Abstract:
Provided is a system that includes a first camera and a second camera each configured to capture image data from respective viewing angles, and a data processor coupled with the first camera and the second camera, that receives the image data, calculates a range based on the image data received and validates the calculated range for a parking space.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to roadway lighting systems. In particular, the present invention relates to performing stereoscopic range determination in a system. 
       BACKGROUND 
       [0002]    Conventional parking space detection systems employ parking sensors within parking spaces based, for example, on the radio frequency identification (RFID) technology. Alternatively, a camera can be employed to capture a single image of the parking space, or image of the parking lot, to locate or determine occupancy of individual parking spaces. Also, camera sensors are sometimes used at parking lot entryways to perform trip-wire type detection to sense vehicle presence and motion. 
         [0003]    The accuracy, however, of these conventional detection systems can be compromised due to weather, poor lighting, or other objects within the parking spaces. Further, the installation of these conventional detection systems can be costly and time-consuming. 
       SUMMARY OF THE INVENTION 
       [0004]    Embodiments of the present invention provide a system and a stereoscopic range determination method for detecting occupancy of a parking space. 
         [0005]    In certain circumstances, an embodiment of the present invention includes a system having a first camera and a second camera. Each camera is configured to capture image data from respective viewing angles. The system also includes a data processor coupled with the first camera and the second camera. The data processor receives the image data, calculates a range based on the image data received and determines whether the range is a valid range for a parking space. 
         [0006]    The foregoing has broadly outlined some of the aspects and features of various embodiments, which should be construed to be merely illustrative of various potential applications of the disclosure. Other beneficial results can be obtained by applying the disclosed information in a different manner or by combining various aspects of the disclosed embodiments. Accordingly, other aspects and a more comprehensive understanding may be obtained by referring to the detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings, in addition to the scope defined by the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a block diagram illustrating a system that can be implemented within one or more embodiments of the present invention. 
           [0008]      FIG. 2  is a schematic illustrating an implementation of the system of  FIG. 1  within a roadway lighting system that can be implemented within one or more embodiments of the present invention. 
           [0009]      FIG. 3  is a schematic illustrating a position of a plurality of cameras of the system of  FIG. 1  that can be implemented within one or more embodiments. 
           [0010]      FIG. 4  is a flow chart illustrating a stereoscopic range determination method that can be implemented within one or more other embodiments of the present invention. 
       
    
    
       [0011]    The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the disclosure. Given the following enabling description of the drawings, the novel aspects of the present disclosure should become evident to a person of ordinary skill in the art. This detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of embodiments of the invention. 
       DETAILED DESCRIPTION 
       [0012]    As required, detailed embodiments are disclosed herein. It must be understood that the disclosed embodiments are merely exemplary of various and alternative forms. As used herein, the word “exemplary” is used expansively to refer to embodiments that serve as illustrations, specimens, models, or patterns. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. 
         [0013]    In other instances, well-known components, systems, materials, or methods that are known to those having ordinary skill in the art have not been described in detail in order to avoid obscuring the present disclosure. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art. 
         [0014]    Details regarding the system  100  of the present invention will now be discussed with reference to  FIG. 1 .  FIG. 1  illustrates the system  100  which can be implemented within a roadway lighting system  150  (as depicted in  FIG. 2 ). The present invention is not limited to implementation within roadway lighting systems and can be implemented within other systems. 
         [0015]    As shown in  FIG. 1 , the system  100  includes a power supply  102 , a data processor  104 , and a memory  106 . The system  100  also includes a data communication unit  108  (e.g., a data radio unit), at least one antenna  110  and a plurality of cameras (cameras  1  and  2 )  120   a  and  120   b.    
         [0016]    The power supply  102  can be a separate power supply or integrated within the power supply of the roadway lighting system. The power supply  102  can be solar-powered. The power supply  102  supplies power to the components of the system  100 . 
         [0017]    The data processor  104  can include a computer or server. The data processor  104  can include an analog or digital processor. 
         [0018]    The memory  106  can include hardware or storage media to store data and/or instructions for operating the cameras  120   a  and  120   b . By way of example, the data includes parking facility information, image data, historical data or other suitable information. The instructions include software programming that can be executed by the data processor  104  to perform a technique for determining parking space occupancy. 
         [0019]    The data communication unit  108  can perform wired or wireless communication. The wired communication can include a local area network (LAN) or wide area network (WAN), or directed optical connection or electrical connection. The wireless communication can be radiofrequency (RF) communication, cellular or Bluetooth type communication. Operations of the data communication unit  108  are performed using the antenna  110 . 
         [0020]    The system  100  is configured for communicating with other external systems or components of the roadway lighting system  150 . For example, the system  100  can communicate with a metering system to provide timing information associated with the length of time a parking space has been occupied for purposes of billing or ticketing. 
         [0021]    The cameras  120   a  and  120   b  are mounted to a pole  155  (as depicted in  FIG. 2 ) or other fixed object of the roadway lighting system  150 . The cameras  120   a  and  120   b  are mounted in a fixed position to each capture images  122  and  124  from a respective viewing angle, of a target  130 . As an example, the target  130  can be a parking space, a car, or some other object or person within the parking space. In particular, the images  122  and  124  can be used to gather other occupancy data (e.g., vehicle license plate information, occupancy time information) associated with the target  130  within a parking space. The cameras  120   a  and  120   b  can also be used to capture other data such as traffic data, weather data and crosswalk usage data. 
         [0022]    In  FIG. 2 , the system  100  performs a ranging technique, such as stereoscopic range determination, to determine occupancy of a parking space. The plurality of cameras  120   a  and  120   b  independently capture images  122  and  124  (as depicted in  FIG. 1 ) respectively, of the parking space  200 . The system  100  performs the range determination using the camera  120   a  and  120   b , as each camera can be utilized to determine the range to a given target  130  (e.g., the parking space  200 ), with slightly different perspectives as accorded by their respective camera-to-camera spacing. 
         [0023]    The ranging methodology (e.g., stereoscopic range determination) is based on a baseline distance between cameras  120   a  and  120   b  (as further discussed below regarding  FIG. 3 ). The ranging methodology is also a function of the distance to the target  130 , the field of view (FOV) of the lens of the cameras  120   a  and  120   b  and the resolution of the camera sensor as measured by its Instantaneous Field of View (IFOV) which is calculated by dividing the total Field of View by the number of pixels in that direction. The cameras  120   a  and  120   b  capture images  122  and  124  and are used to calculate the minimum distance to the parking space and a maximum distance to the parking space, respectively (as indicated by the arrows) to determine the range. Calculating distances using the stereoscopic range finding method will cause an increase in increments of measurement as the distance to the target  130  increases, and as the distance to the target  130  decreases, the increment of measurement decreases. 
         [0024]    According to one or more embodiments, the cameras  120   a  and  120   b  can be mounted such that the optical axes of their lenses are parallel to each other which will generate a desired parallax shift or the perspective difference between the cameras  120   a  and  120   b  as discussed above. The perspective difference between the two cameras  120   a  and  120   b  forms the basis for the equation below used to determine the range to the target  130 . The system  100  is effectively measuring the difference between the relative angle views of the cameras  120   a  and  120   b  to the target  130  as represented by the two different images  122  and  124 . 
         [0025]    The calculation of the pixel shift for the target  130  found in the images  122  and  124  can be used to determine the range to that target  130 . In some cases, the optical axes of the lenses of the cameras  120   a  and  120   b  may not be parallel to each other, such that there can be a minimal amount of parallax error between the cameras  120   a  and  120   b  which is accommodated by the method as discussed below with reference to  FIG. 4 . 
         [0026]    The image data, associated with the captured images  122  and  124 , is transmitted from the cameras  120   a  and  120   b  to the data processor  104  for processing. The data processor  104  calibrates the range data received to determine if the range is valid (e.g., 25 feet) for a parking space  200  in order to determine occupancy by a car, or whether a person or object occupies the parking space  200 . According to embodiments of the present invention, the range will be less than 80 feet. 
         [0027]    The calibration operation further includes calculating offsets in both vertical and horizontal directions versus the target and storing this information in memory  106  for further use in determining the range to the target  130 . It should be noted that although the description involves the detection of an empty parking space according to some embodiments, the present invention can also detect an occupancy of the parking space. Further details regarding the range determination is discussed below with reference to  FIG. 3 . 
         [0028]    As shown in  FIG. 3 , range validation can be determined as a function of several variables. For example, (I) is the distance between the cameras  120   a  and  120   b , (dZ h ) is the depth resolution between the images captured by the cameras  120   a  and  120   b , (Z) is the range of the target  130  and (ΔT) is the Instantaneous Field of View (IFOV) of the lens for each camera  120   a  and  120   b . The relationship between these variables can be expressed in the equation: 
         [0000]    
       
         
           
             
               dZ 
               h 
             
             = 
             
               
                 
                   Z 
                   2 
                 
                  
                 Δ 
                  
                 
                     
                 
                  
                 T 
               
               I 
             
           
         
       
     
         [0029]    In the embodiments, and by way of example, the cameras  120   a  and  120   b  can be spaced apart a predetermined distance (I) of 5 to 20 inches. The depth resolution (dZ h ) can be approximately ±1.5 feet for cameras  120   a  and/or  120   b  having a megapixel count of 1.2 and a lens with approximately 80 degree Horizontal Field of View (HFOV). The cameras  120   a  and  120   b  are not limited to any particular depth resolution, megapixel count or IFOV, and can therefore vary accordingly. 
         [0030]      FIG. 4  is a flow chart illustrating a stereoscopic range determination method  400  according to one or more embodiments of the present invention. As shown in  FIG. 4 , the method  400  begins at operation  410  where a first camera and a second camera are disposed a predetermined distance apart in a fixed position (e.g., on a pole). From operation  410 , the process continues to operation  420  where the first camera captures a first image and the second camera captures a second image. 
         [0031]    In  FIG. 4 , the first image represents a minimum distance to a parking space and the second image represents a maximum distance to the parking space. From operation  420 , the process continues to operation  430  where the image data from the first camera and the second camera is transmitted to a data processor for processing. From operation  430 , the process continues to operation  440  where the processor determines a range using the minimum distance and the maximum distance obtained by the first and second cameras as shown in  FIGS. 2 and 3 , and determines whether the range is a valid range for a parking space. 
         [0032]    According to other embodiments, the method  400  can employ a pattern matching algorithm to initially and periodically calculate the parallax offset between the two cameras. In the event of platform or pole movement from wind and other vibration excitations, there may be differences in the appearance between the two cameras if so, instantaneous re-calculation using the pattern matching algorithm can increase accuracy. 
         [0033]    Embodiments of the present invention provide the advantages of determining parking space occupancy using a valid range without having to view the parking space itself, thereby eliminating errors in determining occupancy. 
         [0034]    This written description uses examples to disclose the invention including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.