U.S. patent application number 10/385218 was filed with the patent office on 2004-06-17 for system and method for operating groups of lasers to project a visible line of demarcation within discrete regions of an athletic field.
Invention is credited to Amron, Alan, Dinicola, Brian K..
Application Number | 20040111904 10/385218 |
Document ID | / |
Family ID | 46299046 |
Filed Date | 2004-06-17 |
United States Patent
Application |
20040111904 |
Kind Code |
A1 |
Amron, Alan ; et
al. |
June 17, 2004 |
SYSTEM AND METHOD FOR OPERATING GROUPS OF LASERS TO PROJECT A
VISIBLE LINE OF DEMARCATION WITHIN DISCRETE REGIONS OF AN ATHLETIC
FIELD
Abstract
The surface of an athletic field is divided into multiple
regions or zones. A first of these zones is served by a first group
of laser sources. A second of the zones is served by a second group
of laser sources. Each group includes at least two lasers arranged
to project visible light onto the field from opposite lateral sides
of the field. The output from each group is focused onto the field
so as to form a composite line across the field--anywhere within
the associated zone. A controller is operative, in response to
receipt of a command from either a keyboard terminal or a wireless,
hand held user interface device, to select one of the first group
of laser sources and the second group of laser sources to project a
composite temporary visible line. The zones may be contiguous or
may be separated by one or more intermediate zones, with each
intermediate zone having its own associated group of laser
sources.
Inventors: |
Amron, Alan; (Syosset,
NY) ; Dinicola, Brian K.; (Monroe Twp, NJ) |
Correspondence
Address: |
Brian K. Dinicola
34 Avenue E.
Monroe Twp
NJ
08831-2316
US
|
Family ID: |
46299046 |
Appl. No.: |
10/385218 |
Filed: |
March 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10385218 |
Mar 10, 2003 |
|
|
|
10320304 |
Dec 16, 2002 |
|
|
|
Current U.S.
Class: |
33/289 |
Current CPC
Class: |
A63C 19/065 20130101;
A63C 2203/18 20130101; A63C 2203/22 20130101; G01C 15/004 20130101;
A63C 2019/067 20130101; A63C 2203/14 20130101; A63C 2203/12
20130101; A63C 2203/24 20130101 |
Class at
Publication: |
033/289 |
International
Class: |
G01C 015/00 |
Claims
What is claimed is:
1. An apparatus for providing at least one temporary visible
reference line on a non-smooth surface characterized by a tendency
to scatter incident visible light in random and non-uniform manner,
comprising: a first group of laser sources, including a first laser
source disposed at a first elevated location relative to the
surface, said first laser source being operative to emit a first
laser beam having a wavelength of between 400 nm and 750 nm and to
direct visible light from said beam along a selectable path upon
the surface so as to form a temporary visible line anywhere within
a first region of the surface, and a second laser source disposed
at a second elevated location relative to the surface, said second
laser source being operative to emit a second laser beam having a
wavelength of between 400 nm and 750 nm and to direct visible light
from said second laser beam along the selected path so as to form,
with light from said first laser beam, a composite temporary
visible line within the first region; a second group of laser
sources, including a third laser source disposed at a third
elevated location relative to the surface and to the same lateral
side of the surface as said first laser source, said third laser
source being operative to emit a third laser beam having a
wavelength of between 400 nm and 750 nm and to direct visible light
from said third laser beam along a selectable path upon the surface
so as to form a temporary visible line anywhere within a second
region of the surface, and a fourth laser source disposed at a
fourth elevated location relative to the surface and at the same
lateral side of the surface as said second laser source, said
fourth laser source being operative to emit a fourth laser beam
having a wavelength of between 400 nm and 750 nm and to direct
visible light from said fourth laser beam along the selected path
so as to form, with light from said third laser beam, a composite
temporary visible line anywhere within the second region; and a
controller, responsive to line projection commands, adapted to
selectively operate either the first group of laser sources or the
second group of laser sources so as to project a composite
temporary visible line on the non-smooth surface.
2. The apparatus according to claim 1, wherein each respective
laser source comprises a scanner for sweeping a corresponding beam
across the surface at a rate of at least 30 Hz.
3. The apparatus according to claim 1, wherein at least one of said
first laser source and said second laser source includes a
frequency doubled, Q-switched Nd:YAG laser adapted to generate
laser pulses at a wavelength of 532 nm.
4. The apparatus according to claim 1, wherein each of said laser
sources is adapted to generate a beam of at least 40 W.
5. The apparatus according to claim 1, wherein said controller is
responsive to user input commands to move the composite temporary
line from a first selectable path on a portion of the surface
within the first region to a second selectable path on a portion of
the surface within the second region.
6. The apparatus according to claim 5, wherein the first region and
the second region are contiguous.
7. The apparatus according to claim 1, wherein the beam output by
said first laser source is of a wavelength different than the beam
output by said second laser source.
8. The apparatus according to claim 1, wherein the first laser
source and the second laser source are located on opposite lateral
sides of the first region of the surface, and wherein the third
laser source and fourth laser source are located on opposite
lateral sides of first region of the surface.
9. The apparatus according to claim 1, wherein the composite
temporary line projected by the first group of laser sources is a
straight line having a length of about fifty three yards and a
width of from about four to about eight inches.
10. The apparatus according to claim 1, wherein a visible line
formed upon the first region of the surface by the first laser
source is a first series of individual line segments and a visible
line formed upon the surface by said second laser source is a
second series of individual line segments, said first and second
laser sources being operable to form collinear, offset line
segments with overlapping edges, whereby said composite temporary
line is visible as a contiguous solid line along a substantial
portion of its length.
11. The apparatus according to claim 1, further including a
wireless transceiver adapted to receive encrypted line projection
command signals from a remote, hand held device.
12. A method of projecting at least one temporary visible reference
line onto a non-smooth surface characterized by a tendency to
scatter incident visible light in random and non-uniform manner,
comprising the steps of: in a first receiving step, receiving a
first line projection command; in a first operating step, operating
only a first group of laser sources to project a visible line only
in a first region of the non-smooth surface in accordance with the
received first line projection command; in a second receiving step,
receiving a second line projection command; and in a second
operating step, operating only a second group of laser sources to
project a visible line only in a second region of the non-smooth
surface in accordance with the received second line projection
command.
13. The method of claim 12, further including a step of
transmitting a signal representative of the first line projection
command via a wireless link.
14. The method of claim 13, further including a step of encrypting
the first line projection command prior to said transmitting
step.
15. The method of claim 12, wherein said first operating step
includes operating said first group of laser sources to sweep at
least two coherent beams each having a wavelength of from 400 nm to
750 nm across the first region of the surface at a rate of at least
30 Hz.
16. The method of claim 12, wherein said second operating step
includes operating said second group of laser sources to sweep at
least two coherent beams each having a wavelength of from 400 nm to
750 nm across the first region of the surface at a rate of at least
30 Hz.
17. The method of claim 12, wherein the visible line projected
during the first operating step has substantially the same length
and width as the visible line projected during the second operating
step.
18. The method of claim 17, wherein the visible line projected
during each of the first and second operating steps has a length of
about fifty three yards and a width of about from four to eight
inches.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 10/320,304 filed on Dec. 16, 2002 and entitled
"SYSTEM AND METHOD FOR DYNAMICALLY MARKING ATHLETIC FIELDS USING A
HAND-HELD INTERFACE".
[0002] This application is also related to co-pending U.S. patent
application Ser. No. ______ filed simultaneously herewith and
entitled "SYSTEM FOR OPERATING ONE OR MORE LASERS TO PROJECT A
VISIBLE LINE ONTO A GRASS-COVERED SURFACE".
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention relates generally to the use of visible
reference lines during sporting or entertainment events and, more
particularly, to systems employing at least one laser light beam
source to generate such visible reference lines.
[0005] 2. Discussion of the Background Art
[0006] To accommodate a sporting event, a series of reference
and/or boundary lines may be defined upon a grass-covered surface
using, for example, paint, powders, dyes and the like. Such methods
of marking are entirely satisfactory so long as the reference lines
themselves are static during the entire event. Where the position
of a boundary or other line of demarcation changes dynamically
during the event, however, markings of the permanent type cannot be
used.
[0007] In the game of football, for example, a key objective of the
team in possession of the ball (i.e., the "offense") is to retain
possession of that ball by moving it far enough down the field.
Specifically, the offense is given a set of four plays or "downs"
to advance the ball by at least ten yards. Each time that distance
is reached or exceeded, the offense is said to have crossed a
"first down" line, a new set of downs is earned, and the offense is
allowed to continue its advance toward the goal line of the
opposing team (i.e., the "defense"). If the offense falls short,
however, possession is lost and the two teams reverse their roles.
A regulation football field has a length of 100 yards and 53 yards.
Thus, by way of example, a team gaining possession of the ball at
its own 20 yard line must move the ball a total of eighty yards in
order to reach the end zone of the opposing team.
[0008] In numerous occasions throughout an average football game,
the officials of the game must resort to sideline markers to
establish whether the offense has advanced the ball by the required
distance. The standard alignment system that is utilized is
generally a pair of poles connected by a 30-foot long chain. The
relative position of the football is measured by locating a first
of these poles at the approximate location of the initial line of
scrimmage and moving the second as far forward as possible. Each
time this measurement is made, the game must be delayed and the
yard markers must be carried from the sidelines to the place on the
field where the official has "spotted" the ball. Although the game
of football has become a relatively complex sport, involving
literally hundreds of millions of invested dollars, this time
consuming system has remained relatively the same since the
conception of the sport.
[0009] A number of approaches intended to ameliorate the
aforementioned deficiencies have been proposed over the years, but
none of them has met with any degree of commercial success. U.S.
Pat. No. 3,741,662, entitled "VISIBLE LINE MARKER" and issued to
Pioch on Jun. 26, 1973, U.S. Pat. No. 3,752,588, entitled "LASER
FOOTBALL FIRST DOWN MEASURING DEVICE" and issued to Chapman on Aug.
14, 1973, and U.S. Pat. No. 4,090,708 entitled "APPARATUS FOR
MARKING FOOTBALL FIELDS" and issued to McPeak on May 23, 1978. Each
of the aforementioned patents involves the use of lasers for the
purpose of marking visible lines of demarcation on an athletic
field. One of the principal drawbacks of these systems is the
time-consuming and tedious method of operation.
[0010] Both Chapman and Pioch involve the use of track mounted,
sliding projectors that are located at the sidelines and just a few
feet above the field level. The lasers are mounted for oscillation
in a vertical plane and the projected low intensity beam developed
by each must strike the field at points of reference lying on an
imaginary line of demarcation defined by the intersection of the
vertical plane with the field surface. Accordingly, it is necessary
for the operator to manually position the projector for each
reference point established. Like Pioch and Chapman, McPeak
discloses the use of a laser assemblies adapted to accommodate
sliding movement along the sidelines of a football field. McPeak,
however, teaches that two oppositely directed beams should be aimed
at a level above (i.e., "adjacent and parallel to") the field
surface.
[0011] Another drawback associated with the aforementioned systems
is that the low-intensity output of these lasers is far too low to
be visible by the players, let alone by an audience in, for
example, a stadium setting. Indeed, the aforementioned systems are
intended for use only in making a first down measurement
determination after each close play. As it turns out, players
intent on getting the ball past the first yard line--and focused on
the sideline markers long enough to be "blindsided" by the
defense--have either fumbled the ball or suffered very serious neck
and back injuries.
[0012] Television networks have recently implemented an image
pre-processing system which allows viewers of televised football
games to see a so-called "virtual" first down line that digitally
projects, in real time, a visible line onto video frames recorded
by the television camera, the line being displayed on a viewer's
television set so that it appears to extend between the first down
sideline markers. Unfortunately, neither the players, game
officials, nor the fans attending such games can actually see this
virtual line. It is thus reasonable to conclude that given the
rapid and widespread adoption of a virtual adoption of a virtual
visible line marking system--whose enjoyment is strictly limited to
television viewers, it has heretofore been assumed that it would be
impossible or impracticable to project a real, visible line onto
surfaces like those of athletic fields. Although there are many
possible explanations for this conclusion, it is believed by the
inventors herein that the poor light scattering properties of
grassy surfaces is at least partially to blame. Blades of grass are
randomly oriented and tend to scatter incident light in several
directions. The inventors herein have discovered that from
distances in excess of one hundred feet or so, a single beam of
even relatively high intensity (e.g., 40 joules/second) will be
reflected in such a way that it cannot be seen from most camera or
fan viewing angles within a stadium.
[0013] A continuing need therefore exists for a visible line
marking system that is simple to operate, accurate enough to allow
its use by officials at sporting events, and of sufficient
intensity to be viewed by players, large audiences, and television
viewers alike.
[0014] A need also exists for a system capable of projecting a
variety of other images, onto surfaces having non-uniform light
scattering properties, which can be seen from different
perspectives and from considerable distances even in daylight
conditions.
SUMMARY OF THE INVENTION
[0015] The aforementioned needs are addressed, and an advance is
made in the art, by an apparatus for providing at least one
temporary visible reference line on a surface, as for example, an
athletic field, within the field of view of at least one video
camera. An illustrative system constructed in accordance with a
first embodiment of the present invention comprises a first laser
source disposed at a first elevated, stationary location relative
to the surface, the first laser source being operative to emit a
first laser beam having a wavelength of between 400 nm and 750 nm
and to sweep the first laser beam along a selectable path upon the
surface so as to form a temporary line thereon. The system further
comprises a second laser source disposed at a second elevated,
stationary location relative to the surface and different from the
first stationary location, the second laser source being operative
to emit a second laser beam having a wavelength of between 400 nm
and 750 nm and to sweep the second laser beam across the selected
path so as to form, with the first laser beam, a composite
temporary visible line as, for example, a line of demarcation
during a football game.
[0016] It is expected that the power delivery requirements for each
laser source can vary considerably for each installation, depending
upon such variables as the range of expected ambient lighting
conditions, the distance each beam must traverse before contacting
the surface, and the actual width dimension of the line to be
displayed. For a line width of approximately 3 to 6 inches (8 to 15
cm), excellent results have been achieved from distances in excess
of several hundred feet using two 40 W, frequency doubled,
Q-switched Nd:YAG lasers each adapted to generate laser pulses at a
wavelength of 532 nm. Emission at this wavelength is especially
preferred since it is very close to the peak (555 nm) of the human
eye's sensitivity. By comparison, in an argon ion laser operating
in continuous wave (cw) mode, roughly half of the output is at 514
nm (58% as bright as the same beam at 555 nm), another 30% is at
around 480 nm (18% as bright) and the remaining 20% is at around
440 nm (barely visible to he human eye). Thus, such an argon laser
would have to deliver up to three or four times as much power to
match the visibility of an Nd:YAG laser.
[0017] The surface of the athletic field is divided into multiple
regions or zones. A first of these zones is served by the first and
second laser sources, these sources collectively comprising a first
group of laser sources. A second of these zones is served by third
and fourth laser sources, the third and fourth laser sources
collectively comprising a second group of laser sources.
Advantageously, the use of multiple groups of laser sources allows
the distance over which each beam must travel to be kept within a
range that is consistent with both the intensity and divergence
characteristics of the laser output and with the line width
criteria needed for proper viewing and accuracy for all positions
of the visible line. In accordance with an illustrative
installation of the present invention--a football field that is
subject to bright daylight illumination conditions--the first and
second laser sources are positioned beyond and above opposite
lateral sides of the 25 yard line on one-half of the field, and the
third and fourth laser sources are positioned beyond and opposite
lateral sides of the 25 yard line on the other half of the
field.
[0018] It should be emphasized that there is no requirement that
any pair of lasers be located along a line transverse and
perpendicular to the lateral sidelines of the field. Thus, for
example, the first laser source might be beyond and above the
twenty-yard line of a first lateral side of the field and the
second laser source might be beyond and above the thirty-yard line
of the second lateral side. Still another laser source might be at
the ten-yard line of either the first or the second line, such that
all or any two of them may be used to generate the composite line.
Preferably, however, the various laser sources are arranged so as
to cause the incident light from different beams to be scattered in
a way that allows spectators from as many different viewing angles
as possible to see the line clearly. In that regard, there is no
requirement that the respective laser sources be located at the
same elevated vertical position relative to the field. Needless to
say, it is considered within the level of skill of the ordinary
artisan to obtain, whether empirically or by predictive modeling, a
juxtaposition of laser sources that is ideally suited to the
specific lighting conditions and overall dimensions associated with
any particular indoor or outdoor location.
[0019] Based on the location on the field upon which the visible
line is to be projected, a control system determines which laser
sources are to be operated and in what order. For example, if an
official during a football game makes a determination that a new
first down has been established, then it may be required to move
the visible line from a position within one region of the field
surface, for which coverage is provided by one group of laser
sources, to a second region of the field surface that is covered by
a different group of laser sources. In accordance with present
invention, when the official inputs a line position command via a
wireless, handheld user interface, the control system operates the
respective groups of laser sources so as to seamlessly transfer the
line projection task from one group to the next.
[0020] Additional features and advantages of the invention will be
set forth in the detailed description which follows, and in part
will be readily apparent to those skilled in the art from that
description or recognized by practicing the invention as described
herein, including the detailed description which follows, the
claims, as well as the appended drawings. It is to be understood
that both the foregoing general description and the following
detailed description are merely exemplary of the invention, and are
intended to provide an overview or framework for understanding the
nature and character of the invention as it is claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention will be better understood by reference to the
detailed description of the invention that follows, taken in
conjunction with the accompanying drawings, in which:
[0022] FIG. 1 is a perspective view of a football stadium equipped
with a visible line marking system in accordance with an
illustrative embodiment of the present invention;
[0023] FIG. 2 is a partial perspective view of the football stadium
of FIG. 1, depicting the projection of a visible line of
demarcation (i.e., a "first down" line) onto a portion of the field
surface covered by real or artificial grass;
[0024] FIG. 3 is a block diagram schematically depicting the
components of an exemplary visible line marking system employing
two pairs of synchronized coherent laser sources;
[0025] FIG. 4 is a block diagram depicting, in greater detail, the
various functional elements of the exemplary visible line marking
system of FIG. 3; and
[0026] FIG. 5 is a flow chart depicting a sequence of operation for
the exemplary system depicted in FIGS. 3 and 4.
DETAILED DESCRIPTION OF THE INVENTION
[0027] The present invention is based, in part, on the recognition
that even non-smooth surfaces can reflect incident beams of
coherent light in a way that allows a line projected thereby to be
seen from most radial viewing perspectives. As used herein, the
phrase "non-smooth target surface" is intended to encompass any
surface that is characterized by a tendency to scatter incident
light in a random and nonuniform manner. In connection with the
exemplary football stadium installation depicted in FIGS. 1 and 2,
it will be understood that the term "non-smooth target surface"
refers to the surface of an athletic field that is entirely or
substantially covered by real or artificial turf grass. By
appropriate beam wavelength, output power level selection, and
placement of multiple groups of two or more laser sources, the poor
light scattering performance of such non-smooth surfaces can be
overcome so that spectators can easily see the line(s)
so-projected--from most, if not all, vantage points within the
seating area of a stadium or arena--even in peak daylight ambient
lighting conditions.
[0028] As used herein, the term "laser sources" is intended to
refer both to arrangements in which a coherent laser beam source
and scanning projectors are integrated into a single housing at a
common mounting location and to arrangements in which the laser
sources themselves consist of scanning projectors configured to
receive, via a waveguide (e.g., optical fiber) distribution
network, the output of a plurality or "bank" of lasers whose
respective beams are commonly coupled into a single waveguide for
delivery to any selected laser source. The term "laser sources"
should also be understood to encompass other line forming
arrangements besides those which rely upon the movement of mirrors
to implement a "scanning" operation. Alternate embodiments of the
present invention, for example, may employ laser sources in which
the coherent beam developed intersects a single lens element having
a negative optical power in one cross section and a positive
optical power in another cross section. One such lens element is
described in U.S. Pat. No. 6,069,748 entitled "Laser Line Generator
System" issued to Joseph Bietry on May 30, 2000. Unlike
conventional cylindrical lens arrangements--which provide for a
gaussian distribution of the energy, the Bietry lens arrangement
evenly distributes the optical energy across the entire width and
length of the line.
[0029] It should also be understood that although the exemplary
embodiments illustrated and described herein relate specifically to
the projection of a visible straight line onto the grass surface of
a football field, the teachings of the present invention are
equally applicable to the projection of other types of
lines--including images, logos, advertising messages, and the
like--onto any surface covered by real or artificial turf.
[0030] FIG. 1 is a partial view of an exemplary stadium 100 having
associated therewith a visible line marking system constructed in
accordance with the teachings of the present invention. In the
center of stadium 100 is an athletic field 102 covered with
grass--which can be either real or artificial turf grass--and
marked with a rectangular grid pattern to define a football playing
area. The width of this grid pattern is delineated by, inter alia,
first and second lateral boundary lines indicated generally at 103a
and 103b, which are separated by a distance of approximately
fifty-three yards. At regular increments of ten yards, eleven
transverse reference lines extend across field 102, interconnecting
first and second boundary lines 103a and 103b. Collectively, these
transverse reference lines define the one hundred yard area of
field 102 that separates the end zones 108 of each team.
[0031] Surrounding the grass-covered surface of football field 102
is a seating area, indicated generally at 104, designed to
accommodate a large number of spectators. As will be readily
appreciated by those skilled in the art, the seating area of a
typical professional league football stadium can easily accommodate
several scores of thousands of fans, and many college arenas
provide seating for at least tens of thousands. In that regard,
seating area 104 can consist of three or more distinct tiers as,
for example, a lower deck, mezzanine, and upper deck area. Between
seating area 104 and playing field 102 is a retaining wall 106,
which serves as a barrier between the spectators and the players
and officials on field 102. It goes without saying that the
spectators expect a substantially unobstructed view, from any seat
within seating area 104, of the action taking place on field
102.
[0032] A line marking system constructed in accordance with an
illustrative embodiment of the present invention includes a first
pair of laser sources indicated generally at 120a and 120b and a
second pair of laser sources indicated generally at 130a and 130b.
To ensure coverage of the entire length and width of the playing
area, each laser source is positioned at a location that is high
above the grass-covered surface of field 102--on the order of from
about fifty to about two hundred and fifty feet or so depending
upon the intensity, shape and divergence of the coherent beam
generated and upon the availability of a suitable mounting
location. Although it is certainly conceivable that certain
enclosed (e.g., domed) environments might offer a mounting location
that is directly above athletic field 102, each laser source as
sources 120a and 120b is typically mounted well beyond lateral
boundary lines 103a and 103b--on the order of, say, about fifty to
one hundred and fifty feet outside lines 103a and 103b. In the
exemplary embodiment of FIG. 1, for example, each laser source is
positioned directly above seating area 104, with care being taken
to ensure that the respective beams projected are sufficiently
distant from the spectators at all times as to comply with the
guidelines prescribed by the Center for Diagnostic and Radiological
Health, a department of the U.S. Food and Drug Administration. The
beam may therefore traverse a distance of hundreds of feet before
reaching the surface of field 102, and may do so at an angle of
incidence that is typically within a range of from about fifteen to
about ninety degrees.
[0033] Under certain ambient lighting and other installation
conditions, it is contemplated that a surface may be divided into
multiple regions or zones. This allows the distance over which each
beam must travel to be kept within a range that is consistent with
the intensity, divergence and line width demands for proper
viewing. By way of illustrative example in which the surface is a
football field that is subject to daylight illumination conditions,
first and second laser sources 120a and 120b are positioned above
opposite lateral sides of the 25 yard line to provide coverage for
half the area of field 102--a region designated as area 102b in
FIG. 3, while third and fourth laser sources 130a and 130b are
positioned opposite lateral sides of the 25 yard line on the other
half of the field, a region designated as area 102a in FIG. 3. Such
an installation decreases the maximum angle, relative to the
vertical, at which each beam strikes field surface 102. A beam
emitted by laser source 120a from a point 200 feet above a lateral
side of the 25 yard line will be disposed entirely in a vertical
plane relative to horizontal target surface 102b, and thus at an
angle of zero degrees relative to the vertical. A beam directed
from that same source but along a selectable path 25 yards away
(e.g., at the 50 yard line) will strike target surface at an angle
of twenty degrees relative to the vertical. To be useful as an
official line of demarcation in a football game, it is believed
that the angle should be no greater than 20 degrees. This is
because the tip of the football is three inches above the ground.
In the foregoing example, the trailing edge of the visible
composite line will cross the tip of the football about one inch in
front of where it actually crosses the field. The greater the
greater the angle, the greater the deviation.
[0034] As such, and in accordance with the illustrative embodiment
of the present invention depicted in FIG. 1, each pair of laser
sources is dimensioned and arranged within stadium 100 to provide
coverage for only a portion of the entire of the field area. As
best seen in FIGS. 2 and 3, laser sources 120a and 120b--in a
manner to be described shortly--are operated together so as to
jointly project, from two different angles, a composite visible
line 110 onto the field region 102b. As indicated above, by
appropriate beam wavelength, output power level selection, and
placement of the multiple laser sources, the poor light scattering
performance of the grassy field surface 102 can be overcome and
spectators can easily see the line so-projected from most, if not
all, vantage points within seating area 104--even in peak daylight
ambient lighting conditions.
[0035] A simplified block diagram of an illustrative visible line
marking system 10 constructed in accordance with the teachings of
the present invention is shown in FIG. 3. Essentially, system 10
includes a plurality of groups of laser sources, of which only a
first group (comprising first laser source 120a and second laser
source 120b) and a second group (comprising third laser source 130a
and fourth laser source 130b) are shown. It will readily
appreciated by those skilled in the art that any number of
intermediate groups of laser sources may be added, and the relative
spacing between the sources of all groups adjusted, in order to
ensure that the projected line 110 (FIG. 2) can be clearly seen
from all desired viewing angles.
[0036] In this regard, the inventors herein have observed that the
intensity of light reflected by grassy surfaces is subject to
substantial local variations depending upon the vertical and
angular position of the observer relative to the location where a
laser beam strikes a region of the target surface. In locations
where the amount of ambient illumination is relatively high such,
for example, a stadium whose grass field is exposed to full sun or
even bright incandescent lighting, light projected by a single
coherent laser source is reflected by the randomly oriented blades
of grass in such a way that it can be clearly seen from some
seating locations and barely seen from others. In accordance with
the present invention, the light from two or more beams, as beam
124 output by first laser source 120a and beam 122 output by second
laser source 120b, are used in order to ensure that the light
reflected by target surface 102b can be clearly seen from any
viewing location.
[0037] With continuing reference to FIG. 3, it will be seen that
the respective laser sources are controlled by host computer system
30, with which there are associated a monitor 22, a keyboard
terminal 36, a hand-held wireless interface for supplying line
projection position and operation commands via an RF link. In the
exemplary embodiment, the software that controls movements of the
beams developed by each laser source is configured to allow line
projection position and operation commands to be supplied by either
keyboard terminal 36 or by wireless interface 42 (via an RF link).
To make the most effective use of the capacity to implement line
position commands using keyboard terminal 36, monitor 22 is
configured to present a view (which may be an actual view taken by
video camera or a digitally simulated scene) of football field 102.
Alternatively, or in addition to the keyboard command capability,
commands for position the visible line are entered by wireless
interface 42 via an RF link. To prevent unauthorized interference
with the proper operation of system 10, wireless interface 42 and
wireless transceiver 43 are configured with the ability to encrypt
and decrypt the signals exchanged over the RF link established
therebetween. To ensure the operability of the system in a variety
of pre-existing stadiums and arenas where certain wireless
frequencies may already be assigned to use for other purposes, each
of wireless interface 42 and wireless transceiver 43 is further
equipped with a frequency selection switch by which the system
installer/operator can choose an available, non-interfering
transmission frequency from among a plurality of selectable
frequencies.
[0038] Typically, the wireless interface will be used by one of the
officials on the field charged with the task of establishing an
accurate position of the ball. There are situations in football
where the "spotted" position of the ball is automatically specified
to be the twenty yard line, as where the ball is punted or kicked
off into the end zone. In these cases, entry of the line projection
position command by the official requires nothing more than a
single button depression, system 30 being equipped with a
controller that receives the corresponding command and instructs
the appropriate group of laser sources to project the visible line
at the thirty yard line (i.e., ten yards from the spotted twenty
yard line). In cases where the position is not so defined, a two
step process is required.
[0039] A fine adjustment button or thumbwheel (not shown) of user
interface 42 is depressed until the trailing edge of the visible
line just contacts the forward tip of the football. As will be
explained in greater detail shortly, these movements are controlled
by a projection control board within host computer 30. Once the
official has properly defined the new line of scrimmage in this
fashion, he need only make one more button depression. That is,
user interface 42 is further equipped with a ten-yard increment
button which transmits a command to the projection control board
within host computer 30.
[0040] Turning now to FIG. 4, it will be seen that each laser
source as source 120a comprises first and second galvanic scanners
indicated generally at reference numerals 121 and 123,
respectively. Such scanners are found in conventional laser
projectors, and as used therein, galvanic scanner 121 controls
movement in the X-axis direction of a coherent laser beam developed
by beam generator 140.
[0041] Likewise, galvanic scanner 123 controls movement in the
Y-direction. Considering the width direction of field 102 between
boundaries 103a and 103b to constitute the Y-direction, a visible
line is generated by causing beams 122 and 124 (FIG. 3) to move
fast enough in that direction to create a composite temporary
visible line at a desired location on target surface 16.
[0042] Essentially, a composite visible line is formed at a desired
location by repeatedly and rapidly scanning target surface 102 with
each of beams 122 and 124 such that each beam strikes target
surface 16 at many points along a selectable path. An exemplary
selectable path is identified by reference numeral 110 in FIG. 2,
it being understood that a change in the specific location of the
temporary visible line--in this case a straight line across surface
102b--is implemented through operation of the respective X- and
Y-scanners of each of laser sources 120a and 120b. As will be
readily appreciated by those skilled in the art, each scanner as
scanners 121 and 123 includes mirror (not shown) that deflects the
beam. Working together, scanners 121 and 123 are operative to
direct the corresponding beam at any selectable point within
coverage region 102b so as to thereby generate a temporary visible
line thereon.
[0043] To enable accurate positioning of a visible line along a
selected path as path 110 (FIG. 2), scanners as scanners 121 and
123 are preferably closed-loop galvanic scanners (also called
"position detecting" scanners). Scanners of this type are commonly
used in the laser light entertainment industry and are compatible
with a wide variety of commercially available laser graphics
software packages.
[0044] Acceptable performance has been achieved using scanners that
are capable of directing the beam to 24,000 to 30,000 discrete
points along selected path 110 every second. Scanning assemblies
suitable for use in the present invention have been assembled, for
example, using two of Cambridge Technology's model 6800 scanners
and matching model 6580 amplifier circuit boards.
[0045] As a safety precaution, each laser projector preferably
includes a conventional shutter mechanism (not shown) such, for
example, as an acoustic optical modulator (AOM) for turning off the
beam in the event, for example, a malfunction prevents proper
movement of each scanning beam. In the event system 10 may be
called upon to create two or more distinct and unconnected visible
lines, the AOM's may also be used to implement a blanking function
whereby the beam is turned off as it moves between them.
[0046] Optionally, each laser source may further include a
conventional beam expander (not shown) in order to increase the
diameter of the beam or a conventional collimator (not shown) for
altering its divergence. In a typical stadium installation, it is
anticipated that laser sources as sources 120a and 120b will be
mounted anywhere from about 75 to about 200 feet above the level of
target field surface 102. Consequently, beams 122 and 124 will
traverse a considerable distance before striking surface 102b. As
will be readily appreciated by those skilled in the art, the need
for expansion or collimation of beams 122 and 124 is purely a
function of the initial beam diameter and the desired thickness of
the visible line as formed on the target surface. A more
challenging aspect of projecting beams over such distances,
especially in full sun illumination conditions, is that of finding
lasers capable of delivering coherent beams of sufficient power and
intensity to form a visible composite line.
[0047] For a line width of approximately six inches (15 cm),
excellent results have been achieved in a stadium environment
(i.e., from distances in excess of several hundred feet) using two
40 W, frequency doubled, Q-switched Nd:YAG lasers each adapted to
generate laser pulses at a wavelength of 532 nm. Emission at this
wavelength is especially preferred since it is very close to the
peak (555 nm) of the human eye's sensitivity. By comparison, in an
argon ion laser operating in continuous wave (cw) mode, roughly
half of the output is at 514 nm (58% as bright as the same beam at
555 nm), another 30% is at around 480 nm (18% as bright) and the
remaining 20% is at around 440 nm (barely visible to he human eye).
Thus, an argon laser would theoretically have to deliver up to
three or four times as much power to match the visibility of the
Nd:YAG laser. Notwithstanding the relative difference in
visibility, the inventors herein contemplate that one or more
ew-mode lasers can be used in conjunction with one or more pulse
mode lasers to provide a single, composite visible line, if
desired. Moreover, and with particular regard to an illustrative
embodiment that uses two laser sources to generate each visible
line, it is also contemplated that the first laser source may be
configured to deliver a beam which has a different power level than
the second laser source, and that the respective power levels may
be altered as necessary to compensate for different ambient
lighting conditions.
[0048] The use of Nd:YAG lasers has heretofore been regarded as
unsuitable for so-called laser graphics applications because they
tend to produce dotted, rather than continuous lines.
Advantageously, the use of two or more lasers in accordance with
the teachings of the present invention overcomes this apparent
deficiency by synchronizing the first and second laser sources such
that segments of the broken pattern of elliptical spots produced by
first laser source 120a overlap the broken areas between the
elliptical spots produced by second laser source 120b. The
resulting composite visible line appearing along selected path 110
thus appears to be continuous and unbroken to the human observer.
If desired, a cylindrical lens can be used to define the appearance
of each spot as a dotted line segment having a straight forward and
trailing edge.
[0049] In any event, and with continuing reference to FIG. 4, it
will be seen that the scanners associated with each corresponding
laser source are controlled by a single laser projector control
module, indicated generally at reference numerals 82, that resides
within host computer system 30. Essentially, single laser projector
control module integrates the combined circuitry of a number of
equivalent QM2000 controller boards marketed by Pangolin Laser
Systems, Inc., Orlando, Fla. Essentially, each QM2000 board
includes its own processor and memory storage resources, and is
configured to execute a special software program (Pangolin LD2000)
to directly control any single ILDA-compliant scanner unit. While
acceptable results can be achieved by designated one of these
QM2000 boards as a master controller to control the operation of up
to three other "slave"controller boards, the integration of
multiple such controller modules into a single board structure
allows command instructions received from the user interface to be
executed in real time. This, in turn, avoids the processing delays
which would be experienced when the processing power of the host
computer is used to receive, decrypt, and process the line
projection commands.
[0050] Master control module 82a is configured to assign specific
line projection tasks to the scanners (e.g., 121, 123) of each
laser sources 120a, 120b, 130a and 130b. Utilizing the Pangolin
LD2000 software package, it is possible to define a series of
"scenes" each corresponding to a discrete position of the visible
line to be projected. Alternatively, the entire field can be
modeled as a pattern of spots, and a data table constructed
according to which the operation of each laser source is controlled
to project the visible line at any location selected by the game
official.
[0051] Other components of host computer 30 include a conventional
central processor unit as, for example, an Intel Pentium 4 2.0 GHz
microprocessor unit, random access memory 86, a hard drive for
storage of the operating system and communications program needed
to define an interface between wireless user interface 42 and I/O
ports 90 via radio frequency (RF) transceiver 43. A set of MIDI
function commands input by local console 32 or wireless, handheld
user interface 42 cause the program executing on master projector
control module 82 to instruct an appropriate group of scanners to
move the beams as needed to adjust the visible, composite temporary
line from an initially selected position defined by a first "scene"
stored in RAM of module 82 and corresponding to a selectable path
as path 110 in FIG. 2, to a subsequently selected position defined
by a second scene. Thus, for example, in the context of an
illustrative football stadium installation, the temporary line may
be moved from an initial line of scrimmage--where a game official
has just "spotted the ball"--by a set distance of ten yards by the
mere depression of a single pushbutton of user interface 42. This
can also include moving the temporary visible line from an old line
of scrimmage, forward or backward, to a new line of scrimmage as a
result of a penalty assessed against one of the teams.
[0052] With reference now to FIG. 5, an exemplary sequence of
operating the illustrative visible line marking system depicted in
FIGS. 1-4 will now be described. The process is entered at step 202
wherein the RF link between the handheld interface used by game
officials to input line placement commands and the projector
controller board is monitored to detect whether any command signals
have been received. At block 204, a determination is made as to
whether a command has been received and if so, it is decrypted
(block 206) and supplied to the projection controller board (block
208). Data is read from RAM memory on board the projector control
module (block 210) and the appropriate set of laser sources needed
to generate the visible line at the location corresponding to the
input command are selected (block 212). The command signals needed
to operate the scanners at each laser source are transmitted by the
projector control module to the selected laser sources (block 214).
The visible line will continue to be projected at the initial
position unless and until a new command is received via wireless
transceiver 43 (FIG. 4). It will thus be readily appreciated by
those skilled in the art that when a new command is received
requiring the line to be moved from, for example, a position within
region 102b (FIG. 3) to a position within region 102(a), the
projector control module de-energizes first laser source 120a and
second laser source 120b, and energizes third laser source 130a and
fourth laser source 130b and supplies the latter with the command
signals needed to project the visible line at the newly specified
location.
[0053] It will be readily appreciated by those skilled in the art
that various modifications and enhancements are possible. It should
also be emphasized that there is no requirement that any pair of
laser sources, as first and second laser sources 120a and 120b, be
located along a line transverse and perpendicular to the lateral
sidelines of the field. Thus, for example, the first laser source
might be outside the first lateral side of field region 102b at the
twenty-yard line and the second laser source might be outside the
second lateral side of region 102b at the thirty-yard line. Still
another laser source of the same group might be outside the second
lateral side of region 102b at the ten-yard line, such that all or
any two laser sources of the group might be used to generate a
visible composite line in accordance with the present
invention.
[0054] Nor is their any requirement that the laser sources be
located at the same elevated vertical position relative to the
field. It suffices to say that it is considered to be within the
level of skill of the ordinary artisan to obtain, whether
empirically or by calculation, a juxtaposition of laser sources
that is ideally suited to the specific lighting conditions and
overall dimensions associated with any particular indoor or outdoor
location.
[0055] It will be apparent to those skilled in the art that various
modifications and variations can be 20 made to the present
invention without departing from the spirit and scope of the
invention. Thus, it is intended that the present invention cover
the modifications and variations of this invention provided they
come within the scope of the appended claims and their
equivalents.
* * * * *