devices  21  to  28 ) is a UWB (Ultra Wide Band) radar (Ultra Wide Band radar) of which the range corresponds to ±80° (40° on each of the right and left sides) and a detection distance is a maximum of 15 m or more. The radar devices  21  to  28  detect relative positions between objects, which are present around the dump truck  1 , and the dump truck  1 . Like the imaging devices  11  to  16 , the radar devices  21  to  28  are mounted on the outer peripheral portions of the dump truck  1 . 
     As illustrated in  FIG. 6 , the radar device  21  (appropriately referred to as a first radar device  21 ) is disposed on the front surface of the vehicle body portion  2  at the lower deck  2   a , which is disposed at a height of about 1 m from the ground, slightly on the right side from the middle of the vehicle body portion  2  in the width direction. The detection range of the first radar device  21  is a range that spreads out to the oblique front left side from the front side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 6 , the radar device  22  (appropriately referred to as a second radar device  22 ) is disposed on the front surface of the vehicle body portion  2  at the lower deck  2   a  slightly on the left side from the middle of the vehicle body portion  2  in the width direction. That is, the second radar device  22  is disposed on the left side of the first radar device  21  so as to be adjacent to the first radar device  21 . The detection range of the first radar device  21  is a range that spreads out to the oblique front right side from the front side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 6 , the radar device  23  (appropriately referred to as a third radar device  23 ) is disposed near the front end portion of the right side surface of the lower deck  2   a . The detection range of the third radar device  23  is a range that spreads out to the right side from the oblique front right side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 6 , the radar device  24  (appropriately referred to as a fourth radar device  24 ) is disposed near the right end portion of the side portion of the vehicle body portion  2  at an intermediate height position between the lower deck  2   a  and the upper deck  2   b . The detection range of the fourth radar device  24  is a range that spreads out to the rear side from the right side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 6 , the radar device  25  (appropriately referred to as a fifth radar device  25 ) is disposed below the vessel  4  above an axle that transmits a drive force to the left and right rear wheels  6  of the dump truck  1 . The detection range of the fifth radar device  25  is a range that spreads out to the rear side from the oblique rear right side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 6 , the radar device  26  (appropriately referred to as a sixth radar device  26 ) is disposed above the axle like the fifth radar device  25  and on the right side of the fifth radar device  25  so as to be adjacent to the fifth radar device  25 . The detection range of the sixth radar device  26  is a range that spreads out to the rear side from the oblique rear left side of the vehicle body portion  2  of the dump truck  1  so as to cross the detection range of the fifth radar device  25 . 
     As illustrated in  FIG. 6 , the radar device  27  (appropriately referred to as a seventh radar device  27 ) is disposed near the left end portion of the side surface of the vehicle body portion  2  at an intermediate height position between the lower deck  2   a  and the upper deck  2   b , that is, at a position that is symmetrical to the fourth radar device  24  with respect to the center axis of the vehicle body portion  2  in the width direction. The detection range of the seventh radar device  27  is a range that spreads out to the rear side from the left side of the vehicle body portion  2  of the dump truck  1 . 
     As illustrated in  FIG. 6 , the radar device  28  (appropriately referred to as a first radar device  28 ) is disposed near the front end portion of the left side surface of the lower deck  2   a , that is, at a position that is symmetrical to the third radar device  23  with respect to the center axis of the vehicle body portion  2  in the width direction. The detection range of the eighth radar device  28  is a range that spreads out to the oblique front left side from the left side of the vehicle body portion  2  of the dump truck  1 . 
     The eight radar devices  21  to  28  can detect the relative positions between objects and the dump truck  1  over the entire peripheral area, which corresponds to 360°, of the dump truck  1  as the detection ranges. The eight radar devices  21  to  28  send relative position information, which represents the respective detected relative positions between the objects and the dump truck  1 , to the controller  100 . As described above, the plurality of (eight) radar devices  21  to  28  are provided on the vehicle body portion  2  and can detect objects that are present in the entire peripheral area of the vehicle body portion  2 . 
     &lt;Controller&gt; 
     The controller  100  displays whether or not an object is present around the dump truck  1  on the bird&#39;s-eye image  200  with the imaging devices  11  to  16  and the radar devices  21  to  28 , and informs an operator of the presence of the object as necessary. As illustrated in  FIG. 3 , the controller  100  includes a bird&#39;s-eye image synthesis unit  110 , a camera image switching/visual point changing unit  120 , a display controlling unit  130 , a monitor image creating unit  140 , an object information collecting unit  210 , and an object processing unit  220 . 
     As illustrated in  FIG. 3 , the bird&#39;s-eye image synthesis unit  110  is connected to the imaging devices  11  to  16 . The bird&#39;s-eye image synthesis unit  110  receives a plurality of image information (first to fifth image information) that is created when the respective imaging devices  11  to  16  take images. Further, the bird&#39;s-eye image synthesis unit  110  creates the bird&#39;s-eye image  200 , which includes the entire peripheral area of the dump truck  1 , by synthesizing images that correspond to the plurality of received image information. Specifically, the bird&#39;s-eye image synthesis unit  110  creates bird&#39;s-eye image information, which represents the bird&#39;s-eye image  200  formed by projecting a plurality of images onto a predetermined projection plane, by the coordinate conversion of the plurality of image information. 
     The camera image switching/visual point changing unit  120  is connected to the imaging devices  11  to  16  as illustrated in  FIG. 3 , and switches images that are taken by the respective imaging devices  11  to  16  and displayed on the screen of the monitor  50  together with the bird&#39;s-eye image  200  according to obstacle detection results and the like that are obtained from the radar devices  21  to  28 . Further, the camera image switching/visual point changing unit  120  converts the image information, which is acquired by the respective imaging devices  11  to  16 , into image information that is obtained from a visual point corresponding to the upper infinity. 
     As illustrated in  FIG. 3 , the display controlling unit  130  is connected to the camera image switching/visual point changing unit  120 , the monitor image creating unit  140 , and the object processing unit  220 . The display controlling unit  130  sends object position information, which is used to synthesize and display the position information of objects acquired by the radar devices  21  to  28  on the bird&#39;s-eye image  200  formed by synthesizing the image information acquired by the respective imaging devices  11  to  16 , to the camera image switching/visual point changing unit  120  and the monitor image creating unit  140 . 
     As illustrated in  FIG. 3 , the monitor image creating unit  140  is connected to the bird&#39;s-eye image synthesis unit  110 , the camera image switching/visual point changing unit  120 , and the display controlling unit  130 . The monitor image creating unit  140  creates an image, which includes the position of an object, on the bird&#39;s-eye image  200  on the basis of the image information, which is acquired by the imaging devices  11  to  16  and the radar devices  21  to  28  and corresponds to the entire peripheral area of the dump truck  1 , and the object position information. This image is displayed on the monitor  50 . 
     As illustrated in  FIG. 3 , the object information collecting unit  210  is connected to the radar devices  21  to  28  and the object processing unit  220 . The object information collecting unit  210  receives object detection results, which correspond to the respective detection ranges, from the radar devices  21  to  28  and sends the object detection results to the object processing unit  220 . 
     As illustrated in  FIG. 3 , the object processing unit  220  is connected to the object information collecting unit  210  and the display controlling unit  130 . The object processing unit  220  sends object position information, which is received from the object information collecting unit  210 , to the display controlling unit  130 . 
     In this embodiment, as illustrated in  FIG. 4 , the imaging devices  11  to  16  are disposed on the front surface and side surfaces of the upper deck  2   b  and below the vessel  4 . Further, the controller  100  creates the bird&#39;s-eye image  200 , which is illustrated in  FIG. 5 , by synthesizing the first to sixth image information, which are acquired when the imaging devices  11  to  16  take images, and displays the bird&#39;s-eye image  200  on the monitor  50  that is disposed in front of the driver&#39;s seat  31  in the cab  3 . At this time, the monitor  50  displays an image such as the bird&#39;s-eye image  200  according to the control of the controller  100 . The first to sixth image information, which correspond to the first to sixth areas  11 C to  16 C imaged by the imaging devices  11  to  16 , are synthesized by the controller  100 , so that the bird&#39;s-eye image  200  is obtained. The periphery monitoring system  10  displays this bird&#39;s-eye image  200  on the monitor  50 . For this reason, an operator of the dump truck  1  can monitor the entire range, which corresponds to 360° around the dump truck  1 , by visually recognizing the bird&#39;s-eye image  200  displayed on the monitor  50 . Next, the bird&#39;s-eye image will be described. 
     &lt;Bird&#39;s-Eye Image&gt; 
       FIG. 7  is a view illustrating an image converting method using a virtual projection plane VP. The controller  100  forms the bird&#39;s-eye image  200  of the peripheral area of the dump truck  1  on the basis of a plurality of images that are represented by a plurality of first to six image information. Specifically, the controller  100  performs the coordinate conversion of the first to six image information by using predetermined conversion information. The conversion information is information that represents the correspondence between the position coordinates of each of pixels of input images and the position coordinates of each of pixels of an output image. In this embodiment, the input images are images that are taken by the imaging devices  11  to  16  and are images corresponding to the first to six image information. The output image is the bird&#39;s-eye image  200  that is displayed on the monitor  50 . 
     The controller  100  converts the images, which are taken by the imaging devices  11  to  16 , into an image, which is seen from a predetermined virtual visual point positioned above the dump truck  1 , by using the conversion information. Specifically, as illustrated in  FIG. 7 , the images taken by the imaging devices  11  to  16  are converted into an image, which is seen from a virtual visual point VIP positioned above the dump truck  1 , by being projected onto a predetermined virtual projection plane VP. The conversion information represents the virtual projection plane VP. The converted image is a bird&#39;s-eye image displayed on the monitor  50 . The controller  100  forms the bird&#39;s-eye image  200  of the peripheral areas of the dump truck  1  by projecting the plurality of first to six image information, which are acquired from the plurality of imaging devices  11  to  16 , onto the predetermined virtual projection plane VP in order to synthesize the image information. 
     As illustrated in  FIG. 5 , the peripheral areas of the dump truck  1 , which are imaged by the respective imaging devices  11  to  16 , overlap each other at first to six overlapping areas OA 1  to OA 6 . The controller  100  displays images, which correspond to two information of the first to six image information obtained from two adjacent imaging devices of the imaging devices  11  to  16 , on the bird&#39;s-eye image  200  so that the images overlap each other at the respective first to six overlapping areas OA 1  to OA 6 . 
     Specifically, the controller  100  displays an image of the first image information obtained from the first imaging device  11  and an image of the second image information obtained from the second imaging device  12  so that the images overlap each other at the first overlapping area OA 1 . Further, the controller  100  displays the image of the first image information obtained from the first imaging device  11  and an image of the third image information obtained from the third imaging device  13  so that the images overlap each other at the second overlapping area OA 2 . Furthermore, the controller  100  displays the image of the second image information obtained from the second imaging device  12  and an image of the fourth image information obtained from the fourth imaging device  14  so that the images overlap each other at the third overlapping area OA 3 . Moreover, the controller  100  displays the image of the third image information obtained from the third imaging device  13  and an image of the fifth image information obtained from the fifth imaging device  15  so that the images overlap each other at the fourth overlapping area OA 4 . Further, the controller  100  displays the image of the fourth image information obtained from the fourth imaging device  14  and an image of the sixth image information obtained from the sixth imaging device  16  so that the images overlap each other at the fifth overlapping area OA 5 . Furthermore, the controller  100  displays the image of the fifth image information obtained from the fifth imaging device  15  and the image of the sixth image information obtained from the sixth imaging device  16  so that the images overlap each other at the sixth overlapping area OA 6 . 
     When two image information overlap each other and are synthesized at the first to six overlapping areas OA 1  to OA 6  in this way, values, which are obtained by multiplying the values of the first to six image information by synthesis ratios, are added. The synthesis ratios are values corresponding to the first to six image information, and are stored by the controller  100 . For example, the synthesis ratio of the first image information is 0.5, the synthesis ratio of the second image information is 0.5, and the like, that is, a synthesis ratio is determined for each of the first to six image information. Since the synthesis ratios are used, a plurality of image information are averaged and displayed at the first to six overlapping areas OA 1  to OA 6 . As a result, the rapid changes of a color and contrast are suppressed, so that the controller  100  can form a natural bird&#39;s-eye image  200 . The controller  100  creates synthesis image information, which represents the bird&#39;s-eye image synthesized as described above, and outputs the synthesis image information to the monitor  50 . 
       FIG. 8  is a plan view illustrating a relation between the dump truck and a vehicle that is present around the dump truck.  FIG. 9  is a front view illustrating the relation between the dump truck and the vehicle that is present around the dump truck. The dump truck  1 , which is used in a mine, is a very large vehicle of which the amount of objects is about 80 t (ton) to 400 t (ton), the overall length L is about 8 m (meter) to 15 m (meter), the width W is about 5 m (meter) to 10 m (meter), and the overall height Ha is about 5 m (meter) to 8 m. For this reason, an area where a shadow is formed is formed around the dump truck  1  according to the direction of the sun (an area denoted by SA of  FIGS. 3 and 4  is appropriately referred to as a shadow area SA in the following description). The shadow area SA depends on the altitude of the sun. However, since the overall height Ha of the dump truck  1  is particularly large, the size of the shadow area SA may exceed 10 m (meter) to the outside of the dump truck  1  in some cases. 
     A vehicle (service car)  300 , such as a car in which an operator of the dump truck  1  gets and which is used by the operator when the operator moves to the dump truck  1  or a car or a small truck that makes the rounds in a mine, is used in the mine. Since the vehicle  300  is a car or a small truck, the vehicle  300  has an overall length Lc of about 5 m (meter), a width We of about 2 m (meter), and an overall height Hc of about 2 m (meter). As described above, the vehicle  300  is significantly smaller than the dump truck  1 . The size of the shadow area SA substantially exceeds 10 m (meter) to the outside of the dump truck  1  as described above. Accordingly, when the vehicle  300  enters the shadow area SA, the vehicle  300  is completely hidden in the shadow area SA. 
     In general, there is the intensity of illumination substantially corresponding to diffused reflection or the like even in the area of a shadow. However, since the shadow area SA of the dump truck  1  is very large, light caused by diffused reflection or the like becomes very little. As a result, the intensity of illumination in the shadow area SA is reduced. For this reason, the bird&#39;s-eye image  200 , which is obtained by imaging the vehicle  300  present in the shadow area SA with the imaging devices  11  to  16 , has a large difference in the contrast of light and shade (black and white) (for example, tens of thousands lux or more). As a result, since the vehicle  300  present in the shadow area SA is surrounded by the dark (black) portion of the bird&#39;s-eye image  200 , so that there is a possibility that the vehicle  300  is not displayed on the bird&#39;s-eye image  200 . As a result, there is a possibility that the operator of the dump truck  1  may not recognize the vehicle  300  that is approaching the dump truck  1 . Particularly, when the vehicle  300  is present on the side opposite to the cab  3 , which is disposed on the upper deck  2   b , with respect to the center axis of the dump truck  1  in the width direction or on the rear side of the dump truck  1  as illustrated in  FIG. 3 , the vehicle  300  is present at the blind spot of the operator who gets in the cab  3 . Accordingly, it is necessary to allow the operator to reliably and visually recognize the vehicle  300 , which is present at the blind spot of the operator, by the bird&#39;s-eye image  200 . 
     A possibility that the vehicle  300  is present at a place in a mine where the dump truck  1  is present is high. Further, since the dump truck  1  itself moves in a mine while forming the shadow area SA, the place of the shadow area SA also changes from hour to hour. Furthermore, since the overall height of the dump truck  1  is changed when the vessel  4  is moved up and down, the range of the shadow area SA also significantly changes. For this reason, a situation around the dump truck  1  needs to be capable of being reliably taken in a situation by the bird&#39;s-eye image  200  in the dump truck  1 , which is used in a mine, even in the environment where a difference in the contrast of light and shade is large. 
     Moreover, since a difference in the intensity of illumination between a sunny spot and a shady spot is very large at a place where sunlight is very strong, such as immediately below the equator or near the equator, a difference in the contrast of light and shade (black and white) of the bird&#39;s-eye image  200  significantly appears at such a place. Accordingly, the vehicle  300  present in the shadow area SA becomes more difficult to see. Since relatively many mines are present immediately below the equator or near the equator, there is a large request for visually recognizing the vehicle  300 , which is present around the dump truck  1 , by the bird&#39;s-eye image  200  in the periphery monitoring system  10  that is used for the dump truck  1  used in a mine. 
     In order to be capable of visually recognizing the vehicle  300 , which is present around the dump truck  1 , by the bird&#39;s-eye image  200 , wide dynamic range (WDR) cameras are used as the imaging devices  11  to  16  in this embodiment. A wide dynamic range camera is a camera that has a function capable of adjusting the entire portion so that the entire portion can be visually recognized thoroughly, by correcting a dark portion into a bright portion while maintaining a bright portion at a visually recognizable level. 
     The first imaging device  11  illustrated in  FIG. 2  is a camera that can image the front side of the vehicle body portion  2 , and corresponds to a front wide dynamic range camera. The second imaging device  12  is a camera that can image the side (right side) and oblique front side of the vehicle body portion  2 , and corresponds to a first side wide dynamic range camera (first right wide dynamic range camera). The second imaging device  12  is a camera that can image the side (left side) and oblique front side of the vehicle body portion  2 , and corresponds to a first side wide dynamic range camera (first left wide dynamic range camera). The fourth imaging device  14  is a camera that can image the side (right side) and oblique rear side of the vehicle body portion  2 , and corresponds to a second side wide dynamic range camera (second right wide dynamic range camera). The fifth imaging device  15  is a camera that can image the side (left side) and oblique rear side of the vehicle body portion  2 , and corresponds to a second side wide dynamic range camera (second left wide dynamic range camera). The sixth imaging device  16  is a camera that can image the public relations of the vehicle body portion  2 , and corresponds to a rear wide dynamic range camera. 
       FIG. 10  is a view illustrating an example of an imaging device to which a wide dynamic range camera is applied. Each of the imaging devices  11  to  16  includes an imaging element  60  such as a CCD, a DSP (Digital Signal Processor)  61 , a decoder (video decoder)  62 , a brightness dynamic range correcting unit  63 , and an encoder (video encoder)  64 . The brightness dynamic range correcting unit  63  and the encoder  64  are realized by, for example, an image processing IC (Integrated Circuit)  64 . 
     The information on the image, which is taken by the imaging element  60 , is converted into a digital signal by an AD (Analog Digital) converter and the digital signal is then input to the DSP  61 . The DSP  61  processes the input digital signal of the information on the image, and then outputs the processed digital signal to the decoder  62 . The decoder  62  decodes the processed signal, which is input from the DSP  61 , and then outputs the decoded signal to the brightness dynamic range correcting unit  63 . The brightness dynamic range correcting unit  63  performs brightness correction, more specifically, high dynamic range synthesis processing of the input signal of the image. The high dynamic range synthesis processing is processing for converting an original image having very high contrast, that is, an actual image, which is taken by the imaging element  60 , into an image of which the contrast is reduced so as to be a contrast of about 1000:1. The brightness dynamic range correcting unit  63  outputs the signal of the image, which has been subjected to the high dynamic range synthesis processing, to the encoder  64 . The encoder  64  encodes the input signal, and outputs the encoded signal to the controller  100 . Signals that are output from the imaging devices  11  to  16 , that is, signals that are output from the encoders  64  are the first to six image information. 
     The imaging devices  11  to  16  can correct a dark portion, such as a portion becoming the shadow of the dump truck  1 , into a bright portion while maintaining a bright portion at a visually recognizable level by using wide dynamic range cameras as the imaging devices  11  to  16 . For this reason, the images, which are taken by the imaging devices  11  to  16 , do not easily cause under-exposure and over-exposure, and become images that are more easily understood as a whole. Accordingly, the periphery monitoring system  10 , which includes the imaging devices  11  to  16 , can display the bird&#39;s-eye image  200 , from which an object such as a vehicle  300  present in the shadow area SA of the dump truck  1  is easily and visually recognized, on the monitor  50 . When the periphery monitoring system  10  monitors the periphery of the dump truck  1  by using the images taken by the imaging devices  11  to  16  as described above, the periphery monitoring system  10  can display an object, which is present around the dump truck  1 , on the image (for example, the bird&#39;s-eye image  200  in this embodiment) even in the environment where a difference in the contrast of light and shade is large. As a result, the operator of the dump truck  1  can reliably and visually recognize the periphery of the dump truck  1 , particularly, an object such as a vehicle  300 , which is present in the shadow area SA, regardless of the environment. 
     Since the periphery monitoring system  10  can create the bird&#39;s-eye image  200 , which reliably displays an object present around the dump truck  1 , as described above even in the environment where a difference in the contrast of light and shade is large, the periphery monitoring system  10  can allow the operator to reliably and visually recognize the vehicle  300 , which is present at the blind spot of the operator, by the bird&#39;s-eye image  200 . Accordingly, the periphery monitoring system  10  is very effective when monitoring the periphery of the above-mentioned very large dump truck  1  that is used in a mine. That is, in the large dump truck  1  which may form a very large shadow area SA and moves while forming the shadow area SA by oneself and of which the shadow area SA is significantly changed when the vessel  4  is moved up and down and the area forming the blind spot is large, the periphery monitoring system  10  creates the bird&#39;s-eye image  200 , which reliably displays an object present around the dump truck  1 , and can provide accurate information on the periphery of the dump truck  1  to the operator of the dump truck  1 . Further, as for the dump truck  1  that operates at a place where a difference in the intensity of illumination between a sunny spot and a shady spot is very large, such as immediately below the equator, the periphery monitoring system  10  can provide accurate information on the periphery of the dump truck  1  to the operator of the dump truck  1 . 
     Meanwhile, the sixth imaging device  16  is disposed below the vessel  4  above an axle housing that connects two rear wheels  6  and  6 . As described above, the sixth imaging device  16  is disposed in the vehicle body portion  2  of the dump truck  1 . Furthermore, since the vessel  4  overhangs toward the rear side of the dump truck  1 , a shadow is apt to be formed below the vessel  4 . That is, the sixth imaging device  16  is disposed at a position where the shadow area SA is apt to be formed. For this reason, the sixth imaging device  16  has very many opportunities for imaging the shadow area SA. Accordingly, it is preferable that the dump truck  1  include at least the sixth imaging device  16  and use a wide dynamic range camera as the sixth imaging device. 
     &lt;Imaging Ranges of the Respective Imaging Devices&gt; 
     As illustrated in  FIG. 2 , the dump truck  1  includes the first imaging device  11 , the second imaging device  12 , the third imaging device  13 , the fourth imaging device  14 , and the fifth imaging device  15  that are disposed on the upper deck  2   b , and the sixth imaging device  16  that is disposed below the vessel  4  at the rear end of the frame  2   f . Particularly, the second and third imaging devices  12  and  13  cover areas between the left and right sides and the oblique front left and right sides of the vehicle body portion  2  of the dump truck  1  as imageable areas. Moreover, the fourth and fifth imaging devices  14  and  15  cover areas between the oblique rear left and right sides and the left and right sides of the vehicle body portion  2  of the dump truck  1  as imageable areas. According to this, the controller  100  can create the bird&#39;s-eye image  200 , which covers the entire peripheral area of the dump truck  1 , in conjunction with the first image information and the sixth image information, which are imaged and acquired by the first and sixth imaging devices  11  and  16 , and monitor the periphery of the dump truck  1 . 
     Further, in this embodiment, the imaging devices  11  to  16 , which are adjacent to each other, are disposed so that the first to sixth areas  11 C to  16 C, which are areas that can be imaged by the respective imaging devices  11  to  16 , overlap each other at the portions adjacent to each other as illustrated in  FIG. 5 . If the controller  100  is provided with connecting cables at the overlapping portions of the first to sixth areas  11 C to  16 C, which can be imaged by the respective imaging devices  11  to  16 , the controller  100  can monitor the entire peripheral area, which corresponds to 360°, of the dump truck  1  in plan view. Meanwhile, the connecting cables for connecting the first to sixth areas  11 C to  16 C, which are adjacent to each other, of the bird&#39;s-eye image  200  can be set at arbitrary positions in the overlapping ranges of the first to sixth areas  11 C to  16 C. Next, imaging ranges of the imaging devices  11  to  16  in the height direction will be described. 
       FIGS. 11 to 13  are views illustrating imaging ranges of the imaging devices of the periphery monitoring system according to this embodiment in the height direction.  FIGS. 14 to 16  are views illustrating cases where a vehicle moves around the dump truck. Three-dimensional imaging ranges of the respective imaging devices  11  to  16  on the entire peripheral area of the dump truck  1  are illustrated in  FIG. 13 . The imaging ranges of the respective imaging devices  11  to  16  in the height direction within a range of a predetermined distance around the dump truck  1  are illustrated in this embodiment. 
     In order to reliably display an object (for example, a vehicle), which is present around the dump truck  1  (for example, within a range of 10 m (meter) around the dump truck  1 ), on the bird&#39;s-eye image  200 , for example, the imaging device  11  may be disposed so that a part of the vehicle  300  is included in an imaging range  320  of the imaging device  11  as illustrated in  FIG. 11 . The other imaging devices  12  to  16  are the same as described above. When a vehicle  300  is present near the periphery of the imaging range on the front side of the dump truck  1  in the embodiment illustrated in  FIG. 11 , a roof  301  of the vehicle  300  gets out of the imaging range  320  of the first imaging device  11  in the state illustrated in  FIG. 11 . For this reason, the first imaging device  11  images the lower side from a window  302  of the vehicle  300 , so that the bird&#39;s-eye image  200  formed on the basis of this imaged image information displays the lower side of the window  302  of the vehicle  300 . As a result, there is a possibility that the operator of the dump truck  1 , which sees this bird&#39;s-eye image  200 , may not recognize the vehicle  300  since only a part of the vehicle  300  in the height direction is displayed. 
     Accordingly, in this embodiment, the respective imaging devices  11  to  16  are disposed so that the dump truck  1  allows the entire object (for example, a vehicle  300 ) present around the dump truck  1  to be displayed on the bird&#39;s-eye image  200  and allows an imaging range of the half or more (for example, 1.5 m (meter)) of the height of the upper deck  2   b  (for example, 3 m (meter)) in the height direction to be ensured. That is, in the case of an extra large vehicle such as the dump truck  1  that is used in a mine, it is difficult to visually recognize an object such as a vehicle  300  that is present below the upper deck  2   b  on which the cab  3  is installed when seen from the operator getting in the cab  3 . For this reason, in order to allow the periphery monitoring system  10  to check an object that is present around the dump truck  1 , it is necessary to allow an object, which is present at a position lower than the upper deck  2   b  from the ground, to be reliably recognized over the entire peripheral area of the dump truck  1 . 
     In this embodiment, the imaging devices are disposed so that the height Hs of at least one imaging range of all the imaging ranges of the respective adjacent imaging devices in the horizontal direction is equal to or larger than a size that includes the entire object (for example, a vehicle  300 ) at the boundary portions (or overlapping portions) of the bird&#39;s-eye image  200 , which is obtained by synthesizing image information imaged and acquired by adjacent imaging devices among the imaging devices  11  to  16 . Further, in this embodiment, at least one of two adjacent imaging devices is disposed so that the imaging range in the height direction becomes a height corresponding to the half or more of the height of the upper deck  2   b . As a result, since an object, which is present at a position lower than the upper deck  2   b , can be in the imaging range of one of the imaging devices, which are adjacent to each other, among the respective imaging devices  11  to  16  as illustrated in  FIG. 12 , it is possible to reliably display the entire object on the bird&#39;s-eye image  200 . 
     Specifically, even when, for example, the vehicle  300  serving as an object moves around the dump truck  1  to the first area  11 C from the third area  13 C so as to cross the boundary portion of the imaging range of each of the imaging devices  11  to  16  as illustrated in  FIGS. 14 to 16 , the periphery monitoring system  10  can display the entire vehicle  300  on the bird&#39;s-eye image  200 . Meanwhile, it is preferable that an alpha blending technique, which averages and displays the overlapping portions of the boundary portions of the image corresponding to the first to six image information, be used when the bird&#39;s-eye image  200  is created by the synthesis of the first to six image information acquired by the respective imaging devices  11  to  16 . According to this, it is possible to avoid the disappearance of an object at the boundary portions of the bird&#39;s-eye image  200  even when the object moves so as to cross the boundary portions of the images corresponding to the first to six image information. 
     &lt;Modification&gt; 
     In the above-mentioned embodiment, the periphery monitoring system  10  has created the bird&#39;s-eye image  200  on the basis of image information that is imaged and acquired by the imaging devices  11  to  16 . However, the periphery monitoring system  10  is not limited to this embodiment. As described above, the dump truck  1  has the poorest visibility on the rear side and the range of the shadow area SA is significantly changed when the vessel  4  is moved up and down. The periphery monitoring system  10  may use, for example, only the sixth imaging device  16  that is disposed below the vessel  4  of the dump truck  1 , and may use a high dynamic range camera as the sixth imaging device  16  in order to monitor the rear side of the dump truck  1 . That is, the sixth imaging device  16 , which is formed of a high dynamic range camera, may be used as a back monitor of the dump truck  1 . According to this, the periphery monitoring system  10  can create an image on which vehicles or other objects present on the rear side of the dump truck  1  are displayed even in the environment where a difference in the contrast of light and shade is large, and can display the image on the monitor  50 . 
     Meanwhile, it is preferable that six imaging devices  11  to  16  be used and wide dynamic range cameras be used as all these imaging devices when the entire peripheral area of the peripheral area of the dump truck  1  is monitored. According to this, it is possible to obtain the bird&#39;s-eye image  2  on which vehicles or other objects present around the dump truck  1  over the entire peripheral area of the dump truck  1  are displayed even in the environment where a difference in the contrast of light and shade is large. 
     This embodiment and the modification thereof have been described above, but elements that can be easily supposed by those skilled in the art and substantially the same elements are included in the above-mentioned components. In addition, the above-mentioned components may be appropriately combined with each other. Further, the components may be variously omitted, substituted, or modified without departing from the scope of this embodiment. The dump trucks according to this embodiment and the modification of this embodiment may have a large difference in the contrast of light and shade between a shady portion and a sunny spot portion due to the shadows that are formed by the dump trucks. For this reason, a dump truck used in a mine will be described above as an example in the above-mentioned embodiment and the modification of the embodiment. However, the dump truck is not limited to a dump truck used in a mine, and may be a dump truck that can be used in a construction site such as a dam. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  DUMP TRUCK 
               2  VEHICLE BODY PORTION 
               2   a  LOWER DECK 
               2   b  UPPER DECK 
               2   f  FRAME 
               3  CAB 
               3   a  PILLAR 
               4  VESSEL 
               4 F FLANGE PORTION 
               5  FRONT WHEEL 
               6  REAR WHEEL 
               10  PERIPHERY MONITORING SYSTEM 
               11 ,  12 ,  13 ,  14 ,  15 ,  16  IMAGING DEVICES 
               21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28  RADAR DEVICES 
               31  DRIVER&#39;S SEAT 
               50  MONITOR 
               60  IMAGING ELEMENT 
               61  DSP 
               62  DECODER 
               63  BRIGHTNESS DYNAMIC RANGE CORRECTING UNIT 
               64  ENCODER 
               100  CONTROLLER 
               110  BIRD&#39;S-EYE IMAGE SYNTHESIS UNIT 
               120  CAMERA IMAGE SWITCHING/VISUAL POINT CHANGING UNIT 
               130  DISPLAY CONTROLLING UNIT 
               140  MONITOR IMAGE CREATING UNIT 
               200  BIRD&#39;S-EYE IMAGE 
               210  OBJECT INFORMATION COLLECTING UNIT 
               220  OBJECT PROCESSING UNIT 
               300  VEHICLE 
             SA SHADOW AREA