Abstract:
A video image acquisition apparatus is disclosed. The apparatus has one or multiple digital cameras taking images of a flying golf ball created by at least two flashes or strobes of light on continuous video mode at a predetermined frame rate. Each image frame is then subtracted from the background and compared to determine the existence of the ball image in flight thus eliminating a dependency upon the camera shutter speed which must be synchronized with the flashes in prior art design. Furthermore, another video image acquisition apparatus is also disclosed that consists of at least two video cameras taking images of flying golf balls created by at least two flashes or strobes of light at predetermined time intervals. The apparatus then applies triangulate calculation of the two camera images to determine the exact physical locations of the flying golf balls in space at a given time of flight.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This utility patent application is based upon thus claims the priority of a provisional application Ser. No. 60/491,886, filed Aug. 1, 2003, by the same inventor. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to the field of electronic monitoring of high-speed events. More particularity, the present invention is directed to a video image acquisition apparatus for monitoring launch parameters of a launched sports object such as a flying golf ball.  
         [0004]     2. Description of the Related Art  
         [0005]     There are a number of apparatus or monitoring systems available since the 70&#39;s to measure high-speed events, in particular the launch parameters of flying golf balls. However, any apparatus or systems designed for measuring golf ball launch parameters will have some inherent limitations as well as optimal operational specifications. Over the years, high-speed camera and/or stroboscopic photography technologies have been used by a number of golf equipment manufacturers in the development process for golf ball and golf club such as the early invention of U.S. Pat. No. 4,158,853. As this type of technology has become increasingly prevalent for the measurement of golf ball launch parameters, the use of high-speed camera images has become more available and sophisticated such as described in U.S. Pat. Nos. 5,471,383, 6,241,622, 6,579,190 and 6,592,465.  
         [0006]     However, all these prior arts use similar approaches with high shutter speed and multi-shuttering camera or cameras to capture two-dimensional (2-D) fast flying ball images for launch parameter calculations. These require specialty and expensive high shutter speed or multi-shuttering camera and cameras to meet the image capturing requirements. Furthermore, the physical locations of the balls in space at any given time is not precisely measured as limited by the camera resolution and image distortion to be described later. Inherent measurement errors of these 2-D high speed camera and stroboscopic photography systems fall into two categories, namely camera hardware limitations (such as camera pixel resolution, focus, and lens distortion) and dynamic set-up variables (operator and system setup related variables such as camera height and distance to ball, camera leveling). As described herein, these components of measurement error have an interdependent relationship with one another, meaning that the accuracy of each parameter depends upon the accuracy of every other parameter.  
         [0007]     During golf ball launch, a 2-D camera system is often used to measure ball speed, launch angle, back-spin RPMs (revolutions per minute), and sometimes azimuth (in degrees of Push or Pull) and side-spin RPMs. By accurately measuring these parameters, algorithms shaped by field-testing and calibration can be used to predict golf ball flight (and roll). The purpose of the camera is to capture two or more successive images of a high-speed occurrence—a speeding golf ball moving up to 200 MPH (miles per hour) with a ball spin of up to 12,000 RPMs and launch angles from 0 to 65 degrees. These images are then processed by image recognition software or spatial mapping software that calculates the launch parameters of the shot based upon the movement of pre-defined markings on the golf ball over a series of images.  
         [0008]     To provide image processing software with meaningful images to accurately calculate golf ball launch parameters, the orientation of the camera along the x-, y-, and z-axes spatially, as well as the side to side and/or up and down position of the camera lens, for every starting and dynamic ball location, are critical. Otherwise, parallax views will severely limit the ability of a camera system to provide representative images of the golf ball launch parameters (a three-dimensional occurrence), hence limiting the accuracy of prediction of ball flight and roll with such systems. A good illustrative example of error from parallax view is when one tries to measure ball speed with a 2-D camera positioned at a perpendicular angle to the target line. To better understand the concept of parallax viewing error, imagine trying to read the gas gauge of our automobile from the passenger seat. Here, the fuel gauge does not appear the same way as it does to the driver whose sitting position faces the fuel gauge straight on. Trying to measure ball speed with a non-zero azimuth with a camera system works the same way.  FIG. 1  illustrates ball speed measurement error across positive (PUSH) and negative (PULL) azimuth angles. As one can see, only when the direction of the ball  5  is 90 degrees to the view angle of the camera  10  as in trajectory  1 , will one get reliable and accurate results with little or minimum error. In general, shots with a (+) azimuth, a PUSH traveling towards the camera  10  as in trajectory  2 , will appear to have a progressively higher ball speed than the actual, while those shots with a (−) azimuth, a PULL traveling away from the camera  10  as in trajectory  3 , will appear to have a progressively lower ball speed than the actual. In essence, under the circumstance of  FIG. 1 , the ball speed measurement calculation is dependent upon the azimuth angle of the ball  5 .  
         [0009]     Non-zero azimuth shots introduce parallax error also into the launch angle measurements of the camera  10  and this is demonstrated in  FIG. 2 . While the camera  10  will see the three shots depicted in the image as having the same launch angle, the shot with positive azimuth traveling towards the camera, having a trajectory  2 , will have an actual launch angle lower than the reported launch angle, while the shot with negative azimuth traveling away from the camera, having a trajectory  3 , will have an actual launch angle higher than the reported launch angle. In essence, under the circumstance of  FIG. 2 , the launch angle measurement calculation is dependent upon the azimuth angle of the ball  5  as well. Thus, unless a straight shot of 0 degrees azimuth is achieved, as signified by trajectory  1  of  FIG. 1  and  FIG. 2 , a camera system will have the effect of parallax error spill into both ball speed and launch angle calculations. Furthermore, when using correction formulas to compensate for the effect of azimuth errors on other parameters, the azimuth angle itself is often miscalculated due to difficulty of producing an accurate azimuth calculation. While some prior art attempts to reconcile the errors of ball speed and launch angle with an azimuth estimation and correction formulas based on size variations of the ball image are presented such as in U.S. Pat. No. 6,579,190, the limitation or pixel resolution of typically-used high shutter speed cameras results in an azimuth accuracy limited to +/−3 or 5 degrees, or equivalently a 6-10 degrees error variance by using single camera picture with multiple ball sizes or diameters captured with multiple shutter sequences. The physical diameter of a golf ball, as compared to the frame size required to capture multiple ball images in launch condition, limits the resolution to accurately estimate the ball azimuth angle. Simply put, a wrongful use of the azimuth correction formula can easily result in a 5+ MPH error in ball speed and a 3+ degrees error in launch angle. The present invention successfully provides better and improved solutions to the camera feature requirements and measurement of actual ball locations.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention relates to video apparatus for improved monitoring of the launch position, velocity and spins of a golf ball. By using stroboscopic photography with at least two flashes at a predetermined interval triggered by either acoustic, optical or electronic means and a digital CMOS (Complementary Metal-Oxide-Semiconductor) or CCD (charge coupled device) camera system, running at a continuous video mode, the present invention is capable of capturing all needed ball image information for computer processing, analysis and display of useful data. Furthermore, according to one embodiment of the present invention, a dual camera system with at least two cameras spaced out by a distance greater than the ball diameter and mounted preferably vertically to the ground is capable of providing much improved measurement of ball location in three-dimensional space at the times of the flashes, hence enabling more precise determination of the ball azimuth angle, ball speed, and launch angle.  
         [0011]     Preferred embodiments of the present invention are presented including a dual camera system interfaced with a data collecting computer, flashes with trigger mechanism located at a given distance to the ball flight trajectory path.  
         [0012]     To the accomplishment of the above and related objects, this invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific construction illustrated. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     Various other objects, features and attendant advantages of the present invention will become fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawing, in which like reference characters designate the same or similar parts throughout the several views, and wherein:  
         [0014]      FIG. 1  illustrates prior art ball speed measurement error across positive (PUSH) and negative (PULL) azimuth angles;  
         [0015]      FIG. 2  illustrates the parallax error of prior art launch angle measurements from non-zero azimuth shots;  
         [0016]      FIG. 3  illustrates a preferred embodiment and arrangement of the present invention wherein a dual camera system interfaced with a data collecting computer and flashes with triggering mechanism located at a given distance to a ball flight trajectory path;  
         [0017]      FIG. 4  illustrates two captured flying golf ball images each with a ball mark in a high speed camera or a stroboscopic photography system;  
         [0018]      FIG. 5  illustrates two different modes of camera shuttering design used in a stroboscopic photography system, they are (a) prior art high shutter speed camera which must synchronize its timing with the strobe or flash light pulses and (b) the continuous mode of operation which is independent to strobe or flash light pulses according to the present invention;  
         [0019]      FIG. 6  shows two ball images captured through the present invention of digital camera running at continuous video mode followed by applying image subtraction and enhancement technique;  
         [0020]      FIG. 7  illustrates an improved way of measuring the ball azimuth position with a dual camera system of the present invention;  
         [0021]      FIG. 8  shows ball images obtained from the dual camera system of the present invention, they are (a) ball image captured from the top camera and (b) ball image captured from the bottom camera;  
         [0022]      FIG. 9  illustrates a preferred camera arrangement of the present invention with vertical mounting; and  
         [0023]      FIG. 10  illustrates a horizontal camera mounting with associated creation of undesirable shift in the ball images. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     In the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will become obvious to those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, materials, components and circuitry have not been described in detail to avoid unnecessary obscuring aspects of the present invention. The detailed description is presented largely in terms of simplified orthogonal and perspective views. These descriptions and representations are the means used by those experienced or skilled in the art to concisely and most effectively convey the substance of their work to others skilled in the art.  
         [0025]     Reference herein to “one embodiment” or an “embodiment” means that a particular feature, structure, or characteristics described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Further, the order of process flow representing one or more embodiments of the invention do not inherently indicate any particular order nor imply any limitations of the invention.  
         [0026]      FIG. 3  illustrates a preferred embodiment and arrangement of the present invention wherein a dual camera system, including camera A  26  and camera B  28 , interfaced with a data collecting computer  30  and a flash light  24  with a flash light trigger  22  located at a given distance to a ball flight trajectory  18 . The data collecting computer  30  has a computer display  32  for displaying information. Two ball images  14  and  16  that reflect the stroboscopic images, created by two flashes emitted by the flash light  24  after triggering by the flash light trigger  22 , are referenced to the tee  20  location through a ball flight trajectory  18 .  
         [0027]      FIG. 4  illustrates two captured and displayed flying golf ball images  40  and  42  respectively with ball marks  40   a  and  42   a  in a typical high shutter speed camera or a stroboscopic photography system. Numerous ball flight parameters are calculated according to these ball images  40  and  42  immediately after launch. The ball marks  40   a  and  42   a  are of the shape of a bar or line and these are typically used in the art to provide back, side and rifle spins information. Distance d between the two ball images  40  and  42  is used to calculate the ball speed and the launch angle  37  is determined by the angle between ground  36  and ball flight trajectory  38  at the tee  20  location. As illustrated earlier, the actual ball speed and launch angle are highly dependent upon the exact ball location in three-dimensional space. Thus, accurate determination of the ball locations from the camera images becomes vitally important to extract meaningful and accurate ball flight data hence predicting ball flight trajectory and ball landing distance satisfactorily.  
         [0028]      FIG. 5  illustrates two different modes of camera shuttering design used in a stroboscopic photography system. Typical camera designs in stroboscopic photography use high shutter speed or multiple-shuttering which opens and closes successively in synchrony with the flashes or strobe lights and this is illustrated in  FIG. 5 ( a ) where the camera shutter is open when the flashlight is on and close when the flashlight is off. As the conditions of ball launch require the time interval between flashes to be very short, in the range of a couple of milliseconds, the camera shutter speed or image capturing speed need to be correspondingly fast and more often to be specially designed or customized at a much higher camera cost. The present invention, on the other hand, bypasses the use of multi-shuttering or high shutter speed camera design and, instead, uses a digital camera under a continuous video mode at a low frame rate and this is depicted in  FIG. 5 ( b ). Thus, under the present invention the shutter and frame speeds of the camera become irrelevant. Additionally, by using digital frame background subtraction and freezing and recognizing the ball images, one can achieve the same result by using almost any type of digital cameras hence drastically reducing the camera feature requirements and lowering the camera cost.  FIG. 6  shows two typical ball images  44  and  46  captured through a continuous video mode followed by applying image subtraction and enhancement technique.  
         [0029]      FIG. 7  illustrates an improved way of measuring the ball azimuth position with a dual camera system, having a camera A  26  and a camera B  28 , of the present invention. With the orientation of  FIG. 7 , the ball azimuth position means the left and right position of the golf ball. In the case of a prior art such as U.S. Pat. No. 6,579,190, a single camera  50  is used to capture ball size images. A comparison of the ball size (i.e., the ball diameter bd) is then applied to determine the displacement of ball in the azimuth direction (i.e., PUSH or PULL), distance daz. As the ball diameter bd is relatively small, about 1.68 inches, the azimuth displacement daz does not create a significant difference of the camera viewing angle and this is denoted as Angle 1. Hence such a small viewing angle difference results in a low resolution of the determination of azimuth angle. However, in the case of the current invention as illustrated in the lower part of  FIG. 7 , the same azimuth displacement daz in our vertically spaced dual camera system, with an inter-camera distance dc greater than the ball diameter bd, creates a much more significant difference of the camera viewing angle Angle 2 and this in turn provides a much higher resolution of the determination of azimuth angle hence increasing the measurement accuracy of all major ball launch parameters such as the ball speed and launch angle. Furthermore, no ball marking is required here as the ball position is determined by using the geometric center of the ball image and this provides a solid reference and better defined image boundary in determining the actual ball location regardless of any variations in the viewing angle or the distance and the current invention is much less sensitive to variations in the external lighting condition, focusing and blurring commonly associated with the round edges of the ball. This is very different from both the single camera approach used in U.S. Pat. No. 6,579,190 and the horizontally mounted dual camera approach used in U.S. Pat. No. 5,471,383 where multiple and patterned reflective dots specially marked on the ball are used.  
         [0030]      FIG. 8  shows some typical ball images obtained from the dual camera system of the present invention.  FIG. 8 ( a ) shows the ball images captured with camera A  26  while  FIG. 8 ( b ) shows strobe or flash light illuminated ball images captured with camera B  28 . Notice that the X-axis locations of the ball images are relatively the same in both pictures.  
         [0031]      FIG. 9  further illustrates a preferred camera arrangement of the present invention with vertically mounted camera A  26  and camera B  28 . As illustrated, the two camera images obtained from the vertically mounted dual camera system present another significant improvement in that one can visualize that the ball horizontal positions (i.e., along the X-axis direction) between the two cameras are relatively the same in reference to the edges of the picture. This is so as the view angles of the two cameras are aligned along the X-axis and the difference in their view angles mainly appears along the Y-axis. Thus, this vertical arrangement of the two cameras  26  and  28  is important as the locations of the first ball image  14  and the second ball image  16  are sensitive to the ball speed and launch angle for typical low angle golf shots from drivers and low irons (e.g., in a range from a few degrees to may be 20 degrees).  
         [0032]     On the other hand, a horizontal camera mounting of camera A  56  and camera B  58  creates unnecessary shift in the ball images and this is illustrated in  FIG. 10 . Specifically, the ball image locations along the X-direction are highly sensitive to the viewing angles of the cameras  56  and  58  and, which are also dependent on the ball speed where its X-axis speed component is much higher than its Y-axis component for typical ball launch conditions of low angle shots (e.g., from drivers or low irons). As a result, complicated viewing angle and special corrections become necessary when the corresponding ball image locations are separated too far apart along the X-axis as illustrated in  FIG. 10 . Hence the horizontal camera mounting of the dual camera system is less preferred due to its associated problem of X-axis ball image separation.  
         [0033]     Actual field and calibration test have been conducted to validate the effectiveness of the current invention and a brief summary of such tests is listed in Table 1 that demonstrates the effectiveness and usefulness of the current invention.  
                                                                                                                                 TABLE 1                           Actual Field Test Data With Current Invention                Actual Estimated   GA CAM Results                Carry           Carry               Ball   Launch   Back-   Side       File   Dis-   Off-   Short   Dis-   Off-   Short   Azi-   Speed   Angle   spin   spin       Name   tance   line   Shape   tance   line   Shape   muth   (rph)   (deg)   (rpm)   (rpm)                    Drivers                                                   BRFast02   245   −5   0   251   7   0.5   −4   160   11.1   3172   625       BRFast03   230   30   3   253   12   0.5   −4   163   10.5   3355   779       BRTM01   225   30   2   244   20   0   4   147   12.6   1812   83       BRTM02   235   5   1   246   12   0   3   149   13.6   1629   18       BRTM03   230   −30   −1.5   238   −33   −0.5   −6   150   10.7   1098   −276       BRHook02   185   −50   −2   191   −52   −2.5   −6   157   11.3   3307   −1448       BRHook03   240   −25   −1   195   −17   −1.5   5   156   10.5   2508   −1492       BRSlice01   250   15   1   260   15   1   −6   159   8.5   1689   1035       BRSlice02   235   25   1.5   224   38   1.5   1   141   12.9   2325   1088       BRSlice03   235   25   1.5   245   13   1   −2   148   14   1985   595       6-iron       6iTM01   160   15   0.5   150   −1   0   −1   110   15.3   6092   86       6iTM02   165   −10   −0.5   162   −4   −0.5   3   117   15.7   6607   −580       6iHookTM01   160   −30   −3   138   −30   −0.5   −7   111   14.1   6480   −878       6iHookTM02   165   −20   −2   156   −10   −0.5   0   112   15.6   5339   −494       6iSliceTM01   155   10   1.5   150   9   0.5   2   113   16.2   7480   257       6iSliceTM02   160   2   0   144   −36   −0.5   −12   106   15.5   6722   −431       Sand Wedge       SW01   105   −5   0   102   16   0.5   14   82   35.7   3581   −828       SW02   100   −5   0   97   −11   −1.5   0   77   33.4   2767   −1380       SW03   100   0   0   91   −11   −1   −1   80   36   3160   −1172       SW04   80   5   0   89   5   0   5   76   38.4   4216   −225       SW05   100   0   0   101   −6   −0.5   1   82   36   2326   −717                  
 
 For example, with a driver of BRFast02, an Actual Estimated (current invention) Carry Distance of 245 is obtained versus a reference from GA CAM Results of 251. For a second example, with a 6-iron of 6iSliceTM01, an Actual Estimated (current invention) Carry Distance of 150 is obtained versus a reference from GA CAM Results of 155. 
 
         [0035]     A video apparatus for improved monitoring of various launch parameters for a golf ball is described. Using an exemplary embodiment of stroboscopic photography with at least two consecutively triggered strobes or flashes and a digital camera system running at a continuous video mode, the present invention is capable of capturing all needed ball image information for processing, analysis and display of useful data. Furthermore, another embodiment of vertically arranged dual camera system with at least two cameras is also described for providing improved measurement of ball location in three-dimensional space at the times of the flashes. However, for those skilled in this field, these exemplary embodiments can be easily adapted and modified to suit additional applications without departing from the spirit and scope of this invention. Thus, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements based upon the same operating principle. The scope of the claims, therefore, should be accorded the broadest interpretations so as to encompass all such modifications and similar arrangements.