Patent Publication Number: US-11390218-B2

Title: Vehicle periphery monitoring device, vehicle periphery monitoring method and non-transitory storage medium

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2020-110607 filed on Jun. 26, 2020, the disclosure of which is incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a vehicle periphery monitoring device, a vehicle periphery monitoring method, and a non-transitory storage medium. 
     Related Art 
     A video processing system that detects dirt or scratches or the like on a lens by comparing characteristic quantities of images in the same image acquisition range that have been acquired by a plurality of cameras is disclosed, for example, in Japanese Patent Application Publication Laid-Open (JP-A) No. 2019-102929. More specifically, this video processing system divides an image acquisition range of respective images acquired by a plurality of cameras into areas, and calculates the quantity of cumulative edges in each area. If the difference in the respective quantities of cumulative edges is greater than a predetermined threshold value, then it is determined that a foreign object is adhering to a lens. 
     However, in the video processing system disclosed in JP-A No. 2019-102929, because it is not possible to detect any misalignment of the camera mounting positions, if a composite image is displayed on a display unit inside a vehicle cabin, there is a possibility that incorrect composite images containing positionally misaligned images will be displayed. 
     SUMMARY 
     The present disclosure provides a vehicle periphery monitoring device that, in a structure that displays composite images, inhibits composite images that are incorrect because of camera misalignment from being displayed. 
     A vehicle periphery monitoring device of a first aspect has a rear image acquisition unit that acquires rear images including a first image of a vehicle rear side acquired by a rear camera, a second image of a vehicle rear right-side acquired by a rear right-side camera, and a third image of a vehicle rear left-side acquired by a rear left-side camera, a target position acquisition unit that acquires from a plurality of sensors including the rear camera, the rear right-side camera and the rear left-side camera relative positions of a target present in areas including the vehicle rear side, the vehicle rear right-side, and the vehicle rear left-side relative to its own host vehicle, a target position determination unit that determines whether or not the relative positions of the target acquired by the target position acquisition unit are mutually consistent with each other in the plurality of sensors, and a display processing unit that, in a case in which it is determined by the target position determination unit that the relative positions of the target are mutually consistent with each other, displays a single composite image that is created by combining the first image, the second image, and the third image at a display unit provided in a vehicle cabin, and that, in a case in which it is determined by the target position determination unit that the relative positions of the target are not mutually consistent with each other, displays the first image, the second image, and the third image individually and adjacently to each other on the display unit. 
     In the vehicle periphery monitoring device according to the first aspect, a rear image acquisition unit acquires a rear image that includes a first image of a vehicle rear side, a second image of a vehicle rear right-side, and a third image of a vehicle rear left-side. Here, the first image is an image acquired by a rear camera. Moreover, the second image is an image acquired by a rear right-side camera, and the third image is an image acquired by a rear left-side camera. 
     The target position acquisition unit acquires from a plurality of sensors including the rear camera, the rear right-side camera and the rear left-side camera relative positions, relative to its own host vehicle, of a target present in areas including the vehicle rear side, the vehicle rear right-side, and the vehicle rear left-side. In addition, a target position determination unit determines whether or not the relative positions of the target, relative to its own host vehicle, acquired by the target position acquisition unit are mutually consistent with each other in the plurality of sensors. Furthermore, a display processing unit displays the first image, the second image, and the third image on a display unit provided in a vehicle cabin. 
     Here, in a case in which it is determined by the target position determination unit that the relative positions of the target, relative to its own host vehicle, are mutually consistent in the plurality of sensors, the display processing unit displays at the display unit a single composite image that is created by combining the first image, the second image, and the third image. As a result, a vehicle occupant is able to easily recognize the position of a target traveling at the rear of their own vehicle. 
     On the other hand, in a case in which it is determined by the target position determination unit that the relative positions of the target, relative to its own host vehicle, are not mutually consistent in the plurality of sensors, the display processing unit displays the first image, the second image, and the third image individually and adjacently to each other on the display unit. In this way, in a case in which the mounting position of any one of the rear camera, the rear right-side camera, or the rear left-side camera becomes out of alignment, by displaying the individual images on the display unit, a composite image containing positionally misaligned images does not get displayed on the display unit. 
     Note that the term ‘composite image’ referred to here is an image that is created by performing image processing on each of the first image, the second image, and the third image such that the first image, the second image, and the third image are combined together into a single seamless image. 
     A vehicle periphery monitoring device of a second aspect is characterized in that, in the first aspect, the target position acquisition unit acquires the relative positions of the target from three or more sensors including the rear camera, the rear right-side camera and the rear left-side camera. 
     In the vehicle periphery monitoring device of the second aspect, by acquiring the relative positions of the target relative to a host vehicle from three or more sensors, the detection accuracy when detecting the relative positions of the target can be improved compared to a structure in which the relative positions of the target relative to a host vehicle are acquired from two or fewer sensors. 
     A vehicle periphery monitoring device of a third aspect is characterized in that, in the second aspect, there is further provided an enhanced display unit that provides an enhanced display of a target approaching the host vehicle in an image displayed on the display unit. 
     In the vehicle periphery monitoring device of the third aspect, by providing an enhanced display of a target approaching their vehicle, it is possible to draw the attention of a vehicle occupant to the target. 
     A vehicle periphery monitoring device of a fourth aspect is characterized in that, in the third aspect, in a case in which only the relative position of the target detected by just one sensor among the three or more sensors is not consistent in the target information determination unit, the enhanced display unit provides an enhanced display on the display unit based on a relative positions of the target acquired from the remaining sensors after the information from the one sensor has been excluded. 
     In the vehicle periphery monitoring device of the fourth aspect, by providing an enhanced display based on a relative positions of the target acquired from the remaining sensors, it is possible to provide an enhanced display at the correct position of the target. In other words, because there is a possibility that the mounting position of a sensor having a relative position of the target that is not consistent with those of the other sensors has become misaligned, it is possible to inhibit an enhanced display being provided at an incorrect position due to information from the misaligned sensor being included. 
     A vehicle periphery monitoring device of a fifth aspect is characterized in that, in the third aspect, in a case in which the relative positions of the target detected by all of the sensors among the three or more sensors are all c in the target position determination unit, the enhanced display unit provides an enhanced display based on the relative position of the target acquired from the sensor having a relative position of the target that is detected as being closest to the host vehicle. 
     In the vehicle periphery monitoring device of the fifth aspect, by providing an enhanced display based on the relative position of the target acquired from the sensor having a detected relative position of the target that is the closest to the host vehicle, information having a high degree of urgency can be conveyed to a vehicle occupant. 
     A vehicle periphery monitoring device of a sixth aspect is characterized in that, in the fourth aspect, in a case in which only the relative position of the target detected by any one sensor among the rear camera, the rear right-side camera and the rear left-side camera is not consistent with the other relative positions in the target position determination unit, warning content is displayed on the display unit superimposed on the rear image acquired by the one sensor. 
     In the vehicle periphery monitoring device of the sixth aspect, by displaying warning content superimposed on the rear image acquired by the sensor having a mounting position has a possibility of being misaligned, it is possible to alert a vehicle occupant as to this possibility. 
     A vehicle periphery monitoring device of a seventh aspect is characterized in that, in the fifth aspect, in a case in which the relative positions of the target detected by the rear camera, the rear right-side camera and the rear left-side camera are all mutually different from each other in the target position determination unit, warning content is displayed superimposed on all of the images of the first image, the second image, and the third image which correspond to those sensors that have detected the target. 
     In the vehicle periphery monitoring device of the seventh aspect, because warning content is displayed superimposed on a plurality of images, it is possible to encourage a vehicle occupant to make a vehicle inspection or the like. 
     A vehicle periphery monitoring device of an eighth aspect is characterized in that, in any one of the first through seventh aspects, the target position acquisition unit acquires the relative positions of the target from the sensors that include radar units that are provided in corner portions of a vehicle body rear portion and detect obstacles at the rear of the vehicle. 
     In the vehicle periphery monitoring device of the eighth aspect, by detecting a relative position of a target using obstacle detection radar, there is no need to install dedicated sensors so that an increase in the number of components is inhibited. 
     As has been described above, according to the vehicle periphery monitoring device according to the present disclosure, it is possible, in a structure that displays composite images, to inhibit composite images that are incorrect because of camera misalignment from being displayed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG. 1  is a block diagram showing a hardware structure of a vehicle periphery monitoring device according to an exemplary embodiment; 
         FIG. 2  is a view as seen from a vehicle rear side of a front portion of a vehicle cabin interior of a vehicle provided with the vehicle periphery monitoring device according to the exemplary embodiment; 
         FIG. 3  is a plan view showing a vehicle provided with the vehicle periphery monitoring device according to the exemplary embodiment, and a motorcycle traveling behind this vehicle; 
         FIG. 4  is a block diagram showing a function structure of the vehicle periphery monitoring device according to the exemplary embodiment; 
         FIG. 5  is a flowchart showing an example of a flow of display processing of the exemplary embodiment; 
         FIG. 6  is a view showing an example of an image being displayed on an electronic interior mirror of the exemplary embodiment, and shows a composite image being displayed; 
         FIG. 7  is a view showing an example of an image being displayed on an electronic interior mirror of the exemplary embodiment, and shows an example of a state in which a mounting position of a rear right-side camera has become misaligned; and 
         FIG. 8  is a view showing an example of an image being displayed on an electronic interior mirror of the exemplary embodiment, and shows an example of a state in which mounting positions of a rear camera and a rear right-side camera have become misaligned. 
     
    
    
     DETAILED DESCRIPTION 
     A vehicle periphery monitoring device  10  according to an exemplary embodiment will now be described with reference to the drawings. 
     (Hardware Structure of the Vehicle Periphery Monitoring Device  10 ) 
     As is shown in  FIG. 1 , the vehicle periphery monitoring device  10  of the present exemplary embodiment is configured so as to include a CPU (Central Processing Unit)  14 , ROM (Read Only Memory)  16 , RAM (Random Access memory)  18 , storage  20 , a communication interface  22 , and an input/output interface  24 . Each of these structures is connected via a bus  26  so as to be able to mutually communicate with the other structures. As an example, the vehicle periphery monitoring device  10  of the present exemplary embodiment forms part of an ECU (Electronic Control Unit) that is mounted in a vehicle  12 . 
     The CPU  14  which is serving as a processor is a central processing unit, and performs tasks such as executing various types of programs, and controlling various units. In other words, the CPU  14  reads programs from the ROM  16 , which is serving as memory, or from the storage  20 , which is also serving as memory, and executes these programs using the RAM  18  as a work area. The CPU  14  performs the aforementioned control of the various structures and various types of computation processing in accordance with the programs stored in the ROM  16  or the storage  20 . 
     The ROM  16  stores various types of programs and various types of data. The RAM  18  serves as a work area and temporarily stores programs or data. The storage  20  is formed by an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and is a non-transient storage medium that stores various types of programs including operating systems, and various types of data. In the present exemplary embodiment, a display program and the like that is used to display a composite image is stored in the ROM  16  or in the storage  20 . 
     The communication interface  22  is an interface that the vehicle periphery monitoring device  10  uses to perform communication via a computer network, and a Standard such as, for example, 5G LTE, Wi-Fi (Registered Trademark), or Ethernet (Registered Trademark) is used for this communication. 
     A rear camera  28 , a rear right-side camera  30 , a rear left-side camera  32 , a right-side radar  34 , a left-side radar  36 , an electronic interior mirror  38  which serves as a display unit, a right-side warning display unit  40 R and a left-side warning display unit  40 L are connected to the input/output interface  24 . The rear camera  28 , the rear right-side camera  30 , the rear left-side camera  32 , the left-side radar  34 , and the right-side radar  36  each correspond to a ‘sensor’ according to the present disclosure. 
     As is shown in  FIG. 2 , a right side-door  29 R is disposed at the right side of the vehicle  12 , and a right camera-support portion  31 R is provided on an outer surface of a front-end portion of the right side-door  29 R. The right camera-support portion  31 R protrudes towards the vehicle right side from the right side-door  29 R, and the rear right-side camera  30  is mounted facing towards the vehicle rear side on a right-side end portion of the right camera-support portion  31 R. 
     In contrast, a left side-door  29 L is disposed at the left side of the vehicle  12 , and a left camera-support portion  31 L is provided on an outer surface of a front-end portion of the left side-door  29 L. The left camera-support portion  31 L protrudes towards the vehicle left side from the left side-door  29 L, and the rear left-side camera  32  is mounted facing towards the vehicle rear side on a left-side end portion of the left camera-support portion  31 L. 
     As is shown in  FIG. 3 , the rear right-side camera  30  is mounted on the right side of the vehicle  12 , and the rear left-side camera  32  is mounted on the left side of the vehicle  12 . An example of an image acquisition range of the rear right-side camera  30  is an area indicated by solid lines AR 2  in  FIG. 3 . The image acquisition range AR 2  is an area bounded by a straight line extending from the rear right-side camera  30  along the right side of the vehicle  12  towards the vehicle rear, and a straight line extending from the rear right-side camera  30  diagonally rearwards and towards the right side. 
     In addition, an example of an image acquisition range of the rear left-side camera  32  is an area indicated by solid lines AR 3  in  FIG. 3 . The image acquisition range AR 3  is an area bounded by a straight line extending from the rear left-side camera  32  along the left side of the vehicle  12  towards the vehicle rear, and a straight line extending from the rear left-side camera  32  diagonally rearwards and towards the left side. 
     The rear camera  28  is mounted facing towards the vehicle rear side in a central portion in a vehicle width direction of a rear end portion of the vehicle  12 , and acquires images of the area behind the vehicle. An example of an image acquisition range of the rear camera  28  is an area indicated by single-dot chain lines AR 1  in  FIG. 3 . The image acquisition range AR 1  is an area that spreads out progressively wider towards the left and right sides the further away it is from the rear end portion of the vehicle  12 . 
     The right-side radar  34  is mounted on a right corner portion of a vehicle body rear portion of the vehicle  12 , and is a radar unit that detects obstacles to the rear of the vehicle. An example of a detection range of the right-side radar  34  is an area indicated by double-dot chain lines AR 4  in  FIG. 3 . The detection range AR 4  is a fan-shaped area centered on the right-side radar  34 , and is set as an area that spans the space between the image acquisition range AR 1  of the rear camera  28  and the image acquisition range AR 2  of the rear right-side camera  30 . 
     The left-side radar  36  is mounted on a left corner portion of the vehicle body rear portion of the vehicle  12 , and is a radar unit that detects obstacles to the rear of the vehicle. An example of a detection range of the left-side radar  36  is an area indicated by double-dot chain lines AR 5  in  FIG. 3 . The detection range AR 5  is a fan-shaped area centered on the left-side radar  36 , and is set as an area that spans the space between the image acquisition range AR 1  of the rear camera  28  and the image acquisition range AR 3  of the rear left-side camera  32 . 
     As is shown in  FIG. 2 , the electronic interior mirror  38  is formed by an LCD panel, and is able to display images to vehicle occupants. Moreover, as is shown in  FIG. 7 , a first image  70 A of the area to the vehicle rear that is acquired by the rear camera  28 , a second image  70 B that is acquired by the rear right-side camera  30 , and a third image  70 C that is acquired by the rear left-side camera  32  are displayed on the electronic interior mirror  38 . Furthermore, as is shown in  FIG. 6 , it is also possible for a composite image  70 D that is formed by combining together the first image  70 A, the second image  70 B, and the third image  70 C to be displayed on the electronic interior mirror  38 . In this way, the electronic interior mirror  38  functions as a replacement for an interior rear-view mirror so that, by viewing images displayed on the electronic interior mirror  38 , a vehicle occupant is able to ascertain the situation over a wide area at the rear of the vehicle  12 . 
     A right-side warning display unit  40 R is provided in the right camera-support portion  31 R. The right-side warning display unit  40 R is a display unit that is visible to a vehicle occupant and displays a warning when an approach of an obstacle from the rear right-side direction of the vehicle is detected by the right-side radar  34 . 
     A left-side warning display unit  40 L is provided in the left camera-support portion  31 L. The left-side warning display unit  40 L is a display unit that is visible to a vehicle occupant and displays a warning when an approach of an obstacle from the rear left-side direction of the vehicle is detected by the left-side radar  36 . 
     (Function Structure of the Vehicle Periphery Monitoring Device  10 ) 
     The vehicle periphery monitoring device  10  is able to perform various types of functions using the above-described hardware resources. The function structure achieved by the vehicle periphery monitoring device  10  will now be described with reference to  FIG. 4 . 
     As is shown in  FIG. 4 , the vehicle periphery monitoring device  10  is configured so as to include a rear image acquisition unit  50 , a target position acquisition unit  52 , a target position determination unit  54 , a display processing unit  56 , an enhanced display unit  58 , and a warning display unit  60  as function structures. Each function structure is achieved as a result of the CPU  14  reading a program stored in the ROM  16  or the storage  20  and then executing this program. 
     The rear image acquisition unit  50  acquires rear images including the first image  70 A of the area to the vehicle rear that is acquired by the rear camera  28 , the second image  70 B of the area to the rear right-side of the vehicle that is acquired by the rear right-side camera, and the third image  70 C of the area to the rear left-side of the vehicle that is acquired by the rear left-side camera. 
     The target position acquisition unit  52  acquires the relative positions relative to the vehicle  12  of a target that is present in areas including the area to the vehicle rear, the area to the rear right-side of the vehicle, and the area to the rear left-side of the vehicle from a plurality of sensors including the rear camera  28 , the rear right-side camera  30 , and the rear left-side camera  32 . As an example, in the present exemplary embodiment, the target position acquisition unit  52  acquires the relative positions of the target relative to the vehicle  12  by acquiring signals from the right-side radar  34  and the left-side radar  36  in addition to the rear camera  28 , the rear right-side camera  30 , and the rear left-side camera  32 . 
     In the present exemplary embodiment, if the vehicle  12  is looked at in a plan view, the coordinates of the target are acquired taking a center portion in the vehicle width direction of the rear end portion of the vehicle  12  as a reference position. For example, as is shown in  FIG. 3 , in a case in which a motorcycle  100  is approaching the vehicle  12  from a rear right-side direction, this motorcycle  100  travels through an area where the image acquisition range AR 1  of the rear camera  28  and the image acquisition range AR 2  of the rear right-side camera  30  mutually overlap. In addition, the motorcycle  100  also travels through the detection range AR 4  of the right-side radar  34 . At this time, the target position acquisition unit  52  calculates the relative position of the motorcycle  100  based on the first image  70 A that was acquired by the rear camera  28 , and then acquires the coordinates of the motorcycle  100  relative to the reference position by correcting the result of this calculation. In the same way, the target position acquisition unit  52  calculates the relative position of the motorcycle  100  based on the second image  70 B that was acquired by the rear right-side camera  30 , and then acquires the coordinates of the motorcycle  100  relative to the reference position by correcting the result of this calculation. Furthermore, the target position acquisition unit  52  also corrects the relative position of the motorcycle  100  that was detected by the right-side radar  34 , and then acquires the coordinates of the motorcycle  100  relative to the reference position. For this reason, if all of the sensors are mounted in their proper positions, then the coordinates of the motorcycle  100  that have been acquired at the same timings by the target position acquisition unit  52  are all the same coordinates. 
     As is shown in  FIG. 4 , the target position determination unit  54  determines whether or not the relative positions of the target acquired by the target position acquisition unit  52  are consistent in the plurality of sensors. More specifically, in the example shown in  FIG. 3 , the target position determination unit  54  determines whether or not the coordinates of the motorcycle  100  that have been acquired at the same timings by the target position acquisition unit  52  from the three sensors, namely, the rear camera  28 , the rear right-side camera  30 , and the right-side radar  34  are mutually consistent with each other. 
     As is shown in  FIG. 4 , in a case in which it is determined by the target position determination unit  54  that the relative positions of the target are mutually consistent with each other, then as is shown in  FIG. 6 , the display processing unit  56  combines the first image  70 A, the second image  70 B, and the third image  70 C into the single composite image  70 D and displays this at the electronic interior mirror  38 . The composite image  70 D is a composite image formed by performing image processing respectively on the first image  70 A, the second image  70 B, and the third image  70 C, and is displayed with their viewing angles appropriately changed so that the first image  70 A, the second image  70 B, and the third image  70 C are combined together into a single seamless image. To achieve this, in the composite image  70 D, the boundary between the first image  70 A and the second image  70 B, and the boundary between the first image  70 A and the third image  70 C are moved appropriately to the right or left. 
     In contrast, in a case in which it is determined by the target position determination unit  54  that the relative positions of the target are not mutually consistent with each other, then as is shown in  FIG. 7 , the display processing unit  56  displays the first image  70 A, the second image  70 B, and the third image  70 C as separate individual images adjacently to each other on the electronic interior mirror  38 . In a case in which the first image  70 A, the second image  70 B, and the third image  70 C are displayed adjacently to each other as individual images, a first partition area  72 A is provided between the first image  70 A and the second image  70 B, and a second partition area  72 B is provided between the first image  70 A and the third image  70 C. By providing the first partition area  72 A and the second partition area  72 B in this way, a vehicle occupant is made visually aware that the first image  70 A, the second image  70 B, and the third image  70 C have not been combined into a composite image. Note that, in the present exemplary embodiment, as an example, in a case in which the first image  70 A, the second image  70 B, and the third image  70 C are displayed adjacently to each other as individual images, the respective images each have a fixed display range. In other words, the positions of the first partition area  72 A and the second partition area  72 B are fixed, and the first image  70 A is displayed between the first partition area  72 A and the second partition area  72 B. In addition, the second image  70 B is displayed on the right side of the first partition area  72 A, and the third image  70 C is displayed on the left side of the second partition area  72 B. 
     As is shown in  FIG. 4 , the enhanced display unit  58  provides an enhanced display of the target approaching the vehicle  12  in the image displayed on the display processing unit  56 . In the present exemplary embodiment, as an example, as is shown in  FIG. 6 , in a case in which the motorcycle  100  is approaching the vehicle  12 , an enhanced display is provided by displaying a frame-shaped mark M superimposed on the position of the motorcycle  100  in the composite image  70 D. Because a following vehicle  102  is following at a sufficient distance from the vehicle  12 , an enhanced display of the following vehicle  102  is not provided. 
     Here, the enhanced display unit  58  of the present exemplary embodiment changes the method used to calculate the relative position of the target to be displayed as an enhanced image in accordance with preconditions. More specifically, in a case in which only the relative position of the target detected by just one sensor among the three or more sensors is determined in the target position determination unit  54  to not be consistent with the other relative positions, the enhanced display unit  58  provides an enhanced display based on a relative positions of the target acquired from the other sensors with the information from the inconsistent sensor being excluded. 
     For example, as is shown in  FIG. 3 , a case in which the relative positions of the motorcycle  100  are detected by the rear camera  28 , the rear right-side camera  30 , and the right-side radar  34  will now be considered. In this state, in a case in which the relative position of the motorcycle  100  as detected by the rear right-side camera  30  is not consistent with the relative positions detected by the other sensors (i.e., by the rear camera  28  and the right-side radar  34 ), the enhanced display unit  58  provides an enhanced display at a position that is calculated based on a relative positions detected by the rear camera  28  and the right-side radar  34 . In other words, a structure is employed in which, by excluding the information about the relative position of the motorcycle  100  detected by the rear right-side camera  30 , data having a high probability of being erroneous is excluded. 
     Moreover, in a case in which the relative positions of the target detected by all of the sensors among the three or more sensors are all mutually different from each other in the target position determination unit  54 , the enhanced display unit  58  of the present exemplary embodiment provides an enhanced display based on the relative position of the target acquired from the particular sensor having a detected relative position of the target that is the closest to the vehicle  12 . 
     For example, as is shown in  FIG. 3 , a case in which the relative positions of the motorcycle  100  are detected by the rear camera  28 , the rear right-side camera  30 , and the right-side radar  34  will be considered. In this state, in a case in which the relative positions detected by all of the sensors are mutually different from each other, and the relative position of the motorcycle  100  detected by the right-side radar  34  is the closest to the vehicle  12 , the enhanced display unit  58  provides an enhanced display based on the relative position of the motorcycle  100  acquired from the right-side radar  34 . 
     As is shown in  FIG. 4 , the warning display unit  60  displays warning content superimposed on the rear image at the electronic interior mirror  38 . More specifically, in a case in which only the relative position of the target detected by any one sensor among the rear camera  28 , the rear right-side camera  32 , and the right-side radar  34  is determined in the target position determination unit  54  to not be consistent with the other relative positions, the warning display unit  60  displays superimposed warning content. 
     For example, in a case in which only the relative position of the target detected by the rear right-side camera  30  is not consistent with the other relative positions, as is shown in  FIG. 7 , the warning display unit  60  displays the warning content  74  superimposed on the second image  70 B acquired by the rear right-side camera  30  on the electronic interior mirror  38 . Here, by displaying ‘camera misalignment’ as the warning content, the suggestion is made to a vehicle occupant that there is a possibility that the relative position of the target displayed in the second image  70 B has not been correctly detected. Moreover, in a case in which only the relative position of the target detected by the right-side radar  34  is not consistent with the other relative positions, it is also possible to provide a display indicating that there is a fault with the right-side radar on a center display or the like installed in the instrument panel instead of providing a warning display on the right-side warning display unit  40 R (see  FIG. 2 ). Note that the warning display unit  60  may be in the form of different warning content such as an icon or the like that are displayed superimposed on a display unit. 
     Moreover, in a case in which the relative positions of the target detected by the rear camera  28 , the rear right-side camera  30 , and the rear left-side camera  34  are all mutually different from each other in the target position determination unit  54 , the warning display unit  60  displays warning content superimposed on all of the images of the first image  70 A, the second image  70 B, and the third image  70 C that correspond to sensors detecting the target. 
     For example, in a case in which the relative positions of the motorcycle  100  are detected by the rear camera  28  and the rear right-side camera  30 , as is shown in  FIG. 8 , the warning display unit  60  displays the warning content  76  superimposed on the first image  70 A, which corresponds to the rear camera  28 , at the electronic interior mirror  38 . In the same way, the warning display unit  60  displays the warning content  74  superimposed on the second image  70 B, which corresponds to the rear right-side camera  30 , at the electronic interior mirror  38 . In the present exemplary embodiment, as an example, the contents of the warning contents  74  and the warning contents  76  are both the same, however, it is also possible for other warning content to be displayed. 
     (Actions) 
     Next, actions of the present exemplary embodiment will be described. 
     (Example of the Display Processing) 
       FIG. 5  is a flowchart showing an example of the flow of display processing performed by the vehicle periphery monitoring device  10 . This display processing is executed as a result of the CPU  14  reading a program from the ROM  16  or storage  20 , and then expanding and executing this program. Note that, as an example, in the flowchart described below, as is shown in  FIG. 3 , a state in which the motorcycle  100 , which is serving as the target, is detected by the rear camera  28 , the rear right-side camera  30 , and the right-side radar  34 . 
     As is shown in  FIG. 5 , in step S 102 , the CPU  14  displays a composite image on the electronic interior mirror  38 . More specifically, utilizing the functions of the display processing unit  56 , the CPU  14  displays the composite image  70 D, which is created by combining the first image  70 A acquired by the rear camera  28 , the second image  70 B which is created by the rear right-side camera  30 , and the third image which is acquired by the rear left-side camera  32 , on the electronic interior mirror  38  (see  FIG. 6 ). 
     In step S 104 , the CPU acquires the relative positions of the motorcycle  100 . More specifically, utilizing the functions of the target position acquisition unit  52 , the CPU  14  acquires the relative positions of the motorcycle  100  relative to the vehicle  12  by acquiring signals from the rear camera  28 , the rear right-side camera  30 , and the right-side radar  34 . 
     In step S 106 , the CPU  14  determines whether or not the relative positions from the three sensors are mutually consistent with each other. More specifically, utilizing the functions of the target position determination unit  54 , the CPU  14  determines whether or not the coordinates of the motorcycle  100  that have been acquired at the same timings from the three sensors, namely, the rear camera  28 , the rear right-side camera  30 , and the right-side radar  34  are mutually consistent with each other. 
     If the CPU  14  determines in step S 106  that the relative positions from the three sensors are mutually consistent with each other, the routine moves to the processing of step S 110 . If, on the other hand, the CPU  14  determines in step S 106  that the relative positions from the three sensors are not mutually consistent with each other, the routine moves to the processing of step S 108 . 
     In step S 110 , utilizing the functions of the enhanced display unit  58 , the CPU  14  provides an enhanced display at the relative position of the motorcycle  100 . For example, as is shown in  FIG. 7 , the CPU  14  may provide an enhanced display by displaying a superimposed frame-shaped mark M. The CPU  14  then ends the display processing. 
     In contrast, in step S 108 , the CPU  14  determines whether or not the relative position of only one sensor is not consistent with the other relative positions. More specifically, in a case in which, utilizing the functions of the target position determination unit  54 , the CPU  14  determines that the relative position from only one sensor among the coordinates for the motorcycle  100  acquired at the same timings from the three sensors is not consistent with the other relative positions, the routine moves to the processing of step S 112 . Moreover, in a case in which the CPU  14  determines in step S 108  that the number of sensors having a relative positions are inconsistent is not just one sensor, in other words, if the CPU  14  determines that the relative positions are mutually different from each other in all three sensors, then the routine moves to the processing of step S 116 . 
     In step S 112 , utilizing the functions of the enhanced display unit  58 , the CPU  14  provides an enhanced display at the relative positions after excluding the sensor that was not consistent with the others. For example, in a case in which the mounting position of the rear right-side camera  30  has become misaligned so that the relative position of the motorcycle  100  as detected by the rear right-side camera  30  is not consistent with the relative positions from the other sensors, the enhanced display unit  58  provides an enhanced display at a position that is calculated based on the relative positions detected by the rear camera  28  and the right-side radar  34 . 
     Next, in step S 114 , utilizing the functions of the display processing unit  56 , the CPU  14  switches the composite image  70 D that was being displayed on the electronic interior mirror  38  to separate images. In other words, as is shown in  FIG. 7 , the first image  70 A, the second image, and the third image  70 C are displayed as individual images on the electronic interior mirror  38 . Moreover, utilizing the functions of the warning display unit  60 , the CPU  14  also displays the warning content  74  superimposed on the second image  70 B that was acquired by the rear right-side mirror  30  at the electronic display unit  38 . The CPU  14  then ends the display processing. 
     If it is determined in step S 108  that the relative positions are mutually different from each other in all of the three sensors, then, in step S 116 , the CPU  14  provides an enhanced display based on the closest relative position. For example, in a case in which the relative positions detected by all of the sensors are mutually different from each other, and the relative position of the motorcycle  100  detected by the right-side radar  34  is the closest, then utilizing the functions of the enhanced display unit  58 , the CPU  14  provides an enhanced display based on the relative position of the motorcycle  100  acquired from the right-side radar  34 . 
     Next, in step S 118 , utilizing the functions of the display processing unit  56 , the CPU  14  switches the composite image  70 D that was being displayed on the electronic interior mirror  38  to separate images. In other words, as is shown in  FIG. 8 , the first image  70 A, the second image, and the third image  70 C are displayed as individual images on the electronic interior mirror  38 . Moreover, utilizing the functions of the warning display unit  60 , the CPU  14  also displays warning content superimposed on all of the images of the first image  70 A, the second image  70 B, and the third image  70 C that correspond to sensors that have detected the target. Here, warning content is displayed superimposed on the first image  70 A and the second image  70 B. The CPU  14  then ends the display processing. 
     As has been described above, in the vehicle periphery monitoring device  10  according to the present exemplary embodiment, in a case in which it is determined by the target position determination unit  54  that the relative positions of a target are mutually consistent with each other in a plurality of sensors, the display processing unit  56  displays the single composite image  70 D that is formed by combining together the first image  70 A, the second image  70 B, and the third image  70 C at the electronic interior mirror  38 . As a result, it is possible to easily recognize the position of a target traveling behind the vehicle  12 . 
     Moreover, in a case in which it is determined by the target position determination unit  54  that the relative positions of the target are not mutually consistent with each other, the display processing unit  56  displays the first image  70 A, the second image  70 B, and the third image  70 C respectively as individual images adjacent to each other on the display unit. By displaying individual images on the electronic interior mirror  38  in this way if the camera mounting position of any one of the rear camera  28 , the rear right-side camera  30 , and the rear left-side camera  32  is out of alignment, there is no possibility of a composite image containing a misaligned image being displayed on the electronic interior mirror  38 . As a result, in a structure that displays composite images, it is possible to inhibit composite images that are incorrect because of camera misalignment from being displayed. 
     Furthermore, in the present exemplary embodiment, by providing an enhanced display of targets that are approaching the vehicle  12  via the enhanced display unit  58 , it is possible to draw the attention of a vehicle occupant to the target. In particular, the enhanced display unit  58  of the present exemplary embodiment provides an enhanced display based on the relative positions of the target acquired from the remaining sensors after excluding the information from the sensor having a relative position for the target that was not consistent with that of the other sensors. As a result, it is possible to inhibit an enhanced display from being provided at an incorrect position. 
     Furthermore, in the present exemplary embodiment, in a case in which the relative positions of the sensors are all mutually different from each other, the enhanced display unit  58  provides an enhanced display based on the relative position of the target acquired from the sensor having a detected relative position of the target is the closest to the vehicle  12 . As a result, information having a high degree of urgency can be made known to a vehicle occupant. 
     Moreover, in the present exemplary embodiment, by displaying warning content superimposed on the rear image acquired by the sensor having a mounting position has a possibility of being misaligned, it is possible to alert a vehicle occupant as to this possibility. Moreover, in a case in which the relative positions of the target detected by the rear camera  28 , the rear right-side camera  30 , and the rear left-side camera  32  are all mutually different from each other, warning content is displayed superimposed on all of the images of the first image  70 A, the second image  70 B, and the third image  70 C that correspond to those sensors that have detected the target. As a consequence, because warning content are displayed superimposed on a plurality of images, it is possible to encourage a vehicle occupant to make a vehicle inspection or the like. 
     Furthermore, as is the case in the present exemplary embodiment, by detecting relative positions of a target using the right-side radar  34  and the left-side radar  36  for obstacle detection, there is no need to install dedicated sensors so that an increase in the number of components is inhibited. 
     The vehicle periphery monitoring device  10  according to the present exemplary embodiment has been described above, however, various modifications and the like may be made to the present disclosure insofar as they do not depart from the spirit or scope of the present disclosure. For example, as is shown in  FIG. 1 , the vehicle periphery monitoring device  10  of the above-described exemplary embodiment is an ECU that is mounted in the vehicle  12 , however, the present disclosure is not limited to this, and it is also possible to employ a structure in which the vehicle periphery monitoring device  10  is provided externally to the vehicle  12 . If the vehicle periphery monitoring device  10  is provided externally to the vehicle  12 , then images acquired by the rear camera  28 , the rear right-side camera  30 , and the rear left-side camera  32  may be obtained via a network. 
     Moreover, in the above-described exemplary embodiment, the rear camera  28 , the rear right-side camera  30 , the rear left-side camera  32 , the right-side radar  34 , and the left-side radar  36  are used as sensors to detect the relative positions of a target, however, the present disclosure is not limited to this. For example, it is also possible to use a back guide monitor that is used to ensure there is a clear area behind a vehicle when that vehicle is reversing as a sensor. In addition, it is also possible to use LIDAR (Laser Imaging Detection And Ranging) that is used to detect peripheral information around a vehicle as a sensor. Furthermore, it is also possible for the relative positions of a target to be detected using only three sensors, namely, the rear camera  28 , the rear right-side camera  30 , and the rear left-side camera  32 . 
     Furthermore, in the above-described exemplary embodiment, the enhanced display unit  58  provides an enhanced display by displaying the frame-shaped mark M superimposed on a target, however, the present disclosure is not limited to this. For example, it is also possible to display a predetermined mark superimposed on the target. Additionally, it is also possible for the mark to change as the target comes closer. 
     Furthermore, in the above-described exemplary embodiment, a structure that displays images on the electronic interior mirror  38  is used as a display unit, however, the present disclosure is not limited to this. For example, in addition to the electronic interior mirror  38 , it is also possible to display a composite image on a center display or the like that is installed in the instrument panel. 
     Furthermore, it is also possible for the processing executed by the CPU  14  after reading software (i.e., a program) to instead be executed by various types of processors other than a CPU. Examples of other types of processors in this case include PLD (Programmable Logic Devices) whose circuit structure can be altered after manufacturing such as an FPGA (Field-Programmable Gate Array), and dedicated electrical circuits and the like which are processors having a circuit structure that is designed specifically in order to execute a particular processing such as ASIC (Application Specific Integrated Circuits). In addition, the display processing may be executed by just one type from among these various types of processors, or by a combination of two or more processors that are either the same type or are mutually different types (for example by a plurality of FPGA or by a combination of a CPU and an FPGA). Furthermore, the hardware structures of these different types of processors are, more specifically, electrical circuits obtained by combining circuit elements such as semiconductor elements and the like. 
     Moreover, in the above-described exemplary embodiment, the storage  20  is employed as a storage unit, however, the present disclosure is not limited to this. For example, it is also possible for the various types of programs to be stored on a non-transitory storage medium such as a CD (Compact Disk), a DVD (Digital Versatile Disk), and a USB (Universal Serial Bus) memory, and then distributed. Moreover, it is also possible to employ a system in which each program is downloaded from an external device via a network.