Active conformal infrared window including electroactive polymer and phase-change material metasurface, and control method thereof

Abstract

One objective of the present invention is to provide an active spherical infrared window equipped with an electroactive polymer and a phase change material metasurface that integrates an electroactive polymer and a phase change material metasurface into a single spherical infrared window to respond to aerodynamic heating and aerodynamic optical distortion occurring in high-speed flight environments, and a method for controlling the same, wherein optical characteristics can be actively controlled by electrical control. To achieve the above objective, an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to one embodiment of the present invention comprises: an infrared-transmitting substrate that transmits infrared rays and at least a portion of which is formed as a curved surface; an electroactive polymer portion configured to be deformable according to an electrical input and disposed on the optical path of infrared rays passing through the infrared-transmitting substrate; a phase change material metasurface having a plurality of meta-atoms including a phase change material whose optical properties change according to a phase change and disposed on a common optical path with the electroactive polymer portion; and a control portion that controls the electrical input applied to the electroactive polymer portion and the phase change state of the phase change material metasurface, respectively, to actively control the optical properties of infrared rays passing through the infrared-transmitting substrate.

Description

Technology Field

[0001] The present invention relates to infrared optical window technology applied to high-speed aircraft, and more specifically, to an active spherical infrared window equipped with an electroactive polymer and a phase change material metasurface, and a method for controlling the same, which can actively control infrared transmission characteristics and wavefront characteristics even in environments of aerodynamic heating and aerodynamic optical distortion by utilizing the electrical deformation of an electroactive polymer and the optical phase modulation of a phase change material metasurface. Background Technology

[0003] An infrared optical device is a device that collects infrared signals incident from the outside to detect, identify, or track targets, and can be mounted on high-speed aircraft such as aircraft and unmanned aerial vehicles.

[0004] Such infrared optical devices may be equipped with an infrared window or an infrared dome at the front to transmit infrared light of the wavelength range of interest while protecting the internal optical system and infrared detector from the external environment.

[0005] In particular, infrared windows applied to high-speed aircraft can be formed in a conformal shape including curved or aspherical surfaces, taking into account the external shape and aerodynamic characteristics of the aircraft.

[0006] Spherical infrared windows can reduce the air resistance of an aircraft and improve shape compatibility with its external form, but because the curvature, angle of incidence, and optical path vary depending on the position, complex optical aberrations and wavefront distortion may occur compared to planar windows.

[0007] In addition, during high-speed flight, the temperature of the infrared window can rise significantly due to aerodynamic heating caused by the compression and viscosity of the air, and an uneven temperature distribution may form inside the window.

[0008] Since the refractive index of infrared-transmitting materials can vary with temperature, non-uniform temperature distribution can cause differences in refractive index by location, leading to optical path aberrations and wavefront errors.

[0009] In addition, the thickness, curvature, or surface shape of the window may change due to thermal expansion, and as a result, optical aberrations such as focus shift, astigmatism, coma, and spherical aberration may occur.

[0010] Aero-optic phenomena caused by shock waves, shear layers, and turbulent boundary layers formed around high-speed aircraft can also be a major cause of infrared image quality degradation.

[0011] Changes in refractive index due to changes in air density can cause temporally and spatially varying wavefront distortions, and these wavefront distortions can continuously change depending on flight speed, altitude, angle of attack, and surrounding flow conditions.

[0012] Conventionally, to solve this problem, methods such as cooling the infrared window or placing a separate correction lens, wedge, prism, or movable optical element in the optical path may be used.

[0013] However, since the cooling method requires a cooling device, a heat exchange structure, and additional thermal management configurations, it can increase the volume and weight of the system and has limitations in directly correcting dynamic aero-optical distortions caused by external flow.

[0014] Mechanical compensation methods may also require additional motors, actuators, and support structures, which complicates the optical system and makes it difficult to ensure stability against vibrations and shocks occurring in high-speed flight environments, while also having limitations in responding to rapidly changing wavefront distortions.

[0015] Although techniques to correct distortion by digitally post-processing acquired images can be used, there is a limitation in that it is difficult to completely restore signals or spatial frequency components already lost in the optical system.

[0016] Accordingly, there is an increasing need for technology that can actively control the characteristics of the optical path itself before the optical signal reaches the detector.

[0017] Electroactive polymers (EAPs) are materials whose shape can change depending on the application of voltage or an electric field, and can be utilized as active devices to control the shape or optical characteristics of optical devices without mechanical driving devices.

[0018] In particular, electroactive polymers such as dielectric elastomer actuators can provide relatively large strain and fast response characteristics, making them potentially applicable to variable focus optical devices.

[0019] However, conventional variable optical devices using electroactive polymers have mainly been applied to planar or simple variable focus optical devices, and there are technical difficulties in simultaneously securing the infrared transmittance, heat resistance, low-temperature characteristics, and structural stability required for spherical infrared windows applied to high-speed aircraft.

[0020] Meanwhile, a metasurface is a structure capable of controlling the phase, amplitude, polarization, or resonance characteristics of incident light by arranging fine meta-atoms, and has the advantage of enabling various optical functions even at a thin thickness.

[0021] In particular, metasurfaces incorporating phase change materials (PCMs) can actively control phase response or optical properties by utilizing changes in refractive index resulting from phase transitions between amorphous and crystalline states.

[0022] However, conventional phase change material metasurfaces have primarily been developed for planar optical devices, and to apply them to spherical infrared windows with curved or aspherical shapes of high-speed aircraft, it is necessary to consider both changes in optical properties due to curvature and thermal stability.

[0023] Furthermore, when an electroactive polymer and a phase change material metasurface are applied to a single optical window, the heat generated during the operation of the phase change material can affect the physical properties and deformation characteristics of the electroactive polymer, and conversely, there is also a possibility that the state of the phase change material may change unintendedly due to aerodynamic heating.

[0024] Therefore, there is a need for a new active spherical infrared window technology that effectively integrates an infrared-transmitting substrate, an electroactive polymer, a transparent electrode, a phase change material metasurface, and a thermal insulation structure into a single spherical infrared window, and can stably utilize the mechanical deformation of the electroactive polymer and the optical control function of the phase change material metasurface. Prior art literature

[0026] Korean Registered Patent Publication No. 10-2890463 The problem to be solved

[0027] One objective of the present invention, which aims to solve the aforementioned conventional problems, is to provide an active spherical infrared window equipped with an electroactive polymer and a phase change material metasurface that integrates an electroactive polymer and a phase change material metasurface into a single spherical infrared window to respond to aerodynamic heating and aerodynamic optical distortion occurring in high-speed flight environments, and a method for controlling the same, wherein optical characteristics can be actively controlled by electrical control.

[0028] In addition, another objective of the present invention is to provide an active spherical infrared window equipped with an electroactive polymer and a phase change material metasurface, and a method for controlling the same, which enables different control characteristics to be realized in a single optical window by controlling the focal length and wavefront characteristics of a relatively wide area using a change in the shape or arrangement of the optical structure due to deformation of the electroactive polymer, and controlling detailed optical characteristics using a change in the local refractive index or phase characteristics of the phase change material metasurface.

[0029] Meanwhile, another objective of the present invention is to provide an active sphere-type infrared window equipped with an electroactive polymer and a phase change material metasurface, and a method for controlling the same, by organically combining an infrared-transmitting substrate, an electroactive polymer, a transparent electrode, a phase change material metasurface, and a thermal insulation structure to suppress thermal interference caused by the driving heat of the phase change material and external aerodynamic heating, and to ensure stable optical performance and structural reliability even in flight environments accompanied by high temperature, low temperature, vibration, and shock. means of solving the problem

[0031] To achieve the above objective, an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to one embodiment of the present invention comprises: an infrared-transmitting substrate that transmits infrared rays and at least a portion of which is formed as a curved surface; an electroactive polymer portion configured to be deformable according to an electrical input and disposed on the optical path of infrared rays passing through the infrared-transmitting substrate; a phase change material metasurface having a plurality of meta-atoms including a phase change material whose optical properties change according to a phase change and disposed on a common optical path with the electroactive polymer portion; and a control portion that controls the electrical input applied to the electroactive polymer portion and the phase change state of the phase change material metasurface, respectively, to actively control the optical properties of infrared rays passing through the infrared-transmitting substrate.

[0032] In addition, in an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, the electroactive polymer part and the phase change material metasurface are stacked or bonded together to form an integral structure, and are configured such that one or more of the shape, curvature, and arrangement of the plurality of meta-atoms of the phase change material metasurface change according to the deformation of the electroactive polymer part.

[0033] In addition, in an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, the electroactive polymer part is characterized by comprising: an electroactive polymer layer that deforms according to an electrical input; and a pair of electrodes disposed between the electroactive polymer layer and applying an electric field to the electroactive polymer layer.

[0034] In addition, in an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, at least one of the pair of electrodes comprises a light-transmitting electrode disposed in a region overlapping with the optical path of infrared light, and the light-transmitting electrode comprises one or more of graphene, carbon nanotubes, transparent conductive oxides, and conductive nanostructures.

[0035] In addition, in an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, the plurality of meta-atoms of the phase change material metasurface each comprise a phase change material, and the phase change material is capable of switching between at least two of an amorphous state, a crystalline state, and an intermediate state between the amorphous state and the crystalline state, and is characterized in that one or more of the refractive index, absorption rate, transmittance, reflectance, phase retardation, and resonance characteristics of the plurality of meta-atoms change according to the change in the state.

[0036] In addition, the active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention further comprises a heating unit that provides thermal energy to the phase change material metasurface to induce a phase change of the phase change material, and the heating unit is configured to selectively heat all of the plurality of meta-atoms or some of the plurality of meta-atoms.

[0037] In addition, an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention further comprises a thermal insulating member disposed between the infrared-transmitting substrate and the electroactive polymer part, between the electroactive polymer part and the phase change material metasurface, and between the phase change material metasurface and the heating part, wherein the thermal insulating member is configured to suppress the transfer of at least one of the heat transmitted through the infrared-transmitting substrate and the heat generated from the heating part to the electroactive polymer part.

[0038] In addition, in an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, one or more of the spacing, pitch, relative position, arrangement density, and curvature of the phase change material metasurface between the plurality of meta-atoms of the electroactive polymer portion change due to deformation of the electroactive polymer portion, and accordingly, one or more of the focal length, optical power, phase distribution, and wavefront for infrared rays passing through the infrared-transmitting substrate are controlled.

[0039] In addition, in an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, the control unit controls the amount of deformation of the electroactive polymer by adjusting the electrical input applied to the electroactive polymer, controls the phase change state of the phase change material included in a part region of the phase change material metasurface, and controls one or more of the focal length, optical power, phase, wavefront, and transmission characteristics of the infrared light by controlling the deformation of the electroactive polymer and the change in optical characteristics of the phase change material metasurface independently or in combination.

[0040] In addition, to achieve the above objective, a control method for an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to another embodiment of the present invention comprises: a step of passing infrared rays through an infrared-transmitting substrate that transmits infrared rays and at least a portion of which is formed as a curved surface; a step of deforming the electroactive polymer part by applying an electrical input to the electroactive polymer part disposed on the optical path of the infrared rays passing through the infrared-transmitting substrate; a step of controlling the phase change state of a phase change material metasurface having a plurality of meta-atoms disposed on a common optical path with the electroactive polymer part and including a phase change material whose optical properties change according to the phase change; and a step of actively controlling the optical properties of the infrared rays passing through the infrared-transmitting substrate by controlling the deformation of the electroactive polymer part and the phase change state of the phase change material metasurface, respectively.

[0041] In addition, in a method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, the electroactive polymer part and the phase change material metasurface are stacked or bonded together to form an integral structure, and the step of deforming the electroactive polymer part is characterized by including a step of changing one or more of the shape, curvature, and arrangement of the plurality of meta-atoms of the phase change material metasurface according to the deformation of the electroactive polymer part.

[0042] In addition, in a method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, the electroactive polymer part comprises: an electroactive polymer layer that is deformed according to an electrical input; and a pair of electrodes disposed between the electroactive polymer layer; and the step of deforming the electroactive polymer part comprises applying an electrical input to the pair of electrodes to form an electric field in the electroactive polymer layer and deforming the electroactive polymer layer by the electric field.

[0043] In addition, in a method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, at least one of the pair of electrodes comprises a light-transmitting electrode disposed in a region overlapping with the optical path of infrared light, and the light-transmitting electrode comprises one or more of graphene, carbon nanotubes, transparent conductive oxides, and conductive nanostructures.

[0044] In addition, in a method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, the step of controlling the phase change state of the phase change material metasurface comprises the step of switching the phase change material included in each of the plurality of meta-atoms between at least two states among an amorphous state, a crystalline state, and an intermediate state between the amorphous state and the crystalline state, and is characterized by changing one or more of the refractive index, absorption rate, transmittance, reflectance, phase retardation, and resonance characteristics of the plurality of meta-atoms according to the switching of the states.

[0045] In addition, in a method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, the step of controlling the phase change state of the phase change material metasurface comprises: a step of providing thermal energy to the phase change material metasurface using a heating unit; and a step of inducing a phase change of the phase change material by selectively heating all of the plurality of meta-atoms or some of the plurality of meta-atoms by the thermal energy.

[0046] In addition, the method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention further comprises the step of disposing of a thermal insulating member between the infrared-transmitting substrate and the electroactive polymer part, between the electroactive polymer part and the phase change material metasurface, and between the phase change material metasurface and the heating part, and using the thermal insulating member to suppress the transfer of at least one of the heat transmitted through the infrared-transmitting substrate and the heat generated from the heating part to the electroactive polymer part.

[0047] In addition, in a method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, the step of deforming the electroactive polymer part includes changing one or more of the spacing, pitch, relative position, arrangement density, and curvature of the phase change material metasurface between the plurality of meta atoms of the electroactive polymer part by the deformation of the electroactive polymer part, and is characterized by controlling one or more of the focal length, optical power, phase distribution, and wavefront for infrared rays passing through the infrared-transmitting substrate according to the arrangement of the plurality of meta atoms or the change in the curvature of the phase change material metasurface.

[0048] In addition, in a method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface according to the present invention, the step of actively controlling the optical characteristics of the infrared radiation comprises: a step of controlling the amount of deformation of the electroactive polymer part by controlling the electrical input applied to the electroactive polymer part; a step of controlling the phase change state of the phase change material included in a part region of the phase change material metasurface; and a step of controlling one or more of the focal length, optical power, phase, wavefront, and transmission characteristics of the infrared radiation by controlling the deformation of the electroactive polymer part and the change in optical characteristics of the phase change material metasurface independently or in combination.

[0049] Meanwhile, to achieve the above objective, an active sphere infrared window having an electroactive polymer and a phase change material metasurface according to another embodiment of the present invention is characterized by being controlled by a control method for an active sphere infrared window having an electroactive polymer and a phase change material metasurface.

[0051] Specific details of other embodiments are included in "Specific details for implementing the invention" and the attached "drawings".

[0052] The advantages and / or features of the present invention and the methods for achieving them will become clear by referring to the various embodiments described below in detail together with the accompanying drawings.

[0053] However, it should be understood that the present invention is not limited to the configurations of each embodiment disclosed below, but may be implemented in various different forms, and that each embodiment disclosed in this specification is provided merely to make the disclosure of the present invention complete and to fully inform those skilled in the art of the scope of the present invention, and that the present invention is defined only by the scope of each claim of the claims. Effects of the invention

[0055] As such, according to the present invention, by integrating an electroactive polymer and a phase change material metasurface into a single spherical infrared window, optical characteristics can be actively controlled in response to aerodynamic heating and aero-optical distortion occurring during high-speed flight, thereby having the effect of improving the resolution, focus stability, and wavefront quality of infrared images.

[0056] In addition, according to the present invention, by utilizing mechanical deformation over a relatively wide area of ​​an electroactive polymer together with local phase or refractive index control of a phase change material metasurface, it is possible to effectively respond to changes in focal length and complex wavefront errors while reducing the use of mechanical optical correction devices, and there is an advantageous effect for miniaturization and weight reduction of the optical system.

[0057] In addition, according to the present invention, by organically combining an infrared-transmitting substrate, an electroactive polymer, a phase change material metasurface, and a thermal insulation structure, mutual thermal interference caused by the driving heat of the phase change material and external aerodynamic heating can be suppressed, and stable optical performance and structural reliability can be secured even in flight environments accompanied by high temperature, low temperature, vibration, and shock. Brief explanation of the drawing

[0059] FIG. 1 is a block diagram schematically showing the overall configuration of an infrared optical system including an active spherical infrared window according to one embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a multilayer stacked structure of an active sphere infrared window according to one embodiment of the present invention. FIG. 3 is a schematic plan view showing a configuration in which a plurality of metacells corresponding to different infrared wavelength ranges are arranged on a metasurface of a phase change material according to one embodiment of the present invention. FIG. 4 is a schematic diagram showing a configuration for measuring an incident wavefront and calculating Zernike coefficients using a Shack-Hartmann type wavefront sensor according to one embodiment of the present invention. FIG. 5 is a diagram schematically illustrating the process of generating driving signals for an electroactive polymer part and a phase change material metasurface by estimating wavefront distortion using a plurality of images and calculating Zernike coefficients by the Phase Diversity method according to one embodiment of the present invention. FIG. 6 is a flowchart schematically illustrating a control process according to one embodiment of the present invention, which distributes the Zernike mode of the wavefront error to the electroactive polymer part and the phase change material metasurface and determines the driving amount for each. FIG. 7 is a timing diagram schematically showing the temporal operation relationship of a dual-loop adaptive optical control combined with a high-speed control loop of the Shack-Hartmann method and a low-speed correction loop of the Phase Diversity method according to one embodiment of the present invention. FIG. 8 is a block diagram schematically showing the configuration of a high-speed control loop and a low-speed control loop of an adaptive optical device including an electroactive polymer part and a phase change material metasurface according to one embodiment of the present invention. FIG. 9 is a diagram schematically illustrating the correction process of an infrared image through the estimation and correction of wavefront error according to an embodiment of the present invention, as well as the image and wavefront state before and after correction. FIG. 10 is a flowchart schematically illustrating a control method for controlling the optical properties of an active spherical infrared window using an electroactive polymer part and a phase change material metasurface according to one embodiment of the present invention. Specific details for implementing the invention

[0060] Before describing the present invention in detail, it should be understood that the terms and words used in this specification should not be interpreted as being limited to their ordinary or dictionary meanings, and that the inventor of the present invention may appropriately define and use the concepts of various terms to best describe their invention, and furthermore, that these terms and words should be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0061] In other words, it should be understood that the terms used in this specification are used merely to describe preferred embodiments of the present invention and are not intended to specifically limit the content of the present invention, and that these terms are defined in consideration of various possibilities of the present invention.

[0062] In addition, it should be noted that in this specification, singular expressions may include plural expressions unless the context clearly indicates a different meaning, and that even if they are expressed in a similarly plural form, they may include the meaning of the singular.

[0063] Throughout this specification, where it is stated that a component "includes" another component, unless specifically stated otherwise, this may mean that it does not exclude any other component but may include any other component.

[0064] Furthermore, it should be noted that in cases where it is stated that a component "exists inside or is installed in connection with" another component, this component may be installed in direct connection or contact with the other component, or it may be installed at a certain distance apart, and in the case where it is installed at a certain distance apart, there may be a third component or means for fixing or connecting the component to the other component, and a description of this third component or means may be omitted.

[0065] On the other hand, if it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there is no third component or means.

[0066] Likewise, other expressions describing the relationship between each component, such as “between” and “right between”, or “adjacent to” and “directly adjacent to”, should be interpreted as having the same intent.

[0067] In addition, it should be understood that in this specification, terms such as “one side,” “other side,” “one side,” “other side,” “first,” “second,” etc., are used to clearly distinguish one component from another component, and that the meaning of the component is not restricted by such terms.

[0068] In addition, position-related terms such as "up," "down," "left," and "right" used in this specification should be understood as indicating the relative position of the corresponding component in the drawing, and unless an absolute position is specified, these position-related terms should not be understood as referring to an absolute position.

[0069] Furthermore, in specifying the reference numerals for each component of each drawing in this specification, the same component has the same reference numeral even if it is shown in different drawings; that is, the same reference numeral throughout the specification indicates the same component.

[0070] In the drawings attached to this specification, the size, position, connection relationships, etc., of each component constituting the present invention may be described in a partially exaggerated, reduced, or omitted manner for the convenience of explanation or to sufficiently clearly convey the concept of the present invention, and therefore, the proportions or scale may not be strictly accurate.

[0071] In addition, in the following description of the present invention, detailed descriptions of components that are deemed to unnecessarily obscure the essence of the present invention, such as known technologies including prior art, may be omitted.

[0073] Hereinafter, embodiments of the present invention will be described in detail with reference to the relevant drawings.

[0075] With reference to FIGS. 1 to 10, an active spherical infrared window equipped with an electroactive polymer and a phase change material metasurface according to one embodiment of the present invention and a method for controlling the same will be described in detail.

[0076] In this specification, the term "spherical shape" may be understood as a concept including a curved, aspherical, or freeform shape that is continuously connected to or formed to correspond to the external shape of the aircraft.

[0077] In this specification, infrared radiation may include near-infrared radiation, mid-wave infrared radiation (MWIR), long-wave infrared radiation (LWIR), or a combination thereof.

[0078] Medium-wavelength infrared radiation may include, for example, a wavelength band of about 3 μm to about 5 μm.

[0079] Long-wavelength infrared radiation may include, for example, a wavelength band of about 8 μm to about 12 μm.

[0080] In this specification, an electroactive polymer (EAP) may include a polymer material in which one or more of the thickness, area, length, curvature, or shape can be changed by voltage or an electric field.

[0081] Dielectric elastomer actuators (DEA) can be used as an example of electroactive polymers, but are not limited thereto.

[0082] In this specification, a phase change material (PCM) may refer to a material that can switch between at least two states depending on externally provided thermal, electrical, or optical energy, and in which one or more of the refractive index, absorption rate, transmittance, reflectance, phase retardation, and resonance characteristics may change depending on the state change.

[0083] Phase change materials can have an amorphous state, a crystalline state, and an intermediate state or a partially crystalline state between the amorphous and crystalline states.

[0084] The phase change material may include germanium-antimony-selenium-tellurium (GSST: Ge-Sb-Se-Te)-based materials, germanium-antimony-tellurium (GST: Ge-Sb-Te)-based materials, or materials having similar optical phase change properties.

[0085] The size, thickness, number, spacing, and arrangement of each component depicted in the drawings are for the convenience of explanation and may be changed in actual implementation depending on the required optical performance, wavelength of use, flight environment, and manufacturing process.

[0086] The materials, dimensions, temperature, response time, and performance figures described below are intended to illustrate one embodiment or design example and are not intended to limit the scope of the invention to specific materials or figures.

[0088] FIG. 1 is a block diagram schematically showing the overall configuration of an infrared optical system including an active spherical infrared window according to one embodiment of the present invention.

[0089] Referring to FIG. 1, an active spherical infrared window (100) for transmitting infrared rays incident from the outside to an internal optical system may be disposed in the aircraft nose cone (10).

[0090] The aircraft nose cone (10) may include the external structure of a mobile body carrying not only a fixed-wing aircraft but also a guided weapon, an unmanned aerial vehicle, a high-speed aircraft or an infrared search device.

[0091] The active spherical infrared window (100) can be formed as a curved surface, an aspherical surface, or a freeform surface connected to the external shape of the aircraft.

[0092] The active ball-shaped infrared window (100) can be directly or indirectly exposed to an aerodynamic heating environment (20).

[0093] In a high-speed flight environment, the temperature of the aircraft nose cone (10) and the active ball-shaped infrared window (100) may increase due to the adiabatic compression and viscous effects of the air.

[0094] The Mach number of the free flow , free flow temperature , the specific heat ratio of air When saying that, the stagnation point temperature according to the adiabatic compression approximation It can be expressed as shown in the following Equation 1.

[0095] [Formula 1]

[0096]

[0097] The specific heat ratio of air is about 1.4, and Mach 4 and Under these conditions, the stagnation point temperature can increase to about 924 K.

[0098] The actual wall temperature of the window may be lower than the stagnation point temperature due to the influence of conduction, radiation, and re-radiation, but it can rise to a level of about 500 K to about 700 K.

[0099] Aerodynamic heating can cause a non-uniform temperature distribution inside an infrared-transmitting substrate.

[0100] Infrared-transmitting materials such as sapphire or spinel are about 10 -5 In the case of a thermochemical coefficient at the / K level, large temperature variations can cause differences in refractive index depending on the location.

[0101] Non-uniform refractive index distribution can cause optical path differences at the level of tens of µm, and in the mid-wavelength infrared band of about 4 µm, it can appear as wavefront errors corresponding to multiple wavelengths.

[0102] The self-heat radiation of the window due to aerodynamic heating can increase significantly as the temperature of the window increases and can affect the background signal and fixed pattern noise of the infrared detector (400).

[0103] The thermal expansion of a window is length L, coefficient of thermal expansion and temperature change About It can have a relationship.

[0104] Thermal expansion of a hollow window changes the curvature of the window and can consequently cause boresight errors.

[0105] In addition, density fluctuations within the high-speed turbulent boundary layer can cause time-varying dynamic aero-optical distortion.

[0106] Aero-optical distortion may include frequency components of several hundred Hz or several kHz depending on the operating environment.

[0107] Infrared rays passing through the active sphere infrared window (100) can be transmitted to the gimbal (200), optical system (300), and infrared detector (400).

[0108] The gimbal (200) can change the orientation direction or line of sight axis of the optical system.

[0109] The optical system (300) may include one or more lenses, mirrors, diffractive optical elements, apertures, or optical filters.

[0110] The infrared detector (400) may include a focal plane array (FPA) and can convert incident infrared light into an electrical image signal.

[0111] A portion of the light passing through the optical system (300) can be transmitted to the wavefront sensor (500).

[0112] The wavefront sensor (500) can measure or estimate wavefront error by the Shack-Hartmann method, the Phase Diversity method, or a combination thereof.

[0113] The control unit (600) can receive wavefront information from the wavefront sensor (500) and analyze the wavefront error.

[0114] The control unit (600) can decompose the wavefront error into a plurality of Zernike modes.

[0115] The control unit (600) can control the electrical input applied to the electroactive polymer unit through the high voltage amplifier (610).

[0116] The control unit (600) can control the phase change state of the phase change material metasurface (160) through the heater driving unit (620).

[0117] Accordingly, the active sphere infrared window (100) can actively adjust optical characteristics in response to aerodynamic heating and aerodynamic optical distortion that change during flight.

[0119] Next, the stacked structure of the active ball-shaped infrared window is described.

[0120] FIG. 2 is a cross-sectional view schematically showing a multilayer stacked structure of an active sphere infrared window (100) according to one embodiment of the present invention.

[0121] An active sphere infrared window (100) may include a diamond-like carbon (DLC) hardcoat (111), an infrared-transmitting substrate (110), a first thermal insulation part (120), an upper transparent electrode (130), an electroactive polymer layer (140), a lower transparent electrode (150), a phase change material metasurface (160), a second thermal insulation part (170), a heating part (180), and a frame or encapsulation part (190) facing from the outside or air side toward the inside or optical measurement.

[0122] The diamond-like carbon hardcoat (111) can protect the infrared-transmitting substrate (110) from sand dust, raindrops, particle collisions and erosion.

[0123] The diamond-like carbon hardcoat (111) can be formed with a thickness of, for example, about 1 μm.

[0124] The infrared-transmitting substrate (110) may include sapphire, spinel, or other infrared-transmitting optical materials.

[0125] The infrared-transmitting substrate (110) may have a thickness of, for example, about 3 mm to about 5 mm.

[0126] The infrared-transmitting substrate (110) may have a curved or non-spherical shape corresponding to the external shape of the aircraft.

[0127] The first thermal insulation part (120) can suppress the transfer of heat from aerodynamic heating transmitted through the infrared transparent substrate (110) to the electroactive polymer layer (140).

[0128] The first thermal insulation part (120) may include a porous aerogel-based thin film.

[0129] The thermal conductivity of the first thermal insulation part (120) can be, for example, about 0.02 W / (m·K).

[0130] The thickness of the first thermal insulation part (120) can be, for example, about 20 μm.

[0131] The upper transparent electrode (130) and the lower transparent electrode (150) can be placed on both sides of the electroactive polymer layer (140).

[0132] The upper transparent electrode (130) and the lower transparent electrode (150) may include one or more of graphene, a carbon nanotube network, a transparent conductive oxide, and a conductive nanostructure.

[0133] The electroactive polymer layer (140) may include a silicon-based dielectric elastomer having low-temperature properties.

[0134] The thickness of the electroactive polymer layer (140) can be, for example, about 50 μm.

[0135] The phase change material metasurface (160) may include a plurality of nanopillars, nanodisks, or other forms of metaatoms made of germanium-antimony-selenium-tellurium or germanium-antimony-tellurium phase change materials.

[0136] The meta-atoms of the phase change material meta-surface (160) can have a height or thickness of, for example, about 600 nm.

[0137] The second thermal insulation section (170) can suppress the transfer of heat generated in the heating section (180) and the phase change material metasurface (160) to the electroactive polymer layer (140).

[0138] The heating unit (180) may be composed of a microheater grid comprising tungsten (W), indium tin oxide (ITO), or other resistance heating materials.

[0139] The heating unit (180) can be configured to be divided into multiple regions so that each region is independently addressable.

[0140] Accordingly, all or part of the phase change material metasurface (160) can be selectively heated.

[0141] The frame or encapsulation portion (190) can maintain the pre-deformation of the electroactive polymer layer (140) and mechanically support the laminated structure.

[0142] The frame or the encapsulation portion (190) may also provide an electrical interface between the electrode and the heater.

[0144] Next, the independent control degrees of freedom of electroactive polymers and phase change materials are explained.

[0145] The electroactive polymer layer (140) and the phase change material metasurface (160) can be stacked or combined to be integrated and can be placed on a common optical path.

[0146] The electroactive polymer layer (140) and the phase change material metasurface (160) can perform complementary optical modulation using different control inputs.

[0147] The electroactive polymer layer (140) can be deformed over a relatively wide area by Maxwell stress according to the applied voltage.

[0148] The response time of the electroactive polymer may be at the ms level in one example.

[0149] A static or quasi-static electrical input may be provided to continuously maintain the deformation state of the electroactive polymer.

[0150] Electroactive polymers can be used to correct relatively low-order spatial wavefront variations, including defocus and astigmatism.

[0151] The phase change material metasurface (160) can have its positional crystallinity changed by being locally heated by a heater pulse.

[0152] The response time of the phase change material may be at the μs level in one embodiment.

[0153] Since phase change materials can have non-volatile characteristics, they do not require continuous maintenance power or can significantly reduce maintenance power after the desired phase change state is formed.

[0154] Phase change materials can be used to locally correct relatively high-order wavefront errors, including coma, spherical aberration, and trefoil.

[0155] Electroactive polymers and phase change materials can be driven independently of each other.

[0156] Electroactive polymers and phase change materials can be driven simultaneously or sequentially in time.

[0158] Next, we will explain the double-band phase change material metasurface.

[0159] FIG. 3 is a schematic plan view showing a configuration in which a plurality of metacells corresponding to different infrared wavelength ranges are arranged on a metasurface of a phase change material according to one embodiment of the present invention.

[0160] The phase change material metasurface (160) may include a first metacell (161) corresponding to a mid-wave infrared band and a second metacell (162) corresponding to a long-wave infrared band.

[0161] The first metacell (161) may include an M cell.

[0162] The second metacell (162) may include an L cell.

[0163] M cells and L cells can be arranged alternately in a checkerboard pattern.

[0164] In other embodiments, the M cells and L cells may have stripes, clusters, matrices, or non-periodic arrays.

[0165] The meta-atoms of the M cell can have, for example, a diameter of about 0.8 μm and a pitch of about 2 μm.

[0166] The meta-atoms of the L cell can have, for example, a diameter of about 1.8 μm and a pitch of about 4 μm.

[0167] By applying demosaicing processing to the image obtained from a single infrared detector (400), a mid-wavelength infrared image and a long-wavelength infrared image can be extracted.

[0168] The heating unit (180) can independently activate or deactivate the M cell group and the L cell group.

[0169] Accordingly, it can be operated in one of the following modes: a mid-wavelength infrared single-band mode, a long-wavelength infrared single-band mode, or a mid-wavelength infrared / long-wavelength infrared dual-band mode.

[0170] When a interference wavelength associated with a laser jammer or flare is detected or provided from the outside, the control unit (600) can control a portion of the phase change material so that absorption or reflection for that wavelength increases.

[0171] Accordingly, a spectrum evasion function to counter Infrared Countermeasures (IRCM) can be implemented.

[0172] The spectrum mode may be changed multiple times depending on the required operational conditions during flight.

[0174] Next, the Sharke-Hartmann method of wavefront measurement is explained.

[0175] FIG. 4 is a schematic diagram showing a configuration for measuring an incident wavefront and calculating Zernike coefficients using a Shack-Hartmann type wavefront sensor according to one embodiment of the present invention.

[0176] The wavefront sensor (500) may include a lenslet array (510) and a Shack-Hartmann Wavefront Sensor (SHWS) detector (520).

[0177] The lenslet array (510) may include, for example, about 20×20 to about 40×40 microlenses.

[0178] The Shark-Hartmann wavefront sensor detector (520) may include a small medium-wavelength infrared detector or an auxiliary visible light detector for wavefront measurement.

[0179] The wavefront sensor (500) may further include a calibration reference light source in the form of a semiconductor laser or a light-emitting diode as needed.

[0180] Let the incident wavefront be W(x,y), and the spot corresponding to the (i,j)th lenslet of the lenslet array (510) be from the reference position, respectively and When moved by that amount, the average wavefront slope of the corresponding area can be expressed as Equation 2 below.

[0181] [Equation 2]

[0182]

[0183] Here f L is the focal length of the lenslet.

[0184] The entire wavefront can be reconstructed using the gradient field obtained from each lenslet.

[0185] When using the Zernike mode-based restoration method, the measured gradient vector is s, the Zernike gradient influence matrix is ​​G, and the Zernike coefficient vector is When the measurement noise is denoted as n, the following Equation 3 can be used.

[0186] [Equation 3]

[0187]

[0188] If the lenslet array (510) includes N×N lenslets, the gradient vector s is 2N 2 It can have the form of × 1.

[0189] The control unit (600) may use Tikhonov regularization to suppress measurement noise and instability of the inverse matrix operation.

[0190] The normalized least squares solution can be expressed as shown in Equation 4 below.

[0191] [Equation 4]

[0192]

[0193] Here is the Tikhonov normalization parameter and I is the identity matrix.

[0194] The Sharke-Hartman method can directly calculate the wavefront slope in a single frame, so it can be advantageous for high control bandwidth.

[0195] In one embodiment, a measurement or correction bandwidth of about 1 kHz or more can be targeted.

[0196] On the other hand, the lenslet array and dedicated detector may occupy additional space.

[0197] Spot crosstalk may occur under strong parallax conditions.

[0198] Under low-light conditions, the signal-to-noise ratio of spot detection may degrade.

[0199] Therefore, the Sharke-Hartmann method can be advantageously applied to high-speed control loops that compensate for rapid aerodynamic fluctuations.

[0201] Next, we will explain the wavefront estimation method of the phase diversity method.

[0202] FIG. 5 is a diagram schematically illustrating the process of generating driving signals for an electroactive polymer part and a phase change material metasurface by estimating wavefront distortion using a plurality of images and calculating Zernike coefficients by the Phase Diversity method according to one embodiment of the present invention.

[0203] The phase diversity method can inversely estimate the wavefront error by using the image itself acquired by the infrared detector (400) without necessarily using a separate lenslet.

[0204] In one embodiment, a focused image and an image with intentional out-of-focus added can be obtained, respectively.

[0205] Intentional defocus can be formed using a control voltage applied to the electroactive polymer layer (140).

[0206] In another embodiment, a known phase pattern can be formed by setting a portion of the phase change material metasurface (160) as a diagnostic area.

[0207] The unknown status of hiring and dismissal ...saying that the diversity status of the base that is intentionally added When saying that The second video It can be expressed as shown in the following Equation 5.

[0208] [Formula 5]

[0209]

[0210] Here is the pupil function, and is the original scene, and is the inverse Fourier transform, and is a convolution operation, and is measurement noise.

[0211] It can correspond to a focal image and It can handle out-of-focus images.

[0212] The control unit (600) can estimate an unknown wavefront using a cost function based on maximum likelihood estimation in the frequency domain.

[0213] The cost function can be expressed as shown in the following Equation 6.

[0214] [Equation 6]

[0215]

[0216] Here and are the optical transfer functions at corresponding image conditions, and and is the Fourier transform of the measured image.

[0217] Unknown dismissal Is It can be parameterized by Zernike coefficients in the form of.

[0218] The control unit (600) can repeatedly update the Zernike coefficients to minimize the cost function.

[0219] Zernike coefficients are It can be determined to satisfy the conditions of.

[0220] The Levenberg-Marquardt method or the Gauss-Newton method can be used for iterative optimization.

[0221] When applying parallel GPU computation, a refresh rate of several Hz to tens of Hz can be achieved.

[0222] The phase diversity method can minimize the need for a separate optical unit for the wavefront sensor and utilize the focal plane array image itself.

[0223] In low-light environments, a signal-to-noise ratio more favorable than the Sharke-Hartmann method can be achieved depending on operating conditions.

[0224] On the other hand, since iterative optimization is required, the effective control bandwidth may be limited to, for example, about 10 Hz to about 50 Hz.

[0226] Next, the deformation principle and variable focus function of electroactive polymers are explained.

[0227] When a voltage V is applied to the upper transparent electrode (130) and the lower transparent electrode (150) located on both sides of the electroactive polymer layer (140), Maxwell stress may be generated in the electroactive polymer layer (140).

[0228] The thickness of the electroactive polymer layer (140) is d, and the relative permittivity is , vacuum permittivity When the electric field is denoted as E, the Maxwell pressure p can be expressed as shown in Equation 7 below.

[0229] [Equation 7]

[0230]

[0231] Assuming incompressible conditions and letting Young's modulus be Y, the strain in the thickness direction and area strain It can be expressed as shown in the following Equation 8.

[0232] [Equation 8]

[0233]

[0234] In one embodiment In this case, the Maxwell pressure can be about 62 kPa.

[0235] The area strain can be about 7.8%.

[0236] When the phase change material metasurface (160) is integrally bonded with the electroactive polymer layer (140), the spacing or pitch of the meta-atoms can also change in response to the in-plane deformation of the electroactive polymer.

[0237] The basic phase profile of a metalens can be expressed as follows.

[0238]

[0239] New focal length in paraxial approximation when the metasurface is radially magnified by s It can be expressed as shown in the following Equation 9.

[0240] [Formula 9]

[0241]

[0242] When s=0.08, the new focal length is approximately It can be.

[0243] Accordingly, in one design example, it may be possible to adjust the focal length by about 17%.

[0245] Next, the principles of phase change and phase modulation of phase change materials are explained.

[0246] Germanium-antimony-selenium-tellurium-based phase change materials can have a difference in refractive index in the mid-wave infrared and long-wave infrared bands between the amorphous and crystalline states.

[0247] In one embodiment, the refractive index contrast at a wavelength of about 4 μm may be about 1.8.

[0248] Partial determination If the value is set to 0 to 1, the effective refractive index can be approximated as shown in the following Equation 10.

[0249] [Formula 10]

[0250]

[0251] Here is the refractive index of the crystalline state. is the refractive index of the amorphous state.

[0252] The thickness of the phase change material meta-atom When saying that, the local phase change can be expressed as in the following Equation 11.

[0253] [Equation 11]

[0254]

[0255] In one embodiment The condition can be used.

[0256] The maximum phase change due to a complete phase transition is approximately It could be at that level.

[0257] By adjusting the partial crystallinity, approximately 0 to Continuous phase modulation of the range may be possible.

[0258] The thermal energy required for the crystallization of a phase change material cell can be expressed as shown in the following Equation 12.

[0259] [Equation 12]

[0260]

[0261] Here is density, is specific heat, and is the cell volume, and is the crystallization temperature, and is the initial temperature, and is the latent heat of crystallization.

[0262] The density of the germanium-antimony-selenium-tellurium system is approximately , specific heat is weak , crystallization temperature is approximately And the volume of the cell is approximately In this case, the required energy is [number] It can become a level.

[0263] This energy can be supplied using pulses of about 100 ns to about 1 μs.

[0265] Next, the bonding phase of electroactive polymers and phase change materials is explained.

[0266] Geometric deformation caused by electroactive polymers and local phase change caused by phase change materials can be combined in a common optical path.

[0267] When geometric deformation of s occurs in the radial direction due to the electroactive polymer and local phase change occurs due to the phase change material, the overall phase can be expressed as Equation 13 below.

[0268] [Equation 13]

[0269]

[0270] Accordingly, electroactive polymers can provide geometric phase changes over a relatively wide spatial region, and phase change materials can provide local phase correction with high spatial resolution.

[0272] Next, the distribution and determination of driving amounts of the Zernike mode will be explained.

[0273] FIG. 6 is a flowchart schematically illustrating a control process according to one embodiment of the present invention, which distributes the Zernike mode of the wavefront error to the electroactive polymer part and the phase change material metasurface and determines the driving amount for each.

[0274] Referring to FIG. 6, the wavefront measured or estimated by the wavefront sensor (500). It can be broken down into multiple Zernike modes.

[0275] Normalized pupil coordinates When that is the case, the measured wavefront can be expressed as shown in the following Equation 14.

[0276] [Equation 14]

[0277]

[0278] Here, is of the Zernike polynomial It is the th mode, and is the coefficient corresponding to the corresponding Zernike mode.

[0279] Each Zernike coefficient when using the orthogonality of Zernike polynomials It can be calculated as follows.

[0280]

[0281] The control unit (600) can distribute each wavefront error mode to the electroactive polymer unit or phase change material metasurface (160) based on the calculated Zernike coefficient.

[0282] In one embodiment, the set of lower-order modes distributed to the electroactive polymer is It can be defined as.

[0283]

[0284] Here, It can respond to defocus and It can correspond to astigmatism.

[0285] Since the electroactive polymer part can change its shape or curvature over a relatively wide area, it can be used to correct these low-order wavefront errors.

[0286] The higher-order Zernike mode set distributed to the phase change material metasurface (160) is It can be defined as.

[0287] In one embodiment, a higher-order mode set It can be defined as follows.

[0288]

[0289] Here is the radial degree of the Zernike polynomial, and It can represent the azimuth order.

[0290] The phase change material metasurface (160) can form a local phase change by controlling the phase change state at each location, so it can be used to correct relatively high-order wavefront errors including coma, spherical aberration, trefoil, etc.

[0291] electroactive polymer part The influence function for the i-th Zernike mode It can be said that.

[0292] Here, V may represent the electrical input or driving voltage applied to the electroactive polymer part.

[0293] The control unit (600) provides an optimal driving voltage to minimize the wavefront error of the Zernike mode distributed to the electroactive polymer unit. can decide.

[0294] Optimal driving voltage can be determined as shown in the following Equation 15.

[0295] [Formula 15]

[0296]

[0297] Accordingly, the high-voltage amplifier (610) has a determined optimal driving voltage Electrical input corresponding to can be provided to the electroactive polymer part.

[0298] The electroactive polymer part can correct wavefront errors corresponding to Zernike modes distributed by deformation according to the provided electrical input.

[0299] of the phase change material metasurface (160) The influence function for the i-th Zernike mode It can be said that.

[0300] Here It can indicate the crystallinity or phase change state of a phase change material.

[0301] The control unit (600) has an optimal crystallinity distribution to minimize the wavefront error of the Zernike mode distributed on the phase change material metasurface (160). can decide.

[0302] The optimal determination distribution can be determined as shown in the following Equation 16.

[0303] [Equation 16]

[0304]

[0305] The heater driving unit (620) can provide heater pulses to the heating unit (180) in response to the determined optimal crystallinity distribution.

[0306] The heating unit (180) can heat a selected area of ​​the phase change material metasurface (160) to control the phase change state at each location.

[0307] Accordingly, the phase change material metasurface (160) can perform local phase correction corresponding to higher-order Zernike modes.

[0308] The distribution of Zernike modes on the electroactive polymer part and the phase change material metasurface (160) is not limited to one fixed method.

[0309] Depending on the driving range of the electroactive polymer part, the spatial resolution of the phase change material metasurface (160), the required response speed, correction precision, driving state, or temperature state, one Zernike mode may be selectively distributed to either the electroactive polymer part or the phase change material metasurface (160), or distributed to both.

[0310] Therefore, the lower-order mode in Fig. 6 Allocate to and higher-order modes The configuration for distributing to represents one embodiment, and the Zernike mode distribution method of the present invention is not limited thereto.

[0312] Next, residual wavefront error and Strehl ratio are explained.

[0313] The residual fracture surface after correction by electroactive polymers and phase change materials can be defined as follows.

[0314]

[0315] The root mean square (RMS) of the residual wavefront can be expressed as shown in the following Equation 17.

[0316] [Equation 17]

[0317] =

[0318] The strelle ratio according to the Marechal approximation can be expressed as shown in the following Equation 18.

[0319]

[0320] In one design example, the Strel ratio It can be set to.

[0321] In this case, the residual wavefront error is approximately The following can be aimed for.

[0322] For medium-wavelength infrared wavelengths of about 4 μm, a root mean square wavefront error of about 0.29 μm or less can be set as a design target.

[0324] Next, the number of control cells in the phase change material metaarray is explained.

[0325] To correct high-order wavefront errors, the phase change material metasurface (160) can have sufficient spatial control freedom.

[0326] The number of pixels required for the phase change material metasurface (160) can be determined by considering the minimum value according to the optical spatial sampling conditions and the practical design value according to the actual manufacturing process and driving structure.

[0327] First, the maximum correction order When saying, The optical minimum number of pixels for spatially sampling up to the Zernike mode can be set as in the following Equation 19a in one embodiment.

[0328] [Equation 19a]

[0329]

[0330] Here It can represent the total number of control pixels required for wavefront correction.

[0331] for example In this case, the minimum number of pixels for optical spatial sampling can be set to 144 or more.

[0332] Meanwhile, the number of pixels of the actual phase change material metasurface (160) can be determined based on the effective aperture and the pixel pitch of the micro heater.

[0333] Effective caliber It is called the pixel pitch of the micro heater In this case, the number of practical design pixels based on a square pixel array can be expressed as shown in the following Equation 19b.

[0334] [Equation 19b]

[0335]

[0336] In one design example You can use the condition.

[0337] In this case, approximately 500 control pixels can be placed in one direction of the effective aperture, and based on a square array, the total number of pixels is approximately You can become a dog.

[0338] Therefore, in one design example, a metaarray of approximately 500×500 can be used.

[0339] The actual number of pixels may vary depending on the required correction order, effective aperture, pixel pitch of the heater, manufacturing process, thermal diffusion characteristics, and required spatial resolution.

[0341] Next, the thermal insulation design is explained.

[0342] A thermal insulation structure may be provided so that the thermal driving of the phase change material using the heating unit (180) does not excessively increase the temperature of the electroactive polymer layer (140).

[0343] The thermal diffusivity of phase change materials , pulse duration When that is the case, the thermal diffusion length can be expressed as shown in the following Equation 20.

[0344] [Formula 20]

[0345]

[0346] The thermal diffusivity of the germanium-antimony-selenium-tellurium system is approximately And, when the pulse duration is about 200 ns, the thermal diffusion length can be limited to about 180 nm.

[0347] Accordingly, heat can be relatively localized within a phase change material layer approximately 600 nm high.

[0348] The thermal conductivity of the thermal insulation , maximum temperature rise allowed for electroactive polymers , the average heat flux of the heater When that is the case, the required thickness of the thermal insulation can be expressed as shown in the following Equation 21.

[0349] [Equation 21]

[0350]

[0351] In one design example In this case, a thermal insulation thickness of about 0.4 μm or more can be used as a design standard.

[0352] The actual thickness of the first thermal insulation part (120) or the second thermal insulation part (170) may be changed depending on optical transmittance, mechanical stability, manufacturing process and temperature environment.

[0354] Next, dual-loop adaptive optics control will be explained.

[0355] FIG. 7 is a timing diagram schematically showing the temporal operation relationship of a dual-loop adaptive optical control combined with a high-speed control loop of the Shack-Hartmann method and a low-speed correction loop of the Phase Diversity method according to one embodiment of the present invention.

[0356] The high-speed control loop can measure the wavefront and update the correction signal at time intervals of, for example, about 1 ms.

[0357] Accordingly, a correction bandwidth of approximately 1 kHz can be achieved.

[0358] The high-speed control loop can correct rapidly changing aero-optical distortion.

[0359] The low-speed control loop can perform phase diversity wavefront estimation at intervals of about 1 second, for example.

[0360] The low-speed control loop can reset the reference wavefront of the Sharke-Hartmann wavefront sensor or correct long-term accumulated errors.

[0361] Non-common optical path errors caused by the difference between the main optical path and the optical path for the wavefront sensor can also be corrected by the phase diversity method.

[0362] The control conditions of the high-speed control loop and the low-speed control loop can be changed according to changes in flight conditions, such as an increase in Mach number, the initiation of rapid maneuvers, the peak of aerodynamic heating, or the approach of a target.

[0364] Next, the high-speed and low-speed control structures will be explained.

[0365] FIG. 8 is a block diagram schematically showing the configuration of a high-speed control loop and a low-speed control loop of an adaptive optical device including an electroactive polymer part and a phase change material metasurface according to one embodiment of the present invention.

[0366] Referring to FIG. 8, incident light from the outside can be transmitted to an optical system (300) after passing through an active sphere infrared window (100).

[0367] The active sphere infrared window (100) may include an electroactive polymer layer (140) and a phase change material metasurface (160).

[0368] The electroactive polymer layer (140) can be deformed according to an electrical input, and the phase change material metasurface (160) can have its optical properties changed according to the phase change state.

[0369] A portion of the light passing through the optical system (300) can be branched to the wavefront sensor (500), and the remaining light can be transmitted to the image forming system (700).

[0370] The wavefront sensor (500) can measure wavefront information of incident light using the Shack-Hartmann method.

[0371] The wavefront sensor (500) can provide the measured wavefront information to the high-speed control unit (630).

[0372] The high-speed control unit (630) can generate a driving signal for at least one of the electroactive polymer layer (140) and the phase change material metasurface (160) based on a rapidly changing wavefront error.

[0373] The high-speed control unit (630) can control the amount of deformation of the electroactive polymer layer (140) by providing an EAP driving signal to the electroactive polymer layer (140).

[0374] The high-speed control unit (630) can provide a PCM driving signal to the phase change material metasurface (160) to control the phase change state or optical characteristics of the phase change material metasurface (160).

[0375] The image forming system (700) can form an infrared image using light that has passed through the optical system (300).

[0376] The infrared detector (400) can detect an infrared image formed by the image forming system (700) and provide image information corresponding to the detected image to the low-speed control unit (640).

[0377] The low-speed control unit (640) can calculate the wavefront error or correction amount according to the phase diversity method or image-based error evaluation.

[0378] The correction information calculated by the low-speed control unit (640) can be used to adjust the reference value, reference wavefront, or correction condition of the high-speed control loop.

[0379] The control management unit (650) manages the control status of the high-speed control unit (630) and the low-speed control unit (640) and can coordinate the operation of the two control loops.

[0380] The control management unit (650) can adjust one or more of the control gain, reference value, correction range, driving priority, and mode distribution of the high-speed control unit (630) and the low-speed control unit (640).

[0381] The control management unit (650) can control high-speed correction for rapidly changing wavefront errors and low-speed correction for relatively slowly changing reference errors or non-common optical path errors to be performed in cooperation with each other.

[0382] Accordingly, the optical characteristics of the active sphere infrared window (100) can be stably controlled while suppressing unnecessary control interference or overlap of correction amounts that may occur between the high-speed control loop and the low-speed control loop.

[0384] Next, the correction of images and wavefronts is explained.

[0385] FIG. 9 is a diagram schematically illustrating the correction process of an infrared image through the estimation and correction of wavefront error according to an embodiment of the present invention, as well as the image and wavefront state before and after correction.

[0386] In the degraded image acquisition step (901), a degraded image may be acquired due to aerodynamic heating, aerodynamic optical distortion, or thermomechanical deformation of the window.

[0387] In the wavefront error estimation step (902), the wavefront error can be estimated using the Sharke-Hartman method, the phase diversity method, or a combination thereof.

[0388] In the correction signal generation step (903), a correction signal for at least one of the electroactive polymer and the phase change material can be generated based on the estimated wavefront error.

[0389] In the adaptive optical element driving step (904), at least one of the electroactive polymer and the phase change material can be driven.

[0390] In the corrected image acquisition step (905), an image with optical wavefront correction applied can be acquired.

[0391] The degraded image (910) may include low resolution, blur, or distortion before correction.

[0392] The estimated wavefront error (920) may represent a spatial phase distribution obtained by a wavefront sensor or an image-based algorithm.

[0393] The corrected wavefront (930) may represent the residual wavefront error after being corrected by the electroactive polymer and the phase change material.

[0394] The corrected image (940) may have improved resolution or clarity compared to the degraded image (910).

[0396] Next, the response to low and high temperature environments is explained.

[0397] The electroactive polymer layer (140) can be configured to maintain flexibility even in a low-temperature environment at high altitudes.

[0398] In one embodiment, the glass transition temperature Silicone-based copolymers or silicone-based materials containing plasticizers with a temperature of about 180 K or less may be used.

[0399] The composition of the phase change material can be adjusted to suppress unintended self-crystallization caused by aerodynamic heating.

[0400] For example, crystallization temperature by adjusting the Sb ratio or Se doping, etc. It can be set to approximately 550 K or higher.

[0401] Accordingly, it is possible to distinguish between temperature changes due to aerodynamic heating and the intentional operation of phase change materials.

[0403] Next, the control method of the active ball-shaped infrared window is described.

[0404] FIG. 10 is a flowchart schematically illustrating a control method for controlling the optical properties of an active spherical infrared window using an electroactive polymer part and a phase change material metasurface according to one embodiment of the present invention.

[0405] In the step of passing infrared rays (S100), infrared rays incident from the outside can be passed through an infrared-transmitting substrate (110) in which at least a portion is formed as a curved surface.

[0406] In the step of applying electrical input (S200), electrical input can be applied to the electroactive polymer layer (140) using the upper transparent electrode (130) and the lower transparent electrode (150).

[0407] In the step (S300) of deforming the electroactive polymer part, the electroactive polymer layer (140) can be deformed by an applied electrical input.

[0408] In step (S300), one or more of the shape, curvature, spacing, pitch, relative position, or arrangement density of the phase change material metasurface (160) can be changed according to the deformation of the electroactive polymer layer (140).

[0409] In the step (S400) of controlling the phase change state, the phase change material included in the phase change material metasurface (160) can be switched between at least two states among an amorphous state, a crystalline state, or an intermediate state.

[0410] Accordingly, one or more of the refractive index, absorption rate, transmittance, reflectance, phase delay, or resonance characteristics can be changed.

[0411] The step of providing thermal energy (S500) can be performed optionally.

[0412] In step (S500), thermal energy can be provided to all or part of the phase change material metasurface (160) using a heating unit (180).

[0413] The step of suppressing heat transfer (S510) can be performed optionally.

[0414] In step (S510), heat transferred from the infrared-transmitting substrate (110) or the heating unit (180) to the electroactive polymer layer (140) can be suppressed by using the first thermal insulation unit (120) or the second thermal insulation unit (170).

[0415] In the step (S600) of controlling the change in optical properties, the deformation of the electroactive polymer part and the change in optical properties of the phase change material metasurface (160) can be controlled independently or in combination.

[0416] In the step (S700) of controlling the optical characteristics of infrared light, at least one of the focal length, optical power, phase, wavefront, and transmission characteristics of infrared light can be controlled.

[0417] If necessary, one or more of the reflectance, absorption rate, resonance characteristics, and spectral pass characteristics can also be adjusted.

[0418] If the wavefront error exceeds the allowable range after correction, at least some of steps (S200) to (S700) may be repeated.

[0419] Accordingly, the optical characteristics of the active sphere infrared window (100) can be continuously controlled in a closed-loop manner.

[0421] Next, additional embodiments and variations of the control method will be described.

[0422] The electroactive polymer part can be formed as a single continuous electroactive polymer layer (140).

[0423] In another embodiment, the electroactive polymer part may be divided into multiple regions that are driven independently of each other.

[0424] When multiple electroactive polymer regions are controlled independently, not only uniform area deformation but also asymmetric deformation, local curvature changes, or astigmatism correction can be achieved.

[0425] The phase change material metasurface (160) can be formed over the entire area of ​​the electroactive polymer layer (140).

[0426] In another embodiment, a phase change material metasurface (160) may be formed in a portion of the electroactive polymer layer (140).

[0427] Metaatoms can have cylinders, ellipses, square prisms, rings, slots, or complex nanostructures.

[0428] The phase change of the phase change material may be performed not only by Joule heating by the heating unit (180) but also by light pulses, direct current injection, or other forms of energy supply.

[0429] Therefore, the heating unit (180) is not limited to an essential configuration in all embodiments.

[0430] The Shark-Hartmann method and the phase diversity method can each be used independently.

[0431] The Sharke-Hartmann method and the phase diversity method can be combined into a high-speed control loop and a low-speed control loop and used simultaneously.

[0432] For example, rapidly changing aero-optical distortion can be corrected by a high-speed control loop based on the Shack-Hartmann method, and reference errors or non-common optical path errors accumulated over a long period of time can be corrected by a low-speed control loop based on the phase diversity method.

[0433] The Zernike modes distributed in electroactive polymers and phase change materials are not limited to a single fixed classification.

[0434] It is not necessary to allocate lower-order Zernike modes to the electroactive polymer and higher-order Zernike modes to the phase change material.

[0435] The correction subject of a specific Zernike mode may be changed depending on the driving range, response speed, spatial resolution, current driving state, temperature state, and required correction precision of each electroactive polymer and phase change material.

[0436] If a specific Zernike mode can be corrected by both the electroactive polymer and the phase change material, the control unit (600) can distribute the total amount of correction for the mode between the electroactive polymer and the phase change material.

[0437] For example, part of the wavefront error corresponding to one Zernike mode can be corrected by deformation of the electroactive polymer part and part of the remaining part can be corrected by local phase change of the phase change material metasurface (160).

[0438] For the distribution of the correction amount, the minimization of residual wavefront error, the minimization of driving power, the prevention of driving saturation of electroactive polymers or phase change materials, the reduction of response time, the improvement of optical efficiency, the reduction of heat generation, or a combination thereof may be used as the objective function.

[0439] The control unit (600) may additionally distribute the same or similar wavefront correction function to another control axis when one of the electroactive polymer or phase change material approaches the driving limit.

[0440] Accordingly, the electroactive polymer and the phase change material are not limited to a configuration that corrects only completely separated aberration modes, but may also be operated in a cooperative control manner that jointly corrects the same aberration component.

[0441] In the present invention, the type of wavefront sensor, the distribution method of the Zernike mode, the selective operation of multiple infrared bands, and the dual-loop control method may each be applied selectively, and the active spherical infrared window (100) is not limited to necessarily including all of these configurations.

[0442] The deformation of the electroactive polymer part and the change in optical properties of the phase change material metasurface (160) may be controlled based on the measurement results of the wavefront sensor (500), or may be controlled based on a preset control value, flight conditions, temperature information, or an external control command.

[0443] For example, the control unit (600) can select a pre-stored electroactive polymer driving value or phase change material state information corresponding to one or more of the Mach number, flight altitude, angle of attack, flight speed, angular velocity, window temperature, or flight phase.

[0444] Accordingly, closed-loop control using a wavefront sensor (500) is one embodiment of the present invention, and open-loop control using a preset control map or composite control combining open-loop control and closed-loop control may also be applied.

[0445] In addition, dual-band operation of mid-wavelength and long-wavelength infrared, spectrum avoidance functions for responding to infrared countermeasure systems, and diagnostic patterns for phase diversity can be applied independently, and these functions do not all need to be performed simultaneously.

[0446] The active sphere infrared window (100) can be applied to infrared monitoring devices, infrared cameras, infrared laser communication devices, and other optical devices requiring aero-optical correction.

[0448] Next, operational performance and design examples will be described.

[0449] In one embodiment, the residual wavefront error in the mid-wavelength infrared band after aero-optical correction is approximately Controlling to less than can be set as a design goal.

[0450] The electrical focal length adjustment range using in-plane deformation of an electroactive polymer can be set to approximately ±17% in one design example.

[0451] Spectral mode switching between the mid-wave infrared band and the long-wave infrared band can be performed by utilizing the phase change characteristics of the phase change material.

[0452] Phase change operation at the μs level can be implemented depending on the material of the phase change material, the heater structure, and the pulse conditions.

[0453] By utilizing the non-volatile properties of phase change materials, the maintenance power required after the desired optical state is formed can be reduced.

[0454] One design goal may be to set the average power consumption of the active optical unit to less than about 1 W.

[0455] In an embodiment using a high-speed loop of the Sharq-Hartmann method, a closed-loop correction bandwidth of about 1 kHz or more can be targeted.

[0456] The boresight error caused by aerodynamics can be targeted to be less than about 0.1 mrad depending on the correction conditions.

[0457] The volume or mass of the optical unit can be reduced by reducing the mechanical zoom group or separate multiple correction optical elements.

[0458] In one example of a system design, a reduction in volume or mass of about 30% to about 50% compared to the existing optical part can be aimed.

[0459] By utilizing dual-band operation of mid-wave infrared and long-wave infrared, the infrared characteristics of a target can be acquired across multiple wavelength bands and used for target identification.

[0460] In an infrared countermeasure system environment, specific interference wavelengths can be selectively suppressed by altering the spectral characteristics of the phase change material.

[0461] The active ball-shaped infrared window (100) may also be used as an optical configuration for correcting aero-optical distortion occurring in a high-speed flight environment at Mach 3 to Mach 5.

[0462] When using wavefront sensor-based closed-loop control, manufacturing tolerances, drift due to long-term operation, or optical errors due to environmental changes can be actively compensated.

[0463] In this way, the active spherical infrared window (100) can actively adjust one or more of the focal length, optical power, phase, wavefront, and transmission characteristics of infrared rays in response to aerodynamic heating and aerodynamic optical distortion occurring in a high-speed flight environment by integrating the electromechanical deformation of an electroactive polymer and the variable optical characteristics of a phase change material metasurface (160) into a single spherical optical structure.

[0464] In addition, since electroactive polymers and phase change materials can be controlled independently or the correction capabilities of the two control axes can be combined, a wide correction range and high spatial resolution can be secured simultaneously.

[0466] Although various preferred embodiments of the present invention have been described above with some examples, the descriptions of various embodiments described in the "Specific details for carrying out the invention" section are merely illustrative, and those skilled in the art to which the present invention pertains will understand that the present invention can be modified in various ways or equivalent embodiments can be carried out based on the above description.

[0467] In addition, since the present invention can be implemented in various other forms, the present invention is not limited by the description above. The above description is provided merely to make the disclosure of the present invention complete and to fully inform those skilled in the art of the scope of the present invention, and it should be understood that the present invention is defined only by each claim of the claims. Explanation of the symbols

[0469] 10: Aircraft nose cone 20 : Aerodynamic heating environment 100: Active ball-type infrared window 110: Infrared-transmitting substrate 111 : Diamond Carbon (DLC) Hardcoat 120 : 1st thermal insulation section 130: Upper transparent electrode 140 : Electroactive polymer layer 150: Lower transparent electrode 160 : Phase change material metasurface 161 : 1st Metacell (M Cell) 162 : 2nd Metacell (L Cell) 170 : Second thermal insulation section 180 : Heating part 190: Frame or bag part 200 : Gimbal 300 : Optical system 400 : Infrared detector 500 : Wavefront sensor 510: Lenslet Array 520 : Detector for Shack-Hartmann wavefront sensor 600 : Control unit 610: High-voltage amplifier 620: Heater drive unit 630: High-speed control unit 640 : Low-speed control unit 650 : Control Management Unit 700 : Image forming system 901: Degraded image acquisition stage 902: Wavefront Error Estimation Step 903: Correction signal generation step 904: Adaptive optical element driving step 905: Corrected image acquisition step 910 : Degraded image 920 : Estimated wavefront error 930 : Corrected wavefront 940 : Corrected image

Claims

Claim 1 An active spherical infrared window having an electroactive polymer and a phase change material metasurface, characterized by comprising: an infrared-transmitting substrate that transmits infrared rays and at least a portion of which is formed as a curved surface; an electroactive polymer part configured to be deformable according to an electrical input and disposed on the optical path of infrared rays passing through the infrared-transmitting substrate; a phase change material metasurface having a plurality of meta-atoms including a phase change material whose optical properties change according to a phase change and disposed on a common optical path with the electroactive polymer part; and a control unit that controls the electrical input applied to the electroactive polymer part and the phase change state of the phase change material metasurface, respectively, to actively control the optical properties of infrared rays passing through the infrared-transmitting substrate. Claim 2 An active spherical infrared window having an electroactive polymer and a phase change material metasurface, characterized in that, in claim 1, the electroactive polymer part and the phase change material metasurface are stacked or bonded together to form an integral structure, and one or more of the shape, curvature, and arrangement of the plurality of meta-atoms of the phase change material metasurface change according to the deformation of the electroactive polymer part. Claim 3 An active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein, in claim 1, the electroactive polymer part comprises: an electroactive polymer layer that deforms according to an electrical input; and a pair of electrodes disposed between the electroactive polymer layer and applying an electric field to the electroactive polymer layer. Claim 4 An active spherical infrared window having an electroactive polymer and phase change material metasurface, wherein at least one of the pair of electrodes comprises a transparent electrode disposed in an area overlapping with the infrared optical path, and the transparent electrode comprises one or more of graphene, carbon nanotubes, transparent conductive oxides, and conductive nanostructures. Claim 5 An active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein, in claim 1, each of the plurality of meta-atoms of the phase change material metasurface comprises a phase change material, and the phase change material is capable of switching between at least two of an amorphous state, a crystalline state, and an intermediate state between the amorphous state and the crystalline state, and one or more of the refractive index, absorption rate, transmittance, reflectance, phase retardation, and resonance characteristics of the plurality of meta-atoms change according to the change of the state. Claim 6 An active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein, in claim 5, it further comprises a heating unit that provides thermal energy to the phase change material metasurface to induce a phase change of the phase change material, and the heating unit is configured to selectively heat all of the plurality of meta-atoms or some of the plurality of meta-atoms. Claim 7 An active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein, in claim 6, it further comprises a thermal insulating member disposed between the infrared-transmitting substrate and the electroactive polymer member, between the electroactive polymer member and the phase change material metasurface, and between the phase change material metasurface and the heating member, wherein the thermal insulating member is configured to suppress the transfer of at least one of the heat transmitted through the infrared-transmitting substrate and the heat generated from the heating member to the electroactive polymer member. Claim 8 An active spherical infrared window having an electroactive polymer and a phase change material metasurface, characterized in that, in claim 1, one or more of the spacing, pitch, relative position, arrangement density, and curvature of the phase change material metasurface between the plurality of meta-atoms of the electroactive polymer part are changed by deformation of the electroactive polymer part, and accordingly, one or more of the focal length, optical power, phase distribution, and wavefront for infrared rays passing through the infrared-transmitting substrate are controlled. Claim 9 An active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein, in claim 1, the control unit controls the amount of deformation of the electroactive polymer by adjusting the electrical input applied to the electroactive polymer, controls the phase change state of the phase change material included in a part region of the phase change material metasurface, and controls one or more of the focal length, optical power, phase, wavefront, and transmission characteristics of the infrared light by controlling the deformation of the electroactive polymer and the change in optical characteristics of the phase change material metasurface independently or in combination. Claim 10 A method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface, characterized by comprising: a step of passing infrared rays through an infrared-transmitting substrate that transmits infrared rays and at least a portion of which is formed as a curved surface; a step of applying an electrical input to an electroactive polymer portion disposed on the optical path of infrared rays passing through the infrared-transmitting substrate to deform the electroactive polymer portion; a step of controlling the phase change state of a phase change material metasurface having a plurality of meta-atoms disposed on a common optical path with the electroactive polymer portion and including a phase change material whose optical properties change according to the phase change; and a step of actively controlling the optical properties of infrared rays passing through the infrared-transmitting substrate by controlling the deformation of the electroactive polymer portion and the phase change state of the phase change material metasurface, respectively. Claim 11 A method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein, in claim 10, the electroactive polymer part and the phase change material metasurface are stacked or bonded together to form an integral structure, and the step of deforming the electroactive polymer part includes the step of changing one or more of the shape, curvature, and arrangement of the plurality of meta-atoms of the phase change material metasurface according to the deformation of the electroactive polymer part. Claim 12 A method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein, in claim 10, the electroactive polymer part comprises: an electroactive polymer layer that is deformed according to an electrical input; and a pair of electrodes disposed between the electroactive polymer layer; and the step of deforming the electroactive polymer part comprises applying an electrical input to the pair of electrodes to form an electric field in the electroactive polymer layer and deforming the electroactive polymer layer by the electric field. Claim 13 A method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein at least one of the pair of electrodes comprises a transparent electrode disposed in an area overlapping with the infrared light path, and the transparent electrode comprises one or more of graphene, carbon nanotubes, transparent conductive oxides, and conductive nanostructures. Claim 14 A method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein the step of controlling the phase change state of the phase change material metasurface comprises the step of switching the phase change material included in each of the plurality of meta-atoms between at least two states among an amorphous state, a crystalline state, and an intermediate state between the amorphous state and the crystalline state, and changing one or more of the refractive index, absorption rate, transmittance, reflectance, phase retardation, and resonance characteristics of the plurality of meta-atoms according to the switching of the states. Claim 15 A method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein, in claim 14, the step of controlling the phase change state of the phase change material metasurface comprises: a step of providing thermal energy to the phase change material metasurface using a heating unit; and a step of selectively heating all of the plurality of meta-atoms or some of the plurality of meta-atoms by the thermal energy to induce a phase change of the phase change material. Claim 16 A method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein, in claim 15, a thermal insulating member is disposed between the infrared-transmitting substrate and the electroactive polymer member, between the electroactive polymer member and the phase change material metasurface, and between the phase change material metasurface and the heating member, and further comprising the step of using the thermal insulating member to suppress the transfer of at least one of the heat transmitted through the infrared-transmitting substrate and the heat generated from the heating member to the electroactive polymer member. Claim 17 A method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein the step of deforming the electroactive polymer part comprises changing one or more of the spacing, pitch, relative position, arrangement density, and curvature of the phase change material metasurface between the plurality of meta atoms of the phase change material metasurface by the deformation of the electroactive polymer part, and controlling one or more of the focal length, optical power, phase distribution, and wavefront for infrared rays passing through the infrared-transmitting substrate according to the arrangement of the plurality of meta atoms or the change in curvature of the phase change material metasurface. Claim 18 A method for controlling an active spherical infrared window having an electroactive polymer and a phase change material metasurface, wherein the step of actively controlling the optical properties of the infrared radiation comprises: a step of controlling the amount of deformation of the electroactive polymer by controlling the electrical input applied to the electroactive polymer; a step of controlling the phase change state of the phase change material included in a part region of the phase change material metasurface; and a step of controlling one or more of the focal length, optical power, phase, wavefront, and transmission properties of the infrared radiation by controlling the deformation of the electroactive polymer and the change in optical properties of the phase change material metasurface independently or in combination. Claim 19 An active sphere infrared window having an electroactive polymer and a phase change material metasurface, characterized by being controlled by a control method for an active sphere infrared window having an electroactive polymer and a phase change material metasurface according to any one of claims 10 to 18.

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