Patent Publication Number: US-11657618-B2

Title: Display apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 16/263,159 filed on Jan. 31, 2019, which is a continuation of U.S. patent application Ser. No. 14/241,735 filed on Feb. 27, 2014, which is the national phase of PCT Application No. PCT/JP2012/005321 filed Aug. 24, 2012, which claims priority from Japanese Patent Application No. 2011-184416 filed Aug. 26, 2011 and Japanese Patent Application No. 2011-184419 filed Aug. 26, 2011. The contents of all of these applications are incorporated by reference herein in their entireties. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a drive assistance apparatus that gives notice of a potential collision with an obstacle during parking. 
     BACKGROUND ART 
     Hitherto, there is a known drive assistance apparatus that combines images captured using a plurality of cameras into an all-around view image indicating the all-around view of a vehicle and displays the combined image to assist driving (see Patent Literature (hereinafter, referred to as “PTL”) 1, for example). 
     However, the all-around view image is created by combining the camera images projected onto a road surface position, so that a three-dimensional object disappears (dead angle) at a junction boundary between adjacent cameras. In general, the junction boundary between the camera images is set in the vicinity of four corners of a vehicle due to restrictions such as the installation of position of the camera or the angle of view of the camera, or the density of pixels. Such four corners of the vehicle are also likely to become blind zones of the visually observable area of the driver. For this reason, the deriver may continue driving without realizing the three-dimensional object in the vicinity of the junction boundary and thus cause a collision between the vehicle and the three-dimensional object. 
     In order to solve such a problem, in the related art, the position or angle of the junction boundary between camera images is changed in association with a sonar unit, a gear, or the like (see PTL 2 and PTL 3, for example). 
     CITATION LIST 
     Patent Literature 
     PTL 1 
     International Publication No. WO 00/64175 
     PTL 2 
     Japanese Patent Application Laid-Open No. 2007-104373 
     PTL 3 
     Japanese Patent Application Laid-Open No. 2006-121587 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, with the technique of the related art, there is a problem in that a blind spot still exists in the close proximity of the vehicle (a distance within a few tens of centimeters from the vehicle). In particular, there is a concern that a driver may not realize the presence of the three-dimensional object due to the disappearance of the three-dimensional object on the bird&#39;s-eye view image although the presence of the three-dimensional object has been detected by the sonar unit, for example. 
     An object of the present invention is thus to provide a drive assistance apparatus capable of preventing a three-dimensional object from disappearing in the close proximity of a vehicle in a bird&#39;s-eye view image although the three-dimensional object has been detected. 
     Solution to Problem 
     In a drive assistance apparatus according to an aspect of the present invention, a sensor includes a detection range that is within the angle of view of a second imaging section, and when the sensor detects a three-dimensional object, an image processing section creates a bird&#39;s-eye view image by combining an image captured by the second imaging section and images captured by a first imaging section and sets the detection range of the sensor to be within a region of the bird&#39;s-eye view image based on the image captured by the second imaging section in the bird&#39;s-eye view image. 
     Advantageous Effects of Invention 
     According to the drive assistance apparatus of the present invention, it is possible to prevent a three-dimensional object from disappearing in the close proximity of a vehicle in a bird&#39;s-eye view image although the three-dimensional object has been detected, and thus to bring about the effect of making it easier for the driver to realize the three-dimensional object in the close proximity of the vehicle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram illustrating a configuration of a drive assistance apparatus according to Embodiment 1 of the present invention; 
         FIG.  2    is a diagram illustrating the positions at which first and second imaging sections are mounted to a vehicle according to Embodiment 1 of the present invention; 
         FIG.  3    is a diagram illustrating the positions at which sonar units are mounted to a vehicle according to Embodiment 1 of the present invention; 
         FIG.  4    is a diagram illustrating an angle of view of the second imaging section and a detection range of a sonar unit according to Embodiment 1 of the present invention in a horizontal plane; 
         FIG.  5    is a diagram illustrating a three-dimensional object according to Embodiment 1 of the present invention; 
         FIG.  6    is a flowchart illustrating drive assistance processing using the drive assistance apparatus according to Embodiment 1 of the present invention; 
         FIG.  7    is a diagram illustrating a bird&#39;s-eye view image created in step S 65  of  FIG.  6   ; 
         FIG.  8    is a diagram illustrating a blind spot region generated in the bird&#39;s-eye view image of  FIG.  7   ; 
         FIG.  9    is a diagram illustrating a boundary of the blind spot region of  FIG.  8   ; 
         FIG.  10    is a block diagram illustrating a configuration of a drive assistance apparatus according to Embodiment 2 of the present invention; 
         FIG.  11    is a diagram illustrating the positions at which first and second imaging sections are mounted to a vehicle according to Embodiment 2 of the present invention; 
         FIG.  12    is a diagram illustrating the positions at which sonar units are mounted to a vehicle according to Embodiment 2 of the present invention; 
         FIG.  13    is a diagram illustrating an angle of view of the second imaging section and a detection range of the sonar unit according to Embodiment 2 of the present invention in a horizontal plane; and 
         FIG.  14    is a flowchart illustrating drive assistance processing using the drive assistance apparatus according to Embodiment 2 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
     Hereinafter, a drive assistance apparatus according to Embodiment 1 of the present invention will be described with reference to the accompanying drawings. Meanwhile, in the present embodiment, a vehicle having a steering wheel on its right side will be described as an example. In a case of a vehicle having a steering wheel on its left hand side, the left and right are reversed. 
       FIG.  1    is a block diagram illustrating a configuration of a drive assistance apparatus according to Embodiment 1 of the present invention. 
     In  FIG.  1   , drive assistance apparatus  1  includes an imaging electric control unit (ECU) configured to perform image processing and includes volatile memory  2 , image processing section  3 , non-volatile memory  4 , control section  5 , and bus  6  for connecting these components to each other. Drive assistance apparatus  1  is connected to first imaging section  7 , input section  8 , vehicle speed sensor  9 , steering sensor  10 , gear  11 , sonar section  12 , display section  13 , and second imaging section  14 . Drive assistance apparatus  1  may include input section  8 , vehicle speed sensor  9 , steering sensor  10 , gear  11 , sonar section  12 , display section  13 , and second imaging section  14 . Meanwhile, steering sensor  10  and a steering signal which are illustrated in  FIG.  1    may also be referred to as “steering angle sensor  10 ” and a “steering angle signal,” respectively. 
     Volatile memory  2  includes a video memory or a random access memory (RAM), for example. Volatile memory  2  is connected to first imaging section  7 . In addition, volatile memory  2  is connected to second imaging section  14 . Volatile memory  2  temporarily stores image data items obtained from captured images which are received from first imaging section  7  and second imaging section  14  at every predetermined time. The image data items stored in volatile memory  2  are output to image processing section  3  through bus  6 . 
     Image processing section  3  includes an application specific integrated circuit (ASIC) or very large scale integration (VLSI) chip, for example. Image processing section  3  is connected to display section  13 . Image processing section  3  performs the conversion of a viewpoint on the image data items which are received from volatile memory  2  and creates a bird&#39;s-eye view image in which the image data items received from non-volatile memory  4  are superimposed on each other, at every predetermined time. Image processing section  3  may create a combined image in which ordinary images without conversion of a viewpoint are arranged as the bird&#39;s-eye view image. The technique disclosed in International Publication No. WO 00/64175 can be used as a method of converting a viewpoint, for example. Image processing section  3  outputs the combined images which are created at every predetermined time as display images to display section  13 . 
     Non-volatile memory  4  includes a flash memory or a read only memory (ROM), for example. Non-volatile memory  4  stores various image data items such as an image data of a vehicle for which the drive assistance apparatus is used (hereinafter, referred to as “host vehicle”) and a data table regarding a display method in accordance with driving situations. The image data items stored in non-volatile memory  4  are read out in response to a command of control section  5 , and is used for various image processing using image processing section  3 . 
     Control section  5  includes a central processing unit (CPU) or large scale integration (LSI) chip, for example. Control section  5  is connected to input section  8 , vehicle speed sensor  9 , steering sensor  10 , gear  11 , and sonar section  12 . Control section  5  controls the image processing of image processing section  3 , data read out from volatile memory  2  or non-volatile memory  4 , input from first imaging section  7  or second imaging section  14 , and output to display section  13  on the basis of various signals input from input section  8 , vehicle speed sensor  9 , steering sensor  10 , gear  11 , and sonar section  12 . 
     First imaging section  7  includes four cameras. On the other hand, second imaging section  14  includes one camera. First imaging section  7  and second imaging section  14  input images captured at every predetermined time to volatile memory  2  of drive assistance apparatus  1 . First imaging section  7  is mounted to a vehicle body so as to be capable of capturing images of all-around view of a host vehicle. In addition, second imaging section  14  is installed at a left front corner of the vehicle. The positions at which first imaging section  7  and second imaging section  14  are mounted to the vehicle body will be described below. 
       FIG.  2    is a diagram illustrating the positions at which first imaging section  7  and second imaging section  14  are mounted to a vehicle. As illustrated in  FIG.  2   , first imaging section  7  includes front camera  7   a , right camera  7   b , left camera  7   c , and rear camera  7   d . For example, front camera  7   a  and rear camera  7   d  are mounted to the front and rear bumpers of the vehicle body, respectively. For example, right camera  7   b  and left camera  7   c  are mounted to the lower portions of right and left door mirrors of the host vehicle. On the other hand, second imaging section  14  is mounted to the left front corner of the host vehicle. 
     Input section  8  includes a touch panel, a remote controller, or a switch, for example. When input section  8  is formed of a touch panel, the input section may be provided to display section  13 . 
     Vehicle speed sensor  9 , steering sensor  10 , gear  11 , and sonar section  12  output a vehicle speed signal indicating the vehicle speed of the host vehicle, a steering angle signal indicating a steering angle, a gear signal indicating the state of a shift lever, a detected signal and distance signal of a three-dimensional object to control section  5 , respectively. Sonar section  12  includes eight sonar units which are mounted to four places of four corners of the vehicle body of the host vehicle and four places of the front and back of the vehicle body, respectively. The positions at which the sonar units of sonar section  12  are mounted to the vehicle body will be described below. 
       FIG.  3    is a diagram illustrating the positions at which the sonar units of sonar section  12  are mounted to a vehicle. As illustrated in  FIG.  3   , sonar section  12  includes left front corner sonar unit  12   a , right front corner sonar unit  12   b , left rear corner sonar unit  12   c , right rear corner sonar unit  12   d , left front sonar unit  12   e , right front sonar unit  12   f , left rear sonar unit  12   g , and right rear sonar unit  12   h . As illustrated in  FIG.  3   , respective horizontal detection ranges  16   e  to  16   h  of left front sonar unit  12   e , right front sonar unit  12   f , left rear sonar unit  12   g , and right rear sonar unit  12   h  are set to be narrower than respective horizontal detection ranges  16   a  to  16   d  of left front corner sonar unit  12   a , right front corner sonar unit  12   b , left rear corner sonar unit  12   c , and right rear corner sonar unit  12   d . Next, a relation between the detection range of left front corner sonar unit  12   a  and an angle of view of second imaging section  14  will be described. 
       FIG.  4    is a diagram illustrating the angle of view of second imaging section  14  and the horizontal detection range of left front corner sonar unit  12   a . As illustrated in  FIG.  0 . 4   , the angle of view  17  of second imaging section  14  is set to approximately 180 degrees in a horizontal plane. In addition, detection range  16   a  of left front corner sonar unit  12   a  is included within the angle of view  17  of second imaging section  14 . That is, the entirety of detection range  16   a  of left front corner sonar unit  12   a  is included within the angle of view  17  of second imaging section  14 . 
     It is preferable that second imaging section  14  be mounted further upward of the vehicle body than left front corner sonar unit  12   a . Thus, detection range  16   a  of left front corner sonar unit  12   a  has a tendency for being three-dimensionally included within the angle of view  17  of second imaging section  14 . In addition, it is preferable that optical axes of second imaging section  14  and left front corner sonar unit  12   a  be substantially equal to each other. Accordingly, a deviation of detection range  16   a  of left front corner sonar unit  12   a  within angle of view  17  of second imaging section  14  becomes smaller, and thus it is possible to reduce a concern that detection range  16   a  of left front corner sonar unit  12   a  may partially protrude outside the angle of view  17  of second imaging section  14 . 
     Display section  13  includes, for example, a navigation apparatus or a display section provided to a rear seat. Display section  13  displays a combined image input from image processing section  3 . The combined image may be only a bird&#39;s-eye view image, or may be an image in which a bird&#39;s-eye view image and a normal image are arranged in parallel. When a blind spot is present in the vicinity of a boundary of the bird&#39;s-eye view image, a three-dimensional object disappears. Here, the three-dimensional object in this embodiment will be illustrated. 
       FIG.  5    is a diagram illustrating a three-dimensional object in this embodiment. As illustrated in  FIG.  5   , Color Cone (registered trademark) having a width of approximately 30 cm, a depth of approximately 30 cm, and a height of approximately 50 cm is assumed to be the three-dimensional object in this embodiment. When half or more than half of Color Cone (registered trademark) disappears three-dimensionally on a bird&#39;s-eye view image, it means that a blind spot is present in the vicinity of a boundary of the bird&#39;s-eye view image. 
     Next, the drive assistance processing using control section  5  will be described. 
       FIG.  6    is a flowchart illustrating the drive assistance process using control section  5 . 
     First, as shown in step S 61 , control section  5  determines whether the shift lever is in a reversed state, on the basis of the gear signal input from gear  11 . 
     In a case of YES in step S 61 , image processing section  3  creates a bird&#39;s-eye view image using an image captured by first imaging section  7  and acquired from volatile memory  2 , in response to a command of control section  5 . In addition, as shown in step S 62 , display section  13  displays the created bird&#39;s-eye view image in parallel with a rear image of rear camera  7   d  which is acquired from volatile memory  2 . 
     Next, in a case of NO in step S 61 , as shown in step S 63 , image processing section  3  creates a bird&#39;s-eye view image using an image captured by first imaging section  7  and acquired from volatile memory  2 , in response to a command of control section  5 , and display section  13  displays the created bird&#39;s-eye view image in parallel with a front image of front camera  7   a  which is acquired from volatile memory  2 . 
     Next, as shown in step S 64 , control section  5  determines whether a three-dimensional object is present at a left front corner of a host vehicle, on the basis of detected results of sonar section  12 . That is, control section  5  determines whether left front corner sonar unit  12   a  has detected a three-dimensional object. In a case of NO in step S 64 , the processing of step S 61  is performed again. 
     On the other hand, in a case of YES in step S 64 , as shown in step S 65 , image processing section  3  newly creates a bird&#39;s-eye view image using the image captured by first imaging section  7  and an image captured by second imaging section  14  and causes display section  13  to display the created bird&#39;s-eye view image. That is, only when left front corner sonar unit  12   a  detects a three-dimensional object, image processing section  3  creates a bird&#39;s-eye view image using images captured by four cameras  7   a  to  7   d  of first imaging section  7  and the image captured by second imaging section  14 . Conversely, when left front corner sonar unit  12   a  has not detected the three-dimensional object located at the left front corner of the host vehicle, image processing section  3  creates the bird&#39;s-eye view image so far using only the images captured by four cameras  7   a  to  7   d  of first imaging section  7 . Differences between the bird&#39;s-eye view image created in step S 65  and an ordinary bird&#39;s-eye view image created by the images captured by four cameras  7   a  to  7   d  of first imaging section  7  will be described later. 
     Next, as shown in step S 66 , control section  5  determines whether the moving direction of the host vehicle is the forward direction. At this time, control section  5  specifies the moving direction of the host vehicle on the basis of the gear signal input from gear  11 . That is, control section  5  determines from the gear signal whether the shift lever is set to the front. 
     In a case of YES in step S 66 , as shown in step S 67 , control section  5  causes display section  13  to display the image captured by second imaging section  14 , instead of the rear image displayed in parallel on display section  13  by step S 62  or the front image displayed in parallel on display section  13  by step S 63 . 
     After the processing of step S 67 , or in a case of NO in step S 66 , as shown in step S 68 , control section  5  determines whether the termination of a drive assistance mode has been detected. In a case of YES in step S 68 , control section  5  terminates the drive assistance processing. For example, when an input of the termination of the drive assistance mode is received from input section  8 , control section  5  terminates the drive assistance processing. On the other hand, in a case of NO in step S 68 , control section  5  performs the processing of step S 61  again. 
     Next, a description will be given of differences between the bird&#39;s-eye view image created in step S 65  when left front corner sonar unit  12   a  detects the three-dimensional object and an ordinary bird&#39;s-eye view image created by the images captured by four cameras  7   a  to  7   d  of first imaging section  7 .  FIG.  7    is a diagram illustrating the bird&#39;s-eye view image created in step S 65 , using an image. 
     As illustrated on the left side of  FIG.  7   , before left front corner sonar unit  12   a  detects a three-dimensional object, image processing section  3  creates bird&#39;s-eye view image  40   a  using the images captured by four cameras  7   a  to  7   d  of first imaging section  7 . Image  21  of a host vehicle is superimposed on the center of bird&#39;s-eye view image  40   a . Regions  22  to  25  of bird&#39;s-eye view image  40   a  correspond to viewpoint-converted images of the images captured by front camera  7   a , right camera  7   b , left camera  7   c , and rear camera  7   d , respectively. The junction surfaces of regions  22  to  25  are shown as combination boundaries  31  to  34 , respectively. When left front corner sonar unit  12   a  detects three-dimensional object  41  in the vicinity of the host vehicle, a blind spot is generated at combination boundary  34  in the bird&#39;s-eye view image itself using the images captured by four cameras  7   a  to  7   d  of first imaging section  7 , and thus three-dimensional object  41  disappears. 
     Consequently, when left front corner sonar unit  12   a  detects the three-dimensional object, as illustrated on the right side of  FIG.  7   , image processing section  3  creates bird&#39;s-eye view image  40   b  using not only the images captured by four cameras  7   a  to  7   d  of first imaging section  7  but also an image captured by second imaging section  14  that captures an image of the left front corner in which three-dimensional object  41  is detected. Regions  22  to  26  of bird&#39;s-eye view image  40   b  correspond to viewpoint-converted images of the images captured by front camera  7   a , right camera  7   b , left camera  7   c , rear camera  7   d , and second imaging section  14 , respectively. Combination boundary  35  between front camera  7   a  and second imaging section  14  and combination boundary  36  between left camera  7   d  and second imaging section  14  are set to positions at which region  26  of the viewpoint-converted image of second imaging section  14  can include the detection range of left front corner sonar unit  12   a . In other words, combination boundaries  35  and  36  are set outside the detection range of left front corner sonar unit  12   a . Thus, three-dimensional object  41  detected by left front corner sonar unit  12   a  does not disappear in the vicinity of combination boundaries  35  and  36  in bird&#39;s-eye view image  40   b , and the visibility of three-dimensional object  41  within region  26  is maintained. In particular, since a falling-down direction of three-dimensional object  41  in the vicinity of the combination boundary does not rapidly fluctuate, a driver can view three-dimensional object  41  without feeling a sense of discomfort. In addition, three-dimensional object  41  falls down in a direction which is radially away from the vehicle as a reference point, and thus it is possible to intuitively ascertain the position and direction of three-dimensional object  41 . 
     Meanwhile, in order to set three-dimensional object  41  to be distant from combination boundaries  35  and  36  as far as possible, it is fundamentally preferable that combination boundaries  35  and  36  be set to be as close as possible to the angle of view of second imaging section  14 . On the other hand, if combination boundaries  35  and  36  are set to be substantially equal to the angle of view of second imaging section  14 , glare of the outside of the original angle of view may occur when second imaging section  14  deviates from its mounting position. For this reason, it is preferable that combination boundaries  35  and  36  be set to positions located approximately several degrees to tens of degrees inward with respect to the angle of view of second imaging section  14 . 
     Next, a blind spot region of the bird&#39;s-eye view image created in step S 65  and a blind spot region of an ordinary bird&#39;s-eye view image created by the images captured by four cameras  7   a  to  7   d  of first imaging section  7  will be described.  FIG.  8    is a diagram illustrating a dead angle region generated in the bird&#39;s-eye view image of  FIG.  7   . 
     Ordinary bird&#39;s-eye view image  50   a  created by the images captured by four cameras  7   a  to  7   d  of first imaging section  7  is illustrated on the left side of  FIG.  8   . Bird&#39;s-eye view image  50   b  created in step S 65  is illustrated on the right side of  FIG.  8   . In bird&#39;s-eye view images  50   a  and  50   b , a fixed range from host vehicle image  51  is set to blind spot measurement region  52 . The fixed range is set to approximately several tens of cm. For example, the fixed range is set to 50 cm. This indicates a distance at which the host vehicle can move forward in a creeping manner at a speed of approximately 3 km/h and stop with sudden braking. 
     As illustrated on the left side of  FIG.  8   , in ordinary bird&#39;s-eye view image  50   a  created by the images captured by four cameras  7   a  to  7   d  of first imaging section  7 , detection range  53  of left front corner sonar unit  12   a  partially overlaps blind spot region  54  caused by combination boundary  34  between front camera  7   a  and left camera  7   c . When detection range  53  of left front corner sonar unit  12   a  overlaps blind spot region  54 , three-dimensional object  41  disappears within the overlapping range. Consequently, in bird&#39;s-eye view image  50   b  created in step S 65 , combination boundaries  35  and  36  are kept away from detection range  53  of left front corner sonar unit  12   a  using the image captured by second imaging section  14 . Thus, as illustrated on the right side of  FIG.  8   , in bird&#39;s-eye view image  50   b  created in step S 65 , detection range  53  of left front corner sonar unit  12   a  is separated from blind spot region  55  caused by combination boundary  35  between second imaging section  14  and front camera  7   a  and blind spot region  56  caused by combination boundary  36  between second imaging section  14  and left camera  7   d  so as not to overlap the blind spot regions. Accordingly, the three-dimensional object which is present in the detection range of left front corner sonar unit  12   a  is displayed on display section  13  without disappearing on bird&#39;s-eye view image  50   b.    
     Next, a blind spot region caused by a combination boundary of the bird&#39;s-eye view image of  FIG.  8    will be described.  FIG.  9    is a diagram illustrating a boundary of the blind spot region of  FIG.  8   . In  FIG.  9   , an example of bird&#39;s-eye view image  50   a  on the left side of  FIG.  8    will be described. 
     Boundary line  54   a  illustrated on the upper left side of  FIG.  9    indicates a boundary of blind spot region  54  on the left side of the paper of  FIG.  8   . That is, boundary line  54   a  indicates an outer edge of dead angle measurement region  52 . 
     Boundary line  54   b  illustrated on the lower left side of  FIG.  9    indicates a boundary of blind spot region  54  on the lower side of the paper of  FIG.  8   . Boundary line  54   b  indicates a boundary at which a blind spot is generated when three-dimensional object  41  is present within region  25 . When three-dimensional object  41  is moved to the upper side of the paper of  FIG.  9    toward combined boundary  34  between front camera  7   a  and left camera  7   d , half or more than half of three-dimensional object  41  disappears (25 cm or more) in a height direction. The lowermost position of three-dimensional object  41  in the paper of  FIG.  9    serves as a component of boundary line  54   b . Boundary line  54   b  is indicated by a set of the lowermost positions of three-dimensional object  41  in the sheet of  FIG.  9    when gradually moving three-dimensional object  41  to the left side of the sheet of  FIG.  9    to repeatedly perform the same processing. 
     Boundary line  54   c  illustrated on the upper right side of  FIG.  9    indicates a boundary of blind spot region  54  on the right side of the sheet of  FIG.  8   . That is, boundary line  54   c  indicates an outer edge of host vehicle image  51 . 
     Boundary line  54   d  illustrated on the lower right side of  FIG.  9    indicates a boundary of blind spot region  54  on the upper side of the sheet of  FIG.  8   . Boundary line  54   d  indicates a boundary at which a blind spot is generated when three-dimensional object  41  is present within region  22 . When three-dimensional object  41  is moved to the lower side of the sheet of  FIG.  9    toward combination boundary  34  between front camera  7   a  and left camera  7   d , half or more than half of three-dimensional object  41  disappears (15 cm or more) in a width direction. The uppermost position of three-dimensional object  41  in the sheet of  FIG.  9    serves as a component of boundary line  54   d . Boundary line  54   d  is indicated by a set of the uppermost positions of three-dimensional object  41  in the sheet of  FIG.  9    when gradually moving three-dimensional object  41  to the left side of the sheet of  FIG.  9    to repeatedly perform the same processing. 
     A similar method of determining a boundary is applied to blind spot regions  55  and  56  of bird&#39;s-eye view image  50   b  on the right side of  FIG.  8   , and thus the detailed description thereof will be omitted. 
     As described above, according to the present invention, the detection range of left front corner sonar unit  12   a  is included within the angle of view of second imaging section  14 . Thus, when left front corner sonar unit  12   a  detects a three-dimensional object, image processing section  3  combines the image captured by second imaging section  14  and the images captured by four cameras  7   a  to  7   d  of the first imaging section to create bird&#39;s-eye view image  40   b  and sets the detection range of left front corner sonar unit  12   a  to be within a range of the bird&#39;s-eye view image based on the image captured by second imaging section  14  in bird&#39;s-eye view image  40   b . That is, image processing section  3  moves a blind spot of the three-dimensional object outside the detection range of left front corner sonar unit  12   a . Therefore, although left front corner sonar unit  12   a  detects a three-dimensional object, it is possible to prevent the three-dimensional object in the proximity of a host vehicle from disappearing on a bird&#39;s-eye view image of display section  13 . In particular, in this embodiment, rather than all of the four corners of the host vehicle are set as positions where the three-dimensional object in the close proximity of the host vehicle may disappear on the bird&#39;s-eye view image, only the left front side, which is likely to become a blind spot to a driver in a case of a vehicle having a steering wheel on its right hand side. Thus, a selector is no longer necessary in drive assistance apparatus  1  which can only have a limited number of camera input ports, so that it is possible to prevent an increase in size of a control ECU of drive assistance apparatus  1  due to the selector. 
     Meanwhile, in the drive assistance processing illustrated in  FIG.  6    of this embodiment, a bird&#39;s-eye view image and an ordinary image (a front image or a rear image) are displayed in parallel to provide a plurality of determination criteria to the driver to thereby improving the visibility of a three-dimensional object, but it is also possible to display the bird&#39;s-eye view image alone. That is, at least the processing of step S 64  and step S 65  of  FIG.  6    may be performed. Specifically, image processing section  3  combines an image captured by first imaging section  7  and an image captured by second imaging section  14  into a bird&#39;s-eye view image on the basis of common mapping data. Display section  3  displays the bird&#39;s-eye view image. According to such a configuration, the continuity of a display image is maintained before and after a combination boundary of the bird&#39;s-eye view image, and thus it is possible to prevent a driver from feeling a sense of discomfort and to prevent the generation of a blind spot and the disappearance of the three-dimensional object located at the combination boundary of the bird&#39;s-eye view image after detecting the three-dimensional object. 
     In addition, in this embodiment, since a case of a vehicle having a steering wheel on its right hand side is assumed, a three-dimensional object in the vicinity of a left front corner, which is likely to become a blind spot to the driver, is prevented from disappearing on the bird&#39;s-eye view image, using second imaging section  14  and left front corner sonar unit  12   a  which are provided at the left front corner. On the other hand, in a case of a vehicle having a steering wheel on its left hand side, an object is located on the right front side rather than the left front side. That is, in the case of a vehicle having a steering wheel on its left hand side, an installation position of second imaging section  14  in this embodiment is replaced by the right front corner, and left front corner sonar unit  12   a  is replaced by front corner sonar unit  12   b.    
     That is, second imaging section  14  captures an image of a front corner in a direction opposite to the position of the steering wheel of a host vehicle among four corners of the host vehicle. The detection range of sonar section  12  detecting a three-dimensional object, which is present at the front corner in a direction opposite to the position of the steering wheel of the host vehicle, is included within the angle of view of second imaging section  14 . When sonar section  12  detects the three-dimensional object, image processing section  3  creates a bird&#39;s-eye view image by combining the image captured by first imaging section  7  and the image captured by second imaging section  14  and may set the detection range of sonar section  12  to be within a region of the bird&#39;s-eye view image based on the image captured by second imaging section  14  in the bird&#39;s-eye view image. On the other hand, when sonar section  12  has not detected the three-dimensional object which is present at the front corner in the direction opposite to the position of the steering wheel of the host vehicle, image processing section  3  creates a bird&#39;s-eye view image by combining the images captured by first imaging section  7 . 
     Meanwhile, in this embodiment, sonar units which detect three-dimensional objects located at the front and back of a vehicle in sonar section  12  are formed of four sonar units  12   e  to  12   f , but at least two sonar units may be provided in order to detect the three-dimensional objects located at the front and back of the vehicle. 
     In addition, in this embodiment, although sonar section  12  is used as a three-dimensional object detecting section for detecting a three-dimensional object, any means such as an infrared sensor may be used as long as it is a sensor that detects a three-dimensional object. 
     Embodiment 2 
     Next, a drive assistance apparatus according to Embodiment 2 of the present invention will be described with reference to the accompanying drawings. A description similar to that in Embodiment 1 will be given the same reference numerals and signs, and the detailed description thereof will be omitted. 
       FIG.  10    is a block diagram illustrating a configuration of the drive assistance apparatus according to Embodiment 2 of the present invention. In  FIG.  10   , drive assistance apparatus  1  further includes selector  15  with respect to the drive assistance apparatus of Embodiment 1. Drive assistance apparatus  1  is connected to second imaging section  14  through selector  15 . Selector  15  may also be included in drive assistance apparatus  1 . Volatile memory  2  is connected to second imaging section  14  through selector  15 . Control section  5  controls selector  15  based on a signal input from sonar section  12  and selects second imaging section  14 . 
     Second imaging section  14  includes four cameras. First imaging section  7  and second imaging section  14  input images captured at every predetermined time to volatile memory  2  of drive assistance apparatus  1 . Second imaging section  14  is mounted to each of four corners of a vehicle body of a host vehicle. The position at which second imaging section  14  is mounted to the vehicle body will be described below. 
       FIG.  11    is a diagram illustrating the positions at which first imaging section  7  and second imaging section  14  are mounted to a vehicle. As illustrated in  FIG.  11   , second imaging section  14  includes left front corner camera  14   a , right front corner camera  14   b , left rear corner camera  14   c , and right rear corner camera  14   d . Selector  15  selects one of left front corner camera  14   a , right front corner camera  14   b , left rear corner camera  14   c , and right rear corner camera  14   d  on the basis of a command of control section  5 . An image captured by the selected camera is input to volatile memory  2  of drive assistance apparatus  1  at every predetermined time. 
     Sonar section  12  includes four sonar units which are mounted to four corners of the vehicle body of the host vehicle, respectively. The positions at which the sonar units of sonar section  12  are mounted to the vehicle body will be described below. 
       FIG.  12    is a diagram illustrating the positions at which the sonar units of sonar section  12  are mounted to a vehicle, respectively. As illustrated in  FIG.  12   , sonar section  12  includes left front corner sonar unit  12   a , right front corner sonar unit  12   b , left rear corner sonar unit  12   c , and right rear corner sonar unit  12   d . As illustrated in  FIG.  12   , respective horizontal detection ranges  16   a  to  16   d  of left front corner sonar unit  12   a , right front corner sonar unit  12   b , left rear corner sonar unit  12   c , and right rear corner sonar unit  12   d  are each set to equal to or less than 180 degrees. 
       FIG.  13    is a diagram illustrating an angle of view of left front corner camera  14   a  and a horizontal detection range of left front corner sonar unit  12   a . As illustrated in  FIG.  13   , a relation between a detection range of sonar section  12  and an angle of view of second imaging section  14  is similar to the relation shown in  FIG.  4    of Embodiment 1. That is, the angle of view  17   a  of left front corner camera  14   a  is set to approximately 180 degrees in a horizontal plane. Detection range  16   a  of left front corner sonar unit  12   a  is included within the angle of view  17   a  of left front corner camera  14   a . That is, the entirety of detection range  16   a  of left front corner sonar unit  12   a  is included within the angle of view  17   a  of left front corner camera  14   a . Similarly to Embodiment 1, it is preferable that left front corner camera  14   a  be mounted further upward of the vehicle body than left front corner sonar unit  12   a . In addition, it is preferable that optical axes of front corner camera  14   a  and left front corner sonar unit  12   a  be substantially equal to each other. 
     Meanwhile, in  FIG.  13   , as an example, the relation between the detection range of sonar section  12  and the angle of view of second imaging section  14  has been described using the angle of view of left front corner camera  14   a  and the detection range of left front corner sonar unit  12   a , but a similar relation is established with respect to four corners of another vehicle. That is, the detection ranges of right front corner sonar unit  12   b , left rear corner sonar unit  12   c , and right rear corner sonar unit  12   d  are included within the angles of view of right front corner camera  14   b , left rear corner camera  14   c , and right rear corner camera  14   d , respectively. 
     Next, the drive assistance processing using control section  5  will be described. 
       FIG.  14    is a flowchart illustrating the drive assistance processing using control section  5 . The processing of step S 71  to step S 73  is similar to that of corresponding step S 61  to step S 63  of  FIG.  6    of Embodiment 1. In step S 74 , control section  5  determines whether a three-dimensional object is present within a predetermined range in the vicinity of a host vehicle, from detected results of sonar section  12 . In a case of NO in step S 74 , the processing of step S 71  is performed again. On the other hand, in a case of YES in step S 74 , as shown in step S 75 , control section  5  specifies a response location of a three-dimensional object which is present within a shortest distance from a host vehicle. That is, when the number of sonar units detecting a three-dimensional object is one, among sonar units  12   a  to  12   d  provided at four corners of the host vehicle, control section  5  determines that the corner at which the sonar unit detecting the three-dimensional object is disposed is the response location of the three-dimensional object. On the other hand, when the number of sonars detecting a three-dimensional object is two or more, among sonars  12   a  to  12   d  provided at four corners of the host vehicle, control section  5  determines that the corner at which the sonar detecting a three-dimensional object closest to the host vehicle is disposed is the response location of the three-dimensional object, on the basis of distance signals of the host vehicle and the three-dimensional object which are received from sonar section  12 . 
     Next, as shown in step S 76 , image processing section  3  newly creates a bird&#39;s-eye view image using not only an image captured by first imaging section  7  but also an image obtained by capturing the vicinity of the response location of the three-dimensional object closest to the host vehicle which is specified in step S 75  and causes display section  13  to display the created bird&#39;s-eye view image. That is, image processing section  3  creates the bird&#39;s-eye view image using images captured by four cameras  7   a  to  7   d  of first imaging section  7  and an image captured by a camera of sonar section  12  which corresponds to the response location of the three-dimensional object specified in step S 75 , among cameras  14   a  to  14   d  of second imaging section  14 . Differences between the bird&#39;s-eye view image created in step S 76  and an ordinary bird&#39;s-eye view image created by the images captured by four cameras  7   a  to  7   d  of first imaging section  7  are similar to the differences described in Embodiment 1, and thus the detailed description thereof will be omitted. 
     Next, as shown in step S 77 , control section  5  determines whether a three-dimensional object is present in the moving direction of a host vehicle within a shortest distance from the vehicle. At this time, control section  5  specifies the moving direction of the host vehicle on the basis of a gear signal input from gear  11 . That is, control section  5  specifies, from a gear signal, that the moving direction of the vehicle is the forward direction when the shift lever is set to the front and that the moving direction of the vehicle is the backward direction when the shift lever is set to the reverse. In addition, control section  5  compares the specified moving direction and the response location of the three-dimensional object in step S 75  to perform the determination of step S 77 . That is, when the shift lever is set to the front and the moving direction of the vehicle is the forward direction, control section  5  determines, from the gear signal, whether the response location of the three-dimensional object specified in step S 75  is located on the left front side or the right front side. On the other hand, when the shift lever is set to the reverse and the moving direction of the vehicle is the backward direction, control section  5  determines, from the gear signal, whether the three-dimensional object reaction location specified in step S 75  is located on the left rear side or the right rear side. 
     In a case of YES in step S 77 , as shown in step S 78 , control section  5  causes display section  13  to display the image captured by the camera which captures an image of the vicinity of the response location of the three-dimensional object closest to the host vehicle which is specified in step S 65 , in second imaging section  14 , instead of the rear image displayed in parallel on display section  13  by step S 72  or the front image displayed in parallel on display section  13  by step S 73 . After the processing of step S 78 , or in a case of NO in step S 77 , the processing of step S 79  is performed. The processing of step S 79  is similar to that of step S 68  of  FIG.  6    of Embodiment 1, and thus the description thereof will be omitted. 
     As described above, according to the present invention, the detection ranges of sonar unit  12   a  to sonar unit  12   d  are included within the angles of view of corner camera  14   a  to corner camera  14   d , respectively. When sonar unit  12   a  to sonar unit  12   d  detect a three-dimensional object, a corner camera corresponding to the sonar detecting a three-dimensional object closest to a vehicle is selected by selector  15 . Image processing section  3  creates bird&#39;s-eye view image  40   b  by combining an image captured by the selected corner camera and images captured by four cameras  7   a  to  7   d  of first imaging section  7  and causes a detection range of the sonar unit to be within a region of the bird&#39;s-eye view image based on the image captured by the corner camera in bird&#39;s-eye view image  40   b . That is, image processing section  3  moves a blind spot of the three-dimensional object outside the detection range of sonar section  12 . Therefore, although sonar section  12  detects a three-dimensional object, it is possible to prevent the three-dimensional object in the close proximity of a host vehicle from disappearing on a bird&#39;s-eye view image of display section  13 . 
     INDUSTRIAL APPLICABILITY 
     The drive assistance apparatus of the present invention is useful in that, when a three-dimensional object located at one of four corners of a host vehicle is detected using a sonar unit in particular, the driving assistance apparatus displays the three-dimensional object on a bird&#39;s-eye view image without disappearance of the three-dimensional object, which in turn, allows the driver to easily realize the three-dimensional object. 
     REFERENCE SIGNS LIST 
     
         
           1  Drive assistance apparatus 
           3  Image processing section 
           5  Control section 
           7  First imaging section 
           12  Sonar section 
           14  Second imaging section