Abstract:
A dynamic laser based golf swing analysis system includes single and multiple laser sources which broadcast a monochromatic laser light projected through a cylindrical lens system to generate a series of light planes in space. An optical receiver system carried by the club shaft includes multiple optical sensors arranged in a specific three dimensional geometrical configuration such that passage of the optical receiver through the planes of laser light will produce direction and magnitude coordinates for all six degrees of freedom of the golf club head as it moves through a golf ball impact zone. The receiver transmits timing data via radio frequency to a base unit which interprets the information and displays the location coordinates, angular orientation, and velocities descriptive of the club head motion.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is related to and claims priority from Provisional Application Ser. No. 60/079,838 filed on Mar. 30, 1998 for a “Golf Swing Analysis and Method.” 
    
    
     FIELD OF THE INVENTION 
     The invention relates to an electronic system and method for the analysis of a golf swing, and in particular to quantifying the position, orientation, and velocity of the golf club as it moves through the golf ball impact zone. 
     BACKGROUND OF THE INVENTION 
     The dynamics of a golf swing are the contributing factors, which when coupled with the club face construction and the surface characteristics of a golf ball, will ultimately determine the trajectory of the golf ball. The relative motion and orientation of the golf club head and, in particular, its face as it impacts the golf ball determines the effective transfer of energy from the club to the ball. Subtle changes to certain components of the golf swing can have dramatic effects on the flight of the golf ball, some desirable, a majority typically undesirable. It is known in the art to provide a quantifying of the relative motion of the golf club head as it impacts the golf ball through the use of multiple video cameras and extensive, costly digital image processing. By way of example, U.S. Pat. No. 5,501,463 to Gobush et al. discloses a video image processing system that uses cameras for viewing light patterns on the club. The light patterns are then processed by a computer for determining a movement of the golf club. Other methods using magnetic, optical, and mechanical techniques typically only provide a limited amount of information regarding various aspects of the club head such as speed, face angle or slice. U.S. Pat. No. 4,979,745 to Kobayashi discloses the use of a sensor in the club head which detects light from a ground station emitter. The detection then causes an emitter in the club head to emit light. A measurement of time between peak light outputs provides a timing measure from which an angle and club head speed is determined. Yet another approach includes the use of sensors placed on the ground under a ball for detecting the shadow of the club head as it passes over the sensor. The timing differences between sensor detection of a shadow are used to determine club head speed and acceleration. In a similar manner, sensors are positioned to measure the heel and toe portion of the head for determining an angular component of the swing. Many approaches require sensor loops, reflective optics and other such devices that are cumbersome and thus obstruct the club swing, limit access to the golf ball, or require such extensive setup that they become impractical for use by the average golfer. There is a need to measure the characteristics of the golf swing without devices or techniques that are complex, costly, and or limited effectiveness. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing background, it is therefore an object of the invention to provide a system and method for analyzing a golf swing by quantifying a complete characterization of a golf club head movement as it passes through the impact zone of the golf ball. It is further an object of the invention to provide location coordinates, angular orientation, and velocities descriptive of the golf club head motion. It is yet another object of the invention to provide a system and method for measuring the club face loft angle, club face opening angle, club face toe-heel angle, slice magnitude, hook magnitude, chop direction and magnitude, club head height and lateral position relative to the ball both of which define the club head “sweet spot,” and club head velocity. 
     These and other objects, advantages, and features of the present invention are provided by a golf swing analysis system comprising a radiation source for providing a plane of radiation through which radiation plane a golf club can pass, a radiation sensor carried by the golf club, which sensor is responsive to an orientation of a ball striking face of a golf club head, timing means operable with the radiation sensor for receiving a radiation sensing signal and for determining a time period between passage of the first and second portions of the head through the radiation plane, and processing means for processing the time period and calculating a characteristic value for club head movement through a ball impact zone. The radiation sensor provides the radiation sensing signals in response to first and second portions of the golf club head passing through the plane of radiation. The timing means receive the radiation sensing signals for determining a time period between signals and thus between the passage of the first and second portions. In one embodiment of the present invention, communication means are operable between the timing means and processing means for providing the processing means at a location removed from the golf club. 
     In a preferred embodiment of the present invention, the radiation source provides a fan shaped laser beam generally perpendicular to the surface upon which a player stands for swinging the golf club. Preferably, the laser beam extends from the player to a golf ball to be struck, and is perpendicular to a target line passing through the club face and the golf ball toward a target. Further, the radiation sensor comprises a radiation receiver having a plurality of radiation sensors orthogonally arranged at measurable preselected locations with at least three of the plurality of radiation sensors for defining a radiation sensor plane. The radiation sensor plane is representative of the striking face of the club head. Each radiation sensor comprises an optical sensor responsive to a laser beam. 
     A preferred embodiment of the timing means comprises a trigger input module and a counter. The trigger input module receives the detection signal from the radiation sensor and provides a pulsed output indicative of the time period between passage of the first and second locations passing the radiation plane. The counter operates with the trigger module for receiving the pulsed output and counting a number of pulses between the radiation sensor signals. 
     The characteristic value for club head movement comprises loft angle, face angle, and golf club head velocity. With the radiation plane comprising first and second fan shaped laser beams intersecting each other and each vertically orientated and arranged at a measurable fixed angle to each other, and with the first fan shaped laser beam perpendicular to a target line passing through the club face and ball, the characteristics value comprises loft angle, face angle, toe-heel angle, slice velocity, hook velocity, and golf club head velocity. With the radiation plane comprising first, second, and third planar shaped laser beams intersecting each other, the characteristic value for club head movement comprises loft angle, face angle, toe-heel angle, slice velocity, hook velocity, chop velocity, golf club head velocity, and sweet spot. Here, the first and second planar shaped laser beams are vertically orientated, intersecting, and arranged at a measurable fixed angle to each other. The first planar shaped laser beam is perpendicular to a target line passing through the club face and ball, and the third planar shaped laser beam intersects the first and second planar shaped laser beams at a non-vertical angle. 
     Included in a preferred embodiment of the present invention herein describes is a laser module base unit consisting of three laser sources. Each laser source is coupled to a cylindrical lens assembly for the projection of a plane of laser light. The laser sources are oriented in a specific geometrical alignment to provide three intersecting planes of laser light at predetermined angles. The base unit containing the laser sources is positioned on the ground between the golfer and golf ball with the lasers directed toward the golf ball. The sensor module is clipped to the shaft of the golf club just above the club head and contains four sensors in a three dimensional, orthogonal pattern with predetermined distances between each sensor. The sensors contained in the sensor module trigger the system counter upon intersection with the planes of laser light. The relative counts are stored in a data queue and then transmitted via radio frequency to the base unit containing the laser source module and a microprocessor which calculates the club head location coordinates, angles and velocities at the point of impact with the golf ball. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     A preferred embodiment of the invention as well as alternate embodiments are described by way of example with reference to the accompanying drawings in which: 
     FIG. 1 is a perspective view of a golf swing analysis system of the present invention illustrating a use by a player; 
     FIG. 2 is a block diagram illustrating functional elements in one preferred embodiment of the golf swing analysis system of the present invention; 
     FIG. 3 is a functional block diagram illustrating a sensor embodiment of FIG. 2; 
     FIG. 4 is an orthogonal coordinate system illustrating its use in defining a sensor plane of the present invention; 
     FIGS. 5A,  5 B, and  5 C are perspective, elevation, and plan views of multiple laser sources and their respective planar beams used in an alternate embodiment of the present invention; 
     FIG. 6 is a functional block diagram illustrating one embodiment of the laser source configuration of FIGS. 5A-5C; 
     FIGS. 7A,  7 B, and  7 C illustrate one embodiment of a sensor geometrical configuration as described in an orthogonal coordinate system; and 
     FIGS. 8-16 illustrate characteristic values for a golf club head movement including face angle, loft angle, toe-heel angle, slice, hook, lateral position, positive chop, negative chop, and head height, respectively. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     Referring initially to FIGS. 1 and 2, a preferred embodiment of the present invention, a golf swing analysis system  10  useful in determining movement of a golf club head  12  during the execution of a golf swing by a player  14  comprises a laser source  16  for providing a plane shaped laser beam  18  through which beam the golf club head can pass. An optical sensor  20  is carried by a golf club  22 . The optical sensor  20  is responsive to an orientation of the club head  12  for providing a sensing signal  24 , responsive to portions of the club head passing through the laser beam  18 , as will be further detailed later in this section. As illustrated with reference to FIG. 2, a counter  26 , operable with the optical sensor  20 , receives the sensing signals  24  and defines a time period between passage of first and second portions of the club head  12  through the plane shaped laser beam  18 . As will be further described later in this section, a processor  28  processes the time period and calculates a characteristic value for club head movement through a ball impact zone. 
     The system  10 , in the embodiment herein described, further includes communication means comprising an RF transmitter  32  operable with the counter  26  for transmitting  33  data collected to a remote RF receiver  34  operable with processor  28 . 
     As illustrated again with reference to FIG. 1, the plane shaped laser beam  18  is perpendicular to the ground surface  36  upon which the player  14  stands for swinging the golf club  22 . Further, the laser beam  18  preferably extends from the player  14  toward a golf ball  38  to be struck, and is at a right angle to a target line  40  which passes through the club head  12  and the golf ball  38  toward a target, such as a golf course green. In a preferred embodiment, a base unit  42  carries the laser source  16 , RF receiver  34 , and processor  28 . The optical sensor  20 , counter  26 , and RF transmitter  32  are carried by the golf club  22  in a sensor module  44 . A display  46  is also carried in the base unit  42 , as illustrated again with reference to FIG.  2 . 
     As illustrated with reference to FIG. 3, the optical sensor  20  comprises an optical receiver  48  having a four (A, B, C, D) optical sensors  20 A,  20 B,  20 C, and  20 D, each providing a trigger input  50  to the counter  26 . As illustrated with reference to FIG. 4, the sensors  20 , identified for convenience as A, B, C, and D, are orthogonally arranged at measurable preselected locations X, Y, Z within the orthogonal coordinate system with three sensors  20 A,  20 C, and  20 D, by way of example, lying within and thus defining a sensor plane  52 . The sensor plane  52  is oriented so as to be representative of the striking face on the club head  12 . 
     In a preferred embodiment of the present invention, timing means include the counter  26  which receives the trigger input  50  each time any one of the sensors  20 A,  20 B,  20 C, or  20 D, passes through the plane shaped laser beam  18 . Timing pulses from the counter  26  are interrupted, and a pulse count or count value from the counter is then stored in a data queue  54  until the swing is complete. Once the swing is complete, count data is fed to the RF transmitter  32  which in turn transmits this data to the RF receiver  34  carried within the base unit  42 . The data representative of count value is then passed to the arithmetic processor  28  for reduction. The arithmetic processor  28  calculates the position, angular orientation, and velocities of the club head  12  at the point of impact with the ball  38 . These values are then sent to the display  46  for viewing. 
     With the embodiment as described with reference to FIGS. 1-4, the characteristic values for club head movement can include loft angle, face angle, and golf club head velocity. In an alternate embodiment, a second planar shaped laser beam  56  is provided, wherein the first beam  18  (earlier described) and this second  56  fan shaped laser beam, as illustrated with reference to FIGS. 5A,  5 B, and  5 C, intersect each other and each are vertically orientated and arranged at a measurable fixed angle to each other. As earlier described with reference to FIG. 1, first laser beam  18  is perpendicular to the target line  40 . With the use of two laser beams  18 ,  56 , the characteristic values available increase over that earlier described. They will now includes loft angle, face angle, toe-heel angle, slice velocity, hook velocity, and golf club head velocity. In yet another embodiment including the first  18 , the second  56 , and a third  58  planar shaped laser beam, each intersecting each other, with the first and second vertically orientated, intersecting, and arranged at a measurable fixed angle to each other, the first beam perpendicular to a target line  40 , and the third planar shaped laser beam intersecting the first and second beams at a non-vertical angle, as illustrated again with reference to FIGS. 5A,  5 B, and  5 C. With such a three beam arrangement, the characteristic values available include loft angle, face angle, toe-heel angle, slice velocity, hook velocity, chop velocity, golf club head velocity, and sweet spot. 
     As illustrated with reference to FIG.  6  and again to FIG. 2, the laser source  16 , a laser module includes three separate laser sources  16 A,  16 B,  16 C which are conveniently housed in the base unit  42  for the preferred embodiment herein described. As herein described, each laser broadcasts a plane of light at a predetermined angle relative to each other. With regard to the orientation of the laser beams  18 ,  56 , and  58 , described with reference again to FIGS. 5A,  5 B, and  5 C, the relative angles between the laser beam planes are also arbitrary but must be known a priory. As earlier described, the first plane shaped laser beam  18  is projected as a vertical plane of light with respect to the ground surface  36 . The second laser beam  56  is also projected as a vertical plane of light but at an intersecting angle with the first beam  18 . The third planar beam  58  intersects the first  18  and second  56  and is at a non-vertical angle with respect to the ground surface  36 . 
     The specific sensor geometry for one preferred system includes a spacing of the sensors  20  selected for desired aesthetic characteristics while optimizing the overall system performance. However, their arrangement may be arbitrary as long as the exact values of the distance between sensors  20  is known. By way of example, and as illustrated again with reference to FIG. 4, Sensors  20 A,  20 C, and  20 D are located in a single plane which defines the sensor plane  52 , with sensor  20 B along a line orthogonal to the plane  52 . The sensor geometry for all four sensors  20  are illustrated with reference to FIGS. 7A,  7 B, and  7 C. The location of Sensor  20 B is chosen as the origin of the orthogonal coordinate axis. 
     The exact sensor position values (X, Y Z) and their offset from reference sensor  20 B in the selected coordinate space is determined during the manufacturing phase of the system. These values are calibrated and stored as arithmetic constants and are used by the arithmetic processor  28 . Using sensor  20 B as the origin of the three dimensional coordinate structure, the calibrated values for the remaining sensors are as follows: 
     Sensor A ( 20 A): A x , A y , A z , 
     Sensor C ( 20 C): C x , C y , C z , 
     Sensor D ( 20 D): D x , D y , D z , 
     The measured quantities during the swing are the relative counts (from the counter  26 ) between the intersection of each sensor with each plane of laser light. Using planar laser beam  18  as illustrated with reference again to FIGS. 5A-5C, the measured values take the form of: 
     
       
         t a1 , t c1 , t d1   
       
     
     where t represents the count value, and a, c, d indicates the respective sensor and  1  represents the first laser plane i.e. laser plane  18 . 
     Given the geometry as earlier described with reference to FIGS. 7A-7C, for the sensors  20 , the mathematical equation for the calculation of the club face angle as defined in FIG. 8 can be reduced to the following expression.        α   =       tan     -   1            [           (         t   a1          D   z       -       t   d1          A   z         )          (         A   y          C   z       -       C   y          A   z         )       -       (         t   a1          C   z       -       t   c1          A   z         )          (         A   y          D   z       -       D   y          A   z         )               (         t   a1          C   z       -       t   c1          A   z         )          (         A   x          D   z       -       D   x          A   z         )       -       (         t   a1          D   z       -       t   d1          A   z         )          (         A   x          C   z       -       C   x          A   z         )           ]                              
     Once this parameter has been determined, the loft angle as defined in FIG. 9, may also be calculated using the following expression along with the measured values described above:        θ   =       tan     -   1            [           (         t   a1          D   x       -       t   d1          A   x         )        sin                 α     -       (         t   a1          D   y       -       t   d1          A   y         )        cos                 α         (         t   d1          A   z       -       t   a1          D   z         )       ]                              
     The club head velocity may also be calculated using the above values in the following expression:          S   y     =     [       c   y1       t   c1       ]                            
     where the term c y1  is calculated using the following equation: 
     
       
         C y1 =C x  cos θ sin α+C y  cos θ cos α+C z  sin θ 51    
       
     
     Using the second planar laser beam  56  created by laser  16 B as illustrated with reference again to FIGS. 5A-5C, and the previously calculated values for the angles α, and θ, the toe-heel angle φ, as defined in FIG. 10, can be determined using the following expression:        φ   =         tan     -   1            [       b   3       a   3       ]       -       cos     -   1            [       c   3           a   3   2     +     b   3   2           ]                                
     where 
     
       
         a 3 =a 1 (t c2 −t b2 )−C 1 (t a2 −t b2 ) 
       
     
     
       
         b 3 =a 2 (t c2 −t b2 )−C 2 (t a2 −t b2 ) 
       
     
     
       
         c 3 =M[a yl (t c2 −t b2 )−C yl (t a2 −t b2 )] 
       
     
     and 
     
       
         a 1 =A x  cos α−A y  sin α 
       
     
      c 1 =C x  cos α−C y  sin α 
     
       
         a 2 =−A x  sin θ sin α−A y  sin θ cos α+A z  cos θ 
       
     
     
       
         c 2 =−C x  sin θ sin α−C y  sin θ cos α+C z  cos θ 
       
     
     and where M is slope of planar laser beam  56  with respect to the Y axis coordinate of the sensors  20 . 
     The measured values take the form of: 
     
       
         t a2, t   c2 , t d2   
       
     
     where t represents the count value, and a, c, d indicates the respective sensor and  2  represents the second laser plane  56 . 
     Using the value for the toe-heel angle φ, calculated above, plus the previously calculated values for the angles α, and θ, and the club head velocity value S y  the magnitude for the slice and hook component of the swing as shown in FIGS. 11 and 12, respectively, can be determined with the following expression:          S   x     =     [         M   *       S   y          (       t   c2     -     t   b2       )         +     (     M   *     c   y1       )     -     c   x1         (       t   c2     -     t   b2       )       ]                            
     where 
     
       
         c x1 =c 1  cos φ+c 2  sin φ 
       
     
     
       
         c y1 =C x  cos θ sin θ+C y  cos θ cos α+C z  sin θ 
       
     
     and 
     
       
         c 1 =C x  cos −C y  sin α 
       
     
     
       
         c 2 =−C x  sin θ sin a−C y  sin θ cos α+C z  cos θ 
       
     
     and where M is slope of laser plane B with respect to the Y axis coordinate of the sensors  20 . 
     The measured values take the form of: 
     
       
         t c2 , t b2   
       
     
     where t represents the count value, and c, b indicates the respective sensor and  2  represents the second planar laser beam  56 . 
     Using the above calculated value for the slice or hook velocity, plus the club head velocity, the value for the club head translation with respect to the ball as illustrated with reference to FIG. 13, can be calculated using the following equation: 
     
       
         X=(S x −M*S y )*t b2   
       
     
     where M is slope of laser plane B and t b2 is the same measured quantity used in the previous expression above. 
     Adding the third planar laser beam  58  created by laser source  16 C, and using the previously calculated values for the angles α, θ, φ, and the club head velocity value S y  the direction and magnitude for the chop component of the swing as shown in FIGS. 14 and 15, can be determined using the following expression:          S   z     =     [         Q   *       S   y          (       t   c3     -     t   b3       )         +     (     Q   *     c   y1       )     -     c   z1         (       t   c3     -     t   b3       )       ]                            
     where 
     
       
         c y1 =C x  cos θ sin α+C y  cos αcos α+C z  sin θ 
       
     
     
       
         c z1 =c 2  cos φ−c 1 sin φ 
       
     
     and 
     
       
         c 1 =C x  cos α−C y  sin α 
       
     
     
       
         c 2 −C x  sin θ sin α−C y  sin θ cos α+C z  cos θ 
       
     
     and where Q is slope of the third planar laser beam  58  with respect to the Y axis coordinate of the sensors  20 . 
     The measured values take the form of: 
     
       
         t c3 , t b3   
       
     
     where t represents the count value, and c, b indicates the respective sensor and  3  represents the third laser plane i.e. laser plane. 
     Using the above calculated value for the chop direction and magnitude, plus the club head velocity, the value for the club head height translation with respect to the ground as shown in FIG. 16, can be calculated using the following equation: 
      Z=(S z −Q*S y )*t b3   
     where Q is slope of laser plane C and t b3  is the same measured quantity used in the previous expression above. 
     The absolute quantities for the motion of the golf club head can be determined with the above derivations provided accurate positions for the source lasers is known. What is more desirable for the devices intended use is to determine the relative position and motion of the club head in relation to the golf ball. This is done by taking data during the back swing as the club moves away from the ball and using these results as a reference for the forward swing. 
     The derivations above are for a general case of sensor geometry. The sensor geometry can be selected to be a variety of orientations some of which can simplify the required calculations other orientations may provide more condensed packaging. The overall application determines the optimal sensor construction since the basic concept can be employed to measure the motion of almost any moving object. A wider sensor spacing provides greater system accuracy but the calculations remain the same. 
     A prototype system was constructed using the following sensor spacing: 
     Sensor A: A x =0.250 
     A y =0 
     A z =0.250 
     Sensor C: C x =−0.100 
     C y =0.100 
     C z =0 
     Sensor D: D x =0.250 
     D y =100 
     D z =−0.250 
     Units are in inches. The respective resolution of the system for the angles α and θ was 0.1 degrees. For the angle φ, the resolution was 0.3 degrees. The velocities S x , S y , S z  had a resolution of 0.01 mph. The lateral and height components had a calculated resolution of 0.1 inches. 
     In summary, operation includes the sensor module  44  which is attached to the golf club shaft just above the interface between the club shaft and the club head  12 . The base unit  42  which contains the laser sources  16  is positioned on the ground surface  36  between player/golfer  14  and the golf ball  38  with the laser beam  18  directed toward the golf ball. During a swing, the golf club moves through the various planes of laser beams  18 ,  56 ,  58  as above described, which beams are detected by the sensors  20 . Data is transmitted to the base unit  42 , which calculates and displays the club head position, orientation and velocity relative to the golf ball at the point of impact with the golf ball. 
     As described, the system  10  herein described uses a set of laser sources positioned to illuminate the impact zone  30  preceding the ball  38 . By way of example, positioning the sensor plane  52  between the ball  38  and laser plane  18  at address, an initial setting is completed during the back swing. Measurements are then made from the initial setting as the plane  52  passes through the plane  18  during the down swing. The basic concept of the system  10  is by nature expandable to include multiple laser sources before and after the ball to provide multiple data points along additional portions of the swing path. This data can then be graphically represented via computer to give a further characterization of the swing. 
     Likewise, the data can be downloaded to a personal computer and used to generate a graphical representation of the club head position and orientation at the point of impact with the golf ball. The system  10  can be used indoors as well as outdoors to provide off season practice or indoor coaching. The sensor module  44  attaches to any golf club  12 , and a golf ball does not need to be present for the system  10  to operate. Further, it is anticipated that training clubs will be constructed with the sensor module  44  integrally formed within the club. The data collected can also be used in conjunction with environmental data and course descriptive data to create an expert system for the proper club selection and club head speed requirements and club head angles required to achieve a desired ball trajectory. 
     The present invention described in this document has been constructed and demonstrated in prototype form. The system  10  herein described, provides a very cost effective way to completely and accurately characterize important features of a golf swing, and without cumbersome devices being placed in such a way as to impede the swing or being placed directly in the swing path. The system can also be easily expanded to increase over all system functionality. The devices described in this document represents a viable and demonstrable break through for the characterization and analysis of the golf swing in such a way as to be affordable and useable to the average golfer by providing information that to date has not been available by any other device or means at this level of completeness for a single swing or impact event. 
     It is therefore expected that many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims.