Abstract:
A system for dynamically marking, with a temporary visible line, an athletic field surface, wherein the field has a first end, a second end, a first lateral boundary and a second lateral boundary. The system includes a laser source capable of producing a beam of radiation, and a displaceable actuator operatively associated with the laser source and adapted to direct the laser beam onto the athletic field surface. A controller including an electronic processor is programmed to cause displacement of the actuator sufficient to cause a visible line, extending from the first lateral boundary to the second lateral boundary, to appear and move between opposite ends of the athletic field surface. A portable, handheld user interface, which includes a wireless communication link, allows a single supervisory official to establish at least unidirectional communication with the controller. The controller responds to transmissions received from the interface by causing the visible line to advance to any position, selected by the official, between the first end and the second end of the athletic field.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates generally to devices for marking athletic fields during sporting events and, more particularly, to a system and method of using a hand-held interface to direct the movement of one or more movable light beams so as to provide an accurate line of demarcation during football games.  
           [0003]    2. Discussion of the Prior Art  
           [0004]    In athletic events such as football games, an important line of demarcation is the first “down” marker—a line that is located ten yards from the starting point for a series of offensive plays or downs. If the ball is not moved at least ten yards in four “downs” or plays, the team on offense loses possession of the ball. Presently, this ten-yard distance is determined by a set of chains held in position along the sidelines, with one stake or marker placed at approximately the point of the initial line of scrimmage. A supervisory official rules on the precise position of the ball after each ball—with that ruling constituting a determination of whether or not the offensive team has advanced from its previous field position.  
           [0005]    Frequently, during play, the offensive team advances approximately 10 yards, and in such a situation, a “measurement” is made using the chains. The chain crew attempts to move parallel to the yard lines, so that when the marker is placed in mid-field, it is located at the same point as it was on the sidelines. Obviously, such an antiquated procedure is quite time consuming and inaccurate, and in view of the extreme importance of such a measurement, is unwarranted. A number of approaches have therefore been proposed to simplify the process.  
           [0006]    In U.S. Pat. No. 3,741,662, for example, it is proposed to use multiple low-intensity light beams to produce a constant, visible wall of light. The beams serve to visually demarcate a scoring or score-advancing line wherein movement through the wall is of significance in playing the game. Each light beam emitting source is disposed within a carrier that is linearly moved, along a set of guide rails, in directions parallel to and outside of a boundary line of the playing area. That is, the light beam is directed horizontally from outside the playing area and is reciprocated vertically to create and maintain the vertical wall of light. While this approach represents a potential advance, in terms of accuracy, over the aforementioned chain-marker procedure, it is impractical for situations in which space on the sidelines is limited. Moreover, manual positioning of the beam-carriers requires the assignment of a dedicated ground crew and the position operation has been deemed too slow and cumbersome to be practical.  
           [0007]    In U.S. Pat. No. 4,090,708, a number of somewhat similar arrangements are disclosed. In a first embodiment, a single laser beam is configured to provide a luminous horizontal segment directed across the playing area, acting as an overhead line of demarcation in combination with a relatively lower parallel luminous segment of the same beam which is reflected reversely across the playing area to provide a ground-level demarcation line. Alternatively, two oppositely traveling light beams having a pair of horizontal luminous segments serve as a composite over-head demarcation line. These are employed in combination with a second pair of horizontal, relatively lower, luminous segments of the same beams that serve as a ground-level demarcation line.  
           [0008]    Due to their complexity and difficulties in implementation and use, neither of the aforementioned approaches has met with any degree of commercial success. Thus, while viewers of televised football games are now able to see a digitally superimposed line of demarcation—representative of the first down line marker on the field, that enhancement has heretofore eluded those members of the audience actually present at the stadium. A need therefore exists for a system capable of visibly displaying a line of demarcation at any desired location on an athletic field and characterized by a simple, easy to use, portable user interface.  
         SUMMARY OF THE INVENTION  
         [0009]    The aforementioned deficiencies are addressed, and an advance is made in the art, by a system for dynamically marking, with a temporary visible line, an athletic field surface, wherein the field has a first end, a second end, a first lateral boundary and a second lateral boundary. The system includes a laser projector capable of producing a beam of radiation, and at least one displaceable actuator operatively associated with the laser source and adapted to direct the laser beam onto the athletic field surface. The laser projector includes a scanning mechanism adapted to sweep the beam along a path designed to project a visible line onto the athletic field. A controller is configured to cause a displacement of the actuator sufficient to cause the visible line, extending from the first lateral boundary to the second lateral boundary, to appear on and move to a desired position on the athletic field surface. Where the laser source of the laser projector is configured to emit light at a wavelength within the visible band of the electromagnetic spectrum, a shutter mechanism—designed to block light from exiting the laser projector in the event of a malfunction of the scanning mechanism—prevents the beam from being directed at the eye of an individual on the field long enough to cause injury.  
           [0010]    A portable, handheld user interface, which includes a wireless communication link, allows a single supervisory official to establish at least unidirectional communication with the controller. The controller responds to transmissions received from the interface by causing the visible line to advance to any position, selected by the official, between the first end and the second end of the athletic field. In accordance with an especially preferred embodiment of the present invention adapted for use during football games, the interface includes a rotary mechanical operator for producing finely controlled movements of the visible line and momentary contact pushbutton operators for quickly but coarsely controlling the movements of the visible line. An optional refinement includes a mechanical operator adapted to issue a “last position” in memory command, whereby a previous position of the actuator—corresponding to a last “fixed” position of the visible line—is stored in memory and the process of advancing the visible line to a new first down location can be re-initialized by actuating the last position operator to direct the visible line back to this position. Still another refinement includes at least one mechanical operator such as a pushbutton which, when depressed, causes the actuator to advance (or reverse) the projected visible line by a predetermined distance (e.g., forward ten yards for a new first down, or back five or fifteen yards for a predetermined penalty). 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The invention will be further described with reference to embodiments thereof, illustrated by way of example on the accompanying drawings in which:  
         [0012]    [0012]FIG. 1 is a plan view showing first and second typical athletic field installations for a remotely operated, line demarcation system constructed in accordance with an illustrative embodiment of the present invention;  
         [0013]    [0013]FIG. 2 is a block schematic diagram depicting the respective functional components of a remotely operated, line demarcation system constructed in accordance with an illustrative embodiment of the present invention;  
         [0014]    [0014]FIG. 3 is a block schematic diagram depicting an exemplary actuator module adapted to direct the beam output of a laser source at the athletic field so as to produce a visible line at any desired location between a first goal line and a second goal line;  
         [0015]    [0015]FIG. 4 is a block schematic diagram depicting an exemplary communications interface adapted to establish a wireless communication link between the line demarcation system and a hand-held, portable remote control user interface;  
         [0016]    [0016]FIG. 5 is a block schematic diagram depicting an exemplary controller that is responsive to commands received from the remote control user interface to direct the operation of both the actuator module and the laser source;  
         [0017]    [0017]FIG. 6A is a block schematic diagram depicting the functional components of a hand-held, user interface constructed in accordance with the present invention; and  
         [0018]    [0018]FIG. 6B is a block schematic diagram depicting the external features of a hand-held, user interface constructed in accordance with an especially preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Referring to the drawings, and more particularly to FIG. 1, there is shown a football field surface  10  with yard lines  12  extending across the field at evenly spaced intervals. During the course of play, certain lines of demarcation are used. Of particular significance, and as illustrated in FIG. 1, are the initial scrimmage line  14 , present scrimmage line  16  and first down ten-yard line  18 . Other lines of significance on the surface of athletic field surface  10  include first and second goal lines  17  and  19 , a first lateral boundary  20  and a second lateral boundary  22 .  
         [0020]    In accordance with the present invention, a system for superimposing a visibly illuminated line over one of the aforementioned lines  14 ,  16  and  18  is provided. In the illustrative embodiment of the present invention, the system  30  includes a temporary visible line marking apparatus  32  disposed directly above the athletic field (at, for example, a distance of from about 50 to 500 feet) at its midpoint. As will soon became readily apparent, such an arrangement is especially easy to implement using a single, scanning beam laser source in that relocation of the temporary visible line requires only angular displacement of a single actuator about a horizontal axis transverse to field  10 . Since such a configuration will generally only be practical in the event of a domed stadium, a “sidelines” location of temporary visible line marking apparatus  32  (shown in dotted line)—wherein the apparatus is offset from the center of field  10  but is otherwise positioned at a vertical location sufficient to provide access to the entire field—is also contemplated. Indeed, depending upon budget, safety and access considerations, more sophisticated installations—for example, with the apparatus  32  being movable linearly along a track from one end of field  10  to the other or even positioned at one of the field—might be practical.  
         [0021]    In any event, and with reference now to FIG. 2, it will be seen that the line marking apparatus  32  of system  30  includes a laser beam projector  34 , an actuator module  36  for positioning of laser beam projector  34 , a communication interface  38 , with each of these being operative under the control of a controller indicated generally at  40 . Advantageously, operation of line marking apparatus  32  is remotely controlled by a hand-held, portable user interface  42 . Initialization of the system, and calibration of its respective components, is achieved using a PC terminal indicated generally at reference numeral  44 .  
         [0022]    The laser beam generated by beam projector  34  may be by any conventional well-known apparatus. Out of considerations of safety for the players on the field, the intensity and power of a beam emitted within the visible portion of the optical spectrum should be at the minimum level of power and intensity to achieve the objectives. In that regard, it should be noted that under current U.S. law, any party conducting a laser show or demonstration must apply for a “variance” to the Center for Devices and Regulatory Health (CDRH), a division of the Food and Drug Administration (FDA). Performers are permitted to have lasers on them under specified conditions. Generally, eye-safety issues are addressed by ensuring that the beam has a relatively large diameter, and by keeping the power level low. According to FDA regulations, employees (e.g., football players) can be exposed to Class II and IIa laser radiation levels as long as any direct viewing is only by accident for very brief periods. Preferably, however, the parameters of beam width, output power level and distance relative to field  10  are selected such that individuals standing on the field are only exposed to Class I radiation levels. In practice, the measurable irradiance at any point accessible to a person standing on field  10  (e.g. by jumping) should not exceed 10 milliwatts per centimeter squared, or 100 watts per meter squared.  
         [0023]    Since 1972, there has been an internationally agreed upon hazard concept: the “MPE” or Maximum Permissible Exposure. Actually, the MPE includes many different exposure limits, depending upon the laser wavelength and time of exposure. The MPE for a given wavelength and exposure duration means: 10 times less than the light level where 50% of subjects&#39; eyes had visible damage. Expressed another way: shining light at the MPE level into a subject&#39;s eye has a statistical chance of damaging 3 out of every 100 subjects. In summary, the MPE is a “worst case” safety factor. Exposure at the MPE level is already somewhat hazardous, so additional factors such as a moving (i.e., scanning) beam are assumed to further reduce risk. A typical requirement of the CDRH is that a failsafe be provided to rapidly block emissions by the laser in the event of a scanner failure—a safety feature that prevents a stationary beam from being directed into the eye for an impermissibly long interval. High inertia scanners (i.e., those which take more than one second for the scanning beam to stop moving) are considered relatively safe since they provide ample time for the actuation of a shutter (not shown). Thus, in an illustrative embodiment of the invention, laser projector  34  includes both an inertial scanning mechanism (not shown) for repetitively sweeping the laser beam to form a visible line on field  10  and a shutter (not shown) designed to stop light output in the event that mechanism fails.  
         [0024]    The failure of low inertia scanners (less than 1 second to stop), galvanometer scanners and AO deflectors are harder to detect within a time window sufficient to enable activation of even a very fast failsafe shutter like a PCAOM. Nonetheless, as shutter technologies advance, it is contemplated that systems constructed in accordance with the present invention could be configured to make use of them. Moreover, alternate arrangements—using a light beam emitted at a wavelength from the non-visible portion of the electromagnetic spectrum (e.g., an ultraviolet wavelength) might be used to stimulate phosphorescent compounds pre-applied to a surface of field  10 . An illustrative system of this type is disclosed in U.S. Pat. No. 5,174,571 issued to Aubusson et al. on Dec. 29, 1992.  
         [0025]    Turning now to FIG. 3, there is shown an illustrative 3-axis embodiment of an actuator module constructed in accordance with an exemplary embodiment of the present invention. As noted previously, when apparatus  32  is positioned at the location shown in solid line form in FIG. 1, only a single axis of movement is required to advance a line created by laser beam projector  34  from one end of field  10  to the other. However, in the dotted line location, additional adjustments in the position of laser beam projector  34  would be required in order to produce a consistently transverse line across field  10  as that line advances from end  17  to end  19 . To this end, exemplary actuator module  36  incorporates three servo motors—indicated generally at reference numerals  46 ,  48  and  50 —for independent angular displacement about first, second and third axes. The respective control wires for each servomotor are grouped in a bus  52  for connection to controller  40 .  
         [0026]    With reference now to FIG. 4, there is shown an illustrative communication interface for use in a line marking apparatus  32  constructed in accordance with the present invention. To receive operating commands from wireless communication with portable, wireless, hand held user interface  42 , apparatus  32  includes an RF receiver  56  and an RF antenna  58 . An RS- 232  interface, indicated generally at  54 , is also provided in order to facilitate initialization and calibration of the servomotors and other elements of system  32 . Electrical connections from RF receiver  56  and RS- 232  interface to controller  40  are achieved by wires  60 .  
         [0027]    As seen in FIG. 5, a controller  40  constructed in accordance with an illustrative embodiment of the present invention includes a scanning laser beam control unit  64  and a digital proportional radio control unit  62 . In accordance with an especially preferred embodiment of the invention, laser beam projector  34  (FIG. 2) is configured as an integrated, self-contained system that includes a laser emitter, collimating optics, a scanning mirror or deflector, and a power supply all disposed within a housing. Such packages are available commercially and can be simply and easily programmed to sweep an area so as to define any desired visible pattern. In accordance with such an embodiment, laser beam control unit  64  is operative to either energize or de-energize laser beam projector  34 . Digital proportional radio control unit  62 , in this embodiment, serves to execute commands received from the remote user interface by producing either coarse or fine angular adjustments in the positioning of the laser beam projector.  
         [0028]    As seen in FIGS. 6A and 6B, a hand held user interface constructed in accordance with an illustrative embodiment of the present invention includes a battery-powered power supply  66 , mechanical operators  68  for enabling a supervisory official to input commands directing apparatus  32  to reposition a temporary line marker, a command encoder  70  responsive to encode the manually entered input, and a wireless transmitter—such as RF transmitter  72 —configured to transmit operating commands to the communication interface  38  of apparatus  32 . With particular reference to FIG. 6B, it will be seen that the exemplary handheld user interface employs two different types of mechanical operators. For quick, “up the field” movements of the temporary line marker, first and second pushbuttons—indicated generally at reference numerals  68   a  and  68   b , respectively, are provided. While one of these pushbuttons are depressed, movements implemented by actuator module  36  occur at a rapid continuous pace, with the line marker advancing in the direction of the arrow corresponding to the pushbutton depressed. For finer movements, a rotary actuator or thumbwheel  68   c  is provided—thereby taking advantage of the ability of digital proportional radio control unit  62  to obtain precisely controlled operation of actuator module  36 . In accordance with an especially preferred embodiment of the invention, this rotary actuator -when properly calibrated—is operated to advance the marker by a precise distance calculated by the user, such that an advance of ten yards may be determined without even examining the markings on the field. If desired, one or more additional pushbutton operators (not shown) may be included in order to advance (or reverse) movement of the visible line by a predetermined amount (e.g., ten yards forward for a first down, five or fifteen yards back for a specified penalty, and so on).  
         [0029]    Assuming that the direction of play is to the left or downfield, as viewed in FIG. 1, and a first down has just been made, the supervisory official manipulates one or more of the mechanical operators so that laser projector  34  is angularly displaced about at least one axis and the trailing edge of a visible line transverse to the field advances to a point of intersection with a designated spot on the ball. This spot is preferably the forward tip of the ball. Using the “fine control” mechanical operator, which provides equal, incremental movements, the first down line now advances by ten yards to the location of the new first down line.  
         [0030]    Until another first down play is made, beam projector  34  continues to direct the line marker at the present first down line. Thus, after each down, the officials, players, and members of the audience have a continuous visible indication of the offensive team&#39;s proximity to the crucial first down line. When a new first down play is made, the position of the ball is marked as before and the line is advanced ten more yards, as before, to the new first down line.  
         [0031]    This arrangement, while incredibly simple in its implementation, presents several advantages to the owners of teams whose games are televised. In addition to the obvious cost savings in labor, the vastly reduced amount of time needed to make the first down measurement determination afforded by the present invention presents an opportunity to sell significantly more advertising time during the televised games. Moreover, the present apparatus provides a more effective method of determining the measurement for first downs and eliminates both the guesswork and human error in making such a determination.  
         [0032]    It will be appreciated that certain changes may be made in the various illustrative embodiments described above without departing from the scope of the invention, the latter being limited only by the claims which are appended hereto.