Abstract:
A visually-distracted-driving detection device that can detect visually distracted driving with high accuracy. The visually-distracted-driving detection device includes a visually-distracted-driving determination unit that determines that a driver is visually distracted if the direction in which the driver is looking is greater than or equal to a predetermined angle with respect to the front of the driver; and a prohibition unit that, if it is specified that the present position of the vehicle as specified by a present-position specifying unit is within a first predetermined distance from an intersection, prohibits a process that is performed in cases where it is determined that the driver is visually distracted.

Description:
TECHNICAL FIELD  
       [0001]    The present invention relates to a visual distraction detecting apparatus (visually-distracted-driving detection device) for detecting whether an occupant (driver, etc.) of a vehicle is visually distracted. 
       BACKGROUND ART 
       [0002]    In relation to a visual distraction detecting apparatus, there has been proposed a technology that inhibits the visual distraction detecting apparatus from judging a visual distraction if a certain condition is satisfied. See, Japanese Laid-Open Patent Publication No. 2007-072629 (hereinafter referred to as “JP2007-072629A”). According to JP2007-072629A (see  FIG. 6 ), if a steering angle δ is not equal to or less than a predetermined steering angle δ 0  (step  100 : NO), if a turn signal switch  34  is not off (step  102 : NO), if a gear shift position is not a forward position (step  104 : NO), or if the road is not straight (step  106 : NO), then the output of a facial image camera  18  is invalidated and information concerning a facial angle θ is invalidated (step  110 ), thereby inhibiting the visual distraction detecting apparatus from judging the occurrence of a visual distraction. The proposed technology aims to perform various warning processes that are suitable in the case of a visual distraction (see paragraphs [0055] through [0066]). 
         [0003]    The process of judging whether the road is straight or not (step  106 ) is performed by judging a road lane, in which the vehicle is traveling at present or in which the vehicle is expected to travel several seconds later, as a straight road if the curvature of the traveled road lane, which is detected based on information supplied from a white line recognizing ECU  38 , is less than a predetermined curvature, or if the yaw angle of the vehicle is less than a predetermined angle (see paragraph [0058]). 
       SUMMARY OF INVENTION  
       [0004]    According to JP2007-072629A, as described above, it is judged whether a visual distraction should be inhibited from being judged or not. The judgment conditions for the judging process include the steering angle δ, the on/off state of the turn signal switch  34 , the gear shift position, and the straightness of the road (i.e., the curvature of the traveled road lane or the yaw angle). Therefore, the technology according to JP2007-072629A fails to deal with a crossroad intersection where straight roads run through one another continuously, for example. 
         [0005]    According to JP2007-072629A, for example, the visual distraction detecting apparatus is inhibited from judging a visual distraction (step  110 ) if a turn signal switch  34  is on (step  102 : NO). However, while the turn signal switch  34  is off, if the driver who intends to turn at an intersection is looking in a direction along which the vehicle will travel after turning at the intersection, the visual distraction detecting apparatus tends to judge that the driver is visually distracted. 
         [0006]    Similarly, according to JP2007-072629A, if the curvature of the traveled road lane, which is detected based on information supplied from the white line recognizing ECU  38 , is not less than a predetermined curvature (step  106 : NO), then the visual distraction driving detecting apparatus is inhibited from judging a visual distraction (step  110 ). However, in a case where the vehicle approaches a crossroad intersection where straight roads run through one another continuously, if a judgment is made only based on the curvature of the traveled road lane, then the vehicle is judged erroneously as traveling straightly even if the driver intends to make a turn at the intersection. 
         [0007]    The present invention has been made in view of the aforementioned problems. It is an object of the present invention to provide a visual distraction detecting apparatus, which is capable of detecting a visual distraction with high accuracy. 
         [0008]    A visual distraction detecting apparatus according to the present invention comprises a present position identifying unit for identifying a present position of a vehicle, the present position identifying unit including map data, a gazing direction detecting unit for detecting a gazing direction of an occupant of the vehicle based on a viewing direction or a facial direction of the occupant, a visual distraction judging unit for judging that the occupant is visually distracted if the gazing direction of the occupant is angularly spaced from a front direction of the occupant by a predetermined angle or greater, and an inhibiting unit for inhibiting a process, which would be performed if the occupant were judged as being visually distracted, when the present position identified by the present position identifying unit is located within a first predetermined distance from an intersection. 
         [0009]    According to the present invention, when the vehicle approaches an intersection, a process, such as a visual distraction warning process, for example, which would be performed if the occupant were judged as being visually distracted, is inhibited. Therefore, an action that the occupant takes to confirm the left or right of the vehicle is not judged erroneously as being a visual distraction. Consequently, the process, which should be performed only if the occupant is judged as being visually distracted, can be performed accurately. 
         [0010]    The visual distraction detecting apparatus may further comprise a route guiding unit for guiding the vehicle along a route set by the occupant, wherein the intersection is an intersection at which the route guiding unit guides the occupant to make a turn. In situations where it is highly likely that the occupant confirms the left or right of the vehicle, the process, which would be performed if the occupant were judged as being visually distracted, can be inhibited. Consequently, the process, which should be performed only if the occupant is judged as being visually distracted, can be performed accurately. 
         [0011]    The visual distraction detecting apparatus may further comprise an informing unit for informing the occupant of the intersection when the vehicle reaches a position within a second predetermined distance from the intersection at which the route guiding unit guides the occupant to make a turn, wherein the inhibiting unit inhibits the process, which would be performed if the occupant were judged as being visually distracted, after the informing unit has informed the occupant and until the present position identifying unit judges that the vehicle has completed a change in path. Therefore, the process which would be performed if the occupant were judged as being visually distracted, can be inhibited after informing of the intersection and only until the vehicle actually finishes turning through the intersection. Consequently, the process, which should be performed only if the occupant is judged as being visually distracted, can be performed accurately. 
         [0012]    The visual distraction detecting apparatus may further comprise a steering angle detecting unit for detecting a steering angle of a steering wheel of the vehicle, wherein the inhibiting unit inhibits the process, which would be performed if the occupant were judged as being visually distracted, until the steering angle detecting unit detects that the steering angle has changed from a value that is greater than a predetermined steering angle threshold value to a value that is less than the predetermined steering angle threshold value. Therefore, a visual distraction warning can be inhibited from being issued only until the vehicle actually finishes turning. Consequently, the process, which should be performed only if the occupant is judged as being visually distracted, can be performed accurately. 
         [0013]    The visual distraction detecting apparatus may further comprise a resetting unit for automatically resetting a route when the vehicle has traveled along a route that differs from the route along which the route guiding unit has guided the vehicle, wherein the inhibiting unit may inhibit the process, which would be performed if the occupant were judged as being visually distracted, until the resetting unit automatically resets a route. Even if the vehicle deviates from the route along which the route guiding unit has guided the vehicle, the process, which would be performed if the occupant were judged as being visually distracted, can be prevented from being performed while the route is being reset. 
         [0014]    The first predetermined distance may be shorter than, longer than, or equal to the second predetermined distance. If the first predetermined distance is shorter than the second predetermined distance, then even if the occupant confirms the left or right of the vehicle in response to being prompted by information from the informing unit, the action to confirm the left or right of the vehicle can be prevented from being judged erroneously as a visual distraction. Therefore, the process, which should be performed only if the occupant is judged as being visually distracted, can be performed accurately. 
         [0015]    According to the present invention, there also is provided a visual distraction detecting apparatus comprising a gazing direction detector for detecting a gazing direction of a driver of a vehicle based on at least one of a viewing direction and a facial direction of the driver, a visual distraction judging section for judging whether the driver is visually distracted, using an angle formed between the gazing direction and a front direction of the driver, or a direction along which the vehicle is traveling, and an intersection approach judging section for detecting whether the vehicle is approaching an intersection. If the vehicle is approaching the intersection, the visual distraction judging section does not judge that the driver is visually distracted, or alternatively, a process, which would be performed if the driver were judged as being visually distracted, is not performed even if the visual distraction judging section judges that the driver is visually distracted. 
         [0016]    According to the present invention, if the vehicle is approaching an intersection, the process, which would be performed if the occupant were judged as being visually distracted, is not performed. If the visual distraction detecting apparatus according to the present invention is incorporated in a configuration in which a warning is issued upon detection of a visual distraction, an action that the occupant of the vehicle takes to confirm the left or right side of the vehicle at an intersection, or to gaze at a pedestrian or the like, is not judged erroneously as being a visual distraction. Hence, an inappropriate warning is avoided. Further, if a certain numerical value, e.g., a TTC (Time To Contact) threshold value for judging whether a warning should be issued or not, is changed upon detection of a visual distraction, then such a numerical value can be set appropriately. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  is an overall block diagram of a vehicle, which incorporates therein a visual distraction warning apparatus as a visual distraction detecting apparatus according to an embodiment of the present invention; 
           [0018]      FIG. 2  is a view showing a peripheral area around a front windshield of the vehicle; 
           [0019]      FIG. 3  is a view showing a situation in which the visual distraction warning apparatus is applied; 
           [0020]      FIG. 4  is a first flowchart of a visual distraction detecting process carried out by the visual distraction warning apparatus; 
           [0021]      FIG. 5  is a second flowchart of a visual distraction detecting process carried out by the visual distraction warning apparatus; 
           [0022]      FIG. 6  is a plan view for describing the judgment of a visual distraction; 
           [0023]      FIG. 7  is a flowchart of a visual distraction warning inhibition judging process; and 
           [0024]      FIG. 8  is a flowchart of a modification of the visual distraction warning inhibition judging process shown in  FIG. 7 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     1. Description of Overall Arrangement 
     [1-1. Overall Arrangement] 
       [0025]      FIG. 1  is an overall block diagram of a vehicle  10  that incorporates therein a visual distraction warning apparatus  12  (hereinafter also referred to as a “warning apparatus  12 ”) as a visual distraction detecting apparatus according to an embodiment of the present invention.  FIG. 2  is a view showing a peripheral area around a front windshield  14  of the vehicle  10 . As shown in  FIGS. 1 and 2 , the warning apparatus  12  includes an occupant camera  16 , a navigation device  18 , a steering angle sensor  20 , an electronic control unit  22  (hereinafter referred to as an “ECU  22 ”), a speaker  24 , and a headup display  26  (hereinafter referred to as a “HUD  26 ”). As shown in  FIG. 2 , the vehicle  10  according to the present embodiment is a so-called right-hand drive vehicle. Alternatively, the vehicle  10  may be a left-hand drive vehicle having the same arrangement as described above. 
       [1-2. Occupant Camera  16 ] 
       [0026]    As shown in  FIG. 2 , the occupant camera  16  (image capturing unit) is mounted on a steering column, not shown, directly in front of the driver seat of the vehicle  10 . The occupant camera  16  captures an image of the face (head) of the driver (hereinafter referred to as a “facial image”). The occupant camera  16  is not limited in position to the illustrated position, but may be positioned near a rearview mirror  28  ( FIG. 2 ) or on a dashboard  30 . The occupant camera  16  is not limited to a camera for capturing an image in one direction, but may be a camera for capturing images in multiple directions (a so-called stereo camera). The occupant camera  16  may be a color camera, a monochromatic camera, or a near-infrared camera. 
       [1-3. Navigation Device  18 ] 
       [0027]    The navigation device  18  uses a GPS (Global Positioning System) to detect the present position of the vehicle  10 , and guides the user (occupant) through a route to the destination. As shown in  FIG. 1 , the navigation device  18  includes a communication unit  40 , an input/output unit  42 , a processor  44 , a storage unit  46 , and a display unit  48 . 
         [0028]    The communication unit  40  acquires positional information from a GPS satellite, and performs wireless communications with an external server, not shown. The input/output unit  42  is used to communicate with the ECU  22  and the speaker  24 . 
         [0029]    The processor  44  performs various processing routines for controlling operations of various parts of the navigation device  18  as well as performing route guidance. As shown in  FIG. 1 , the processor  44  includes a present position identifying function  50 , a route guiding function  52 , and a route resetting function  54 . The present position identifying function  50  (present position identifying unit) identifies the present position of the vehicle  10  based on positional information from the GPS satellite and map information that is stored in the storage unit  46 . 
         [0030]    The route guiding function  52  (route guiding unit, informing unit) sets a route for guiding the user (hereinafter referred to as a “guidance route”) based on the destination given by the occupant and the present position of the vehicle  10 , and guides the user through the guidance route. Alternatively, a guidance route may be set by an external server. More specifically, the route guiding function  52  may send the destination and the present position to an external server through the communication unit  40 , and the navigation device  18  (route guiding function  52 ) may receive and use a guidance route, which is set by the external server based on the destination and the present position. The route resetting function  54  (resetting unit) resets the guidance route if the path followed by the vehicle  10  deviates from the route that the navigation device  18  uses for guiding the vehicle  10 . 
         [0031]    The storage unit  46  serves to store various programs and data, and has a map database  56  (hereinafter referred to as “map information DB  56 ”). The map information DB  56 , which stores map information, is used by the processor  44  when the processor  44  performs route guidance. The data stored in the map information DB  56  includes information I 1  concerning the path followed by the vehicle  10 . The information I 1  is made up of information concerning intersections and curves (positions of intersections, positions of entrances and exits of curves, curvatures of curves, etc.). 
         [0032]    The display unit  48 , which includes a touch panel or the like, serves to input information to and output information from the navigation device  18 . For example, a destination is entered into the navigation device  18 , and a route to the destination is extracted from the navigation device  18 . 
         [0033]    In  FIG. 2 , the navigation device  18  is installed in the vehicle  10 . However, a portable information terminal such as a smartphone or the like may be used as the navigation device  18 . If a portable information terminal is used as the navigation device  18 , then the map information DB  56  may be installed in the external server, and the portable information terminal may request the external server to calculate a guidance route. The portable information terminal may receive the guidance route, which was calculated in response to the request, from the external server, and may supply the information I 1 , etc., to the ECU  22  through a wired or wireless link. 
       [1-4. Steering Angle Sensor  20 ] 
       [0034]    The steering angle sensor  20  (steering angle detecting unit) detects a steering angle θs of a steering wheel  32  of the vehicle  10 , and supplies the detected steering angle θs to the ECU  22 . 
       [1-5. ECU  22 ] 
       [0035]    As shown in  FIG. 1 , the ECU  22 , which serves to control the visual distraction warning apparatus  12 , includes an input/output unit  60 , a processor  62 , and a storage unit  64 . The input/output unit  60  is used to communicate with the occupant camera  16 , the navigation device  18 , the steering angle sensor  20 , the speaker  24 , and the HUD  26 . 
         [0036]    As shown in  FIG. 1 , the processor  62  includes a gazing direction detecting function  70 , a visual distraction judging function  72 , a visual distraction warning function  74 , and a warning inhibiting function  76 . The gazing direction detecting function  70  (gazing direction detecting unit, gazing direction detector) detects a gazing direction of the driver based on at least one of the viewing direction (eyeball direction) and the facial direction of the driver (occupant). 
         [0037]    The visual distraction judging function  72  (visual distraction judging unit, visual distraction judging section) judges whether or not the driver is visually distracted based on the gazing direction of the driver. If the visual distraction judging function  72  judges that the driver is visually distracted, then the visual distraction warning function  74  issues a warning against the visual distraction (hereinafter referred to as a “visual distraction warning”). According to the present embodiment, the visual distraction warning is issued both as a warning sound from the speaker  24  and displayed as a warning indication on the HUD  26 . However, the visual distraction warning may be either one of a warning sound and a warning indication, or may be another type of warning, e.g., a warning given by turning on or blinking a predetermined indicator. Even if the visual distraction judging function  72  judges that the driver is visually distracted, the warning inhibiting function  76  (inhibiting unit, intersection approach judging section) inhibits the visual distraction warning function  74  from issuing a visual distraction warning if a predetermined condition is satisfied, as will be described in detail later. 
       [1-6. Speaker  24 ] 
       [0038]    The speaker  24  is used to produce a speech output for delivering audible route guidance performed by the navigation device  18 , and also to produce a warning sound, which is output as a visual distraction warning issued by the ECU  22  (visual distraction warning function  74 ). The speaker  24  may also be used for other purposes, such as producing sound outputs from radio broadcasts, television broadcasts, and audio devices. 
       [1-7. HUD  26 ] 
       [0039]    The HUD  26  includes a display device mounted on the front windshield  14  of the vehicle  10 , which displays the vehicle speed, mileage, guidance information for route guidance performed by the navigation device  18  (arrows for route guidance), and a warning image that provides a visual distraction warning issued by the ECU  22  (visual distraction warning function  74 ). The HUD  26  may also display other information, such as information that indicates the presence of pedestrians at night. 
       2. Overview of Control Process According to the Present Embodiment 
       [0040]      FIG. 3  is a view showing a situation in which the visual distraction warning apparatus  12  is applied.  FIG. 3  shows by way of example a view, as seen from within the vehicle  10 , of an area in front of the vehicle  10 , along with a display screen  80  that is displayed on the display unit  48  of the navigation device  18 . The display screen  80  includes an icon  82  representing the vehicle  10 , and a straight line (guidance route line  84 ) on a road, which is representative of a guidance route set by the navigation device  18 . 
         [0041]    If there is an intersection  86  at which the vehicle  10  is expected to turn to the left or the right on the guidance route (guidance route line  84 ) set by the navigation device  18 , then it is assumed that the driver  88  will gaze at a direction in which the vehicle  10  will travel in the future (i.e., a left forward direction in  FIG. 3 ). Stated otherwise, although the gazing direction X of the driver  88  is different from the front direction of the driver  88  or the vehicle  10 , i.e., the direction in which the vehicle  10  is traveling at present, the driver  88  is behaving normally, i.e., as required in order to drive the vehicle  10 , and is not visually distracted. In this case, according to the present embodiment, a visual distraction warning is inhibited from being issued, and hence an inappropriate visual distraction warning can be avoided. 
       3. Details of Control Process According to the Present Embodiment 
     [3-1. Overall Sequence] 
       [0042]      FIGS. 4 and 5  are first and second flowcharts of a visual distraction detecting process, which is carried out by the visual distraction warning apparatus  12 . In step S 1 , the ECU  22  acquires various items of information from the navigation device  18  (hereinafter referred to as “navigational information”). The navigational information includes the present position of the vehicle  10 , in addition to the information I 1  referred to above (information concerning intersections and curves). 
         [0043]    In step S 2 , the occupant camera  16  acquires a facial image of the driver  88 . In step S 3 , based on the facial image of the driver  88  that was acquired by the occupant camera  16 , the ECU  22  detects a gazing direction X of the driver  88 . 
         [0044]    A viewing direction of the driver  88  can be detected by the method described in Japanese Laid-Open Patent Publication No. 2010-105417 (see paragraphs [0014] through [0016], for example). 
         [0045]    The facial direction of the driver  88  can be detected in the following manner, for example. Based on the facial image captured by the occupant camera  16 , the ECU  22  (gazing direction detecting function  70 ) detects the central position of the face along with left and right end positions of the face. Based on the detected positions, the ECU  22  approximates the face of the driver  88  to be a cylindrical shape, for example, and calculates the facial direction (cylinder process). 
         [0046]    In step S 4 , using the gazing direction X (to be described in detail later), the ECU  22  (visual distraction judging function  72 ) judges whether or not the driver  88  is visually distracted. If the driver  88  is judged not to be visually distracted (step S 5 : NO) as a result of the visual distraction judging process performed in step S 4 , the ECU  22  (warning inhibiting function  76 ) inhibits a visual distraction warning from being issued, i.e., the ECU  22  does not perform the visual distraction warning function  74  in step S 6 . 
         [0047]    In step S 7 , the ECU  22  resets a visual distraction time T 1  to zero. The visual distraction time T 1  represents an accumulated value of times during which the driver  88  has been judged as being visually distracted. 
         [0048]    In step S 8 , the ECU  22  judges whether or not the vehicle  10  has deviated from the guidance route. If the vehicle  10  has not deviated from the guidance route (step S 8 : NO), then in step S 9 , using the navigational information referred to above, the ECU  22  judges whether or not the vehicle  10  is traveling in the intersection  86  or along a curve. If the vehicle  10  is traveling in the intersection  86  or along a curve (step S 9 : YES), then control returns to step S 7 . If the vehicle  10  is not traveling in the intersection  86  or along a curve (step S 9 : NO), then in step S 10 , the ECU  22  cancels inhibition of the visual distraction warning. 
         [0049]    Inhibition of the visual distraction warning in step S 6  may not be carried out as a specific process, and may be continued by repeating steps S 7  through S 9 . If inhibition of the visual distraction warning is not carried out as a specific process, then cancelation of the inhibition of the visual distraction warning, which typically is performed in step S 10 , may not be carried out as a specific process. 
         [0050]    Returning to step S 8 , if the vehicle  10  has deviated from the guidance route (step S 8 : YES), then in step S 11 , the ECU  22  judges whether or not resetting of a guidance route by the navigation device  18  has been completed. The guidance route is automatically reset by the route resetting function  54  of the navigation device  18 . If resetting of the guidance route by the navigation device  18  has not been completed (step S 11 : NO), then the ECU  22  repeats step S 11  until the resetting operation is completed. If resetting of a guidance route by the navigation device  18  has been completed (step S 11 : YES), then control proceeds to step S 10 . 
         [0051]    Returning to step S 5 , if the driver  88  is visually distracted (step S 5 : YES), then in step S 12  of  FIG. 5 , the ECU  22  judges whether or not the navigation device  18  is performing route guidance. If the navigation device  18  is not performing route guidance (step S 12 : NO), then control proceeds to step S 15 . If the navigation device  18  is performing route guidance (step S 12 : YES), then in step S 13 , the ECU  22  performs a visual distraction warning inhibition judging process. As will be described later with reference to  FIG. 7 , the visual distraction warning inhibition judging process is a process for judging whether or not a visual distraction warning should be inhibited, even if the visual distraction judging function  72  has judged that the driver  88  is visually distracted. 
         [0052]    If a visual distraction warning is to be inhibited (step S 14 : YES) as a result of the visual distraction warning inhibition judging process performed in step S 13 , then control proceeds to step S 6  in  FIG. 4 . If a visual distraction warning is not to be inhibited (step S 14 : NO), then, in step S 15 , the ECU  22  judges whether or not the visual distraction time T 1  is equal to or greater than a threshold value THt 1 . The threshold value THt 1  represents a time (e.g., a time ranging from 1 second to 4 seconds) required to finalize the judgment that the driver  88  is visually distracted. If the visual distraction time T 1  is equal to or greater than the threshold value THt 1 , then the judgment that the driver  88  is visually distracted is finalized. 
         [0053]    If the visual distraction time T 1  is not equal to or greater than the threshold value THt 1  (step S 15 : NO), then the present processing cycle is brought to an end, and control returns to step S 1 . If the visual distraction time T 1  is equal to or greater than the threshold value THt 1  (S 15 : YES), then in step S 16 , the ECU  22  (visual distraction warning function  74 ) issues a visual distraction warning. As described above, the visual distraction warning is issued both as a warning sound from the speaker  24  and as a warning indication displayed on the HUD  26 . After step S 16 , control returns to step S 1 . 
       [3-2. Visual Distraction Judging Process] 
       [0054]      FIG. 6  is a plan view illustrating judgment of a visual distraction. In  FIG. 6 , reference numeral “ 100 ” denotes a line (hereinafter referred to as a “central line  100 ”) indicating the front direction of the driver  88  or the front direction of the vehicle  10  in the position of the driver  88 , and “θ” indicates an angle (hereinafter referred to as a “gazing angle θ”) of the gazing direction X of the driver  88  from the central line  100 . For ease of illustration, it is assumed that the gazing angle θ on the left side (counterclockwise) of the central line  100  (zero) is of a positive value, whereas the gazing angle θ on the right side (clockwise) of the central line  100  is of a negative value. The character “α” denotes a range (hereinafter referred to as a “non-visual-distraction angular area α” or a “non-visual-distraction area α”), which is judged by the ECU  22  (visual distraction judging function  72 ) as being a range in which the driver  88  is not visually distracted. 
         [0055]    Reference numeral “ 102 ” denotes a line indicating the left end of the non-visual-distraction area a, whereas reference numeral “ 104 ” denotes a line indicating the right end of the non-visual-distraction area a. These lines will hereinafter be referred to as “non-visual-distraction area boundary lines  102 ,  104 ” or simply “boundary lines  102 ,  104 ”. The boundary line  102  represents a predetermined value (hereinafter referred to as a “threshold value THθ 1 ”) with respect to the central line  100 . If the gazing angle θ exceeds the threshold value THθ 1  (θ&gt;THθ 1 ), then the ECU  22  (visual distraction judging function  72 ) judges that a visual distraction is taking place in the leftward direction (counterclockwise). Similarly, the boundary line  104  represents a predetermined value (hereinafter referred to as a “threshold value THθ 2 ”) with respect to the central line  100 . If the gazing angle θ runs past the threshold value THθ 2  (θ&lt;THθ 2 ), then the ECU  22  (visual distraction judging function  72 ) judges that a visual distraction is taking place in the rightward direction (counterclockwise). If the gazing angle θ does not exceed either of the boundary lines  102 ,  104  (THθ 2 ≦θ≦THθ 1 ), then the ECU  22  (visual distraction judging function  72 ) judges that a visual distraction is not taking place. 
       [3-3. Visual Distraction Warning Inhibition Judging Process] 
       [0056]      FIG. 7  is a flowchart of the visual distraction warning inhibition judging process. In step S 21 , based on the navigational information referred to above, the ECU  22  judges the distance D from the vehicle  10  to the intersection  86  ( FIG. 3 ) or a curve, for example. The intersection  86  refers to an intersection where the vehicle  10  is expected to turn to the left or the right on the guidance route. Alternatively, the intersection  86  may be an intersection at which the vehicle  10  is expected to travel straight through the intersection. 
         [0057]    In step S 22 , the ECU  22  judges whether the vehicle  10  has approached the intersection  86  or a curve within a certain distance (hereinafter referred to as a “guidance execution distance Dnavi” or simply a “distance Dnavi”) at which the navigation device  18  executes speech guidance concerning the intersection  86  or a curve. Specifically, the ECU  22  judges whether or not the distance D is equal to or less than the distance Dnavi. Alternatively, instead of or in addition to the speech guidance from the speaker  24 , the ECU  22  may display on the HUD  26  a guidance indicator such as an arrow or the like pointing toward the direction in which the vehicle  10  is to turn. 
         [0058]    If the vehicle  10  has not approached the intersection  86  or a curve within the distance Dnavi (step S 22 : NO), then in step S 23 , the ECU  22  judges whether or not the vehicle  10  has approached the intersection  86 . More specifically, a threshold value (hereinafter referred to as an “intersection approaching judgment threshold value Di” or simply a “threshold value Di”) for judging whether or not the vehicle  10  has approached the intersection  86  is preset, and the ECU  22  judges whether or not the distance D is equal to or less than the threshold value Di. The threshold value Di is set as a distance at which the driver  88  is likely to confirm the situation to the left or the right of the vehicle  10  in order to execute a left or a right turn, or is set as a distance greater than the above-mentioned distance, for example. Typically, the threshold value Di is set shorter than the distance Dnavi. If necessary, however, the threshold value Di may be set longer than or equal to the distance Dnavi. 
         [0059]    If the vehicle  10  has not approached the intersection  86  (step S 23 : NO), then, in step S 24 , the ECU  22  judges whether or not the vehicle  10  has approached a curve having a predetermined radius of curvature or less. More specifically, a threshold value (hereinafter referred to as a “radius-of-curvature threshold value Re or simply a “threshold value Rc”) indicative of the predetermined radius of curvature, and a threshold value (hereinafter referred to as a “curve approaching judgment threshold value Dc” or simply a “threshold value Dc”) for judging whether or not the vehicle  10  has approached the curve are preset, and the ECU  22  judges whether or not the radius R of curvature of the present curve in question is equal to or less than the threshold value Rc, and whether or not the distance D is equal to or less than the threshold value Dc. The threshold value Dc is set as a distance at which the driver  88  should confirm the direction in which the curve proceeds in order to turn safely along the curve, i.e., a direction that may potentially exceed the threshold value THθ 1  or the threshold value THθ 2  from the front direction, or as a distance greater than the above-mentioned distance. Usually, the threshold value Dc is set shorter than the distance Dnavi. If necessary, however, the threshold value Dc may be set to be longer than or equal to the distance Dnavi. 
         [0060]    If the vehicle  10  has not approached a curve having a predetermined radius of curvature (step S 24 : NO), i.e., if the radius R of curvature is not equal to or less than the threshold value Rc, or if the distance D is not equal to or less than the threshold value Dc, then the present processing sequence is brought to an end. 
         [0061]    If the vehicle  10  has approached the intersection  86  or a curve within the distance Dnavi (step S 22 : YES), if the vehicle  10  has approached the intersection  86  (step S 23 : YES), or if the vehicle  10  has approached a curve having a predetermined radius of curvature (step S 24 : YES), then control proceeds to step S 25 . 
         [0062]    In step S 25 , the ECU  22  (warning inhibiting function  76 ) inhibits a visual distraction warning from being issued. Consequently, a visual distraction warning is not issued, even if the visual distraction judging function  72  judges that the driver  88  is visually distracted. 
       4. Advantages of the Present Embodiment 
       [0063]    According to the present embodiment, as described above, when the vehicle  10  approaches the intersection  86  or a curve within the predetermined distance (step S 22 : YES, step S 23 : YES, or step S 24 : YES), a visual distraction warning is inhibited. Therefore, an action, which the driver  88  takes to confirm the left or right of the vehicle  10  at the intersection  86  or the direction in which the curve proceeds, is not judged erroneously as being a visual distraction. Therefore, a visual distraction warning process can be performed accurately. 
         [0064]    According to the present embodiment, the intersection  86  refers to an intersection at which the navigation device  18  guides the driver  88  to make a turn. The visual distraction warning process is inhibited in situations in which it is highly likely for the driver  88  to confirm the left or right of the vehicle  10 . Consequently, the visual distraction warning process can be performed accurately. 
         [0065]    According to the present embodiment, after the answer to any one of steps S 22  through S 24  is “YES” and until the answer to any one of steps S 22  through S 24  is “NO”, the ECU  22  (warning inhibiting function  76 ) inhibits the process, i.e., the visual distraction warning process, which otherwise would be performed if the driver  88  were judged as being visually distracted, or the ECU  22  (warning inhibiting function  76 ) continues to carry out step S 25 . Since a visual distraction warning is inhibited from being issued only until the vehicle  10  actually finishes execution of the turn along the curve, the visual distraction warning process can be performed more accurately. 
         [0066]    After the vehicle  10  has deviated from the guidance route (step S 8  in  FIG. 4 ) and until a new guidance route is set (step S 11 : YES), the visual distraction warning is inhibited from being issued, i.e., step S 16  is not carried out. Therefore, even if the vehicle  10  deviates from the guidance route, a visual distraction warning is prevented from being issued erroneously while the guidance route is being reset. 
         [0067]    According to the present embodiment, the intersection approaching judgment threshold value Di and the curve approaching judgment threshold value Dc are less than the guidance execution distance Dnavi. Therefore, even at times that the driver  88  confirms the left or right of the vehicle  10  or the direction in which the curve proceeds, as prompted by speech guidance or guidance displayed on the HUD  26  concerning the intersection  86  or the curve, an action to confirm the left or right of the vehicle  10  or the direction in which the curve proceeds is prevented from being judged erroneously as being a visual distraction. Therefore, the visual distraction warning process can be performed accurately. 
         [0068]    According to the present embodiment, when the vehicle  10  approaches the intersection  86  within a predetermined distance (step S 22 : YES or step S 23 : YES), a visual distraction is not judged as occurring, i.e., step S 25  is continuously carried out. Therefore, an action, which the driver  88  takes to confirm the left or right of the vehicle  10  at the intersection  86  or to gaze at a pedestrian or the like, is not judged erroneously as being a visual distraction, and hence, issuance of an inappropriate warning is avoided. If a certain numerical value, e.g., a TTC threshold value for judging whether or not a warning should be issued, is to be changed when a visual distraction is detected, then such a numerical value can be set appropriately. 
       5. Modifications 
       [0069]    The present invention is not limited to the above embodiment, but various arrangements may be adopted based on the disclosure of the present description. For example, the present invention may adopt the following arrangements. 
       [5-1. Objects Capable of Incorporating the Visual Distraction Detecting Apparatus] 
       [0070]    In the above embodiment, the warning apparatus  12  is incorporated in a vehicle  10 . However, the warning apparatus  12  may be incorporated in other types of objects. For example, the warning apparatus  12  may be incorporated in mobile objects such as ships, aircrafts, etc. The warning apparatus  12  is not limited to being incorporated in mobile bodies, but may be incorporated in other apparatus that have a need to detect when occupants thereof are visually distracted. 
       [5-2. Visual Distraction Judging Process] 
       [0071]    According to the present invention, a visual distraction is judged to have occurred by the process described with reference to  FIG. 6 . However, a visual distraction may be judged to have occurred by other processes, insofar as such processes are capable of judging whether or not an operator such as a driver  88  or the like is visually distracted. 
       [5-3. Warning Inhibiting Process] 
       [0072]    The warning apparatus  12  according to the above embodiment inhibits a visual distraction warning, i.e., a warning for indicating the occurrence of a visual distraction to the driver  88 , from being issued when the vehicle  10  approaches the intersection  86  or a curve within a predetermined distance (any one of steps S 22  through S 24 : YES). However, another process, which normally would be performed when a visual distraction is detected, may be inhibited from being carried out when the vehicle  10  approaches the intersection  86  or a curve within a predetermined distance (any one of steps S 22  through S 24 : YES). For example, as disclosed in JP2007-072629A, in which a warning is issued if a TTC (Time to Contact) is equal to or less than a predetermined value, a TTC threshold value may be changed upon the occurrence of a visual distraction, i.e., a TTC threshold value may not be increased even if a visual distraction is judged to have occurred. Furthermore, rather than inhibiting a warning from being issued, a camera output may be invalidated, as disclosed in JP2007-072629A. Alternatively, in an arrangement in which the acceleration or the vehicle speed of the vehicle  10  is limited when a visual distraction is detected, the acceleration or the vehicle speed may be inhibited from being limited. Further, in an arrangement in which the vehicle  10  is automatically decelerated when a visual distraction is detected, the vehicle  10  may be inhibited from being automatically decelerated. 
         [0073]    In the above embodiment, the visual distraction warning inhibition judging process is carried out according to the flowchart shown in  FIG. 7 . However, the visual distraction warning inhibition judging process is not limited to the features of the flowchart shown in  FIG. 7 . The visual distraction warning inhibition judging process may be carried out according to another flowchart, insofar as a visual distraction warning, i.e., a warning for indicating the occurrence of a visual distraction to the driver  88 , can be inhibited from being issued based on the fact that the vehicle  10  approaches the intersection  86  or a curve within a predetermined distance. 
         [0074]      FIG. 8  is a flowchart of a modification of the visual distraction warning inhibition judging process. In step S 31 , the ECU  22  judges the distance D from the vehicle  10  to the intersection  86  or a curve. This judging process is the same as that performed in step S 21  of  FIG. 7 . 
         [0075]    In step S 32 , the ECU  22  judges whether or not the vehicle  10  approaches the intersection  86  and whether or not a blinker (not shown) is turned on. More specifically, a threshold value (hereinafter referred to as an “intersection approaching judgment threshold value Di 1 ” or simply a “threshold value Di 1 ”) for judging whether or not the vehicle  10  has approached the intersection  86  is preset, and the ECU  22  judges whether or not the distance D is equal to or less than the threshold value Di 1 . The threshold value Di 1  may be set as a distance at which the blinker is expected to be turned on or a value in the vicinity thereof, for example. After the blinker has been turned on by a switch that is operated by the driver  88 , the blinker continues operating after the steering angle θs detected by the steering angle sensor  20  has exceeded a first steering angle threshold value and until the steering angle θs becomes less than a second steering angle threshold value. The second steering angle threshold value may be set equal to or less than the first steering angle threshold value. 
         [0076]    If the vehicle  10  has not approached the intersection  86  and the blinker has not been operated (step S 32 : NO), then in step S 33 , the ECU  22  judges whether or not the vehicle  10  has further approached, i.e., has approached more closely to, the intersection  86 . More specifically, a threshold value (hereinafter referred to as an “intersection approaching judgment threshold value Di 2 ” or simply a “threshold value Di 2 ”) for judging whether or not the vehicle  10  has further approached the intersection  86  is preset, and the ECU  22  judges whether or not the distance D is equal to or less than the threshold value Di 2 . The threshold value Di 2  is set less than the threshold value Di 1  (Di 2 &lt;Di 1 ). 
         [0077]    If the vehicle  10  has not approached closer to the intersection  86  (step S 33 : NO), then in step S 34 , the ECU  22  judges whether or not the vehicle  10  has approached a curve having a predetermined radius of curvature or less. The judging process of step S 34  is the same as the judging process of step S 24  of  FIG. 7 . 
         [0078]    If the vehicle  10  has approached the intersection  86  and the blinker has been operated (step S 32 : YES), or if the vehicle  10  has further approached the intersection  86  (step S 33 : YES), or if the vehicle  10  has approached a curve having a predetermined radius of curvature or less (step S 34 : YES), then control proceeds to step S 35 . 
         [0079]    In step S 35 , the ECU  22  (warning inhibiting function  76 ) inhibits a visual distraction warning from being issued. Therefore, a visual distraction warning process is not carried out, even if the ECU  22  (visual distraction judging function  72 ) has judged that the driver  88  is visually distracted. 
         [0080]    According to the present modification, since a visual distraction warning is inhibited from being issued until the blinker is turned on, i.e., until the vehicle  10  finishes turning through the intersection  86 , the visual distraction warning process can be performed more accurately. 
         [0081]    In the above embodiment, using navigational information from the navigation device  18 , the ECU  22  detects that the vehicle  10  has approached the intersection  86  or a curve within a predetermined distance. However, the ECU  22  is not limited to using navigational information from the navigation device  18 . Other information may be used, insofar as such information enables the ECU  22  to detect that the vehicle  10  has approached the intersection  86  or a curve within a predetermined distance. For example, the ECU  22  may detect that the vehicle  10  has approached the intersection  86  or a curve based on communications between the warning apparatus  12  and communication units, e.g., optical beacons, laid on the roadside. Alternatively, using an image from an image capturing device, e.g., an infrared camera, which captures images around the periphery of the vehicle  10 , the ECU  22  may judge the distance D up to an intersection or a curve, a traffic signal, or a mark that indicates an intersection or a curve.