U.S. patent application number 10/743283 was filed with the patent office on 2004-07-22 for ball trajectory measuring apparatus.
Invention is credited to Asakura, Takeshi.
Application Number | 20040142772 10/743283 |
Document ID | / |
Family ID | 32709223 |
Filed Date | 2004-07-22 |
United States Patent
Application |
20040142772 |
Kind Code |
A1 |
Asakura, Takeshi |
July 22, 2004 |
Ball trajectory measuring apparatus
Abstract
A first camera (1) is provided behind a launch point (Ps), a
second camera (2) is provided between the launch point (Ps) and a
drop point (Pe), and a third camera (3) is provided before the drop
point (Pe). The first camera (1) and the second camera (2)
photograph a golf ball (G) from a back part. The third camera (3)
photographs the golf ball (G) from a front part. First of all, the
golf ball (G) is photographed by the first camera (1) and the third
camera (3). The photographing of the first camera (1) is relayed to
the second camera (2). Then, the golf ball (G) is photographed by
the second camera (2) and the third camera (3). The angle of view
of the first camera (1) is related to that of the second camera
(2). Based on image data which are obtained by cameras, a
coordinate position (x, z) of the golf ball (G) is calculated by a
triangulation method.
Inventors: |
Asakura, Takeshi; (Kobe-shi,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
32709223 |
Appl. No.: |
10/743283 |
Filed: |
December 23, 2003 |
Current U.S.
Class: |
473/407 |
Current CPC
Class: |
A63B 2220/807 20130101;
A63B 24/0021 20130101; G06T 2207/30224 20130101; A63B 2220/05
20130101; G06T 2207/30241 20130101; G06T 7/292 20170101; A63B
71/0605 20130101; A63B 69/3658 20130101; A63B 2024/0034
20130101 |
Class at
Publication: |
473/407 |
International
Class: |
A63B 057/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 21, 2003 |
JP |
2003-11743 |
Claims
What is claimed is:
1. A ball trajectory measuring apparatus comprising: a first camera
for photographing a flying ball from a back part; a second camera
having an angle of view related to that of the first camera and
serving to photograph the ball from the back part later than the
first camera; a third camera for photographing the ball from a
front part; a control portion for controlling photographing timings
of the first, second and third cameras; and a calculating portion
for calculating position coordinates of the ball based on image
data obtained by the first, second and third cameras, and position
coordinates, directions of optical axes and angles of view of the
respective cameras.
2. The ball trajectory measuring apparatus according to claim 1,
wherein the first camera is positioned behind a ball launch point,
the second camera is positioned between the launch point and a drop
point, and the third camera is positioned before the drop
point.
3. The ball trajectory measuring apparatus according to claim 1,
wherein the angle of view of the first camera partially overlaps
with that of the second camera, and the angle of view of the second
camera is related to that of the first camera based on ball images
which are simultaneously photographed by the first camera and the
second camera.
4. A ball trajectory measuring apparatus comprising: a first camera
for photographing a flying ball from a front part; a second camera
having an angle of view related to that of the first camera and
serving to photograph the ball from the front part earlier than the
first camera; a third camera for photographing the ball from a back
part; a control portion for controlling photographing timings of
the first, second and third cameras; and a calculating portion for
calculating position coordinates of the ball based on image data
obtained by the first, second and third cameras, and position
coordinates, directions of optical axes and angles of view of the
respective cameras.
5. The ball trajectory measuring apparatus according to claim 4,
wherein the first camera is positioned before a ball drop point,
the second camera is positioned between a launch point and the drop
point, and the third camera is positioned behind the launch
point.
6. The ball trajectory measuring apparatus according to claim 4,
wherein the angle of view of the first camera partially overlaps
with that of the second camera, and the angle of view of the second
camera is related to that of the first camera based on ball images
which are simultaneously photographed by the first camera and the
second camera.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an apparatus for measuring
the trajectory of a flying ball.
[0003] 2. Description of the Related Art
[0004] A golf ball flies by hitting through a golf club. If the
trajectory of the flying golf ball can be measured, the evaluation
of the performance of the golf ball, the evaluation of the
performance of the golf club and the diagnosis of the swing form of
a golf player are carried out.
[0005] Japanese Laid-Open Patent Publication No. 6-323852 has
disclosed a measuring apparatus using a CCD camera having a shutter
function. In this apparatus, image data photographed by the CCD
camera are fetched into a calculating portion and a change between
image frames is written to a multilayer memory by an image
processing. The trajectory of a golf ball is measured from a
multilayered image thus obtained. In the measuring apparatus, the
trajectory of the golf ball can be observed but time series data on
the position coordinates of the golf ball cannot be measured.
[0006] Japanese Laid-Open Patent Publication No. 2001-145718 has
disclosed an apparatus for measuring the trajectory of a golf ball
based on image data obtained by a CCD camera provided behind a
launch point and image data obtained by a CCD camera provided on
the side of the trajectory). In this apparatus, a large number of
CCD cameras are required to be provided on the side. In order to
measure the trajectory with high precision by this apparatus,
furthermore, a distance between the CCD camera provided on the side
and the golf ball is to be sufficiently increased. In general golf
courses and examination sites of golf equipment manufacturers, a
distance in a hitting direction is long and a side space is small.
The installation of the apparatus has many restrictions.
[0007] Furthermore, there has also been proposed an apparatus for
photographing a golf ball from both sides by means of two CCD
cameras provided on the right and left sides of a trajectory. In
this apparatus, the trajectory of the golf ball is measured based
on a pair of image data by a triangulation method. In order to
measure the trajectory with high precision by this apparatus, it is
necessary to set a distance between the left and right CCD cameras
to be sufficiently great. In order to install the apparatus, it is
necessary to take a very large side space. The installation of the
apparatus has many restrictions.
[0008] There can also be proposed means for measuring a trajectory
by an apparatus comprising a CCD camera provided behind a launch
point and a CCD camera provided before a drop point. In the
measurement using this apparatus, a very large side space is not
required. In order to photograph the trajectory within a wide range
by this apparatus, a wide angle CCD camera is required. In the wide
angle CCD camera, precision in the measurement is insufficient. In
the case in which the position coordinates of a golf ball are
calculated immediately after a launch and immediately before a drop
(in other words, a golf ball in a low position), the precision is
particularly insufficient.
[0009] It is an object of the present invention to provide a ball
trajectory measuring apparatus which can easily be installed and
can measure time series data on the position coordinates of a
flying ball with high precision.
SUMMARY OF THE INVENTION
[0010] The present invention provides a ball trajectory measuring
apparatus comprising a first camera for photographing a flying ball
from a back part, a second camera having an angle of view related
to that of the first camera and serving to photograph the ball from
the back part later than the first camera, a third camera for
photographing the ball from a front part, a control portion for
controlling photographing timings of the first, second and third
cameras, and a calculating portion for calculating position
coordinates of the ball based on image data obtained by the first,
second and third cameras, and position coordinates, directions of
optical axes and angles of view of the respective cameras.
[0011] In the measuring apparatus, the camera is not provided on a
side. Accordingly, a very large side space is not required. In the
measuring apparatus, the photographing is carried out from the back
part by means of the first camera and the second camera and is
carried out from the front part by means of the third camera. The
position coordinates of the ball are calculated by a triangulation
method based on image data obtained by the photographing from the
back part and image data obtained by the photographing from the
front part. The photographing to be carried out from the back part
is relayed from the first camera to the second camera. The angle of
view of the second camera is related to that of the first camera.
Therefore, the ball can be photographed within a wide range of the
trajectory through the relay.
[0012] It is preferable that the first camera should be positioned
behind a ball launch point, the second camera should be positioned
between the launch point and a drop point, and the third camera
should be positioned before the drop point. Since the second camera
is positioned between the launch point and the drop point, an angle
formed by an optical axis in a horizontal direction can be set to
be great. The angle of elevation of the golf ball measured
immediately before the drop by means of the second camera is great.
The measuring apparatus has high precision in the measurement of
the ball immediately before the drop.
[0013] It is preferable that the angle of view of the first camera
should partially overlap with that of the second camera. The angle
of view of the second camera is related to that of the first camera
based on ball images which are simultaneously photographed by the
first camera and the second camera. This apparatus is excellent in
precision in the measurement.
[0014] Another invention provides a ball trajectory measuring
apparatus comprising a first camera for photographing a flying ball
from a front part, a second camera having an angle of view related
to that of the first camera and serving to photograph the ball from
the front part earlier than the first camera, a third camera for
photographing the ball from a back part, a control portion for
controlling photographing timings of the first, second and third
cameras, and a calculating portion for calculating position
coordinates of the ball based on image data obtained by the first,
second and third cameras, and position coordinates, directions of
optical axes and angles of view of the respective cameras.
[0015] In the measuring apparatus, the camera is not provided on a
side. Accordingly, a very large side space is not required. In the
measuring apparatus, the photographing is carried out from the back
part by means of the third camera and is carried out from the front
part by means of the first camera and the second camera. The
position coordinates of the ball are calculated by a triangulation
method based on image data obtained by the photographing from the
back part and image data obtained by the photographing from the
front part. The photographing to be carried out from the front part
is relayed from the second camera to the first camera. The angle of
view of the second camera is related to that of the first camera.
Therefore, the ball can be photographed within a wide range of the
trajectory through the relay.
[0016] It is preferable that the first camera should be positioned
before a ball drop point, the second camera should be positioned
between a launch point and the drop point, and the third camera
should be positioned behind the launch point. Since the second
camera is positioned between the launch point and the drop point,
an angle formed by an optical axis thereof in a horizontal
direction can be set to be great. The angle of elevation of the
golf ball measured immediately after the launch by means of the
second camera is great. The measuring apparatus has high precision
in the measurement of the ball immediately after the launch.
[0017] It is preferable that the angle of view of the first camera
should partially overlap with that of the second camera. The angle
of view of the second camera is related to that of the first camera
based on ball images which are simultaneously photographed by the
first camera and the second camera. This apparatus is excellent in
precision in the measurement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a view showing the schematic structure of a ball
trajectory measuring apparatus according to an embodiment of the
present invention,
[0019] FIG. 2 is a side view showing a state in which the
trajectory of a golf ball is measured by the apparatus in FIG.
1,
[0020] FIG. 3 is a side view showing another measuring method using
the apparatus in FIG. 1, and
[0021] FIG. 4 is a side view showing a state in which the
trajectory of the golf ball is measured by a ball trajectory
measuring apparatus according to another embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] A preferred embodiment of the present invention will be
described below in detail with reference to the drawings.
[0023] An apparatus shown in FIG. 1 comprises a first camera 1, a
second camera 2, a third camera 3, a control portion 4 and a
calculating portion 5. The first camera 1, the second camera 2 and
the third camera 3 are CCD cameras having a shutter function. The
control portion 4 and the calculating portion 5 include a computer
and a peripheral apparatus. The control portion 4 and the
calculating portion 5 may be constituted by the same computer. A
ball trajectory measuring apparatus may comprise a printing
portion, a display portion and the like which are not shown.
[0024] The control portion 4 detects a trigger signal generated by
hitting a golf ball and then transmits a signal to the calculating
portion 5 in order to start to record image data. Moreover, the
control portion 4 transmits a synchronizing signal toward the first
camera 1, the second camera 2 and the third camera 3. A plurality
of synchronized images is obtained by the first camera 1, the
second camera 2 and the third camera 3 which receive the
synchronizing signal.
[0025] The calculating portion 5 records, for each frame, image
data obtained by the first camera 1, the second camera 2 and the
third camera 3. For the recording, a time plus VTR, a digital disk
recorder, an animation board or the like can be used. The data thus
obtained are used for an image processing. In the image processing,
a difference peak hold calculation is carried out in order of
frames for the image data. More specifically, only a pixel memory
for a changed peak in the pixel of each frame memory is held and
other memories are erased. The image of a golf ball is whiter than
a background and is obtained as the whitest portion in a decision
of shading. Consequently, the background is erased by the image
processing so that it is possible to obtain data in which only the
image of the golf ball remains.
[0026] FIG. 2 is a typical side view showing a state in which the
trajectory of the golf ball is measured by the apparatus in FIG. 1.
FIG. 2 shows a golf ball G and a trajectory T of the golf ball G.
The golf ball G flies from left to right in FIG. 2. In FIG. 2, Ps
denotes a launch point and Pe denotes a drop point. As shown in
FIG. 2, there can be supposed two-dimensional position coordinates
in which the position of the first camera 1 is set to be an origin,
a straight line connecting the first camera 1 and the second camera
2 is set to be an X axis and a direction of a height is set to be a
Z axis.
[0027] The first camera 1 and the second camera 2 are provided
behind the launch point Ps. The first camera 1 and the second
camera 2 are placed in substantially the same position. The first
camera 1 and the second camera 2 photograph the golf ball G from a
back part. The third camera 3 is provided before the drop point Pe.
The third camera 3 photographs the golf ball G from a front part. A
distance between the first camera 1 and second camera 2 and the
third camera 3 is represented as L. The position coordinates of the
first camera 1 and the second camera 2 are (0, 0) and the position
coordinates of the third camera 3 are (L, 0). The first camera 1,
the second camera 2 and the third camera 3 are provided in such a
manner that optical axes thereof are inclined upward in a
horizontal direction. The inclination angle of the first camera 1
is greater than that of the second camera 2. The angle of view of
the first camera 1 is surrounded by two-dotted chain lines L1a and
L1b shown in FIG. 2. The angle of view of the second camera 2 is
surrounded by two-dotted chain lines L2a and L2b. The angle of view
of the first camera 1 partially overlaps with that of the second
camera 2.
[0028] Description will be given to a method of calculating
position coordinates (x, z) of the golf ball G by a triangulation
method. When the golf ball G is launched, first of all, the golf
ball G is photographed by the first camera 1 and the third camera
3. In this stage, the image of the golf ball G is not taken by the
second camera 2. By the photographing, continuous image data are
obtained. The image data obtained by the first camera 1 and the
image data obtained by the third camera 3 make a pair. A
black-and-white decision is carried out by horizontal scanning over
frame data obtained by the first camera 1, and ball position in a
vertical direction on the image are detected. Based on the result
of the detection and a direction of an optical axis and an angle of
view in the first camera 1, an angle of elevation .theta..sub.1 of
the golf ball G in the position of the first camera 1 is
calculated. Similarly, the black-and-white decision is carried out
by the horizontal scanning over the frame data obtained by the
third camera 3, and ball position in a vertical direction on the
image are detected. Based on the result of the detection and a
direction of an optical axis and an angle of view in the third
camera 3, an angle of elevation .theta..sub.3 of the golf ball G in
the position of the third camera 3 is calculated.
[0029] The following equation (1) is obtained by a triangle formed
by a foot Pf of a perpendicular drawn from the golf ball G, and the
first camera 1 and the golf ball G to be apexes.
tan .theta..sub.1=z/x (1)
[0030] On the other hand, the following equation (2) is obtained by
a triangle formed by the foot Pf of the perpendicular drawn from
the golf ball G, and the third camera 3 and the golf ball G to be
apexes.
tan .theta..sub.3=z/(L-x) (2)
[0031] The following equations (3) and (4) are obtained from the
equations (1) and (2).
x=(L.multidot.tan .theta..sub.3)/(tan .theta..sub.1+tan
.theta..sub.3) (3)
z=(L.multidot.tan .theta..sub.1.multidot.tan .theta..sub.3)/(tan
.theta..sub.1+tan .theta..sub.3) (4)
[0032] The distance L between the first camera 1 and the third
camera 3 and the angles of elevation .theta..sub.1 and
.theta..sub.3 which are calculated are substituted for the
equations (3) and (4), and the position coordinates (x, z) of the
golf ball G are calculated. The position coordinates (x, z) are
obtained as time series data with the flight of the golf ball
G.
[0033] As described above, the angle of view of the first camera 1
partially overlaps with that of the second camera 2. For a certain
period of the flight, therefore, the image of the golf ball is
photographed by both the first camera 1 and the second camera 2.
The first camera 1 and the second camera 2 are synchronized with
each other. Therefore, the angle of view of the first camera 1 and
that of the second camera 2 are related to each other based on data
on images photographed at the same time. In other words, the
correspondence of the coordinates in the angle of view of the first
camera 1 to those in the angle of view of the second camera 2 is
grasped by calculating means.
[0034] When the golf ball G further flies, it gets out of the angle
of view of the first camera 1. Then, the golf ball G is
photographed by the second camera 2 and the third camera 3. Based
on the image data obtained by the second camera 2 and the third
camera 3, the position coordinates (x, z) of the golf ball G are
calculated by the triangulation method. Since the angle of view of
the first camera 1 is related to that of the second camera 2,
continuous position coordinate data can be measured with high
precision within a wide range of the trajectory T. As described
above, the angles of view are related to each other based on the
data on images photographed at the same time. Even if precision in
the installation of the optical axis of the camera is insufficient,
therefore, the position coordinates (x, z) are calculated with high
precision.
[0035] In the method shown in FIG. 2, in the case in which the golf
ball G flies without a substantial transverse shift from a target
direction, measurement is carried out. If the flight is shifted
from the target direction, a transverse direction (a perpendicular
direction to the paper in FIG. 2) is set to be a Y axis. An angle
of elevation of the golf ball G in the position of the first camera
1 is represented as .theta..sub.11, an angle of elevation of the
golf ball G in the position of the third camera 3 is represented as
.theta..sub.31, an angle in a transverse direction of the golf ball
G in the position of the first camera 1 is represented as
.theta..sub.12, and an angle in a transverse direction of the golf
ball G in the position of the third camera 3 is represented as
.theta..sub.32. .theta..sub.11, .theta..sub.31, .theta..sub.12 and
.theta..sub.32 are obtained by an image processing based on the
image data. Position coordinates (x, y, z) of the golf ball G are
obtained by substituting .theta..sub.11, .theta..sub.31,
.theta..sub.12 and .theta..sub.32 for the following equations (5),
(6) and (7).
y=(L.multidot.tan .theta..sub.12.multidot.tan .theta..sub.32)/(tan
.theta..sub.12+tan .theta..sub.32) (5)
0=((tan .theta..sub.11).sup.2+(tan
.theta..sub.31).sup.2).multidot.x.sup.2- +2.multidot.(tan
.theta..sub.31).sup.2.multidot.L.multidot.x+((tan
.theta..sub.11).sup.2+(tan
.theta..sub.31).sup.2).multidot.y.sup.2-(tan
.theta..sub.31).sup.2.multidot.L.sup.2 (6)
0=(tan .theta..sub.11).sup.2.multidot.(x.sup.2+y.sup.2)-z.sup.2
(7)
[0036] Also in this case, the photographing is relayed by the first
camera 1 and the second camera 2 which have mutual angles of view
related to each other. Consequently, the measurement can be carried
out within a wide range of the trajectory T.
[0037] At least three cameras for photographing the golf ball G
from a back part may be provided to relay the photographing. At
least two cameras for photographing the golf ball G from a front
part may be provided to relay the photographing.
[0038] FIG. 3 is a typical side view showing another measuring
method using the apparatus of FIG. 1. In this example, the first
camera 1 is provided behind the launch point Ps, the second camera
2 is provided between the launch point Ps and the drop point Pe,
and the third camera 3 is provided before the drop point Pe. The
first camera 1 and the second camera 2 photograph the golf ball G
from a back part. The third camera 3 photographs the golf ball G
from a front part. The angle of view of the first camera 1 is
surrounded by two-dotted chain lines L1a and L1b. The angle of view
of the second camera 2 is surrounded by two-dotted chain lines L2a
and L2b. The angle of view of the first camera 1 partially overlaps
with that of the second camera 2. The angle of view of the first
camera 1 is related to that of the second camera 2.
[0039] Also in the measuring method, first of all, the golf ball G
is photographed by the first camera 1 and the third camera 3. The
photographing of the first camera 1 is relayed to the second camera
2. Then, the golf ball G is photographed by the second camera 2 and
the third camera 3. Based on image data thus obtained, the
coordinate position (x, z) or (x, y, z) of the golf ball G is
calculated by the triangulation method.
[0040] In an example shown in FIG. 3, the golf ball G is
photographed immediately before a drop by the second camera 2. The
Z coordinate of the golf ball G which is obtained immediately
before the drop is small. If the second camera 2 is placed in the
same position as the first camera 1, the angle of elevation of the
golf ball G obtained immediately before the drop by the second
camera 2 is small. On the other hand, if the second camera 2 is
positioned between the launch point Ps and the drop point Pe as
shown in FIG. 3, the angle of elevation of the golf ball G obtained
immediately before the drop by the second camera 2 is comparatively
great. The great angle of elevation contributes to an enhancement
in precision in the measurement. The reason will be described
below.
[0041] It is assumed that the position coordinates of the golf ball
G obtained immediately before the drop are (200, 3), the position
coordinates of the second camera 2 are (0, 0) and the position
coordinates of the third camera 3 are (300, 0). In other words, it
is assumed that the second camera 2 is provided behind the launch
point Ps. In this case, an angle of elevation .theta..sub.2 of the
golf ball G from the second camera 2 is calculated as 0.86 degree
by the following equation.
.theta..sub.2=tan.sup.-1 (3/200)
[0042] On the other hand, an angle of elevation .theta..sub.3 of
the golf ball G from the third camera 3 is calculated as 1.72
degrees from the following equation.
.theta..sub.3=tan.sup.-1 (3/(300-200))
[0043] If the angle of elevation .theta..sub.2 obtained based on
the image data of the second camera 2 is 0.91 degree (that is, a
value obtained with a shift of 0.05 degree from the original value
of 0.86 degree), the position coordinates (x, y) of the golf ball G
are calculated as (196.2, 3.1) by the following equation.
x=(300.multidot.tan(1.72))/(tan(0.91)+tan(1.72))
z=(300.multidot.tan(0.91).multidot.tan(1.72))/(tan(0.91)+tan(1.72))
[0044] "196.2" to be the x coordinate thus calculated is smaller
than "200" to be an actual x coordinate by 3.8.
[0045] In the case in which the position coordinates of the second
camera 2 are (150, 0), in other words, the second camera 2 is close
to the drop point Pe, the angle of elevation .theta..sub.2 is
calculated as 3.43 degrees by the following equation.
.theta..sub.2=tan.sup.-1(3/(200-150))
[0046] If the angle of elevation .theta..sub.2 obtained based on
the image data of the second camera 2 is 3.48 degrees (that is, a
value obtained with a shift of 0.05 degree from the original value
of 3.43 degrees), the position coordinates (x, z) of the golf ball
G are calculated as (199.6, 3.0) by the following equation.
x=(150.multidot.tan(1.72))/(tan(3.48)+tan(1.72))
z=(150.multidot.tan(3.48).multidot.tan(1.72))/(tan(3.48)+tan(1.72))
[0047] "199.6" to be the x coordinate thus calculated is very close
to "200" to be an actual x coordinate. Thus, the second camera 2 is
provided in such a position that the golf ball G can be
photographed immediately before the drop at a great angle of
elevation. Consequently, the precision in the measurement can be
enhanced.
[0048] In respect of the precision in the measurement, it is
preferable that the second camera 2 should be provided in such a
position that the inclination angle of the optical axis thereof is
3 to 40 degrees. The inclination angle is more preferably 5 to 40
degrees and particularly preferably 7 to 40 degrees. From the
viewpoint of the precision in the measurement, it is preferable
that the second camera 2 should be provided close to the third
camera 3 from the middle point of the first camera 1 and the third
camera 3.
[0049] It is preferable that the distances of the first camera 1,
the second camera 2 and the third camera 3 from the ground should
be 3 m or less. If the distance from the ground is more than 3 m,
it is hard to measure the golf ball G immediately after the launch
and immediately before the drop. From this viewpoint, it is more
preferable that the distance from the ground should be 2 m or less.
An ideal distance from the ground is zero.
[0050] At least three cameras for photographing the golf ball G
from a back part may be provided to relay the photographing. At
least two cameras for photographing the golf ball G from a front
part may be provided to relay the photographing.
[0051] FIG. 4 is a typical side view showing a state in which the
trajectory of a golf ball is measured by a ball trajectory
measuring apparatus according to another embodiment of the present
invention. This apparatus comprises a first camera 4, a second
camera 5 and a third camera 6 which are the same as those of the
apparatus in FIG. 1. This apparatus comprises the same components
as the control portion 4 and the calculating portion 5 of the
apparatus in FIG. 1, which are not shown.
[0052] The first camera 4 is provided before a drop point Pe, the
second camera 5 is provided between a launch point Ps and the drop
point Pe, and the third camera 6 is provided behind the launch
point Ps. The first camera 4 and the second camera 5 photograph a
golf ball G from the front part. The third camera 6 photographs the
golf ball G from the back part. The angle of view of the first
camera 4 is surrounded by two-dotted chain lines L1a and L1b. The
angle of view of the second camera 5 is surrounded by two-dotted
chain lines L2a and L2b. The angle of view of the first camera 4
partially overlaps with that of the second camera 5. The angle of
view of the first camera 4 is related to that of the second camera
5.
[0053] In the measuring method, first of all, the golf ball G is
photographed by the second camera 5 and the third camera 6. The
photographing of the second camera 5 is relayed to the first camera
4. Then, the golf ball G is photographed by the first camera 4 and
the third camera 6. Based on image data thus obtained, the
coordinate position (x, z) or (x, y, z) of the golf ball G is
calculated by the triangulation method.
[0054] In an example shown in FIG. 4, the golf ball G is
photographed immediately after a launch by the second camera 5. The
Z coordinate of the golf ball G which is obtained immediately after
the launch is small. If the second camera 5 is placed in the same
position as the first camera 4, the angle of elevation of the golf
ball G obtained immediately after the launch by the second camera 5
is small. On the other hand, if the second camera 5 is positioned
between the launch point Ps and the drop point Pe as shown in FIG.
4, the angle of elevation of the golf ball G obtained immediately
after the launch by the second camera 5 is comparatively great. The
great angle of elevation contributes to an enhancement in precision
in the measurement.
[0055] In respect of the precision in the measurement, it is
preferable that the second camera 5 should be provided in such a
position that the inclination angle of the optical axis thereof in
a horizontal direction is 3 to 40 degrees. The inclination angle is
more preferably 5 to 40 degrees and particularly preferably 7 to 40
degrees. From the viewpoint of the precision in the measurement, it
is preferable that the second camera 5 should be provided close to
the third camera 6 from the middle point of the first camera 4 and
the third camera 6.
[0056] At least two cameras for photographing the golf ball G from
a back part may be provided to relay the photographing. At least
three cameras for photographing the golf ball G from a front part
may be provided to relay the photographing.
[0057] While the apparatus according to the present invention has
been described above by taking, as an example, the case in which
the trajectory of the golf ball G is measured, it is also suitable
for measuring the trajectory of another ball.
[0058] The above description is only illustrative and can be
variously changed without departing from the scope of the present
invention.
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