Abstract:
A blind spot detection system. The system includes a camera mounted at the rear of a vehicle, a controller coupled to the camera, and an indicator coupled to the controller. The camera is configured to capture images in a field-of-view to the rear of the vehicle. The controller is configured to receive a signal from the camera indicative of the images, and controller determineg when a second vehicle in the images enters a blind spot of the vehicle. The controller activates the indicator when the second vehicle enters the blind spot of the vehicle.

Description:
BACKGROUND 
       [0001]    The invention relates to blind spot detection systems for vehicles. More specifically, the invention relates to a blind spot detection system that uses a rear view camera to detect when another vehicle has entered the vehicle&#39;s blind spot. 
         [0002]    Most blind spot detection systems use dedicated sensors to determine when an object is in a vehicle&#39;s blind spot (i.e., an area where a driver of the vehicle cannot see the object with the vehicle&#39;s mirrors). For example, dedicated ultrasonic, radar, and similar sensors are fitted on or in vehicles and used for blind spot detection purposes, detect vehicles in the blind spot and alert the driver of the presence of those vehicles. 
       SUMMARY 
       [0003]    The invention performs blind spot detection with sensors that are used for other vehicle functions (e.g., ultrasonic sensors from a parking assist system, a rear-view camera for a backing assist system, etc.). 
         [0004]    In one embodiment, the invention provides a blind spot detection system. The system includes a camera mounted at the rear of a vehicle, a controller coupled to the camera, and an indicator coupled to the controller. The camera is configured to capture images in a field-of-view to the rear of the vehicle. The controller is configured to receive a signal from the camera indicative of the images, and controller determineg when a second vehicle in the images enters a blind spot of the vehicle. The controller activates the indicator when the second vehicle enters the blind spot of the vehicle. 
         [0005]    In another embodiment the invention provides a method of detecting a vehicle in a blind spot of a host vehicle. The method includes providing a plurality of images from a camera to a controller of a field-of-view (FOV) behind the vehicle, detecting, by the controller, a second vehicle in the plurality of images, tracking, by the controller, the second vehicle, determining that the second vehicle has entered one of the vehicle&#39;s blind spots, and issuing, by the controller, an indication of the second vehicle&#39;s position to an operator of the vehicle. 
         [0006]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a diagram of a vehicle showing fields-of-view for a plurality of sensors. 
           [0008]      FIG. 2A  shows a side view mirror. 
           [0009]      FIG. 2B  shows the side view mirror of  FIG. 2A  with a blind spot indicator icon lit. 
           [0010]      FIG. 3  is a plan view of a dashboard of a vehicle. 
           [0011]      FIG. 4  shows positions of vehicles detected by a blind spot detection system. 
           [0012]      FIG. 5  illustrates exemplary zones of danger for a blind spot detection system. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
         [0014]      FIG. 1  shows a vehicle  100  equipped with a blind spot detection system  102 . The vehicle  100  includes an engine  105 , a controller  110 , a rear-view camera  115  (e.g., a CCD camera), a plurality of wheel speed sensors  125 , a right side-view mirror  130 , a left side-view mirror  135 , and a human-machine interface (HMI)  140 . The controller  110  can be a stand-alone controller (i.e., performing driver information functions) or can incorporate other control functions (e.g., engine control, braking control, etc.) in addition to driver information functions. The blind spot detection system  102  includes the controller  110 , the rear-view camera  115 , and the HMI  140 . In some embodiments, as described below, the blind spot detection system  102  includes additional components (e.g., additional sensors, additional HMI devices). 
         [0015]    The controller  110  includes a processor  145  (e.g., a microprocessor, microcontroller, ASIC, DSP, FPGA, etc.) and memory  150  (e.g., flash, ROM, RAM, EEPROM, etc.), which can be internal to the processor  145 , external to the processor  145 , or a combination thereof. The controller  110  also includes other circuits such as input/output circuits and communication circuits (not shown). The controller  110  can store in the memory  150  information on objects detected in a video signal or data from the camera  115 , and track the movement of the objects over time. 
         [0016]    The HMI  140  provides an interface between the system and a driver. The HMI  140  provides one or more suitable input methods such as buttons, a touch-screen display having menu options, voice recognition, etc. for turning on/off functions (not shown). The HMI  140  also provides warnings or indications to the driver of other vehicles that may pose a potential risk. The HMI  140  provides the warning using a suitable indicator such as a tell-tale light on an instrument cluster, a warning icon on a mirror, a heads-up display, etc., an acoustic alarm such as a chime or buzzer, and/or a haptic indicator (e.g., vibrating the steering wheel). The system can provide different warnings based on a level of the potential risk. For example, the system can flash an icon when a vehicle is approaching the host vehicle&#39;s blind spot, and can light continuously when the vehicle is in the host vehicle&#39;s blind spot.  FIGS. 2A and 2B  illustrate an exemplary side view mirror blind spot indicator.  FIG. 2A  shows the mirror  130  when a vehicle is not in the blind spot. The entire area of the mirror  130  is reflective allowing a driver to see to the side and behind the vehicle  100 . When another vehicle is detected in the blind spot, an icon  180  is lit in a corner of the mirror  130 . 
         [0017]      FIG. 3  shows a construction of another portion of the HMI  140 . The portion includes a display  200  (e.g., an LCD display) and a plurality of buttons  205  positioned in a dashboard  210  of the host vehicle  100 . In some constructions, the display  200  includes a touch-screen enabling an operator to provide input to the system via the display  200 . 
         [0018]    The camera  115  is mounted on a rear R of the vehicle  100 , and has a field-of-view (FOV)  220  extending rearward from the vehicle  100 . The FOV  220  is the area in which the camera  115  is able to detect light reflected off of objects. The camera  115  converts the reflected light into a video signal. The size (e.g., viewable angle) of the FOV  220  is dependent on the construction of the camera  115 , such as the camera&#39;s focal length. 
         [0019]    When the host vehicle  100  is backing up (i.e., the transmission is in reverse), the HMI  140  receives the video signal and displays an image which is indicative of a view of the area in the FOV  220 . The displayed image assists the driver in backing up the vehicle by showing objects that are behind the host vehicle  100 . In some embodiments, the video signal is fed directly to the HMI  140 , and the controller  110  controls when the HMI  140  displays the video image (e.g., when the host vehicle  100  is backing up). In other embodiments, the video signal is fed to the controller  110 , and the controller  110  feeds the video signal to the HMI  110  when appropriate (e.g., when the host vehicle  100  is backing up). 
         [0020]    When the host vehicle  100  is not backing up, the HMI  140  does not display the video image. However, the camera  115  still picks up images in the FOV  220 , and produces the video signal. The controller  110  uses the video signal to determine when another vehicle enters one of the host vehicle&#39;s blind spots, and issues an alarm (e.g., lights an icon  180  in a side view mirror  130  or  135 ) to warn the driver of the vehicle in the blind spot. 
         [0021]      FIG. 4  depicts vehicles near the vehicle  100  which may be detected by the blind spot detection system  102 . The host vehicle  100  is traveling down a three-lane highway  305 . A second vehicle  310  is in the driver&#39;s blind spot where the driver may not be able to see the second vehicle  310  (e.g., via a mirror or the driver&#39;s peripheral vision). The second vehicle  310  is depicted traveling a distance behind host vehicle  100 . The controller  110  detects the second vehicle  310  and determines whether the second vehicle  310  is in the host vehicle&#39;s blind spot as described in greater detail below. The controller  110  makes this determination based on the distance the second vehicle  310  is from the host vehicle  100 , and how fast the vehicle  310  is moving relative to the host vehicle  300 . 
         [0022]      FIG. 5  illustrates exemplary zones of danger and operating parameters for the blind spot detection system  102 . The blind spot detection system provides a warning to the driver whenever an object (e.g., a vehicle) is adjacent the host vehicle  100  (e.g., within an area bounded by a middle  405  of the host vehicle  100  to about 3 meters behind the host vehicle  100  and from about 0.5 meters to the left and right of the host vehicle  100  to about 3 meters left and right, respectively, of the host vehicle  100 ). 
         [0023]    In one embodiment, the blind spot detection system is implemented using three different zones of danger A, B, and C, respectively, as shown in  FIG. 4 . In addition to the zones of danger, there is a blind spot detection (BSD) area. Each zone (A, B and C) covers a different area in a lane  410  and a lane  415  adjacent to a lane  420  that host vehicle  100  is presently in. Specifically, the area covered by zone A extends from about 3 meters to about 25 meters behind the host vehicle  100 , the area covered by zone B extends from about 3 meters to about 45 meters behind the host vehicle  100 , and the area covered by zone C extends from about 3 meters to about 70 meters behind the host vehicle  100 . 
         [0024]    All zones A, B (which includes zone A), and C (which includes zones A and B) are bounded by an area about 0.5 meters from the side of the host vehicle  100  to about 3 meters from the side of the host vehicle  100 . By tracking vehicles detected in the zones, the controller  110  can estimate if and when a vehicle will be in the host vehicle&#39;s blind spot. Each zone has a different time-to-blind-spot threshold. 
         [0025]    The controller  110  detects vehicles in the FOV  220  of the camera  115 , and determines when the vehicle enters the blind spot. The controller  110  can detect the wheels of the vehicle during daylight hours and can detect headlights of the vehicle during darkness. The controller  110  then determines a position of the vehicle relative to the host vehicle  100  as well as a closing rate. U.S. patent application Ser. No. 12/758,394 entitled “Video Based Intelligent Vehicle Control System” filed Apr. 12, 2010, the entire content of which is incorporated by reference, describes systems and methods for detecting objects using images obtained from a camera, and determining their positions relative to a host vehicle including how those positions are changing (e.g., a closing rate). 
         [0026]    Referring back to  FIG. 1 , the host vehicle  100  can also include additional sensors such as rear, cross-traffic alert object detection devices  450  and/or blind spot object detection devices  455  (e.g., embedded in the side view mirrors  130  and  135 ). The rear, cross-traffic alert object detection devices  450  are positioned on the right and left rear sides of the host vehicle  100  and have a FOV  460 . As described in U.S. patent application Ser. No. 12/855,238 entitled “Combined Lane Change Assist and Rear, Cross-Traffic Alert Functionality” filed Aug. 12, 2010, the entire content of which is hereby incorporated by reference, the controller  110  receives indications from the rear, cross-traffic alert object detection devices  450  when objects are in their FOV  460  and warns the driver if another vehicle is approaching the host vehicle  100  when the host vehicle  100  is backing up. The rear, cross-traffic alert object detection devices  450  can be radars (e.g., 24 GHz or 77 GHz mid-range radar sensors), light detecting and ranging (LIDAR) sensors, video cameras, etc. The blind spot object detection devices  455  in the side view mirrors are similar devices to the rear, cross-traffic alert object detection devices  450 , and have a FOV  465 . 
         [0027]    The object detection devices  450  and  455  detect objects that are within their FOVs  460  and  465 . The object detection devices  450  and  455  can detect where an object is within the FOV  460  or  465  (e.g., using a time-of-flight method), and how fast and in what direction the object is moving, and an acceleration of the object (e.g., using Doppler effects). In some embodiments, the object detection devices  450  and  455  communicate the location and motion (e.g., speed, acceleration, and direction) information of objects they detect to the controller  110 . In other embodiments, the object detection devices  450  and  455  communicate raw data (e.g., transmitted and received frequencies, time-of-flight, etc.) to the controller  110  and the controller  110  determines one or more of the location, speed, acceleration, and direction of detected objects. In some embodiments, the controller  110  merges the data from the object detection devices  450  and  455  together. In other embodiments, one of the object detection devices  450  and  455  merges the data together and communicates the merged data to the controller  110 . 
         [0028]    In some embodiments, the controller  110  uses information from the camera  115  and one or more object detection devices  450 / 455  to determine when a vehicle is in the host vehicle&#39;s blind spot. For example, the controller  110  can detect a vehicle approaching the host vehicle  100  from the rear using the camera&#39;s video image and extrapolate when the vehicle will be in the blind spot. When the vehicle eventually leaves the FOV  220  of the camera  115 , the controller  110 , based on the extrapolation, “guesses” when the vehicle is in the blind spot, and when the vehicle will have moved out of the blind spot. However, in a host vehicle  100  with one or more object detection devices  450 / 455 , the controller  110  can use information obtained from these devices  450 / 455  to monitor the vehicle while it is in the blind spot. An alarm provided to the driver is thus based on information from the camera  115  and the object detection devices  450 / 455 . A “preliminary” alarm (e.g., a flashing icon on a side-view mirror) can be provided as a vehicle is approaching the blind spot (e.g., based on the video image from the camera  115 ), but has not yet entered the blind spot (e.g., is determined to be in zone A). Another alarm (e.g., a solid icon on a side-view mirror) can be provided when the vehicle is in the blind spot (e.g., as detected by an object detection device  450 / 455  and/or based on extrapolation of the vehicle&#39;s position from the video image). 
         [0029]    In a situation where the host vehicle  100  is overtaking another vehicle, the object detection devices  450 / 455  can detect the vehicle when it enters the blind spot and trigger an alarm. Once the vehicle is behind the host vehicle  100 , the vehicle will be in the camera&#39;s FOV  220 , and the controller  110  turns off the alarm. In some embodiments, the controller  110  provides the preliminary alarm until the vehicle is a predetermined distance behind the host vehicle  100  (e.g., moves from zone A to zone B). 
         [0030]    By using both the indications received from the object detection devices  450 / 455  and the video signal from the camera  115 , the controller  110  can make more accurate decisions as to the presence of a vehicle in the blind spot. The use of components (e.g., the camera  115  and the object detection devices  450 ) already on the host vehicle  100  (i.e., for use with other functions such as back up assist and rear, cross-traffic alert) results in reduced cost of implementing a blind spot detection system. 
         [0031]    Various features and advantages of the invention are set forth in the following claims.