U.S. patent application number 12/849477 was filed with the patent office on 2011-03-03 for marksmanship training device.
Invention is credited to George Galanis, Ashley Stephens, Philip Temby, Armando Vozzo.
Application Number | 20110053120 12/849477 |
Document ID | / |
Family ID | 43625458 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110053120 |
Kind Code |
A1 |
Galanis; George ; et
al. |
March 3, 2011 |
MARKSMANSHIP TRAINING DEVICE
Abstract
The present invention describes a marksmanship training
simulator including, a weapon capable of firing a laser, a screen
for projecting images including a background and a target thereon
using a background projector for projecting a background scene and
a target area projector for projecting a density of visible pixels
on the screen such that the target image is at better than
eye-limited resolution when viewed by the marksman through a and
wherein the contrast ratio of the target image formed by both by
the background and target area projector is substantially that of
the target area projector. The screen reflects the laser and there
is also a laser footprint detector directed to the target area
wherein the density of the detector pixels for receiving the
non-visible footprint and the intensity and size of the laser
footprint is such that there is a predetermined accuracy of the
detection of the location of the footprint.
Inventors: |
Galanis; George; (Edinburgh,
AU) ; Vozzo; Armando; (Edinburgh, AU) ; Temby;
Philip; (Edinburgh, AU) ; Stephens; Ashley;
(Edinburgh, AU) |
Family ID: |
43625458 |
Appl. No.: |
12/849477 |
Filed: |
August 3, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11414559 |
May 1, 2006 |
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12849477 |
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Current U.S.
Class: |
434/21 |
Current CPC
Class: |
F41G 3/2627 20130101;
F41J 5/10 20130101; F41G 3/2655 20130101; G09B 9/003 20130101; F41G
3/2694 20130101; G09B 19/00 20130101 |
Class at
Publication: |
434/21 |
International
Class: |
F41G 3/26 20060101
F41G003/26 |
Claims
1. A marksmanship simulator for the training of a marksman
including: a target area projector projecting a density of pixels
on the screen such that an individual pixel is not visible to the
vision assisted or vision non-assisted marksman, wherein the pixels
form a target image within the target area; a screen for receiving
and reflecting projected visible and non-visible radiation; a
background projector for projecting an image on the screen and over
a target area, wherein the contrast ratio of the target image
formed by both the background projector and target area projector
is substantially that of the target area projector.
2. A marksmanship simulator according to claim 1 further including,
a marksmanship training weapon for projecting a non-visible laser
footprint onto the screen; and a detector for detecting the
reflected non-visible laser footprint on the screen wherein the
density of the detector pixels for receiving the non-visible
footprint and the intensity and size of the laser footprint is such
that there is a predetermined accuracy of the detection of the
location of footprint.
3. A marksmanship simulator according to claim 2 further including
a processor for receiving the detector signal representing the
location of the non-visible laser footprint and also knowing the
location of the projected pixels of the background image and target
area and determining the location of the non-visible laser
footprint with respect to one or more of the pixels of either or
both the background image or the target area.
4. A marksmanship simulator according to claim 2 wherein the
detector is arranged to detect the non-visible laser only if it
lies near or within the target area.
5. A marksmanship simulator according to claim 1 wherein the
background projector maximizes the contrast ratio in the target
area by minimizing the brightness in the target area projected by
the background projector.
6. A marksmanship simulator according to claim 2 further including
a mechanism for moving both the target area projector and the
detector such that the detector is detecting the non-visible
footprint in or about the target area.
7. A marksmanship detector arrangement for use in a marksmanship
arrangement having a screen for receiving and reflecting projected
visible and non-visible radiation, a projector for projecting a
density of visible pixels on the screen substantially within a
target area and a marksmanship training weapon for projecting a
non-visible laser footprint onto the screen, including a detector
for detecting the reflected non-visible laser footprint on the
screen wherein the density of the detector pixels for receiving the
non-visible footprint and the intensity and size of the laser
footprint is such that there is a predetermined accuracy of the
detection of the location of footprint.
8. A marksmanship simulator for the training of a marksman having a
marksmanship training weapon for projecting a non-visible radiation
footprint including a target area image capable or reflecting
non-visible radiation, and a detector for detecting the reflected
non-visible radiation footprint from the target wherein the density
of the detector pixels for receiving the non-visible footprint and
the intensity and size of the laser footprint is such that there is
a predetermined accuracy of the detection of the location of
footprint.
9. A marksmanship simulator according to claim 8 wherein the target
area image is illuminated.
10. A marksmanship simulator according to claim 8 wherein the
target area image is illuminated by non-visible light.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 11/414,559, filed May 1, 2006, entitled
"Marksmanship Training Device."
FIELD OF THE INVENTION
[0002] The current invention relates to a simulator for training
small arms marksmanship skills which involve firing over long
distances and where the required angular movement of the barrel is
slow.
BACKGROUND OF THE INVENTION
[0003] There are numerous weapon simulator devices that have been
utilized for training marksmen and other personnel for combat
situations, as well as for law-enforcement. The technology enabling
the construction of such devices started becoming viable with the
introduction of solid-state electronics in the 1970's. Over the
last two decades the scientific community has conducted controlled
experiments in order to evaluate the effectiveness of these devices
for training and assessing marksmen. None of the experiments have
found evidence of any significant benefit for marksmanship
training, in particular the ability to locate a group of shots in
tight proximity onto a target. Furthermore, none of the studies
have found high correlations between marksmanship performance in
the simulator and that in the live environment (i.e., a marksman's
live-fire performance is not well-predicted by their performance in
the simulator). Such outcomes imply that these devices have limited
utility for training and assessing marksmanship skills. While the
scientific literature has highlighted these shortcomings, the
scientific community has tended to caution against over reliance on
the use of these simulators and have not identified any solutions
to these problems in terms of improvements to the simulator.
[0004] The task of marksmanship requires the use of very fine
perceptual-motor skills. In general, marksmanship tasks can be
divided into two types. The first type involves firing over long
distances at targets subtending small angles at the weapon (e.g., a
marksman firing at a static target on a rifle range at 100 metres,
or a sniper attempting to fire at a partially concealed man-size
target at several hundred metres). This type of task is best
conducted from the prone position mainly because this enables the
shooter to steady the barrel, and because engagement of the static
or slow-moving target does not require rapid angular movement of
the barrel of the weapon. The second type of marksmanship task
involves firing at close-range, fast-moving targets, such as occurs
in combat pistol tasks and in the recreational field of clay-pigeon
or skeet shooting. This latter task is typically conducted from a
standing position to give the marksman greater freedom of movement
and allow rapid angular movement of the barrel of the weapon.
However, these factors lead to less stability of the barrel, which
in turn leads to less accuracy in aiming the weapon and hence this
type of task is more often conducted over closer ranges.
[0005] Computer generated target imagery found in current small
arms simulators is limited by the resolution of that imagery which
is significantly lower than the eye-limited resolution of targets
on a live firing range and thus the degraded target results in
significant shortcomings in marksmanship performance. When training
marksman to aim, acquire and engage a target, it is important that
the limiting factor is the visual acuity of the marksman and not
visual artifacts in the simulated target image.
[0006] Marksmanship performance is often measured in terms of a hit
or miss of the target. It is acknowledged that hitting a target is
an important measure of performance in marksmanship training.
However, when undertaking marksmanship training, other important
measures include the extreme spread which is the distance between
the two most widely separated shots in a group of shots and shows
the ability of the marksman to maintain a consistent point of aim.
When specifying the accuracy requirements for the weapon aim-point
calculation in a marksmanship simulator, it should be apparent that
any measurement error should be insignificant compared to the
requirements of the marksmanship task being trained or assessed. In
current small arms simulators, the weapon aim-point and fall of
shot position locations are not calculated by the hit detection
systems to a level of precision sufficient to support the reliable
assessment and training of marksmanship skills, in particular for
shooting at targets over long ranges.
[0007] The invention described herein provides a method and
apparatus arrangement to overcome, or at least substantially reduce
the disadvantages and shortcomings in prior art by ensuring that
the marksman's performance is not confounded by (a) the quality of
the target image and/or (b) the accuracy of the weapon aim-point
determination.
[0008] Thus a simulator arrangement and method of use is described
for training marksmanship tasks which involve firing over long
distances and where the required angular movement of the barrel is
slow.
[0009] Additionally further advantages of the present invention
will become apparent from the following description, in connection
with the accompanying drawings, where, by way of illustration and
example, embodiments of the present invention are disclosed.
BRIEF DESCRIPTION OF THE INVENTION
[0010] In a broad aspect of the invention a marksmanship simulator
for the training of a marksman includes: a target area projector
projecting a density of pixels on the screen than such that an
individual pixel is not visible to the vision assisted or vision
non-assisted marksman, wherein the pixels form a target image
within the target area; a screen for receiving and reflecting
projected visible and non-visible radiation; a background projector
for projecting an image on the screen and over a target area,
wherein the contrast ratio of the target image formed by both the
background projector and target area projector is substantially
that of the target area projector.
[0011] In a further aspect of the invention a marksmanship
simulator further includes a marksmanship training weapon for
projecting a non-visible laser footprint onto the screen; and a
detector for detecting the reflected non-visible laser footprint on
the screen wherein the density of the detector pixels for receiving
the non-visible footprint and the intensity and size of the laser
footprint is such that there is a predetermined accuracy of the
detection of the location of footprint.
[0012] In yet a further aspect of the invention a marksmanship
simulator further includes a processor for receiving the detector
signal representing the location of the non-visible laser footprint
and also knowing the location of the projected pixels of the
background image and target area and determining the location of
the non-visible laser footprint with respect to one or more of the
pixels of either or both the background image or the target
area.
[0013] In yet a further aspect of the invention a marksmanship
simulator further includes a detector arranged to detect the
non-visible laser only if it lies near or within the target
area.
[0014] In yet a further aspect of the invention a marksmanship
simulator further includes a background projector which maximizes
the contrast ratio in the target area by minimizing the brightness
in the target area projected by the background projector.
[0015] In yet a further aspect of the invention a marksmanship
simulator further includes a mechanism for moving both the target
area projector and the detector such that the detector is detecting
the non-visible footprint in or about the target area.
[0016] In yet a further aspect of the invention a marksmanship
simulator further includes a marksmanship arrangement having a
screen for receiving and reflecting projected visible and
non-visible radiation, a projector for projecting a density of
visible pixels on the screen substantially within a target area and
a marksmanship training weapon for projecting a non-visible laser
footprint onto the screen, including a detector for detecting the
reflected non-visible laser footprint on the screen wherein the
density of the detector pixels for receiving the non-visible
footprint and the intensity and size of the laser footprint is such
that there is a predetermined accuracy of the detection of the
location of footprint.
[0017] In yet a further aspect of the invention a marksmanship
simulator further includes a marksmanship training weapon for
projecting a non-visible radiation footprint including a target
area image capable or reflecting non-visible radiation, and a
detector for detecting the reflected non-visible radiation
footprint from the target wherein the density of the detector
pixels for receiving the non-visible footprint and the intensity
and size of the laser footprint is such that there is a
predetermined accuracy of the detection of the location of
footprint.
[0018] In yet a further aspect of the invention a marksmanship
simulator further includes a marksmanship simulator wherein the
target area image is illuminated.
[0019] In yet a further aspect of the invention a marksmanship
simulator further includes a marksmanship simulator wherein the
target area image is illuminated by non-visible light.
[0020] It should be appreciated that the present invention can be
implemented in numerous ways, including as a process, an apparatus,
a system, or a computer readable medium such as a computer readable
storage medium or a computer network wherein program instructions
are sent over wireless, optical or electronic communication links.
It should be noted that the order of the steps of disclosed
processes may be altered within the scope of the invention.
[0021] Details concerning computers, computer networking, software
programming, telecommunications and the like may at times not be
specifically illustrated as such were not considered necessary to
obtain a complete understanding nor to limit a person skilled in
the art in performing the invention, are considered present
nevertheless as such are considered to be within the skills of
persons of ordinary skill in the art.
[0022] A detailed description of one or more preferred embodiments
of the invention is provided below along with accompanying figures
that illustrate by way of example the principles of the invention.
While the invention is described in connection with such
embodiments, it should be understood that the invention is not
limited to any embodiment. On the contrary, the scope of the
invention is limited only by the appended claims and the invention
encompasses numerous alternatives, modifications, and equivalents.
For the purpose of example, numerous specific details are set forth
in the following description in order to provide a thorough
understanding of the present invention. The present invention may
be practiced according to the claims without some or all of these
specific details. For the purpose of clarity, technical material
that is known in the technical fields related to the invention has
not been described in detail so that the present invention is not
unnecessarily obscured.
[0023] Throughout this specification and the claims that follow
unless the context requires otherwise, the words `comprise` and
`include` and variations such as `comprising` and `including` will
be understood to imply the inclusion of a stated integer or group
of integers but not the exclusion of any other integer or group of
integers.
[0024] The reference to any background or prior art in this
specification is not, and should not be taken as, an acknowledgment
or any form of suggestion that such background or prior art forms
part of the common general knowledge.
[0025] Specific embodiments of the invention will now be described
in some further detail with reference to and as illustrated in the
accompanying figures. These embodiments are illustrative, and not
meant to be restrictive of the scope of the invention. Suggestions
and descriptions of other embodiments may be included within the
scope of the invention but they may not be illustrated in the
accompanying figures or alternatively features of the invention may
be shown in the figures but not described in the specification.
BRIEF DESCRIPTION OF THE FIGURES
[0026] FIG. 1 depicts a marksmanship simulator arrangement of an
embodiment of the invention;
[0027] FIG. 2 depicts alternative arrangements according to
embodiments of the invention for projecting the target image onto a
screen;
[0028] FIG. 3 depicts prior art projection of the background and
target image using a background projector;
[0029] FIG. 4a depicts prior art target area resolution and target
image as displayed by the background projector and as seen by a
marksman;
[0030] FIG. 4b depicts target area resolution and target image as
displayed by the target projector wherein the target image is at
better than eye-limited resolution as seen by the marksman
according to an embodiment of the invention;
[0031] FIG. 5 illustrates the geometry associated with the
calculation of the maximum projected pixel size to achieve an eye
limited resolution of the target area;
[0032] FIGS. 6a and 6b show light intensity plots on the simulator
screen for purposes of illustrating the effect of two projectors on
the contrast ratio of the background and target area images;
[0033] FIG. 7 depicts prior art detection of the laser
footprint.
[0034] FIGS. 8a, 8b and 8c depict the characteristics of the laser
footprint where the size of the laser footprint is larger than that
of each detector pixel, and the pixel intensity before and after
application of a suitable threshold;
[0035] FIGS. 9a, 9b and 9c depict the characteristics of the laser
footprint where the size of the laser footprint is smaller than
that of each detector pixel, and the pixel intensity before and
after application of a suitable threshold;
[0036] FIG. 10 depicts detection of the laser footprint for an
embodiment of the invention.
[0037] FIGS. 11a and b depict the characteristics of the laser
footprint for one embodiment of the invention where the size of the
laser footprint is larger than that of each detector pixel, and the
pixel intensity before and after application of a suitable
threshold;
[0038] FIGS. 12a and b depict the characteristics of the laser
footprint for one embodiment of the invention where the size of the
laser footprint is smaller than that of each detector pixel, and
the pixel intensity before and after application of a suitable
threshold;
[0039] FIG. 13 depicts a flow diagram of the hit detection
process;
[0040] FIG. 14 illustrates the pixel intensity before the
application of a suitable threshold as described in FIG. 13;
[0041] FIG. 15 illustrates the pixel intensity after the
application of a suitable threshold as described in FIG. 13;
[0042] FIG. 16 depicts a geometric representation of steps 8-13 in
the hit detection process for FIG. 13;
[0043] FIG. 17 depicts the output provided by the processor as
feedback to marksman and instructors.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0044] As mentioned previously, the target image is preferably
presented to the marksman at better than eye-limited resolution. In
the context of a marksmanship simulator, the term "eye-limited
resolution" is taken to mean a simulated target image of such
quality that when a marksman, with normal (that is 20/20 vision),
looks through the simulator aiming device sees a target that does
not have any additional visible artifacts that are not present in
the equivalent real-world target. In particular, with regards to
this invention, such an image is provided under those conditions
when the marksman can not detect individual picture elements (in a
digital display the term pixel is used to describe such an
element). The image seen by the marksman is thus absent of any
indication that it has been generated electronically even though it
will be understood by the marksman that the image has been
projected from an electronic image generating device.
[0045] Referring to FIG. 1 an embodiment of one aspect of the
invention is depicted, including a marksmanship training weapon 1
for projecting a non-visible laser footprint onto the screen 6. The
weapon is shown with an eye-sight aim assistance device, typically
referred to as a sight 2, for viewing the target image 19. The
target area 8 contains an image 19 which can be viewed through the
sight 2 of the weapon 1 to give a field of view 10. The weapon 1
includes a laser that emits radiation in the form of a non-visible
laser beam (although other forms of radiation may be useable) from
the barrel 3 of the weapon which strikes the screen 6 which
receives and reflects the projected non-visible laser footprint,
the footprint 7 being preferably, according to the skill of the
marksman, within the target area 8.
[0046] A target area 8 can be projected anywhere on the screen 6 by
the target area projector 16, this may be a bulls-eye or other type
of target used for marksmanship training (animate or inanimate
object) along with a suitable background image 9 (none specifically
shown).
[0047] A background projector 4 projects an image 9 on the screen 6
and invariably also over the target area 8, in this embodiment the
background projector is Sony CX70 Ultra Portable LCD Data
Projector, AV Central, Adelaide, South Australia; a target area
projector (Sony CX70 Ultra Portable LCD Data Projector, AV Central,
Adelaide, South Australia), (target area projector 16) projects on
to the screen substantially within the target area 8, a density of
visible pixels on the screen such that the target image is at
better than eye-limited resolution when viewed by the marksman
through the sight 2, and as will be described in greater detail
later in the specification, wherein the contrast ratio of the
target area formed by both by the background projector 4 and target
area projector 16 is substantially that of the target area
projector 16 so as to provide the best possible target image to the
marksman.
[0048] Continuing reference to FIG. 1, in this embodiment, a
non-visible radiation detector (in this embodiment a laser
footprint detector) 18 is directed to detect the target area 8 on
the screen 6. The detector (in this embodiment a Photron PCI 512
Fastcam, Blink Technology Australia, Pty Ltd) for detecting the
reflected non-visible laser footprint on the screen is arranged
such that the density of the detector pixels for receiving the
non-visible footprint and the intensity and size of the laser
footprint is such that there is a predetermined accuracy of the
detection of the location of the footprint as described in greater
detail later in the specification. To determine the parameters of
the density of the detector pixels and the intensity and size of
the laser footprint requires consideration of the measurement
accuracy required for the marksmanship task being trained or
assessed. For example, a pass/fail criterion may be the requirement
to achieve an extreme spread less than 200 mm when shooting at a
target at 100 m on the live range. This would then lead to the
requirement to discriminate between extreme spreads over a range
encompassing values below and above this pass/fail criterion. This
leads to a requirement to be able to discriminate to well below the
pass/fail criterion. In this example this could be approximately
25% of the pass/fail criterion (that is 50 mm). The measurement
accuracy required to achieve this level of discrimination
consequently may be an order of magnitude better than the 50 mm
task requirement; that is the detection system would be required to
have a measurement accuracy of equivalent to 5 mm on a real target.
In a marksmanship simulator, where the marksman may fire at a
distance of 10 m from the screen, by geometry (similar triangles),
the measurement accuracy requirement in the simulator would
therefore be 0.5 mm.
[0049] The detection process in one embodiment uses a processor 11
which is connected to both the background projector 4, the target
area projector 16, and in particular the laser footprint detector
18 so as to determine the weapon aim-point of the marksman. It is
not necessary for the target area projector 16 to be located
adjacent the laser footprint detector 18, however, the respective
projection and detection areas on the screen 6 should be coincident
on the screen. There may be some circumstances where these areas do
not align for one reason or another, an example being where a
portion of the screen needs to be assessed as to whether a laser
actually missed the target area.
Image Resolution
[0050] There are a number of ways that a marksmanship simulation
arrangement can be achieved using the above elements, but one
arrangement is to use a marksmanship training weapon 1 for
projecting a non-visible laser footprint onto the screen 6 and a
background projector 4 dedicated to projecting the background image
and which invariably overlays the target area. The target area
projector 16 for projecting target image 19 in target area 8 is
superimposed over that portion of the background image 9 which has
been generated by the background projector 4. Other features and
advantages can be provided by using one or more other elements such
as controlling the movement of the target area within the projected
background image while co-coordinating the detection of the target
area with the laser footprint detector.
[0051] The resolving power of the human eye is approximately one to
two minutes of arc, and can vary between individuals around that
average value. Therefore each pixel in the target area image
subtends no more than 1 minute of arc in order for this image to be
at eye-limited resolution from the marksman's viewpoint. This can
be achieved by positioning the target area projector 16 relatively
close to the screen in comparison to the background projector.
Alternatively, the target area projector 16 may be positioned
further from the screen, but with an optical device 20 that focuses
the whole image onto a smaller area; these arrangements are
depicted in FIG. 2. The latter solution may be preferred when
shooting at targets simulated to be at very long ranges (e.g., 1000
m). These solutions result in the size of the pixels making up the
target image to be small enough so as to not be resolvable by a
marksman with normal vision when looking through the sight 2.
[0052] A further aspect of the invention is the sole use of a
detection of the laser footprint on a target image within a target
area by a detector 18. In one detection arrangement, the laser
footprint is smaller than the detector pixels and the detector
outputs a signal representative of the location of the detected
non-visible laser footprint relative to the pixels of the detector.
The footprint location can then be used to determine the accuracy
of the marksman for a single shot as well as for determining the
extreme spread and other performance measures from multiple
shots.
[0053] Various other detection arrangements are also possible,
including where the detector pixels are larger than the laser
footprint, but detection techniques can still resolve the location
of the footprint to an accuracy which allows for single and
multiple shot determinations of the marksman's accuracy within the
pre-determined accuracy as described earlier.
[0054] Details of the arrangement of specific embodiments of the
projector/s and detector will be described in greater detail later
in the specification.
[0055] Illustrative of the inaccuracy of prior art, FIG. 3
illustrates the prior art projection of the background image
including the target image to illustrate the limitations in target
imagery.
[0056] A projector 4 generates a background image including a
target image 9 on the screen 6. The target image can be projected
anywhere on the screen 6 by the projector 4. The target image 9
covers only a few projector pixels in the target area 8.
[0057] Referring to FIG. 4a the upper image is illustrative of the
pixel density of target imagery in the prior art and in the case of
FIG. 4b the upper image is illustrative of a representative and
comparative embodiment of the invention having a much higher pixel
image density than depicted in FIG. 4a. The lower images in FIGS.
4a and 4b are illustrative of the view of the target image by the
marksman either unassisted or assisted by the use of a weapon
sight. The lower image in FIG. 4a is a picture of an actual
digitally projected image of a target from a prior art simulator
and clearly contains visible unwanted artifacts introduced by the
pixilated view of the low resolution projected target image of the
prior art. No such artifacts are visible in the better than
eye-limited resolution target image projected by the target
projector in the representative embodiment of the invention.
[0058] The geometric calculation provided in FIG. 5 is based on the
formula for calculating for the maximum projected pixel size to
achieve eye-limited resolution;
.PHI.=2a tan [d/(2D)]
.theta.=m.PHI.=2a tan [d/(2D)]
Where m=magnification of the sight D=distance between marksman's
eye and the screen d=maximum distance between the centre of
adjacent pixels .theta.=angle subtended by a pixel as viewed by the
marksman and is set to be 1 minute of arc (0.291 milliradians) such
that the pixels are at eye-limited resolution
[0059] Hence, the maximum size of a pixel (d) for producing a
target at eye-limited resolution for a given distance from the
screen D is:
d = 2 D tan [ .theta. / ( 2 m ) ] = D .theta. / m for small values
of .theta. . = D .times. 2.91 .times. 10 - 4 / m . ##EQU00001##
[0060] Using the above equation for one embodiment of the invention
in which D=10 metres yields d=2.91 mm/m. In one embodiment of the
invention, magnification m may range from 1 to 10. The target area
projector (Sony CX70 Ultra Portable LCD Data Projector, AV Central,
Adelaide, South Australia), has a native resolution of
1024.times.768. Hence, the maximum area that can be projected by
the target area projector such that the target image is at
eye-limited resolution ranges from 2980 mm.times.2235 mm (m=1) to
298 mm.times.224 mm (m=10). In this embodiment of the invention,
typical target images are tens of mm across and hence the invention
readily achieves eye-limited resolution target imagery. The target
area projector is placed approximately 1 metre from the screen and
achieves a field of view approximately 0.75 metres.times.0.6
metres. Hence d is approximately 0.7 mm which yields an eye-limited
resolution target image up to a magnification of .times.4 for a
marksman positioned 10 metres from the screen. Eye-limited
resolution target images at greater magnifications may be achieved
in an alternative embodiment of the invention wherein an optical
device focuses the whole image onto a smaller area; as depicted in
FIG. 2.
[0061] FIGS. 6a and 6b depict a graphical illustration of the light
intensity falling along a straight line cross section on the screen
in the vicinity of the target image. The maximum contrast ratio
that the projection and screen system is capable of producing can
be determined by projecting a test image where the light
intensities rise and fall through the minimum and maximum
intensities across several pixels for the background and target
projectors producing a checker board effect on the screen. FIG. 6a
left shows the case where only the target projector is projecting
this test image onto the screen. FIG. 6a right, shows the case
where only the background projector 4 is projecting the test image
over the entire screen, and the graph shown in the figure is
showing the intensity plot in the region of the target image. For
the purpose of this description it is assumed that the target area
projector has been dimmed such that the maximum intensity of light
falling on the screen is very nearly equal to the light intensity
of the background projector. Since the light output of the target
area projector is focused into a small area on the screen, the
light intensity in the target area will be reduced to match the
light levels of the background image where the light output of the
background projector is spread over the entire screen. To achieve
such balancing between projectors of roughly similar light output
capabilities, the target area projector light settings are set low
enough to match the light intensity of the background image. If the
target area projector does not have sufficient range to achieve
this, then a neutral density filter can be placed in front of the
target area projector lens to further reduce the light output of
the target area projector.
[0062] The maximum light intensity of the target image (6a left) is
denoted by I.sub.maxt and the minimum light level by I.sub.mint. In
a similar way, the maximum light intensity of the background image
(6a right) is denoted by I.sub.maxb and the minimum intensity of
the background image is given by I.sub.minb. The contrast ratio of
the target image (with only the target area projector, 6a left) is
given by I.sub.maxt/I.sub.mint; and the contrast ratio of the
background image is given by I.sub.maxb/I.sub.minb.
[0063] FIG. 6b depicts the effect of superimposing images from the
background projector and the target area projectors in the area of
the target image, where on the left of FIG. 6b both projectors are
modulated through their full range of intensities across several
pixels. FIG. 6b on the right shows the case where the target area
projector is producing light intensities through its full range,
whereas the background projector is emitting minimal light
intensity.
[0064] With reference to FIG. 6b left, if the maximum and minimum
intensities across a distance encompassing several background
projector pixels are taken, the background contrast ratio, R.sub.b
is given by:
R.sub.b=(I.sub.maxt+I.sub.maxb)/(I.sub.mint+I.sub.minb)
[0065] However the target contrast ratio can be determined by
taking the ratio of maximum and minimum intensities over a smaller
distance, encompassing a distance that contains only several pixels
of the target project. With reference to FIG. 6b left, in the
regions of 25 mm, 35 mm, 45 mm (where the maximum light intensities
of the background projector occur), the contrast ratio is given
by:
R.sub.tmax=(I.sub.maxt+I.sub.maxb)/(I.sub.mint+I.sub.maxb)
[0066] With reference to FIG. 6b right, where background projector
4 is producing minimal light intensity, while the target image
projector is producing its maximum contrast the contrast ratio is
given by:
R.sub.tmin=(I.sub.maxt+I.sub.minb)/(I.sub.mint+I.sub.minb)
[0067] For the purposes of illustrating the concepts of contrast
ratio and without loss of generality, if the two projectors were of
matched brightness and contrast specifications and the intensities
of the target and background images on the screen were matched by
use of a suitable light filter placed in front of the target area
projector, then I.sub.maxt and I.sub.maxb can be replaced by
I.sub.max (I.sub.max being the maximum screen intensity that can be
produced by each projector). Similarly I.sub.mint and I.sub.minb
can be replaced by I.sub.min (I.sub.min being the minimum screen
intensity that can be produced by each projector). The contrast
ratio equations then become:
R.sub.b=(I.sub.max+I.sub.max)/(I.sub.min+I.sub.min)=(2I.sub.max)/(2I.sub-
.min)=I.sub.max/I.sub.min
[0068] That is the contrast ratio over several background pixels is
for the intents and purposes of this disclosure, approximately
equal to the contrast ratio of each individual projector pixel.
[0069] However, the contrast ratios across a few target image
pixels are given by the following equations. In the region where
the background image projector is producing a maximum intensity the
contrast ratio is:
R tmax = ( I max + I max ) / ( I min + I max ) = 2 I max / ( I min
+ I max ) = 2 / ( I min / I max + 1 ) = 2 / ( 1 / R + 1 )
##EQU00002##
[0070] In the region where the background image projector is
producing a minimum intensity the contrast ratio is:
R tmin = ( I max + I min ) / ( I min + I min ) = ( I max + I min )
/ 2 I min ) = 1 / 2 ( I max / I min + 1 ) = 1 / 2 ( R + 1 )
##EQU00003##
[0071] Typical contrast ratios of projection systems in a darkened
room can be of the order of 500:1 or greater. For the purposes of
illustration consider the case of using background and target area
projectors that both have contrast ratios R of 500. The contrast
ratio performance across the region of several background projector
pixels is given by R.sub.b and is thus 500. That is the use of two
projectors does not adversely affect the contrast achievable over
several background pixels or greater.
[0072] However, taking the illustration further, the target image
contrast ratio in the region of maximum background intensity is
given by:
R.sub.tmaxb=2/(1/R+1)=2/(1/500+1).apprxeq.2 (since 1/500 is much
smaller than 1)
[0073] That is an R.sub.tmax of two implies that the high
resolution detail from the target image is washed out by the
low-resolution of the background projector if the light intensity
of the background projector is high in the target image area. The
contrast ratio in the region where the background projector is
generating minimum intensity is given by:
R.sub.tminb=1/2(R+1)=1/2(500+1)=1/2R.apprxeq.250
[0074] Hence by using two projectors although a higher spatial
resolution can be achieved in the target image, the contrast ratio
is, in the best case halved, and the requirement to achieve this
performance is that the background projector must produce minimal
intensity and contrast in the region of the target area.
[0075] Hence in selecting projectors the simulation engineer should
select a background projector that has specifications for producing
regions of black that emit the lowest level of light possible.
However because the target projector has its light output
concentrated into a small region of the screen, the maximum
brightness specification of the target projector is less critical,
but because of the contrast ratio of the target image is diminished
by the light leaking when the background projector is emitting
"black" the target-projector would benefit by having a better
contrast specification than the background projector.
[0076] In another embodiment of the invention which does not
include a screen or background projector, a marksmanship simulator
for the training of a marksman having a marksmanship training
weapon for projecting a non-visible radiation footprint can
include, a target area image capable or reflecting non-visible
radiation. In one specific example this could be a printed
photographic image of a target (an inanimate target) which is
located a distance from the marksman. In one arrangement the target
could be at a similar distance to the target image used in other
embodiments.
[0077] In this arrangement the detector for detecting the reflected
footprint on the target includes a density of detector pixels for
receiving the non-visible footprint, and the intensity and size of
the non-visible radiation footprint is such that there is a
predetermined accuracy of the detection of the location of the
footprint.
[0078] In the above embodiment the marksmanship simulator includes
a means of illuminating the target. Illumination could be
non-visible light for night marksmanship training usable in
conjunction with night vision systems by the marksman. Further
radiation in the visible range can be used to increase the visible
intensity of the target during simulated daytime marksmanship
training.
Hit Detection
[0079] Modern small arms simulators rely on a single hit-detection
camera 20 to detect the laser footprint 7 anywhere over a wide area
of the screen 6 as depicted in FIG. 7. In some cases, where systems
allow multiple firers, several cameras may be employed for the same
purpose (e.g., multiple cameras for multi-lane systems). The
position of the laser footprint is then correlated to the position
of the target. The hit-detection system sees the screen as a set of
distinct blocks, as pictorially represented in FIG. 7, each block
typically referred to as a pixel 14. In this instance, each pixel
represents the projection of the camera sensory elements onto the
screen (as distinct from the pixels of the projected imagery).
[0080] Typically a computer associated with the hit-detection
sensor forms the hit-detection system, and uses the detected
intensity and coordinate position of the detection pixels
illuminated by the laser footprint (7 in FIG. 7) to calculate the
laser footprint position and hence the weapon aim-point. The
accuracy of this calculation is dependent on three factors; the
size of the detector pixels for receiving the non-visible footprint
and the intensity and size of the laser footprint. This is
illustrated in FIGS. 8a, 8b, 8c, 9a, 9b and 9c which demonstrate
different examples in which these three factors are varied.
[0081] FIG. 8a shows the case where the size of the laser footprint
is larger than that of each detector pixel. In this case, the
hit-detection system will calculate the laser footprint position by
determining the footprint centroid which is the intensity weighted
average of the coordinate positions of each pixel, where the
intensity at each detector pixel includes contributions from the
laser footprint and from noise (internal to the camera as well as
background thermal noise). Consequently, the accuracy of this
calculation is determined by the signal to noise ratio in the
detection process which is predominantly affected by the intensity
of the laser footprint. FIG. 8b shows the case where the signal to
noise ratio is low and consequently the centroid calculation is
biased by noise and is inaccurate. When calculating the centroid, a
threshold can be applied to reduce the effect of noise. However, in
this case, the application of a threshold is not sufficient to
completely eliminate the effect of noise because the intensity at
each detection pixel illuminated by the laser footprint has a
significant contribution from random noise as well as from the
laser footprint. FIG. 8c shows the case where the signal to noise
ratio is high and consequently the centroid calculation is not
biased by noise; application of a threshold can substantially
eliminate the effect of noise and results in more accurate
determination of the centroid of the laser footprint. FIG. 9a shows
the case where the size of the laser footprint is smaller than that
of each detector pixel and in most instances, the laser footprint
illuminates a single pixel. In this instance, the hit-detection
system calculates the laser footprint position to be that of the
single illuminated pixel and the accuracy of the calculation is
determined by the size of the detector pixel. As shown in FIGS. 9b
and 9c, the effect of noise is less significant because the
illuminated pixel can be uniquely determined after application of a
suitable threshold.
[0082] In a modern small arms simulator, the hit-detection is
performed by a standard charge-coupled device (CCD) camera; the CCD
cameras employed typically have a resolution of 760 pixels
(horizontal) by 580 pixels (vertical). For a system allowing a
quartet of firers, the screen dimension is such that the pixel (as
seen by the camera) is a square on the screen of approximately 4 mm
on each side. The size of the laser footprint in modern small arms
simulators is considerably larger than this, around 10 mm in
diameter. This corresponds to the case shown in FIG. 8a above and
consequently, the size of the pixels does not limit the accuracy of
the hit-detection calculation. The determining factor is now the
signal-to-noise ratio.
[0083] To overcome the problem of poor signal-to-noise ratios that
characterizes the prior art, the following solutions are proposed:
(1) a hit-detection camera that is positioned so as to capture the
area of the screen immediately surrounding the target (in order to
increase the amount of signal captured relative to the areas not
covered by the signal which simply add noise to the centroid
calculation), (2) hit-detection cameras that have noise floors
superior to those used in the prior art and (3) an eye-safe laser
that has a higher intensity and smaller footprint than those used
in the prior art. One embodiment of the current invention utilizes
all three of these solutions to achieve superior signal-to-noise
ratios and hence highly accurate weapon aim-point calculation.
[0084] In addition to adequate signal-to-noise ratio, it is
important that the weapon aim-point calculation is not adversely
affected by the large size of the detector pixel (both in absolute
terms and relative to the laser footprint). The size of each
detector pixel is determined by the dimension of the screen
captured by the CCD camera relative to the camera resolution.
Consequently, the pixel size can be reduced by increasing the
resolution of the camera or capturing a smaller area of the screen.
In one embodiment of the current invention, the hit-detection
camera only captures a small area of the screen in order to
maximize the signal-to-noise ratio. In this case, the pixel size is
small and the effect is negligible, regardless of the size of the
laser footprint. This is illustrated in FIG. 10 which shows the
preferred arrangement of the use of one hit detection sensor
(camera) directed to the target area (the finer grid area central
to the upper right illustration in FIG. 10). These aspects of the
invention are further illustrated in FIGS. 11a, 11b, 12a and 12b.
FIG. 11a shows the case where the size of the laser footprint is
larger than that of each detector pixel; FIG. 11b shows the
calculation of the position of the laser footprint. FIG. 12a shows
the case where the size of the laser footprint is larger than that
of each detector pixel; FIG. 12b shows the calculation of the
position of the laser footprint.
[0085] It should be apparent from the preceding discussion to one
skilled in the art that there is no simple equation which
determines the accuracy of a particular embodiment of the
hit-detection system as illustrated in FIG. 10. The accuracy is
determined by the detector pixel size, the size and intensity of
the laser footprint and the signal-to-noise characteristics of the
detector. There is a range of values for these parameters that
satisfies the weapon aim-point accuracy requirement which was
described earlier in the specification and simulation and
experimentation are required to precisely determine the accuracy of
a given embodiment of the invention. However, appropriate choice
for these parameters allows the design of an embodiment of the
invention that has a pre-determined accuracy that satisfies the
weapon aim-point accuracy requirement which was described earlier
in the specification.
[0086] In one embodiment the camera (Photron PCI 512 Fastcam, Blink
Technology Australia, Pty Limited) with a resolution of
512.times.512 pixels is placed approximately 2 m from the screen
and captures an area approximately 0.25.times.0.25 m. This results
in a pixel size of approximately 0.5 mm.
[0087] With regards to the firing weapon the radiation emitted is
preferably non-visible, and can be infra-red or preferably laser,
since the smaller laser footprint provides for increased accuracy,
in this embodiment the laser is an eye-safe infra-red laser
(LDM-5-850-0.78, from Laserex Technologies). In one form, the laser
is attached to a suitable weapon and is fired at the screen from a
distance of 10 m.
[0088] An infrared light filter (Andover 830FG07-165S, Lastek Pty
Ltd) is attached to the camera such that only radiation from the
laser footprint is detected by the camera.
[0089] The laser footprint provided by the laser (LDM-5-850-0.78)
is approximately 4 mm in diameter. Through the use of simulation
methods, it may be shown that the relative sizes of pixel (0.5 mm)
and laser footprint (4 mm) the maximum error in the calculation of
the laser footprint position is approximately 0.1 mm. This is
similar to the case shown in FIG. 8a but the pixel is considerably
smaller than that of the prior art. By geometry, if the screen is
10 m from the firer, and the simulated target is at 100 m, the
corresponding error is 1 mm, which exceeds the weapon aim-point
accuracy requirement which was described earlier in the
specification.
[0090] The combination of laser (LDM-5-850-0.78), camera (Photron
PCI 512 Fastcam) and filter (Andover 830FG07-165S) results in
signal-to-noise ratios of around 60 dB which is of such magnitude
that random noise will have minimal impact on the accuracy of the
calculation of the laser footprint location. Experimentation with
this embodiment of the invention has shown that when the laser is
fired from 4.5 m (want 10 m), the hit-detection system calculates
the location of the laser footprint to an accuracy equivalent to a
radial standard deviation of 0.01 milliradians.
[0091] Control of the shape of the laser output from the
marksmanship training weapon could include the addition of a
focusing lens arrangement on the laser 3 to focus the near parallel
rays of the laser 3 to as small a spot on the screen as possible.
In cases where the size of the laser footprint requires reduction
this could be achieved by use of an aperture of suitable size in
the barrel 3 to restrict the width of the laser beam and so produce
a controlled spot size on the screen 6.
[0092] Referring once again to the embodiment of the invention
presented in FIG. 1, data from the laser footprint detector 18 is
made available to the computer 11 for processing. A variety of
calculations can be performed by the processor, including
displaying either on a separate monitor or on the screen 6 as
required the strikes achieved by the marksman, group calculations
and many other details relating to individual strikes, timing of
strikes, comparison with prior results achieved by the particular
marksman or other marksmen. The data can be stored for later
retrieval as required.
[0093] In one embodiment the hit detection process includes the
following steps as illustrated in FIG. 13, which where required, is
processed in an appropriately programmed general purpose computer,
having a processor chip, memory and various input and output
mechanisms for receiving, storing and sending data related to the
marksmanship simulator arrangement and marksmanship detector
arrangement. Processes 2 to 13 illustrate the case where there is a
single hit-detection camera as in the embodiment of the invention
described by FIG. 1. If there is a requirement for a second
hit-detection camera (if for example, there is a requirement to
capture an image of the entire screen) then the additional
processes 15 to 23 are shown in order to illustrate how the
processing can be replicated and integrated with that of steps 2 to
13.
[0094] The processor can provide records (immediately and after a
series of shots) of the laser strikes in tabular and graphical form
(digital for viewing and hard copy), the presentation of which is
arranged to be suited to the training and qualification of marksmen
using the simulator arrangement.
[0095] Step 0 occurs prior to the simulator being run in real time
and in this step the entire system is calibrated in order to (1)
determine the appropriate scaling factor which scales distances
from a reference coordinate system (such as the screen) to the
desired coordinate system (such as the firing range being
simulated) (2) correct for keystoning and rotation errors resulting
from the field of view of the camera being offset and rotated
relative to the laser footprint.
[0096] Radiation (including the laser footprint as well as the
background and target images) is reflected from the screen (1), and
strikes infrared light filter (2). Infrared filter (2) blocks out
the visible portion of the radiation and passes only the infrared
component of that radiation, which should now be only that from the
laser (3). The detector camera (4) now converts the radiation into
a pixel image which is an array of values of infrared light
intensity (5). An intensity threshold (6) is applied to this array
of values and sets all values below the threshold to zero,
resulting in an array corresponding to the laser footprint against
a black background (7). The processor now computes the centroid (8)
of the laser footprint by taking the intensity weighted average of
the (x,y) coordinates of each pixel in array. One method to compute
the inset aim-point (9) would be to apply an equation of the
form:
X i = j = 1 Mi k = 1 Ni x k I jk / ( j = 1 Ni k = 1 Mi I jk )
##EQU00004## Y i = j = 1 Ni k = 1 Mi y j I jk / ( j = 1 Ni k = 1 Mi
I jk ) ##EQU00004.2##
[0097] The processor then scales (11) the centroid coordinates into
the scale of the screen coordinate system (12) and then displaces
this value (13) according to the offset giving the centroid
location relative to a reference coordinate on the screen (14). The
coordinates (14) now becomes an input into ballistic and
fall-of-shot computations.
[0098] FIG. 13 also shows optional processes 15-23 which illustrate
how the processing can be replicated and integrated with that of
steps 2 to 13 where it is desirable to detect the footprint outside
of the target area in order to give a low-resolution indication of
the extent to which a shot missed the target area.
[0099] FIG. 14 depicts the intensity level of the pixel array in
one of the axes before applying a threshold.
[0100] FIG. 15 depicts the same pixel intensities as shown in FIG.
14 after the application of the threshold where values below the
intensity threshold are set to zero.
[0101] FIG. 16 depicts the geometry of the scaling and corrections
applied to the centroid in the detector coordinate system in order
to convert them to screen coordinates.
[0102] FIG. 17 depicts the output provided by the processor as
feedback to marksman and instructors. Performance data is displayed
as the calculated fall-of-shot after ballistics calculations have
been applied to the location of the laser footprint. As an example,
FIG. 17 displays the fall-of-shot and extreme spread value for a
marksman shooting 5 rounds at a target.
* * * * *