WO2002102475A1

WO2002102475A1 - Method and apparatus for analyzing a golf stroke

Info

Publication number: WO2002102475A1
Application number: PCT/US2002/018243
Authority: WO
Inventors: George K. Shoane
Original assignee: Rutgers, The State University Of New Jersey
Priority date: 2001-06-07
Filing date: 2002-06-07
Publication date: 2002-12-27
Also published as: WO2002102475A9; US20030144088A1

Abstract

A method of analyzing and practicing golf strokes, such as putting strokes, is provided. A surface is provided, wherein a golfer (20) can practice one or more strokes in an environment simulating components of a golf course, such as a green. A club movement detector embedded in the surface and comprising a plurality of photodetectors and associated circuitry determines the position and velocity of the club face. A head movement sensor (40) detects rotational movement of the golfer's head during the golf stroke. An eye movement sensor (50) detects movement of the eyes of the golfer during the golf stroke. A processor (70) connected to the club movement sensor (60), eye movement sensor (60), and head movements sensor (50) gathers movement data during the golf stroke and produces measurements corresponding to the golf stroke, such as eye, head, and club movement of the golfer. The invention includes measuring head movement data and wirelessly transmitting same for remote analysis during a golf stroke.

Description

METHOD AND APPARATUS FOR ANALYZING A GOLF STROKE

SPECIFICATION BACKGROUND OF THE INVENTION

RELATED APPLICATIONS

The present invention claims the benefit of U.S. Provisional Application Serial No. 60/296,527 filed June 7, 2001, U.S. Provisional Application Serial No. 60/317,944 filed September 10, 2001, U.S. Patent Application Serial No. 10/107,910 filed March 27, 2002, and U.S. Provisional Application Serial No. 60/371,699 filed April 11, 2002, the entire disclosures of which are all expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for golf stroke analysis, and more particularly, to a method and apparatus for analyzing components of a golf stroke including club face movement and the physical movement of a golfer during a stroke. The present invention also relates to a method and apparatus for allowing golfers to practice and improve their golf strokes.

RELATED ART hi the field of sports, generally, and in the game of golf, particularly, there has been an increasing need to address specific questions posed by athletes concerning the body's forces and motions during athletic activities. Much information has been acquired about the golf swing and the physical forces associated therewith, including forces impacting the golf ball. Such information has been obtained using high-speed photography and videotape, and the components of the golf swing have been studied in great detail during, at least, the past 50 years. Unfortunately, such methodologies do not allow for real-time analysis of a golfers' stroke.

The putting stroke is a crucial element in the game of golf. Statistics compiled by the Professional Golfer's Association show that approximately 40% of the total strokes by professional golfers in a given round are spent on putting. Golf teaching professionals and sports psychologists frequently teach beginning and experienced golfers the importance of minimal or ho eye and head movements throughout the putting stroke. Reduced eye movement is particularly important to successful execution of the putting stroke, because eye fixation at locations other than the ball can cause improper strokes and missed puts. Further, reduced head movement allows a golfer to maintain a stable image of a putting surface, thereby enhancing the golfer's accuracy at putting. If the golfer's head moves during the stroke, putting misalignment and missed putts can result. Additionally, putter head velocity and acceleration, in conjunction with a golfer's grip, are useful indicators of a golfer's putting accuracy and ability.

What would be desirable, but has not yet been provided, is a system for analyzing the aforementioned aspects of a golfer's putting stroke, and producing realtime results indicating the effectiveness and accuracy of the putting stroke, and for allowing golfers to practice their strokes while also receiving feedback information.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and apparatus for analyzing golf strokes.

It is another object of the present invention to provide a method and apparatus for analyzing putting strokes.

It is an additional object of the present invention to provide a method and apparatus for allowing a golfer to practice and improve his or her golf stroke, while receiving feedback thereon and allowing for the comparison of measurements of the swing to measurements of a professional golfer's swing.

It is a further object of the present invention to provide a method and apparatus for measuring eye, head, and club movement during a golf stroke, including a putting stroke.

It is an additional object of the present invention to provide a method and apparatus for analyzing a golf stroke including a club movement sensor for measuring club movement.

It is still another object of the present invention to provide a method and apparatus for analyzing a golf stroke including a head movement sensor for measuring head movements during the stroke.

It is a further object of the present invention to provide a method and apparatus for analyzing a golf stroke including an eye movement sensor for measuring eye movements during the stroke.

It is another object of the present invention to provide a method and apparatus for analyzing a golf stroke including a processor for acquiring eye, head, and club movement data and processing same.

It is still another object of the present invention to provide a method and apparatus for comparing eye, head, and club movement data of a golfer to eye, head, and club movement data of golfers of various experience levels.

It is yet another object of the present invention to provide a method and apparatus for determining the effect of different golf grips on eye, head, and club movement during a golf stroke, including a putting stroke.

The present invention relates to a method and apparatus for analyzing and practicing a golf stroke, particularly a golf putting stroke. A putting platform is provided, wherein a golfer can putt in an environment simulating a golf green. Information regarding the golfer's eye, head, and club movements during the putting stroke are acquired using a plurality of sensing devices. A club movement sensor in the putting surface measures club movements during the stroke, without requiring attachment to the club. Eye movement sensors measure left and right eye movements of the golfer during putting. A head movement sensor tracks rotational movement of the golfer's head during the putting strokes. The acquired motion data are gathered simultaneously by a processor, and time traces of club, head, and eye movement may be generated. The time traces can be compared to time traces of golfers of various experience levels to determine the accuracy and efficiency of the golfer's putting stroke. Additionally, the effect of various golfing grips on eye, head, and club movement can be measured and analyzed. As such, a golfer can practice and improve his or her golf stroke, and compare measurements thereof to measurements of others, such as professionals.

BRIEF DESCRIPTION OF THE DRAWINGS

Other important objects and features of the invention will be apparent from the following Detailed Description of the Invention taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of the apparatus of the present invention during use by a golfer.

FIG. 2a is a top view of the club movement sensor shown in FIG. 1.

FIG. 2b is a side view of the club movement sensor and a portion of the putting surface shown in FIG. 1.

FIG. 2c is an end view of the club movement sensor and a portion of the putting surface shown in FIG. 1.

FIG. 3 is a perspective view of an embodiment of the head movement sensor shown in FIG. 1.

FIG. 4a is a side view of the eye movement sensor shown in FIG. 1.

FIG. 4b is a side view showing the eye movement sensor of FIG. 1 shown in greater detail.

FIG. 5 is a block diagram showing components of the present invention.

FIG. 6 is a schematic diagram showing a circuit configuration of the club movement sensor of the present invention.

FIG. 7 is a diagram showing operation of the club movement sensor.

FIG. 8 is a graph showing a time trace of club movement during a putting stroke.

FIG. 9 is a graph showing a time trace of eye movement during a putting stroke.

FIG. 10 is a graph showing a time trace of head movement during a putting stroke.

FIG. 11a is a graph showing a time trace of club movement of an experienced golfer during a putting stroke.

FIG. lib is a graph showing a time trace of club movement of a novice golfer during a putting stroke.

FIG. 12 is a graph showing simultaneous time traces of eye, head, and club movement during a putting stroke. FIG. 13a is a graph showing simultaneous time traces of eye, head, and club movement of a novice golfer during a putting stroke.

FIG. 13b is a graph showing simultaneous time traces of eye, head, and club movement of an experienced golfer during a putting stroke.

FIG. 14 is a graph showing time traces of eye, head, and club movement when a conventional golf grip is used during a putting stroke.

FIG. 15 is a graph showing time traces of eye, head, and club movement when a cross-handed golf grip is used during a putting stroke.

FIG. 16 is a graph showing time traces of eye, head, and club movement when a one-handed golf grip is used during a putting stroke.

FIG. 17 is a table showing results of statistical analysis of conventional, cross- hand, and one-handed grips used during 3 foot and 9 foot putts.

FIG. 18 is a photograph showing an embodiment of the present invention for analyzing head movement during a golf stroke uses an accelerometer and that wirelessly transmits the acquired data to a processor.

FIG. 19 shows an embodiment of a head movement sensor of FIG. 18.

FIG. 20 is a schematic showing a circuit for use with the embodiment of the present invention shown in FIG. 18, for converting accelerometer output to head rotation data.

FIG. 21 is a graph showing time traces of putter, eye, and head movement measured using the apparatus of FIG. 18.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method and apparatus for analyzing golf strokes, particularly a putting stroke. A variety of physical movements can be tracked and analyzed during the golf stroke, such as eye, head, and club movement, and time traces thereof can be produced in real time. The sampled data can be compared with pre-recorded time traces of golfers at different experience levels, to determine the accuracy and efficiency of the golfer's stroke. Further, the effects of various golf grips on eye, head, and club movement can be determined. A golfer can practice and improve his or her game, and compare measurements relating to his or her golf stroke to measurements of professionals.

FIG. 1 is a perspective view of an embodiment of the present invention. The system of the present invention comprises a variety of components which, operating in conjunction, provide golf stroke analysis. A putting surface 80 is provided for a golfer 20 for taking practice putting strokes using any club 30 and golf ball 34 known in the art. Movement of club 30 along a path generally indicated by line 32 can be analyzed by club movement sensor 60, embedded in putting surface 80, as will be hereinafter further described. Importantly, club movement sensor 60 does not obstruct the path of golf ball 34, allowing golfer 20 to putt normally and (hopefully) sink golf ball 34 into hole 82. Further, putting movement sensor 60 allows for the analysis of movement of club 30, without requiring the attachment of any apparatus thereto.

In an embodiment of the present invention, putting surface 80 can be partitioned into two or more surfaces that can be positioned lengthwise to allow for putts of varying lengths. For example, two sections of putting surface 80 can be joined to allow for putts of three feet in length, additional sections can be added to allow for putts of nine feet in length. Any combination of sections of putting surface 80 can provided for allowing putts of any desired length.

Movement of the head of golfer 20 during the putting stroke can also be measured by the present invention. Rotational movement of the head of golfer 20, indicated generally along axis 24, can be measured by head movement sensor 40, attached to helmet 41, as will be hereinafter further described. It is to be understood that other types of head movement (i.e., side-to-side) are contemplated by the present invention and considered within the scope thereof. Head movement sensor 40 can be any sensor known in the art, e.g., an accelerometer with wireless transmitter and receiver, that is capable of measuring rotational movement.

Eye movements of golfer 20 can also be analyzed by the present invention by eye movement sensor 50, as will be hereinafter further described. In a prefened embodiment, eye movement sensor 50 is an infrared device that tracks motion of both right and left eyes of a golfer. Other eye movement sensors are considered within the scope of the invention.

Movement data generated by eye movement sensor 50, head movement sensor 40, and club movement sensor 60, is transmitted to processor 70 by cables 72. It is conceivable that other means for transmitting the acquired data, such as radio frequency ("RF") or infrared ("IR") transmission, can be utilized to channel the acquired movement data to processor 70. The movement information gathered by processor 70 during a putting stroke can then be analyzed to determine the accuracy and efficiency of the putting stroke.

FIG. 2a is a top view of the club movement sensor of the present invention. Putting motion sensor 60 comprises first detector array 62, and second detector anay 64, each of the detectors having a plurality of detectors 66. In a prefened embodiment of the invention, detectors 66 are infrared phototransistors. As a club moves along axis 32, shadows are cast on one or more of the detectors 66, whereupon the one or more detectors 66 turn electrically off. The outputs of detectors 66 of both first detector anay 62 and second detector array 64 are then fed to processor 70 via cables 72. The second detector anay 64 is positioned to track movement of the club to impact. Thereafter, the first detector anay 62 is positioned to track movement of the putter after impact. The first detector anay 62 is offset from the second detector array 64, so that golf ball 34 can travel freely along path 36 without traveling over detectors 66 of first detector anay 62. Other spatial configurations of club movement sensor 60, first detector anay 62, and second detector anay 64 are considered within the scope of the present invention.

FIG. 2b is a side view of the club movement sensor 60 and putting surface 80 of the present invention. In a prefened embodiment of the present invention, detectors 66 are positioned at increasing intervals away from the ball 34, in both frontward and rearward directions. For example, the first four detectors 66 of first detector anay 62 and second detector anay 64, closest to ball 34, are spaced approximately Vi inch apart. The next two detectors are spaced 1 inch apart. The remaining two detectors are then spaced 2 inches apart. It is to be understood that additional detectors and other spatial arrangements are considered within the scope of the present invention.

FIG. 2c is an end view of the club movement sensor 60 and putting surface 80 of the present invention. The surface 80 can be constructed of wood boards 82, 84, and 86, such as particle boards, which are joined together and covered with artificial grass to form putting surface 80. Other materials capable of forming putting surface 80 are considered within the scope of the present invention. Putting surface 80 contains cavities for retaining embedded detector anays 62 and 64.

FIG. 3 is a perspective view of the head movement sensor of the present invention. Rotational movement of a golfer's head about axis 24 can be measured during a putting stroke by sensor 44. A golfer wears hat or helmet 41 which transfers rotational movement of the golfer's head to sensor 44, via interconnections 42 and 43. Interconnections 42 and 43 are designed to mate interchangeably, and allow a user to step away from sensor 44 to disengage therefrom. It may be desirable to magnetize these components to facilitate engagement thereof. Interconnection 42 is attached to hat or helmet 41, and interconnection 43 is attached to sensor 44. Sensor 44 can be any sensor in the art that is capable of measuring rotational movement, such as a potentiomenter. According to an embodiment of the invention, sensor 44 is mounted via pivot 45 to a fixed surface, and output from sensor 44 is transmitted via cables 72. It is to be understood that various other configurations are considered within the scope of the invention. For example, sensor 44 could be mounted on the hat or helmet 41, and could be self-contained, i.e., not attached to a fixed surface. The sensor could contain a pendulum such that when one rotates his or her head, a reading is taken. Further, this reading could be wirelessly transmitted to the processor. Additionally, other headgear can be used to receive the golfer's head and transfer movement thereof to a sensor.

FIG. 4a is a side view of the eye movement sensor 50 of the present invention. Eye movement sensor 50 can be any sensor known in the art that is capable of measuring eye movements, such as a Skalar-Iris Model 6500 helmet-mounted infrared reflection device. Other comparable detection devices can be used with the present invention without departing from the scope thereof. In a prefened embodiment, eye motion sensor 50 contains one or more infrared detectors 52 that are pointed generally in the direction of the golfer's eyes and measure eye motion of the golfer (i.e., left-to- right and right-to-left eye motion). Output from the one or more infrared detectors 52 can be sent to a processor via cables 72, or wirelessly. Optionally, eye motion sensor 50 can be affixed to hat or helmet 41 via frame 54, or formed integrally therewith. Alternatively, the sensors can be incorporated on eyewear. Preferably, hat or helmet 41 and eye motion sensor 50 are manufactured to be lightweight, so that a golfer experiences minimal to no discomfort while wearing same during a golf stroke.

FIG. 4b is a side view showing the eye movement sensor 50 of the present invention shown in greater detail. Movements of a golfer's eyes, such as eye 26, can be tracked by infrared detectors 52. In a prefened embodiment of the present invention, infrared detectors 52 of eye movement sensor 50 have a linear range of +/- 25 degrees, a combined resolution of 5 minutes of arc, and a bandwidth of 200 Hz, but these tolerances are not required. Voltage output signals of eye movement sensor 50 represent eye movements of the golfer's eyes, and can be analyzed by a processor.

FIG. 5 is a block diagram showing component parts of the present invention. Outputs from the head movement sensor 40 and eye movement sensor 50 are connected to analog-to-digital (A/D) converters 90 and 92, respectively. Club movement sensor 60 is connected to digital input port 94. The resulting digital signals derived from each of the sensors 40, 50, and 60 are then processed in real time by processor 70. Processor 70 can be any computer system known in the art. In a prefened embodiment of the present invention, processor 70 acquires the digitized movement data from each of the sensors, and outputs same. Such output may comprise synchronized time trace plots indicating movement of the right eye, left eye, club, and head of the golfer. As shown in FIG. 5, such data can be output through numerous channels (i.e., channels 1 through 4) for presentation to the golfer or for further data processing.

FIG. 6 is a schematic diagram showing an example of a circuit configuration of the club movement sensor 60 of the present invention. A plurality of infrared sensors, such as phototransistors Qi through Q„, can be connected to provide club movement detection. For purposes of illustration, only phototransistors Qi through Q₄ are shown connected in the circuit of FIG. 6. Further, other light-sensing devices, such as CdS photocells, can be used in place of the phototransistors. Each of phototransistors Qi through Q₄ are connected to difference amplifiers Di through D₄, which reduce noise in the signals generated by each of phototransistors Qi through Q₄. Further, difference amplifiers Di through D allow for the generation of an electrical signal conesponding to the leading edge (i.e., face) of a club passed over one or more of phototransistors Qi through Q . Connected to difference amplifiers Di through D are comparators Ci through C , which compare the outputs of each of difference amplifiers Di through D to a threshold voltage Vx. It is to be understood that other circuit configurations of club movement sensor 60 not depicted in FIG. 6 are considered within the scope of the present invention. In a prefened embodiment of the invention, 16 phototransistors are provided in club movement sensor 60 to produce a 16 bit digital signal in which one of the bits indicates the position of the club face.

FIG. 7 is a diagram showing operation of the club movement sensor 60. Club 30, having a face 31, is passed over phototransistors of the club movement sensor 60, shown illustratively as Qi through Q , generally along path 32 of a putting stroke. At a given point along the path 32 of the putting stroke, club 30 casts a shadow over one or more of the phototransistors of club movement sensor 60, turning same electrically off. As shown, club 30 casts a shadow over phototransistors Q₂ and Q₃, turning them to an off state, while phototransistors Qi and Q remain in an electrically on state, hi an illustrative embodiment, the on state of the phototransistors is indicated as a voltage of 0 volts, while the off state is indicated as a voltage of +5 volts.

Voltage outputs from each of phototransistors Qi and Q are then sent to difference amplifiers Di through D , wherein outputs from two of the phototransistors are processed by each of the difference amplifiers. When the input voltage of a first phototransistor connected to one of the difference amplifiers is lower than the input voltage of the second phototransistor, a negative voltage is produced. Conversely, when the input voltage of the first phototransistor is lower than the input voltage of the second phototransistor, a positive voltage is produced. Further, when the input voltages of the phototransistors are equal, zero voltage is produced. Thus, as shown in the illustrative embodiment of FIG. 7, voltage of zero produced by Qi and a voltage of +5 volts produced by Q₂ cause difference amplifier Di to emit a voltage of -5 volts. Outputs from each of the difference amplifiers Di through D are then sent to comparators Ci through C , and are compared thereby to a threshold voltage Vx. In a prefened embodiment of the present invention, Vx is 0.7 volts. Other values can be substituted for Vx. For input voltages that fall below Vχ₅ a negative voltage (i.e., -12 volts) is produced. Conversely, for input voltages that exceed V , a positive voltage (i.e., +5 volts) is produced. Thus, as shown in FIG. 7, a voltage of -5 volts provided by difference amplifier D_q, which is lower than Vx of -0.7 volts, an output voltage of -12 volts is produced by comparator . Accordingly, the position of face 31 of club 30 can be indicated by a single positive voltage produced by one of the comparators. Therefore, a voltage of +5 volts produced by comparator C₃ indicates the position of club face 31 amongst the plurality of phototransistors.

Outputs from the sensors of the present invention can be utilized to produce time traces conesponding to eye, club, and head movements. In a prefened embodiment of the invention, C++ and MATLAB programs are used to generate position and velocity graphs as functions of time for club movement, left eye movement, right eye movement, and head movement. The generated time traces/graphs can then be compared amongst golfers at varying skill levels to indicate the efficiency and accuracy of the subject golfer. It is well known that any general purpose computer, programmed by languages known in the art, can be used to produce the time traces.

It should be apparent to those skilled in the art that the present invention can be adapted to allow analysis and practice of all types of golf strokes, such as putting, driving strokes, iron stokes, chips, pitches, or other stokes. The apparatus of the present invention can be installed in commercial driving ranges, golf courses, or other practice locations, allowing golfers to quickly gauge the efficiency of their golf strokes and to receive feedback on practice strokes by returning real-time measurements of the strokes and comparing same to measurements of professional golfers. Further, the present invention can be adapted to allow practice and analysis of other sports involving stroke-like movements. EXAMPLE

The apparatus of the present invention was experimentally tested on twelve volunteers, divided into three groups according to skill levels. Individuals with handicaps between 0 and 9 were placed in the first group, and individuals with handicaps between 10 and 20 were placed into the second group. Novices were placed into the third group. Each group had four volunteers. Each subject made twenty 3- foot putts and twenty 9-foot putts using the present invention, and results for each of the volunteers were compared. It was found that the typical low-handicapper exhibited a small head rotation (i.e., clockwise as seen from top) during the backstroke, compensated for by a smooth eye movement (i.e., vestibulo-ocular reflex), wherein steady eye fixation on the ball was maintained. Head rotation appeared to be associated with a slight shoulder turn during the putting stroke, and occuned less frequently for 3 -foot putts but occasionally appeared for 9-foot putts. The typical mid- handicapper demonstrated a similar response pattern, but additionally exhibited saccadic eye movements (i.e., fast jumps in fixation) during the backstroke and at the time of impact. The typical novice golfer showed relatively large head rotations and compensatory eye movements, and exhibited frequent enatic eye fixations through the backstroke and during impact.

FIGS. 8 through 10 are graphs showing examples of measurements of club, eye, and head movement achieved by the present invention. FIG. 8 is a graph showing time traces of club movement during a putting stroke produced by the present invention. Club position, measured in centimeters, is graphed as a function of time, measured in seconds. Positive and negative club position values indicate movements toward or away from the hole, respectively. Position of the club is represented as a solid line, while velocity of the club is represented as a dashed line. The point of impact with the ball is illustratively represented as a club position value of 0, occurring between 1 and 1.5 seconds.

FIG. 9 is a graph showing time traces of eye movement during a putting stroke. Eye movements for both left and right eyes of the subject are indicated in the top and bottom graphs, respectively. Prior to capturing eye movement data, the subject fixated on three known locations (i.e., left end, middle, and right end of the club movement sensor 60 of the present invention), in order to provide adequate calibration data. Eye movement data acquired during the putt was then measured with reference to the calibration data, and eye position was recorded as displacement in centimeters of the left and right eyes along putting surface 80. The solid line of the graph indicates eye displacement in centimeters. Further, the dashed line indicates eye velocity.

FIG. 10 is a graph showing a time trace of head movement during a putting stroke. Prior to acquiring head movement data, the head movement sensor 60 was pre-calibrated to provide conversion from a measured voltage change to a conesponding angular rotation of the potentiometer shaft, which in turn conesponded to an angular rotation of the subject's head. This angle was then converted to a displacement of a hypothetical beam emanating from the center of rotation of the head, approximated by the position of the center between the two eyes of the subject, and measured in centimeters. As shown in the graph, head position is measured in centimeters from the center position of the head, and indicated as a solid line. The dashed line indicates head velocity.

FIG. 11a is a graph showing a time trace of club movement of an experienced golfer during a putting stroke. As can be seen, club movement is relatively smooth, with backward and forward movement being relatively uniform. These results can be compared to FIG. lib, which shows a time trace of club movement of a novice golfer during a putting stroke. Backward movement is noticeably larger than forward movement, and there is a lack of uniformity between forward and backward movements.

FIG. 12 is a graph showing simultaneous time traces of eye, head, and club movement during a putting stroke. The dotted line across the four graphs indicates the moment in time in which the ball is struck. Thus, using the present invention, realtime plots of head, club, and eye movement can be generated simultaneously and compared.

FIG. 13a is a graph showing simultaneous time traces of eye, head, and club movement of a novice golfer during a putting stroke. The point of contact between the club face and the ball is represented in the graphs as occurring after 2 seconds. As can be seen from the graphs, a considerable amount of eye movement for both the left and right eyes of the subject occuned prior to the point of contact. Further, forward and backward club movements are not uniform, as there is greater backward movement than forward movement. Additionally, the occunence of saccadic eye movement can be seen occurring prior to the putt.

FIG. 13b is a graph showing simultaneous time traces of eye, head, and club movement of an experienced golfer during a putting stroke. As can be seen, club, eye, and head movements for the experienced golfer appeared more uniform than the movements of the novice golfer, as shown in FIG. 13a. Club movements are also more uniform, with backward and forward movements being generally equal. Eye movements are significantly less than those of the novice golfer, and saccadic movements do not appear prior to contact between the club face and the ball. Additionally, head movement is reduced.

The present invention can also be utilized to determine the effect of various golf grips on putting performance. For example, club, eye, and head movements can be measured and compared for various golf grips, i.e., conventional, cross-hand, and single-hand grips. Results using these grips are shown in FIGS. 14-16.

FIG. 14 is a graph showing time traces of eye, head, and club^" movement when a conventional golf grip is used during a putting stroke. Time traces of club, eye, and head movements are shown for a typical 9 foot put using a conventional golf grip. For all traces, position and velocity are indicated by solid and dashed lines, respectively. The vertical dashed lines indicate the duration of the putt starting from the beginning of the backstroke and ending at the point of impact with the ball. FIG. 15 is a graph showing time traces of eye, head, and club movement when a cross-handed golf grip is used during a putting stroke. FIG. 16 shows time traces using the one-handed grip.

The results shown in FIGS. 14-16 can be analyzed using statistical methods to determine the effect of the various grips on putting. FIG. 17 shows results of statistical analysis of conventional, cross-hand, and one-handed grips used during 3 feet and 9 feet putts. The results show differences between the putting grips for various parameters, including height to the subject's eyes, putt amplitude, putt duration, percentage of putts made, and STD of left eye, right eye, and head movements. To determine whether the difference between the results in adjacent columns are significant (i.e., p < 0.1; H = 1), one-tailed t-tests were performed. Height to the subject's eyes was highest for one-handed grips, intermediate for conventional grips, and lowest for cross-handed grips. This can be attributed to the fact that one-handed subjects tended to stand more erect. Conversely, for cross- handed grips, the left hand is positioned lower on the club grip, thus lowering the left shoulder. Such a result tends to bring the head of the subject down as well, thus lowering the height of the head relative to the platform. The results for this category are the same for 3 and 9 foot putts.

Putt amplitude is not significantly different for the three putting grip styles for 3 foot putts. However, for 9 foot putts, amplitude for cross-handed grips are statistically significantly smaller than for either conventional or one-handed grips. This may be attributable to a restriction of right elbow motion in the backstroke, due to increased bending of the right elbow to compensate for a higher right hand position on the club.

Putt duration is longer for the one-handed grip than for either conventional or cross-handed grips, for both 3 and 9 foot putts. This may be due to the increased length of the swing arm (i.e., club plus hand and arm), in the one-handed putt. Hence, if one considers this as a pendulum motion, the increased length conesponds to an increase in the period of motion, resulting, in turn, in an increase in the duration of the putt.

The percentages of putts made appear to be higher for cross-handed grips than for either conventional or one-handed grips, for both 3 and 9 foot putts. However, such comparisons are not statistically significant, except for 9 foot putts where the percentage made is statistically significantly higher for cross-handed grip than for conventional grip (p = 0.006).

The STD of combined right and left eye movements is lowest for one-handed grips, intermediate for cross-handed grips, and highest for conventional grips, for both 3 and 9 foot putts. The results are all statistically significant except for the comparison between cross-handed and conventional grips for 3 foot putts (p = 0.312).

The STD of head movements is lower for one-handed grips, intermediate for cross-handed grips, and highest for conventional grips, for 3 foot putts. These results are statistically significant except for the comparison between one-handed grips and cross-handed grips (p = 0.151). However, for the 9 foot putts, there are no statistically significant differences among the putting grip styles. These findings suggest that head motion plays a more important role in shorter (i.e., 3 foot) putts than for longer (i.e., 9 foot) putts. Further, the results indicate that one-handed grips, and to a lesser extent, cross-handed grips, result in less head motion during the putt.

FIG. 18 is a photograph showing an embodiment of the present invention for analyzing head movement during a golf stroke using an accelerometer and wirelessly transmitting the acquired data. As previously mentioned, the present invention can be implemented using one or more devices for wirelessly transmitting head and eye movement data during the stroke, thereby obviating the need for interconnecting cables between the head and eye movement sensors and other apparatuses. For example, as shown in FIG. 18, the present invention can be modified to provide a system 100 for wirelessly measuring head movement data during a golf stroke. The system 100 includes a helmet 110, similar in design to the helmet 41 of FIG. 1. The word "helmet" is meant to cover any suitable mechanism for support sensing equipment including, but not limited to, a hat, a headband that fully or partially sunounds the head, a visor, etc. Attached to the helmet 110 are a head movement sensor 120, a battery back 130, and eye movement sensors 140.

Head movement sensed by sensor 120 is wirelessly transmitted to receiver 160, for remote analysis. Advantageously, the sensor 120 allows for the untethered acquisition and analysis of head movement data during a golfer's putting stroke, without requiring the golfer to align his or her head with a stationary device and keep same in place during measurement. Head movement sensor 120 comprises an accelerometer, transmitter, and associated circuitry for measuring head movement and transmitting same wirelessly to receiver 160 for remote analysis. Any other device that can be used to acquire head rotation data is considered to be within the scope of the present invention. Battery packs 130 and 150 can be used to provide a power source to power sensor 120 and receiver 160. A 3 volt power source has been found to be sufficient.

FIG. 19 shows the head movement sensor 120 of the present invention in greater detail. The sensor 120 comprises an accelerometer 121, a transmitter 125, an antenna 126, and a power source 130. These components can be mounted on one or more circuit boards. As shown in FIG. 19, two circuit boards are interconnected. The power source 130 is shown remote from the circuit boards but could be positioned thereon. As shown in FIG. 19, the accelerometer 121 is mounted on one of the boards, and the wireless transmitter 125 and antenna 126 on the other board.

In a prefened embodiment of the present invention, the accelerometer comprises an ADXL202 single chip accelerometer manufactured by Analog Devices, Inc., which provides a 167 Hz rectangular wave signal having a duty cycle proportional to the acceleration. The duty cycle represents the ratio of the pulse- width to the period, and is proportional to the acceleration of the device in each of two sensitive axes (i.e., X and Y axes). The dimensions of the device are 10.6 mm x 9.9 mm x 5.5 mm. Two outputs are provided, based on sensors aligned in the X and Y directions within the plane of the device. The device is useful for measuring tilt, and it uses the force of gravity as an input vector to determine orientation of an object in space. A particular axis (i.e., X or Y axis) is most sensitive to tilting deviations when the device is parallel to the earth's surface. The accelerometer is capable of measuring both dynamic acceleration (i.e., vibration) or static acceleration (i.e., gravity). It is to be understood, however, that other devices capable of measuring head movement are considered within the scope of the invention and may be utilized without departing from the spirit of the invention.

If the accelerometer 121 is positioned on top of a subject's head and oriented in such a way that the Y-axis of the accelerometer is pointed toward the sky and in the direction behind the subject, then the X-axis is approximately parallel to the earth's surface (and parallel to an imaginary line drawn between the two eyes), providing sensitivity to tilt of the X-axis. The tilt of the X-axis is a result of the rotation of the head. Indeed, in testing the device during putts, it was found that the X-axis is much more sensitive to rotational as opposed to translational (i.e., side-to-side) motions of the head. Thus, the accelerometer can be used to measure head rotation during a golf swing or a putting stroke.

Preferably the transmitter 125 is the TR-1000 916.50 MHz hybrid transceiver manufactured by RFM, Inc. The device is well-suited to short-range wireless data applications, can serve as either a transmitter or a receiver, and its dimensions are 10.2 mm x 7.1 mm x 2.0 mm. The transmitter can operate using either on-off keying (OOK) or amplitude-shift keying (ASK). The operation of the transmitter is basically transparent to the other components of the overall device. The input analog signal to the transmitter is directly reflected in the output analog signal of the receiver. The distance between the transmitter and receiver can be up to 100 ft depending on environmental conditions. Thus, the transmitter/receiver combination can be easily implemented in a laboratory, pro-shop or driving-range environment. It is to be understood, however, that other transmitters/transceivers known in the art can be utilized with the present invention.

Sensor 120 can be implemented as follows: the accelerometer 121 can be soldered onto a small circuit board 122 (2.5 mm x 4.0 mm), and appropriate components such as capacitors and resistors can be added. The transmitter 125 can be soldered onto another similar-size circuit board 124. The two boards 122 and 124 can be mated by means of male and female complementary connectors on the two circuit boards. Of course, a single board could be used. The sensor 120 can then be adhered to a small flat plastic member that is glued to a stem. The stem can then be screwed onto a female stem fixed on the helmet 110 of FIG. 18. The orientation of the sensor 120 is adjusted so that the X-axis of the accelerometer is approximately parallel to a hypothetical line drawn between the subject's eyes. The accelerometer signal is input to the transmitter, which then emits a radio frequency signal. The signal consists of a rectangular wave whose duty cycle is proportional to the head rotation acceleration. The receiver 160 of FIG. 18 receives the signal and relays the duty cycle signal to remote processing circuitry. Clearly, the construction of the sensor 120 can be simplified in accordance with what is known in the art.

When the duty cycle is received by receiver 160, it is necessary to process same to provide a signal conesponding to head movement data. An illustrative circuit 200 for providing such processing is shown in the schematic of FIG. 20. The received duty cycle signal is fed into input 205 of circuit 200. In stage 210, the signal is integrated to provide an acceleration signal conesponding to rotational acceleration of the subject's head during a putting stroke. Then, in stage 220, the signal is fed through a biasing and gain stage to permit adjustment of circuit 200 to the most sensitive level (i.e., by tweaking the potentiometer of stage 220). The signal is then integrated by an operation amplifier in stage 230 to provide a velocity signal, and then integrated once again by another operation amplifier in stage 240 to produce a head rotation position signal. A final gain stage 250 provides a larger head rotation voltage signal for input to a computer or other system for analysis and/or further processing. Thus, the circuit 200 allows for the production of a head rotation position signal at output 255 given a duty cycle signal at input 205. Other circuit configurations for providing head rotation position signals are considered within the scope of the invention.

FIG. 21 is a graph showing time traces of putter, eye, and head movement measured using the wireless head measurement apparatus of the present invention. As can be seen in the bottom trace of the graph, head movement information can be acquired by the accelerometer of the present invention, transmitted wirelessly, processed, and analyzed to produce a time trace of high accuracy conesponding to head position during the putting stroke. The angle of head rotation about the spine axis has been converted to an equivalent movement of an imaginary beam projected peφendicularly to the face of the subject and onto the putting platform of the present invention.

It should also be noted that wireless data acquisition and transmission equipment and techniques can be used to wirelessly transmit data acquired by the eye movement sensors of the present invention.

Having thus described the invention in detail, it is to be understood that the foregoing description is not intended to limit the spirit and scope thereof. What is desired to be protected by Letters Patent is set forth in the appended claims.

Claims

CLAIMS What is claimed is:

1. An apparatus for analyzing golf strokes comprising: a surface for supporting a golfer during a golf stroke; means for sensing position of a golf club head during the golf stroke; and a processor connected to the means for sensing position for producing measurements conesponding to position of the golf club during the golf stroke.

2. The apparatus of claim 1, wherein the means for sensing position of the club head comprises at least one photodetector anay.

3. The apparatus of claim 2, wherein the at least one photodetector anay comprises a plurality of photodetectors for detecting club head position and velocity.

4. The apparatus of claim 3, wherein the plurality of photodetectors comprises a plurality of infrared phototransistors.

5. The apparatus of claim 1, wherein the means for sensing position of the club head further comprises means for determining a position of a leading edge of the club.

6. The apparatus of claim 5, wherein the means for determining the position of the leading edge of the club produces a signal conesponding to the position of the putter.

7. The apparatus of claim 6, wherein the signal is sent to the processor for producing the measurements.

8. The apparatus of claim 1, wherein the means for sensing position of the club head is embedded in the surface.

9. The apparatus of claim 1, wherein the measurements are compared to measurements of golfers of different skill levels.

10. The apparatus of claim 1, wherein the measurements comprise time traces.

11. An apparatus for analyzing golf strokes comprising: a surface for supporting a golfer during a golf stroke; means for sensing movement of the golfer during the golf stroke; and a processor connected to the means for sensing movement for producing measurements conesponding to the movement of the golfer during the golf stroke.

12. The apparatus of claim 11, wherein the means for sensing movement comprises means for sensing head movement of the golfer during the golf stroke.

13. The apparatus of claim 12, wherein the means for sensing head movement comprises a potentiometer for measuring rotational head movement.

14. The apparatus of claim 13, further comprising a helmet for a golfer to wear, the helmet interconnected with the potentiometer for transferring the rotational head movement to the potentiometer.

15. The apparatus of claim 12, wherein the time trace indicates head movement of the golfer during the golf stroke.

16. The apparatus of claim 11, wherein the means for sensing movement comprises means for sensing eye movement of the golfer during the stroke.

17. The apparatus of claim 16, wherein the means for sensing eye movement comprises an infrared eye movement detector for sensing movement of the eyes of the golfer during the golf stroke.

18. The apparatus of claim 16, wherein the measurements indicate eye movement of the golfer during the golf stroke.

19. The apparatus of claim 11, wherein the measurements comprise time traces.

20. An apparatus for analyzing golf strokes comprising: a surface for supporting a golfer during a golf stroke; means for sensing position of a golf club head during the golf stroke; means for sensing movement of the golfer during the golf stroke; and a processor connected to the means for sensing position of the golf club and the means for sensing movement of the golfer, the processor producing measurements conesponding to sensed golf club position and sensed golf club movement during the golf stroke.

21. The apparatus of claim 20, wherein the means for sensing position of the club head comprises at least one photodetector anay.

22. The apparatus of claim 21, wherein the at least one photodetector anay comprises a plurality of photodetectors for detecting club head position and velocity.

23. The apparatus of claim 22, wherein the plurality of photodetectors comprises a plurality of infrared phototransistors.

24. The apparatus of claim 20, wherein the means for sensing position of the club head further comprises means for determining a position of a leading edge of the club.

25. The apparatus of claim 24, wherein the means for determining the position of the leading edge of the club produces a signal conesponding to the position of the putter.

26. The apparatus of claim 25, wherein the signal is sent to the processor for producing the measurements.

27. The apparatus of claim 20, wherein the means for sensing position of the club head is embedded in the surface.

28. The apparatus of claim 20, wherein the measurements are compared to measurements of golfers of different skill levels.

29. The apparatus of claim 20, wherein the means for sensing movement further comprises means for sensing head movement of the golfer during the golf stroke.

30. The apparatus of claim 29, wherein the means for sensing head movement comprises a potentiometer for measuring rotational head movement.

31. The apparatus of claim 30, further comprising a helmet for a golfer to wear, the helmet interconnected with the potentiometer for transferring the rotational head movement to the potentiometer.

32. The apparatus of claim 20, wherein at least one of the measurements indicates head movement of the golfer during the golf stroke.

33. The apparatus of claim 20, wherein the means for sensing movement further comprises means for sensing eye movement of the golfer during the golf stroke.

34. The apparatus of claim 33, wherein the means for sensing eye movement further comprises an infrared eye movement detector for sensing movement of the eyes of the golfer during the golf stroke.

35. The apparatus of claim 20, wherein at least one of the measurements indicates eye movement of the golfer during the golf stroke.

36. The apparatus of claim 20, wherein the measurements comprise time traces.

37. A method for analyzing golf strokes comprising: providing a surface for supporting a golfer; allowing the golfer to take a golf stroke; sensing movement of the golfer during the golf stroke; and producing measurements conesponding to the sensed movement during the golf stroke.

38. The method of claim 37, further comprising sensing head movements of the golfer during the golf stroke.

39. The method of claim 38, further comprising producing measurements conesponding to the head movements of the golfer during the golf stroke.

40. The method of claim 37, further comprising sensing eye movements of the golfer during the golf stroke.

41. The method of claim 40, further comprising producing measurements conesponding to the eye movements of the golfer during the golf stroke.

42. The method of claim 37, further comprising sensing position of a golf club during the golf stroke.

43. The method of claim 42, further comprising producing measurements conesponding to the position of the golf club during the golf stroke.

44. The method of claim 37, further comprising comparing the measurements of the golfer to measurements of golfers of different skill levels.

45. An apparatus for indicating movement of an object above a surface comprising: a plurality of sensors disposed on the surface; a plurality of difference amplifiers connected to the plurality of sensors; and a plurality of comparators connected to the plurality of difference amplifiers, the plurality of comparators producing a digital signal having multiple bits, wherein at least one of the multiple bits conesponds to a position of the object above the surface.

46. The apparatus of claim 45, wherein the plurality of sensors comprise a plurality of phototransistors .

47. The apparatus of claim 45, wherein the plurality of sensors are disposed within the surface and face generally upward.

48. The apparatus of claim 45, wherein the digital signal is 16 bits.

49. An apparatus for analyzing a golf stroke comprising: a sensor for measuring head movement during the golf stroke; and a transmitter interconnected with the sensor for wirelessly transmitting head movement data measured by the accelerometer.

50. The apparatus of claim 49, wherein the sensor comprises an accelerometer.

51. The apparatus of claim 49, further comprising a receiver for receiving the head movement data.

52. The apparatus of claim 51 , further comprising processing means connected to said receiver for producing head position information from said head movement data.

53. The apparatus of claim 49, further comprising means for sensing eye movement during the golf stroke.

54. The apparatus of claim 49, further comprising means for sensing putter movement during the golf stroke.

55. A method for analyzing a golf stroke comprising: measuring head movement during the golf stroke using a sensor, said sensor producing an output signal; and wirelessly transmitting said output signal for remote processing.

56. The method of claim 56, wherein the step of measuring head movement comprises measuring head movement during the golf stroke using an accelerometer and wirelessly transmitting an output signal of the accelerometer for remote processing.

57. The method of claim 53, further comprising: receiving said output signal at a remote location; and processing said output signal to provide head position information during the golf stroke.

58. The method of claim 57, further comprising producing a time trace using the head position information.

59. The method of claim 57, further comprising measuring eye movement during the golf stroke and transmitting said eye movement for remote processing.

60. The method of claim 57, further comprising measuring putter movement during the golf stroke and transmitting said putter movement for remote processing.