Abstract:
A display device for a vehicle which includes: an image-taking unit which takes images of an area ahead of the vehicle at predetermined intervals; a display which displays the images taken by the image-taking unit; and a controller which divides a display area of the display into a plurality of areas including a center area and a right-and-left side area, wherein the controller sets a first interval for the image-taking unit for taking images to be displayed in the right-and-left side area of the display to become longer than a second interval for the image-taking unit for taking images to be displayed in the center area.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a display device for a vehicle.  
         [0003]     Priority is claimed on Japanese Patent Application No. 2005-151292, filed May 24, 2005, the content of which is incorporated herein by reference.  
         [0004]     2. Description of Related Art  
         [0005]     A driving support system for a vehicle which detects conditions of roads based on images of the area ahead of the vehicle is known (see, for example, Japanese Unexamined Patent Application, First Publication No. H08-253059). In the support system, the images are captured by a camera disposed in the vehicle, and images made by the system, reflecting the conditions of roads detected by the system, are displayed on a display provided on the front window or on the dashboard of the vehicle.  
         [0006]     In the driving support system of the related art, it has been impossible to modify the contents of the image to be displayed in accordance with changes of traveling conditions of the vehicle or the ability of occupants to view the surroundings because the images are made only based on the images captured by the camera. Therefore, there has been a problem in that the support system cannot assist the occupant&#39;s ability to view the surroundings when this ability declines in accordance with a change of the traveling conditions of the vehicle.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention was made in view of the aforementioned circumstances, and it has as an object to provide a display device for a vehicle which can properly assist an occupant&#39;s ability to view the surroundings, this ability declining in accordance with traveling conditions of the vehicle.  
         [0008]     A first aspect of the present invention is a display device for a vehicle, including an image-taking unit which takes images of an area ahead of the vehicle at predetermined intervals; a display which displays the images taken by the image-taking unit; and a controller which divides the display area of the display into a plurality of areas including a center area and right-and-left side area, wherein the controller sets a first interval for the image-taking unit for taking images to be displayed in the right-and-left side area to become longer than a second interval for the image-taking unit for taking images to be displayed in the center area.  
         [0009]     In the aforementioned display device, a displaying period of the images of areas in the occupant&#39;s field of view where the ability of the occupant to view the surroundings relatively declines during driving (that is, images displayed in the right-and-left side area) is extended in accordance with an extension of the first interval. Therefore, the display device can allow the occupant to view the images properly and compensate for the declined ability even when kinetic vision of the occupant declines and its field of view is narrowed in accordance with a change in traveling conditions of the vehicle (for example, acceleration).  
         [0010]     The display device of the present invention may further include a velocity measuring unit which measures a velocity of the vehicle, wherein the controller controls a width of the center area to be narrower and controls a width of the right-and-left side area to be wider in accordance with an increase of the velocity measured by the velocity measuring unit.  
         [0011]     In this case, the display device can compensate for the occupant&#39;s declined ability to view the surroundings by widening the right-and-left side area when the field of view of the occupant is narrowed in accordance with an increase of the velocity of the vehicle.  
         [0012]     The image-taking unit may include a first camera which takes images to be displayed in the right-and-left side area and a second camera which takes images to be displayed in the center area, and the controller may set a shutter speed of the first camera to be faster than a shutter speed of the second camera.  
         [0013]     In this case, the display device can provide clearer images by making the shutter speed for images to be displayed on the right-and-left side area faster than that for images to be displayed on the center area; thereby the occupant&#39;s ability to view the surroundings when driving can be improved.  
         [0014]     The controller may control the display so as to display a moving picture taken by the image-taking unit in the center area. In this case, the display device allows the occupant to view the surroundings as if the occupant were actually viewing the surroundings by displaying moving pictures in the field of view of the occupant when the occupant&#39;s ability to view the surroundings is maintained when driving (that is, the center area).  
         [0015]     The display device of the present invention may further include a steering angle sensor which measures a steering angle of the vehicle, wherein the controller determines one of a direction of image taking of the image-taking unit and areas in the images taken by the image-taking unit to be displayed in the display, in accordance with the steering angle measured by the steering angle sensor.  
         [0016]     In this case, when the controller sets an area in images taken by the image-taking unit and controls the display to display images of the area, appropriate images can be displayed in both the center area and the right-and-left side area in accordance with the driver&#39;s intention in driving, and thereby the driver&#39;s ability to view the surroundings can be properly assisted. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a diagram showing a constitution of a display device for a vehicle of an embodiment of the present invention.  
         [0018]      FIG. 2  is a diagram showing an example of timings for obtaining images for the center area and the right-and-left side area, in a vehicle at low speed and high speed.  
         [0019]      FIG. 3  is a diagram showing an example of the field of view of a driver and a combined image.  
         [0020]      FIG. 4  is a flowchart showing the operation of the display device of the present embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Hereinbelow, a display device for a vehicle of an embodiment of the present invention is described with reference to the accompanying drawings. As shown in  FIG. 1 , a display device  10  of the present embodiment has a center area imaging unit  11 , a right-and-left side area imaging unit  12 , a steering angle sensor  13 , a wheel speed sensor  14 , a processing unit  15  having an electrical circuit including a CPU, and a display  16 .  
         [0022]     The center area imaging unit  11  has a camera  11   a  for the center area and an image processing unit  11   b  for the center area, and the right-and-left side imaging unit  12  has a camera  12   a  for the right-and-left side area and an image processing unit  12   b  for right-and-left side area.  
         [0023]     The cameras  11   a  and  12   a  are cameras such as a CCD camera or a CMOS camera which can obtain images in the range of visible light or in the infrared range. The cameras  11   a  and  12   a  are disposed in a cabin of the vehicle and obtain images of a predetermined area ahead of the vehicle through a windshield.  
         [0024]     The processing units  11   b  and  12   b  generate images for the center area and the right-and-left side area consisting of pixels of a two-dimensional array by performing a predetermined processing such as filtering and binarization on the images obtained by the cameras  11   a  and  12   a  and send them to the processing unit  15 .  
         [0025]     The steering angle sensor  13  is, for example, a rotary encoder disposed on a steering pivot. The steering angle sensor  13  measures the direction and the magnitude of the steering angle operated by a driver (the steering angle of a steering wheel). The wheel speed sensor  14  measures the rotation speed of each wheel of the vehicle.  
         [0026]     The constitution of the processing unit  15  shall be described. A center area image obtaining unit  21  obtains images for the center area from the center area imaging unit  11  and sends them to an image combining unit  29 . A right-and-left side area image obtaining unit  22  obtains images for the right-and-left side area from the right-and-left side area imaging unit  12  and sends them to the image combining unit  29 . A steering angle computing unit  23  computes the direction and the magnitude of the steering angle (the actual steering angle of the vehicle) based on a signal showing the direction and the magnitude of the steering angle sent from the steering angle sensor  13 . An imaging angle setting unit  24  sets imaging directions and imaging angles (for example, the imaging angle with respect to a horizontal line) of the cameras  11   a  and  12   a  in accordance with the actual steering angle computed by the steering angle computing unit  23 . The imaging angle setting unit  24  outputs information about the imaging direction to an imaging condition controller  28  and to the image combining unit  29 .  
         [0027]     A velocity computing unit  25  computes the velocity of the vehicle based on the rotation speed of each wheel sent from the wheel speed sensor  14 . A deceleration computing unit  26  computes the deceleration of the vehicle based on the rotation speed of each wheel sent from the wheel speed sensor  14 . A traveling condition determination unit  27  determines the traveling condition of the vehicle based on the velocity of the vehicle computed by the velocity computing unit  25  and the deceleration of the vehicle computed by the deceleration computing unit  26 . The traveling condition determination unit  27  outputs a result of the determination to the imaging condition controller  28  and to the image combining unit  29 .  
         [0028]     The imaging condition controller  28  controls the imaging angles of the cameras  11   a  and  12   a  based on the information about the imaging directions of the cameras  11   a  and  12   a  sent from the imaging angle setting unit  24 . The imaging condition controller  28  also controls the timing of imaging and the shutter speed of the camera  11   a  for the center area and the camera  12   a  for the right-and-left side area based on the determination result on the traveling condition of the vehicle determined by the traveling condition determination unit  27 .  
         [0029]     For example, the imaging condition controller  28  sets an interval B (in milliseconds) for image obtaining for the right-and-left side area imaging unit  12  such that it is longer than an interval A (in milliseconds) for image obtaining for the center area imaging unit  11 . The controller  28  also increases the interval B in accordance with an increase of the vehicle velocity (for example, as an interval B 1  is extended to an interval B 2  shown in  FIG. 2 ). Furthermore, the controller  28  sets the shutter speed of the right-and-left side imaging unit  12  such that it is faster than the shutter speed of the center area imaging unit  11 .  
         [0030]     The image combining unit  29  generates a combined-image by combining an image for the center area sent from the center area image obtaining unit  21  with an image for the right-and-left side area sent from the right-and-left side area image obtaining unit  22  based on the information about the imaging directions of the cameras  11   a  and  12   a  sent from the imaging angle setting unit  24  and the determination result on the traveling condition of the vehicle determined by the traveling condition determination unit  27 . The image combining unit  29  outputs the combined-image to a display controller  30 .  
         [0031]     For example, the image combining unit  29  determines an area of the image for the center area sent from the center area image obtaining unit  21 . The area of the image determined by the combining unit  29  constitutes a center portion MC in the horizontal direction of a combined-image M and is displayed in the center area of the display  16 . At the same time, the image combining unit  29  determines areas of the image for the right-and-left side area sent from the right-and-left side area image obtaining unit  22 . The areas of the image determined by the combining unit  29  constitutes a left portion ML and a right portion MR in the horizontal direction of the combined-image M and is displayed in the right-and-left side area of the display  16 . The combined-image M is thus generated.  
         [0032]     At this time, the image combining unit  29  determines the position and the shape of areas to be extracted from images for the center area C and images for the right-and-left side area in accordance with the information about the imaging directions of the cameras  11   a  and  12   a.    
         [0033]     In addition, when acceleration is detected by the traveling condition determination unit  27 , the field of view of the driver becomes narrower, therefore the image combining unit  29  reduces the width of the center area of the display  16  (that is, the width LC of the center portion MC of the combined-image M). At the same time, the image combining unit  29  increases the width of the right-and-left side area of the display  16  (that is, the width LL and LR of the left portion ML and the right portion MR of the combined-image M). The width LC is set to a predetermined minimum width (a width equivalent to the width of a lane of a road or slightly wider than that is displayed on the display).  
         [0034]     The display controller  30  drives the display  16  which in turn displays the combined-image sent from the image combining unit  29 .  
         [0035]     The display device  10  of the present embodiment has the aforementioned constitution and the operation thereof shall be described below.  
         [0036]     First, in step S 01  shown in  FIG. 4 , the imaging angle setting unit  24  obtains the information about the actual steering angle of the vehicle which is computed based on a signal from the steering angle sensor  13 , and the traveling condition determination unit  27  obtains information about the velocity of the vehicle which is computed based on a signal from the wheel speed sensor  14 .  
         [0037]     In step S 02 , the imaging angle setting unit  24  sets the imaging directions of the camera  11   a  for the center area and the camera  12   a  for the right-and-left side area in accordance with the actual steering angle of the vehicle.  
         [0038]     In step S 03 , the imaging condition controller  28  controls each shutter speed of the cameras  11   a  and  12   a  in accordance with the velocity of the vehicle.  
         [0039]     In step S 04 , the center area image obtaining unit  21  obtains images for the center area taken by the camera  11   a  and the right-and-left side area image obtaining unit  22  obtains images for the right-and-left side area taken by the camera  12   a.    
         [0040]     In step S 05 , the image combining unit  29  obtains an area of image to be the center portion MC of the combined-image M from images for the center area and areas of image to be the left portion ML and the right portion MR of the combined-image M from images for the right-and-left side area. At this time, the image combining unit  29  sets the width LC of the center portion MC, the width LL of the left portion ML, and the width LR of the right portion MR in accordance with the velocity of the vehicle, and determines the areas of the obtained images for the portions MC, ML, and MR in accordance with the actual steering angle of the vehicle.  
         [0041]     In step S 06 , the image combining unit  29  generates the combined-image M by combining the portions MC, ML, and MR.  
         [0042]     In step S 07 , the display controller  30  drives the display  16  which in turn displays the combined-image M and terminates the processing.  
         [0043]     Through the aforementioned steps, when the kinetic vision of the occupant declines and the field of view RV is narrowed in accordance with a change in the traveling condition of the vehicle (particularly acceleration), the display device displays images for the right-and-left side area in a portion of the display which corresponds to areas in the field of view where the occupant&#39;s ability to see relatively declines (that is, the right-and-left side area of the display  16 ). The obtaining interval and display period for the right-and-left side area images are set relatively longer than those for the images for the center area. The width of the right-and-left side area is set to be increased in accordance with acceleration for compensating for the occupant&#39;s declined ability to view properly.  
         [0044]     In addition, clearer still images are displayed in the right-and-left side area than in the center area because the images for the right-and-left side area are obtained with relatively faster shutter speed.  
         [0045]     On the other hand, in the field of view where the occupant&#39;s ability to see is maintained (that is, the center area of the display  16 ), images for the center area which are obtained under a relatively shorter obtaining interval are displayed. The display period of the images for the center area is set relatively shorter than that of the images for the right-and-left side area. Since the images for the center area are obtained with relatively slower shutter speed, continuity is emphasized among the consecutive images. As a result, images which look like a moving picture are displayed as if the occupant were actually watching.  
         [0046]     As described, the display device  10  of the present embodiment can properly assist the occupant&#39;s ability to view the surroundings, an ability which declines in accordance with the traveling condition of the vehicle when the kinetic vision of the occupant declines and the field of view is narrowed in accordance with a change in a traveling condition (e.g., acceleration) by displaying images obtained in a relatively longer interval and relatively faster shutter speed in areas of the display corresponding to areas in field of view where the occupant&#39;s ability to view relatively declines.  
         [0047]     Though this embodiment has the camera  11   a  for the center area and the camera  12   a  for the right-and-left side area, it is not limited thereto. For example, the display device may have only one camera. In this case, images for the center portion MC of the combined-image M and images for the left portion ML and the right portion MR are obtained under intervals different from each other and the combined-image M is generated by combining images for each portion. At this time, the obtaining interval for the portions ML and MR is set longer than that of the portion MC. In a case of low speed in  FIG. 2 , a relatively faster shutter speed is set when the timing of image obtaining for the portions ML and MR and the timing for the center portion MC are aligned, as indicated by points t 1 , t 4 , and t 7 , and a relatively slower shutter speed is set when only images for the center portion MC are obtained as indicated by points t 2 , t 3 , and t 5 .  
         [0048]     In addition, though the image taking directions of the cameras  11   a  and  12   a  are set in accordance with the actual steering angle computed by the steering angle computing unit  23 , it is not limited thereto. For example, the cameras  11   a  and  12   a  may be cameras of wider angle and images for the portion MC and images for the portions ML and MR may be selected from images taken by the cameras  11   a  and  12   a  in accordance with the actual steering angle computed by the steering angle computing unit  23 .  
         [0049]     While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.