Abstract:
A system in a moving surveillance vehicle operates in background mode to capture images of license plates of neighboring moving vehicles, which may occupy lanes other than the lane in which the surveillance vehicle is moving. The images are used to determine the license plate numbers of the moving vehicles, which are then checked against a database to determine whether there are any potential law enforcement-related problems that require the attention of the operator. If so, the system alerts the operator using an audible tone, visual prompt, vibration, or in some other suitable manner. The entire process, including generation of the alert can occur autonomously of the operator.

Description:
This application is a continuation of U.S. patent application Ser. No. 12/757,262 filed Apr. 9, 2010, which is a continuation of U.S. patent application Ser. No. 10/546,555 filed Aug. 22, 2005, now issued U.S. Pat. No. 7,711,150, which is a U.S. National Phase of PCT/US03/21958 filed Jul. 10, 2003. These and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to license plate recognition. 
     BACKGROUND OF THE INVENTION 
     Traffic police, highway patrol and other mobile security personnel have a need to accurately and efficiently identify potential law enforcement problems with respect to nearby motor vehicles. One well-recognized strategy is to “run” license plate numbers of such vehicles against a database. 
     It is a well known practice for an officer in a patrol car to visually read a license plate of a target vehicle, and then call in the number to a support center. It is also known for an officer to utilize an on-board digital video camera to capture an image of the vehicle license plate of a parked vehicle, and even to use an on-board computer to analyze the image to determine the license plate number. In both cases, however, conscious effort is required on the part of the officer, which diverts attention from driving or other activities. In some cases the diversion of attention can be dangerous, and can even contribute to an otherwise preventable car accident. 
     A highly advanced license plate recognition and checking system is described in Japanese patent 11-296785, published on Oct. 29, 1999, the disclosure of which is incorporated herein in its entirety by reference. In that system the patrol car is provided with an on-board camera and camera controller, optical character recognition (OCR) software, a database, and a display device. While moving along a road, the driver places the patrol car in front of or behind the target car, and then triggers operation of the camera. The camera photographs the license plate of a preceding or following target vehicle, and sends the captured image to the on-board computer. OCR software running on the computer determines the license plate number, and applies that number against the on-board database. The results are displayed to the operator. 
     Apparently, the inventors of Japanese patent 11-296785 did not appreciate that (a) forcing the driver of the patrol car to maneuver his vehicle relative to the target vehicle, and (b) forcing the operator to trigger the camera, involve conscious efforts on the part of the driver, which preclude the system from operating in a truly autonomous fashion. The issue of being fully autonomous is not a mere design choice. Fully autonomous operation is not only safer and more thorough, it also has a particularly important function in countering accusations of racial profiling. If a system could be devised that would autonomously process license plate information of all vehicles in view of the camera, including vehicles in other lanes, then the operator could not be reasonably accused of focusing on any particular car or driver. 
     Thus, there is still a need for more fully autonomous surveillance of moving automotive vehicles from another moving vehicle. 
     SUMMARY OF THE INVENTION 
     The present invention is generally directed to systems and methods in which a first moving vehicle (surveillance vehicle) captures vehicle license plate number information from a second moving vehicle in a fully autonomous fashion, and applies that information against a database to identify potential problems with the second vehicle or its driver. In preferred embodiments the surveillance vehicle is preferably a police car or other patrol unit; and the second vehicles can be in any lane that is visible from the camera, including the same lane as that occupied by the first vehicle, other driving lanes, and even in parking areas or road shoulders. 
     A digital video camera with a wide-angle lens is preferably used to capture the license place information. Alternatively, any other suitable image-capturing device could be used, including a still-image camera. The camera can advantageously be mounted on the front, rear, side or top of the surveillance vehicle, and preferably has a viewing angle range of at least 120°. 
     An on-board processor can either (a) perform optical character recognition on an acquired image to determine the license plate number, or (b) transmit at least a portion of the image to a remote site for that determination. The license plate number can then be applied against one or more databases, which can be local and/or remote to the camera and processor, to identify potential problems with the car or driver of the second vehicle. 
     Ideally, each of these functions is carried out continuously, in background mode without any input from the driver or other operator of the vehicle carrying the system. When potential problems are identified, the operator is notified using an auditory, visual or other alert. 
     Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side perspective view of a moving surveillance vehicle carrying a surveillance system according to the inventive subject matter, with neighboring vehicles in various lanes. 
         FIG. 2  is a schematic representation of the surveillance system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  generally depicts a surveillance vehicle  10  equipped with a surveillance system  20  (see  FIG. 2 ) that is driving along a roadway  30  in lane  32 . Another vehicle  40  is traveling ahead of surveillance vehicle  10  in lane  22 , while vehicles  42 ,  44  are traveling in the same direction as surveillance vehicle  10  in lane  34 . Vehicles  46  and  48  are traveling in the oncoming direction in lane  36 , across low median  35 . Surveillance system  20  generally comprises first and second digital video cameras  22 A,  22 B, a processor  24  (see  FIG. 2 ), and a signal generator  28  (see  FIG. 2 ). 
     The surveillance vehicle  10  will often be a patrol car  10 , but can be any road or off-road vehicle, including jeeps, trucks, ambulances, buses, recreational vehicles, fire engines, and so forth. The neighboring vehicles  40 ,  42 ,  44 ,  46  and  48  can likewise be any combination of any types of vehicles, and will obviously be dispersed around the patrol car  10  in a manner that varies infinitely over time. Most of the neighboring vehicles  40 ,  42 ,  44 ,  46  and  48  will have rear license plates, and some can have front license plates. In this drawing, the relevant license plates for vehicles  40 ,  42 ,  44 ,  46  and  48  are  40 A,  42 A,  44 A,  46 A, and  48 A, respectively. 
     Cameras  22 A,  22 B are mounted at the front and rear portions of surveillance vehicle  10 . Mounting can be on the bumpers or anywhere else, and can even be located in other positions such as in the siren tower on top of the surveillance vehicle  10  or inside the cab behind the windshield. One or both of cameras  22 A,  22 B can be mounted in the center line of the surveillance vehicle  10 , or off-center in any suitable manner. There must of course be at least one camera, which could provide front, rear, side or combination coverage. Second, third, and other cameras are optional. A person skilled in the art should recognize that more than two cameras could be mounted on surveillance vehicle  10  in suitable locations (e.g., front, rear, side or top of vehicle) to allow up to 360° license plate scan coverage. 
     Each camera  22 A,  22 B has a lens (not shown) that “sees” license plates within their respective viewing angles  24 A,  24 B. A wide-angle lens (not shown) is optional, and where present would preferably be a high-precision spherical lens adapted to minimize distortion and other aberrations for sharp and high-contrast images with a viewing angle range of about 75°-150°. Preferred viewing angles are at least 90°, more preferably at least 120°, still more preferably at least 150°, and most preferably at least 160°. Viewing angles  24 A,  24 B are shown as being pointed directly forward and aft of surveillance vehicle  10 , but can alternatively be pointed in other directions as well. The viewing direction can optionally be motorized to scan a swath of area up, down, and sideways, or to point in a particular direction, and those functions can be automated and/or manual. As drawn, forward camera  22 A can “see” license plates  40 A, and  42 A, but not license plate  48 A. Rearward camera  22 B can “see” license plate  44 A, but not license plates  46 A. 
     In  FIG. 1  cameras  22 A,  22 B are ordinary video cameras. Other types of cameras can be used, including still cameras, charge-coupled device cameras for higher resolution, infrared cameras for night operations, and so forth. The focus is most likely set to infinite, but there can also be an automatic focusing mechanism (not shown). One or both of cameras  20 ,  22  can be advantageously provided with illumination, which can be in the form of a controlled light source (not shown) adapted to brighten vehicle license plates during the day and/or allow camera operation during the night. Alternatively, the illumination means can be an infra-red (IR) light source, i.e. invisible to the driver of the neighboring vehicles. 
     In  FIG. 2  surveillance system  20  generally comprises first and second digital video cameras  22 A,  22 B, a processor  24 , memory  26 , and an alert generator  28 . 
     Processor  24  can be any suitable processor, including for example CPU(s) (central processing unit(s)) made by Intel Corp. (e.g., Pentium®, Xeon®), AMD (e.g., Athlon®), Motorola, IBM, etc., I/O (input/output) circuits, communication bus links, etc. Processor  24  receives digital image data input from cameras  22 A,  22 B, and processes the data software resident in memory  27 . The software preferably includes an operating system (OS) (e.g., Windows®, Linux®, Unix®, Free BSD®, etc.), and optical character recognition programs. 
     Memory  27  can also advantageously include county-wide, state-wide, nation-wide, or even multi-country vehicle license plate number data, as well as related information of interest such as law enforcement-related data. Information that is not available on-board the surveillance vehicle  10  can be accessed wirelessly from a remote facility  60 . In that case system  20  would need to be adapted for wireless connection using communication hardware  29 . 
     Optical character recognition preferably occurs on board vehicle  10 , but may alternatively or additionally occur in the remote facility  60 , or elsewhere. Any suitable OCR software can be used, such as that of Hi-Tech Solutions, currently available through www.htsol.com. Many suitable OCR algorithms operate in three stages. The first stage involves vectorizing the captured (raster) image. The second stage deals with isolation of the vectors that describe the raster image. The third stage performs the subsequent alphanumeric character recognition to generate a plate string. More details on suitable theory, methods and algorithms can be found on the World-Wide-Web at: http://www.cae.wisc.edu/˜woochull/course/lpr.html; http://www.cs.technion.ac.il/Labs/Isl/Project/Projects_done/cars_plates/finalreport.htm; http://www.singaporegateway.com/optasia/imps, or in numerous literature sources such as, for example, “Computer Graphics: Principles and Practice”, Foley, van Dam, Flener, and Hughes, Addison Wesley, Reading, Mass., 1990; which are incorporated herein by reference. 
     To lower cost, the processor  24 , memory  28 , and communication hardware  29  would generally be included as part of a laptop or other computer (shown generally as component  21 ) that had already been installed in vehicle  10  for other purposes. Alternatively, processor  40 , memory  42 , GUI  50 , local license plate number database module  44 , and speaker  46  can be implemented as an integral part of cameras  22 A,  22 B. 
     The network used to communicate with remote facility  60  could be the same network already being used by computer  21 , or could be some other network. Transmission of license plate data between processor  24  and remote facility  60  can be encrypted using any suitable data encryption algorithms to ensure data security. 
     Processor  24  cooperates with one or more alert devices, such as speaker  28 A, computer display  28 B, or vibratory interface  28 C. Alternatively, processor  24  can utilize any other speaker (not shown) in the vehicle  10 . 
     The entire system  20  is preferably programmed to operate autonomously in background mode, i.e., without any input being required from the operator. The operator is preferably only alerted where the system  20  has identified a possible law enforcement-related problem using the captured license plate information. System  20  can be designed to operate continuously for an extended period of time while vehicle  10  is patrolling the streets/highways, and can be turned on and off by the operator as desired. 
     Multiple instances of system  20  can be installed and operated on multiple surveillance vehicles for more efficient license plate number check coverage, and the various systems may cooperate with each other by exchanging information. System  20  can also be operated in conjunction with global satellite or other positioning systems (not shown). Thus, for example, one squad car may identify a neighboring vehicle at a given location, and another squad car may identify the same vehicle 30 minutes later at another location. By calculating the distance traveled by the targeted vehicle, the system could calculate the minimum speed that the target vehicle traveled during that time frame. The vehicle license data gathered by system  20  during routine surveillance patrols could also be used for other than law enforcement purposes, as needed and/or authorized by local law regulations. 
     A contemplated method includes the following steps: The processor  26  activates one or more cameras  22 A,  22 B, which capture images of nearby vehicle license plates. The captured information is read by a frame grabber in each camera. Pixel output from the frame grabber(s) is passed by the processor  26  through image processing software algorithms to enhance the image, if necessary, detect the vehicle license plate position, and through OCR software algorithms determine a license place number. The processor then checks the license plate number against corresponding data records stored in memory  28 , or in remote license plate number facility  60 , for potential law enforcement-related vehicle problems. If a problem is identified, the operator (not shown) is alerted audibly, visually or in a vibratory manner using one or more of speaker  28 A, computer display  28 B, or vibratory interface  28 C, respectively. 
     While the present invention has been described in detail with regards to the preferred embodiments, it should be appreciated that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. In this regard it is important to note that practicing the invention is not limited to the applications described hereinabove. Many other applications and/or alterations can be utilized provided that such other applications and/or alterations do not depart from the intended purpose of the present invention. Also, features illustrated or described as part of one embodiment can be used in another embodiment to provide yet another embodiment such that the features are not limited to the specific embodiments described above. Thus, it is intended that the present invention cover all such embodiments and variations as long as such embodiments and variations come within the scope of the appended claims and their equivalents.