Note: Descriptions are shown in the official language in which they were submitted.
CA 02484674 2004-10-14
TITLE: iVlethod and Apparatus far Locating the Trajectory of an Object in
Motion.
FIELD OF THE INVENTION
[0001 ] This invention relates to a detection system fox determining the
position, velocity and
trajectory in space of moving objects, such as golf balls and baseballs for
the purpose of
training and practicing as well as other objects such as the detection of
projectiles approaching
a vehicle. It can also be used to evaluate the mechanical characteristics of a
baseball bat, tennis
racket, ox the like by comparing the ball's velocity before and after the
collision with the
baseball bat or racket, etc. Moreover, it can accurately determine whether ox
not a baseball
crosses the strike zone by tracking its trajectory in front of the home plate.
BACKGROUND TO THE INVENTIt~N
[0002] Numerous systems exist for tracking a golf ball and estimating its
range. Their main
purpose is to give golfers a graphic and/or numeric display indicating their
drive's
effectiveness when they practice or play.
[00031 U.S. Patent No. 5,303,924 describes a golf game apparatus that
simulates a total golf
shot distance based upon the actual flight of a struck golf ball at a practice
range, projecting the
flight distance of the ball to an initial impact position on a target area. A
microphone in the area
detects the take off of the ball stz~uck by the club head, and an array of
microphones in the
target area detects its arrival. The time between the two events can be
correlated to the range.
The system requires a semi-permanent installation.
[0004] U.S. Patent No. 5,413,345 describes a system that identifies, tracks,
displays and
records all or selected portions of the path of one ox more golf balls. It
performs these functions
from the time each ball is struck, or a$er it is in flight, until it reaches
the final point of rest. It
uses an array of high-speed cameras installed on the green.
[0405] U.S. Patent No. 5,472,205 describes a system that detects the club head
offset angle
relative to a desired club head axis as well as the speed of club head by sag
light reflected
from the underside of the club head and processing this information
electronically. The latter
1 --
CA 02484674 2004-10-14
can be used to calculate the ball's speed by assuming an efficiency of
momentum transfer from
the club head to the ball. The system requires a semi-permanent installation.
[0006] U.S. Patent No. 5,489,099 describes a system comprising a video camera,
a video
processor and a flight path predictor. A video camera Locks onto the ball and
tracks it while
being rotated by an automatic control system.
[0007] U.S. Patent No. 5,846,139 describes a golf simulator consisting of
three arrays of
infrared receivers and emitters installed in an enclosure providing a shield
from the ambient
light. The system determines the ball's velocity vector. It requires a
permanent installation.
[0008] U.S. Patent No. 5,926,780 describes a system for measuring a ball's
velocity vector.
It consists of two arrays of Light sensors illuminated from above by two light
sources. When the
ball is struck, it flies over the two arrays and casts a shadow over a few
sensors. Their location
in the array and the position of the light sources allows the calculation of
the ball's velocity
vector. The patent does not address the exposure of the arrays to the ambient
light. The system
requires a semi-permanent installation.
[0009] U.S. Fatent No. 5,938,545 describes a system comprising two video
cameras
mounted on a golf cart. Their fields of view overlap and they track the ball
by successive frame
scans. The ball's trajectory is determined with respect to the cart, which is
at an angle with
respect to the launch pointer target line and at a certain distance from this
reference point. This
angle and this distance must both be known in order to relate the trajectory
to the target line
and to the position of the golfer. The system does not address the saturation
effect of the sun on
the area CCD sensor in the camera.
[0010] U.S. Patent No. 6,012,987 describes an electronic surveillance camera
and a motion
sensor above the green. Signals from the camera and the motion sensor are
txansmitted to a
processing unit. The latter generates the movement of an object on a video
screen. The system
requires a semi-permanent installation.
2
CA 02484674 2004-10-14
[0011] U,S. Patent No. 6,093,923 describes two or mare video cameras installed
on a drive
range tracking a golf ball within their fields of view. The system then
electronically simulates
the ball's trajectory to determine the ball's probable point of impact.
[OOI2] U.S. Patent No. 6,520,864 describes a video camera tracking a golf ball
against a
IO stationary background. A computer processes the video signal. to detect the
golf ball and to
automatically determine its trajectory.
[0013] Reference [1]: Barras, Ch., Localisation optique d'objets rapproch6s
animes dune
grande vitesse (Optical location finding of high-velocity objects at close
range), Institut franco-
allemand de recherche de Saint-Louis (Franco-German Research Institute Saint-
Louis), report
S-R 904192. Though arising in a field unrelated to the tracking of out-going
objects, this
reference [lJ describes a system for protecting a military vehicle consisting
of a pair of
photodiode arrays with lenses that form fan-shaped fields of view overlapping
in a single plane.
It can detect at close range the position of an incoming projectile aimed at a
vehicle. However,
it cannot determine the velocity, nor the direction of the threat.
(_0014] Reference [2]: European patent application by Giat Industries, FP 1
096 2I 9 A 1.
Inventors: Lefebvre, Gerald and lVluller, Sylvain; Proeede et systems pour
detecter acne
menace tires sur un objet fire ou mobile. (Method and system far detecting a
threat fared at a
stationary cir moving object). Applicant, Publication date: 2001-05-10. 'This
reference [2j
describes a similar military-focus system concerning incotxzing objects in
which two arrays
with lenses installed on either side of the front of a military vehicle define
four vertical
intersecting fields of view: It explains how measuring the time when a
projectile penetrates
each planar field of view and knowing the angle between the lines joining the
penetration
points to the sensors, on the one hand, and the horizontal plane, on the other
hand, provides
sufficient information for calculating the position of the projected
penetration points and the
velocity vector of the incoming projectile. This system covers only a military
application
related to the calculation of an incoming projectile's position and velocity
vector, wherein the
trajectory is assumed to be linear. This reference relies upon making four
successive time
measurements. This reference does not address the determination of the path of
an outgoing
object, much Iess determining a projected trajectory calculated as a parabola
corrected for
3
CA 02484674 2004-10-14
aerodynamic drag. Furthermore, this patent application does not mention how to
prevent the
over saturation of the diode array when the image of the sun is focused on it.
[4015] There is a need for a sports training system fox tracking an object in
space that does
not xequire a semi-permanent installation, but can be set up and ready for use
in a shoat time
and within a limited space. Such a system can facilitate the training of
baseball playexs, tennis
players and players of other sports based upon control of a projectile. The
device could also be
used in the evaluation of the mechanical propexties of a baseball bat, golf
club, tennis racket, ox
other device used for striking an incoming projectile.
[0016] Imaging systems can form an image of an object on a planar surface, as
in the case of
a charge-coupled device, CCD, employed in a video camera. Such planar images
require time
to sample all of the pixels available in an x, y stray. Simpler imaging
systems utilize a linear
array that provides a far smaller number of. pixel sensors. The sampling time
is accordingly
substantially reduced. However, such known linear arrays can only sample a
planar surface in
space, viewed edge-on.
[0017] Such linear arrays can be provided with directed pixel sensors, aligned
to divide the
surface of the viewing plane into a discrete number of viewing sectors. Thus
an 82.4-degree
field of view divided amongst 512 directed pixel sensors will allow each
directed sensor to
detect an object present within a detection zone having an average angular
dimension of 0.161
degrees within the detection plane.
[00183 While providing some image information with respect to the location of
an object in
space, the full location of an object, much less its firajectory, cannot be
defined through use of a
single linear array of directed pixel sensors. This invention addresses a
method by which
multiple linear arrays having directed pixel sensors rnay be utilized to
obtain more information
about the location of an object, and according to variants, defining not only
its instantaneous
location in space, but also its path of travel, local velocity and ultimate
trajectory.
[0019] The invention in its general form will first be described, and then its
implementation
in terms of specific embodiments will be detailed with reference to the
drawings following
hereafter. These embodiments axe intended to demonstrate the principle of the
invention, and
4
CA 02484674 2004-10-14
the manner of its implementation. The invention in its broadest and more
specific forms will
then be further described, and defined, in each of the individual claims which
conclude this
Specification.
SUMMARY OF THE INVENTION
to
[0020] According to the invention in a first variant, two linear detection
optical sensor
arrays, each having a plurality of directed pixel sensors, are positioned to
provide overlapping
fields of view in or substantially within a common, shared, planar field of
view. By
triangulation, the position of the object within the common field of view caa~
then be calculated.
I S Knowing the baseline between the two detection arrays and the angular
orientation in space of
the common field of view, the precise position in space of the object can be
calculated and the
time of its penetration of such field can be recorded.
[0021 ] The respective fields of view of the two linear detection arrays need
not be precisely
24 co-planar. If such ,fields of view are sufficiently proximate to each other
an object of finite
length may simultaneously be detected in both fields. Furthermore, taking the
hypothetical case
of an infnitely small object, floe consecutive detection of the object by the
first and second
arrays over a very short interval can be taken, as an approximation, as being
simultaneous. lxi
either case, by treating the respective fields of view as ifthey were
coplanar, the location of the
25 object in space can be calculated.
[0022] According to a feature of the invention, two linear detection arrays
may be said to
constitute a "set of arrays". By employing a pair of such sets, each set
providing respective,
shared, common fields of view, an accurate xzleasurement can be made of the
position of the
30 tracked object at two locations. This can be used to establish the local
trajectory or the line of
travel of an object. In the case of a launched projectile, e.g. a golf ball,
for which the takeoff
point is known, the initial parabolic path of such projectile can be
established without taking
time measurements. Recording the time between the successive intersections of
the object with
the respective common fields of view allows the object's immediate velocity to
be established.
35 This provides a further means for determining the initial parabolic path of
a projectile.
5
CA 02484674 2004-10-14
[0023] When the object penetrates the f rst common field of view of the first
set of position
sensor arrays, a first set of coordinates, x-coordinate as and y-coordinate h
is calculated by a
data processor based on data provided by such sensors. The same sequence of
events is
repeated when the object enters the second planar field of view and a second
set of coordinates
is calculated. The path of travel is defined by these values, so obtained. The
system described
so far in the present varianfi does not requaxe any time measurement to
calculate the object's
initial path of flight.
[0024] If the take-off point is known and the object's local velocity is
determined from the
two sets of measured coordinates combined with the time delay between
sightings, then the
data can be combined to define a projected, extended, trajectory and an
approximate landing
point. This can be done by using an algorithm that incorporates known
corrections for air
resistance. This trajectory may be displayed in a video presentation andJor
range and
directional data can be provided to the player through some form of display.
Possible displays
include visual displays and auditory displays amongst others
[0025] The associated sensor arrays in each set that monitor a shared, common
field of view
must be separated from each other so that their respective fields of view
intersect at an angle.
I3owever, two sensor arrays, each directed to monitoring a different field of
view, may be
mounted in a single, common support that fixes their angle of orientation to
each other. Thus
two pods, each containing two such angularly fixed arrays, array be zxzounted
on either side of
the object's flight path. This feature of mounting two angularly fixed arrays
in each pod
provides a fixed value for one of the parameters required for the analytic
analysis, namely the
angle between such arrays.
[0026] It is further necessary to know the orientations of the respective
common fields of
view. This may be achieved by mounting the arxays in an assembly which is
provided with
means for controlling the orientation and positions of the respective arrays,
and thereby
controlling the orientation and positions of their associated common fields of
view.
[0027] While the invention has been described is applicable to golf, baseball,
tennis training
and the like, it can be usefully employed in any situation wherever there is a
need to determine
the location of an object, in space, its velocity and its trajectory. It is
applicable to both
6
CA 02484674 2004-10-14
incoming and outgoing objects. The invention is also applicable to tracking an
incoming
projectile aimed at a target, suclras-a velziclc.
[0028) In the case of a 'return" activity, wherein a projectile's trajectory
is calculated in the
incoming and outgoing directions, data can be obtained during both the
incoming and outgoing
IO phases of the path followed by a struck object and used to produce a
combined output.
Examples of a situation in which this informarion would be invaluable are the
training of a
baseball, tennis, or cricket player, or the player of any sport in which a
projectile is struck by a
device. From this data, a display can be provided that indicates the e~ciency
of the blow
being struck that effects the return.
[0029] A further feature of the invention is that over-saturation of the
photosensitive array
due to excessive illumination, as by the sun, can be achieved by using
photodiode arrays with
an "anti-blooming" control as well as by the use of wave-length selective
optical filters and/or
photosensitive optical filtering that darkens when exposed to intense light,
i.e., an auto-
darkening, photochromic optical filter.
[0030] The foregoing sumrnarazes the principal features of the invention and
some of its
optional aspects. The invention may be further understood by the description
of the preferred
embodiments, in conjunction with the drawings, which now follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031) The figures accompanying this disclosure are summarized as follows:
[0032] Figure I is a pictorial schematic of the system of the invention
applied to golf
[0033] Figure 2 depicts a position sensor assembly in face view showing a
single sensor
axray.
[0034] Figure 3 depicts a set of two associated arrays whose fields of view
overlap to
provide a single position sensor zone.
[0035] Figure ~. illustrates the geometric principles for determination of the
ball's
coordinates within a single position sensor zone.
7
__ . . ~u,. R m..ri . , ~,~ ~~~..~,.~~.~ ,~,w. . a . . .~ ~",d_a~~~ .~~..
___~.
CA 02484674 2004-10-14
S [0036] Figtare 5 is a schematic of a sensor pod with two sensor arrays
mounted at a fixed
angle to each other and inclined away from the viewer to be direoted towards a
flight path.
[0037] Figure 6 shows the side view of the position sensor zones and of the
strike zone
plane in baseball for use in determining the accuracy of a pitched baseball.
IaESCRIPTION OF THE PREFERRED EMBODIMENT
[0038] Figure 1 illustrates the operation of the system as it tracks a golf
ball 1. Two sensor
pods 2, each containing two position sensor arrays 3, are installed with one
pod 2 on either side
of the target line 4 at a known separation distance. The "target Iine°'
is 'the line over which the
IS object to be sensed is expected to pass. The sensor pods 2 are connected
electronically by a
wire link 5 or a wireless link to the electronic processing unit 6. This unit
sends signals to a
display 7.
[0039] When the sensor pods 2 are aligned, the fields of view S generated by
each of the
respective position sensor arrays 3 in one sensor pod 2 preferably overlap
with the fields of
view of a corresponding position sensor array 3 in the other sensor pod. This
defines two
common planar position sensor zones A and B. The sensor arrays 3 which combine
to define a
sensor zone constitute an associated set of sensor arrays, with one membex of
the set being
present in each sensor pod 2.
[0040] As the golf ball 1 crosses these zones, the processor 10 in the
electronic unit 6
receives the data as to the location of the object within each zone A, B and
calculates by
triangulation, using standard geometric analysis, the coordinates of the
penetration points 9.
The electronic processor 10 also calculates the distance between such
penetration or points and
the ball's travel time between these points. Fxoxn this data, the processor IO
can determine the
ball's velocity vector including the'speed of the ball 1, the take-off angle B
with respect to the
horizontal plane, and the angular deviation of the flight path from the target
line 4 in the
horizontal plane. Using established ballistics data, the processor 10 can
estimate the ball's
projected trajectory and the range of the drive. Range calculations take into
account
aerodynamic effects acting on the ball 1 using known data and procedures.
'These calculations
8
CA 02484674 2004-10-14
can include the use of previously generated tables based upon the known
behaviour of objects
such as golf balls.
[0041 ] A description of the system's components and operation follows.
[0042] Each sensor pod 2 contains a set of two position sensor arrays 3, as
shown
individually in Figure 2 and collectively in Figure S. Each position sensor
array 3 consists of a
linear array of photodiodes or a charge-coupled device (CCD) providing data
inputs to a
processor 10 in the electronic unit 9. A sensor array 3 in one pad 2 is paired
with a senor array
3 in the other pod 2 to create a set of associated sensor arrays for ptxtposes
of detecting an
object present in their respective, shared, intersecting fields of view A, B,
[0043] The photodiode array 3 may be equipped with an "anti-bloomitxg"
control, i.e. an
operational feature that prevents over exposure of the diodes or the spill
over of excessive
charge from a pixel irradiated by the image of the sun to its neighbours on
either side. This
feature could be further enhanced by use of a wavelength selective band-pass
filter 12 or a
photochxomie, auto-darkening optical filter whose attenuation. increases when
exposed to
sunlight.
[0044) Known position sensor assemblies suitable for this application have
characteristics
similar to the device described as follows:
Lens characteristics . /1.8
Focal length . 3.8 mm
Detector . linear photodiode array
Number of diodes (pixels) . 512 (typically)
Width oflinear array . 0.013 mm
Diode pitch . 0.013 mm
Length of array . 6.656 mm
[0045] Each position sensor 3 has a fan-shaped field of view whose angular
dimensions are
82.4 degrees by O.I96 degrees, consisting of 512 detection zones (see Figure
2). Each pixel
9
CA 02484674 2004-10-14
detection zone 13 has angular dimensions of 0.161 ° (average) x
0.195°. The fields of view 8 of
the position sensors in each assembly are aligned to intersect substantially
within a common,
shared planar field of view, designated as position sensor detection zones A
and B in Figure 1.
This allows an object within the comxnon, shared planar field of view to be
located by a set of
polar coordinates overlaid on the shared planar field of view in position
sensor zones A and B '
{see Figure 3) as explained in the following description. The position sensors
face the luminous
sky and the target may appear either as a darker object against the lighter
background, or as a
lighter object against a darker background. In either case; its axrival causes
a change in the
intensity of tlxe light sensed by the respective sensor arrays 3.
[0045) When a ball 1. crosses position sensor zones A and B, its iixzage on
the photodiode
arrays 3 covers a certain nurxzber of pixels. As the processor in the
electronic unit scans each
a
array 3, typically at a minimum rate of 2 kI3z, it identifies the ball's
location in position sensor
zone A arid B by the differential effects created by the presence of the ball
I in the field of view
8.
[0047] The identification can be achieved by subtracting from each data bit
stream of a scan
the stored data bit stream of the preceding scan. Since the data of the
background illumination
remains the same during both scans, they are eliminated by this operation and
the remaining
singularity in the most recent frame is the image of the ball 1. The processor
10 in tlxe electronic
unit 9 determines the center of this image which it uses as the location of
the object. It then
calculates from the viewing angles cz and r3, (Figure 4), the x-coordinate a,
and y-coordinate h of
the object from the following equations in respective each of the sensor zones
A and B:
_ tan,8
a' Tatan/j+tany {1)
_ tank tang
a tan ~ -~- tan y {2)
[004$] As an example, a golf ball (1.6$ in. = 4.22 cm diameter) at a distance
or l.S rn
subtends an angle of 1.51 ° and its image on the detector arxay can
cover 10 to 11 pixels. It will
be assumed that angles ~ and can be measured with an r.zn.s. error of two
pixels; i.e. 0.322 °
. _.... "., m,x . . .., n ,, v~x...." , ,_.,._~~.~~~im .. ~ ~ ...... . "~M. __
~__...,-~~.~,.~,.....___ _... __.._~.~_ ~_~_._._ __.___.~.~. _ _ .. .
~~~ur~.-"~~..
CA 02484674 2004-10-14
= 0.00562 rad.. The corresponding errors dal and dll can be calculated from
the following
equations:
~ ; ~ a~ a1~~2 +~ a er~2
(3)
( a z
eh ~a~ ~Ij~ +Cay ~Y~
(4)
Where:
Bat _ tan y
a~3 y a eos2 ~3 (tan ~3 + tan y)2
(5)
~ _ _a tan ~'3
ay cosy y (tan/.3+tany~2
(6)
~h tans Y
a~ T a ~s2 ,B (tan ~3 + tan y)Z
f~)
_ah tan2,Q _
=a
8y cosay (tan~3+tany)2
($)
For , = I 6.0°, = 63.4° and a =1.5 m the following r.m.s, errors
were calculated:
ai=0.6 cm h =l.Ocm
The velocity vector of the ball 1 can be determined from the coordinates of
the penetration
points 9 in position sensor zone A and B, and the flight time between them.
[0049] The calculation of penetration points 9 in position zones A and B is
sufficient to
I S determine the golf ball's trajectory. This data alone can be provided to a
display to infornn a
player as to the direction of travel of a struck ball 1. To provide a read-out
of range, ~-ther
data must be acquired. The projected trajectory of a struck object is a
parabola that has to be
11
CA 02484674 2004-10-14
corrected for aerodynamic drag. Equation {9) describes a parabola which
intersects the x-
axis at point x = 0, the known location for the commencement of the golf
ball's trajectory.
This parabola also intersects the x-axis at x = rnln.
. Y - mx-- r~ f9)
IO
Using different parameters,
m = trxn8
n= G 12(vo'~cos B)a
1S where B is the take-off angle, G is the gravitational constant and va is
the ball's take-off
velocity.
[OOIO] The parabola can be defined if the parameters r~ and n are known. They
can be
calculated by substituting the coordinates 'of the two penetration points 9
into equation {9).
This operation results in two equations, which suffice to calculate the two
unknowns m and
20 n and thereby define the parabolic trajectory. A parabolic path can be
determined because
the point of origin or take-off point for the golf ball 1 is also known.
Consequently, the
trajectories of objects can be determined without measuring time so long as
the distance
along the target line 4 from the take-off point I4 to the base-line 2 5 is
known.
25 [0450] If this distance is not known, it ncaay be approximated by
projecting a line
through the penetration points g of the object back from detection zones A and
B to the
horizontal plane. The resulting intersection point is close to the origin
because the initial
part of the parabolic path can be approximated by a straight line. The
velacity determination,
based on the delay between penetration of the two saane~zA:,-T-t-can-be-used-
to calcuiate-tlie -- ~ w- --- w°'
30 parabolic path from which zange can thereafter be established.
jOQ51] If the distance to the take.-off point 14 is also known, calculations
may be
made using both methods and the results may be combined for unproved accuracy.
35 [DO52] The prajected trajectory can then be corrected for aerodynamic drag
by using
pre-calculated ballistic data that apply to a golf ball or baseball or the
like. Such data is
12
,""."...."". .-...."...,. r,. ., .,.,.:.... ".,..
,..,.,r,r:ame..watctt..,.,."aa~y.,.earnw.:~mm~rnrsexww~c..ca..mv~Mnx..n~" .
°.pMC:.v-:.~m.~mc..,."u,w--.....~.....,......e.,..."...xr".,.~ww.~-
v..ww.w.,.,."..;.,...vmw..,zn.~:... P.'3'~...saa.,...«s,"w-..~-..-
...._.....~..,~,.....,....._. ......_
~e.,r.
CA 02484674 2004-10-14
available from a number of sources and can be obtained in the case of a golf
ball, for
example, from P.W. $ehrman, 3.K. Harvey, Golf Ball Aerodynamics, Aeronautical
Cluarterly, p. 112-122, IVlay 1976_
[0053] The foregoing has been directed to calculating future traj~tories. The
past
trajectory of an arriving object can also be calculated, again using ballistic
analysis, to
determine the origin of an object of a known type arriving under its oven
momentum. This
can have military applications, as where it is desired to determine the firing
point of an
incoming hostile ballistic projectile.
The system configuration described offers the following features:
~ Four fields of view are merged in two planes (detection zones A and B),
simplifying the calculation burden.
~ 'The penetration paints in both zones and the distance between them can be
calculated by simple triangulation, independently of tune.
~ The flight trajectory can be modeled as a parabolic trajectory corrected for
aerodynamic drag without time measurements if the take-oi3F point is known,
but
time measurements can he taken into account to provide ari alternate
calculation
and increased accuracy.
, ~ To determine the velocity vector, two time measurements, as the ball
crosses
position sensor zones A and B, are required.
~ For a known object having known air resistance characteristics, a parabolic
trajectory corrected for aerodynamic drag can then be calcuiated_
~ The system is bi-directional, this means that it can measure all the above
3t) quantities regardless of flight direction, Ieft to right or right to left
with respect to
position sensor zones A and F.
~ Flight paths can be established for objects, both incoming and outgoing.
Description of a Sensor Pod
3S [0054] The sensor pod 2 is illustrated in Figure 5. It consists of a
weatherproof housing 15
fitted with two windows 16 and a handle 17 pierced by an opening (not seen in
Figure S). The
13
CA 02484674 2004-10-14
housing 15 contains two position sensor arrays 3 mounted in two planes,
typically at an angle
of 45 degrees with respect to each other and angled sideways to address the
flight path. This
configuration produces overlapping fields of view whereby sets of associated
arrays in each
sensor pod define the position sensor zones A and B. This is illustrated in
Figure 3.
j0055] An eaz~z anchorl mounting post 7 8, shown as a screw-threaded spike,
supports the
assembly. The mounting post ? 8 may be screwed into the ground by turning the
handle 17.
The housing I5 can be rotated on this support and locked in position by a
horizontal Lock 19 as
part of the alignment procedure. The support 18 may be equipped with a level
20, such as a
trapped air bubble, to ensure that the alignment takes place in a horizontal
plane. The support
may be mounted on a telescopic post with a vertical lock 21 allowing height
adjustments where
7 5 this is required. otherwise, the units are installed on a horizontal
surface.
[0056] The two sensor pods 2 are installed separated by a known distance apart
This can be
measured by using a wire or equivalent tether to serve as a base line 15.
Normally, the baseline
would lie a short distance in front of the take-off point 14, infiersected
approximately
centrally by the target line 14 i.e, the horizontal projection of the target's
path of flight. Data
from the sensox pods 2 to the electronic unit 9 can be transmitted either over
wire S or over a
wireless link. In the former approach a section of the wire link from the left
sensor pod 2 to the
right sensor pod 2 (Figure 1) can be installed under or with the base line 15.
[0057) The two sensor pods 2 can be installed, as an example, either at a golf
tee or in a
space reserved for golf practice, or in front of a batter's position, in the
following manner
(Figure 1):
1. A typically 2-m long aluminum or plastic base line 1S is placed
perpendicularly to the
target line 4 over which an object is to pass.
2. The posts 1$ axe inserted vertically in the ground or other support surface
at the ends of
the base line 15 by turning the handle 17 and relying on the level 20 as a
reference.
3. The sights 22, initially optionally folded in the handle 17, are then
erected, and the
sensor housings 15 are rotated until the sights 22 are aligned, The sensor
housings are
then locked in position by the horizontal lock 19. Tf vertical adjustments are
necessary,
they can be achieved by vertically displacing and locking the post's
telescoping parts
14
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CA 02484674 2004-10-14
S with the vertical lock 21. The horizontal alignment should be checked after
a vertical
adjustment to ensure it has not been disturbed. In are alternate alignment
procedure,
small lasers mounted in the handle could replace the pop~up sights.
[0058] Fallawing this installation procedure, the wiring li:nlcs are effected
and the
electronic unit 9 is switched on. All the ensuing calculations are based on
the distance
between the sensor pods 2 determined by the base line 15, the distance from
the take-off
point 14 to the base-line (if required} and the angles of the detected
projectile as measured
by the position sensors 3. As soon as a ball 1 crosses position sensor zones A
and B, the
electronic 9 unit can display the following data:
~ Speed,
Take-off angle in the vertical plane,
I3eviation from the target line in the horizontal plane,
~ Prnjected or hit range.
While it is well known that golf bails can curve significantly in flight,
knowing a projected
value for a been range can nevertheless provide a useful incentive for golfing
practice.
'[0059j The systen~z can be used for golf or batting practice i~ a restricted
space where a net
catches the ball. It can also be installed at a tee or baseball diamond and
display the above data
to each player participating ixi the game, as well as to an audience. l;uch
displays can include a
video.depiction ofthe projected trajectory, in real time.
[0060] In baseball, sensor pods 2 can be installed so that the detection zones
A,B lie in
the path of the pitched ball 23, preferably in front of the home base on
either side of the
reference Line running through the centre of tlxe pitcher's circle and the
centre of the home base
circle. The electronic 9 unit can then calculate the speed of the ball 23 as
well as its direction in
the horizontal and vertical plane both after being thrown by the pitcher and
after being hit by the
batter. This information can be displayed on the electronic unit and.
recorded, to be reviewed by
the coach, players and fans or posted instantaneously for all to view.
15
CA 02484674 2004-10-14
[0061 j Under controlled conditions, the system can be used to evaluate the
mechanical
characteristics of a bat, racket or the like by comparing the momentum of the
pitched ball to the
momentum of the ball after being struck. The display can include a
presentation of the ratio of
the outgoing speed to the incoming speed. It can also depict the direction of
the struck ball, both
vertically and horizontally.
[0052] Furthermore, the system zxxay be used to train a pitcher by creating in
space an
optronic strike zone 25, whose width is equal to that of the front rim of the
home plate (17 in.)
and whose height is equal to the distance between a hypothetical or real
batter's shoulder and
knees (approximately 3.5 ft). In an actual game, the stake zone 25 would have
to be adjusted to
x 5 accommodate each batter. For training pitchers, a standard, fixed strike
zone can be provided.
[0063] The corners of the rectangle of the strike zone are defined by
coordinates in a
vertical plane to which correspond values of al and h in position sensor zone
A. The latter
sensor zone A is inclined at an angle of 22.5 degrees with respect to the
vertical, as shown in
Figure 6. Iu the conversion from al and h coordinates in position sensor zone
A to the x,y
coordinates in the plane of the strike zone, al remains the same while h has
to be multiplied by
cos 22.5° = U.924. When a baseball 23 crosses position sensor zone A,
its coordinates are
calculated, converted to the coordinates in the plane of the strike zone 25
and compared to the
comer coordinates of the latter. While the center of the ball 23 is initially
tracked, allowances
for the width of the ball can be made. This sequence of mathematical
operations establishes
whether or not the baseball 23, or a portion of the baseball 23, has crossed
through the strike
zone 25. Observers can then be informed of the positive or negative outcome of
this event on an
alphanumeric or other display means.
j0064] In this scenario, the system plays the role of an electronic umpire.
The training
can be rendered more realistic by installing dummies made of elastic material
to serve as a
simulated batter and a catcher at the home base. The realism of the training
practice can be
further enhanced by placing at Ieast one additional set of two, of sensor
arrays, or preferably a
further pair of pods 2, one on either side of the center line extending
between the pitcher's circle
and the home base circle. In this configuration the systems can track a curve
ball and display the
top view of its trajectory relative to the strike zone 25 on a video screen.
16
CA 02484674 2004-10-14
CONCLUS10N
(0065] The foregoing has constituted a description of specific embodiments
showfng
how the invention may be applied and put into use. These embodiments are only
exemplary.
The invention in its broadest and more specific aspects is fiu~ther described
and defined in
the claims which now follow.
X0066] These claims, and the language used therein, are to be understood in
terms of
the variants of the invention which have been described. They are not to be
restricted to
such variants, but are to be read as covering the full scope of the invention
as is implicit
within the invention and the disclosure that has been provided herein.
17
