Patent Publication Number: US-6985827-B2

Title: Speed measurement system with onsite digital image capture and processing for use in stop sign enforcement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a continuation-in-part of application Ser. No. 09/812,228, filed Mar. 19, 2001, now U.S. Pat. No. 6,681,195 which claims the benefit of U.S. Provisional Application No. 60/191,171, filed Mar. 22, 2000. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates, in general, to speed detection of moving vehicles, and more particularly to compact, mobile speed detection systems that provide for accurate speed detection with accompanying image capture, processing, and production at the location of the field portion of the system, such as the present location of the law enforcement vehicle. 
   2. Relevant Background 
   Law enforcement agencies and personnel presently use a variety of speed measurement devices to monitor traffic and, more particularly, to identify vehicles that are going faster than posted speed limits. In addition to identifying a speeding vehicle, it has become increasingly common to attempt to capture images of such speeding vehicles and then to use the images to better enforce the speed limits (i.e., use the image as part of a ticketing program). While satisfying some of the needs of the law enforcement agencies, the existing speed measurement and image capture devices have not proven suitable or reliable for many law enforcement agency applications and have created operational problems that hinder the field use of such devices. 
   Various methods are used to detect the speed of moving vehicles, such as well-known radar systems. More recently, speed detection systems have incorporated lasers to accurately detect the speed of a moving vehicle and also the distance or range of the vehicle from the laser device. In general, laser speed detectors measure the time delay between the transmission of a series of pulses and a reflection of those pulses. The design and operation of laser speed detection and range finder systems may be found in U.S. Pat. No. 5,359,404 entitled “Laser-Based Speed Measuring Device, U.S. Pat. No. 5,652,651 entitled “Laser Range Finder Having Selectable Target Acquisition Characteristics and Range Measuring Precision”, and U.S. Pat. No. 6,057,910 entitled “Self-Calibrating Precision Timing Circuit and Method for Laser Range Finder”, which are each incorporated herein by reference. Typically, these laser speed detection systems provide accurate measures of a vehicle&#39;s speed and are useful for providing onsite speed measurements, e.g., at the location of a law enforcement vehicle, that could then be entered on a ticket by law enforcement personnel. 
   Improvements have been made to increase the accuracy and usefulness of these laser-based speed detection systems. For example, U.S. Pat. No. 5,938,717 entitled “Speed Detection and Image Capture System for Moving Vehicles”, which is incorporated herein by reference, discloses a system for accurately aligning a laser speed detector and for capturing an image of a speeding vehicle with a video camera. The system also provides the advantage of automating the capture of images of speeding vehicles at a predetermined distance from the system and of capturing a set of useful information (e.g., date, time, location, speed limit, detected speed, and the like). A computer system is included in the disclosed system to run a frame grabber program to capture a frame of the video image. The computer system includes a removable data storage device for storing the captured image frames and the associated set of information. 
   Generally, the system is taught to be operated by placing the system in a selected location to monitor vehicle speeds, such as along a road with the bulky computer system position in the back of a van or other vehicle. The system is initially set up by an operator and then allowed to operate automatically without or with minimal operator control for a certain period of time. An operator then removes the data storage device from the system and takes the data storage device back to a separate office or facility for processing of the captured images (i.e., grabbing a still image from the video) and data with a computer system at the office. In this manner, tickets can be produced by combining the video image with the collected data and then mailing the ticket to owners of vehicles that violated a speed limit by a selected amount (such as 5 miles per hour in a school zone and 10 miles per hour for a highway). A hardcopy of the image may be included with the ticket with the data being overlaid by the office computer system. In some applications, the field computer system, such as a personal computer, includes a monitor to allow an operator to view the collected image and to facilitate entering of field parameters. Additionally, the field computer system may perform some of the processing features (such as overlaying of the set of information on a grabbed frame of the video) and may include a thermal printer to produce copies of the image with the overlaid information at the field unit. 
   While addressing some of the needs of law enforcement agencies, the video-based laser speed detection systems have not addressed all of the operating problems facing field operators and are not particularly useful in some field applications. For example, the use of frame grabbing with a video camera for image capturing is most effective with-a relatively high capacity and higher speed data processing system and large data storage capacity. Typically, the computer requirements are met with a personal computer with central processing unit with a frame grabber PC card installed and associated monitor and keyboard. The combined use of a video camera with a personal computer results in a bulky package that is often costly and is usually physically large, which limits its usefulness in the field. It is not convenient or even practical for a single operator, i.e., law enforcement officer, to quickly deploy the system and then periodically move the entire system or portions of the system without moving the whole vehicle in which the system is positioned. The portability of these video-based systems is further limited by the need for a large number of communication cables and power cords (e.g., generally AC and DC power provided to each component) between the various components. 
   One of the most significant advantages of a laser-based speed measurement instrument is its ability to narrowly target a single car within a group of cars. However, there is still a need for proof that the detected speed is matched with the correct car. This proof can be provided with the overlaid information if it is accurately synchronized with the proper, grabbed video frame. Of course, this synchronization and combining of information requires additional processing capacity that increases the cost and sometimes the size of the system. Also, the time required to process the information and to print out a hard copy of the produced image limits its desirability as evidence or proof of speeding in the field as enforcement officers demand relatively quick evidential support to be used during the issuance of a speeding ticket. 
   Hence, there remains a need for a device or system for detecting a speed of a moving vehicle and for capturing an image of the vehicle that provides an accurate determination of the vehicle&#39;s speed along with readily accessible proof that the speed has been correctly matched to the proper vehicle. Preferably, such a speed measurement device would be designed for field use (such as inside or outside an operator&#39;s vehicle) providing prompt and useful evidence of a vehicle&#39;s speed while also being compact, lightweight, and easy to operate. The device would also preferably be useful in various weather conditions, provide protection of collected images and data, and be relatively inexpensive to purchase and operate. 
   SUMMARY OF THE INVENTION 
   The present invention addresses the above discussed and additional problems by providing a compact and portable speed measurement and image capture system that combines an accurate laser speed detector with a programmable digital camera and a portable field processor. The portable field processor is configured to allow an operator to enter capture session and system parameters, such as a posted speed limit and a capture speed level, and to receive vehicle speed signals from the speed detector. The portable field processor operates to selectively transmit image capture signals to the digital camera in response to these speed signals (e.g., generates image capture signals when the capture speed level is exceeded). The digital camera is programmed to retrieve a still image of the vehicle from its buffers or memory and create and transmit a digital image file (such as a file compressed per JPEG standards). The portable field processor then writes the speed signal data into the digital image file and displays the combined file on a display screen. The portable field processor can then be detached from the system by a field operator to show the displayed image to a vehicle operator. In one embodiment, a classification sensor is provided to detect whether the vehicle is a commercial vehicle, such as by height measurements, axle counting, weight measurements, and the like, and two distinct capture speed levels are used to effectively capture images of private and commercial speeding vehicles that may have different speed limits. 
   According to one aspect of the invention, a compact speed measurement system is provided for field or onsite use in measuring speeds of vehicles and capturing images of select vehicles. The system includes a laser-based speed detector for determining a speed of a vehicle in a specific target area. When a speed is determined, the detector generates a speed signal. The system also includes a camera generally aligned with the speed detector operable to capture and store digital-format still images of vehicles in memory. Specifically, the camera is programmed to respond to an image capture signal to generate and transmit a digital image file including a still image of the vehicle targeted by the detector. A portable field processor is communicatively linked to the speed detector and the camera to first receive the speed signal, to process the speed signal and in response transmit an image capture signal to the camera, and to receive the digital image file from the camera. 
   In a preferred embodiment, the portable field processor includes software to create a combined speed and image data file by modifying the digital image file to include speed data from the speed signal. For example, the digital image file may be a JPEG-format file and the modifying may involve writing the speed data to the header of the JPEG file. The portable field processor includes a display screen and is configured to display the modified digital image file on the display screen. An operator can then operate the field processor to enlarge and/or enhance selected portions of the displayed image (such as to enlarge the license plate portion of the image). The field processor can be readily detached from the system and hand carried to a stopped vehicle to show the vehicle operator the displayed image as proof of their speed. To control the risk of data loss, the system is configured such that the digital camera acts as a charging power source for the field processor, i.e., the camera will stop operating before the field processor loses power thus assuring storage of all captured images. 
   According to another aspect of the invention, a method is provided for measuring a speed of a moving vehicle and capturing a digital image of the same moving vehicle. The method involves initially positioning and setting up a speed detector and a camera at a location selected by an operator for targeting vehicles moving through a target area. The camera is operated on an ongoing basis to capture or temporarily store a still image of each vehicle passing through the target area. The speed detector operates on an ongoing basis to determine the speed of a specific vehicle in the target area. The speed data including the determined speed is transmitted to a portable field processor. The speed data is processed by the field processor, which responds by transmitting a trigger signal to the camera. The camera receives the trigger signal, responds by retrieving a still image corresponding to the targeted vehicle, and then transmits the still image in a digital image file to the portable field processor. 
   In one embodiment of the method, several of the functions are synchronized to insure that the captured image is an image of the same moving vehicle that was targeted by the speed detector. This is achieved by determining the speed at a speed measurement time with the detector and operating the camera to store still images during an image timing cycle. Synchronization occurs by operating the field processor to transmit the trigger signal within the timing cycle that also coincides with the speed measurement time. 
   In another embodiment of the method, the method includes determining the classification of the vehicle, such as with a separate classification sensor (e.g., a height sensor). The classifications may include private or lower weight vehicles, commercial trucks or higher weight vehicles, and other classifications that may be used by governments in establishing differing speed limits (e.g., 55 mph for commercial vehicles and 65 mph for private vehicles). In this embodiment, the processing of the speed data includes first identifying the classification of the vehicle (such as from the combined speed data string including vehicle speed, range of vehicle from speed detector, and the vehicle type) and then comparing the detected speed with the speed limit for that type of vehicle. Vehicle classification in the method may be achieved in many ways. For example, vehicle classification may include sending a signal directly to the field processor from a separate sensor configured to detect vehicle type or classification may include concatenating vehicle type information onto the laser speed detector data string. 
   In another embodiment of the invention, a stop sign enforcement system is provided in which the portable field processor is configured for traffic sign or signal enforcement, e.g., compliance with stop signs. The portable field processor may include a stop sign or traffic signal software module or otherwise be configured, such as by proper entry of operating parameters for its base operating software, to determine whether a vehicle complies with a traffic sign or signal. In this embodiment, the system includes a laser speed detector and a digital camera that are positioned with a line of sight to a traffic sign or signal, such as a stop sign, and a lane of a road adjacent the sign (i.e., where vehicles are supposed to stop for the sign). 
   The system may be positioned in front of or behind a traffic sign or signal so as to enforce the sign or signal with a front or rear view of vehicles relative to the signal or sign. The laser speed detector is ranged or used to measure the distance to the sign by aiming it at the back or front of the stop sign or traffic signal. Once the measurement distance is identified, the laser detector (with the aligned and combined camera) is aimed at a center portion of the road lane where enforcement is desired. The portable field processor includes a display for allowing an operator to configure the system for traffic signal enforcement, such as by selecting a stop sign enforcement operating mode (or an automatic capture mode), and to input an enforcement or measurement window (i.e., an area relative to the traffic signal or sign) and/or a capture speed threshold. 
   The threshold is typically set in the range of 10 to 20 mph (at which point it is unlikely that a vehicle would be able to stop at the sign) or set as percentage of the posted speed limit (such as 50 to 100 percent of the limit of the road lane, e.g., 30 mph in a 45 mph speed zone). The system is then allowed to operate for a period of time automatically capturing and storing vehicles that violate or “run” the stop sign or other traffic signal (such as a railroad crossing or traffic light). System operation includes the detector detecting a speed of a vehicle that enters the detector&#39;s enforcement window (e.g., detection typically begins a preset distance beyond (or in front of if detecting from behind the vehicle) the measurement distance, such as, but not limited to, 10 to 20 feet) and transmits a speed data signal to the portable field processor. The processor uses the stop sign enforcement module or internal programs with appropriately set parameters and configuration to compare the detected speed indicated in the signal to the threshold. When the threshold is exceeded, the processor transmits a trigger signal to the camera. The camera then retrieves a digital-format still image (of the same vehicle for which the speed was detected) and transmits this to the processor as a digital image file for combining with the speed data (such as in the image file header) and then later downloading for use in creating a traffic violation citation or ticket. In some embodiments, the image file and speed data are maintained as separate files that are linked or matched or that are later combined. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic block diagram illustrating an implementation of a speed measurement and image capture system according to the present invention. 
       FIG. 2  is an illustration of a display screen of the portable field processor of  FIG. 1  as it would be viewed by an operator of the processor and by a vehicle driver. 
       FIG. 3  is front perspective view of an embodiment of the speed measurement and image capture system of  FIG. 1  illustrating the compactness of the system as the entire system is mounted on a standard photographers tripod. 
       FIG. 4  is a rear perspective view of the system of  FIG. 1  similar to  FIG. 3  illustrating the operator&#39;s view of the system and showing the field processor housing for holding and viewing the portable field processor. 
       FIG. 5  is rear side view of the system of  FIGS. 3 and 4  illustrating the detachable mounting bracket and the communication and power ports or connections of the system components. 
       FIG. 6  is a flow diagram illustrating the acts and features of operating the speed measurement and image capture system to capture and process images and then display the images to a vehicle operator with a portable field processor. 
       FIG. 7  is a schematic block diagram illustrating another implementation of a speed measurement and image capture system according to the present invention that is configured more specifically for stop sign (or signal enforcement). 
       FIG. 8  is a flow diagram illustrating the acts and features of operating the speed measurement and image capture system of  FIG. 7  to capture and process images of vehicles determined by the system to be violating a stop sign or other sign or signal requiring a vehicle to stop at specific location. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates one embodiment of a speed measurement and image capture system  100  that is especially configured to be used in the field by law enforcement officers. In this regard, the system  100  includes components that can be combined into a compact and portable unit for ready mounting on a tripod or onto a bracket of a vehicle. Significantly, the system  100  also includes a portable field processor  110  that is designed to receive digital information (i.e., captured digital images and detected speeds and ranges), to process the information (such as by zooming in on a vehicle operator&#39;s face and/or a license plate on the vehicle), and to be detached from the system  100  to be carried over to the vehicle. The captured and processed image can then be easily displayed to the vehicle operator on a display screen  112  of the portable field processor  110 . These and other features, such as the use of a digital camera battery to trickle feed power to the portable field processor  110  to enhance data storage and security, will be discussed in detail below. An overview of the system  100  will first be provided followed by an in depth discussion of the individual components of the system  100  and their operation. 
   As illustrated, the speed measurement and image capture system  100  includes a portable field processor  110  in communication with both a laser speed detector  130  and a digital camera  140 . As will become clear, the laser speed detector  130  is utilized by the portable field processor  110  to obtain a speed of a moving vehicle  134  and the vehicle&#39;s range or distance from the detector  130 . Concurrently, the digital camera  140  is operated by the portable field processor  110  to capture an image of the front portion of the vehicle  134 . During operation, the digital image is combined with the detected speed and range information by the portable field processor  110  for use in proving that a vehicle was going the detected speed (e.g., violating a posted speed limit). 
   The laser speed detector  130  may be any of a number of laser-based speed and range detection devices that are useful for determining speed and range of a vehicle or other object from the detector  130  at the time the determination was made. Additionally, the detector  130  preferably is configured to provide the determined speed and range information over a communication link to the input/output port  122  of the portable field processor  110  (e.g., in digital form). In one preferred embodiment, the laser speed detector  130  is a laser-based sensor device such as that available from Laser Technology, Inc., Englewood, Colo. under the product name of UltraLyte, which operates effectively to determine the speed and range measurement data and to download the data to the portable field processor  110  (e.g., at a baud rate of 9600 or higher). As shown, the portable field processor  110  includes memory  120  for storing the speed and range measurement data from the laser speed detector  130 . 
   The digital camera  140  is a significant feature of the system  100  providing the key functions of capturing and delivering a digital image when prompted by the portable field processor  110  and of acting as the charging power supply for the portable field processor  110 . The digital camera  140  is preferably fully programmable and is selected to create a digital still image on demand and to download the image (e.g., a compressed digital file such as JPEG file) to the portable field processor  110 , which can append the speed and range information to the digital image file such as in the JPEG file header. 
   The digital camera  140  is included to provide the proof that the correct vehicle  134  has been targeted by the laser speed detector  130  by taking or capturing a digital image of the vehicle  134  as the speed is substantially concurrently (i.e., within an acceptable time window, as discussed below) being determined by the detector  130 . In other words, the operation of the digital camera  140  and laser speed detector  130  are synchronized by the portable field processor  110 . The digital camera  140  includes a lens  142  which is selected such that the camera  140  can capture vehicle images which can be resolved to accurately show the vehicle license plate (and in some embodiments, the vehicle operator&#39;s face). The digital camera  140  has a range or field of resolution that preferably coincides with, or is larger than, the target area of the laser speed detector  130  (e.g., a range of 0 to 125 meters or more). The digital camera  140  is powered by an integral battery  144 , which is also used to provide power to the portable field processor  110  via power supply port  124  as is discussed in detail below. 
   As with the laser speed detector  130 , the digital camera  140  may take many forms and configurations to provide the features and operational advantages of the present invention. In one embodiment, the digital camera is a high-speed Ethernet camera (such as those available from JVC under Model No. VN-C1U) that is interfaced with the portable field processor  110  with a network card (such as a Compact Flash network card) in the input/output  122  of the processor  110 . This type of digital camera is desirable for the camera  140  because it has a high data transfer speed and is programmable but many other digital cameras may be employed in the invention. In one preferred embodiment, the camera  140  is operated in a mode to automatically compress captured images into a JPEG format which reduces the file size of the images prior to them being transferred to the portable field processor  110 . The initial setup (e.g., parameter setup) and image capture request communication from the portable field processor  110  to the camera  140  is typically performed via an Ethernet connection (e.g., a 10Base-T Ethernet LAN) with UDP or other protocol to provide a connection rate useful for rapidly downloading the digital images from the camera  140  to the processor  110 . 
   The camera  140  preferably is able to operate in an automatic mode and in a manual mode. In the automatic mode, the camera  140  automatically adjusts the exposure, gain, brightness, and other operating parameters to provide a high quality image. In manual mode, the camera  140  can be adjusted by an operator or by the processor  110  to set a number of operating parameters. For example, the following parameters may be set (with one preferred setting provided in parentheses): image resolution (640×480 pixels); JPEG compression (low or best resolution for camera  140 ); exposure ( 1/1000 second); gain (minimum=150, average setting=200, and maximum=255); frame rate (maximum for camera  140  such as 30 frames/second); contrast (default of camera  140 ); brightness (median setting for camera  140 ); and sharpness (default of camera  140 ). Other operating parameters and settings will be apparent to those skilled in the art to obtain a clear enough image to identify a license plate and/or vehicle operator. 
   In this regard, a number of lens systems  142  may be utilized to obtain a desirable captured image, such as a lens system with a 225-millimeter focal length. In a preferred embodiment, the lens system  142  provides a full field-of-view of 1.5 degrees and is focused at 80 meters to obtain sharp images from 50 to 120 meters. Of course, the focus distance is preferably matched to the target field capacity and setting of the laser speed detector  130 . In practice, the only camera  140  adjustment that is manually performed in the field is adjustment of the aperture. Other operating parameters, such as gain, are set by an operator of the system  100  via the portable field processor  110  by entering information in a capture setup screen (discussed in more detail below). 
   According to one important feature of the invention, the system  100  is configured such that the digital camera  140  functions as a charging power source for the portable field processor  110 . This arrangement enables the processor  110  to be fully charged even when the digital camera  140  does not have enough power to continue to operate (i.e., when its battery  144  is depleted) which provides an added level of data protection for previously captured images and speed and range information with data loss being unlikely. This charging feature may be carried out in a number of ways, and the following embodiment is exemplary only and not limiting of the breadth of the invention. 
   In one embodiment, the camera  144  includes a battery  144  that provides the needed input power for operating the camera  140 . For example, the battery  144  may be a readily available 7.2 VDC rechargeable lithium ion battery or other type and rating battery that can be mounted to the camera  140 . In some embodiments, the camera  140  operates at a different power level than provided by the battery  144  (or desired by processor  110 ) and a step-down regulation board (not shown) is mounted between the camera  140  and the battery  144  (e.g., the camera  140  may require 5 VDC input power and the step-down regulation board would be configured to step down the 7.2 VDC to 5 VDC). Further, a switch (not shown) may be provided to break the connection between the battery  144  and the regulation board. 
   To provide a trickle charge to the processor  110 , the stepped-down voltage may be provided to the processor battery system  126 . As illustrated, the battery  144  is connected directly to the power supply port  124  that feeds the charging power to the battery system  126  of the processor  110 . A step-down regulator (not shown) may be provided in the processor  110 . Alternatively, the stepped-down power from the regulation board (not shown) in the camera  140  can be fed through the communication line to the input/output port  122  of the processor  110 . For example, the processor  110  power supply wiring may be included in the Ethernet communication wiring from the camera  110  with the stepped-down power (such as 5 VDC) being brought into the processor  110  through the input/output port  122  (e.g., a serial connector port). 
   Turning now to the portable field processor  110 , the system  100  is uniquely configured such that the speed of the vehicle  134  can be accurately determined and an image captured with the detector  130  and camera  140 . This data is downloaded to the portable field processor  110 , which can be removed or detached from the system  100  and easily carried over to the vehicle  134  by a system operator to display the captured image with the determined speed to the vehicle operator. To achieve these and other functions, the processor  110  includes an input/output port  122  for communicating with the detector  130  and camera  140 . The port  122  (e.g., an RJ45 socket) may be configured with a Compact Flash network card, such as those available from Socket (e.g., a Socket, part number EA2902-139 Ethernet card), that in one embodiment is an Ethernet card selected to provide 10BaseT communications with the camera  140 . Preferably, the communication cable from the port  122  is ruggedized such that there is no connector to reduce the chance of a communication malfunction during field operations. Of course, the cable connections discussed and illustrated may be replaced with infrared (IR) links between the processor  110  and one or both of the camera  140  and the detector  130 . 
   The processor  110  is preferably a small, handheld computer device or palmtop computer that provides portability and is adapted for easy mounting (as discussed with reference to  FIGS. 3 and 4 ). For example, any of a number of personal digital assistants (PDAs) may be utilized for the processor  110 . As illustrated, the portable field processor  110  includes a display and input/output screen  112  for use by the operator in displaying an image and speed and range information to an operator of the vehicle  134 . 
     FIG. 2  illustrates one embodiment  200  of a screen shot displayed on the display  112 . The captured image includes an image of the vehicle  134  and in this embodiment, the captured image has been processed by the processor  110  to zoom in or enlarge the portion of the captured image that shows the license plate  204  of the vehicle  134 . The collected speed and range data and other operator-entered data (e.g., capture session parameters) are shown in an information section  208  of the screen  112  to provide quick verification that the speed determined has been matched to the correct vehicle  134 . 
   Operation of the processor  110  to process the captured image is discussed below with reference to  FIG. 6 , and preferably includes the ability to select portions of the captured image received from the camera  140  for modification (e.g., to show clearly the license plate  204  and/or the face of the vehicle operator). While many screen or display technologies may be employed, one embodiment uses a reflective TFT screen that uses sunlight for illumination to enhance outdoor performance. The display  112  is used during operation to enter data (such as camera operating parameters and capture session parameters) and may use stylus, touch screen, and keyboard functions commonly available with PDAs for entering and manipulating data (e.g., selecting items in menus). 
   The processor  110  includes a central processing unit (CPU)  114 , such as a 71 MHz MIPS R4000 or a 206 MHz Intel Strongarm 32-bit RISC processor, to perform the logic, computational, and decision-making functions of the field processor  110  including interpreting and executing instructions. Memory  120  is provided for use during software execution and for storing digital image files from the camera  140 , speed and range information from the detector  130 , and capture session parameters entered by an operator. In one embodiment, memory  120  comprises 24 or more MB memory with 8 MB for program execution and the remaining 16 MB for data storage. An operating system  116  is provided to manage the basic operations of the field processor  110  and in a preferred embodiment is the Windows™ CE 3.0 or newer operating system available from Microsoft, Inc., Bellevue, Wash. that is configured to support UDP protocol for communicating with the detector  130  and camera  140 . 
   A system coordinator  118 , e.g., operating software, is provided to coordinate the activities of the system  100 . The system coordinator  118  preferably is configured to allow an operator of the processor  110  to set and modify system operating parameters, to browse previously captured images, and to capture new images of vehicles  134 . Numerous programming languages may be utilized, and in one embodiment, the system coordinator  118  is written in Visual C++ and compiled for the MIPS or StrongArm processor  114  and the specific operating system  116  (e.g., Windows™ CE). 
   As noted earlier, the combination of a digital camera  140  and a laser speed detector  130  with digital data output significantly simplifies the act of combining the speed and range data (and capture session data input by an operator) with the digital image file from the camera  140 . This is a large improvement over prior art devices that utilized video-based image capture and then employed a processing hungry and/or time consuming and complex series of steps to overlay the digital information over a captured frame of the video image of a vehicle. Additionally, synchronization of the operation of the detector  130  and camera  140  is simplified by the inclusion of digital photography technology in the system  100 . Synchronization is important to accurately match captured images with determined speed and range data. 
   In one embodiment, the system coordinator  118  achieves the combination of the speed data with the image by inserting the speed and range data into the digital image file header. Alternatively, the combination of data may be completed by and at the digital camera  140 . In this embodiment, the laser speed detector  130  is communicatively linked to the camera  140  to receive operating instructions (e.g., range-gate information) from the processor  110  as well as for passing the determined data to the processor  110  via camera  140 . 
   In addition to the speed and range data, a number of other operating parameters and capture session data (such as that illustrated in the screen portion  208 ) may be inserted in the image file header when the image file is processed and then stored in the memory  120  by the system coordinator  118 . In one embodiment, the following information is stored in the image file header: (a) date (which is preferably automatically updated by the processor  110 ); (b) time (preferably updated automatically by the processor  110 ); (c) operator name (entered by system  100  operator using a setup screen on display  112 ); (d) operator ID; (e) capture location (entered by operator using setup screen indicating location for monitoring vehicles  134 ); (f) determined speed (provided by the detector  130 ); (g) distance (provided by the detector  130 ); (h) speed limit (entered by operator using setup screen); X and Y crosshair positions (automatically entered during the alignment process to show detection point of detector  130 ); and camera ID (entered by operator and may include camera  140  serial number). 
   The systems coordinator  118  preferably allows the operator to set different modes of operation of the system  100  to selectively store chosen images. In one mode of operation, the operator may select “all” which indicates that during a capture session all speed data for vehicles determined to being going equal to or above the captured speed are stored in a log file in memory  120  for statistical or other uses. The “all” setting may be useful for automated and non-monitored operation of the system  100  (such as setting up the system  100  at a location for a period of time to monitor general traffic patterns and then retrieving the system  100  or the memory  120  at a later time) 
   To reduce the number of image files (with added header information) stored in memory  120 , the operator may enter capture parameters such as a capture level that indicates the amount over the entered speed limit that should be captured. For example, the capture level may be set at 0 mph, and all vehicles  134  determined to be moving at a speed above the entered speed limit are captured. More preferably, a capture level such as 5 or 10 mph is entered to reduce the number of image files captured, processed, and stored in the processor  110  but yet to capture the vehicles  134  that are exceeding the entered speed limit by a level that indicates a citation or ticket should be issued. This mode of operation is suitable for both unmonitored operation and for monitored operation (i.e., in which an operator monitors operation with the capability of stopping a capture session to process and display an image to a particular vehicle operator). 
   Referring again to  FIG. 1 , the system  100  may include a field printer  150  to allow the processor  110  to transmit an image print file to the printer  150  to print screen images or other files in the field. For example, a thermal printer can be connected to the serial port of the processor  110  (or to the field processor housing  310 , discussed below). Additionally, the system  100  may include a base station  160  in communication via link  156  (a wired or wireless link that may include a direct connection such as by taking the processor  110  to a home office containing the base station  160  or a communications network such as the Internet) to the portable field processor  110 . The base station  160  may include one or more computer systems configured with software and processing components to enable the base station  160  to access and process the image files in memory  120  (or alternatively, the memory  120  may be removed and taken to the base station  160 ). This enables an operator of the base station  160  to browse the image files or to sort the files based on capture sessions and/or speeds (or speed to speed limit differentials) for creation of citations or tickets. 
   According to a preferred embodiment of the invention, the base station  160  includes software and processing capacity to be able to process the digital image files to enhance the images to improve clarity without modifying the original files. New screen images are created that may include enlarging selected portions of the image (such as the license plate area or operator area of the vehicle  134 ) and changing the contrast of the image to provide a higher quality picture of the vehicle  134 . The base station  160  can then print the enhanced or unenhanced image with all or select portions of the embedded text using any suitable printer. 
   According to another feature of the illustrated system  100 , a vehicle classification sensor  170  is provided that is configured to discriminate between different classifications of vehicles. In many situations, governments enforce two or more different speed limits. For example, in the United States, a 65 miles per hour (mph) speed limit may be enforced for vehicles under a certain height, weight, or axle number (typically, called private vehicles) while in the same location, a 55 mph speed limit is enforced for vehicles over a certain height, weight, or axle number (typically, called commercial vehicles). In these locations, it is useful to first differentiate or classify the vehicles into the classifications used to set and enforce the differing speed limits and then to only capture those that are meeting or exceeding the speed limit (e.g., capture level). Without this ability, the vehicles violating the lower speed limit are typically not captured or a large amount of manual processing is used to eliminate all the vehicles not speeding when the lower speed limit is used as the capture level. 
   Referring to  FIG. 1 , the system  100  is shown to include a vehicle classification sensor  170  configured for sensing a characteristic of the vehicle, such as height, weight, axle number, and the like. The sensor  170  may be configured to transmit a signal providing this characteristic data to the input/output  122  of the portable field processor  110  (automatically or upon request from the processor  110 ). In a preferred embodiment, the vehicle classification sensor  170  is configured to determine the classification of the vehicle and to then transmit the vehicle type information to the portable field processor  110 . This vehicle classification signal may be sent directly or the information may be concatenated with the laser speed detector  130  speed data (e.g., the combined data string may include vehicle speed, vehicle range from detector  130 , and vehicle type). 
   While many vehicle sensor configurations may be utilized to practice this feature of the invention, the illustrated sensor  170  is useful for sensing the height, H VEHICLE , of the vehicle  134 . In this regard, the sensor  170  typically is mounted and aligned within the system  100  to sense when a vehicle  134  is at or above a height limit, such as 6 to 9 feet (i.e., whatever vehicle height is used by the government for setting the lower speed limit). 
   The portable field processor  110  then processes the vehicle type information along with the vehicle speed data to determine if an image should be captured. For example, the portable field processor  110  may be configured to first identify the vehicle type or classification and then retrieve from memory  120  a vehicle speed limit for the classification. In a more preferred embodiment, the operator of the portable field processor  110  inputs capture levels for each possible vehicle classification. In this embodiment, once the processor  110  identifies the vehicle classification from the signal from the sensor  170 , the processor  110  compares the received vehicle speed with the appropriate capture level to determine if an image should be captured. In this manner, the system  100  enables effective and accurate vehicle classification and capture of speeding vehicle images in locations having more than one enforced speed limit. 
   According to another useful aspect of the system  100 , the portable field processor  110  may be configured to transmit wireless signals to remote field locations to enhance speed enforcement. In practice, the portable field processor  110  and the digital camera  140 , and the detector  130  may be positioned to capture images of speeding vehicles at a first location on a road while the enforcing officer may be positioned at a second location remote from the processor  110 , such as 100 to 200 meters or further down the road from the processor  110 . With this positioning, the enforcement officer can be informed with a signal from the processor  110  of an approaching speeding vehicle  134  and more importantly, be provided with the combined vehicle speed data and image file for use in stopping and ticketing the vehicle  134 . 
   In this regard, the portable field processor  110  is shown in  FIG. 1  to include a wireless output  174  for transmitting a wireless signal  176  to a remote field receiver  180 . As discussed above, the wireless signal  176  preferably includes the combined speed data and image file (explained in detail previously). The remote field receiver  180  may be any wireless device configured for receiving a wireless signal, and in one embodiment, is a device similar to the portable field processor  110  that is useful for processing and displaying the captured image and speed data to an operator of a vehicle  134 . A thermal printer may also be used at the remote location to print out hard copies of the image and speed data. A number of well-known wireless network devices and technologies can be utilized for the wireless output  174 . Similarly, a number of digital wireless protocols may be used, such as CDMA, GSM, iDEN, CDPD, and Bluetooth. 
   Referring now to  FIGS. 3–5 , one embodiment of the speed measurement and image capture system  100  is illustrated that clearly shows the compact and portable nature of the system  100  that is achieved, at least in part, through the combined use of the digital camera  140  and the portable field processor  110 . As shown, the system  100  can readily be mounted on and supported by a standard tripod  330  (such as a photographer&#39;s tripod). Due to the lightweight and compact characteristics of the system  100 , the system  100  alternatively can be simply hand-held by an operator, be mounted on a number of stand arrangements besides the illustrated tripod  330 , or be mounted directly to a vehicle with the use of a receiving bracket (not shown) attached to the vehicle. 
   As shown in  FIGS. 3–5 , the system  100  is mounted to the tripod  330  utilizing system mounting bracket  320  in a manner that balances the system components to enhance stability. Additionally, the mounting bracket  320  includes a quick release plate  322  that is configured to engage the tripod  330  such that the plate  322  can be mounted rapidly and optionally fastened to the tripod  330  to lock the plate  322  in position. In the illustrated embodiment, the plate  322  is configured to slide into grooves in the tripod  330  and fasteners can be inserted through holes in the plate  322  to rigidly attach the bracket  320  to the tripod  330 . 
   To distribute the weight of components and enhance stability, the illustrated bracket  320  is adapted to facilitate mounting of the detector  130 , the digital camera  140 , and the field processor  110  (along with any protective housing  310 ) on the tripod  330  (or other support structure) such that the mounted system  100  is stable. Further, it is preferable that the mounted system  100  remain relatively stable with or without the field processor  110 , as a key feature of the invention is being able to remove the field processor from the system  100 . Many alternative arrangements can be envisioned for maintaining a stable mounting of the system  100  on a bracket  320 , and these alternative mounting arrangements are considered within the breadth of this disclosure. 
   In the illustrated embodiment, the bracket  320  is configured such that the typically heavier detector  130  is mounted substantially above the quick release plate  322 . This enhances the stability of the mounted system  100  by placing the heaviest component on or substantially on a central axis of the tripod  330  (or on an axis passing through the center of gravity of the tripod  330 ). The digital camera  140  is then mounted on the bracket  320  adjacent a first side of the detector  130  and a field processor housing  310  for housing the processor  110  is mounted on the bracket  320  adjacent a second side of the detector  130 . This configuration provides weighted stability for the mounted system  100  with the processor  110  positioned within or removed from the housing  310 . 
   Additionally, mounting the camera  140  to the same bracket  320  as the detector  130  facilitates mechanical alignment of the two components such that captured vehicle images more readily correspond to the vehicles  134  for which speed is detected. When the camera  140  is attached to the bracket  320  (or the portion or arm of the bracket  320  that is supporting the detector  130 ), the camera  140  can be adjusted vertically and horizontally to be substantially parallel with the sighting device of the detector  130 . Alignment can be achieved by first sighting the detector  130  on a stationary object and then second sighting the camera  140  on the same object (or in opposite order). Once mechanically aligned, the two devices  130  and  140  are preferably locked in place, such as with fasteners, such that alignment is only required upon initial set up. Final alignment (or refined camera targeting) of the camera  140  is preferably achieved with the systems coordinator  118  of the processor  110  which can operate to position digital image crosshairs onto a specific feature of a sighted object. The crosshairs indicate the detection location of the detector  130  on an image captured by the camera  140 . 
   As discussed with reference to  FIG. 1 , the detector  130  and camera  140  communicate with the portable field processor  110 . As shown, the detector  130  includes a communication port  520  and the camera  140  includes a communication port  530  (although in some applications IR links may be utilized). Standard communication cables (not shown) are then used to connect the detector  130  and camera  140  to the communication port  502  (illustrated as a serial port) of the field processor housing or enclosure  310 . The portable field processor  110  (not shown in  FIGS. 3–5 ) is positioned or plugged into the base  312  of the housing  310  to provide for communication with the detector  130  and camera  140  (as discussed with reference to  FIG. 1 ). A protective cover  314  is provided that can be open, such as with hinges, to allow access to the interior portion of the base  312  for insertion and removal of the processor  110  during operation of the system  100 . In this manner, the processor  110  is protectively housed in the housing  310  with docking for communication with the detector  130  and camera  140  but yet can readily be detached or unplugged from the housing  310 . 
   The protective cover  314  includes a viewing window  318  to allow the cover  314  to be closed to protect the processor  110  from weather and dust during field use of the system  100 . To enter data, the cover  314  is typically opened to provide access to the display  112  of the processor, and for use with many processor  110  configurations a stylus holder  316  is provided on the side of the base  312  to hold the stylus-type data input tools provided with palmtop computers and PDAs. An optional cover locking knob  514  is provided to lock the cover  314  in the closed position. 
   Preferably, the camera  140  also provides charging power to the processor  110 . As illustrated, the camera  140  includes a power outlet port  534  which is connected with a cord (not shown) to the power supply port  124  of the housing  310  and processor  110 . In another preferred embodiment, the trickle charging power is provided over the communication cable and fed into the processor  110  over a standard communication port (e.g., serial port  502 ). In this embodiment, only one cable is needed to transfer data (i.e., digital image files and parameter data) between the camera  140  and the housing  310  and to transfer power from the camera  140  to the housing  310 . The single cable would connect the communication port  530  of the camera  140  to the communication port  502  of the housing  310  (which in turn, is connected to the communication port, typically a serial port, of the processor  110  when the processor  110  is docked within the housing  310 ). Also, as discussed with reference to  FIG. 1 , in some embodiments a short communication cable (not shown) is used to communicatively link the detector  130  to the camera  140  to reduce the length of cabling required. In this embodiment, the processor  110  exchanges data with the detector  130  through the camera  140  communication cable and port  530 . 
   Referring now to  FIG. 6 , operation of the speed measurement and image capture system  100  will be discussed to provide a further understanding of the unique features of the invention. At  610 , the operation process  600  is started with initial set up of the portable system  100 . Initial set up may involve numerous steps such as the mounting of the system  100  on the bracket  320  and/or tripod  330 , but generally involves selecting a capture session location in which to monitor vehicle traffic (such as adjacent a road within the system&#39;s targeting area and with the sun striking the rear of the detector  130  and camera  140  to control glare and to better illuminate license plates) and setting up, connecting, and powering up the components of the system  100 . A portion of a road may be targeted and vehicles automatically targeted and/or captured as they cross into the capture area or target line or alternatively, an operator may target manually specific vehicles by changing the position of the system  100  (e.g., turning the system  100  on the tripod  330 ). 
   At  614 , the operator is requested via a menu or other data entry device on the display screen  112  of the processor  110  to select an operating mode. A number of operating modes may be included for operation of the system  100  such as a browse mode that allows the operator to view previously captured images and a system mode that allows the operator to enter or modify system settings (such as adjusting the camera  140  settings, the detector  130  settings, the images to be logged or stored (such as only vehicles above a capture limit indicating speeding) and the like). If these modes are selected, once the operator is finished entering information or viewing (and processing and printing) images, the process  600  ends at  618 . To capture new vehicle images and speeds, the operator at  614  selects capture mode (or continue previous capture mode) and at  618  the process  600  is continued. 
   At  622 , the operator is requested via a data entry screen on the display  112  to enter capture session information or parameters. A portion or all of these parameters will then be inserted by the system coordinator  118  into the captured image file (such as in the header of a JPEG file) for inclusion in the captured image files stored in memory  120  and/or shown to vehicle operators. A wide variety of parameters may be included but in one embodiment, the parameters include an operator name, an operator ID, a capture session location, the posted speed limit for the location, the capture level or capture speed limit (i.e., a speed value for which the system  100  will capture an image when the determined speed by the detector  130  is greater than or equal to the speed value), weather conditions (which in some embodiments is used by the system coordinator to automatically determining camera  140  settings such as camera gain), and the camera  140  serial or identification number. 
   At  626 , the capture session is begun. The system  100  is either positioned to automatically detect vehicles  134  that enter a target area or the operator of the system  100  may move the system  100  to target particular vehicles  134  (such as by turning the upper portion of the tripod  330 ). When a targeted vehicle&#39;s speed and distance from the detector  130  are determined by the detector  130 , this information is transmitted to the processor  110  (e.g., via a communication connection such as RS232). The system coordinator  118  compares the determined vehicle&#39;s speed with the entered capture level or capture speed limit for the capture session. If the determined speed is less than the capture speed limit, no image is taken, i.e., the camera  140  is not operated to capture an image (unless all images and speeds are being logged for monitoring traffic patterns). If the determined speed is equal to or greater than the capture speed limit, the system coordinator  118  of the processor  110  transmits an operational signal to the camera  140  to trigger the camera  140  to capture an image of the vehicle  134 . The camera  140  retrieves the current digital image file from its memory and downloads the digital image file (e.g., a JPEG file) via the Ethernet or other connection to the processor  110 . 
   The image capture step  626  may also include first classifying the vehicle  134  into classifications, such as private and commercial, used by a government agency for establishing two or more speed limits (e.g., capture levels). This classification is performed by the processor  110  or the vehicle classification sensor  170  based on detected information by the sensor  170  (such as vehicle being above a certain height, above a weight limit, or having more than a set number of axles). The processor  110  then acts to first retrieve or identify the classification of the vehicle and then compare the vehicle speed with the appropriate capture level. 
   Within the image capture process  626 , it is important to synchronize image capture by the camera  140  with detection of speed by the detector  130 . Typically, laser speed detectors  130  operate on a measurement cycle as measured from the start of individual laser shots or transmissions to the calculation of the speed and distance. A typical laser speed gun or device may have a measurement cycle of about 300 milliseconds to 400 milliseconds (with some devices having shorter and some longer cycles). The speed and distance data are transmitted to the processor  110  at the end of this measurement cycle. Hence, the time from the start of the measurement process to the export of the data is at least about 300 milliseconds and typically less than about 400 milliseconds. 
   To achieve synchronization, the digital camera  140  is preferably programmed such that the image is not taken for a time period greater than the shortest portion of the detector measurement cycle (i.e., about 300 milliseconds for the above illustrative examples). Also, a maximum latency time (i.e., time between triggering signal received at camera  140  and taking picture) is selected such that the detector  130  would most likely not have been aimed at a new target or automatically tracked on a new target vehicle. In one embodiment, a maximum latency time of 200 milliseconds is utilized, but it is understood by the inventors that smaller and larger latency times may be selected to provide acceptable synchronization of the camera  140  and detector  130 . In this embodiment, an image capture window is established that begins at about 300 milliseconds before the end of the measurement by the detector  130  and that ends at about 200 milliseconds after the trigger signal to the camera  140 . 
   With this image capture window established, the camera  140  is preferably programmed in combination with operation of the system coordinator  118  (which transmits the camera trigger signal) such that the camera timing cycle coincides with the image capture window to place an image frame containing the vehicle  134  for which speed was measured within the memory of the camera  140 . The camera timing cycle in one embodiment is approximately 200 milliseconds with the image frame being placed in memory as early as 100 milliseconds prior to the end of speed measurement by the detector  130  and as late as 100 milliseconds after the end of speed measurement. 
   This timing cycle is obtained by the systems coordinator  118  adding a time delay, such as 100 milliseconds, from the time the detector  130  completes and transmits the speed measurement to the processor  110 . Another phase of the timing cycle is established by the camera  140  which updates a compressed image into alternating buffers periodically, such as every 200 milliseconds. If the camera trigger signal is received just before the next update, the image would be 200 milliseconds old (or 100 milliseconds prior to the end of the speed measurement). Conversely, if the camera trigger signal is received as soon as the buffer is updated, the image is frozen immediately (or 100 milliseconds after the end of the speed measurement). Of course, those skilled in the art will understand that the camera timing cycle, the image capture window, the timing of the camera trigger signal, and the speed measurement cycles will vary with particular components chosen for the system  100  and with the programming and operating setting of each component. These variations are acceptable in practicing the invention as long as the image capture and speed determination events can be adequately synchronized such that the same vehicle is captured in an image file and is targeted for speed determination. 
   As discussed with reference to  FIG. 1 , a significant feature of image capture is the combination of the image file from the camera  140  with the speed and distance data from the detector  130  and other system and/or capture session parameters. Typically, the data combination is completed at the processor  110  by the system coordinator  118  which functions to write or insert the speed and distance information into the header of the image file (e.g., JPEG-formatted file). The system coordinator  118  also writes select portions of the system parameters (such as time and date) and capture session parameters (such as location, speed limit, and operator ID) into the digital image file header. Generally, after the digital image file header is modified or the information is otherwise appended to the digital image file, the modified digital image file is displayed on the display  112  of the processor  110  for viewing by the operator. 
   In one preferred embodiment, the operator at  626  can operate the processor  110  to zoom in or enlarge select portions of the displayed image file. For example, the operator may select the license plate portion or the driver&#39;s side of the windshield to enlarge one of these portions of the displayed image. Various image enhancing tools may also be provided in the processor  110 , and if included, the operator can enhance the image by altering the displayed contrast, brightness, and other characteristics useful to make a clearer and sharper image. 
   In some applications, the system  100  is allowed to operate for a period of time automatically capturing images of vehicles (all or only those above the capture limit) and combining speed and distance image and select system parameters with the digital image files. These captured and modified digital image files are then stored in memory  120  for later viewing and processing. This later viewing and processing can occur in the field via the processor  110  and/or the optional field printer  150 . Alternatively, at  638 , the images stored in the memory  120  (i.e., capture session data) are downloaded from the processor  110  to a base station  160 . The downloading may be completed remotely over a communications network  156  or directly by interconnecting the processor  110  to a computer system within the base station  160  or by removing the memory  120  for use in the base station  160 . At the base station  160 , the combined image files can be sorted by determined speeds, by differentials between determined speeds and speed limits, by location, or by other information appended to the image file (e.g., inserted in the image file header). The images may also be processed to enhance picture quality and to enlarge select portions of the image. The electronic or hard copies of the processed images may then be used as part of a citation or ticket transmitted to the vehicle owner or operator. 
   Alternatively, according to a significant feature of the system  100 , the portable field processor  110  may be used by an operator to provide proof in the field that a vehicle was violating a posted speed limit. At  630 , the operator may interrupt an active capture session. For example, an operator may observe the displayed image on the display  112  of the processor  110  and when a speeder is displayed (above capture limit or by visual identification by the operator), the operator may stop the capture session to pull over the vehicle and issue a ticket. Alternatively, the system coordinator  118  may be adapted to provide an audio and/or visual alarm when a vehicle is detected to be driving at or above the capture limit and its image is captured. At this point, the operator detaches or unplugs the processor  110  from the housing  310  and carries the processor  110  to the stopped vehicle. The operator can display the captured image with combined data to the vehicle operator on the display  112 . 
   Alternatively, at  630 , the captured speed data and digital image may be transmitted to a receiver operated by a remotely positioned field operator (law enforcement officer). The field operator can then process the information with their equipment, such as another portable field processor  110 , and stop an approaching vehicle shown in the captured image. The field operator can then display the image to the operator of the vehicle  134  as described above. 
   The operator of the system  110  may process the captured image to enlarge the license plate or the driver&#39;s face and to enhance the clarity of the displayed image. When the operator has completed using the processor  110  to prove a vehicle&#39;s speed to a driver, the operator docks the processor  110 , located in the housing  310 , to its bracket. At  634 , a new capture session may be begun (returning to step  610 ) or the previous capture session can be resumed without having to reenter capture session parameters. After the session is completed, the capture session data can be downloaded to the base station at  638  for further processing. 
   In one embodiment, a data security process is performed by the system coordinator  118  prior to writing the combined data image file to memory  120  to ensure that the image and/or speed data is not altered between the time it is collected and the time it is used in a citation or as evidence. A number of security processes may be utilized to indicate whether a data file has been altered. For example, the system coordinator  118  may perform a check sum on the data with a seed number in the header of the combined speed data and digital image file, encrypt the check sum, and append the encryption into the header of the file. Then when a saved image file is opened, it is first verified as not being altered by removing the encrypted check sum and replacing the check sum with a seed number. The same type of check sum is run on the file and the new check sum is encrypted. The two encrypted check sums are then compared to determine if alteration has occurred. Of course, numerous other security processes may be utilized to reduce the risk of data modification but the exemplary method has proven effective and is detailed enough to detect an alteration as small as inverting speed digits (e.g., changing 75 mph to 57 mph). Note, in some embodiments, security is further enhanced by verifying with the processor  110  the check sum output directly by the laser speed detector  130  with an expected check sum value. 
   In addition to enforcement of speed limits, it is desirable to provide a system and method for identifying vehicles that violate traffic signs and signals, such as stop signs, traffic lights, and other postings or traffic devices that require a vehicle to come to a stop at a particular location. Such signals may vary based on the traffic laws of a country or locale, but in the United States, stop signs and traffic signals are typically placed at corners where one road intersects another road. To comply with the posted stop sign, an operator of a vehicle is required to come to a complete stop, i.e., a vehicle speed of 0 mph, for a period of time. Similarly, a traffic light when showing a red light requires a vehicle operator to stop their vehicle until the traffic light changes to show a green light. Other postings, traffic signs, or signals may likewise require a vehicle to stop at a particular location, such as certain railroad crossing signs or signals (e.g., at blind crossings) that require all vehicles to stop prior to crossing over the railroad tracks. 
   For these and other stop “signs” (e.g., the use of stop signs in this application is intended to include any and all devices used to cause a vehicle to stop such as printed stop signs, traffic lights, certain railroad crossing signage, and the like), it is desirable to be able to detect violations, i.e., vehicles that fail to stop, and to capture enough information to create a valid citation for the violation (such as an image of the front or rear of the vehicle with a license plate and/or an image of the vehicle driver) as discussed with reference to  FIGS. 1–6 . 
   In this regard,  FIG. 7  illustrates a stop sign (or traffic signal) enforcement system  700 . In the system  700 , many of the components of the system  100  of  FIG. 1  are included and provide similar functionality. For example, the laser speed detector  130  is utilized to detect a speed of a vehicle  134  located a distance from the detector  130  (such as a range distance, d RANGE ) as discussed with reference to  FIG. 1  and the camera  140  functions to capture an image of the vehicle  134  in response to a capture or trigger signal from the portable field processor  110 . 
   The portable field processor  110  is configured similarly as in the system  100  but further includes a stop sign enforcement module  710  (which may be integrated with system coordinator  118  or may be provided by configuring the system  700  and processor  110  and its software according to the following description) that typically includes the operating software, program, and/or routines used by the processor  110  in determining when a stop sign violation has occurred and in response, initiating an image capture or trigger signal by the system coordinator  118  to the digital camera  140 . As with the system  100 , the detector  130  and camera  140  are preferably synchronized such that an image captured by the camera  140  is of a vehicle  134  that is determined to be traveling at a detected speed (e.g., a speed over a capture speed threshold). 
   Because certain functionalities are not required for stop sign enforcement, some components of the system  100  may be left out of the system  700  (or if one unit is used and marketed for all functionalities of the invention, these components can be provided but not actively utilized during stop sign enforcement). For example, the wireless output  174  and remote field receiver  180  typically would not be required in the system  700  as the enforcement session data is typically downloaded to a base station  160  (but in some cases, the session data may be transmitted using a wireless output, such as device  174 , to the base station  160  such as when the processor  110  is relatively permanently positioned at a location for stop sign enforcement). The vehicle classification sensor  170  is not shown in system  700  as generally stop sign laws apply equally to all vehicle types (but may be included for stop signs that require commercial vehicles, including busses, to stop but not private vehicles, such as at some railroad crossings). Hence, the system  700  may be simplified in functionality and configuration compared to the system  100 . Generally, prior to operation, the system  700  is positioned within a vehicle, such as a van or other vehicle, or other support and protective enclosure (such as a shed or portable trailer) that is itself positioned nearby a particular stop sign within the effective range of the detector  130  and camera  140 . The system  700  may be positioned as shown in  FIG. 7  behind the stop sign  720  so as to capture a frontal image of the vehicle  134 , or alternatively, may be positioned in front (e.g., down the road on the side of the sign  720  displaying the print, symbols, or lights) of the stop sign  720  so as to capture an image of the rear portion of the vehicle  134 . 
   To fully explain operations of the system  700  and its unique features, it may be useful to describe the system  700  in conjunction with one exemplary operating procedure  800  shown in  FIG. 8 . The operating process  800  is started at  805  generally by providing the stop sign enforcement module  710  in the portable field processor  110  or otherwise providing the software in the system coordinator  118  (or elsewhere) to perform the processing functions described within the operating procedure  800 . At  810 , the portable system  700  including the processor  110 , the detector  130 , and camera  140  are set up in the field to detect stop sign violators (e.g., violators of traffic signals that require stopping a vehicle) and capture information for proving such violation of the posted signage. The initial set up, as with step  610  of process  600  in  FIG. 6 , may involve a number of steps such as the mounting of the system  700  on the bracket  320  and/or tripod  330  or other support structure and generally involves selecting an enforcement site or location at which to monitor vehicle traffic relative to a particular stop sign  720 . Again, although  FIG. 7  illustrates one location for the detector  130  and camera  142 , other locations may be utilized to practice the method  800  including, but not limited to, positioning the detector  130  and camera  140  in front of the sign  720  typically on the same side of the lane  724  as the sign to have a line of sight to the front of the sign  720  and the rear of vehicles  134  in the enforcement window  736  adjacent the sign  720  in the lane  724 . 
   Once an enforcement site is chosen, the system  700  is generally positioned adjacent a road (or lane  724  of a road) a particular distance, d RANGE , from the stop sign, such as along (e.g., down traffic or up traffic) the road with an unobstructed view of the back (or front) of the stop sign  720  and the lane  724  adjacent the stop sign  720 , i.e., where a vehicle  134  is required to stop for a period of time and labeled an enforcement or measurement window  736  in  FIG. 7 . The set up location for the portable field processor  110 , laser speed detector  130 , and camera  140  is determined by line of sight and distance considerations given optimum conditions associated with normal laser detector  130  and camera  140  usage. Typically, the distance or range, d RANGE , is dictated by the optimum range of the camera lens  142  to ensure clear and identifiable images for reading license plates in captured images and subsequent citation or ticket creation at  890 . 
   At  820 , the operator of the system  700  is requested via a menu or the like on the screen  112  (or other input point or feature) of the processor  110  to select an operating mode. The modes may include those discussed relative to process  600  and step  614  and, in the system  700 , further include a stop sign enforcement mode (or the “mode” may be implied by an operator configuring the system  700  according to the method  800  with no actual mode selection provided to an operator). The stop sign enforcement mode may coincide with a standard automatic mode for some units in which images are automatically captured along with speed detector data when a capture speed threshold (or capture level) is exceeded except that the stop sign threshold is typically set much lower than previously discussed capture levels or speeds, i.e., a set amount in excess of a posted speed limit. 
   At  830 , the system coordinator  118  determines whether the stop sign enforcement mode was selected in the menu or otherwise at  820  (or again, the “mode” may be implied by the settings selected by operator). If a different mode is selected, operation  800  continues at  840  with transfer of the process or operations by the system coordinator  118  to the process  600  and capture mode query  618 . If the stop sign enforcement mode is selected and identified at  830 , operation  800  of the system  700  is continued by operation of the coordinator  118  in conjunction with the stop sign enforcement module  710  of the portable field processor  110 . More particularly, the processor  110  is programmed for a particular enforcement window  736  and speed threshold. 
   At  850 , ranging is performed for the system  700  for the particular enforcement site, which may be behind the sign  720  as shown in  FIG. 7  or in front of the sign  720 , which dictates the positioning of the detector  130  and camera  140  relative to a stop sign  720 . The ranging distance, d RANGE , is generally measured from the stop sign  720 , such as the back side (or front side) of the stop sign, to the laser speed detector  130  and/or the lens  142  of the camera  140 . Ranging at  850  is performed by aiming the laser speed detector  130  at the back (or front) of the stop sign  720  (or to a post or other portion of the sign or signal) being monitored by the system  700 . The laser speed detector  130  preferably can then be set to detect speeds of vehicles  134  with this determined distance, d RANGE , from the detector  130  and to display this distance, d RANGE , for entering into the processor  110  as an enforcement parameter at  860  (e.g., programmed into the processor  110  as the measurement distance for downloading to the base station  160 ). The space or area adjacent the stop sign  720  in the lane  724  can be thought of or labeled the enforcement window or range  736  that is adjacent and generally behind the sign  720  and is the point or area where a vehicle  134  will violate stop sign laws (or where an infraction will occur). 
   Typically, the laser speed detector  130  is operable for a window or set of distances beyond the measurement distance, d RANGE , and will operate effectively for measuring speeds within this measurement, capture, or enforcement window  736 . For example, the detector  130  may be configured to have a 10-foot or larger (or smaller) window  736  such that if the measurement or ranging distance, d RANGE , was determined to be 60 feet the laser speed detector  130  would target vehicles  134  that are 60 to 70 feet from the detector  130  and ignore all targets or vehicles  134  outside this measurement or capture window  736 . This enables the detector  130  to measure the speed of a single target (as 2 vehicles typically will not fit within a single 10-foot enforcement window  736 ) within the enforcement area in the lane  724  in front of the sign  720 . As discussed previously with respect to system  100 , preferably the camera  140  is selected to have a range that coincides with the enforcement distance, d RANGE , and more particularly, the lens  142  is automatically or manually adjusted to focus at a distance corresponding to the enforcement distance, d RANGE , or within the corresponding enforcement window  736  adjacent and in front of the sign  720  in the lane  724 . Note, the enforcement distances and sizes of the window  736  may be varied in practicing the invention with the examples above provided for illustration purposes and not as limitations to the invention. 
   At  860 , the operator of the system  700  is requested via a data entry screen  112  to enter stop sign enforcement session parameters including a capture speed threshold. The parameters may vary but will typically include information useful for inclusion in the captured image file (such as in the header of a JPEG file and, for example, see information portion  208  of display  200  in  FIG. 2 ) and/or for use in preparing or supporting a ticket or citation prepared based on a detected stop sign violation. This information may include operator name, an operator ID, an enforcement site and stop sign location, the type of sign being monitored, weather conditions (which may effect camera  140  settings/operation), the camera  140  and/or detector  130  identifiers, and, significantly, the capture or enforcement speed threshold (or capture level). 
   Also, at  860 , the system  700  is set to automatically capture (i.e., placed in an auto-capture mode) violators of the monitored stop sign  720 . According to one feature of the system  700 , the stop sign enforcement module  710  (or system coordinator  118  or other software or hardware in processor  110 ) is adapted for determining when a vehicle  134  violates the stop sign law (i.e., runs the stop sign  720 ) by comparing a speed of the vehicle  134  detected by the laser speed detector  130  to a capture speed threshold. The capture speed threshold may be a default value (such as up to 10 mph or more) or may be entered by the operator  860  to comply with policies, regulations, and/or laws in force at the enforcement site (i.e., to comply with local, county, state, and/or national standards or rules). Typically, a capture speed threshold will be input at  860  based on standards set by the agency for which the operator is working and will be set to establish reasonable and fair thresholds for identifying violators of a stop sign  720 , e.g., a vehicle traveling at 10 mph or higher is unlikely to be able to stop within the enforcement window  736 . 
   Once the capture speed threshold is entered, the system  700  can be operated to monitor the stop sign  720  and automatically capture images and data for violating vehicles  134 . As part of  860 , the laser detector  130  is aimed at about the middle of the lane  724  and the system  700  is instructed to or switched to an automatic capture mode (such as by selecting a button on a menu of display  112 ). This automatic mode of stop sign enforcement involves continuous operation of the laser speed detector  130  to detect vehicle speeds and, at least periodically, to operate the synchronized digital camera  140  to capture images of violating vehicles  134  (i.e., vehicles  134  traveling at detected speeds above the set or default threshold). 
   As discussed above with regard to  FIGS. 1–6 , the camera  140  operates to capture images based on signals from the portable field processor  110 . Preferably, the camera  140  operates in synchronization with the speed detection by the detector  130  and does so in one of the manners described for system  100 . The camera  140  generally captures an image having a width, w CAPTURE , that preferably includes the stop sign  720  and the lane  724  but which may be narrower so as to capture all or a portion of the vehicle  134  in the lane  724 . This enables the camera  140  to capture an image of the stop sign  720  that is being violated and the entire front or rear portion of the vehicle  134  (or at least the license plate of the vehicle  134 ), including the license plate and, in some cases, the windshield and image of the drivers of the vehicle  134  when the system  700  is arranged as shown in  FIG. 7  to capture frontal images of vehicles  134 . The camera  140  is preferably aligned with the detector  130  to capture images corresponding generally with the speed detection location, i.e., the enforcement window  736  relative to the sign  720 . 
   The trigger signal for the camera  140  is initiated by the module  710  based on a determination that the detected speed received by the processor  110  from the detector  130  is above the capture speed threshold. In other words, the system  700  acts to identify stop sign violators based on a vehicle  134  not stopping. According to the invention, a vehicle&#39;s failure to stop is determined by the vehicle  134  being determined to be traveling above a threshold speed adjacent the stop sign  720  within an enforcement window  736  adjacent the stop sign  720 . A non-violating vehicle  134  (one traveling at a detected speed below or at the threshold) is assumed to be slowing down when entering the enforcement or measurement window of the detector  130  and then stopping (or going 0 mph). Hence, a fair threshold is one that assumes a relatively rapid reduction of speed within the enforcement window to avoid capturing images of vehicles  134  that stopped at the sign  720  but stopped quickly or within a relatively short distance (i.e., the length of the enforcement window  736 ). In this regard, a “fair” threshold value is generally in the range of 10 mph to 20 or more mph (at which speeds the vehicle  134  most likely would not be able to stop at the sign  720 ) with more conservative thresholds being set at the posted speed limits or percentages of the posted speed limits for the lane  724 . 
   The following operating examples are provided to more fully describe operation of the system  700  in enforcing stop sign laws. In a first non-limiting example, the capture speed threshold is set at 10 mph and the measurement distance, d RANGE , is determined to be 50 feet with a 10-foot window  736 . The car  134  approaches the monitored stop sign  720  and rolls into the front end of the enforcement window (i.e., about 60 feet from the detector  130  and about 10 feet behind the stop sign  720 ) at a speed of 18 mph. The laser speed detector  130  functions to detect the speed and transmit a signal to the processor  110  and stop sign enforcement module  710  (or system coordinator  118  or other software/hardware of processor  110 ). The module  710  determines that the threshold of 10 mph is exceeded and transmits a trigger signal to the camera  140  which captures the image (such as by freezing its buffer or taking a picture within its image timing cycle). 
   The camera  140  transmits the image of the vehicle  134  to the processor  110 . The image and enforcement information along with parameters are saved in memory  120  as a single digital file (as described in detail with reference to  FIGS. 1–6 ) or as two or more files that are linked or otherwise matched to assure proper mating of images, enforcement information, and parameters. The single file or multiple files typically include an image of the vehicle  134  and its license plate and information for the file header including time and date of violation, a distance to the vehicle  134 , and the detected speed of the vehicle  134 . Note, again, the detector  130  and camera  140  may be positioned in front of the sign  720  such that the system  700  acts to detect a violation, to capture an image of the back portion of the vehicle  134  and, in some embodiments, the front of the sign, and enforcement parameters. 
   In a second example, the measurement distance, d RANGE , determined in the ranging of step  850  is 60 feet, the measurement range of the detector  130  is 15 feet, and the capture speed threshold is entered at  860  to be 20 mph. When a vehicle  134  crosses the front (or distal) end of the measurement or enforcement window  736  (i.e., about 75 feet from the detector  130  and about 15 feet in front of the stop sign  720  in the lane  724 ) going 15 mph, the vehicle  134  is determined not to be violating the stop sign  720  and no image is captured. This is determined by the system  700  because the detector  130  targets the vehicle  134 , determines the speed of 15 mph, and transmits a corresponding signal to the processor  110  and module  710 . The module  710  compares the detected speed to the threshold and determines that no violation has occurred (or that the vehicle may stop at the sign  720 ) and does not transmit or initiate a trigger signal to the camera  140 . Numerous other examples will be apparent to those skilled in the art with varying capture thresholds, enforcement window sizes and locations, and positions for the detector  130  and camera  140 . 
   At  870 , the enforcement session is terminated, such as by an enforcement officer or an operator switching off power to the system  700  or selecting a stop button on the display  112  or elsewhere on the processor  110 . Termination can also be achieved by transmitting a termination signal from a remote device, such as a wireless transmission from the base station  160 . At  880 , the enforcement session data in memory  120  is downloaded from the processor  110 . Typically, this is achieved by transporting the processor  110  (and, optionally, the detector  130  and camera  140 ) to the location of the base station  160  and wiring the processor  110  to the base station  160 . Alternatively, the downloading may include removal of the memory  120  and then later insertion in the base station  160  for data transfer or include wired or wireless transmission of the data in memory  120  to the base station  160  (or another system) for further processing. 
   Of course, the data and images in the memory  120  can be viewed on the display  112  of the processor  110  by an operator prior to downloading to determine if downloading is required or useful. In some embodiments, the module  710  is further adapted to track numbers of violators or images in the memory  120 , such as based on actual image numbers or percentage of memory  120  being utilized. In these embodiments, the module  710  (or other software/hardware in processor  110 ) may be configured to transmit an alarm or notification signal to the base station  160 , such as by a wireless output device (not shown), when a certain number of images have been captured or percentage of the memory  120  has been utilized. Additionally, the module  710  or other components may operate to shut down monitoring operations at this point to avoid overwriting previously stored images. Automatic shutdown may also be instigated by the module  710  or coordinator  118  upon a low power level detection of battery system  126  (and such detection may also be accompanied by a warning or notification signal being transmitted by the processor  110  to the base station  160 ). 
   At  890 , the downloaded data is processed to create stop sign or traffic signal violation citations, traffic tickets, or warnings that can be transmitted to the operator or owner of the vehicle  134 . The processing may include magnifying or enlarging the display of the license plate or operator of the vehicle  134  and include other processing discussed with reference to  FIGS. 1–6 . Generally, the creation of the citation at  890  includes identifying license plate numbers in the captured images, matching registered owner information to the numbers (e.g., in a state&#39;s motor vehicle database), and printing a ticket including the owner&#39;s name and mailing address along with the violation (e.g., running a stop sign, failing to stop at a traffic light, and the like) and parameter (e.g., time and date and location) information. 
   In one embodiment of the system  700 , the system  700  is utilized for monitoring violators of a traffic signal when the signal has turned red. In other words, the stop “sign” is a traffic signal or light. In this embodiment, the system  700  includes a wired or wireless input (not shown) for receiving a signal indicating the state or status of the traffic signal. The signal may be generated by a separate device useful for determining light status, such as a device with a camera and processor for determining the state of the signal. In one embodiment, the signal is received from the targeted or monitored traffic signal device itself, which provides signals to indicate when the traffic light is red and a signal from the traffic signal device when the traffic light is green again. The module  710  (or other components of processor  110 ) operates to only monitor signals from the laser speed detector  130  when the light is red as indicated by the signals from the traffic signal device. When the light is red, operation of the system  700  in this embodiment is similar to that described relative to  FIGS. 7 and 8  with laser  130  and camera  140  generally directed to a particular lane  724  or particular lanes  724  (if more than one camera  140  and detector  130  are utilized in system  700 ). 
   In another embodiment of the system  700 , the digital camera  140  positioned in front or back of the sign  720  is supplemented or replaced by a video camera to allow a short video, such as a 5 to 10 second clip, to be captured of the stop sign violation. In this embodiment, the video camera is triggered by the processor  110  as soon as a speed is detected by the detector  130  that is above the threshold as determined by the module  710  or other software/hardware of processor  110 . In order to capture enough video footage, the system  700  may have to be adjusted to utilize a detector  130  with a larger measurement window or that has been set to detect a speed farther away from the stop sign (such as 20 to 50 feet in front of the stop sign  720  in the lane  724 ). In the earlier detection embodiment, the capture speed threshold would be set higher as the vehicle  134  would have a larger distance to stop. Alternatively, a second detector  130  may be provided that functions simply in detecting a possible violation by a vehicle  134  at a preset distance behind a stop sign  720 . This second detector  130  would detect a speed above a threshold (the same or more likely higher than the capture speed threshold) and the module  710  would first trigger the video based on this comparison. Then, the second detector  130  would detect a second speed within the enforcement or measurement window discussed previously and if determined above the capture speed threshold, the module  710  would save the video footage or mark the video for later use in proving the violation and after a set time period, terminate operation of the video camera (or the camera may be programmed to only capture a set length of footage each time it is instructed to operate by the processor  110 ). 
   Although the invention has been described and illustrated with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the combination and arrangement of parts can be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter claimed. For example, the system  100  can readily be used in daylight and at night with the addition of infrared and other flash devices or flood lighting. 
   Further, in one preferred embodiment, the portable field processor  110  is configured such the memory  120  or a separate memory (not shown) is readily removable. For example, it may be desirable that field officers or operators have their own processor  110  and simply exchange data at the end of shifts or the operators may simply have their own removable media and share the same processor  110 . This can be achieved with removable storage media, such as compact disks, floppy disks, flash cards, portable USB storage devices, and the like. The memory  120  or other memory to support this removable media may be a separate data storage device linked (such as with USB port) to the processor  110 . This configuration allows ready removal of data storage media and also facilitates field restoration of the application (system coordinator  118 ) if lost during field use (i.e., the application may be downloaded in the field by an operator).