U.S. patent application number 11/678039 was filed with the patent office on 2008-01-03 for method for detecting a source of an incoming laser.
This patent application is currently assigned to Honeywell International Inc.. Invention is credited to Jan Jelinek, Michael L. Rhodes, Vicraj T. Thomas, Philip J. Zumsteg.
Application Number | 20080001064 11/678039 |
Document ID | / |
Family ID | 34063253 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080001064 |
Kind Code |
A1 |
Thomas; Vicraj T. ; et
al. |
January 3, 2008 |
Method For Detecting a Source of an Incoming Laser
Abstract
A system and method for laser source detection. An exemplary
embodiment of the system includes a first array of lenses, a second
array of opto devices (including light sources and light
detectors), and at least one processor. By positioning the array of
lenses to determine the lens position at which energy from an
incoming laser is greatest on the light detectors, the approximate
location of the laser source may be determined. Upon determining
the source, responsive action may be taken. If the incoming laser
is from a friendly party, a friendly-party notification may be
provided. If the incoming laser is from an enemy, reciprocal
targeting or false reflections may be employed.
Inventors: |
Thomas; Vicraj T.; (Golden
Valley, MN) ; Rhodes; Michael L.; (Richfield, MN)
; Zumsteg; Philip J.; (Shorewood, MN) ; Jelinek;
Jan; (Plymouth, MN) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Assignee: |
Honeywell International
Inc.
Morristown
NJ
|
Family ID: |
34063253 |
Appl. No.: |
11/678039 |
Filed: |
February 22, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10622819 |
Jul 18, 2003 |
7196301 |
|
|
11678039 |
Feb 22, 2007 |
|
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Current U.S.
Class: |
250/206.1 |
Current CPC
Class: |
G01S 3/789 20130101;
H01L 2924/0002 20130101; H01L 2924/0002 20130101; H01L 27/14618
20130101; H01L 2924/00 20130101; G01S 3/784 20130101 |
Class at
Publication: |
250/206.1 |
International
Class: |
H01S 3/00 20060101
H01S003/00 |
Goverment Interests
GOVERNMENT CONTRACT
[0002] The Government may have rights in this invention pursuant to
Contract F33615-02-C-1175, awarded by the Department of the Air
Force.
Claims
1. A method for detecting a source of an incoming laser,
comprising: determining a direction of an incoming laser;
determining a wavelength of the incoming laser; determining whether
the incoming laser is from a friendly party; and upon determining
that the incoming laser is from a friendly-party, providing a
friendly-party notification.
2. The method of claim 1, further comprising: upon determining that
the incoming laser is from an enemy, targeting the source of the
incoming laser.
3. The method of claim 1, further comprising: upon determining that
the incoming laser is from an enemy, transmitting at least one
laser in a plurality of different directions to create a false
reflection.
4. The method of claim 1, wherein determining the direction of the
incoming laser includes determining an approximate location of the
source.
5. The method of claim 4, wherein determining the direction of the
incoming laser further includes determining a confidence level of
the determined approximate location of the source.
6. The method of claim 1, wherein determining the wavelength of the
incoming laser includes utilizing different detectors sensitive to
different wavelengths.
7. The method of claim 1, wherein determining whether the incoming
laser is from a friendly party includes examining an optical code
carried by the incoming laser.
8. The method of claim 7, wherein the optical code includes an
indication of the pulse repetition frequency of a laser
emitter.
9. The method of claim 7, wherein the optical code is selected from
the group consisting of A-Code laser codes (AGM-114K Hellfire
missile) and NATO STANAG No. 3733.
10. The method of claim 2, wherein providing a friendly-party
notification includes using a laser to transmit an identification
code to the source.
11. The method of claim 3, wherein targeting the source of the
incoming laser includes painting the source with a laser.
12. The method of claim 4, wherein the at least one laser is part
of an array of semiconductor lasers disposed under a corresponding
plurality of lenses positionable by actuators controlled by at
least one processor.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/622,819 filed Jul. 18, 2003
BACKGROUND
[0003] The present invention relates to laser source detection, and
more particularly, to a system and method for laser source
detection.
[0004] Modern weapons systems frequently use lasers to assist in
targeting. Because the path of a laser beam is essentially a
straight line, it can be used as a starting point for sighting a
weapon, and adjustments may be made to compensate for gravity,
wind, and other factors. Some weapons systems employ a beam-riding
scheme, in which a munition, such as a missile, tracks the path of
a laser beam to a target painted by the laser. One of the effects
of laser-assisted targeting is improved accuracy and precision.
[0005] At the same time, a party painted by such a laser needs to
be able to react in a quick and appropriate manner. Regardless of
whether the source of the laser is an enemy or friendly party, the
painted party needs to avoid any munitions that may be fired. If
the source of the painting laser is a friendly party, the painted
party will preferably be identified as a non-enemy, and no
munitions will be fired. "Friendly-party notification" is becoming
increasingly important, as friendly-fire incidents are making up
increasingly larger percentages of total wartime casualties.
[0006] One approach similar to friendly-party notification is CIDDS
(Combat IDentification Dismounted Soldier). In CIDDS, an
interrogator set shines a laser on a target. If the targeted
soldier is friendly and has a similar system, laser detectors will
decode the signal and a radio transmitter on the targeted soldier
responds with a coded message indicating he or she is friendly.
This response message breaks radio silence, and thus, is a security
risk. The CIDDS system is strictly a combat identification system,
and does not detect or respond to lasers from range finders,
battlefield illuminators, or target designator systems. The CIDDS
helmet-mounted transponder is about 335 grams and has a range of
approximately 1100 meters.
[0007] Another approach that provides a greater range (about 5500
meters ground-to-ground and 8000 meters air-to-ground), but is much
heavier, is BCIS (Battlefield Combat Identification System). This
vehicle-mounted system operates similarly to, but is not compatible
with, CIDDS. Because communication responses are by radio, radio
silence is broken. While BCIS is capable of identifying the source
of a laser within a quadrant, it is still primarily a combat
identification system, and does not detect or respond to lasers
from range finding systems, battlefield illuminators, or target
designator systems. Other similar systems, such as LWS-CV, also
exist.
[0008] A technology that may improve laser detection capabilities
is HARLID (High Angular Resolution Laser Irradiance Detector).
While still primarily a prototype system, HARLID uses an array of
detectors to locate the source of a laser within one degree
(azimuth and elevation). However, HARLID is purely a detection
system and provides no combat identification or reciprocal
targeting capabilities. Raytheon's ANVVR-1 Laser Warning Receiver
may be an example of a HARLID-based system.
[0009] Other approaches have been developed to detect target
designator, range finder, and beam rider threats, but actions taken
upon detection (e.g. friendly-party notification) still suffer from
shortcomings. To improve battlefield situation awareness, it would
be desirable to accurately detect if a soldier or vehicle has been
painted by a laser (e.g. range finder, target designator, beam
rider, spotting beam, battlefield illuminator), locate the source
of the laser, and provide friendly-party
identification/notification. In addition, it would be desirable, in
some embodiments, to provide reciprocal targeting to respond to
imminent threats. The preferred solution should be relatively
lightweight, easy-to-deploy, small, and interfaceable with existing
systems, such as situation awareness systems (e.g. Objective Force
Warrior displays and vehicle cockpit display systems) and target
designators.
SUMMARY
[0010] A system and method for laser source detection are
disclosed. An exemplary embodiment of the system includes a first
array of movable lenses with associated positioning mechanisms, a
second array of opto devices (including laser sources and laser
detectors), and at least one processor. By positioning the
individual lenses in the array to maximize the energy on their
detectors, the approximate location of the laser source may be
determined. Upon determining the source, responsive action may be
taken. If the incoming laser is from a friendly party, a
friendly-party notification may be provided. If the incoming laser
is from an enemy, reciprocal targeting may be used to allow a
laser-guided munition to be fired. Alternatively, at least one
laser may be transmitted in a plurality of directions to cause
false reflections, in an attempt to break a lock maintained by an
incoming laser-guided munition.
[0011] These as well as other aspects of the present invention will
become apparent to those of ordinary skill in the art by reading
the following detailed description, with appropriate reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a simplified block diagram illustrating a system
for laser source detection, according to an exemplary embodiment of
the present invention;
[0013] FIG. 2 is a perspective pictorial diagram illustrating a
system for laser source detection, according to an exemplary
embodiment of the present invention;
[0014] FIG. 3A is a pictorial diagram illustrating a top view of a
representative cell in a system for laser source detection,
according to an exemplary embodiment of the present invention;
[0015] FIG. 3B is a pictorial diagram illustrating a side view of a
representative cell in a system for laser source detection,
according to an exemplary embodiment of the present invention;
[0016] FIGS. 4A and 4B are pictorial diagrams illustrating
placement of a system for laser source detection on military
vehicles, according to exemplary embodiments of the present
invention;
[0017] FIGS. 5A and 5B are pictorial diagrams illustrating
placement of a system for laser source detection on military
personnel, according to exemplary embodiments of the present
invention; and
[0018] FIGS. 6A and 6B show a flow diagram illustrating a method
for laser source detection, according to an exemplary embodiment of
the present invention.
DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS
[0019] FIG. 1 is a simplified block diagram illustrating a system
100 for laser source detection, according to an exemplary
embodiment of the present invention. The system 100 includes an
array 102 of cells, such as cell 104. The system 100 is operable to
detect a remote laser source based on energy incident of the
system. Upon detecting the laser, the facility 106 upon which the
array 102 is mounted can take appropriate responsive action, such
as transmitting a communication (e.g. a friendly-party
notification) to the laser source or taking defensive action (e.g.
transmitting light back toward the source to break any lock that an
incoming light-guided munition may have on the facility 106).
[0020] In a preferred embodiment, the array 102 comprises many
(e.g. tens, hundreds, thousands or more) cells 104, with each cell
being small (e.g. approximately 1 mm.sup.2), resulting in an
overall array size of approximately 0.1 m.sup.2 for use on military
personnel to approximately 1 m.sup.2 for use on military vehicles
or installations). Smaller array sizes may be advantageous for
portability and/or ease of placement, while larger array sizes will
allow for more accurate laser source detection and location.
[0021] As described in detail in FIGS. 2, 3A, and 3B, the array 102
preferably includes cells 104 for detecting light as well as cells
104 for transmitting light. So configured, the system 100 is
operable to detect and locate light, as well as transmit light back
for communication and/or reciprocal targeting. Because transmitted
communications are preferably composed of light signals, radio
silence is not compromised, resulting in potentially safer
conditions for the facility 106. Another advantage of using light
instead of radio is it is less susceptible to jamming and spoofing.
For purposes of convenience and to more accurately describe how
embodiments of the invention are likely to be used in the field,
the remainder of this detailed description will assume the light is
from a laser source.
[0022] FIG. 2 is a perspective pictorial diagram illustrating a
system 200 for laser source detection, according to an exemplary
embodiment of the present invention. The system 200 includes a lens
array 202, an opto device array 204, and a driver array 206 that
includes one or more compute elements. The system 200 is also
likely to include an interface (not shown) that may be used to
connect the system 200 to other equipment, such as weaponry and
communications and/or computing systems, for example.
[0023] The lens array 202 includes a plurality of lens array cells
208, with each cell 208 preferably including an integrated MEMS
(Micro-Electro-Mechanical Systems) diffractive microlens and
actuator for positioning the lens. Each cell is preferably about 1
mm.sup.2, however other sizes may be used as well. A smaller cell
size will allow for increased cell density and improved accuracy.
Details of a preferred implementation of the cell 208 are presented
in FIGS. 3A and 3B.
[0024] The opto device array 204 includes a plurality of opto
device cells 210, with each cell 210 preferably including either an
optical detector (such as a photodiode) or a light source, such as
a laser. Each cell 210 in the opto device array 204 is preferably
associated with a respective cell 208 in the lens array 202 to
enable each microlens to operate in cooperation with its associated
optical detector or light source.
[0025] The driver array 206 includes a plurality of driver cells
212 and provides power, communication, and computation
functionality to the system 200. Power may be provided by
connection to an external power source, such as a battery or solar
cell array, or it may emanate from an integrated power source.
Communications may be provided by a grid of connections linking the
plurality of driver cells 212 to one another. In addition, the
driver array 206 may provide one or more output signals to external
equipment, such as weaponry or communication/computation equipment,
for example. In addition to power and communications, the driver
array 206 may provide the processing capability to perform
computations for determining the location of a detected remote
laser source and/or for positioning microlenses in the lens array
208 for to cause lasers in the system 200 to perform reciprocal
targeting. In a preferred embodiment, the driver array 206 includes
a plurality of distributed processors, rather than a single
processor for the entire system 200. If each lens array cell 208
and associated opto device cell 210 has its own processor in its
own associated driver cell 212, the computational burden is
distributed throughout the entire array, resulting in simplified
calculations and faster operation. The distributed processors may
be implemented in any of several forms, including commercially
available micro-processors (e.g. from IBM, HP, and others) or ASICs
(Application Specific Integrated Circuits), for example. To allow
the processors to perform calculations, a memory may provided with
each processor (or for use by a plurality of processors).
[0026] In a preferred embodiment, the system 200 is approximately
between 0.1 m.sup.2 for use on military personnel to approximately
1 m.sup.2 for use on military vehicles or installations. Of course,
smaller or larger implementations may be used to meet design goals,
such as size, power draw, and/or accuracy. A larger implementation
is likely to be more accurate at the expense of increased power
consumption, while a smaller implementation will be more portable
and lightweight. In addition, while the system 200 is shown as a
single contiguous unit, it may alternatively be distributed less
densely over a larger area. This may improve accuracy, but might
sacrifice speed due to longer links between individual cells.
[0027] Because the system 200 is preferably constructed using MEMS
hardware, it is lightweight and easy to deploy. Power consumption
is minimal, with very little power consumption until a light
source, such as a semiconductor laser, is deployed.
[0028] FIGS. 3A and 3B are pictorial diagrams illustrating top and
side views, respectively, of a representative cell 300 in an
apparatus for laser source detection, according to an exemplary
embodiment of the present invention. The cell 300 includes a lens
portion 302, an opto device portion 304, and a driver portion 306.
Portions 302, 304, and 306 may be respective portions of arrays
202, 204, and 206 described with reference to FIG. 2.
[0029] The lens portion 302 includes a microlens 308, y-axis comb
drives 314a and 314b, x-axis comb drives 316a and 316b, x-axis
suspension members 318a-d, y-axis suspension members 320a-d, a base
portion 322, and lens holders 324a and 324b. The representative
cell 300 has an approximate size of 1 mm.sup.2.
[0030] The structure of lens portion 302 may be realized through
standard MEMS processing techniques, such as a series of silicon
structuring steps including patterning and etching appropriate
layers of silicon and oxides. The suspended lens arrangement may be
constructed, for example by depositing an optically transparent
material over a sacrificial layer, which is removed to produce the
cavity through with the lens may focus light from a remote source
or from an opto device contained in the opto device portion. In a
preferred embodiment, the lens is approximately 0.1 mm in diameter
and has a travel range of approximately 0.05 mm in the x- and y-
directions, a resolution of approximately 0.0005 mm (0.5 .mu.m), a
speed of 5-10 kHz, a focal length of approximately 0.12/0.32 mm,
and a refractive index of about 3.4.
[0031] A potential may be applied to the comb drives 314a-b and
316a-b to cause an electrostatic force to move the microlens 308 in
the x- and y-axes. The final position of the microlens 308 may be
determined through any of a number of techniques, such as by
measuring the capacitance of the comb drives or by applying a
sinusoidal wave voltage to the comb drives at the natural resonant
frequency of the suspended microlens, so that its position may be
calculated based on the applied voltage. Determining the position
of the lens allows the cell 300 to be used to determine the
location of the source of incoming light, or to confirm that
outgoing light is accurately positioned.
[0032] The suspension members 318a-d and 320a-d allow movement of
the microlens 308 along the x- and y-axes of the comb drives 314a-b
and 316a-b. Although actuators and movement mechanisms have been
described and illustrated for two perpendicular axes, other
arrangements for movement and actuation may also be used.
[0033] The opto device portion 304 includes an opto device 310, and
may include additional circuitry and/or connections to enable the
opto device 310. Alternatively, some or all of the additional
circuitry and/or connections may be located elsewhere, such as in
the driver layer 306.
[0034] In the example of FIGS. 3A and 3B, the opto device is a
semiconductor laser, namely, a VCSEL (Vertical Cavity Surface
Emitting Laser). Other types of semiconductor lasers may be used,
as may other types of light sources. Aperature 328a-b provides the
opening for emitting laser energy. The microlens 308 is located at
a sufficient distance from the opto device 310 (i.e. the VCSEL) to
allow the emitted laser to be focused adequately.
[0035] Details on construction and operation of surface emitting
lasers may be found, for example, in "Surface-emitting microlasers
for photonic switching and interchip connections," Optical
Engineering, 29, pp. 210-214, March 1990. For other examples, note
U.S. Pat. No. 5,115,442, by Yong H. Lee et al., issued May 19,
1992, and entitled "Top-emitting surface emitting laser
structures," and U.S. Pat. No. 5,475,701, by Mary K. Hibbs-Brenner,
entitled "Integrated laser power monitor," which are both hereby
incorporated by reference. Also, see "Top-surface-emitting GaAs
four-quantum-well lasers emitting at 0.85 .mu.m," Electronics
Letters, 26, pp. 710-711, May 24, 1990. The laser described has an
active region with bulk or one or more quantum well layers. The
quantum well layers are interleaved with barrier layers. On
opposite sides of the active region are mirror stacks formed by
interleaved semiconductor layers having properties such that each
layer is typically a quarter wavelength thick at the wavelength (in
the medium) of interest thereby forming the mirrors for the laser
cavity. There are opposite conductivity type regions on opposite
sides of the active region, and the laser is turned on and off by
varying the current through the active region. However, a technique
for digitally turning the laser on and off, varying the intensity
of the emitted radiation from a vertical cavity surface emitting
laser by voltage, with fixed injected current, is desirable. Such
control is available with a three terminal voltage-controlled VCSEL
described in U.S. Pat. No. 5,056,098, by Philip J. Anthony et al.,
and issued Oct. 8, 1991, which is hereby incorporated by
reference.
[0036] The opto device 310 may alternatively be a light detector,
such as a photodiode. While a semiconductor laser, such as a VCSEL,
may be used to transmit light out (e.g. for optical communication
and/or reciprocal targeting), a light detector allows for detection
of incoming light, and, in some embodiments, location of the source
of the received light. The distance (i.e. the focal length) between
the microlens 308 and the opto device 310 (i.e. the photodiode) is
such that light passing through the microlens 308 is substantially
focused onto the opto device 310. Then, as the microlens 308 is
moved along the x- and y-axes, the light detector will be best able
to determine intensity, which, in some embodiments, is used to
determine the location of the source, as described in further
detail below.
[0037] The driver portion 306 includes a processor 312, a
connection 330a-b, a substrate 332, and a spacer layer 334. In some
embodiments, more or fewer components may make up the driver
portion 306.
[0038] The processor 312 is in communication with the lens portion
302 and the opto device portion 304 to provide control,
calculation, and data acquisition functions. For example, the
processor 312 may provide appropriate signals, such as through
semiconductor traces or metallizations, to cause translation of the
microlens 308 in the x-or y-axis and to determine lens position, as
discussed above. Similarly, the processor 312 may control the opto
device 310 (e.g. power-up the VCSEL or receive information from the
photodiode). In determining the lens location at which the
strongest energy is detected, four samples are preferably taken for
each cell 300 to determine a vector toward the center of the laser
energy seen by the cell 300.
[0039] The processor 312 for the cell 300 is shown as a single
cell-based processor, rather than a processor serving many cells or
even the whole array. While a processor could serve many cells in
some embodiments, preferred implementations maintain the one
processor per cell arrangement, to promote faster computation and
control, as speed is essential in a battlefield context. In
addition, the algorithms for determining lens position, calculating
vectors for determining strongest energy locations, and determining
the source of incoming light are preferably done in hardware to
achieve faster and more robust results.
[0040] The connections 330a and 330b allow the processor 312 to
communicate with processors in four neighboring cells. (See, for
example, the neighboring cells and neighboring processors in the
arrays shown in the system 200 of FIG. 2.) The processor 312, in
turn, may also pass on information from all or some of its
neighboring processors to each neighboring processor. As a result,
every processor can obtain communications from every other
processor in the array. Of course, information from cells
containing photodiodes may be used for detecting light (and
possibly location), while information from cells containing
semiconductor lasers may be used for transmitting a focused column
of light.
[0041] By receiving communications corresponding to many cells, the
processor 312 can assist in determining the approximate location of
a light source. In one embodiment, each processor stores a table of
these observations. A partial example of such a table is shown
below as Table A. TABLE-US-00001 TABLE A NODE ENERGY SEEN LOCATION
WHEN 425 1020 45.367.degree. 121.24M 12:00 01.0035 431 1044
45.380.degree. 121.25M 12:00 01.0102 418 989 45.388.degree. 121.24M
12:00 01.0199 . . . . . . . . . . . .
[0042] In a preferred embodiment, tens of thousands of cells 300
are included in each array. When control is distributed over this
many cells processing loads are distributed, errors are averaged,
and greater fault-tolerance is realized. Of course, as MEMS
technology improves fewer cells may provide similar
performance.
[0043] Errors in location of a target, such as the source of
received laser light may be due to errors in positioning the lens
308. Tangential (side-to-side) errors are likely to be very low, so
that a target 1 km away could be located to within 1.0 m. The
radial (distance away) error can be more significant, however. By
including a large number of cells, average errors result in tighter
bounds on the target location. Simple averaging of location
estimates of pairs of cells is not likely to work, however, due to
a highly skewed distribution of location estimates. To ease the
computational burden, alternative coordinate systems, such as an
angular coordinate system can be used, and the results can be
converted to polar or Cartesian coordinates. In a preferred
embodiment, the output of 10,000 pairs of cells 300 1 m apart
includes a tangential location along with an estimated distance and
confidence indicator (e.g. lower bound=967.57 m, upper
bound=1034.68 m, confidence=95%).
[0044] FIGS. 4A and 4B are pictorial diagrams illustrating
placement of systems 402 and 452 for laser source detection on
military vehicles 400 and 450, according to exemplary embodiments
of the present invention. FIG. 5A and 5B are pictorial diagrams
illustrating placement of systems 502 and 552 for laser source
detection on military personnel 500 and 550, according to exemplary
embodiments of the present invention. The systems 402, 452, 502,
and 552 may be similar to the system 200 shown in FIG. 2, utilizing
cells like cell 300 in FIGS. 3A and 3B. Of course, a facility, such
as a vehicle, is more likely to be able to accommodate a larger
system than would a person. In a preferred embodiment, the system
is implemented as a "patch" attached to a soldier or vehicle.
[0045] FIGS. 6A and 6B show a flow diagram illustrating a method
600 for laser source detection, according to an exemplary
embodiment of the present invention. In 602, the system determines
that an incoming laser has been detected. In 604, the direction of
the incoming laser is determined. In 606, a determination is made
as to whether the incoming laser is from a friend or enemy. If the
incoming laser is from a friend, then the system provides
friendly-party notification, as shown in 608. If the incoming laser
is from an enemy, then at least two options are available.
According to a first option, the source of the incoming laser is
targeted, as shown in 610. According to a second option, as shown
in 612, the system transmits a laser in a plurality of directions
to create a "false reflection." The false reflection may cause an
incoming munition having a laser lock to break its lock and miss
the facility upon which the system is mounted.
[0046] The method 600 may make use of the system described in FIGS.
1-5B or it may make use of a different system. Detection of an
incoming laser (block 602) may be accomplished using practically
any laser detection scheme. Location of the laser source (block
604) may be done using computerized or manual techniques or a
combination of the two. For example, the approach described with
respect to FIGS. 1-5B may be used, in which an array of photodiodes
receive light through an array of lenses and an array of
communicating processors determines the location based on energy
strength.
[0047] Determining whether an incoming laser is from a friend or
enemy (606) is preferably accomplished by examining an optical code
carried by the incoming laser and the wavelength of the laser. For
example, identification may be based on a targeting code used by a
designator. Some typical laser target designator codes include
A-Code laser codes (AGM-114K Hellfire missile) and NATO STANAG No.
3733 codes. The codes specify the PRF (Pulse Repetition Frequency)
of a laser emitter. Lower codes indicate a lower PRF, which allows
for better target designation due to higher emitted power. The
wavelength of the laser may be determined by having different
detectors 310 in the array 200 tuned to be sensitive to different
wavelengths.
[0048] Friendly-party notification (block 608) preferably comprises
transmitting back an identification code (e.g. a combat ID) by
laser. Known signaling techniques may be used, and one or more
lasers may be used for signaling. In alternative embodiments, other
means of providing friendly-party notification may be used, such as
RF transmissions, visible light, or others.
[0049] Reciprocal targeting (block 610) may be performed using
techniques similar to those used by typical laser designators. If
the system of FIGS. 1-5B is used, the lenses overlying the
semiconductor lasers should be translated to provide the desired
intensity of laser light. The laser should be directed toward the
target, as determined in block 604. Obviously, a system having a
faster response time will be better able to provide location
information for reciprocal targeting. Once reciprocal targeting has
been employed, the source target can be targeted by a smart
munition. For example, the laser can be used to guide a beam-riding
munition.
[0050] In a preferred embodiment, false reflection (block 612)
includes using a large number of lasers, such as the array of
VCSELs shown in FIGS. 1-5B, to overwhelm and confuse an incoming
laser-guided munition. Alternatively, and likely less effectively,
a smaller number of lasers can be pulsed in different
directions.
[0051] The blocks shown in FIGS. 6A and 6B may be performed in
orders other than those shown. For example, determining the
direction of an incoming laser (block 604) may be performed after
determining whether the incoming laser is from a friend or enemy
(block 606). Moreover, while a number of post-detection action
sequences have been described, other similar sequences or
combinations of sequences may be employed without departing from
the intended scope of the application.
[0052] Exemplary embodiments of the present invention have been
illustrated and described. It will be understood, however, that
changes and modifications may be made to the invention without
deviating from the spirit and scope of the invention, as defined by
the following claims.
* * * * *