Camouflage system with adaptive IR signature

Abstract

The present invention relates to camouflage system (1) for camouflaging a vehicle (3), comprising a low-emissive camouflage material (5) for passively reducing an apparent temperature of at least a first thermal area (A) of the camouflage system to a temperature below an apparent temperature of the surroundings of the vehicle (3), an infrared sensor arrangement (7) for measuring the apparent temperature of the surroundings of the vehicle in at least a first measurement zone (9), which first measurement zone (9) is associated with the first thermal area (A), and a controllable heat generating arrangement (11) for heating the first thermal area (A) of the camouflage system (1). The camouflage system (1) further comprises a control unit (13) configured to determine a target temperature for the first thermal area (A) based on at least the apparent temperature of the surroundings of the vehicle (3) in the first measurements zone (9), and to control the heat generating arrangement (11) to heat the first thermal area (A) to the target temperature.

Description

[0001] Camouflage System with Adaptive IR Signature

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a camouflage system for camouflaging a vehicle and, in particular, to a camouflage system comprising means for adapting the thermal signature of the vehicle to the surrounding environment.

[0004] BACKGROUND ART

[0005] The primary objective of camouflage materials is to disrupt the electromagnetic footprint of an object, harmonizing its signature with the surrounding environment to elude detection by human observers and various sensor systems across the electromagnetic spectrum.

[0006] Camouflage systems generally fall into two categories: static, designed for concealing immobile objects, and mobile, tailored for vehicles and other moving targets.

[0007] Adapting the electromagnetic profile of vehicles to blend seamlessly with their surroundings poses distinct challenges. Dynamic factors such as shifts in the environment during vehicle movement and fluctuations in heat emitted by mechanical or electrical components can complicate this process. Furthermore, achieving effective thermal camouflage is hindered by the variability of the surroundings across different perspectives and the uneven distribution of heat across the vehicle's surface, influenced by factors like engine operation.

[0008] There is thus a need for improvements within the field of mobile camouflage systems.

[0009] SUMMARY OF THE INVENTION

[0010] It is an object of the present disclosure to address one or more challenges associated with mobile camouflage systems according to the prior art.

[0011] It is a particular object of the disclosure to provide a mobile camouflage system enabling the thermal signature of a camouflaged object to be adapted to the changes or local variations in the surrounding environment. This and other objects, which will become apparent in view of the description following hereinafter, are achieved according to a camouflage system as defined by the appended claims. According to one aspect of the present disclosure, there is provided a camouflage system for camouflaging a vehicle, comprising a low-emissive camouflage material for passively reducing an apparent temperature of at least a first thermal area of the camouflage system to a temperature below an apparent temperature of the surroundings of the vehicle; - an infrared (IR) sensor arrangement for measuring the apparent temperature of the surroundings of the vehicle in at least a first measurements zone, which first measurements zone is associated with the first thermal area of the camouflage system; a controllable heat generating arrangement for heating the first thermal area of the camouflage system, and - a control unit configured to determine a target temperature for the first thermal area based on at least the apparent temperature of the surroundings of the vehicle in the first measurements zone, and to control the heat generating arrangement to heat the first thermal area to the target temperature. By passively reducing the apparent temperature of the thermal area of the camouflage system to a temperature below the apparent temperature of the surroundings of the vehicle, and actively heating the thermal area to a temperature selected based on at least the apparent temperature of the surroundings, the apparent thermal signature of the thermal area can be made to match the apparent thermal signature of the surroundings, thereby mitigating the risk of detection of the vehicle by IR sensors and other thermal imaging devices. Thus, the control unit is typically configured to control the heat generating arrangement to heat the first thermal area to a target temperature making the apparent temperature of the first thermal area, as perceived by an IR sensor, match the apparent temperature of the surroundings of the vehicle in the first measurement zone.

[0012] In order to reduce the apparent temperature of at least the first thermal area of the camouflage system to a temperature below the apparent temperature of the surroundings of the vehicle, the emissivity coefficient of the low-emissive camouflage material should preferably be no more than 0.8.

[0013] In some embodiments, the camouflage system comprises at least a first temperature sensor for measuring an actual temperature of the first thermal area of the camouflage system, the control unit being configured to control the heat generating arrangement to heat the first thermal area based on the actual temperature of the first thermal area and the target temperature. By measuring the actual temperature of the thermal area, the heat generating arrangement may be controlled based on a difference between the actual temperature of the thermal area and the target temperature, e.g. by employing closed loop control. For example, the heat generating arrangement may be controlled to minimise a difference between the actual temperature and the target temperature. Furthermore, the difference between the actual temperature and the target temperature may be utilised to trigger an alert if the difference exceeds a threshold value indicating that the apparent thermal signature of the vehicle deviates substantially from an apparent thermal signature of its immediate surroundings.

[0014] In some embodiments, the heat generating arrangement comprises a plurality of heat elements and a heat-conducting layer, such as a metal foil, metal film or metal sheet, arranged in thermal contact with the plurality of heat elements and configured to distribute the heat generated by the plurality of heat elements along the heat-conducting layer. By utilising a plurality of heat elements, such as a plurality of electric heating pads, a versatile and adaptive heating arrangement that can be easily integrated into the camouflage system is provided. By utilising a heat-conducting layer that thermally couples the individual heat elements to each other, a more uniform temperature distribution and reduced temperature gradients across the camouflage system can be obtained, thereby avoiding easily detectable hot-spots in the thermal signature of the vehicle.

[0015] As understood from the above, the proposed camouflage system provides camouflage at least within the thermal infrared (TIR) wavelength region. Typically, the camouflage system is also configured to provide camouflage at least within the visual (VIS) wavelength region.

[0016] In some embodiments, the camouflage system is a multilayer camouflage system configured to provide multispectral camouflage in at least the TIR and VIS wavelength regions, and further in at least one and preferably all wavelength regions selected from the group consisting of the near infrared (NIR) wavelength region, the shortwave infrared (SWIR) wavelength region, and the radar wavelength region.

[0017] In some embodiments, the camouflage system comprises a low-emissive backing for providing camouflage at least within the TIR wavelength region, and an incised garnish for providing camouflage at least within the VIS wavelength region, which garnish is attached to an exterior side of the backing configured to face away from the vehicle during use of the camouflage system, wherein the heat generating arrangement is arranged on an opposite interior side of the backing configured to face the vehicle during use of the camouflage system.

[0018] In some embodiments, the camouflage system further comprises a radar-absorbing layer on the interior side of the low-emissive backing, wherein the heat generating arrangement is arranged between the low-emissive backing and the radar-absorbing layer.

[0019] In some embodiments, the camouflage system comprises an alert system configured to monitor a difference in temperature between the target temperature of first thermal area and an actual temperature of the first thermal area, and to alert an operator of the vehicle when the difference in temperature exceeds a threshold value. This is advantageous in that it allows the operator to take appropriate actions to minimise detection by IR sensors, e.g. by moving the vehicle into a different type of terrain.

[0020] The at least first measurement zone may be a ground zone located on the ground in the surroundings of the vehicle, and the IR sensor arrangement may comprise at least one ground IR sensor arrangement for measuring a temperature in the ground zone. By controlling the temperature of the thermal area based on the temperature of the ground in the surroundings of the vehicle, the thermal signature of the vehicle can be controlled to blend into the background of thermal images captured by elevated IR sensors, such as airborne IR sensors carried by aircraft or drones.

[0021] In some embodiments, the ground IR sensor arrangement may comprise a plurality of ground IR sensors configured to capture temperature readings from different points on the ground in the ground zone, wherein the control unit is configured to determine a target temperature for the first thermal area of the camouflage system based on the temperatures measured by the plurality of ground IR sensors. By using a plurality of temperature readings from different points of the ground zone, the apparent temperature of the ground zone as perceived by a distant IR sensor can be more precisely determined, e.g. by determining an apparent temperature of the ground zone as an average of the plurality of temperature readings. This in turn allows the control unit to determine a target temperature for the first thermal area that results in an apparent temperature of the first thermal area that more precisely matches the apparent temperature of the ground zone.

[0022] In some embodiments, the IR sensor arrangement may comprise a sky IR sensor arrangement for measuring IR radiation emitted by the sky, wherein the control unit is configured to determine the target temperature for the first thermal area based on both the apparent temperature of the surroundings of the vehicle in the first measurement zone and the IR radiation emitted by the sky. Taking the IR radiation emitted by the sky into consideration in the calculation of the target temperature of the first thermal area makes it possible to further minimise the contrast between the first thermal area and the first measurement zone, as perceived by an IR sensor.

[0023] In some embodiments, the IR sensor arrangement comprises a plurality of IR sensors for measuring a temperature of the surroundings of the vehicle in each of a plurality of measurements zones, whereas the heat generating arrangement comprises a plurality of individually controllable heat elements for heating different thermal areas of the camouflage system, wherein each thermal area is associated with a respective measurement zone. The control unit is configured to determine a respective target temperature for each of the plurality of thermal areas based on at least the apparent temperature in its associated measurements zone, and to control the plurality of heat elements to selectively heat the thermal areas such that each thermal area is heated to its target temperature. By selectively heating each of a plurality of thermal areas of the camouflage system based on the apparent temperature of an associated measurement zone, the vehicle can be provided with a non-homogenous thermal signature that is adapted to temperature variations in the surroundings of the vehicle.

[0024] In this scenario, the above-mentioned alert system may be configured to monitor, for each thermal area, a difference between the target temperature of the thermal area and an actual temperature of the thermal area, and to alert an operator of the vehicle when the difference in temperature exceeds a threshold value. The alert system may further be configured to indicate to the operator which part or parts of the vehicle have an apparent thermal signature that deviates from an apparent thermal signature of the immediate surroundings, based on the differences between the target temperatures and the actual temperatures of the thermal areas. This is advantageous in that the operator may be made aware also of local discrepancies between the thermal signature of the vehicle and the thermal signature of the immediate surroundings.

[0025] According to another aspect of the present disclosure, there is provided a vehicle, such as a military vehicle, comprising an MCS that is devised and configured as described above.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above objects, as well as additional objects, features and advantages of the present disclosure, will be more fully appreciated by reference to the following illustrative and non- limiting detailed description of example embodiments of the present disclosure, when taken in conjunction with the accompanying drawings, of which:

[0028] Fig. 1 illustrates a camouflage system according to an exemplary embodiment of the disclosure.

[0029] Fig. 2 illustrates a multi-zone camouflage system according to an exemplary embodiment of the disclosure.

[0030] Fig. 3 illustrates a main battle tank (MBT) equipped with the camouflage system according to an exemplary embodiment of the disclosure.

[0031] Fig. 4 illustrates an exemplary embodiment of a panel-based camouflage system according to an exemplary embodiment of the disclosure.

[0032] Fig. 5 illustrates a camouflage material used in the camouflage system according to an exemplary embodiment of the disclosure.

[0033] Fig. 6 illustrates a camouflage system according to another exemplary embodiment of the disclosure.

[0034] DETAILED DESCRIPTION

[0035] The proposed camouflage system for camouflaging a vehicle will now be described with reference to the accompanying drawings, in which preferred exemplary embodiments of the disclosure are shown. It should be understood, however, that the camouflage system may be embodied also in other forms and the disclosure should not be construed as limited to the exemplary embodiments disclosed herein.

[0036] It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It should be noted that, as used in the specification and the appended claim, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context explicitly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the words "comprising", "including", "containing" and similar wordings does not exclude other elements or steps. Fig. 1 illustrates schematically a camouflage system 1 according to an exemplary embodiment of the present disclosure, when applied to a vehicle 3 to be camouflaged.

[0037] The camouflage system 1 comprises a low-emissive camouflage material 5 for passively reducing the apparent temperature of at least a first thermal area A of the camouflage system 1 to a temperature below an apparent temperature of the surroundings of the vehicle 3. The camouflage system 1 further comprises an IR sensor arrangement 7 for measuring the apparent temperature of the surroundings of the vehicle 3 in at least a first measurement zone 9 associated with the first thermal area A, and a controllable heat generating arrangement 11 for heating the first thermal area A of the camouflage system 1. The camouflage system 1 further comprises a control unit 13 or control computer configured to determine a target temperature for the first thermal area A at least based on the apparent temperature of the surroundings of the vehicle in the first measurement zone 9, and to control the heat generating arrangement 11 to heat the first thermal area A to the target temperature.

[0038] More specifically, the control unit 13 is configured to heat the first thermal area A to a target temperature making the apparent temperature of the thermal area A, as perceived by an I R sensor, match the apparent temperature of the surroundings of the vehicle 3 in the first measurement zone 9.

[0039] The working principle of the proposed camouflage system 1 is hence to passively reduce the apparent thermal signature of the camouflage system and hence the camouflaged vehicle 3 by means of the low-emissive camouflage material 5, and then actively increase the apparent thermal signature to make it match the apparent thermal signature of the surroundings of the vehicle 3 by means of the heat generating arrangement 11.

[0040] The camouflage system 1 may comprise at least a first temperature sensor 15 for measuring an actual temperature of the first thermal area A of the camouflage system, whereby the control unit 13 may use the actual temperature measurement for closed loop control of the temperature of the thermal area A. For example, the control unit 13 may be configured to control the heat generating arrangement 11 to heat the first thermal area A based on a difference between the target temperature and the actual temperature of the first thermal area A. This means that the control unit 13 may be configured to control the heat generating arrangement 11 to heat the first thermal area A based on at least an actual temperature of the first thermal area A and the apparent temperature of the surroundings of the vehicle 3 in the first measurement zone 9. The apparent temperature of an object is the temperature of the object as perceived by an I R sensor based on the thermal radiation received by the IR sensor from the object. This temperature may not always represent the true physical temperature of the object, as it can be influenced by factors such as the object's emissivity, environmental conditions, and the presence of interfering radiation. The apparent temperature of the at least first thermal area A is thus the temperature perceived by an I R sensor directed towards the first thermal area A, and the apparent temperature of the surroundings of the vehicle 3 in the first measurement zone 9 is the temperature perceived by an I R sensor directed towards the first measurement zone 9 of the surroundings of the vehicle 3.

[0041] That the low-emissive camouflage material 5 passively reduces the apparent temperature of the first thermal area A to a temperature below the apparent temperature of the surroundings of the vehicle 3 means that the material 5 is designed and treated to exhibit a thermal signature that appears colder than the surrounding environment, as perceived by an I R sensor, without using any active signal-emitting components. This is achieved by designing the camouflage material 5 to exhibit a relatively low emissivity as compared to the emissivity of typical objects in the surroundings of the vehicle. The camouflage system 1 is particularly intended for vehicles operating in high-emissivity terrain, where objects and vegetation in the surroundings of the vehicle 3 typically exhibit an emissivity coefficient above 0.8. The relatively lower emissivity of the camouflage material 5 makes the camouflage material 5 reflect more IR radiation emitted by the cold sky than objects in the surroundings of the vehicle, thereby reducing the apparent temperature of the camouflage material 5 to a temperature below the temperature of surrounding objects, even in situations where the actual temperature of the camouflage material 5 is higher than the temperature of the surrounding objects. There may, however, be situations where the low-emissive camouflage material 5 is incapable of reducing the apparent thermal signature of the vehicle 3 to a temperature below the apparent temperature of the surroundings of the vehicle. For example, this may be the case when the vehicle is operating in cloudy conditions where a thick layer of clouds prevents the cold IR radiation emitted by the sky from reaching and being reflected by the low-emissive camouflage material 5. Therefore, that the camouflage material 5 is able to passively reduce the thermal signature of the vehicle 3 to a temperature below an apparent temperature of the surroundings of the vehicle 3 herein means that it is capable of doing so at least in most weather conditions in woodland terrain. To achieve this, the low-emissive camouflage material 5 is typically designed and configured to have an emissivity coefficient of at most 0.8. In the context of camouflage materials, and as used in the present disclosure, a camouflage material exhibiting an emissivity coefficient of 0.8 or less is considered a low-emissivity camouflage material. This is in contrast to high-emissivity materials typically exhibiting an emissivity coefficient above 0.8. Typically, the emissivity coefficient of the camouflage material 5 is in the range of 0.4-0.8, and preferably in the range of 0.5-0.7. The exact emissivity coefficient of the low-emissive camouflage material 5 may vary depending on the specific material, its composition, and surface treatment, and may be adapted to the intended use and operating conditions of the camouflage system 1. A nonlimiting example of a suitable composition of the low-emissive camouflage material 5 will be described below with reference to Fig. 5.

[0042] In the illustrated example, the IR sensor arrangement 7 comprises a single IR sensor, such as an IR camera, for measuring the temperature of the surroundings in the first measurement zone 9. However, it should be appreciated that the IR sensor arrangement 7 may comprise multiple IR sensors for measuring the temperature at different locations in the measurements zone 9, whereby an average temperature of the measurement zone 9 may be calculated by the control unit 13 based on the temperatures measured by the multiple IR sensors. Likewise, the camouflage system 1 may comprise a plurality of temperature sensors 15 for measuring the temperature of the first thermal area A, whereby the control unit 13 may calculate and use an average value of the temperature readings as the actual temperature of the first thermal area A.

[0043] The heat generating arrangement 11 for heating the at least first thermal area A may comprise one or more individual heat elements. In this exemplary embodiment, the heat generating arrangement 11 comprises a plurality of heat elements 11’-11” and a heat-conducting layer 17 arranged in thermal contact with the plurality of heat elements 11’-11 ” for distributing the heat generated by the heat elements along the heat-conducting layer 17. The heat generating arrangement 11 may be configured to heat the thermal area A by applying heat directly onto low-emissive camouflage material 5 and / or by applying heat to parts of the vehicle 3 underlying the thermal area A. The heat elements 1 T, 11” may be any suitable type of heat elements, such as heat pads, a mesh of resistive wires, etc. In some embodiments, the heat elements 11’, 11” and / or the heat-conducting layer 17 may be embedded into the camouflage material 5 to form a single, integral camouflage material with an integrated heat generating arrangement. The first measurement zone 9 may be any zone exterior to the vehicle 3 having an apparent thermal signature that is to be mimicked by the thermal area A of the camouflage system 1. The location and / or extensional direction of the first measurement zone 9 in relation to the location and / or extensional direction of the first thermal area A may be adapted in relation to an assumed position of an IR sensor-equipped threat. Typically, to avoid detection from elevated IR sensors, the first measurement zone 9 is a ground zone, meaning that the first IR sensor arrangement 7 is directed downwards to capture temperature readings from the ground in the vicinity of the vehicle 3. Typically but not necessarily, the first measurement zone 9 is located exterior to the side of the vehicle 3 on which the first thermal area A is located. As best understood by studying Fig. 2, this allows the thermal signature of the vehicle 3 to blend into the thermal signature of the ground, as perceived by an elevated IR sensor, such as an I R sensor of an aircraft or a drone.

[0044] In other embodiments, it is contemplated the first measurement zone 9 may be located exterior to a side of the vehicle 3 which is opposite to the side of the vehicle on which the first thermal area 3 is located. This may for example be advantageous to avoid detection by ground-based IR sensors since this allows the thermal signature of the “background” of the vehicle to be mimicked by a thermal area on the side of the vehicle 3 facing the ground-based IR sensor.

[0045] The first measurement zone 9 typically corresponds to the field of view of the IR sensor arrangement 7, and the apparent temperature of the surroundings of the vehicle 3 in the first measurement zone 9 typically corresponds to an apparent average temperature of objects (surfaces) located within the field of view of the IR sensor arrangement 7. For example, the IR sensor arrangement 7 may be configured to detect the IR radiation emitted by all surfaces within its field of view, and to determine the apparent temperature of the surroundings of the vehicle 3 in the first measurement zone 9 based on an average of the total radiation detected.

[0046] The camouflage system 1 may further comprise a sky IR sensor arrangement 7’ for measuring IR radiation emitted by the sky. The measurement zone of the sky IR sensor arrangement 7’ hence constitutes a sky zone, denoted by reference numeral 9’ in Fig. 1. The control unit 13 may be configured to determine the target temperature for the first thermal area A based on both the apparent temperature of the surroundings in the first measurement zone 9 and the IR radiation emitted by the sky, as measured by the sky IR sensor arrangement 7’. This is advantageous in that IR radiation from the cold sky, reflected by the low-emissive camouflage material 5 of the camouflage system 1 , can be compensated for by the control unit 13 in the determination of the target temperature for the first thermal area A. As discussed above, reflected IR radiation from the cold sky can lower the apparent temperature of the first thermal area A, thereby making the apparent temperature of the first thermal area A colder than the apparent thermal signature of the surrounding environment. By measuring the IR radiation of the sky and determining an apparent temperature of the sky based on the measured IR radiation, the effect of cold sky reflection can be compensated for in the determination of the target temperature of the first thermal area A.

[0047] The control unit 13 or control computer of the camouflage system 1 may be any type of electronic device capable of controlling the heat generating arrangement 11 based on received temperature-related data. For example, the control unit 13 may be embodied in the form of a microprocessor. The control unit 13 may be an internal computer of the vehicle 3, or it may be an external computer not normally forming part of the vehicle 3. In embodiments where the control unit 13 is an external computer, the control unit 13 may be mounted in or on the vehicle 3, or embedded into the other components of the camouflage system 1 , upon application of the camouflage system 1 onto the vehicle 3.

[0048] The camouflage system 1 may further comprise an alert system configured to monitor a difference in temperature between the target temperature of the first thermal area A and an actual temperature of the first thermal area, e.g. as measured by the temperature sensor arrangement 15, and to alert an operator of the vehicle 3 when the difference in temperature exceeds a threshold value. The alert system typically comprises at least one display 18, coupled to the control unit 13 of the camouflage system. The display 18 is intended for use by an operator of the vehicle and may e.g. be an onboard display of the vehicle 3 or a headmounted display (HMD) of a crewmember of the vehicle. As described above, the control unit 13 may be configured to calculate a target temperature for the first thermal area A based on the surrounding temperature in the first measurement zone 9 and, optionally, the IR radiation emitted by the sky. When the actual temperature of the thermal area A deviates substantially from the calculated target temperature, the control unit 13 triggers an alarm signal that causes display of an alert on the display 18, informing the operator of the detected deviation in temperature.

[0049] Fig. 2 is a top view of a vehicle 3 equipped with a multi-zone camouflage system 1 according to an exemplary embodiment of the present disclosure. The multi-zone camouflage system 1 comprises a plurality of thermal areas A1-A8, where each thermal area is devised and configured in accordance with the thermal area A in Fig. 1. The multi-zone camouflage system 1 is applied to substantially all visible exterior parts of the vehicle 3, meaning that the low- emissive camouflage material 5 (see Fig. 1) of the camouflage system 1 covers substantially all visible exterior surfaces of the vehicle 3. The multi-zone camouflage system 1 includes an IR sensor arrangement comprising a plurality of IR sensors 7A-7H for measuring a temperature of the surroundings of the vehicle 3 in each of a plurality of measurements zones 9A-9H, and a heat generating arrangement (not shown) comprising a plurality of individually controllable heat elements for heating the different thermal areas A1-A8 of the camouflage system. Each thermal area A1-A8 is associated with a respective measurement zone 9A-9H, and the control unit (not shown) of the multi-zone camouflage system 1 is configured to determine a respective target temperature for each of the plurality of thermal areas A1-A8 based on at least the surrounding temperature in its associated measurements zone, and to control the plurality of heat elements to selectively heat the thermal areas A1-A8 such that each thermal area is heated to its target temperature.

[0050] The number and locations of the thermal areas A1-A8 may vary but are typically chosen in dependence of the number and locations of the measurements zones 9A-9H covered by the IR sensors 7A-7H of the camouflage system 1. In this example, the camouflage system 1 is divided into eight sectors of a circle having its origin at a centre point of the vehicle 3, where each circle sector constitutes a respective thermal area. As illustrated in the drawing, a thermal area must hence not consist of a single continuous surface but may comprise multiple and differently oriented surfaces of the camouflage system 1. If the multi-zone camouflage system 1 is a panel-based camouflage system, as will be further described below with reference to Fig. 4, a thermal area may consist of one or more panels of the camouflage system, and / or parts of one or more panels.

[0051] The configuration and position on the vehicle 3 of the plurality of IR sensors 7A-7H may also vary. Although illustrated as being mounted near the outer boundary of the vehicle 3 when looking at it from a top-down perspective, it should be realized that it may be advantageous to mount the IR sensors 7A-7H further from the outer boundary of the vehicle 3 in order to better protect the sensors from impacts and shocks. For example, the plurality of IR sensors 7A-7H may be substantially colocated at an elevated and substantially central position in relation to the vehicle body, for example in a sensor tower protruding substantially vertically from an upper side of the vehicle body.

[0052] By selectively heating the plurality of thermal areas A1-A8 based on the temperature of the their associated measurements zones 9A-9H, the control unit of the multi-zone camouflage system 1 can provide the vehicle 3 with a non-homogenous thermal signature that matches a non-homogenous thermal signature of the surrounding environment. In a multi-zone camouflage system, the above-mentioned alert system may be configured not only to alert the operator when any of the thermal areas A1-A8 deviates in temperature from its determined target temperature, but also to indicate what part or parts of the vehicle that has a thermal signature that currently does not match its immediate surroundings. To this end, the alert system may be configured to monitor, for each individual thermal area A1-A8, a difference between the target temperature of the thermal area and an actual temperature of the thermal area, and to alert an operator of the vehicle when the difference in temperature exceeds a threshold value. The alert system may further be configured to indicate to the operator which part or parts of the vehicle have a thermal signature that deviates from a thermal signature of the immediate surroundings, based on the differences between the target temperatures and the actual temperatures of the thermal areas. For example, the control unit 13 may be configured to cause display of a stylistic picture of the vehicle 3 on the monitor 18, which picture indicates areas of the vehicle covered by a thermal area whose actual temperature deviates substantially from its target temperature. This way, the operator is notified about local deficiencies in the thermal camouflage of the vehicle 3, allowing the operator to take appropriate actions.

[0053] Figs. 3 and 4 illustrate an exemplary embodiment of the camouflage system 1 according to the present disclosure. Fig. 3 illustrates a perspective view of a vehicle 3 with the camouflage system 1 mounted thereon, while Fig. 4 illustrates parts of the camouflage system 1 when dismounted from the vehicle 3.

[0054] As is clear from the present disclosure, the camouflage system 1 is particularly intended for camouflaging vehicles or other movable platforms. Such camouflage systems are sometimes referred to as mobile camouflage systems (MCS). In particular, the camouflage system 1 is intended for camouflaging military vehicles, such as armour-plated ground vehicles. However, although particularly intended for camouflaging movable platforms it should be appreciated that the camouflage system of the present disclosure could be used for camouflaging any type of objects, including stationary objects.

[0055] In the specific example illustrated in Figs. 3 and 4, the camouflage system 1 is configured for use with a main battle tank (MBT).

[0056] As illustrated by Fig. 4, the camouflage system 1 may be a modular or panel based camouflage system comprising a plurality of panels 2, together constituting the camouflage system. The panels 2 of the camouflage system 1 may be designed according to the requirements of the specific vehicle or platform for which it is intended, in order to obtain optimal camouflage performance without affecting the functionality, handling or performance of the vehicle or platform.

[0057] Although constituted by a plurality of individual camouflage panels 2 in the illustrated embodiment, it should be appreciated that the disclosure is not limited to a panel-based camouflage systems and that the camouflage system 1 could as well be manufactured as one substantially continuous camouflage construction that is applied to the vehicle in one or only a few separate pieces. However, the panel-based design is advantageous in that it becomes easier to adapt the camouflage system to the features and the exterior surfaces of the vehicle 3, and to securely attach the camouflage system to the vehicle 3.

[0058] As mentioned above, the camouflage system 1 is configured to cover substantially the whole visible exterior area of the vehicle 3, or at least the total passive, visible exterior area of the vehicle 3. The passive, visible exterior area of the vehicle 3 is the exterior vehicle area that is visible during normal operation of the vehicle and which does not comprise features that cannot be covered by camouflage without jeopardizing vehicle operation or performance, such as wheels, tracks, lookouts, weapon muzzles, external sensors, etc.

[0059] The panels 2 may be securely but removably attached to the vehicle to allow the camouflage system 1 to be subsequently dismounted from the vehicle 3, should that be desired. Each panel 2 may be individually attached to the vehicle 3, whereafter adjacent panels may be attached to each other for a more robust camouflage construction.

[0060] The panels 3 are preferably attached to the vehicle by means of releasable attachment means, such as hook-and-loop fasteners, releasable adhesive, bayonet coupling mechanisms, magnets, or the like. Instead or in addition to such releasable attachment means, existing attachment means of the vehicle may be utilized to attach the panels 2 to the vehicle 3. For example, armour-plates are often bolted to the vehicle body of military vehicles. Such armourbolts may protrude from the exterior surface of the vehicle and be used as releasable attachment means for the attachment of the panels 2. Any of the above mentioned examples of releasable attachment means may also be used to attach the panels 2 to each other. In some embodiments, the panels 2 may be attached to the vehicle 3 and to each other by means of hook-and-loop fasteners.

[0061] Typically, the camouflage system 1 is a multispectral camouflage system configured to provide multispectral camouflage to the vehicle. Multispectral camouflage herein means camouflage within at least two wavelength regions selected from the group consisting of the visual (VIS) wavelength region, the near infrared (NIR) wavelength region, the shortwave infrared (SWIR) wavelength region, the thermal infrared (TIR) wavelength region, and the radar wavelength region. That the camouflage system 1 is configured to “provide camouflage to the vehicle” means that the camouflage system 1 is configured to adapt the electromagnetic signature of the camouflaged vehicle in a way that makes the vehicle more difficult to detect visually and / or by means of electromagnetic sensors operative in the relevant wavelength region. Typically, this is achieved for all relevant wavelength regions by adapting the electromagnetic signature of the vehicle to the electromagnetic signature of the surroundings in which the vehicle is intended to operate.

[0062] The camouflage system 1 of the present disclosure is configured to provide camouflage at least within the TIR wavelength region. As described above with reference to Figs. 1-2, this is achieved by passively reducing the apparent thermal signature of the vehicle 3 to a temperature below an apparent temperature of the surrounding environment through the use of a low-emissivitet camouflage material, and then heating one or more thermal areas of the camouflage system 1 to a temperature that makes the apparent thermal signature of the vehicle 3 match the apparent thermal signature of the surrounding environment, as perceived by an I R sensor.

[0063] Typically, the camouflage system 1 is configured to provide camouflage within both the TIR and the VIS wavelength regions. Preferably, the camouflage system 1 is configured to provide camouflage also within the NIR and SWIR wavelength regions. Effective camouflage within the VIS, NIR and SWIR wavelength regions may be achieved by providing the low-emissive camouflage material 5 of the camouflage system 1 with colour schemes, NIR and SWIR values and surface structures that causes the camouflage system 1 to visually blend into the surrounding environment. Additionally, the camouflage system 1 may comprise contour disrupters that may be applied to conspicuous parts of the vehicle to blur the contours of the vehicle 3. Thus, the camouflage system 1 is preferably configured to provide camouflage within all wavelength regions of the electro-optical spectrum, including the VIS, NIR, SWIR and TIR wavelength regions.

[0064] Additionally, the camouflage system 1 may also be configured to provide camouflage within the radar wavelength region. More specifically, the radar characteristics of the camouflage system 1 may be adapted to provide protection against radar reconnaissance and homing missiles in the frequency range of 1-100 GHz. This may be achieved by adding a layer of radar-absorbing material underneath the low-emissive camouflage material 5, as will be further discussed with reference to Fig. 6 below. That the camouflage system 1 is configured to provide camouflage within a specific wavelength region herein means that the camouflage system is configured to provide camouflage within at least parts of that specific wavelength region. As well known in the art, nomenclature and definitions of wavelength regions or sub-spectra of the electromagnetic spectrum may vary. For the purpose of this disclosure, the following nomenclature and definitions will be used:

[0065] Name of wavelength region Wavelength region

[0066] VIS 400 nm - 750 nm

[0067] NIR 750 nm - 1500 nm

[0068] SWIR 1500 nm - 3 pm

[0069] TIR 3 pm - 12 pm

[0070] (MWIR) (3 pm - 5 pm)

[0071] (LWIR) (8 pm - 12 pm)

[0072] Radar 1 mm - 100 m, where MWIR (mid-wavelength infrared) and LWIR (long-wavelength infrared) are sub-bands within the TIR wavelength region.

[0073] In order to provide the desired multi-spectral camouflage capabilities within the electro-optical spectrum, the low-emissive camouflage material 5 (see Fig. 1) of the camouflage system 1 may be a multi-layered camouflage composition where different layers are configured to provide camouflage in different wavelength regions of the electro-optical spectrum.

[0074] Fig. 5 illustrates a non-limiting example of the low-emissive camouflage material 5 in Fig. 1, embodied in form of multi-layered camouflage composition. The low-emissive camouflage material 5 provides camouflage in VIS, NIR, SWIR while typically exhibiting an emissivity coefficient in the range of 0.5-0.7, thus enabling the TIR signature of the camouflage system 1 to be adapted to the surrounding environment in accordance with the principles of the present disclosure.

[0075] The camouflage material 5 has a first side 5’ configured to face away from the vehicle 3 when the camouflage system 1 is mounted onto the vehicle 3. The first side 5’ of the camouflage material constitutes the outermost layer of the camouflage system 1 that is exposed to an observer of the camouflaged vehicle 3. The camouflage material 5 further has a second and opposite side 5” configured to face the vehicle 3 and the underlying heat generating arrangement 11 (see Fig. 1) when the camouflage system 1 is mounted onto the vehicle 3. The first side 5’ may hereinafter be referred to as the outside or exterior side of the camouflage material 5, whereas the second side 5” may be referred to as the inside or interior side of the camouflage material 5.

[0076] The camouflage material 5 is a multi-layered camouflage material comprising a plurality of layers 5A, 5B providing protection in different parts of the electromagnetic spectrum.

[0077] The innermost layer 5B of the camouflage material is a backing layer, hereinafter simply referred to as the backing. The backing 5B is configured to provide camouflage at least within the electro-optical parts of the electromagnetic spectrum while serving as a backing of the outermost layer 5A. The backing 5B is typically a continuous layer that is visually opaque. The backing 5B may in itself be formed as a multi-layered material. For example, the backing 5B may comprise a polymeric outer layer comprising one or more colorants selected to give the backing a desired colour. The polymeric layer may for example comprise a pigmented polyethylene film or a PVC coated fabric. The polymeric outer layer is preferably configured to be substantially transparent in TIR wavelength regions, including the important MWIR and LWIR wavelength regions. Preferably, the polymeric outer layer is also substantially transparent in the radar wavelength region. The backing 5B may or may not comprise a metallic layer that is highly reflective in TIR wavelength regions, arranged on the interior side of the polymeric outer layer. Such a metallic layer may be included in the backing 5B to reduce the thermal emissivity of the camouflage material 1. The metallic layer may, for example, be provided as a metal film that is coated onto the inner surface of the polymeric layer, i.e. onto the surface of the polymeric layer that faces the heat generating arrangement 11 (see Fig. 1). For example, the metallic layer may be provided in form of a vaporized aluminium coating, coated onto the polymeric layer. If so, the backing 5B forms a metalized, low-emissive polymeric film. In order to minimise radar reflection, the metallic layer may be crackled or broken up to form a mosaic structure. It is also contemplated that the metallic layer of the backing 5B can serve as the heat-conducting layer 17 of the heat generating arrangement 11 (see Fig. 1).

[0078] The outermost layer 5A of the camouflage material 5 is a garnish. The garnish 5A may be made from the same or similar material as the backing 5B. Just like the backing, the garnish 5A may or may not comprise a metallic layer for reducing the thermal emissivity of the material. Consequently, the thermal emissivity of the camouflage material 5 can be tailored to the surrounding environment in geographical areas in which the vehicle 3 is intended to be used by combining any of a low-emissive backing and a high-emissivity backing with any of a low-emissive garnish and a high-emissivity garnish. The garnish 5A may be incised or “leaf cut” to create a three dimensional (3D) leafy effect. The backing 5B may be partly visible through the incised garnish 5A. Both the garnish 5A and the backing 5B are preferably provided with a matte (i.e. non-glossy) surface structure. The backing 5B and the garnish 5A may be provided with the same colour or with different colours. Typically, the backing 5B and the garnish 5A is provided with the same or similar colours, or at least colours selected from a common colour scheme selected to provide camouflage within a specific terrain. For example, the backing 5B and the garnish 5A may be provided with one or more colours selected from a woodland landscape colour scheme. Appropriate colouration may be provided either throughout or on the exposed outer surface of the polymeric material of the backing 5B and the garnish 5A.

[0079] Fig. 6 illustrates another exemplary embodiment of the camouflage system 1 according to the present disclosure.

[0080] In this embodiment, the camouflage system 1 comprises a radar absorbing layer 19 arranged on the interior side of the camouflage material 5 and configured to provide camouflage at least within parts of the radar wavelength region of the electromagnetic spectrum. This is achieved through absorption of electromagnetic radiation in at least parts of the radar frequency range of 1-100 GHz. The radar absorbing layer 19 is preferably configured to provide camouflage at least within parts of any or both of the X-band (8-12 GHz) and the K-band (12-40 GHz). Preferably, the radar absorbing layer 19 is also configured to provide camouflage within at least parts of the W-band (75-110 GHz). Most preferably, the radar absorbing layer 19 is a broadband radar absorbent configured to provide camouflage within at least parts of each of the X-band, K-band and W-band. In order to provide the desired radar camouflage, the radar absorbing layer 19 may comprise electrically conductive particles, such as carbon black. The electrically conductive particles may be comprised in a foam or fabric material, such as a polyolefin, polyester or polyurethane foam or fabric. The foam or fabric material may simultaneously serve as a supporting layer of the camouflage material 5, with the heat generating arrangement 11 interposed between the radar absorbing layer 19 and the camouflage material 5. An example of a material that may be used as radar absorbing layer 19 is disclosed in US 4,064,305.

[0081] In order to reduce radar reflection and / or to distort the radar signature of the vehicle 3, the heat generating arrangement 11 may comprise discontinuous and / or irregularly shaped and / or positioned heat generating elements. In some embodiments, the heat generating arrangement 11 may comprise one or more heat elements provided with frequency selective surfaces (FSS) configured for high transmission in the radar wavelength region, in the illustrated embodiment, the heat generating arrangement 11 comprises a mesh of resistive wires 11’” constituting a heating mesh for heating the thermal area A. The heating mesh is configured to generate and distribute heat substantially uniformly across the thermal area A while being designed not to exhibit a prominent and characteristic radar signature by minimizing radar reflection and / or by providing for non-uniform reflection of incident radar radiation. Thus, when used together with an underlying radar-absorbing layer 19, the heating mesh serves to allow most incident radar radiation to pass through the heat generating arrangement 11 and be absorbed by the radarabsorbing layer 19 while distorting the radar signature caused by reflection of radar signals by the heat generating arrangement.

[0082] It should be realised that the camouflage material 5 and the radar-absorbing layer 19 may be formed as a single, integral multi-layer camouflage material with the heat generating arrangement 11 embedded there between.

[0083] With reference again made to the panel-based camouflage system illustrated in Fig. 4, at least some of the panels 2 of the camouflage system 1 may be formed by the above-described multi-layer camouflage material consisting of the low-emissive camouflage material 5, the radar-absorbing layer 19, and the integrated, embedded heat generating arrangement 11. In this scenario, the panels 2 may comprise electrical connectors for connecting the heat generating arrangement 11 of the panels 4 to the control unit 13 after application of the camouflage system 1 to the vehicle 3.

[0084] With reference still made to the panel-based camouflage system of Fig. 4, the size of the panels 2 typically depends on the size, shape and contours of the vehicle 3. As illustrated in the drawing, the camouflage system 1 typically comprises panels 2 in different sizes and shapes. Typically, the area of a panel 2 is 1 dm2-10 m2, more typically 4 dm2-4 m2, and most typically 5 dm2-3 m2. The thickness of a panel 2 may also vary. In particular, the thickness of the panel 2 depends on whether or not the camouflage system comprises a radar absorbing layer 19. Typically, the material thickness of the panel 2 (i.e. the thickness of the panel when pressing the normally leaf-cut garnish 5A tight against the backing 5B) is in the range of 3-20 mm, more typically 5-15 mm, and most typically 9-12 mm. The panel 2 is flexible in order to be bent around joints, edges and irregular surface areas of the vehicle 2. Preferably, although being flexible, the panel 3 is provided with a certain degree of rigidity in order to facilitate mounting and dismounting of the camouflage system 1 , and to make the camouflage system 1 more robust. To this end, the radar absorbing material of the radar absorbing layer 19, or an additional and innermost supporting layer of the radar absorbing layer, may be configured to provide a certain degree of rigidity to the panel 2.

[0085] It should be noted that the camouflage system 1 may comprise any of, and any combination of, the above described material layers, no matter whether the camouflage system 1 is provided in form of separate panels 3, a substantially continuous layer of material, or in any other form. It should also be appreciated that the camouflage system 1 may be devised differently, and that it may comprise more or less material layers than the exemplary material layers described above.

Claims

1. CLAIMS1 . A camouflage system (1) for camouflaging a vehicle (3), comprising a low-emissive camouflage material (5) for passively reducing an apparent temperature of at least a first thermal area (A) of the camouflage system to a temperature below an apparent temperature of the surroundings of the vehicle (3); an infrared [I R] sensor arrangement (7) for measuring the apparent temperature of the surroundings of the vehicle in at least a first measurement zone (9), which first measurements zone (9) is associated with the first thermal area (A) of the camouflage system; a controllable heat generating arrangement (11) for heating the first thermal area (A) of the camouflage system (1), and a control unit (13) configured to determine a target temperature for the first thermal area (A) based on at least the apparent temperature of the surroundings of the vehicle (3) in the first measurements zone (9), and to control the heat generating arrangement (11) to heat the first thermal area (A) to the target temperature.

2. The camouflage system (1) of claim 1 , wherein the camouflage system (1) comprises at least a first temperature sensor (15) for measuring an actual temperature of the first thermal area (A) of the camouflage system (1), the control unit (13) being configured to control the heat generating arrangement (11) to heat the first thermal area (A) based on the actual temperature of the first thermal area (A) and the target temperature.

3. The camouflage system (1) of any of the preceding claims, wherein the heat generating arrangement (11) comprises a plurality of heat elements (11) and a heat-conducting layer (17) arranged in thermal contact with the plurality of heat elements (11) and configured to distribute the heat generated by the plurality of heat elements (11) along the heat-conducting layer (17).

4. The camouflage system (1) of any of the preceding claims, wherein the camouflage system (1) is a multilayer camouflage system configured to provide multispectral camouflage in at least the thermal infrared [TIR] and the visual [VIS] wavelength regions, and further in at least one and preferably all wavelength regions selected from the group consisting of the near infrared (NIR) wavelength region, the shortwave infrared (SWIR) wavelength region, and the radar wavelength region.

5. The camouflage system (1) of any of the preceding claims, wherein the camouflage system (1) comprises a low-emissive backing (5B) for providing camouflage at least in the TIR wavelength region, and an incised garnish (5A) for providing camouflage at least in the VIS wavelength region, which garnish is attached to an exterior side of the low-emissive backing (5B) configured to face away from the vehicle (3) during use of the camouflage system (1), wherein the heat generating arrangement (11) is arranged on an opposite interior side of the low-emissive backing (5B) configured to face the vehicle (3) during use of the camouflage system (1).

6. The camouflage system (1) of claim 5, wherein the camouflage system (1) further comprises a radar-absorbing layer (19) on the interior side of the low-emissive backing (5B), wherein the heat generating arrangement (11) is arranged between the low- emissive backing (5B) and the radar-absorbing layer (19).

7. The camouflage system (1) of any of the preceding claims, wherein the camouflage system (1) comprises an alert system configured to monitor a difference in temperature between the target temperature of first thermal area (A) and an actual temperature of the first thermal area (A), and to alert an operator of the vehicle (3) when the difference in temperature exceeds a threshold value.

8. The camouflage system (1) of any of the preceding claims, wherein the IR sensor arrangement (7) comprises at least one ground IR sensor arrangement for measuring a temperature of the ground in the surroundings of the vehicle (3).

9. The camouflage system (1) of claim 8, wherein the first measurement zone (9) is a ground zone located on the ground, the ground IR sensor arrangement comprising a plurality of ground IR sensors configured to capture temperature readings from different points on the ground in the first measurement zone (9), wherein the control unit (13) is configured to determine the target temperature for the first thermal area (A) based on the temperatures measured by the plurality of ground IR sensors.

10. The camouflage system (1) of any of the preceding claims, wherein the IR sensor arrangement (7) comprises a sky IR sensor arrangement (7’) for measuring an IR radiation emitted by the sky, the control unit (11) being configured to determine the target temperature for the first thermal area (A) based on both the apparent temperature of the surroundings of the vehicle (3) in the first measurement zone (9) and the IR radiation emitted by the sky.11 . The camouflage system (1) of any of the preceding claims, wherein the IR sensor arrangement (7) comprises a plurality of IR sensors (7A-7H) for measuring a temperature of the surroundings of the vehicle (3) in each of a plurality of measurements zones (9A-9H), the heat generating arrangement (11) comprising a plurality of individually controllable heat elements for heating different thermal areas (A1-A8) of the camouflage system (1), each thermal area (A1-A8) being associated with a respective measurement zone (9A-9H), wherein the control unit (13) is configured to determine a respective target temperature for each of the plurality of thermal areas (A1-A8) based on at least the apparent temperature in its associated measurements zone, and to control the plurality of heat elements to selectively heat the thermal areas (A1-AH) such that each thermal area is heated to its target temperature.

12. The camouflage system of claim 11 when dependent on claim 7, wherein the alert system is configured to monitor, for each thermal area (A1-A8), a difference between the target temperature of the thermal area and an actual temperature of the thermal area, and to indicate to an operator of the vehicle (3) which part or parts of the vehicle have an apparent thermal signature that deviates from an apparent thermal signature of the immediate surroundings, based on the differences between the target temperatures and the actual temperatures of the thermal areas (A1-A8).

13. The camouflage system of any of the preceding claims, wherein the low-emissive camouflage material (5) has an emissivity coefficient of at most 0.8.

14. A vehicle (3) comprising a camouflage system (1) according to any of the preceding claims.

Images