Title of Invention: Golf ball performance evaluation system
Abstract: 
A golf ball performance evaluation system includes an initial properties analyzing unit for measuring and analyzing kinetic properties of a golf ball immediately after the golf ball is hit by a golf club, and an in-flight properties analyzing unit for measuring and analyzing kinetic properties of the golf ball hit by the golf club during a flight on its trajectory. 

Detailed Description: 

BACKGROUND OF THE INVENTION 
 1. Field of the Invention 
 The present invention relates to a golf ball performance evaluation system and more particularly to a golf ball performance evaluation system for measuring and analyzing not only kinetic properties of a golf ball immediately after the golf ball is hit by a golf club but also kinetic properties of the golf ball which continues to fly on its trajectory (flying path) to draw a parabola. 
 2. Description of the Related Art 
 conventionally, flying properties (flight properties) of a golf ball are measured and analyzed by actually hitting the golf ball with a golf club to obtain some properties of the golf ball such as speed (initial velocity), angle (hitting angle), spin amount and the like which result immediately after the golf ball is hit, and when required, a trajectory and distance of the golf ball so hit are calculated through simulation using the properties of the golf ball obtained as described above (for example, refer to JP-A-10-206451). 
SUMMARY OF THE INVENTION 
 The properties of the golf ball measured by the aforesaid conventional system immediately after the golf ball was hit are, however, initial kinetic properties of the golf ball which resulted within an extremely short distance or a flying distance of less than 1 m after the golf ball was hit. Therefore, for example, assuming that a distance from the golf ball hitting position to the landing point is 210 m (about 230 yards), it has been difficult to estimate the shape of the trajectory and the behavior of the golf ball as far as the landing point from the initial kinetic properties of the golf ball. In particular, it has been unable to accurately grasp the behavior of the golf ball which is flying high on its trajectory. 
 On the other hand, it is known that the flying properties of a solid golf ball largely depend on mainly the repulsive properties of a core portion and a cover portion which make up the golf ball and the aerodynamic property attributed to dimples formed on the cover. Based on an assumption that a golf ball having superior flying properties flies to draw a trajectory which matches such flying properties, it is necessary to grasp how the repulsive properties based on physical properties of the golf ball constituent materials and the aerodynamic property based on the surface configuration including the arrangement of dimples affect the kinetic properties of the golf ball resulting immediately after it is hit and the kinetic properties of the golf ball which result before and after a peak position of the trajectory as well as at the peak position. To make this happen, the two types of kinetic properties have needed to be analyzed simultaneously. 
 An object of the invention is to provide a golf ball performance evaluation system which can evaluate the performance of a golf ball accurately by continuously measuring kinetic properties of the golf ball immediately after the ball is hit and kinetic properties of the golf ball during a flight on its trajectory by individual measuring units and analyzing outputted information. 
 According to an aspect of the invention, there is provided a golf ball performance evaluation system including an initial properties analyzing unit for measuring and analyzing kinetic properties of a golf ball immediately after the golf ball is hit by a golf club and an in-flight properties analyzing unit for measuring and analyzing kinetic properties of the golf ball hit by the golf club during a flight on its trajectory. 
 In the invention, in the initial properties analyzing unit, as the kinetic properties of the golf ball resulting immediately after the golf ball is hit, for example, initial velocity, hitting angle (an upward angle relative to a horizontal line, leftward or rightward angle relative to a reference line), backspin amount, sidespin amount and the like are measured and analyzed. 
 In addition, in the invention, in the in-flight properties analyzing unit, as the kinetic properties of the golf ball resulting when flying on its trajectory, for example, speed of the golf ball at an arbitrary position on the trajectory, angle of the trajectory including hitting or ascending angle and descending angle of the golf bail relative to the horizontal line, height of the golf ball at an arbitrary position including a maximum height from the horizontal like, leftward or rightward hitting angle of the golf ball and leftward or rightward deviation amount (distance) including a maximum deviation, various types of spins (backspin and sidespin) of the golf ball during flight on its trajectory, flying distance of the golf ball, flying time of the golf ball and the liker are measured and analyzed. 
 According to the golf ball performance evaluation system of the invention, it becomes possible to evaluate the performance of the golf ball comprehensively and accurately by continuously measuring, with respect to the golf ball which is hit to fly by the golf club, the kinetic properties of the golf ball resulting immediately after the ball is hit and the kinetic properties resulting at an arbitrary position on the trajectory by the individual measuring units and analyzing outputted information.


BRIEF DESCRIPTION OF THE DRAWINGS 
 FIG. 1 is a schematic perspective view of a golf ball performance evaluation system according to an embodiment of the invention; 
 FIG. 2 is a schematic front view of the same system with a display unit thereof removed; 
 FIG. 3 is an explanatory diagram showing a trajectory of a golf ball; 
 FIG. 4 is an operation explanatory diagram of the system shown in FIG. 1; 
 FIG. 5 is a diagram showing a monitor screen of the system shown in FIG. 1; and 
 FIG. 6 is a schematic diagram showing an example of a mark provided on a surface of the golf ball.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
 Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings, but the invention is not limited to the embodiment below. FIG. 1 is a schematic perspective view of a golf ball performance evaluation system according to an embodiment of the invention, and FIG. 2 is a schematic front view of the same system with a display unit thereof removed. 
 In FIGS. 1 and 2, reference numeral 10 denotes an initial properties analyzing unit. The initial properties analyzing unit 10 includes a sensor unit 12, a photographing unit 14 having two cameras placed to align with each other substantially horizontally in a direction in which a golf ball is hit to fly, and a properties analyzing unit 16 for analyzing and displaying photographed results. In addition, although not so illustrated, the sensor unit 12, the photographing unit 14 and the properties analyzing unit 16 are electrically connected. Additionally, in FIGS. 1 and 2, reference numeral 20 denotes an in-flight properties analyzing unit. The in-flight properties analyzing unit 20 includes a radar transmitter-receiver unit 22 and a display unit 24, and although not so illustrated, both the radar transmitter-receiver unit and the display unit are electrically connected. Furthermore, an elevation angle measuring unit 30 for measuring an elevation angle of the golf ball hit can be used additionally in the system of the embodiment. 
 Firstly, the initial properties analyzing unit 10 will be described. In FIGS. 1 and 2, a golf ball is set on a tee 42. In addition, the sensor unit 12 for detecting a passage of a head of a golf club 44 which is swung downwards to hit the golf ball is disposed to the rear of a target line of the golf ball 40. A primary sensor 12a and a secondary sensor 12b which are made up of an optical light emitting portion and light receiving portion are set at an interval of m1 (about 70 mm) in the sensor unit 12. A distance m2 between the secondary sensor 12b and the tee 42 is about 40 mm. 
 In addition, in the photographing unit 14 of the initial properties analyzing portion 10, two cameras are set transversely to photograph the behavior of the golf ball at an extremely initial part of a trajectory of the golf ball flying to draw a parabola shown in FIG. 3. Namely, a primary camera 14a is set in a position which is a distance m4 of 50 to 300 mm apart from the tee 42 and a secondary camera 14b is set in a position which is a distance m5 of 60 to 250 mm apart from the primary camera 14a. CCD cameras having a shutter speed of 1/10,000 to 200,000 of a second are preferably used for those cameras, and electronic flashes 14c, 14d are also preferably provided for the cameras, respectively (the flashes are shown only in FIG. 2.). 
 Next, a measuring method used in the initial properties analyzing unit 10 will be described using FIGS. 1 and 2 and an operation diagram shown in FIG. 4. Firstly, when the primary sensor 12a and the secondary sensor 12b detect a passage of the head of the golf club 44 which is swung downwards by the golfer, a passage time t1 is detected and a head speed is measured from a relationship between the distance m1 between both the sensors 12a, 12b and the time t1 so detected. Next, receiving a signal by the secondary sensor 12b, a trigger output ST acts on the primary camera 14a, the secondary camera 14b and the electronic flashes therefor, The trigger output ST measures in advance a plurality of head speeds to be applied, for example, and sets delay times t2 which correspond to these head speeds and a shutter interval t3 between both the cameras 14a, 14b. Images photographed by the cameras 14a, 14b are displayed on a monitor screen 18 of the properties analyzing unit 16. 
 Next, a golf ball initial kinetic properties analyzing method will be described. The initial velocity of the golf ball is measured based on a relationship between a time t3 taken for the golf ball hit to pass by the primary cameral 14a and the secondary camera 14b and the distance m5 between both the cameras 14a, 14b. The hitting angle of the golf ball (a vertical direction relative to the horizontal line), backspin amount and sidespin amount will be measured as below. 
 FIG. 5 shows images of the golf ball displayed on the monitor screen 18 of the properties analyzing unit 16 when the ball is hit. An image of the golf ball resulting when the ball is photographed from a side thereof by the primary camera 14a is displayed in a first portion 60 of the monitor screen 18, while an image of the golf ball resulting when the ball is photographed from the same side thereof by the secondary camera 14b is displayed on a second portion 62, and measured values are displayed in a third portion 64. In this embodiment, a mark M of isosceles triangle is imparted to a surface of the golf ball 40. The color of the mark M is preferably black or a dark color likened thereto in order to make the mark M prominent from the color (normally, white) of the golf ball. 
 In the initial kinetic properties analyzing method of the embodiment, with respect to the images displayed in the first portion 60 and the second portion 62 of the monitor screen 18, the external shape of the golf ball 40 which is shown as a white portion is extracted from the background thereof which is shown as a black area in the monitor screen 18 using a two-valued logic method (white or black). Following this, the mark M (black) within the external shape of the golf ball 40 which has been so extracted is then extracted using the same two-valued logic method. 
 When the extracting process is completed, a principal axis (an extension line containing the height) of the mark M is obtained, and furthermore, a search is made vertically from the principal axis so obtained to obtain a changing point where the color changes from black to white. The retrieval of changing point from black to white by the vertical search is carried out along the principal axis, and straight lines which pass through points/strings of these changing points or two oblique sides are obtained from results of the retrieval. Following this, a base line which intersects a median line of the two oblique sides at right angles is set outside the black block (the mark M), and a search is made from there towards the block side to obtain a base. When obtaining the oblique sides and the base, it is good to use curve fitting to obtain them in consideration of curving due to spherical surface. 
 When a triangle or the mark M is set by the image processing described above, three apexes are obtained from three sides, and a first apex A1, a second apex A2 and a third apex A3 are determined. Then, three-dimensional vectors of the first apex A1, second apex A2 and third apex A3 when regarding the golf ball 40 as a unit ball having a radius 1 are obtained from the images displayed in the first portion 60 and the second portion 62 of the monitor screen 18, and a rotational axis vector of the golf ball 40 is obtained based on a transition from the first portion 60 to the second portion 62 of the monitor screen 18, whereby a vector operation of the rotational axis vector and position vectors of the individual apexes is carried out to obtain an revolution amount of the golf ball. When the rotational axis vector and the revolution amount are obtained, a backspin amount and a sidespin amount of the golf ball 40. 
 In addition, a vertical positional relationship between the golf balls 40 displayed in the first portion 60 and the second portion 62 of the monitor screen 18 is measured, so that an upward hitting angle of the golf ball 40 can be obtained from a relationship between the inter-camera distance m5 (a horizontal distance) between the cameras 14a, 14b and the vertical positional relationship so obtained. Furthermore, a leftward or rightward deviation (a leftward or rightward hitting angle) of the golf ball hit can be measured based on the magnitudes of the diameters of the golf balls 40 displayed in the first portion 60 and the second portion 62 of the monitor screen 18. 
 Next, a measuring method used in the in-flight properties analyzing unit 20 will be described. The in-flight properties analyzing unit 20 includes the radar transmitter-receiver unit 22 and the display unit 24. In this embodiment, the radar transmitter-receiver unit 22 incorporates therein a transmitter which transmits radio waves towards the golf ball 40 projected and three receivers which receive radio waves which hit the golf ball 40 to thereby be reflected back therefrom. This radar transmitter-receiver unit 22 can be set a distance m3 of about 2000 mm to the direct rear of the golf ball 40 on the tee 42. On the other hand, the display unit 24 is electrically connected to the radar transmitter-receiver unit 22 and has a data operating function. 
 In this embodiment, to improve the reflection of radio waves by the golf ball hit to fly and facilitate the detection of a revolving state of the golf ball, a plurality of dimples 80 (five dimples in this embodiment) are, as shown in FIG. 6, for example, aligned in a straight line, and a metal-based paint 82 is applied to interiors of these dimples 80, so that a mark 84 having a superior radio wave reflecting property can be provided on the surface of the golf ball. This mark 84 made by the application of the metal-based paint can be provided in addition to the mark M of isosceles triangle. 
 The radar transmitter-receiver unit 22 transmits radio waves towards the golf ball 40 on the tee 42, as well as the golf ball 40 which is hit to fly and receives radio waves reflected by the rectilinear mark 84 of the metal-based paint, whereby the position of the golf ball, which varies every second, is measured with passage of time along a trajectory 90 shown in FIG. 3 which initiates from a golf ball setting position 92 where the golf ball is set on the tee 42 and ends at a landing point 96 via points including a point immediately after the golf ball is hit and a peak position 94, thereby making it possible to calculate the speed of the golf ball in an arbitrary position on the trajectory from the initial velocity which results immediately after the golf ball is hit to a speed thereof which results immediately before the golf ball lands at the landing point 96. 
 In addition, prior to any of the measurements with respect to the golf ball hit to fly, as shown in FIG. 3, the radar transmitter-receiver unit 22 sets a horizontal line X on the field independently and also sets a center line, thereby making it possible to measure the angle of the trajectory which includes the hitting angle and falling angle of the golf ball hit to fly relative to the horizontal line X so set and the height of the golf ball hit to fly in an arbitrary position on the trajectory which includes a maximum height h thereof from the horizontal line X. On the other hand, a leftward or rightward hitting angle of the golf ball as a deviation from the center line set and a leftward or rightward deviation amount (distance) including a maximum deviation can be measured. 
 Furthermore, various types of spins (backspin and sidespin) of the golf ball flying on its trajectory can be calculated by detecting radio waves reflected back from the rectilinear mark 84 of the metal-based paint. In this case, the various types of spins can be calculated correspondingly to various behaviors of the golf ball on the trajectory. Furthermore, a flying time as well as a distance d from the golf ball setting position 92 to the golf ball landing point 96 can also be calculated. 
 The in-flight kinetic properties of the golf ball on the trajectory measured and analyzed by the in-flight properties analyzing unit 20 are displayed on a monitor screen 26 of the display unit 24. 
 In this embodiment, the elevation angle measuring unit 30 shown in FIGS. 1 and 2 can be used as required. The elevation angle measuring unit 30 incorporates therein a camera, and the camera is preferably set substantially at the position of the tee with respect to the direction of the target line of the golf ball and substantially at a position equal to the height of the eyes of a human being with respect to the vertical direction. 
 The elevation angle measuring unit 30 can start photographing by making use of a trigger signal in the form of a sound generated when the golf ball is hit to fly or the trigger output ST which was described with respect to the measuring method used in the initial properties analyzing unit. The image of the golf ball hit to fly which changes every second is converted into an electric signal and is then sent to a display unit (not shown) which incorporates therein an operation unit or a personal computer, whereby not only the trajectory is displayed on the monitor screen but also an elevation angle (an ascending angle of the golf ball hit to fly relative to the horizontal line imaginarily drawn at the height of the camera or the height of the eyes of the human being), a leftward or rightward angle (deviation) relative to the center line, an ascending angular velocity and a descending angular velocity of the golf ball on the trajectory are calculated from photographed image signals and then displayed on the screen. 
 Thus, the data obtained by the initial properties analyzing unit 10, the in-flight properties analyzing unit 20 and the elevation angle measuring unit 30 are accumulated in the personal computer, and data necessary to analyze golf balls and golf clubs are processed into an easily usable form to be stored therein. 



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