U.S. patent application number 11/858924 was filed with the patent office on 2012-07-19 for hit detection in direct-fire or small-arms simulators.
Invention is credited to George Galanis, Ashley Stephens, Armando Vozzo.
Application Number | 20120183931 11/858924 |
Document ID | / |
Family ID | 46491052 |
Filed Date | 2012-07-19 |
United States Patent
Application |
20120183931 |
Kind Code |
A1 |
Galanis; George ; et
al. |
July 19, 2012 |
HIT DETECTION IN DIRECT-FIRE OR SMALL-ARMS SIMULATORS
Abstract
A hit detection system including: a simulated weapon, a laser
attached to the simulated weapon, a full screen projector
projecting an image on a screen, a screen for target depiction and
making a laser footprint visible to a hit-detection camera, at
least a first hit detection camera being a high precision camera
that is capable of detecting a laser footprint and generating hit
detection data, a simulation computer in operative connection with
the full screen projector and the hit detection camera, a link
between a trigger on the simulated weapon and the first hit
detection camera, a data storage means for storing hit detection
data generated by the first hit detection camera, so that, in use,
when a trigger on the simulated weapon is pulled to activate the
laser a laser footprint is projected onto the screen and at the
same time the hit detection camera takes an image of the laser
footprint on the screen.
Inventors: |
Galanis; George; (Edinburgh,
AU) ; Vozzo; Armando; (Edinburgh, AU) ;
Stephens; Ashley; (Edinburgh, AU) |
Family ID: |
46491052 |
Appl. No.: |
11/858924 |
Filed: |
September 21, 2007 |
Current U.S.
Class: |
434/22 |
Current CPC
Class: |
F41G 3/2694 20130101;
F41G 3/2655 20130101; F41J 5/10 20130101; F41G 3/2627 20130101 |
Class at
Publication: |
434/22 |
International
Class: |
F41G 3/26 20060101
F41G003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2006 |
AU |
AU2006905264 |
Claims
1. A hit detection system for hit detection in direct-fire or
small-arms simulators comprising: a simulated weapon; a laser
attached to said simulated weapon; a full screen projector
projecting an image on a screen; a screen for target depiction and
configured to make a laser footprint visible to a hit-detection
camera; at least one first hit detection camera comprising a high
precision camera that is capable of detecting a laser footprint and
generating hit detection data; a simulation computer in operative
connection with said full screen projector and said at least one
first hit detection camera; a link between a trigger on said
simulated weapon and said at least one first hit detection camera;
a data storage object configured to store hit detection data
generated by said at least one first hit detection camera; wherein
when a trigger on said simulated weapon is pulled to activate said
laser, a laser footprint is projected onto said screen and at a
same time, said at least one first hit detection camera takes an
image of said laser footprint on said screen.
2. The hit detection system of claim 1, wherein said laser selected
from the group consisting of continuous wave lasers and pulsed wave
lasers.
3. The hit detection system of claim 2, wherein when said laser is
a pulsed laser illumination of said laser attached to said
simulated weapon is as a result of said trigger being operatively
connected to a switch and a circuit capable of generating a pulse
that is subsequently fed to a circuit to generate a voltage
configured to illuminate said laser so that activation of said
trigger illuminates said laser.
4. The hit detection system of claim 2, further comprising a video
camera for continuous laser tracking
5. The hit detection system of claim 4, wherein said at least one
first hit detection camera is focused on only a target depicted on
said screen.
6. The hit detection system of claim 5, further comprising a target
projector configured to project a target image onto said projector
screen.
7. The hit detection system of claim 4, further comprising a second
hit detection camera synchronized to take an image of said screen
when said trigger on said simulated weapon is pulled.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an improvement to
marksmanship training devices for assisting in firearms
training.
[0003] In particular, the invention relates to improving the timing
accuracy of the hit detection process used in the marksmanship
training devices.
[0004] 2. Description of the Related Art
[0005] Since human aiming involves continuous movement, improving
the timing accuracy of the detection process is essential to the
provision of feedback for aiming (and hence marksmanship)
training
[0006] The last couple of decades have seen enormous strides in the
development of video projectors and cameras. Cameras in particular
have reduced in both size and cost, to the point where cameras have
completely solid-state image sensors and hence very compact
electronics.
[0007] Conventional video cameras have a number of limitations for
use in hit-detection systems for simulation and in particular, for
the function of hit-detection in small-arms simulators.
[0008] A typical indoor small-arms simulation system is shown in
FIG. 1.
[0009] Components of such systems include: (1) a simulated rifle,
hand gun, artillery or other weapon that normally ejects a
projectile; (2) a sighting system that may be telescopic, but could
be simpler (such as a sight on the end of a rifle) or more
sophisticated (such as a head up display for tracking multiple
targets); (3) a laser attached or embedded in some part of the
simulated weapon, either generating a continuous beam for
continuous tracking, or controlled by a trigger; (4) a projector
that generates a computer controlled image on the screen; (5) a
camera that views the whole screen; (6) the screen upon which
images are projected and from which laser strikes are detected by
the camera (5); (7) a target that can be projected anywhere on the
screen, this may be a bulls-eye or other type of target used for
marksmanship training, or could be a moving target; (8) the bright
signature area generated by the laser; (9) the area of the screen
viewed through the simulated weapon sight; and (10) the computer
(or computers) controlling the weapons and effects simulation.
[0010] Referring to FIG. 1, when the trigger on the simulated
weapon (1) is pulled the computer can use the location of the
detected aim-point on the screen as part of the computation of the
flight of a simulated projectile.
[0011] The advantage of these types of simulators is that they use
no ammunition, are not dependent on weather conditions and can be
used at any time of the day or night. Therefore, these devices are
quite attractive propositions for low-cost training, or even
training in places where access to live-ranges is not practical or
possible, such as on board submarines.
[0012] One problem with such `indoor` simulation systems is the
difficulty in detecting the location of the centre of the laser
spot to an accuracy that correlates to the real world. Since it is
common for marksmen to aim at targets that are hundreds or even
thousands of metres away, and typical indoor simulators are only
tens of metres long then the tolerance within which the laser
strike must be detected in a simulator is much tighter than that
encountered in the real world.
[0013] For example a marksman who is aiming to get a shot within
100 mm of a point on a target at a range of 100 metres requires the
simulator hit detection system to resolve between laser positions
less than 10 mm apart on the simulator screen if the screen is 10
metres from the firing point (derived by using similar
triangles).
[0014] In addition to the spatial tolerance requirement is the
temporal accuracy requirement. No marksman can hold a gun or rifle
completely stationary. Human muscles have tremors and humans must
continue to breathe. Hence the marksman must pull the trigger
smoothly so as not to jolt the rifle out of position. In addition
the timing of the trigger movement must be such that the rifle,
breathing and trigger pull all coincide at the point in time when
the rifle is aimed at the desired point.
[0015] Humans can be very precise regarding timing of actions, with
skilled humans able to time muscle movements to an accuracy of a
few milliseconds. Thus, the hit detection system must be able to
detect the laser footprint at a precise time and this is just as
critical as the fine tolerances required for spatial location. That
is, the aim point must be located accurately at the precise moment
of the pull of the trigger so as to provide useful feedback for the
human to develop marksmanship skills.
[0016] Current marksmanship simulators have three possible
deficiencies, each of which contribute to an overall problem for
hit detection: low-cost solid-state lasers produce low-frequency
pulses of light; conventional video cameras refresh the detected
scene at slow rates; and the simulation computers, laser pulses and
video cameras all update asynchronously.
[0017] Conventional Video Cameras
[0018] To keep simulator costs down and reduce the requirement for
specially manufactured video computer cards, the current generation
of small-arms simulators use commonly available video cameras.
These cameras typically refresh the whole image at 30 Hz. The video
signal generated by such cameras may be either non-interlaced at 30
Hz, or interlaced where odd and even frames are refreshed
alternately at 30 Hz. That is, the even lines of the image are
typically refreshed in 1/60.sup.th of a second then the odd lines
of the image are refreshed in the next 1/60.sup.th of a second.
Interlaced video cameras require two scans to completely refresh
the image so a complete image is built up over 1/30.sup.th of a
second.
[0019] Pulsed Lasers
[0020] Most low-cost solid-state lasers that have a high degree of
brightness (visible or infra-red) are typically operated in a
pulsed mode--the light beam alternates between on and off. For a
given brightness level, pulsing the laser reduces the overall power
consumption and heat dissipation requirements, as well as reducing
the energy in the light, making the laser safer to use without
eye-protection. Typical pulse rates may be in the order of 10 Hz to
20 Hz.
[0021] Asynchronous Components
[0022] Marksmanship simulators built from commercial-off-the-shelf
components typically run those components in an asynchronous
manner. This reduces development costs and complexity of the
overall simulation system. It is possible that a simulator may
comprise a mix of synchronous and asynchronous components, where
for example there may be some synchronization between a laser pulse
and trigger pull but no synchronization between other
components.
[0023] Given that humans can control muscle movements to a
precision of several milliseconds, the problem with asynchronous
systems occurs when the processes run at frequencies where the
total time delays are random with variations significantly greater
than several milliseconds. Hit detection systems in simulators
operate in the infra-red spectrum so as to be invisible to the
human eye. Therefore the human cannot compensate for any random
delay occurring from the hit-detection system.
[0024] To illustrate this effect consider the example in FIG. 2.
The figure shows time plotted on the horizontal axis along the
bottom, and an example of the processes at work in a laser-based
hit-detection system above the line. The top line shows the
trigger, the middle line shows the state of the laser pulse and the
bottom row shows the state of the hit detection camera.
[0025] Referring to FIG. 2, the detection camera happens to switch
to light detection mode just before the laser asynchronously pulses
on, and the trigger happens to be pulled while the laser is on. In
this case the detection latency is relatively small purely by
chance.
[0026] Similarly, referring to FIG. 3, the detection camera happens
to switch on and the laser asynchronously happens to pulse on.
However, in this case, the laser pulses off, and the trigger is
pulled just after the laser pulses on. In this case a detection
will not occur until the laser pulses on. Alternatively a detection
could be retrospectively be determined by using the last previous
pulse. Either way, there is a potentially significant random error
in determining where the laser was actually pointed at the time the
of the trigger pull.
BRIEF SUMMARY OF THE INVENTION
[0027] It is an object of the invention to increase the timing
accuracy of hit detection systems used in marksmanship training
devices.
[0028] It is a further object of the current invention to provide a
hit detection system for a marksmanship training device that
ensures the laser footprint is located as close as possible in time
to the actual moment of the trigger pull.
[0029] It is yet a further object of the invention to provide a hit
detection process that is synchronous.
[0030] It is an object of the present invention to overcome, or at
least substantially ameliorate, the disadvantages and shortcomings
of the prior art.
[0031] Other objects and advantages of the present invention will
become apparent from the following description, taking in
connection with the accompanying drawings, wherein, by way of
illustration and example, an embodiment of the present invention is
disclosed.
[0032] According to the present invention, although this should not
be seen as limiting the invention in any way, there is provided a
marksmanship simulator including a weapon capable of firing a
laser, a screen for projecting images thereon and for receiving a
laser strike from the weapon, a first hit detection system for
registering a laser strike on the screen, a first projector for
projecting a background image and a target image on the screen.
[0033] In preference, there is provided a hit detection system in
which the frequencies of all the asynchronous processes are
increased so that the delay is below the performance threshold for
humans.
[0034] In a further form of the invention, there is provided a
method of improving the timing of a hit detection system, the
method including the steps of increasing the frequencies of the all
the asynchronous processes so that the variability of the delay is
below the performance threshold for humans.
[0035] In preference, the frequencies will be greater than
approximately 400 Hz.
[0036] In preference, these frequencies will be greater than
approximately 1000 Hz
[0037] In a further form of the invention, there is provided a hit
detection system for a marksmanship training device in which the
regular laser pulsing system is disabled and a single short period
laser pulse is generated upon pulling the trigger of a simulated
weapon.
[0038] In a further form of the invention there is provided a hit
detection system for a marksmanship training device, including a
weapon capable of firing a laser, a screen for projecting images
thereon and for receiving a laser strike from the weapon, a first
hit detection system for registering a laser strike on the screen,
a first projector for projecting a background image and a target
image on the screen, in which a trigger on a simulated weapon is
restricted to be activated at a rate less than or equal to a frame
rate of a camera used to detect a hit.
[0039] In a further form of the invention there is provided a hit
detection system, which includes a continuous wave laser, rather
than a pulsed laser.
[0040] In preference, the system further includes a high-speed
camera to detect the laser spot provided by a simulated weapon.
[0041] In a further form of the invention there is provided a hit
detection system, which includes a pulsed laser to take advantage
of the brighter reference point.
[0042] In preference, the system further includes a circuit that
generates a steady stream of low frequency pulses for continuous
tracking.
[0043] In preference, the system includes a second camera the
second camera synchronized to take a high-speed image of the screen
when the trigger is pulled.
[0044] In preference, a shutter speed of the second camera is long
enough to capture the short duration phase of the laser pulse.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] By way of example, an employment of the invention is
described more fully hereinafter with reference to the accompanying
drawings, in which:
[0046] FIG. 1 is a schematic diagram of a prior art system;
[0047] FIG. 2 is a diagram showing the processes at work in a laser
based hit detection system;
[0048] FIG. 3 displays the situation when the processes are out of
synchrony;
[0049] FIG. 4 is a schematic diagram of an embodiment of the
current invention of continuous tracking with pulsed laser
system;
[0050] FIG. 5 is a schematic diagram of an embodiment of the
current invention referred to as trigger-laser synchronization.
DETAILED DESCRIPTION OF THE INVENTION
[0051] The present invention allows for the following to improve
the problems associated with hit detection in marksmanship training
devices, including increasing the frequencies of all the
asynchronous processes so that the variability of the delay is
below the performance thresholds for the human; or making the hit
detection process synchronous.
[0052] Increase Detection Frequency
[0053] In this embodiment of the invention the simulation processes
are still asynchronous, but the cycle times in all processes must
be shortened so that the total random delay time is so small as to
be negligible, compared to the human thresholds. Since expert human
performance requires muscle coordination within a few milliseconds
of precision, it is recommended that frequencies will need to be of
the order of 400 Hz, and possibly greater than 1 kHz would be
preferred. So if a pulsed laser is used, the pulsing must have a
period of no more than a few milliseconds.
[0054] Alternatively the mark-space ratio of the laser pulses (the
ratio of "on" to "off" time) must be such that the off time is no
more than a few milliseconds in each cycle and the camera must have
a shutter speed of no more than a few milliseconds, and the
frequency of recording the scene must be of the order of 400 Hz or
greater. The trigger pull time must also be polled at a similar
rate (i.e. 400 Hz or greater), and the simulation computer must be
able to detect a trigger pull and generate a recoil to the accuracy
of several milliseconds. The end effect is that the cumulative
random variation in delay, because of the asynchronous connection
of processes, should be no greater than 5 to 10 milliseconds. This
embodiment requires a video camera that operates at a very high
rate. Such cameras can be expensive, and the simulation computer
will have to cope with much larger amounts of data.
[0055] Synchronization
[0056] An alternative embodiment of the invention is to synchronize
key parts of the simulation process.
[0057] Simple Laser-Trigger Synchronization
[0058] Synchronization can be achieved by disabling any regular
laser pulsing and generate a single, very short period, laser pulse
whenever the trigger is pulled. As long as the trigger is not
allowed to be pulled successively at a rate greater than the frame
rate of the camera then each video frame in the camera can contain
no more than a single laser footprint, and then it is guaranteed
that the laser footprint coincides with the aim-point of the rifle
at the moment of the trigger pull.
[0059] Continuous Tracking with a Continuous Laser
[0060] The previous proposed implementation is relatively simple in
terms of locating the aim-point. It can use conventional readily
available commercial video cameras. However, it does not allow for
continuous tracking of the aim point since only a single high
precision laser pulse is generated which a relatively slow video
camera can capture. A refinement allowing for continuous tracking
is to use a continuous wave laser instead of a pulsed laser. A
conventional video camera can be used for the purposes of tracking
the laser to provide a low-precision plot of the laser footprint.
This is similar to the current systems except that a continuous
laser is required. But this alone does not enable high precision
hit detection in time nor will it enable high precision spatial
detection.
[0061] To solve these problems created by use of a continuous laser
a high speed camera is also required. A high-speed camera is added
to this system to detect the laser spot accurately relative to the
point in time of the trigger pull. Referring to FIG. 4, (1) is the
simulated weapon; (2) is used for sighting the target; (3) is the
continuous laser attached to the simulated weapon; (4) is the full
screen projector and (5) is the conventional video camera for
continuous laser tracking; (6) is the screen used for the target
depiction and making the laser footprint visible to the
hit-detection cameras; (7) is the representation of the target on
the screen; (8) is the laser footprint on the screen; (9) is the
region detected by the high-precision camera (11); and (13) is a
direct link between the trigger and camera (11) that bypasses the
simulation computer (10). The reason for bypassing the simulation
computer is so as to eliminate any delays inherent in the computer
system. Although it is possible to have the simulation computer
running at a high rate, bypassing the computer avoids the need for
such high computational speeds, enabling the computer to be run in
a conventional manner at lower iteration rates.
[0062] In the system as described in FIG. 4, the key element is the
high speed link (13), which on trigger pull signals the high-speed
camera to take an image of the simulation screen (6), and in
particular a high resolution image of the target area (7) at the
instant the trigger is pulled. This image can then be downloaded to
the simulation computer at a later time for processing, analysis
and feedback to the marksman or instructor. This process is then
quite independent of the less accurate continuous laser detection
processing that is going on in parallel which is mediated by the
simulation computer (10). With this design, both the continuous
tracking and high-speed hit detection processes can occur
concurrently.
[0063] Continuous Tracking with Pulsed Laser
[0064] A refinement is to use a pulsed laser rather than a
continuous laser. Pulsed lasers have the advantage that they can
provide a brighter reference point than a continuous wave laser for
the same power input. This will result in the laser footprint being
both easier to detect and less hazardous to human eye-sight.
[0065] In this implementation, a circuit must generate a steady
stream of low frequency pulses for continuous tracking The circuit
must then provide for an additional pulse at the moment the trigger
is pulled. To avoid problems associated with two laser pulses in a
single video frame that would occur with a conventional video
camera, a second camera is employed that is synchronized to take a
single high-speed image of the screen when the trigger is
pulled.
[0066] This is shown diagrammatically in FIGS. 4 and 5. FIG. 4
shows the same design elements as described in the previous
section. Referring to FIG. 5, the regular stream of pulses for
driving the laser is generated by a clock (1). The trigger contains
a switch (2) and a circuit that generates a high-speed pulse when
the trigger is pressed. The clock pulse and trigger pulse are
combined by an `OR` gate (so that either the trigger or the clock
can produce a signal) and fed to a circuit (4) that generates a
voltage (5) for illuminating the laser. The trigger signal (6) can
also be sent as a trigger for a high speed camera (11) in FIG.
5.
[0067] In this design the camera shutter must be timed accurately
to be open for a short period so as to ensure that the camera
captures only the short-duration pulse of the laser, which is
synchronized with the trigger pull.
[0068] 1. Slow Camera Considerations
[0069] A commercially attractive possibility might be to use an
inexpensive commercial-off-the-shelf camera system for this
application. In the event that the camera or its associated
componentry is unable to perform adequately due to slow image
capture performance, this can be accommodated by having a two-stage
trigger detection mechansim. The first stage of the trigger
detection, either by first position switch or pressure sensor,
prompts the camera and associated componentry to setup its internal
configuration requirements for the image capture, while the second
trigger point (the point of firing the simulated rifle) prompts the
camera to capture the image.
[0070] 2. Direct Trigger Link Connection
[0071] Synchronization of image capture with trigger activation can
be achieved by a umber of methods, including, but not limited to:
a) direct connection of trigger activation mechanism to camera
input; b) direct connection of trigger activation mechanism to
camera input through signal conditioning components; c) direct
connection of trigger activation mechanism to camera input via the
simulation computer yet independent of the simulation processing
cycles; or d) direct connection of trigger activation mechanism to
camera input by way of prioritized interruption of simulation
processor cycles.
[0072] Various modifications may be made in details of design and
construction [and process steps, parameters of operation etc.,]
without departing from the scope and ambit of the invention.
* * * * *