U.S. patent application number 10/165606 was filed with the patent office on 2003-03-13 for methods and systems for laser diode ignition of field weaponry.
Invention is credited to Butterfield, Tom, Carvalho, Joseph E., Fahey, Wm. David, Folsom, Mark, Valenti, Robert M..
Application Number | 20030047101 10/165606 |
Document ID | / |
Family ID | 26861528 |
Filed Date | 2003-03-13 |
United States Patent
Application |
20030047101 |
Kind Code |
A1 |
Folsom, Mark ; et
al. |
March 13, 2003 |
Methods and systems for laser diode ignition of field weaponry
Abstract
Methods and systems for laser diode ignition of field cannons
and weaponry. A series of one or more laser diodes or laser diode
array, bars or stripes that are configured to optically pump a
collimator which may be formed of materials to provide a lasing
medium. The energy output of these devices can be combined when
configured as an array or a series of redundant laser diodes
assemblies to provide safe and reliable ignition systems. The
collimator may direct the output from these laser diode assemblies
as multiple collimated ignition beams. The laser diode assemblies
may optically end pump and/or side pump the collimator or
collimating rod to deliver a more directed energy output to
artillery propellant. Additionally, the duration of the pulses may
be controlled and extended as necessary to help ensure proper
ignition of the propellant.
Inventors: |
Folsom, Mark; (Monterey,
CA) ; Fahey, Wm. David; (Cupertino, CA) ;
Carvalho, Joseph E.; (Hollister, CA) ; Butterfield,
Tom; (Hollister, CA) ; Valenti, Robert M.;
(Menlo Park, CA) |
Correspondence
Address: |
WILSON SONSINI GOODRICH & ROSATI
650 PAGE MILL ROAD
PALO ALTO
CA
943041050
|
Family ID: |
26861528 |
Appl. No.: |
10/165606 |
Filed: |
June 6, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60296582 |
Jun 6, 2001 |
|
|
|
Current U.S.
Class: |
102/201 |
Current CPC
Class: |
F42B 3/113 20130101;
F41A 19/58 20130101 |
Class at
Publication: |
102/201 |
International
Class: |
F42C 019/00 |
Claims
What is claimed is:
1. A laser-ignited cannon comprising: a barrel formed with an
interior region; a cannon breech positioned adjacent to the barrel,
wherein the breech includes a light-transmissive window for
allowing the passage of laser energy into the interior region of
the cannon barrel to ignite a propellant contained therein; a laser
diode ignition assembly optically coupled to the cannon barrel for
directing laser energy through the light-transmissive window of the
breech into the interior region of the cannon; and a power
management system connected to the laser diode ignition assembly
for delivering electrical energy to the laser diode ignition
assembly to controllably generate an ignition beam output.
2. The laser-ignited cannon as recited in claim 1 wherein the laser
diode ignition system includes a laser diode array and an optically
coupled collimator that directs collimated light through the
light-transmissive window of the breech into the interior region of
the cannon barrel.
3. The laser-ignited cannon as recited in claim 2 wherein the
collimator is a laser rod.
4. The laser-ignited cannon as recited in claim 1 wherein the power
management system includes a low voltage power storage device and
battery charger.
5. The laser-ignited cannon as recited in claim 1 wherein the power
management system further includes a controller for controlling the
timing and duration of the laser energy pulse.
6. The laser-ignited cannon as recited in claim 5 wherein the
controller is programmable to deliver electrical power continuously
to the laser diode ignition assembly until ignition of the
propellant has occurred.
7. A laser ignition system for a field cannon comprising: a
collimator formed of a lasing material for collimating a laser
pulse; at least one laser diode disk array formed with a central
aperture, wherein at least a portion of the collimator is
positioned within the central aperture such that the laser diode
disk array may optically side pump the collimator to generate a
collimated laser pulse used as an ignition beam for a field cannon;
and a power management system connected to the laser diode disk
array for controlling the laser pulse length to provide variable
ignition times.
8. The laser ignition system as recited in claim 7 wherein the
collimator is a laser rod.
9. The laser ignition system as recited in claim 7 wherein the
collimator is positioned in a cannon breech such that laser output
of the collimator is directed through a light-transmissive window
in the breech to a propellant positioned in a cannon barrel
interior.
10. The laser ignition system as recited in claim 7 wherein the
laser energy is directly optically coupled to a propellant.
11. The laser ignition system as recited in claim 7 wherein the
electrical power supply is a battery.
12. The laser ignition system as recited in claim 7 wherein the
power management system includes a controller for controlling the
timing and duration of the laser energy delivery.
13. The laser ignition system of claim 12 wherein the controller is
connected to at least one sensor for monitoring the timing and
duration of the laser energy delivery for ignition to provide
feedback on system performance and the need for maintenance.
14. A field cannon with a laser diode array comprising: a field
cannon that includes a breech portion and a barrel portion, wherein
the breech portion and barrel portion are adjoined by a firing
window formed with an optically transmissive material to permit the
passage of light energy therethrough; a laser diode assembly that
is positioned in the breech portion for delivery of a collimated
ignition beam through the firing window, wherein the laser diode
assembly includes a collimator having an end surface and is formed
of a lasing material for collimating a laser pulse; and at least
one laser diode array optically coupled to the end surface of the
collimator such that the laser diode array optically end pumps the
collimator to generate the collimated ignition beam; and a power
management system connected to the laser diode assembly for
powering and controlling the pulse length of the ignition beam.
15. The field cannon of claim 14 wherein the power management
system includes a feedback monitor to detect ignition performance
conditions.
Description
[0001] This patent application claims the benefit of the U.S.
Provisional Patent Application Serial No. 60/296,582 filed on Jun.
6, 2001, which is incorporated by reference in its entirety
herein.
FIELD OF THE INVENTION
[0002] The present invention relates to methods and apparatus for
igniting propellant in field weaponry with laser diode systems.
More particularly, the invention relates to laser diode ignition
systems for field cannons.
BACKGROUND
[0003] Many field cannons are fired today using a combination of
prime charges in cartridges and acceptor charges. A prime charge is
initially loaded into the breech portion of a cannon. The prime
charge is then fired by electrical or percussive means to thereby
ignite the adjacent acceptor charge portions of field cannon
artillery or other propellants. After the field cannon is fired,
the breech of the cannon is opened so that the expended cartridge
of the prime charge can removed and replaced. This approach has
worked for decades, but not without certain disadvantages including
the significant amount of time that is required to manually replace
the prime charges for each round fired by the field cannon.
[0004] In recent years, the use of prime charges in field cannons
has been replaced with flashlamp lasers. A flashlamp is basically
used as a light source to optically pump a lasing medium such as
Nd:glass or Nd:YAG. For example, the United States government has
pursued laser ignition of propellants with flashlamps in an attempt
to avoid using prime charges. By substituting the firing of prime
charges, flashlamp laser ignition systems eliminate the
time-consuming process of removing and replacing the prime charge
cartridges between each discharge. This consequently reduces the
required operating time to fire each round of the cannon, which in
turn allows the cannon to effectively fire more projectiles within
a specified period of time. Flashlamp-pumped laser rod systems are
used in government funded weaponry systems to provide the laser
pulse which ignites artillery propellant. The laser head in this
type of system is typically mounted directly onto the breech of a
field cannon. The pulse of light can be thus fired through a window
formed in the cannon breech in order to illuminate and ignite a
propellant bag. Assuming a sufficient amount of energy is generated
and directed by this laser beam to a suitable portion of the
propellant bag, the ignition of the propellant bag in turn causes
the artillery propellant to ignite and thereby fire the cannon.
[0005] A variety of disadvantages and associated problems exist
however with flashlamp-pumped laser ignition systems. The
flashlamps, which are commonly used to optically pump a selected
lasing medium, usually operate at high-voltages. Because field
cannons are often deployed in harsh environmental conditions
including rain, dust, high humidity and damp weather, flashlamps
and other high voltage equipment can be difficult to operate and
maintain which presents reliability issues. In addition, flashlamp
laser ignition systems are generally not energy efficient devices.
A significant amount of electrical power must be initially provided
at a high voltage level to begin operating the system. The typical
level of efficiency observed when this high voltage electrical
input is converted into the resulting photons, which illuminate the
igniter in the propellant, is estimated to be less than
two-percent. This type of inefficiency and high demand for
electrical power presents even more challenges to the external
power supplies that are needed to recharge these ignition system
for multiple firings. Moreover, with the increasing trend toward
low voltage digital electronics, high voltage components of the
past are also becoming less available as the supplier base and
demand decreases. The long-term ability to continually manufacture
and rely on these types of flashlamp ignition systems for field use
therefore remains uncertain.
[0006] Current flashlamp-based ignition systems also consist of
relatively large components that are cumbersome and difficult to
mobilize. In order to provide sufficient electrical power to
operate the ignition system, relatively large high voltage
capacitors must be used to store the significant amount of
electrical energy which must be accumulated and subsequently
discharged into the electrical circuits rapidly to fire the
flashlamp. Moreover, while these large energy storage capacitors
can rapidly discharge their retained energy, they have been known
to lose a relatively larger percentage of their capacitance when
operating at relatively lower surrounding temperatures. As a
result, it may be necessary to select capacitors that are even
physically larger in order to store enough electrical energy to
operate the flashlamp under a wider range of temperatures. These
less efficient larger and heavier ignition system components can
significantly hamper the mobility and operability of field cannons.
Furthermore, available flashlamp laser ignition systems provide
laser ignition pulses for relatively small time intervals lasting
only approximately five milliseconds. If ignition fails to occur
within this small window of time, there is a hang fire. Subsequent
attempts to ignite the propellant can be made again, but only after
the capacitor bank is allowed to fully recharge for another firing
which cause undesirable delays in the field.
[0007] There is a need for a compact and mobile laser ignition
system that is a safe alternative to current high voltage flashlamp
laser ignition systems. A cost effective and reliable ignition
system is also needed that can be easily maintained and constructed
from components that are readily available.
SUMMARY OF THE INVENTION
[0008] The present invention provides laser diode ignition systems
for field cannons and weaponry. The ignition systems described
herein are relatively inexpensive to manufacture and maintain. The
laser diodes selected for these systems are generally low-voltage,
compact light sources which are energy efficient. In accordance
with various aspects of the invention, the energy output of these
devices can be combined as an array or a series of redundant laser
diodes assemblies to provide safe and reliable ignition systems for
field cannons and weaponry. A collimator such as a laser rod may be
selected to direct the output from these laser diode assemblies as
multiple collimated ignition beams. The particular features of the
described embodiments in the following specification may be
considered individually or in combination with other variations and
aspects of the invention.
[0009] It is an object of the invention to provide methods and
systems for laser diode ignition of field cannons and weaponry. A
series of one or more laser diodes can be combined to deliver
sufficient laser output in the aggregate to effectively and
reliably ignite weaponry propellants. The collimated laser beams
provided by the laser diode ignition systems herein deliver focused
and energy efficient output for field cannons and other weaponry in
a safe and reliable manner without the need for high-voltage
equipment.
[0010] Another object of the invention is to provide laser diode
ignition systems with built-in redundancy and increased
reliability. Some embodiments of the invention utilize multiple
laser diodes to increase the intensity and/or likelihood of
igniting artillery propellant. The laser ignition systems further
provide the weaponry operator with valuable control and feedback on
the operating performance of the ignition system which can provide
extended firing times as needed to avoid hangfires. Continuous and
extended laser pulses can be thus provided until ignition to ensure
adequate delivery of energy for more reliable field weapon
operation.
[0011] With respect to another aspect of the invention, methods are
provided herein to operate field cannons and weaponry with laser
diode ignition systems. A laser diode array may be initially
selected to end pump and/or side pump a collimator or collimating
rod which delivers a more directed energy output to artillery
propellant. The energy output may consist of collimated ignition
beams which can pass through the firing window of a weapon.
Additionally, the duration of the pulses may be controlled and
extended as necessary to help ensure proper ignition of the
propellant. The invention further provides reliable methods of
igniting weaponry with built-in redundancy in that multiple
ignition beams are delivered across a wider area to provide a
greater likelihood of propellant ignition and more reliable
operation of the weapon. The ignition systems herein may include
multiple diode arrays with multiple diodes per array to provide
numerous ignition beams.
[0012] Other objects and advantages of the invention will become
apparent upon further consideration of the specification and
drawings. While the following description may contain many specific
details describing particular embodiments of the invention, this
should not be construed as limitations to the scope of the
invention, but rather as an exemplification of preferable
embodiments. For each aspect of the invention, many variations are
possible as suggested herein that are known to those of ordinary
skill in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a simplified cross-sectional view of a field
cannon laser diode ignition system provided in accordance with the
invention.
[0014] FIG. 2 is a cross-sectional view a laser diode disc array
provided herein for optically side pumping an ignition
collimator.
[0015] FIG. 3 illustrates an ignition collimator that is optically
pumped by one or more laser diode disk arrays to generate
sufficient laser output with relatively low divergence to pass
through a field cannon firing window.
[0016] FIG. 4 is a simplified block diagram of a laser diode
ignition system with a resonator cavity formed with an external
mirror or reflector.
[0017] FIG. 5 is a simplified cross-sectional view of yet another
embodiment of the invention that provides a field cannon ignition
system that generates a highly collimated laser output by optical
end pumping of a collimating rod.
[0018] FIG. 6 depicts the optical coupling or combining of laser
output from a series of laser diodes and optical fibers to direct a
plurality of light beams towards a collimator.
[0019] FIG. 7 is a cross-sectional view of an end pumped
collimating (lasing) rod that receives optical output from a
plurality of laser diodes to provide a series of collimated light
beams.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The invention provides methods and apparatus for ignition of
propellants in field cannon and weaponry using laser diode
assemblies. Laser diodes are relatively compact semiconductor
devices that do not require the use of high-voltage equipment such
as those demanded by flashlamp lasers. The availability and
versatility afforded by these light sources as described herein can
provide more reliable ignition systems that are well suited for use
in the field.
[0021] As shown in FIG. 1, a laser diode ignition system 10 may be
selected and installed in a field cannon 12 in accordance with the
invention. The principles of the invention herein are applicable to
Crusader field cannons or other propellant-based field weaponry.
The field cannon 12 (not drawn to scale) may be constructed with a
cannon breech 14 and a barrel portion 16. The cannon breech 14 may
be formed with a firing window 15 leading into the interior region
17 of the cannon barrel 16. Within the cannon barrel 16, a round of
artillery 11 can be positioned for firing. The artillery round 11
basically consists of a projectile 13 and a propellant section 18
which can be initiated by the laser ignition system 10 herein. A
powder bag 20 may be placed within a relatively rearward
compartment of the propellant section 18. The back portion of the
propellant 18 may include a prime charge 22 formed with a Mylar
disk or back covering 21 which permits laser ignition beams to pass
therethrough in order to ignite the propellant bag 20. The bag 20
may contain black powder or other combustible material. The
ignition of the propellant bag 20 consequently ignites the adjacent
artillery propellant 18 in order to fire the projectile 13 from the
field cannon 12.
[0022] The laser diode ignition assemblies herein may be installed
in the breech section 14 of the field cannon 12. As shown in FIG.
1, a laser diode assembly or module 10 may be connected to and
driven by a variety of power storage and control apparatus. A
portable external power source 22 may provide electrical energy to
a battery charger 23 for charging a relatively compact and low
voltage power storage, i.e. battery 24. The low voltage power
storage or battery 24 can be charged as needed by a conventional
battery charger and the external power source 22. The power storage
24 may be in turn connected to a controller 25 to drive the laser
diode assembly 10. The controller 25 can be configured to control
the timing and duration of an energy pulse by regulating the
electrical current delivered to the laser diode assembly 10
positioned in the cannon breech 14. Additionally, the laser diode
assembly 10 shown may further include a collimating ignition rod 26
with one or more laser diode arrays 28 to optically end pump or
side pump the rod. It shall be understood that for purposes of
describing the invention, the collimators or collimating rods
referenced herein shall include laser rods that are optically
pumped by laser diodes to efficiently collimate the laser diode
output. In this illustrated embodiment of the invention, the light
energy from the laser diode array 28 optically pumps the adjacently
positioned collimating rod 26 to generate an ignition beam. The rod
26 is typically formed from a solid state medium and any suitable
lasing material known to those in the field including Nd:YAG and
YV04:YAG. A variety of diameters may be selected for the
collimating rod 26 ranging from 2 to 10 mm or greater. While other
configurations may be selected for the lasing medium such as a slab
or wafer, a cylindrical shaped laser rod with a predefined length
is preferable for the applications described herein. It has been
observed that uncollimated laser output from edge emitting low
voltage laser diodes is too diffuse to provide propellant ignition
within an acceptable time frame or across a large depth of field.
The collimated ignition beams provided by the collimating rod
assemblies herein however offer more less divergent output that do
not spread significantly as they pass through the firing window of
the cannon. A relatively higher energy density is thus created by
these laser ignition beams which may traverse a relatively large
depth of field or gap within the cannon breech to ignite artillery
propellant.
[0023] The collimating rod 26 may be positioned just outside the
cannon breech 14 so that the laser output passes through the
light-transmissive firing window 15 into the cannon barrel interior
17. The firing window 15 may be formed of sapphire or other durable
optical material that is suitable for field weapons. The laser
energy can thereby initiate a pyrotechnic reaction by passing
through the Mylar disc and/or back covering 21 of the propellant
18. The laser ignition beam may first ignite the propellant bag 20,
which in turn ignites surrounding artillery propellant 18. The
artillery propellant 18 may be formed in a substantially
donut-shape around the bag 20 or other appropriate configuration.
The expanding gases from the ensuing reaction and complete
deflagration of the propellant 18 thereby propels the projectile 13
from the field cannon barrel 16. A series of one or more ignition
pulses can be also continuously fired by the laser diode assembly
10 until the propellant 18 is ignited. The pulse length or pulse
times can be variably adjusted in accordance with types of weaponry
and changes in atmospheric or external conditions which may prolong
requisite ignition times. Furthermore, the controller 25 may be
connected to a sensor or a feedback monitor to detect and signal
ignition of the propellant 18 or other conditions, or even
automatically stop the flow of electrical energy to the laser diode
28 when the weapon is successfully fired. The controller 25 may be
also programmed to instruct the laser diode array 28 to deliver a
predetermined pulse length in accordance with an anticipated time
to ignite the propellant. Depending on the types of ammunition and
propellants (Zones 1-6) that are used for the field weapon,
appropriate ignition pulse lengths may be also selected and
programmed by the controller 25 in a predetermined manner. It has
been further observed that longer pulse times may be required as
the optical quality of firing windows diminishes over extended
periods of time and usage. Noting this extension in time provides
feedback that the window needs maintenance.
[0024] FIG. 2 illustrates a laser diode disk array 30 which may be
selected for the ignition systems provided herein. A series of one
or more of these arrays 30 may optically side pump an ignition
collimator (laser rod) 33 to generate a collimated output beam.
Each laser diode disk array may be in communication with and
connected to the field gun controller. Certain applications or
types of artillery may require firing of only certain laser diodes,
while other types of propellants may require the combined
collimated output of all laser diodes within the disk array. The
laser diode disc array 30 may be formed with a mounting portion 32
that secures the assembly within a selected portion of the field
cannon. The disk array 30 may include multiple individual laser
diodes 34 that are spaced apart and positioned to direct their
output toward a central region or aperture 35 occupied by the
collimating (lasing) rod 33. The measured diameter of the
collimating (lasing) rod 33 may range from one-millimeter or
greater depending upon certain applications. The central region 35
of the laser diode disk array 30 may be modified accordingly with
appropriate clearance to surround and effectively side pump the
laser rod 33. In this embodiment of the invention, five laser diode
bars were selected for purposes of illustration. It shall be
understood however that any number of one or more laser diode bars
34 may be selected for the side pumped collimating rod assemblies
provided herein. The output of the individual laser diodes 34 may
also optically pump the laser rod at an angle perpendicular to the
external surface of the rod 33 or at any other angle to feed the
lasing medium with light energy. Furthermore, it has been further
observed that the side pumped laser diode arrays herein are often
physically smaller than those laser diode assemblies that provide
end pumping. A more compact light source to optically pump the
ignition collimating rod may therefore reduce costs and save space
within the field cannon.
[0025] The ignition collimators or collimating rods herein may be
optically pumped by one or more laser diode disk arrays to generate
a sufficient ignition pulse which can pass through a field cannon
firing window. As shown in FIG. 3, a single side pumped collimating
rod assembly 36 may be fitted with one or more laser diodes disk
arrays 38 that are slipped over and positioned along the
longitudinal axis of the laser rod 39. A series of laser diode
arrays (Laser Diode Array #1, Laser Diode Array #2 . . . Laser
Diode Array #n) may be selected to optically pump the ignition
collimating rod 39 in order to generate the laser output needed to
ignite various types of propellants under different operating
conditions. Each of the laser diode disk arrays 38 may be wired to
the weapon control unit to receive instructions and power to
optically pump the rod 39. Moreover, any number of one or more of
the laser diode arrays 38 may be fired or not fired in accordance
with predetermined ignition requirements. Under certain operating
and weather conditions, certain types of propellants may not
require operation of all arrays within the laser diode ignition
assembly. In other instances where shorter ignition times are
required or greater laser output levels are desired, all laser
diode arrays within the assembly may be directed to optically pump
the ignition collimating rod or collimator. Depending on the
optical transmissivity of the firing window or the physical
deformities or characteristics of certain propellant bags, more
heat energy may be also delivered as needed in certain instances to
achieve ignition. A variety of ignition times may be provided
herein ranging up to 50 milliseconds or longer. It shall be
understood that the laser diode disk arrays illustrated herein for
purposes of illustration are donut-shaped light sources. Those of
ordinary skill however will understand that other types and shapes
of laser diodes may be selected herein in accordance with the
invention to side pump the lasing medium in order to generate an
ignition beam.
[0026] The collimating rods selected herein may be conventionally
formed with a lasing medium that is bound by a pair of mirrors or
reflectors as is known in the field. By optically side pumping the
collimating (lasing) rod or medium with light energy from laser
diodes, the light is reflected back and forth within the resonant
cavity formed by the end mirrors. While it may be desirable for
many applications to form a collimating rod with a monolithic
construction, it may be more preferable in certain systems to
select external mirrors to define the laser cavity. In FIG. 4, for
example, another embodiment of the invention may be configured with
an external mirror 42. The collimating rod 44 may be optically side
pumped as described herein with laser diodes to generate collimated
laser output. The output may be used as an ignition beam which
passes through the firing window 46 of a field cannon to ignite
artillery propellant within the barrel region of the weapon. It
shall be understood that various ignition beam profiles may be
generated herein depending upon certain factors including the
output power levels and beam diameters of the laser diodes and
collimators. The number of laser diodes with each array, and total
number of laser diode arrays selected to optically side pump the
lasing medium, may also affect the ignition beam profile and
certain concentrations of energy densities. In any event, the
collimating rods herein are intended to collimate the light
received from the laser diodes with less divergence and greater
concentration within a defined area to provide more reliable and
efficient laser ignition of field weaponry.
[0027] Another aspect of the invention provides end pumped laser
diode ignition systems for field weaponry. As shown in FIG. 5,
another embodiment of the invention provides a field cannon
ignition system 50 that generates a collimated ignition beam by
optically end pumping a collimating rod 56. As described herein,
the ignition collimator beam may be directed to pass through a
firing window 51 of a field cannon 52 in order to ignite a prime
charge 66 having a propellant bag 53 positioned within a relatively
rearward portion of an artillery propellant 56 section. The
ignition of the propellant bag 53 may in turn ignite surrounding
propellant 56 in order to fire a projectile 59 from the interior
region 57 of the cannon barrel 54. Furthermore, the end pumping
laser diode assemblies described herein may be installed in the
cannon breech section 67 of the field cannon 52. A controller 65
may also control the firing sequence and duration of the laser
diode assembly 50. The ignition system may include a relatively
portable low voltage power storage or battery 64 that can be
charged with a batter charger 63 and power source 62. It shall be
understood that other power management and control systems may be
selected to operate the laser diode ignition systems described
herein. In order to generate an ignition beam pulse, a series of
one or more laser diodes 58 optically end pump a substantially
adjacent collimating rod 56 which may be formed from a lasing
material. The collimating rod 56 will collimate the light energy
received from the laser diode(s) 58 to form relatively concentrated
and less divergent ignition beam(s). For many applications, a
collimating rod formed of suitable lasing material may be selected
to more quickly generate requisite ignition beams. However, a basic
optical collimator or optical device with configured lenses may be
used alternatively with adequately powered laser diodes in order to
provide desired ignition beam diameters and energy densities in
accordance with the invention. Lasing rods are effective
collimators which direct light pulses from laser diodes to ignite
propellant-based weaponry. It shall be understood that the
fundamental principles associated with laser rod operation herein
are basically the same for both end pumped and side pumped laser
diodes except for the different equipment used and the direction in
which light is pumped into the lasing medium.
[0028] FIG. 6 depicts the optical coupling or combining of laser
output from a series of laser diodes which is provided by end
pumping ignition systems herein. The end pumping laser diode
ignition systems herein may include a series of laser diodes (LD1,
LD2 . . . LDn) that optically feed into a plurality of optical
fiber cables 69. The fiber cables may be formed with various
lengths of up to one meter or more so that an adequate degree of
free movement may be provided during operation and recoil of a
field cannon. All of the transmitted light pulses from the laser
diode array may be thus combined with suitable optical couplers or
combiners. The number of input ports for the coupler may equal the
number of laser diodes or individual emitting laser elements on the
laser diode bars selected for the ignition system. The coupler may
be formed with a single output port 70 to direct all of the laser
diode optical transmissions into a collimating (lasing) rod. The
resulting ignition laser beam or series of beams can be formed and
directed through a light-transmissive window located in the cannon
breech into the interior of a cannon barrel. It shall be understood
that lenses and other optical components and coatings may be
selected to assist in collimating the combined laser diode output
into the cannon breech. As with the other laser diode arrays
described herein for either end pumping or side pumping
applications, each laser diode within the array may have various
power output levels ranging from approximately 1 to 50 watts or
higher. The laser diode may be compact and operate at relatively
low voltages as low as 5 volts or even lower. These devices are
relatively efficient light sources and can convert approximately
50% or more of electrical power into optical power to provide small
and durable components for field use. Some laser diodes may be
configured to efficiently operate for hundreds or even thousands of
ignition cycles from a single charged battery. A variety of
commercially available laser diodes may be selected with different
power output levels in accordance with the invention such as
Coherent Semiconductor FAP-808-60C-1200BL for end pumping and
Coherent Seminconductor B1-81-60Q-49-50-A for side pumping. For
example, in order to achieve a desired output of 40 watts, an
appropriate number of laser diodes with predetermined power levels
and efficiency may be selected as known by those of ordinary skill.
More than one laser diode may be optically coupled to the laser rod
to add to the resultant ignition beam. It has been observed that by
increasing the number of laser diodes which optically end pump the
collimator (laser) rod, as well as those side pumping, there is a
proportional increase in the number of ignition beam spots.
Accordingly, multiple ignition beams may be generated by the end
pumped laser diode ignition systems herein to provide redundancy
and to increase the likelihood propellant ignition.
[0029] For example, as shown in FIG. 7, an end pumped collimating
(lasing) rod 72 may transmit multiple ignition beams generated by a
plurality of end pumping laser diodes. When viewing the lasing rod
from a cross-sectional view, it has been observed that the
resultant ignition beam profile basically consists of a number of
ignition beam spots which corresponds to the number of particular
laser diodes selected for the ignition system. The optical output
from the plurality of laser diodes provides a series of collimated
light beams producing such spots. The ignition spots have been
observed to vary in size ranging from one-half millimeter to
four-millimeters or greater, and may be dependent on the size of
the input beams and pulse lengths. The geometry and sizes of these
spots will also vary according to the optical strength or power
(watts) and output diameters (mm) of the selected laser diodes. For
certain field cannon ignition assemblies, it may be preferable to
select relatively high powered laser diodes with smaller output
diameters. Other embodiments of the invention may alternatively
include relatively lower powered laser diodes having larger output
diameters to ignite propellant.
[0030] Another aspect of the invention provides methods of igniting
propellants in field cannons with laser diode assemblies. The laser
diode assemblies such as those described herein may include laser
diode arrays that either optically end pump or side pump a
collimator such as a laser rod. The optical output from the laser
diodes are collimated by the laser rod to form an ignition beam
pulse. The ignition beam pulse may be sustained as needed to ensure
ignition of artillery propellant. Various methods of holding the
ignition beam are thus provided with the laser diode ignition
systems described herein. A suitable power management and
controller may be also selected to communicate and drive the laser
diode assemblies. Other methods of igniting field weaponry are
provided herein in accordance with the operation of the field
cannons and weaponry provided above.
[0031] While the invention has been described with reference to the
aforementioned specification, the descriptions and illustrations of
the preferred embodiments herein are not meant to be construed in a
limiting sense. It shall be understood that all aspects of the
invention are not limited to the specific depictions,
configurations or relative proportions set forth herein which
depend upon a variety of conditions and variables. Various
modifications in form and detail of the embodiments of the
invention, as well as other variations of the invention, will be
apparent to a person skilled in the art upon reference to the
present disclosure. It is therefore contemplated that the appended
claims shall cover any such modifications, variations or
equivalents of the described embodiments as falling within the true
spirit and scope of the invention.
* * * * *