Abstract:
An improved vision-based system generates object detection corresponding to different viewing areas based on vehicle speed. At lower vehicle speeds, the system covers a wider field of view and a near zone while at higher vehicle speeds the system covers a normal or narrower field of view and a far zone. The system includes a lens package having a movable lens, an image sensor and an image transformer. The movable lens is movable between a first position representing a wide angle view and a second position representing a normal angle view. Each of these views generates an image such that a wide angle view generates a wide angle image and a normal angle view generates a normal angle image. The wide angle view is associated with the vehicle&#39;s passive safety systems while the normal angle view is associated with the vehicle&#39;s active safety systems.

Description:
TECHNICAL FIELD 
     The disclosed inventive concept relates generally to vision-based sensing systems for automotive safety applications. More particularly, the disclosed inventive concept relates to a vision sensor coupled to an optical system that generates object detection corresponding to different viewing areas based on vehicle speed and is thus capable of sensing both a wide field of view at a near zone and a narrow field of view at a far zone. 
     BACKGROUND OF THE INVENTION 
     Many modern vehicles include rudimentary collision avoidance systems of some type. Some vehicles include more sophisticated systems such as adaptive cruise control and forward collision warning. 
     While many such systems are sensor-based and rely upon, for example, radar, light detection and ranging systems, infrared range finders, sound navigation and the like, more recently the use of vision-based sensing systems for automotive safety applications has grown in popularity because of their greater image generation accuracy. 
     Regardless of the sensor arrangement employed, today&#39;s sensing systems for safety applications face a common challenge, which is to combine both active and passive applications into a single safety system. Active safety systems are designed for applications such as adaptive cruise control, forward collision warning, lane keeping aids and the like, and thus require far distance coverage (for distances up to about 160 meters) with a relatively narrow field of view. Conversely, passive safety systems are designed for sensing objects more local to the vehicle, such as pedestrians. Passive safety systems thus require near distance coverage (for distances up to about 30 meters) with a relatively wide field of view. 
     It would thus be advantageous if a single vision-based sensing system was available that can be used for both active and passive safety applications and which can accommodate different distance and field of coverage requirements. Such a system would overcome the problems realized today by vehicle designers and manufacturers. Therefore, there is a need in the art for such a system. 
     SUMMARY OF THE INVENTION 
     The disclosed inventive concept overcomes the problems associated with known vision-based vehicle safety systems. Particularly, the disclosed inventive concept relates to an improved vision-based system that generates object detection corresponding to different viewing areas based on vehicle speed. In addition to vehicle speed other inputs relied upon to determine field of view change might include vehicle yaw rate, longitudinal acceleration, digital mapping and the like. 
     At lower vehicle speeds the vision-based system of the disclosed inventive concept preferably covers a wider field of view and a near zone while at higher vehicle speeds the system preferably covers a normal or narrower field of view and a far zone. A controller is coupled to the vision sensor to generate safety system signals for both passive and active safety systems. 
     The vision-based system of the disclosed inventive concept includes a lens package that includes a movable lens, an image sensor and an image transformer. The movable lens of the lens package is movable between a first position representing a wide angle view and a second position representing a normal angle view. Each of these views generates an image, that is, a wide angle view generates a wide angle image and a normal angle view generates a normal angle image. The wide angle view is associated with the vehicle&#39;s passive safety system while the normal angle view is associated with the vehicle&#39;s active safety system. 
     The system further includes an image sensor for receiving the wide angle and normal angle images and an image transformer for transforming the objects of the images to either a wide angle view or a normal view. 
     The vision-based system of the disclosed inventive concept further includes a control module operatively associated with the lens package, the image sensor, the image transformer and the vehicle. Inputs are connected to the control module, such inputs including but not being limited to a speed sensor, a yaw rate sensor, and a longitudinal acceleration sensor. Other inputs might provide the control module with information regarding the range, velocity and azimuth angle of an object captured by the lens package. 
     The operating protocol associated with the vision-based system of the disclosed inventive concept includes the basic steps of defining a threshold for vehicle speed, determining the vehicle speed, determining the position of the movable lens relative to the other fixed lens of the lens package, moving the movable lens to a wide angle position (if needed) if it is determined that the vehicle speed is below the threshold and moving the movable lens to a normal angle position (if needed) if it is determined that the vehicle speed is above the speed threshold. A wide angle image of an object or a normal angle image of an object is generated. The object in the image is transformed to either a wide angle view or to a normal angle of view as needed. 
     Thereafter the range, velocity and azimuth angle of the captured object are estimated. Once these parameters are estimated, the captured object is classified, identified and tracked. The detection confidence level of the captured object is then estimated. Finally, the gathered and interpreted information is broadcast to the vehicle. 
     The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein: 
         FIG. 1  is a schematic representation of an automobile vehicle showing a normal field of view for active safety systems and a wide field of view for passive safety systems; 
         FIG. 2  is a diagrammatic representation of a conventional lens in its normal position; 
         FIG. 3  is a diagrammatic representation of the conventional lens of  FIG. 2  in its wide angle position; 
         FIG. 4  is a diagrammatic representation of a lens package for a dual field of view according to the disclosed inventive concept shown in its normal position; 
         FIG. 5  is a diagrammatic representation of the lens package for a dual field of view of  FIG. 4  shown in its wide angle position; and 
         FIG. 6  depicts a logic flow diagram of the operation of an image system of the disclosed inventive concept using the lens package of  FIGS. 4 and 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting. 
     In general, the disclosed invention provides an image system for use with an automotive vehicle that includes a vision sensor coupled with an optical arrangement in which the lens positions can be changed. The sensor generates object detection corresponding to different viewing areas based on vehicle speed and, optionally, such variables as vehicle yaw rate, longitudinal acceleration, digital mapping and the like. 
       FIG. 1  illustrates a schematic representation of an automobile vehicle  10  that incorporates the image system of the disclosed inventive concept. Two fields of view are diagrammatically shown. These fields include a normal field of view for active safety defined by broken lines  12  and  12 ′ and a wide field of view for passive safety (particularly for pedestrian protection) defined by broken lines  14  and  14 ′. The fields of view and the broken lines that define them are shown for illustrative purposes only as they are suggestive and are not intended as being limiting. 
     The narrow or normal field of view for active safety applications is appropriate for active safety applications, such as “adaptive cruise control,” “forward collision warning,” “lane keeping aid” and the like. The normal field of view is not only narrower but is longer (about 160 meters) than that required for passive safety applications (about 30 meters). Due to pixel and resolution constraints at the vision sensor (discussed below), a narrower field of view may be advantageous for active safety applications. 
       FIGS. 2 and 3  are diagrammatic representations of known lens systems illustrating lenses in different positions. For both  FIGS. 2 and 3 , the following may be used: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 S 1   
                 Distance between the lens and the object 
               
               
                 S 2   
                 Image plane distance 
               
               
                 F 
                 Focal length 
               
               
                 α 
                 Angle of view 
               
               
                 d 
                 Sensor dimension 
               
               
                   
               
             
          
         
       
     
     Particularly,  FIG. 2  is a diagrammatic representation of a lens system  20  in which a conventional lens  22  is in its normal position. An image-receiving sensor  24  is adjustably positioned at a specified focal length F from the conventional lens  22 . This arrangement is suitable for viewing a distant object such as a vehicle. As is illustrated in  FIG. 2 , when the lens  22  is further from the sensor  24 , the image plane formed on the sensor  24  is further away from the lens  22 . 
       FIG. 3  is a diagrammatic representation of the lens system  20  in which the lens  22  has been relocated closer to the image-receiving sensor  24  to its wide angle position. The image-receiving sensor  24  is fixed thus the focal length F has been reduced. This arrangement is suitable for viewing a nearby object such as a pedestrian. As is illustrated in  FIG. 3 , when the lens  22  is in a position closer to the sensor  24  the image plane formed on the sensor  24  is closer to the lens  22 . The position of the lens  22  relative to the fixed image-receiving sensor  24  (and thus the focal length) may be changed by a motor and the like. 
       FIGS. 4 and 5  illustrate a dual field of view image system for automotive applications. The image system, generally illustrated as  30 , includes a housing  32 . Within the housing  32  is positioned a lens package  34  and an image sensor  36 . The lens package  34  consists of a fixed lens (not shown) and a movable lens  38 . The movable lens  38  can be adjusted to one of two positions, a normal field of view position  40  and a wide angle field of view position  42 . Movement of the movable lens  38  is effected by a motor for mechanical adjustment or by another mechanical device (not shown). 
     The image system  30  is attached to a system control module  44  that is, in turn, attached to the vehicle&#39;s operating system. The control module  44  includes a feature for transforming objects received by the image sensor  36  reversibly between a wide angle view and a normal angle view. 
     As shown in  FIG. 5 , in the normal field of view position  40  the received image fills a larger amount of the image sensor  36  while in the wide angle field of view position  42  the received image fills smaller portion of the screen. Thus image transformation is necessary due to the changes in pixel position between the normal angle view and the wide angle view. Transformation can be achieved by hardware associated with the control module  44  having an appropriate algorithm or by an algorithm programmed into the control module  44 . 
     The control module  44  receives various inputs from the vehicle  10 . These inputs include a vehicle speed sensor  46  that signals vehicle speed to the control module  44 . Additional sensors might be added as needed and might include a vehicle yaw rate sensor  48  and a vehicle longitudinal acceleration sensor  50 . The vehicle yaw rate sensor  48  and the vehicle longitudinal acceleration sensor  50  both provide information as to vehicle operating parameters to the control module  44  which regulates the position of the movable lens  38  relative to the fixed lens. 
     The position of the movable lens  38  shown in  FIG. 4  is set at a normal field of view position  40 , for example, at 42 degrees. This is the position the movable lens  38  would have during vehicle speeds greater than a certain threshold, such as 48 kph, for active safety applications. This arrangement makes it possible to achieve better coverage for active safety applications, particularly when the object is far away, for example, between about 50 m and 200 m away. In this position the image that appears on the image sensor  36  provides coverage for a narrower field of view. 
     If the vehicle speed falls below the specified threshold, again, for example, 48 kph, the lens is moved to its wide angle field of view position  42  as shown in  FIG. 5  for passive safety applications. In this position wide fields of view of, for example, 100 degrees and above are attainable. As a consequence the size of the object image that appears larger in the normal position (dN) is transformed to appear relatively small (d s ) on the image sensor  36 . 
     Because the relatively small image that is created when the image system  30  is in its wide angle position, the image size needs to be transformed to allow for proper image tracking by the image sensor  36 . Transformation of the image size into a smaller size occurs based on the following suggested conversion ratio: 
             ratio   =         d   S       d   N       =         f   S       f   N       ·       S       N   ⁢   _     ⁢   1           S       N   ⁢   _     ⁢   1       +     f   N     -     f   S                   
Other conversion ratios may be possible.
 
     In general, while the vehicle  10  is above a threshold speed its image system  30  operates in an active safety mode whereby the movable lens  38  is positioned for far distance coverage. When the speed of the vehicle  10  falls below the threshold speed the movable lens  38  is repositioned for wide angle coverage. Other inputs may be relied upon. Such other inputs may include yaw rate, longitudinal acceleration and digital mapping may be used by the control module  44  to position the movable lens  38 . The object information must be transformed between the near zone and far zone lens positions of the movable lens  38  whenever the movable lens position changes. 
       FIG. 6  depicts a logic flow diagram  100  for the operating protocol of an image system  30  of the disclosed inventive concept using the image system  30  incorporated into the vehicle  10 . In step  102 , the power to the image system  30  is switched to “on.” In step  104 , the threshold speed of the vehicle  10  is defined. The threshold speed may be selected from a range of speeds appropriate to the vehicle and other parameters. 
     In step  106 , the vehicle speed is obtained by the control module  44  from the vehicle speed sensor  46 . In step  108 , the query is made whether or not the vehicle speed exceeds the vehicle speed threshold defined at step  104 . If the response to the inquiry at step  108  is “no,” then at step  110  the inquiry is made whether or not the position of the movable lens  38  is set to its wide angle position. If the response to the inquiry at step  110  is “no,” then the movable lens  38  is repositioned to its wide angle position at step  112 . 
     Thereafter, at step  114 , the objects in the image produced in the image system are transformed to a wide angle view followed by step  116  in which the objects from the wide angle position are captured. 
     If the response to the inquiry at step  110  is “yes,” then the next step is also to capture the objects from the wide angle position at step  116 . 
     Once the objects are captured at step  116 , the range, velocity and azimuth angle of the vehicle  10  relative to the captured objects are estimated at step  118 . After the range, velocity and azimuth angle are estimated at step  118 , the observed targets are classified and identified by the control module  44  at step  120 . 
     The classified and identified targets are thereafter tracked in step  122 . Classification is based upon pre-selected values. Once classified and tracked, the confidence level of target detection is estimated in step  124 . Target detection confidence is based on a pre-selected range of target identification models. Following estimation of target detection confidence the information is broadcast to relevant vehicle systems in step  126 . 
     If, in step  108 , the response to the query whether or not the vehicle speed exceeds the vehicle speed threshold defined at step  104  is “yes,” then at step  130  the inquiry is made whether or not the position of the movable lens  38  is set to its normal angle position. If the response to the inquiry at step  130  is “no,” then the movable lens  38  is repositioned to its normal angle position at step  132 . 
     Thereafter, at step  134 , the objects in the image produced in the image system are transformed to a normal angle view. This is followed by step  136  in which the objects from the normal angle position are captured. 
     If the response to the inquiry at step  130  is “yes,” then the next step is also to capture the objects from the normal angle position at step  136 . 
     Once the normal angle objects are captured at step  136 , the range, velocity and azimuth angle of the vehicle  10  relative to the captured objects are estimated at step  118 . After the range, velocity and azimuth angle are estimated at step  118 , the observed targets are classified and identified by the control module  44  at step  120 . 
     The classified and identified targets are thereafter tracked in step  122 . Once classified and tracked, the confidence level of target detection is estimated in step  124 . Target detection confidence is based on a pre-selected range of target identification models. Following estimation of target detection confidence, the information is broadcast to relevant vehicle systems in step  126 . 
     Regardless if, in step  108 , the speed threshold is exceeded or not, once the information from step  124  is broadcast at step  126 , the power may be turned off at step  128  in which case the protocol is at an end. However, if the power is not turned off, the vehicle speed is again obtained at step  106  to be followed by the steps of the protocol set forth above. 
     The disclosed invention as set forth above overcomes the challenges faced by known active and passive safety systems for vehicles. However, one skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.