IN THE UNITED STATES PATENT AND TRADEMARK OFFICE APPLICATION FOR PATENT
TITLE: Golf Ball Flight Monitoring System
ATTY DOCKET: OSI-2300
Background of the Invention
1. Field of the Invention
The invention relates to a method and system for monitoring the
flight of a golf ball after impact with a golf club head, and particularly to
computer-controlled estimation of golf ball flight, impact timing and
transfer efficiency characteristics.
2. Discussion of the Related Art
Golf swing and golf ball flight monitoring have been used as tools
for golf instruction and for testing golf equipment such as golf clubs and
golf balls for many years. Such details as club head angle and club speed
at impact with the ball, as well as club take-away and downswing path,
are known to be crucial in determining ultimately important ball flight
characteristics, such as distance, direction, backspin and ball flight
curvature after impact. However, a golf swing is simply too fast in real
time for clear human observation of its many subtle features. High speed cameras and/or other sensors have been used to sense
and record data about the golf swing and/or initial ball flight
characteristics. The data is often displayed for slow speed analysis of a
golfer's form during the swing by an instructor and/or the golfer him or
herself. The position of the golfer's shoulders, hips, legs and/or head, as
well as his or her arms and hands, throughout the golf swing have been
captured on high speed still, video and television cameras either in a
series of still frames or in videos or movies replayable in slow motion.
Some such techniques are described, e.g., at U.S. patents no.
4,71 3,686, 5, 1 1 ,410 and 5,210,603.
Besides capturing the data described above of the golfer's form, data of the path of the golf club head during the swing and initial
characteristics of the golf ball in flight after impact with the club head are
often used. These latter data are more often used for determining total
ball flight characteristics such as distance, direction and curvature, rather
than the golfer's form, and are arguably more relevant factors than form
for determining the performance and effectiveness of a golfer's swing.
Moreover, equipment such as the golf club and golf ball being used can
be tested using these latter data, whereas the golfer's form really doesn't
affect such performance of the golfer's equpiment. Computer processors
running software algorithms are often used for calculating or more of the
above-mentioned features or others of the complete ball flight from the
sensed and recorded data. A series of United States patents assigned to Acushnet Company,
makers of Titleist™ golf equipment show and describe various techniques
and equipment for testing and determining golf club and golf ball
performance using measured pre-impact and post-impact characteristics
of the golf club and golf ball. These patents include U.S. patents no.
4,063,259, 4, 1 36,387, 4, 1 58,853, and 5,471 ,383.
For example, a pair of light source-photodetector pairs are
positioned as described in the '259 patent at spaced-apart locations
alongside the plane of the golfer's swing. Light emitted by each light
source is received by its corresponding photodetector unless an object
breaks the line of the emitted light to the detector. As the golf club head
nears the golf ball in a test method according to the '259 patent, the club
head swings through the line of sight of a first detector to the emitted
light from its corresponding light source. When this happens a signal is
sent to a camera shutter to open. Just before the club head impacts the
golf ball, a second line of sight of a second detector and its corresponding
light source is broken. At this time, a second signal causes a xenon lamp
to flash such that the reflected light is captured by the camera whose
shutter was previously opened.
Next, a microphone captures the sound of impact of the golf club
head with the golf ball. This acoustic signal is amplified and used as a
trigger for a second xenon lamp to flash such that a post impact image of
the golf ball is captured by the camera as shutter remains open. The
same amplified acoustic signal is sent through a delay and is used as a trigger for a third xenon lamp to flash such that another image post-
impact image of the golf ball in flight is captured by the camera. Shortly
thereafter the shutter of the camera is closed, and a still frame having
three images is stored on a film.
The use of a microphone to detect an acoustic signal requires
setting up and maintaining of the microphone, as well as precise
positioning and calibration separate from the optical components of the
system. Also, the sound of impact of the particular golf ball and club at
the test station where the microphone is being used has to be
distinguished from other club-ball impacts going on in the vicinity of the
microphone as well as from other sounds emanating from and around the
test area. It is desired to have a golf ball flight monitoring system that
does not use an acoustic photoflash trigger, and instead preferably uses
all photosensitive equipment.
The film including the three temporally successive images of the
golf ball reveals some useful initial characteristics of the flight of the golf
ball. For example, the initial launch angle and velocity can be determined
from the center of gravity positions of the successive images of the golf
ball, and the known time duration between the capturing of the second
and third images on the film, respectively. A mark placed on the ball prior
to performing the test can be used, as described at the '259 patent, to
reveal the amount of backspin initially imparted to the ball by the club
head. This initial backspin is determined based on how much the mark is
observed to have rotated in the plane of the film from the first to the second and from the second to the third images of the ball captured on
the film.
The small single mark described and shown in the '259 patent may
not be visible if side spin causes the mark to rotate to the "dark" side of
the ball, i.e., away from the camera side of the swing path. It is also
difficult to distinguish the backspin from the sidespin imparted to the ball
using the small single mark.
Lynch et al. were not concerned with sidespin in their description in
the '259 patent because a mechanical golfer was used that presumably
did not impart any sidespin to the ball at impact. Also, the mechanical
golfer was presumed to hit the ball straight ahead with each test swing so
that the initial direction of the golf ball was not considered as a factor in
any of the tests described in the '259 patent. Moreover, it is understood
that the '259 patent is drawn to equipment testing and not to analyzing
swing characteristics of a golfer. Thus, such ball flight characteristics as
the amount of fade or draw (or hook or slice, as the case may be) that a
golfer is achieving due to the sidespin the golfer is imparting at impact, or
the initial direction of the ball struck by the golfer, are not addressed in
the '259 patent. It is desired to have a ball flight monitoring system and
method that does determine ball flight characteristics based in part on the
initial horizontal direction of the golf ball's flight and the initially imparted
sidespin on the ball, in addition to the initial vertical flight conditions and
backspin on the ball. Each of the '387, '853 and '383 patents describes the use of one
or more highly reflective marks on the golf ball for determining initial post-
impact spin characteristics of the golf ball. Using subsequent images of
the one or more spots, each of these patents sets forth some description
of how to determine the complete spin characteristics of the golf ball, and
not simply the backspin as discussed above with respect to the '259
patent. However, the one or more spots may again not be visible to the
camera if they are rotated to the dark side of the ball when the image is
captured on film.
The '387 and '853 patents disclose to position three cameras or
photosensors each at ninety degree spaced locations around the golfer for
detection of the mark or marks wherever they may turn around the golf
ball. The three photosensors cannot be combined to achieve a single
planar image of the initial flight of the ball and the data captured by the
three photosensors is processed according to a complex algorithm that
factors the rotationally spaced locations of the sensors. Also, the angular
spacings of the sensors has to be very accurate or the calculated spin
characteristics of the ball will be unreliable. It is desired to have a method
and system for determining the complete initial spin characteristics of the
golf ball without having to sense marks on the ball in more than a single
observation plane.
The '383 patent sets forth a method for determining the total spin
imparted to the golf ball using six highly reflective marks or spots on the
ball and capturing their relative motions at successive temporal points within a single film frame. Data of the relative positions of the six marks
as captured on the film is converted to data directly related to the total
spin on the ball using a complex algorithm as described in the '383
patent. However, any one or all of the marks could again be rotated
during a real golf swing to the dark side of the ball in which case the
calculations would fail because the input data would be incomplete.
Gobush et al. are again concerned in the '383 patent with
equipment testing, and not golf swing analysis, and thus the mechanical
golfer used in the tests described in the '383 patent never imparts an
amount of sidespin to the ball sufficient to cause any of the marks to
rotate to the dark side of the ball before all of the camera images are
captured. It is desired to have a system and techniques for determining total spin imparted to a golf ball notwithstanding the degree of sidespin
on the ball.
The field of golf swing analysis is also understood in the present
invention to be lacking systems and techniques that measure and/or
determine or calculate and utilize data of the golf club head prior to
impact with the ball in conjunction with initial flight characteristics. Such
pre-impact club head data is desired, e.g., for determining energy transfer
efficiency between the club and ball, whether any sidespin or horizontal
ball directional characteristics are imparted by club head angle or swing
path characteristics, and for obviating the need for acoustic sensing of
impact for triggering image capture. It is also recognized in the present
invention that such a desired system and techniques would be useful for golf swing analysis as well as for testing equipment, including such
testing for determining the unique equipment specifications of particular
golfers depending on their individual
swing characteristics.
It is therefore an object of the invention to provide a golf ball flight
and golf swing monitoring system and technique wherein pre-impact
swing plane direction and head angle characteristics of the take away and
downswing of the golf club are measured and analyzed.
It is a further object of the invention to have a system and
technique for determining the total initial spin imparted to a golf ball,
including backspin and sidespin, and also preferably the three-dimensional
initial flight direction of the golf ball after impact with a golf club using a
single frame including multiple temporally successive images.
It is also an object of the invention to have a golf ball flight and golf
swing monitoring system and technique that combines pre-impact swing
characteristics with initial flight conditions of the golf ball to determine
transfer efficiency characteristics.
It is another object of the invention to provide a system and
technique for monitoring and analyzing initial ball flight characteristics
using a trigger for precisely timing the capture of temporally successive
images. Summary of the Invention
In accord with the above objects, a first aspect of the invention
includes an apparatus for monitoring characteristics of a golf swing path
and/or club head angle. The apparatus includes first and second arrays of
photosensors. Each array includes multiple sensors arranged at an angle
to the swing path. Preferably, the sensors are arranged substantially
orthogonally to the swing path. The first and second arrays are spaced-
apart from each other substantially in a direction along the swing path.
The sensors each receive a light signal unless the club head is located
over the sensor wherein the club head blocks the light signal.
A processor running a software program is configured for
calculating the swing path and/or club head angle based on the monitored
light signals of the sensors of the first and second arrays operated during a golf swing. The club head speed may be calculated based on the time
between the blocking of light signals for sensors in the first and second
arrays. The swing path and/or club head angle may be calculated based
on which sensors of one or both arrays are blocked and on the timing
between the blocking of the sensors of at least one array.
In a second aspect of the invention, multiple temporally successive
images of a golf ball after impact with a golf club are captured for
comparison preferably using a computer processor. The golf ball has a
continuous and preferably linear or substantially linear marking on its
surface that at least halfway circumambulates the golf ball such that the
marking is apparent within each image. The backspin imparted to the golf ball by the impact with the golf club head is then calculable based on a
comparison of the positions of the markings between two or more of the
images. Preferably, a linear estimation of the markings at each image is
first calculated and the backspin calculated based on the angle between
the markings on the two or more images. The sidespin is preferably
calculated based on the curvature of at least one of the markings.
In a third aspect of the invention, a photosensor is positioned a
known distance before the impact position of the golf club with the ball.
When a light signal received by the photosensor is blocked by the golf
club, a trigger signal is sent to a lamp that flashes a predetemined time
after receiving the trigger signal for capturing an image of the ball after
impact by a camera detector. Preferably, two spaced-apart sensors are
positioned before the impact position and the timing between the
successive blocking of the two sensors is used to calculate the club
speed prior to impact. The timing of the flash of the lamp is determined
based on this timing between the successive blockings of the two sensors
such that the ball is optimally positioned within the viewing range of the
camera.
In a fourth aspect of the invention, multiple images of the golf ball
after impact with the golf club are captured by a camera preferably as
described above. The computer processor determines the diameter of
two or more images of the golf ball. Based on the diameters of the two
or more images, the processor determines the three-dimensional velocity
of the ball including the initial horizontal direction of the flight of the ball. Brief Description of the Drawings
Fig. 1 a schematically shows a perspective view of a ball flight
monitoring system including an impact zone analyzer arranged on a hitting
mat.
Fig. 1 b schematically shows preferred electrical connections for the
system of Fig. 1 a.
Fig. 1 c schematically shows an overhead view of the impact zone
analyzer of Fig. 1 a.
Fig. 2 shows a display view illustrating golf club take away and
downswing paths and club head angle determined based on data obtained
from sensors of the impact zone analyzer of Fig. 1 .
Fig. 3a shows a display view of multiple temporally successive
images of a golf ball having a marking utilizing principles of the present
invention.
Fig. 3b shows a display view of multiple temporally successive
images of the golf ball having the marking of Fig. 3a, and software
generated linear and circumferential extrapolations based on the images.
Fig. 4a shows an overhead view representing total golf ball flight
characteristics calculated based on the images and extrapolations shown
in Fig. 3b.
Fig. 4b shows a side view representing total golf ball flight
characteristics calculated based on the images and extrapolations shown in Fig. 3b. Detailed Description of the Preferred Embodiment
Fig. 1 a schematically shows a perspective view of a ball flight
monitoring system including an impact zone analyzer 2 arranged on a
hitting mat 4. The impact zone analyzer 2 is imbedded within the hitting
mat 4 such that the surface of the analyzer 2 is substantially coplanar
with that of the hitting mat 4. The analyzer 2 is connected with a
computer processor 6 such that data signals may be sent to the computer
6 from the analyzer 2. Although a direct connection 7 is shown between
the analyzer 2 and the computer 6, the analyzer 2 may be indirectly
connected to the computer 6 through ball flight capture device or system
22, described below.
The analyzer has a first row 8 and a second row 10 of sensors 1 2
located behind a golf ball 14 on a tee 1 6. Preferably, each row 8, 10 has
around twelve sensors 1 2. The sensors 1 2 are preferably photosensors
such as light sensitive diodes or CCDs. The golf ball 14, of course, does
not have to be located on the tee 1 6. The analyzer 2 is preferably
conventionally connected to the computer 6 such that data representing
the amount of light that each sensor 1 2 receives throughout the duration
of a test golf swing may be received by the computer 6 from electronic
circuitry (not shown). The circuitry may be internal to the analyzer 2 or
external to the analyzer 2 such as within the ball flight capture device 22
that is connected to the analyzer 2, or otherwise. Although not shown, preferably an overhead lighting arrangement illuminates the hitting mat
and especially the first and second rows 8 and 10 of sensors 12.
A directional arrow 1 8 and footprints 20 are merely shown in Fig.
1 a to give the reader perspective as to where a golfer would be standing
during a test swing and what direction the golf ball would generally be
heading after impact with a golf club head of a golf club being swung by
the golfer.
The ball flight capture device 22 is located in front of the ball 14 on
the tee 1 6 across from where the ball 14 will be located in the air a short
time after impact with the golf club head. The device 22 includes a
camera 24 and one or more flash lamps, and preferably three flash lamps shown in Fig. 1 a as a first flash lamp 26, a second flash lamp 28, and a
third flash lamp 30. The device 22 is connected to the computer 6 and
preferably to the analyzer 2, as shown. Each of the device 22 and the
analyzer 2 may be connected to the computer either directly or through
other connections such as from the ball capture device 22 through the
analyzer 2 to the computer 6, or vice-versa.
Fig. 1 b schematically shows preferred electrical connections
associated with the ball flight monitoring system 100 of the present
invention. The ball capture device 22 has a cable connection labeled
"CPA cable" 32 which extends to the analyzer 2 on the hitting mat 4.
Three cable connections to the computer 6 from the ball flight capture
device 22 are labeled "cable 1 " 36, "cable 2" 38 and "cable 3" 34. The
computer 6 runs a software program specifically designed for processing input data from cables 34, 36 and 38, and may be otherwise a
conventional personal computer 6 including typical peripheral components
as shown.
Fig. 1 c schematically shows an overhead view of the impact zone
analyzer 2 including the ball 14 on a tee 1 6 prior to impact with a golf
club head from the right and a first row 8 and a second row 10 of
sensors are also visible in Fig. 1 c. Each of the sensors 1 2, the circuitry of
the analyzer 2 and the software running on the computer 6 (Figs. 1 a-1 b)
are preferably configured for distinguishing between when a golf club
head is over the sensor 1 2 and when the golf club head is not over the sensor 1 2. This is done by detecting when the overhead light is shining
on the sensors 1 2 and when a shadow is over the sensors 12 due to the
presence of the club head. That is, when the golf club head is not over a
particular sensor 1 2, then light from the overhead source is shining directly onto the sensor 12 yielding, e.g., a positive detection of the light
by the particular sensor 1 2. When the golf club head is over a particular
sensor 1 2, then light from the overhead source is blocked from directly
shining onto the sensor 12 yielding, e.g., a negative detection of light
from the overhead source by the particular sensor 1 2, or the detection (by
not detecting the direct light) of the shadow.
The swing path of the golf club and the angle of the club head just
before impact can be monitored using the first and second rows 8, 10 of
sensors 1 2. That is, based on the temporal order and/or duration or
degree of blocking of the individual sensors 1 2 during a test golf swing, the take away and downswing paths and the club head angle can be
monitored and displayed for evaluation. For example, if the center portion
of the club head is sensed as going over the sensor 1 2c and then the
sensor 1 2a, the swing is monitored as being somewhat inside out and the
impact with the ball maybe somewhat off the toe of the club, whereas if
the center portion of the club head is sensed as going over the sensor
1 2d followed by sensor 1 2b, then the impact would be monitored as
being of the heel of the club. Also, if the sensor 1 2a were blocked before
the sensor 1 2b of the second row 10 during the downswing, then the
club head angle would be detected as being somewhat open at the
second row 10 of sensors 12, whereas if the sensor 12b were detected
as being blocked before the sensor 1 2a, then the club head angle would
be detected as being somewhat closed at the second row 10.
Advantageously, the particular head angle and particular swing path can
be determined as well, and not just the general features described in the
general terms used in the above examples. The flashlamps 26, 28 and 30
and the camera 24 shown in Fig. 1 a are included in the embodiment of
Fig. 1 d, and are discussed in detail below.
Fig. 1 d illustrates an alternative ball flight monitoring system to the
system including the analyzer 2 illustrated at Fig. 1 a. The alternative
system does not include the analyzer 2 of the system of Fig. 1 a, but does
include the computer 6 and the ball flight capture device 22 described
above. Preferably two club sensing devices 39a and 39b for determining
club head speed and for triggering or initiating a process leading to the triggering of the camera 24 and/or the flash lamps 26, 28 and 30 is
provided in this alternative embodiment.
The sensors 39a and 39b are configured to detect when the club
head crosses in front of them, such as by crossing the imaginary lines L1
and L2 shown in Fig. 1 d for illustrative purposes. The sensors 39a and
39b may be photo or motion sensitive or otherwise for detecting the
precise time when the club crosses the imaginary lines L1 and L2. At
least one of the sensors 39a or 39b is preferably used for triggering the
camera 24 and lamps 26, 28 and 30. The system used input from
sensors 39a and 39b in determining the club head speed by analyzing the
time difference between when the imaginary lines L1 and L2 are crossed by the club head. The club speed is in turn used to estimte the time until
the ball will pass into the image field of the cmera 24. Using this estimated time, the system will calculate when to shutter the camera 24
and to flash the lamps 26, 28 and 30 to capture images of the ball with
the camera. Alternatively, a default or average timing is used from the
receipt of the trigger signal by the computer 6 and/or ball flight capture
device 22 for shuttering and flashing.
In one methdo of use, the club speed may be determined during a
calibration swing and that same determined value used for subsequent
swings. Alternatively, a new club speed may be determined for each
swing. In a third alternative method, an average or default club speed
may be used for all test swings, in which case only one of the sensors
39a or 39b is used simply for triggering. The head angle and take away and downswing paths that are advantageously determined in the way
described above in accord with the system of Fig. 1 a are not so
determined in this alternative embodiment.
The alternative system illustrated at Fig. 1 d may be advantageously
used for golf swing evaluations at any arbitrary hitting position, such as at
a typical driving range hitting mat or a grassy or sandy area. Thus, a golf
ball 14 sitting on a real grassy or sandy lie, or on a tee 1 6, may be
impacted by a golf club and the resulting ball flight evaluated using the
system shown at Fig. 1 d. In addition, the system of Fig. 1 d is more
portable for moving around a practice area or golf course.
Fig. 2 shows a display view illustrating a golf club take away path
40, a downswing path 42 and a club head angle 44 determined based on
data obtained from the first and second rows 8, 10 of sensors 12 of a preferred impact zone analyzer 2 overlayed in the display, in accord with
using the system shown at Fig. 1 a in accord with the present invention.
The take away path 40 and downswing path 42 are preferably the paths
of the center of gravity of the club head as it goes back during the take
away portion, and comes through during the downswing portion,
respectively, of a test swing. The paths 40, 42 could also be the paths
40, 42 of another point on the club head other than the center of gravity
such as a point nearer the heel or toe of the club head. The paths 40, 42
are determined based on which ones and in what order and/or for what
duration the individual sensors 1 2 of the first and second rows 8 and 1 0 were blocked during the take away and downswing portions of the test
swing.
The head angle 44 illustrated in the display is that of the club head
at the second row 10 nearest the impact point with the ball 14. The
distance between the second row 10 and the ball 14 may be closer than
is represented by any of Figs. 1 a-1 c or 2, such that the head angle 44 at
the second row 1 0 very nearly represents the ultimately important head
angle 44 at impact. On that point, none of the distances in the figures of
this application are necessarily drawn to scale.
The software may estimate the head angle at impact from the head
angle at the second row and/or at the first row, and may use another
estimate for the rate of closing of the head from the second row to the
impact point to make the estimation. For example, although the head
appears to be slightly open at the second row 10 in Fig. 2, the head 44 is
likely somewhat less open at impact, depending on the skill level of the
golfer performing the test swing. In practice, the second row 10 of
sensors 1 2 is so close to the impact position that the head angle at the
second row 10 of sensors 1 2 is at least almost exactly the head angle at
impact.
Fig. 3a shows a display view of three temporally successive images
46, 48 and 50 of a golf ball 14 during flight after impact with a golf club
head, wherein each golf ball image 46, 48 and 50 shows an image on the
golf ball 1 4 of a marking 52a, 52b and 52c, respectively, in accord with
the present invention. Although three images 46, 48 and 50 are shown, two or more than three images may be captured and used for determining
initial flight conditions of the ball 14. The computer 6 determines
kinematic properties of the ball in flight based on these images by
photogrammetry. The image capture timing is determined based on the
club head speed determined by the analyzer 2, preferably from a
calibration swing.
The actual marking on the ball 1 4 is preferably, but not necessarily,
circumferentially drawn around the entire ball 14 such as to separate the
ball 14 into two hemispheres like a meridian and to form a closed loop.
The marking is more specifically preferably at least halfway
circumambulatory of the ball 14, but need not be closed around the entire ball 14. The marking is preferably long enough that it may be within the
camera view no matter what the rotational position of the ball is when its
image is cpatured.
More than one marking may be provided. The two or more
markings may be off center such that for each marking the two areas
separated by the marking are not equal. The degree of equality or
inequality of the two areas is however known in each case and
programmed into the software running on the computer 6 of the ball flight
monitor system of the present invention.
The three images of Fig. 3a are exemplary of those captured by the
camera 24 of the ball capture device 22 discussed above, each due to the
flashing of one of the lamps 26, 28 and 30. By comparing and
contrasting two of or preferably all three of the images 46, 48 and 50 using the software running on the computer 6 and the known timing
between the capturing of the images, initial ball flight characteristics such
as horizontal and vertical velocity, including speed and direction, and total
spin, including backspin and sidespin, can be determined. Analysis and
computation by the processor running the particular software routines
programmed into it in accord with the present invention can then reveal
the total ball flight characteristics such as total distance and flight
trajectory.
Fig. 3b shows a display view of the multiple temporally successive
images 46, 48 and 50 of the golf ball 1 6 including the marking images
52a, 52b and 52c as shown and described with respect to Fig. 3a. In
addition, Fig. 3b shows software generated linear extrapolations 54a, 54b
and 54c of the marking images 52a, 52b and 52c, respectively. Also,
Fig. 3b shows circumferential extrapolations 56a, 56b and 56c based on
the two-dimensional captured perimeters of the images 46, 48 and 50,
respectively, in accord with the present invention. A calibration routine is
preferably used that allows the computer to recognize the general shape
and size within predetermined ranges of the images 46, 48, 50 of the
ball 1 4 after the images 46, 48, 50 are captured.
The linear extrapolations 54a, 54b and 54c of the marking images
52a, 52b and 52c are performed by the computer 6 from the curved
marking images 52a, 52b and 52c illustrated at Figs. 3a-3b. This
curvature is caused at least in part by sidespin on the ball 14 and/or the
location of the ball 1 6 at the times each image was captured relative to the camera exposure aperture in the vertical plane of the field of view shown at Fig. 3b, and the fact that the surface of the actual ball 14 is
curved. The software takes into account each of these factors in making
the linear extrapolations 54a, 54b and 54c.
Once the linear extrapolations 54a-54c are calculated, then the
initial backspin on the ball is calculated by first comparing and contrasting
the linear extrapolations 54a-54c. Qualitatively speaking, the initial
backspin may be determined in accord with the present invention based
on angular differences between the linear extrapolations 54a-54c and
known time differences between the capturing of the images 46, 48 and 50.
The circumferential extrapolations 56a-56c allow the computer to
determine the diameter of each image 46, 48, 50. Although the actual
diameter of the ball 14 does not change, at least after the ball resumes its
spherical shape after being deformed at impact, each image diameter
depends on how near to the camera that the ball is when each image 46,
48, 50 is captured. For example, a larger image diameter means the ball
14 was closer to the camera when the image 46, 48 or 50 was captured.
By analyzing one or more, preferably at least two or all three, of these
image diameters, the computer 6 can advantageously calculate the
horizontal direction that the ball 14 is initially heading in.
The curvatures of the actual markings 52a-52c is also used
advantageously to determine the sidespin on the ball 14. The rotated
positions of the markings 52a-52c as well as the curvatures at those positions allows the computer 6 to precisely determine the sidespin.
Advantageously, based on the sidespin so determined, the trajectory of
the ball flight, especially as the ball curves from left to right, may be
determined with precision. Thus, the combination of the determinations
made by the computer 6 based on the images 46, 48, 50, including the
extrapolations 54a-54c and 56a-56c, and the position and curvature
determination of the marking images, allows the computer to factor the
initial backspin and sidespin and initial vertical and horizontal velocities of
the ball 14 into the calculation of the total ball flight characteristics.
Another feature may be added to the any of the above
embodiments. That is, an additional image may be captured by the
system. The additional image is captured at the impact timing of the club head with the ball. The additional image would include an image of the
ball as well as the club head, and particularly the relationship between the
position of the ball with the club head at the impact time.
The additional image may be one captured with the use of an
additional flashlamp, or one of the flashlamps described above for use
with one of the images captured during the ball flight may be used to
capture the impact image. In the latter case, one fewer images will be
captured of the ball 14 during flight. For the embodiments described
above using three images, the images of the ball 14 in flight would then
be two, and one skilled in the art would realize that two is enough to
determine initial ball flight conditions. The ball flight capture device 22 may be modified to capture this
additional image at the time of impact. The modification may be simply
to move the camera 24 so that the impact position is within the viewing
range of the camera 24. The viewing range may also be widened to
include the impact position. The impact timing is estimated preferably
using a club head speed calculated in a calibration swing or also may be
calculated during the swing at issue or using a default club head speed.
After the club head passes one or both of the rows 8, 10 or one or both
of the sensors 39a, 39b, the time until impact being known based on the
club head speed and distance remaining until impact, the first flash is
produced by one of the flashlamps 26, 28 or 30, preferably flashlamp 26,
at the time of the impact and the image captured.
Advantageously, the position of the club head with respect to the
ball and/or the surface of the ground at impact are captured for analysis.
It may be observed from the captured image at impact whether the club
head is "toe up", "toe down" or even at impact. It may also be observed
whether the ball is struck at the center or nearer the toe or heel of the
club head at impact. In addition, it may be observed how open or closed
the face of the club is at impact, and it may also be observed what the
loft of the club is at impact. It may also be observed whether the ball
was impacted "thin" or "fat" from the captured image of the impact.
Fig. 4a shows an overhead view representing total golf ball flight
characteristics calculated based on the images and extrapolations shown
and described above, particularly with respect to Fig. 3b. Three horizontal flight trajectories are shown in Fig. 4a that were calculated
from three different test swings. The hoπzontal axis is the "distance" in
yards and the vertical axis is the left to right distance.
As can be observed, the ball started out moving in a direction right
of straightaway along flight path A, but then "drew", or moved right to
left due to counterclockwise spin (using the perspective of Fig. 4a)
imparted to the ball at impact. The swing that was calculated by the
computer 6 based on initial flight conditions to produce flight path A, and
determined in accord with the present invention, caused the ball to land
about 250 yards out and only about 5 yards right of straight away. The
ball traveling along flight path B started out a little less right of straight
away than that for flight path A, had a similar draw, and landed about 5
yards to the left of the flight path A ball. The ball traveling along flight
path C started even less right of straight away than that for flight path B,
and a little more draw such that the ball was calculated to land about 1 5
yards left of straight away, again about 250 yards down the fairway.
Fig. 4b shows a side view representing total golf ball flight
characteristics calculated based on the images and extrapolations
described above, particularly with respect to Fig. 3b. The horizontal axis
again shows the distance down the fairway that the ball was calculated
to travel in the air. This time, the vertical axis shows the height of the
golf ball as it traveled along its flight path. Again, three paths D-F are
shown in Fig. 4b. The golf swing that was calculated by the computer 6 to cause the
ball to travel along flight path D was shown to rise to about 140 feet
before beginning its downward ascent to land about 250 yards down the
fairway. The flight paths E and F has a maximum calculated altitude for
the respective balls to be 100 and 70 yards, respectively, while each ball
was calculated to land around 250 yards down the fairway.
It is emphasized that the flight paths shown and described with
respect to Figs. 4a and 4b are only examples to show the kinds of
calculations and displays that the present invention can do. Again, the
total initial spin including backspin and side spin and the total initial
velocity including components is three dimensions are advantageously
determined and used to calculate the flight paths of Figs. 4a and 4b. The
aerodynamic lift caused by spin and aerodynamic drag may be used as
inputs to figure the total flight characteristics of the ball. Other factors
may be inputs for the computer to use in the calculations such as wind,
air density or altitude, various club and ball parameters such as club
speed and loft, ball cover hardness or durometer reading, ball core spin
density, relative impact positions of the club head with the ball, weather
conditions such as rain, etc. As noted, the relative impact positions and
club speed can be determined in accord with the present invention.
Another parameter that may be advantageously calculated in
accord with the present invention is the energy transfer efficiency of the
impact of the club head with the ball. That is, the club head speed and
initial velocity and spin of the ball may be determined in accord with the present invention. Thus, the efficiency can be calculated by subtracting
the energy that a ball would have if a perfectly elastic collision occurred
between the club head and ball, and the actual energy that the ball is
observed to have in the form of translational and rotational kinetic energy
minus work done against gravity to reach the image position or positions
used in the calculation. This efficiency determination can be
advantageously used in consideration of the quality of the equipment, i.e.,
the ball and club, that are used during the test swing.