Note: Descriptions are shown in the official language in which they were submitted.
WO 2010/111277 PCT/US2010/028331
LIGHT BASED PROJECTILE DETECTION SYSTEM
FOR A VIRTUAL FIREARMS TRAINING SIMULATOR
CROSS REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims priority from co-pending U.S. Provisional
Application Serial No. 61/162,498, filed on March 23, 2009, said application
being
relied upon and incorporated herein by reference.
FIELD OF INVENTION
[0002] The present invention relates to a system and method for determining
the
actual coordinates of a projectile impact in a screen and associating the
point of
impact with a firearms training simulation.
BACKGROUND OF THE INVENTION
[0003] A typical virtual firearms training simulator uses simulated weapons
that
do not fire real bullets to train students on the proper handling of a weapon
during
a simulated real life scenario. The training scenario includes a video,
digital
animation, or other virtual scenario of one or more situations requiring the
user to
react quickly and decisively, such as a hostage scenario, terrorist attack, or
general
malfeasance. This scenario is projected onto a screen using a video projector,
with
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the scenario being controlled by a simulation computer that also detects the
point
of aim at the instance the student pulls the trigger of the simulated weapon.
The
simulated weapon is equipped with either an invisible or visible laser that
"fires" a
laser pulse when the trigger is pulled. A camera, in electrical communication
with
the simulation computer, detects this pulse of light, and transmits the impact
coordinates to the simulation computer. The simulation computer then
determines
the location of the hit relative to the scenario being broadcast by matching
the
coordinate system of the camera to the coordinate system of the projected
image or
target.
[00041 A drawback to this system is that the simulated weapon operated by the
user often simply generates a laser pulse to imitate the firing of the weapon,
which
does not produce a realistic experience for the user. That is, the simulated
weapon
typically does not have the feel of an actual firearm, and often does not
produce
recoil action, or produces unrealistic recoil action for the user, such that
the
simulation lacks credibility for the user. Consequently, trainees that are not
used to
extensive target practice with live firearms may be disadvantaged when
required to
handle firearms in combat situations.
[00051 A variant of this virtual firearms training simulator is one that
detects real
bullets fired from an actual live weapon. Since a bullet is not a pulse of
light, the
camera detection method described above may not seem practical to use. Rather,
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several alternative detection methods have been developed as an add-on to an
existing simulator's laser detection system. They include detection of the
visual
image of the bullet as it passes an array of sensors, detection of the heat
signature
of the bullet as it penetrates the screen, detection of the acoustical waves
generated
by the bullet as it passes an array of acoustic sensors, or detection of the
hole that
the bullet makes when penetrating a screen material such as paper. While all
of
these methods may work to some degree, none of them are performed within
desired parameters, such as at a low financial cost and having a high degree
of
accuracy.
BRIEF SUMMARY OF THE INVENTION
[00061 A light based projectile detection system for a firearm and a virtual
firearms training simulator is described herein. The light based projectile
detection
system includes a self-sealing screen having a proximal side and a distal
side. A
scenario projector transmits a simulation onto the proximal side, and a light
source
(such as a flash) faces the distal side. The light source selectively projects
light
onto the distal side of the screen when the firearm is shot, such that light
from the
source traverses the screen after contact by a projectile. A camera monitors
the
light traversing the aperture created by the projectile to determine and
associate the
position of impact and transmit that information to a scenario computer.
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[0007] The system may include an audio detection circuit to monitor the sound
generated by the firearm and transmit a signal to a flash controller to cause
the
light source to illuminate. The screen will then re-seal around the hole so
that the
light no longer traverses the screen.
[0008] The system may additionally include a housing to support the screen,
with the light source surrounded by the housing and screen to control the
distribution of light from said light source. In such an embodiment, a
reflective
panel (such as paper with foil on one side) may be mounted in said housing
diagonally, with the light source positioned between the reflective panel and
the
screen. This arrangement will project light directly onto the distal side of
the
screen as well as onto the reflector panel, which will assist in evenly
projecting
light on the distal side of the screen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Figure 1 is a block diagram of the light based projectile detection
system
for a virtual firearms training simulator;
[0010] Figure 2 is a second block diagram of the light based projectile
detection
system for a virtual firearms training simulator of Figure 1, the diagram
showing
the impact of a projectile with a screen; and
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[00111 Figure 3 is a perspective view of the screen and light assembly
incorporated into the system illustrated in Figures 1 and 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[00121 Referring to Figures 1-3, a light based projectile detection system 10
is
illustrated. The light based projectile detection system 10 is able to monitor
the
impact of a projectile 18 fired by an actual firearm 16 on a self-sealing
screen 14
using a laser detection system 12 similar to those described above and as used
in a
typical laser-based virtual firearms training simulator known in the art.
[00131 More specifically, the laser detection system 12 includes a scenario
projector 20 and a camera 22 that are both in electrical communication with a
simulation or hit detect computer 24. The projector 20 may include any type of
image-generating device, and receives a simulation scenario from the hit
detect
computer 24. The projector 20 will then broadcast that scenario on one or more
self-sealing screens 14. In contrast, the camera 22 monitors the self-healing
screen
14 for a light or laser pulse, which will correspond to the point of impact of
the
projectile 18 fired in during the simulation projected on the screen 14. That
is, the
laser detection system 12 will monitor the actual live fire of the weapon 16
to
determine the impact position of a fired projectile 18, such as a bullet or
slug,
through the screen 14 during simulation scenarios projected on the screen 14.
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Once the light pulse is detected, the camera 22 will transmit the coordinates
of the
impact to the hit detect computer 24. The computer 24 includes software that
will
be able to compute the impact coordinate relative to predetermined screen
coordinates relative to the projected target.
[0014] To leverage the laser detection system 12 to determine the bullet
position
of impact on the screen 14, the bullet 18 must generate a pulse of light at
the
specific location Ll where the bullet 18 impacts the screen 14 after being
fired by
the weapon 16. To generate this pulse of light, the projection screen 14 of
the
bullet detection system 10 is made of a self-healing elastomeric material,
such as a
natural gum rubber or other similar substance known in the art. The screen 14
has
a proximal side 14p and an opposite distal side 14d. The proximal side 14p
faces
and is closest to the laser detection system 12, while the distal side 14d
opposite
the proximal side 14p faces and is closest to a light source 26. The light
source 26
outputs wavelengths of light 28 that can be detected by the same camera 22.
[0015] When a projectile 18 penetrates the surface of the screen 14 at
location
L1 (see Figure 1), it will create a hole Hl at the location L1 that creates a
light
valve to allow light 28 to travel through the screen 14 (see Figure 2). After
a
period of time, the self-healing material of the screen 14 will re-seal the
hole Hl so
that the camera 22 will no longer monitor any light 28 through the screen 14.
As a
result, the brief exposure of light 28 through the light valve Hl in the
screen 14
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will simulate a light pulse. Because the temporary hole H1 is the position L1
of
the bullet 18 at impact, the accuracy for monitoring the light through the
light
valve Hl by the camera 22 is the same as the laser pulse detection (as
described
above). Any calibration algorithm used by the hit detect computer 24 to match
the
coordinate system of the camera 22 to the coordinate system of the projected
simulation of the hit detect computer 24 as projected by projector 20 may be
used
in the present system; that is, the calibration algorithm used by the
simulation hit
detect computer 24 to match the coordinate system of the camera 22 to the
coordinate system of the projected simulation of the hit detect computer 24
will
remain the same whether one uses a laser pulse in prior simulation systems or
shoots a real bullet 18 in the training scenario of the present system.
[00161 A prototype of the design integrated with typical virtual small arms
training simulator is illustrated in Figure 1. This prototype was tested for
accuracy
in matching the contact of the bullet 18 with the scenario, and the results
were
accurate within 1 to 3 mm, which is very similar to the laser-based system. It
was
determined the best way to get the most amount of light 28 for the camera 22
to
detect the bullet 18 passing through the screen was to use a xenon flash 26
facing
the distal side 14d of the screen 14 that is selectively illuminated instead
of a
continuous light source. A xenon flash was selected for its desirable
properties in
light intensity while generating relatively lower heat. As a result, a flash
triggering
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system 30 is connected to the light source 26 to ensure proper timing of the
light
28 with the firing event of the weapon 16.
[0017] The flash triggering system 30 includes an audio detection circuit 32
in
electrical communication with a flash/trigger controller 34. The audio
detection
circuit 32 may be any known in the art, such as a circuit including a
microphone
for converting audio energy (sound waves) into an electrical signal.
Similarly, the
flash/trigger controller 34 may be a conventional microcontroller that is in
electrical communication with the audio detection circuit 32 and the light
source
26. The audio detection circuit 32 is positioned somewhat near the weapon 16,
and
detects the sound associated when the weapon 16 is initially shot. The audio
detection circuit 32 thereby transmits a signal to the flash controller 34
corresponding to the timing of the weapon 16 being fired.
[0018] The flash controller 34, which is in electrical communication with the
light source 26, will use the signal transmitted from the audio detection
circuit 32
to further send a signal triggering a bank of facing the distal side 14d of
the screen
14. The xenon flash bulbs 26 will therefore be illuminated at the approximate
time
when the bullet 18 penetrates through the self-healing rubber front surface
14p.
This is accomplished by having the controller 34 turn the flash bulbs 26 on
after a
pre-determined time delay to ensure the camera 22 will detect or view the
light 28
while there is a bullet hole H1 in the screen 14. This time delay will vary
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depending on the speed of the bullet 18 used and the distance that the firearm
16 is
from the screen 14.
[00191 Looking to Figure 3, the screen 14 may be mounted in a housing or frame
36 (one side of the housing 36 is removed to view the screen 14). The housing
36
and screen 14 define a casing that surrounds the light source 26, such that
the
housing 36 and screen 14 will contain all light produced by light source 26
until
the screen 14 is pierced by a bullet 18. Although the present rectangular
housing
36 is illustrated, other frames may be implemented for the housing 36 as
desired by
the user. Furthermore, a reflector panel 38 may be diagonally mounted within
the
housing 36 above the light source 26, such that the light source 26 is
positioned
between the reflector panel 38 and the screen 14. The reflector panel 38 may
be
made of a sheet of paper with foil on a side nearest the light source 26 or
some
other similar material that has a high reflectivity to effectively reflect and
distribute
the light produced by the light source 26. The light source 26 will therefore
project
light directly onto the screen 14 as well as onto the reflector panel 38 to
project
light evenly on the distal side 14d of the screen 14.
[00201 As noted above, a prototype using xenon flash bulbs 26 was developed
and tested to work as expected with accuracy to be within 1 to 3 mm.
[00211 Without knowing the properties of the rubber screen 14 (such as the
stretch or hardness), an assumption is made that there is a finite amount of
time
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before the screen 14 will re-seal itself (return back to its original shape)
depending
on the distance and failure point of the stretch in the screen 14. A further
assumption of a worst case condition is that the re-seal time is zero (that
is, that the
screen 14 is a perfect material that reseals instantly). In other words, the
screen 14
is sealed as soon as the bullet or slug 18 passes through the screen 14. It is
also
assumed that the only time "light" 28 is allowed through the screen 14 is
while the
slug 18 is penetrating the screen 18 (i.e., the initial hole Hl that the slug
18 makes
is bigger than the slug 18 to allow this light 28 to come through as the slug
18 is
passing through.) To determine how much light 28 is directly related to the
speed
of the slug 18 and how long the "light valve" is left on (that is, how long
light
passes through the screen 14 before it reseals), the following equation should
be
used:
[00221 Light valve on time = [(length of slug + thickness of screen + distance
the screen stretch before initial penetration) / speed of slug] + [resealing
time once
the slug 18 passes], the following measurements are determined.
[00231 Assuming that the minimum distance of stretch in the screen 14 is half
of
the diameter of the slug 18 (but is most likely more) and is dependant of
speed of
the slug 18 and material property of the screen 14, 5 mm as the screen
thickness, 0
sec for the resealing time once the slug passes (this is somewhat dependant on
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far the material is stretched and the screen material property), the following
calculations are made:
[0024] A typical spec for a 9mm NATO ball is: Speed of slug range from 950
ft/s to 1300 ft/s with a slug length of 0.610" or 15.5mm.
[0025] A typical specification for a 5.56 mm, ball is: Speed of slug is 3250
ft/s
with the slug length of 19.3 mm to 23mm.
[0026] So minimum light valve on time for a 9 mm slug is (15.5 + 5 +
4.5)/(1300*304.8) = 63.1 sec, and the minimum light valve on time for a 5.56
mm is (19.3 + 5 + 2.28)/(3250*304.8) = 26.8 sec.
[0027] In a charged coupled device (CCD) in the camera 22 for capturing
images, there is a photoactive region (an epitaxial layer of silicon), and a
transmission region made out of a shift register. An image is projected by a
lens
on the capacitor array (the photoactive region), causing each capacitor to
accumulate an electric charge proportional to the light intensity at that
location.
The exposure time for the light valve HI is calculated at a minimum from 26.8
to
63.1 sec (based on the calculations for the above-noted assumptions).
Consequently, it is possible to detect the charge if the intensity is large
enough
using the CCD sensor as long as the noise level in the CCD sensor is not
larger
than the charge. Since this is really an absolute minimum in an ideally
perfect
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situation, the actual time the light valve Hl will be open will be greater, if
not
significantly greater.
[0028] In addition, there is a blanking time between the shifting of data out
of
the register where the CCD sensor cannot accumulate charges. This blanking
needs to be as small as possible. The current camera 22 has about a 2 msec
blank
time. This is more of a function determined by the camera manufacturer. For
example, the current camera 22 being evaluated for the system 10 has a blank
time
between frames of 35 gsec out of the box and can be adjusted even lower.
[0029] The calculations support the theory that the capabilities of CCD sensor
can allow it to detect a bullet slug 18 traveling through a re-sealable rubber
screen
14 with a back-lit light source 26.
[0030] The design above was initially tested using a rubber live fire screen
as a
proof of concept, some incandescent light bulbs, a standard 100 D-P (small
arms
virtual system) with the standard hit camera 22 and a filter (an infrared
filter used
to monitor the desired light) and a TV monitor. The back side or distal side
14d of
the screen 14 was lit using about two 100W light bulbs, with the rear rubber
screen
removed so that only the front rubber screen was separating the light 26 and
the
shooter. The hit camera 22 was pointed on the screen 14 as usual and the TV
monitor connected to "see" the output of the hit camera 22. The design was
tested
with both 9 mm and 5.56 mm rounds 18. In all cases, the users were able to
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visually see the light 28 come through the screen 14 momentarily before the
screen
14 would reseal after the slug 18 passed through.
[00311 The 5.56 slug 18 did leave a pinhole and did not completely reseal like
the 9 mm slug 18. A small piece of the screen 14 had been torn off from the
back
or distal side 14d when the 5.56 mm slug 18 was shot, which did not occur with
the 9 mm. A momentary faint blurry light appeared on the TV monitor indicating
where the slug 18 went through the screen 14, which showed that detection is
possible and, with the right combination of filters, camera, screen material,
and
lighting source, it is possible to design a system to detect the brief pulse
of light 28
caused by the penetration of the bullet slug 18.
[00321 A high speed camera 22 was also used to determine the approximate on
time of the material (how long the light valve Hl appears to be open) once a 9
mm
slug has penetrated the screen 18. The frame rate of the camera 22 was
approximately 8000 frames per sec. The hole Hl appeared to be open for at
least 4
frames or 4/8000 or 0.5 msec which is more 9 times longer than calculated for
the
worst case scenario. These test results further demonstrated that the proposed
device will operate as desired.
[00331 Having thus described exemplary embodiments of a LIGHT BASED
PROJECTILE DETECTION SYSTEM FOR A VIRTUAL FIREARMS
TRAINING SIMULATOR, it should be noted by those skilled in the art that the
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within disclosures are exemplary only and that various other alternatives,
adaptations, and modifications may be made within the scope of this
disclosure.
Accordingly, the invention is not limited to the specific embodiments as
illustrated
herein, but is only limited by the following claims.
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