US20080296842A1

US20080296842A1 - Multi-spectral targets for gunnery training

Info

Publication number: US20080296842A1
Application number: US11/543,762
Authority: US
Inventors: Harvey M. Novak; Russell Dominique
Original assignee: FALCON SYSTEMS ENGINEERING Corp
Current assignee: FALCON SYSTEMS ENGINEERING Corp
Priority date: 2005-10-06
Filing date: 2006-10-06
Publication date: 2008-12-04

Abstract

Methods and apparatus for a multi-spectral target apparatus, includes a target having at least one thermal emitting portion, a controller module in communication with a remote user, at least one brightness controller including an input electrically connected to the controller module and at least one output electrically connected to at least one thermal emitting portion of the target. The brightness controller is operable to vary a thermal emitting property of the at least one thermal emitting portion, wherein the at least one thermal emitting portion includes a thermal emitter layer further comprising a resistive layer having a front side and a back side, the resistive layer sandwiched between an electrode layer deposited on the front side and the back side of the resistive layer.

Description

FIELD OF THE INVENTION

The present invention relates generally to gunnery targets. More specifically, the present invention relates to gunnery targets that produce high-fidelity thermal infrared images.

BACKGROUND OF THE INVENTION

It is critical that gunners and sensor operators be well trained to properly identify targets in order to maximize the impact of their weapons on the battlefield while simultaneously avoiding fratricide incidents and civilian casualties. Accordingly, gunnery targets representations of tanks and other vehicles are used for live fire training, sensor testing and observer training.
Modern weaponry includes thermal targeting. In order to provide realistic training, target representations that provide a thermal signature similar to the intended target has become essential. Because destruction by live fire is the result of successful training, inexpensive target surrogates which augment or replace actual vehicles are needed for sensor testing and training of sensor operators.
The Army alone uses a large number of conventional and thermal targets. While actual threat platforms are the best when used for target realism to prove out new weapon and sensor capability, these targets are few in number, are expensive to procure and operate and are difficult to clean up after use due to fuel and fabrication contaminants.
Some of the Department of Defense needs for representations of threat vehicles as targets for live fire training are suicide vehicles, tanks and other armored vehicles, including “Technicals” that usually consists of an automatic weapon mounted on the cab or on the bed of a pickup truck with a human weapon operator and the driver visible.
The Army uses some 3-D surrogate targets, but these are expensive at $10,000 each and are large complicated plastic constructs. Present pop-up gunnery targets include 2-D and 2.5-D (greater than 24″ relief) cutouts with crude large thermal panels that do not provide sufficient temperature gradation and fidelity. The targets are constructed of plywood cutouts with heating elements of various geometric shapes added-on to provide the thermal signature. In most cases, the heating pads are designed to provide the same thermal image all day, regardless of the ambient temperature. Accordingly, the targets lack sufficient fidelity to provide threat-representative visual and thermal signatures.
While a small number of more sophisticated targets exist, use is not widespread. Largely because of cost, availability, and short life expectancy, the majority of the targets continue to be plywood panel outlines of threat vehicles. These are sometimes covered with reverse polarity paper or simple heated panels. Some ranges use charcoal fires to pre-heat targets prior to pop-up. These methods provide marginal thermal signatures that are inadequate for effective training with the newer weapon and targeting sensor technologies. Training on poor representations can lead to confusion when the battlefield image doesn't match the training image.
For the current U.S. arsenal of long range precision guided fire-and-forget weapons systems, day and night time accurate target acquisition is crucial and must be tested and validated against realistic targets 24/7.
Accordingly, gunnery targets that produce high-fidelity thermal infrared images while remaining lightweight, low-cost and able to endure multiple hits without replacement is desirable.

SUMMARY OF THE INVENTION

The present invention provides multi-spectral targets that provide high-fidelity thermal infrared images while remaining lightweight, low-cost and able to endure multiple hits without replacement.
Handheld and aircraft-mounted thermal imagers are used by police, firefighters, search and rescue, border patrol, news organizations and other law enforcement agencies. Dummy vehicles and human representations are useful as training devices for target practice, SWAT, identification, tracking, interception, and search and rescue. Realistic representations of hot spots can be used for training firefighters, safety inspectors and maintenance crews with thermal imagers. Other useful thermal representations are watercraft, aircraft, police dogs and other animals.
One aspect of the disclosed embodiments includes realistic and affordable multi-spectral infrared (3-5 μm and 8-12 μm IR) 2-D, 2.5-D and 3D representations of thermal targets that combine realistic thermal infrared signatures with visual appearance. These targets would support some field repairs to extend target life and allow for future integration of millimeter wave signatures.
Another aspect of an apparatus for a multi-spectral target apparatus, includes a target having at least one thermal emitting portion, a controller module in communication with a remote user, at least one brightness controller including an input electrically connected to the controller module and at least one output electrically connected to at least one thermal emitting portion of the target. The brightness controller is operable to vary a thermal emitting property of the at least one thermal emitting portion, wherein the at least one thermal emitting portion includes a thermal emitter layer further comprising a resistive layer having a front side and a back side, the resistive layer sandwiched between an electrode layer deposited on the front side and the back side of the resistive layer.
Other aspects include at least one processor operable to perform the actions of the above apparatus and method.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout and wherein:

FIG. 1 is a block diagram of a multi-spectral target according to the aspects disclosed herein;

FIG. 2 is a thermal emitter according to the prior art;

FIG. 3A is one aspect of an intrinsic emitter target section according to the multi-spectral target system of FIG. 1; and

FIG. 3B is another aspect of an intrinsic emitter target section according to the multi-spectral target system of FIG. 1.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

An overall system 100 is depicted in FIG. 1 and comprises one embodiment of a multi-spectral gunnery target combining thermal infrared technology with realistic visual appearance. The apparatus and methods disclosed herein may be incorporated to improve the fidelity thermal appearance of 2D and 2.5D (>24″ relief) pop-up gunnery targets, frontal and flank views of humans, vehicles and vehicles with visible humans.
Non-limiting, the system 100 of FIG. 1 comprises a control channel and panel assignments specific for a Technical Vehicle target. Other embodiments may include other targets with other thermal signatures. System 100 comprises the target, i.e., infrared target representation 150, which includes integral thermal infrared emitters; a power section power; and a target heating control system 102 that drives the emitters. The target 150 is physically placed in the line of fire and is expended, while the power and control system 102 is protected in a trench. Not shown are the other range systems that power and control the lifter, rail trolley or battlefield effects.
Because there are several independent mechanisms that generate thermal emissions in a real-life scenario, the target 150 is partitioned into several sections each with an independent temperature control. Some areas with the same heating mechanism are physically separated, such as the tire assemblies 134, 136, and are fabricated as separate sections though they share the same infrared brightness control.
Apparent temperature, as used herein, refers to the temperature as seen by a thermal infrared imager and may be different than the surface temperature as read by thermocouples due to the emissivity and reflectivity of the surface.
The non-human heat sources such as the engine, brakes and lights can be considered constant power sources for a given set of conditions. Constant power sources in thermal equilibrium lose heat to the environment at the same rate they generate heat. The rate of heat loss through conduction is proportional to the temperature difference between the heat source and the environment. The result is a quasi-constant temperature differential above the ambient temperature. The other heat loss mechanisms via convention and radiation complicate the relationship, hence the “quasi” caveat. The general result is that the apparent temperature of these active areas of the target rises and falls with the daily ambient temperature changes and tends to maintain a constant temperature differential or contrast to the surroundings.
On the other hand, human heat sources can be considered constant temperature sources since the body temperature is regulated. As the ambient temperature drops below body temperature, the skin temperature will drop some, but not significantly, and as a result the temperature differential will increase. As the ambient temperature rises to body temperature and above, the temperature differential will decrease as will the thermal infrared contrast to the surrounding environment.
“Active” sections may be controlled to behave as “passive” sections when the scenario calls for the heat generating mechanism to be inactive, such as when simulating a vehicle that has not run for a while. A section may be considered passive if it is just representing the daily heating and cooling cycles due to the environment.
The overall temperature of a section may be operator controlled and corresponds to an infrared brightness control. The infrared brightness variation across the surface of the section is fixed by an emissivity paint pattern in a similar as the variation across the real target is fixed by its paint job and construction. A plurality of brightness control channels are shown to vary the scenario. Some channels control more than one physical section of the target and include:
The “Engine Temperature” channel 118 controls those parts of the target whose apparent temperature increases when the engine is running, such as the truck front quarters 130 and the exhaust system 132. This enables the target to simulate a cold, idling or “hot runner” vehicle.
The “Tire Temperature” channel 120 controls the front and rear tire sections, 134 and 136 respectively, to represent the temperature increase due to tire rolling friction and brake friction for a “hot runner” vehicle.
The “Lights” channel 122 controls the headlight section 138 and tail-light section 140 to represent the heat signature of an operating light. The target may be represented with or without lights on.
The “Window” channel 124 controls the representation of the vehicle cab occupant, such as the driver 142. The heat signature of a person is visible when the window is open but thermal infrared transmission is blocked by the window glass when the window is up. This allows training on either scenario.
The “Gunner” channel 144 controls the apparent temperature of the representation of the human standing in the pickup truck bed. The apparent temperature of the exposed skin will tend to be constant except for some drop in cold and windy conditions.
The “Diurnal Heating/Cooling” or “passive” channel 128 controls the apparent temperature of the representation of those sections of the truck which are not appreciably heated by internal sources, but rather respond to the heating and cooling cycles of the environment, such as the truck body 146.
The “Scenario Control” block 116 accepts commands from a communications module 104 that may in some embodiments comprise a wireless Ethernet link configured to communicate with external systems including the NGATS (New Generation Army Targetry System). Non-limiting, any communication connection or protocol that allows a remote or local user to control the operation of the multi-spectral gunnery target 100 may be utilized.
The scenario control block 116 comprises logic operable to translate a received command into a channel brightness setting, and may include a processor assembly or a plurality of interconnected controller or processor assemblies. Furthermore, each controller may be an application-specific integrated circuit (“ASIC”), or other chipset, processor, logic circuit, or other data processing device. Furthermore, each controller may also include memory, which may comprise volatile and nonvolatile memory such as read-only and/or random-access memory (RAM and ROM), EPROM, EEPROM, flash, or any memory common to computer devices.
Each channel control, e.g., engine temperature channel control 118, contains logic to implement the brightness settings of the connected target section, which in the case of the engine channel temperature channel control 118 is the truck front quarters 130 and exhaust system 132 representations.
Appearance and brightness is controllable and may be adjusted based upon ambient temperature and diurnal cycle temperature variations. Furthermore, system 100 is operable to account for active (heat generated by vehicle operation or human body) and passive (environmentally heated and cooled) components.
The active and passive portions of the targets may be thermal devices that generate emissions in the 3-5 μm and 8-12 μm infrared spectrum and in some aspects the thermal representation range (delta) for active components is 25° C. and 10° C. for passive components.
In one aspect, control of the brightness setting is controlled via pulse width modulation (PWM) of the power supplied to the target sections. For example, full power or brightness may be unmodulated 48VDC supplied to the target section. If the power is modulated to produce a pulse train with a 10% duty cycle, that is, on for 10% of the time, then the target section received only 10% of full power.
The power level delivered to the target section is determined by the desired scenario and calculations which take into account present and past readings of the ambient temperature and environmental conditions in order to mimic diurnal cycles. Note that the target can be set up to deliver a realistic thermal signature for the actual range environment or for a simulated environment or to compensate for non-ideal range conditions (fog, rain, haze, etc).
The power system disclosed herein is configurable. Permanent stationary targets can operate from line power (120 VAC). Moving targets must operate from battery power while moving, but can recharge from line power when docked at the start of the run. Temporary or remote target emplacements require battery power, but must be recharged from a solar panel or generator. In one aspect, system 100 includes a 12 volt battery system 112 that may be recharged from line power by charger 110 or by a solar array 108. The 12 volts may then be boosted with a high-efficiency DC to DC converter 114 to 48 volts to power the thermal emitters. The higher voltage reduces the current and allows higher resistances to be used in the target design. In one exemplary embodiment, battery system 112 includes a 10 Ah, 12 VDC battery that is configured to provide 1200 watts peak with a static power limit of 450 watts for vehicular targets and 150 watts for infantry targets.
The individual target portions of the infrared target representation 150 include intrinsic thermal emitters integral to the target material. The distributed power and heating associated with this implementation provides a high degree of redundancy. Using a small number of controlled sections reduces cost and complexity while allowing thermal signature flexibility, enhanced survivability and target repair.
FIG. 3A illustrates one aspect of a target section 300 that includes a thermal emitter 302 mounted to a lightweight, rigid foam material 308 that adds insulation, rigidity and strength to the target 300.
The thermal emitter layer 302 may be comprised of a conductive polymer sheet 306 with a metal coating 304 on both sides of sheet 306. Sheet 306 is integral to the target section 300 and may be thermoformed in a mold to form sections of a 2.5D target. Non-limiting, other fabricating techniques may be utilized provided the resistivity properties of the thermal emitter layer 302 are maintained.
Accordingly, the thermal generation portion of the target 300 is fabricated as part of the entire target shell rather than as an add-on as shown in the related art of FIG. 2, in which the target shell consists of a plywood shell and a resistive polymer layer is attached to the plywood shell.
Because thermal targeting has become essential part of warfare, it is desirable to manufacture a gunnery target with the thermal signature elements as an intrinsic part of the complete target. The advantages of building the thermal signature as part of the target are ruggedness, redundancy, enhanced fidelity and ease of installation. This enables the generation of a thermal signature for the whole target instead of just hot spots. A resistive heat-generating layer is used across the whole target. The shell is filled (2.5D) or backed (2D) with rigid polymer foam for insulation and strength.
Thermal emitter layer 302 comprises conductive electrode layers 304 deposited on both faces of the resistive layer 306 so that current flows across the thickness D of the resistive layer 306. This method has several advantages over the presently used thermal emitter configuration of FIG. 2 that uses widely spaced electrode stripes with current flowing across the surface of the resistive material. One advantage is that a much lower resistance results because the electrodes 304 are closely spaced and separated only by the thickness D of the resistive film 306. A lower resistance allows a lower voltage DC to be used instead of dangerous AC line voltages to achieve the same power densities.
Low resistivity polymers are not commonly available. Polymers are insulators. A conductive filling of carbon or metal particles is added to get current to flow and too much additive adversely affects the mechanical properties. Accordingly, electrodes 304 being closely spaced, permits higher resistivity materials to be used and therefore allow a wider range of commercial conductive polymer products.
The benefits of this type of arrangement are apparent in that the voltage is applied evenly over the entire resistive layer and thus the only effect of hits on the emitter functioning is at the spot where the projectile goes through; no wires or current paths are disrupted in the rest of the target. Redundant wires 316 connected to the electrode layers 304 may be placed at multiple locations around the edge of the target to ensure that the current cannot be interrupted. As a bonus the metallized surfaces of the electrodes layers 304 will provide a radar signature. The conductive plastic can be thermoformed into 2½-D bas-relief shapes with the infrared signature built directly into the target material rather than being a “cosmetic” add-on feature.
The overall target temperature can be raised and lowered as conditions warrant and the target can be divided into active and passive sections that are separately controlled to represent different operating conditions and diurnal heating cycle changes.
At least two methods may be used to vary the infrared image seen across the emitting surface in order to achieve a high-fidelity representation. One is to change the actual emitter surface temperature and the other is to change the apparent temperature. The first is achieved by varying the thickness D of the resistive layer 306 in order to vary the resistance and therefore the heat produced. The second is achieved by varying the emissivity of the emitting surface to produce different apparent temperatures for the same actual surface temperature.
The applied voltage and the polymer sheet's resistance determine the heat produced by the emitter layer 302. The resistance of the layer 306 is determined by the bulk resistivity of the material and the thickness D of the layer (resistance=resistivity×thickness/area). This gives three factors that can be adjusted to determine the power density (watts per unit area) of the target. The power density determines the target temperature and the emissivity coating can be used to fine adjust the apparent temperature pattern viewed by the thermal imager.
In operation, the applied voltage may be varied to adjust overall temperatures as viewing conditions change. The resistivity of the conductive sheet material 306 is determined by the amount of conductive fill material that is added to the polymer and is specified and controlled at manufacture. Varying the thickness of the conductive sheet material across the target will may induce temperature variations across the target. Although the thickness D is usually fixed at the manufacture of the sheet material, modifying the thickness D during fabrication may achieve a variation of the thermal infrared pattern. For example, the use of compression molding, a technique that utilizes two opposing mold surfaces, may be used to produce a controlled thickness pattern.
Several conductive polymer products comprising the requisite range of resistivity and have thermoplastic properties for thermoforming into 2.5D target shells include, but is not limited to: HMS-1000C, Tivar 1000 CN, Propylux CN, Kydex GND, and Lennite CN.
These polymer products are available with sheet resistivities in the range of 10³to 10⁶ohms/square. Such high resistivities may not work with widely spaced electrodes because a high voltage would be required to get enough heat produced. Accordingly, in some embodiments, the electrodes are disposed on opposite faces of the sheet; the close electrode spacing allows low voltage DC power to be used.
Note that ohms/square is a valid unit of sheet resistivity. Any size square of sheet material with electrode stripes on 2 opposite edges will have the same resistance as any other size square. Sheet resistivity can be converted to bulk resistivity (ohms-cm) by multiplying the sheet resistivity by the sheet thickness in cm. Bulk resistivity is measured with square or circular electrodes on opposite faces of the material thickness.]
Several methods are available for adding the electrode layers 304 to the resistive polymer sheet 306, including spray painting, electroplating and vacuum deposition methods. Vacuum vapor deposition has been used to form metallized plastic film used as a barrier in the packaging for processed fruits and vegetables, beverages, snack foods, confections, coffee, and tobacco products, as such it is a widely available and economical process. In some embodiments, conductive plastic (Kydex-CN) sheets coated with aluminum via vacuum deposition may be used.
Still referring to FIG. 3A, an emissivity coating 310 may be disposed on a front surface 312 of the electrode layer 304. Without the emissivity coating 310 the otherwise visible aluminum electrode coating 304 may present a very low emissivity and high reflectivity surface to a thermal imager targeting the device. The resulting apparent temperature would mostly reflect the temperature of the surroundings or the sky rather than the emitter temperature.
In some embodiments, the emissivity coating 310 may be applied directly to the front surface 312 of the metallic electrode layer 304 of the emitter 302. In other embodiments, such as the multi-spectral target of FIG. 3B, the emissivity coating 310 may be printed on the underside of a thin top layer 314, such as polyethylene, allowing the thin film 310 to be run through processes similar to printing on paper. Polyethylene film is relatively transparent to thermal infrared radiation.
The emissivity coating 310 may be a high-emissivity ink or paint that is applied in a half-tone printing process to achieve fine gradations of emissivity variation across the target. The emissivity coated layer 314 may then be aligned and laminated to the front-side metallization layer 312, sealing the coating 310 under the plastic film 314 that may also function to add some front insulation to the target section 400.
Several known techniques are available for manufacturing the target sections. The most economical and feasible manufacturing process for making the emitter layer 302 is reverse draw thermoforming. In this technique the sheet material 306 is heated to the sag point and then blown away from the mold to stretch the material. When the “bubble” is the correct size, the pressure stops and a plug presses on the material to force it back into the mold. The thickness of the material is fixed as it comes in contact with the plug. The plug is 10 to 20 percent smaller in length and width than the female cavity. This forming technique provides the most uniform part thickness.
A 24″ deep draw on these parts was considered large. In general, the smaller the draw, the more uniform the wall thickness.
A flange needed to clamp and seal the sheet during forming will be about 4″-5″ wide. Therefore, the usable part length or width will be 8″-10″ less then the sheet size.
A sheet thickness of at least 0.125 inch is recommended for deep draw parts. Sheet material of 0.06 inches thick may be used on shallow draw parts. The approximate weight of a 0.125 inch thick, 4′×8′ Kydex sheet is 24 lbs. The actual part weight will be less than this and the material will be thinner after forming.
In addition, the target panels 300, 400 may include a support structure, not shown, to provide rigidity and may be positioned at each panel section joint. Fiberglass angles or channels are lightweight and may provide a flat surface for mounting. The thermoformed sheets may be permanently attached to the fiberglass components using push-in, plastics clips and panel sections may be temporarily fastened together using fasteners designed for more temporary use.
The back side of the panels comprising emitter layer 302 are preferably insulated with a material 308 to prevent heat loss and to increase the panel stiffness. In some embodiments, difficulty may be experienced in insulating thermoformed sheets using foam spray due to the high exothermic temperatures that fast curing polymers generate. One alternative may include an open cavity rigid polyurethane foam 308.
In other embodiments, insulating material 308 may comprise a flexible foam bonded to the thermoformed sheets 302. Because the flexible foam does not provide any structural reinforcement, additional mid-panel stiffness may be provided by adding fiberglass supports.
Although thermoforming is one technique for fabricating the target sections 302, in other embodiments, vacuum forming or reverse draw thermoforming of the target sections may be employed. However, because the mold is applied to only one surface of the plastic 306 it may not produce the variance in emitter layer thickness in order to generate a desired thermal pattern. The use of vacuum forming may require the emissivity pattern 310 alone to generate the desired thermal pattern.
In other embodiments, varying the thickness of the emitter layer 302 may be accomplished using compression molding. Compression molding was originally developed to manufacture composite parts for metal replacement applications. Compression molding is mostly used to make larger flat or moderately curved parts such as hoods, fenders, scoops, spoilers, lift gates and the like for automotive end-uses.
With compression molding there is a molding surface or tool on both sides of the plastic material that press the softened material into the desired shape and thickness. Formation of the emitter layer 302 using compression molding may produce the desired varying thickness if the distance between the two halves of the mold is not a uniform.
As described above, several techniques are currently available for forming the target sections. Deep relief vacuum thermoforming may result in uneven thinning of the material. Thickness uniformity can be maintained with reverse draw thermoforming or a desired thickness variation may be formed using compression molding.
Hit resilience depends upon the target material properties. The goal is to localize the damage to an area not much larger than the diameter of the projectile. The material should offer little resistance to the projectile; it should shear at the point of impact but not shatter, fracture or deform. A clean shear means less energy is transferred to the target from the projectile which means that less strain is placed on the rest of the target and its attachment points.
Plastic sheets comprising the sandwiched layer 306 may be used to provide hit resilience. Various plastics may be used, including but not limited to Propylux-SD, Absylux, Zelux-SD and Kydex-GND. Propylux-SD is static-dissipative polypropylene. Absylux-SD is static-dissipative ABS (acrylonitrile-butadiene-styrene). Zelux is static-dissipative polycarbonate. Kydex-GND is a conductive Acrylic-PVC alloy. Plastics labeled static-dissipative have a higher resistivity than plastics labeled conductive. Kydex and Zelux may be preferred for target construction based upon the results of the bullet impact testing with Kydex performing better, that is, the damage being limited to the immediate area of the hit without shattering, crumbling, cracking, splitting or deformation effects very far beyond the radius of the round.
In other embodiments, a target 150 may comprise high-power panels for the active regions and lower-power panels for the passive regions. The target may be divided into sections when considering size limits for the materials and size limits for the manufacturing processes.
A commercially available conductive polymer such as Kydex may used as an alternative to an expensive custom material. The sheets may be 125-mil or -60 mil thick for example. Using the thicker sheet material allows for less critical processing tolerances than for thinner film material. In order to achieve a target with 2.5-D relief, the sheets may be thermoformed against a mold. Unequal pressure (compression molding) may be used to selectively thin out the material as much as 50% to create up to twice the delta temperature (above ambient) in the thinned regions than in the un-thinned. The molded shell may then be metallized on both sides, for example, with aluminum via vapor deposition. As disclosed above the target shell 302 may then be back-filled with rigid foam 308. An emissivity pattern 310 may then be applied to the face of the target 314 to achieve a finer apparent temperature rendition.
The thickness variation plus the emissivity pattern 310 provide the high-fidelity apparent temperature variations across a panel 300. The applied voltage controls the overall panel temperature.
Panels 300, 400 may be powered with up to 48 VDC, selectable by a user. The variable power supply voltages for the various sections may be generated from a power source available on the gunnery range. In some embodiments the power source is AC line power for stationary targets and 12 VDC for mobile targets, as part of the thermal target power and control system.
The thermal target power and control system 102 allows an operator to control the overall “brightness” of the target 150 as necessary to compensate for or to simulate viewing conditions. If separate emitter panels are used for active and passive target regions, then each will have overall “brightness” control to further adjust the scenario to simulate diurnal variation and vehicle operational conditions. A fast target warm-up mode will overdrive the thermal emitters for a short time to quickly ramp up the temperature and then drop to the temperature maintenance power level shortly before pop-up. The target thermal emitters may remain powered-off when the target is lowered.
One implementation of the intrinsic emitter 302 disclosed above is incorporated in the design of gunnery targets with thermal representations of humans associated with a target vehicle, hereafter referred to as the “Technical.”
For example, the warlord forces in Somalia and Afghanistan have used the Technical. Because the Technical is not a fixed configuration but can vary in vehicle model, gun type and mounting location, the multi-spectral gunnery target representation of the Technical described herein is non-limiting.
Thermal infrared images and measurements were made of a pickup truck with posed humans to represent a Technical in order to acquire an example of the thermal signature as an aid for target design. The temperature distribution measurements are used for designing prototypes and for calculating thermal and electrical power requirements. The white-hot images were taken with the FLIR ThermaCam model S65 (320×240 pixels, 7.5-1311m, FPA uncooled bolometer) and the temperatures were extracted using the FLIR ThermaView software.
Table 1 comprises measurements compiled from the thermal images. A shaded grassy wooded area was taken as representing the ambient temperature. The delta temperatures were computed from the ambient.

TABLE 1

“Technical” Thermal Infrared Temperature Measurements

Feature	Measurements, ° F.	Avg ° F.	Δ ° F.

Exhaust system,	169	169	120.1
center under truck
Tailpipe	98.6	98.6	49.7
Taillight	97.9	97.9	49
Front wheel well	84.1	84.1	35.2
Hood	79.1	79.1	30.2
Gunner's head	78.4, 72.6, 78.9, 78.5	77.1	28
(right side, rear,
left side, front)
Reflection of truck	76.8	76.8	27.9
underbody on asphalt
Driver's head	74.9, 74.1	74.5	26
(window open)
Gunner's torso	52.0, 60.9, 73.8	62.2	13.3
(clothed, side,
rear, front)
Tire	61.9	61.9	13
Front quarter panel	61.3	61.3	12.4
Front grill	60.3	60.3	11.4
Gunner's leg	55.1, 56.1	55.6	6.7
(clothed, side, rear)
Door	56.3, 52.1	54.2	5.3
Tailgate	54.0	54.0	5.1
Asphalt road	53.2, 54.1	53.7	4.8
Rear window	49.8	49.8	0.9
(reflecting trees)
Ambient	50.5, 48.2, 49.6, 48.9, 47.5	48.9	0
(wooded area)
Windshield	42.7, 51.7	47.2	−1.7
(reflecting sky, trees)
Sky	28.0	28.0	−20.9
Hubcap sky reflection	25.9, 14.3	20.1	−28.8

The hottest parts of the scene are the exhaust system, the front wheel wells and the taillights (not shown). Presumably the headlights would also show hot if turned on. The exhaust system is visible from one side and from the rear (picture not shown) while the front wheel wells are hot on both sides. These hot items are all more than 35° F. (delta 19° C.) above the ambient temperature of 49° F. The hottest spot measured, at 169° F., was on the exhaust system. These hot spots are a small percentage of the target area.
Everything in the scene is at or above the ambient temperature except for the sky (28° F.), the sky reflection off the hubcaps (14° F., 26° F.), and the sky reflected off the windshield (43° F.).
The noticeably warm areas are the front quarter panels, hood, grille, front bumper, tires, and the exposed skin of the humans. Most of the truck body and the gunner's clothed legs are near ambient temperature. The “passive” areas of the truck were about 5° F. above the air temperature as might be expected as the late afternoon (˜5 μm) ambient temperature cooled.
In one embodiment, a 2.5D flank view technical target is about 65″ high and 188″ long with a relief depth of 24 inches. It has a truck area of about 45 square feet and a gunner area of about 7 square feet. The rear of the thin thermal emitting shell may be backfilled with several inches of rigid plastic foam both for insulation and for structural rigidity. In some embodiments, the thin plastic shell and plastic foam insulation filling weigh less than 200 pounds.
The target may be partitioned into modular sections according to system 100 of FIG. 1. Such partitioning may result in reasonable size production molds, each section being small enough to be easily fabricated with sheet thermoforming techniques. Furthermore, breaking a large target up into smaller pieces may facilitate handling, packing, storing and commercial shipping.
The average power level applied to each section can be controlled separately to generate an accurate scenario-dependent thermal infrared signature. Modular sections, such as the human or weapon representation, facilitate customization with alternate representations or alternate attachment points to the Technical vehicle 400. A human gunner and weapon may be positioned facing forward, back or over the cab.
Realistic multi-spectral (3-5 cm and 8-12 μm) 2D, 2.5D and 3D representations that combine thermal infrared technology with realistic visual appearance have many additional uses. Other applications for the thermal signature technology are sniper target training, IFF signature training, sensor testing, observer familiarization, decoys, camouflage and ID marking.
Handheld, vehicle and aircraft mounted thermal imagers are used by police, firefighters, other law enforcement, search and rescue, border patrol, and news organizations. Dummy vehicles and human representations are useful for as training devices for target practice, SWAT, identification, tracking, interception, search and rescue. Realistic representations of hot spots in buildings and equipment can be used for training firefighters, safety inspectors and maintenance crews who use thermal imagers. Other useful thermal representations are watercraft, aircraft, dogs and other animals.
While the foregoing disclosure shows illustrative aspects and/or embodiments, it should be noted that various changes and modifications could be made herein without departing from the scope of the described aspects and/or embodiments as defined by the appended claims. Furthermore, although elements of the described embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or embodiment may be utilized with all or a portion of any other aspect and/or embodiment, unless stated otherwise.
Furthermore, although the various illustrative logics, logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented as a plurality of computing devices. Other implementations may comprise more or less computing devices that may include a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a state machine, a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein.

Claims

1. A multi-spectral target apparatus, comprising:

a target comprising at least one thermal emitting portion;

a controller module in communication with a remote user;

at least one brightness controller including an input electrically connected to the controller module and at least one output electrically connected to at least one thermal emitting portion of the target and operable to vary a thermal emitting property of the at least one thermal emitting portion;

wherein the at least one thermal emitting portion includes:

a thermal emitter layer further comprising a resistive layer having a front side and a back side, the resistive layer sandwiched between an electrode layer deposited on the front side and the back side of the resistive layer.

2. The apparatus of claim 1, wherein the electrode layer deposited on the front side of the resistive layer includes an emissivity coating comprising an emissivity property disposed on a front side of the electrode layer.

3. The apparatus of claim 2, wherein the emissivity coating is applied in a half-tone printing process.

4. The apparatus of claim 1, wherein the thermal emitting layer further comprises a top layer aligned and attached to a front side of the electrode layer deposited on the front side of the resistive layer, a coating comprising an emissivity property disposed on an underside of the top layer.

5. The apparatus of claim 1, wherein the thermal emitting layer further comprises at least one electrical conducting wire attached to each electrode layer, the thermal emitting layer configured to pass a current from one electrode layer to the other electrode layer.

6. The apparatus of claim 1, wherein the resistive layer comprises a resistivity between 10³and 10⁶ohms/square.

7. The apparatus of claim 1, wherein the resistive layer is at least 0.125 inch.

8. A method of varying thermal emissivity of a target including a resistive layer sandwiched between a pair of electrodes, comprises at least one of varying an emitter surface temperature and varying an apparent temperature of the target.

9. The method of claim 8, wherein varying the emitter surface temperature includes varying a thickness D of the resistive layer.

10. The method of claim 8, wherein varying the emitter surface temperature includes passing a current between the pair of electrodes.

11. The method of claim 8, including varying a supply of electric power to the target.

12. A thermal emitter layer comprising a resistive layer having a front side and a back side, the resistive layer sandwiched between an electrode layer deposited on the front side and the back side of the resistive layer.