Spectrum-space coordinated regulation multispectral stealth device

Abstract

The invention discloses a spectrum-space coordinated regulation multispectral stealth device. The device structurally comprises an infrared selective radiation layer, a retroreflection structure layer and a microwave absorption layer from top to bottom in sequence, the infrared selective radiation layer has the transmissivity of more than 0.5 in a solar spectral band, the radiance of the infrared selective radiation layer in an infrared atmospheric window is lower than 0.5, and the radiance of the infrared selective radiation layer in an infrared non-atmospheric window is higher than 0.5; the reflectivity of the retroreflection structure layer to the solar spectrum wave band is higher than 0.6, and the final emergent light and the incident light are parallel but opposite in direction. The device provided by the invention can simultaneously realize visible light / short wave infrared stealth, infrared stealth and heat dissipation optimization, and a multiband compatible function of microwave stealth.

Description

Technical Field

[0001] This invention relates to the field of multispectral stealth technology, specifically to a multispectral compatible stealth device that integrates visible-near-infrared-shortwave infrared retroreflection stealth, mid-far-infrared selective radiation heat dissipation and stealth, and microwave absorption. Background Technology

[0002] With the rapid development of ground-based detection technology, high-value aerospace targets face severe threats from multi-band detection systems such as radar, visible light, and infrared. Improving their all-band survivability has become an urgent priority. However, under the existing technological system, there is a profound and irreconcilable fundamental conflict between the stealth requirements of aerospace targets in different bands and their thermal management requirements in the vacuum environment of space.

[0003] In the visible to short-wave infrared solar radiation band, space targets face a dilemma between "stealth" and "heat dissipation." Traditional visible-near-infrared-short-wave infrared stealth schemes typically require the target surface to have extremely low solar reflectivity (i.e., high absorption) to blend into the deep space background. However, aerospace targets are in a vacuum environment and cannot dissipate heat through thermal conduction and convection. If the surface has a high absorption rate for solar radiation with a power density as high as 1353 W / m², it will cause the device temperature to rise sharply and even exceed the normal operating range.

[0004] In the mid-infrared band, stealth and heat dissipation also present a trade-off. To counter infrared imaging detection, the target surface needs to have low emissivity in the atmospheric window bands (3-5 μm and 8-14 μm). However, traditional low-emissivity stealth materials block the path for aerospace targets to radiate waste heat outwards, leading to overheating. While existing selectively radiating materials attempt to utilize the 5-8 μm band for heat dissipation, the heat dissipation capacity of this narrow band is often insufficient under low-temperature conditions or high thermal loads, failing to fully utilize the opaque very long infrared band (14-30 μm) for efficient heat dissipation.

[0005] Stealth solutions in the microwave band typically rely on radar-absorbing materials, but infrared and optical stealth layers are often made of materials that block radar waves, making it difficult to achieve electromagnetic wave compatibility in multi-layered structures.

[0006] Therefore, there is an urgent need to develop a new type of device that can overcome the limitations of single-spectral modulation, and achieve the rejection of solar heat and the elimination of ground reflection signals through the coordinated modulation of spectral selectivity and spatial distribution of light field, while also taking into account infrared stealth, efficient radiative heat dissipation and radar stealth. Summary of the Invention

[0007] This invention aims to resolve the fundamental conflict between stealth and thermal management in existing aerospace targets, as well as the incompatibility of multispectral stealth, by providing a spectral-space coordinated multispectral stealth device for aerospace targets. This device cleverly combines spectral screening and spatial light field reconstruction technologies through layered design and material optimization.

[0008] The spectral-space coordinated control multispectral stealth device for aerospace targets provided by this invention comprises, from top to bottom, an infrared selective radiation layer, an antireflective structure layer, and a microwave absorption layer. The infrared selective radiation layer, as the outermost structure, primarily performs spectral selection and infrared radiation thermal management functions; the antireflective structure layer, located in the middle, is responsible for spatial control of the light field in the solar radiation band; and the microwave absorption layer, located at the bottom, is responsible for radar wave absorption.

[0009] A spectral-space coordinated multispectral stealth device for aerospace targets comprises, from top to bottom, an infrared selective radiation layer, an antireflective structure layer, and a microwave absorption layer. The infrared selective radiation layer has a transmittance of over 0.5 in the solar spectrum, an emissivity of less than 0.5 in the infrared atmospheric window, and an emissivity of over 0.5 in the infrared non-atmospheric window. The antireflective structure layer has a reflectivity of over 0.6 in the solar spectrum, and the outgoing light rays are parallel to the incident light rays but in opposite directions.

[0010] The infrared selective radiation layer, as the outermost layer of the device, primarily performs spectral screening and infrared radiation thermal management functions. This layer consists of a transparent substrate and alternating layers of low-refractive-index and high-refractive-index materials deposited on the substrate in a multilayer structure. This invention is not limited to specific material combinations or a fixed number of layers; any dielectric material that exhibits high transmittance in the solar spectral band (0.4-2.5 μm) and selective radiation characteristics in the infrared band is applicable. By optimizing the material type, thickness, and number of stacked layers, and utilizing the photonic crystal bandgap effect and intrinsic absorption characteristics of the material, this layer can achieve low emissivity in the infrared atmospheric window band (3-5 μm and 8-14 μm) to suppress thermal radiation signals and counteract infrared imaging detection, while simultaneously achieving high emissivity in the infrared non-atmospheric window band (5-8 μm and 14-30 μm) for radiative heat dissipation, thus achieving efficient thermal management.

[0011] The retroreflective structure layer, located below the infrared selective radiation layer, is used to receive solar spectral radiation transmitted through the top layer. This layer employs an optical structure with retroreflective function, utilizing geometric optical properties to reflect incident light back along its original path towards the light source. Through this spatial manipulation, most of the solar radiation energy is repelled back into space, preventing the device from overheating; simultaneously, since ground-based observation stations are typically located away from the direction of the solar light source, the intensity of the reflected signal received from the ground is significantly reduced, achieving "dark target" stealth for Earth-based optics.

[0012] Preferably, the retroreflective structure layer is made of a dielectric material that is transparent to microwaves and has low loss in the visible-near-infrared-shortwave infrared band, and its structure is a micro-prism array. More preferably, to maximize retroreflection efficiency and eliminate ineffective reflection areas, each unit in the micro-prism array adopts a full prism (high retroreflectivity) structure, and the micro-prism array itself is a total internal reflection micro-prism array. Unlike traditional truncated microprisms, the full prism structure eliminates the non-working area (dead zone) through geometric optimization. Its characteristic is that each reflection unit is microscopically arranged in a rectangular close-packed configuration, and each unit is composed of specific polygonal surfaces, each containing three mutually perpendicular reflective surfaces, thereby achieving a near 100% theoretical area utilization rate. Preferably, each micro-prism unit in the total internal reflection micro-prism array includes three mutually perpendicular total internal reflection mirror structures. More preferably, each micro-prism unit is arranged in a rectangular close-packed configuration, and each contains mutually perpendicular total internal reflection mirror structures.

[0013] The microwave absorbing layer is located at the bottom of the device and uses an absorbing material optimized for a specific radar band (such as the Ku band). Since the upper infrared selective radiation layer (dielectric film) and the antireflective structure layer (polymer dielectric) are both made of microwave-transparent materials, radar waves can penetrate the first two layers and be captured by the bottom microwave absorbing layer and converted into heat energy dissipation.

[0014] Preferably, the infrared selective radiation layer consists of a microwave-transparent substrate and a multilayer structure consisting of alternating layers of low-refractive-index and high-refractive-index materials deposited on the substrate.

[0015] Preferably, the low refractive index material includes one or more of YbF3, LaF3, MgF2, BaF2, CaF2, and SiO2; the high refractive index material includes one or more of ZnS, ZnSe, HfO2, SnO2, MgO, ZrO2, Y2O3, and YSZ (yttrium-stabilized zirconium oxide).

[0016] Preferably, the infrared selective radiation layer has a transmittance of 0.6 or higher in the solar spectrum, an emissivity of less than 0.4 in the infrared atmospheric window, and an emissivity of more than 0.8 in the infrared non-atmospheric window.

[0017] Preferably, the substrate material in the infrared selective radiation layer is one or more of the following: silicon dioxide, Al2O3, MgF2, BaF2, CaF2, PET, PMMA, colorless PI, colorless PE, colorless PP, and colorless PDMS. The thickness of the substrate is generally 50 μm or more, and generally does not exceed 5000 μm.

[0018] As a preferred embodiment, in the infrared selective radiation layer: the low refractive index material is ytterbium fluoride, the high refractive index material is zinc sulfide, the total number of layers is 10 to 30, and the layer thickness is 10 nm to 3 μm.

[0019] As a preferred embodiment, the infrared selective radiation layer has the following structure from top to bottom: YbF3 (100~200 nm), ZnS (20~30 nm), YbF3 (15~25 nm), ZnS (1200~1800 nm), YbF3 (30~40 nm), ZnS (15~25 nm), YbF3 (500~600 nm), ZnS (400~500 nm), YbF3 (500~600 nm), ZnS (1500~2000 nm), YbF3 (650~750 nm). , ZnS(300~400nm), YbF3(650~750nm), ZnS(1200~1600nm), YbF3(30~40nm), ZnS(15~25nm), Y bF3(900~1000nm), ZnS(5~15nm), YbF3(700~800nm), ZnS(1000~1500nm), YbF3(950~1050nm).

[0020] Preferably, the retroreflective structure layer is made of a dielectric material that is transparent to microwaves and has low loss in the visible-near-infrared-shortwave infrared band, and its structure is a microprism array.

[0021] Preferably, the microprism array is a full prism array (i.e., a total reflection prism).

[0022] Preferably, the retroreflective structural layer material is polymethyl methacrylate, polydimethylsiloxane, or a cyclic olefin polymer.

[0023] Verification has shown that the device employing this invention exhibits extremely low reflectivity (below 0.3) in the specular reflection direction within the solar radiation band, allowing it to blend better into the background environment and further meeting stealth requirements. Simultaneously, the retroreflective structure layer ensures that most solar radiation waves return along their original path, thus solving the problem of temperature increases caused by solar radiation and avoiding the risk of signal capture. In the infrared band, the device achieves emissivity below 0.26 in the mid-wave infrared atmospheric window (3-5 μm) and 0.35 in the long-wave infrared atmospheric window (8-14 μm), effectively reducing the probability of aerospace targets being locked onto by infrared detectors. More importantly, in terms of radiative heat dissipation, the device achieves emissivity exceeding 0.8 in the 5-8 μm band and even exceeding 0.87 in the very long-wave infrared band (14-30 μm). This allows aerospace targets to utilize these atmospherically opaque bands to establish efficient radiative heat dissipation channels, expelling heat towards the 3K cosmic background and maintaining thermal balance. The device of this invention is also used in the microwave band. With an average absorption rate as high as 0.94, the radar cross section is significantly reduced.

[0024] In summary, the device proposed in this invention can simultaneously achieve multi-band compatibility functions such as visible light / shortwave infrared stealth, infrared stealth and heat dissipation optimization, and microwave stealth. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the layered structure of the multispectral compatible stealth device.

[0026] In the diagram, 1 – Infrared selective radiation layer; 2 – Retroreflective structure layer; 3 – Microwave absorption layer;

[0027] Figure 2 This is a physical image of the multispectral compatible stealth device;

[0028] Figure 3 The images show a microstructure (C), a three-dimensional structure (A), and a top view (B) of the retroreflective structure layer in the multispectral compatible stealth device.

[0029] Figure 4 The spectroscopic reflectance spectrum of the multispectral compatible stealth device in the solar spectral band is shown.

[0030] Figure 5 The infrared emissivity spectrum of the multispectral compatible stealth device is shown below.

[0031] Figure 6 The image shows the absorption spectrum of the multispectral compatible stealth device in the microwave Ku band. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be further described in detail below with reference to specific embodiments.

[0033] This invention proposes a spectral-space coordinated multispectral stealth device for aerospace targets. Its core lies in the hierarchical design of the physical structure, which decouples and separately processes electromagnetic waves in different bands. The device's physical structure consists of three tightly bonded functional parts from top to bottom: an infrared selective radiation layer, an anti-reflection structure layer, and a microwave absorption layer. A schematic diagram of its structure is shown below. Figure 1 As shown.

[0034] Example 1

[0035] The physical image of the prepared spectral-spatial synergistic modulated multispectral stealth device is shown below. Figure 2 As shown.

[0036] The outermost infrared selective radiation layer is designed based on multilayer interferometry theory. In this embodiment, after optimized calculations, ytterbium fluoride (YbF3) was selected as the low-refractive-index material, and zinc sulfide (ZnS) was selected as the high-refractive-index material. A total of 21 layers were alternately deposited on a silicon dioxide (SiO2) substrate to form a stacked structure. This specific material combination and layer design aims to achieve high solar transmittance while precisely forming high-reflection bands (i.e., low radiation) in the 3-5 μm and 8-14 μm wavelengths, while utilizing phonon absorption and interference enhancement in the 5-8 μm and 14-30 μm wavelengths to achieve high radiation.

[0037] As a preferred embodiment, the specific materials and thicknesses of each layer from top to bottom (the last layer being connected to the substrate surface) are as follows: YbF3 (126nm), ZnS (22nm), YbF3 (21nm), ZnS (1658nm), YbF3 (37nm), ZnS (19nm), YbF3 (585nm), ZnS (438nm), YbF3 (515nm), ZnS (1766nm), YbF3 (683nm), ZnS (335nm), YbF3 (684nm), ZnS (1477nm), YbF3 (33nm), ZnS (18nm), YbF3 (938nm), ZnS (11nm), YbF3 (744nm), ZnS (1330nm), YbF3 (990nm).

[0038] Testing revealed that the meticulously designed infrared selective radiation layer exhibited excellent spectral modulation performance. In the solar spectral band (AM0 standard), the film achieved a transmittance of 0.639 (63.9%), ensuring that most of the solar energy can penetrate this layer and reach the underlying retroreflective layer for processing, rather than being absorbed or specularly reflected at the surface.

[0039] It should be noted that this is only a preferred embodiment of the present invention. In practical applications, other infrared-transparent materials (such as LaF3 / MgF2 / BaF2 / CaF2 / SiO2 for low-refractive-index materials; and ZnSe / HfO2 / SnO2 / MgO / ZrO2 / Y2O3 / YSZ for high-refractive-index materials) can be selected and the number of layers adjusted to achieve similar spectral modulation effects. The substrate thickness is 50 μm. Besides silicon dioxide, other materials transparent to visible light and microwaves can also be selected for the substrate, such as Al2O3 / MgF2 / BaF2 / CaF2 / PET / PMMA / colorless PI / PE / PP / PDMS, etc.

[0040] Immediately below the infrared selective radiation layer is the retroreflective structure layer. In this embodiment, optical-grade polymethyl methacrylate (PMMA), which is low-loss and microwave-transparent in the visible-near-infrared-shortwave infrared band, was selected as the substrate, and a total prism (total internal reflection microprism) array was fabricated using a micro / nano imprinting process. For example... Figure 3 The microscopic image shown in C reveals that the structure is composed of countless tiny reflective units arranged closely together. See also Figure 3 In the diagrams A and B (where B is a top view of A), each total prism reflective unit exhibits a closely spaced rectangular arrangement in its microscopic geometry. Internally, each unit comprises a three-dimensional structure consisting of three mutually perpendicular mirror surfaces (a, b, c). After three total internal reflections, the light ultimately returns in a direction completely parallel to the incident light. Simultaneously, a rectangular patchwork is formed by setting three triangular (d, e, f) surface structures. This unique geometric patchwork is a significant feature of the total prism structure. Mathematically and optically, it eliminates the ineffective reflection dead zone caused by the truncated angles of traditional corner prisms, increasing the utilization rate of the effective retroreflection area to nearly 100%. When sunlight passes through the top layer of the membrane and enters the PMMA total prism structure, the light undergoes three total internal reflections on the three mutually perpendicular internal reflective surfaces. The final outgoing light is parallel to the incident light but in the opposite direction, returning towards the sun. In this embodiment, the retroreflective structure layer directly uses a commercially available photoelectric switch sensor reflector.

[0041] The bottom layer is the microwave absorbing layer. In this embodiment, a commercially available, mature Ku-band absorbing patch was directly selected. Since the upper YbF3 / ZnS dielectric film and PMMA prism layer are both low dielectric loss materials, they act as "transparent windows" for microwaves, allowing radar waves to reach and be absorbed by the bottom absorbing material.

[0042] In actual manufacturing, the first and second layers from bottom to top are purchased directly and fixed by bonding with corresponding adhesives; the outermost layer is prepared by electron beam evaporation coating. Furthermore, the substrate film is first fixed to the top surface of the second layer, and then the electron beam evaporation coating process is used to stack the layers one by one to obtain the device structure of the present invention.

[0043] Finally, the overall full-band performance of the fabricated spectral-spatial synergistically modulated multispectral stealth device was tested, and the test results are as follows: Figure 4 , Figure 5 and Figure 6 As shown.

[0044] The device was tested using a spectrophotometer with an integrating sphere in the solar radiation band. For example... Figure 4 As shown, thanks to the highly efficient retroreflection effect of the all-prism structure (reflecting most of the light back to the source rather than undergoing specular reflection), the overall device has extremely low reflectivity in the specular reflection direction, with an average specular reflectivity of only 0.274. This means that from the perspective of a ground-based observation station, the device appears as an extremely dark target, and most of the solar energy is not absorbed by the device but is repelled back into space.

[0045] In the infrared band, the emissivity of the device was measured using Fourier transform infrared spectroscopy (FTIR). For example... Figure 5 As shown, the top-layer YbF3 / ZnS multilayer film system plays a crucial role. This device achieves an emissivity of 0.26 in the mid-wave infrared atmospheric window (3-5 μm) and 0.35 in the long-wave infrared atmospheric window (8-14 μm), effectively reducing the probability of aerospace targets being locked onto by infrared detectors. More importantly, in terms of radiative heat dissipation, the device exhibits an emissivity as high as 0.8 in the 5-8 μm band and an even higher emissivity of 0.87 in the very long-wave infrared band (14-30 μm). This allows aerospace targets to utilize these atmospherically opaque bands to establish efficient radiative heat dissipation channels, expelling heat towards the 3K cosmic background and maintaining thermal equilibrium.

[0046] In the microwave band, the reflection loss of the device in the Ku band was tested using a vector network analyzer in a microwave anechoic chamber. For example... Figure 6 As shown, due to the wave transmittance of the first two layers and the strong absorption of the bottom layer, the overall device exhibits excellent wave absorption performance in the Ku band, with an average absorption rate as high as 0.937, thereby significantly reducing the radar cross section.

[0047] In summary, the data from this embodiment fully demonstrates that the device proposed in this invention can simultaneously achieve multi-band compatibility functions such as visible light / shortwave infrared stealth, infrared stealth and heat dissipation optimization, and microwave stealth.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. The present invention is not limited to the examples described above. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A spectral-spatial synergistic modulated multispectral stealth device, characterized in that, Structurally, from top to bottom, it comprises an infrared selective radiation layer, an antireflective structure layer, and a microwave absorption layer. The infrared selective radiation layer has a transmittance of more than 0.5 in the solar spectrum, an emissivity of less than 0.5 in the infrared atmospheric window, and an emissivity of more than 0.5 in the infrared non-atmospheric window. The antireflective structure layer has a reflectivity of more than 0.6 in the solar spectrum, and the final outgoing light is parallel to the incident light but in the opposite direction.

2. The spectral-spatial synergistic control multispectral stealth device according to claim 1, characterized in that, The infrared selective radiation layer consists of a microwave-transparent substrate and a multilayer structure consisting of alternating layers of low-refractive-index and high-refractive-index materials deposited on the substrate.

3. The spectral-spatial synergistic control multispectral stealth device according to claim 2, characterized in that, Low refractive index materials include one or more of YbF3, YF3, LaF3, MgF2, BaF2, CaF2, and SiO2; high refractive index materials include one or more of ZnS, ZnSe, HfO2, SnO2, MgO, ZrO2, Y2O3, and YSZ.

4. The spectral-spatial synergistic control multispectral stealth device according to claim 2, characterized in that, In the infrared selective radiation layer: the low refractive index material is ytterbium fluoride, the high refractive index material is zinc sulfide, the total number of layers is 10~30, and the layer thickness is 10nm~3μm.

5. The spectral-spatial synergistic control multispectral stealth device according to claim 1, characterized in that, The retroreflective structure layer is made of a dielectric material that is transparent to microwaves and has low loss in the visible-near-infrared-short-wave infrared band, and its structure is a microprism array.

6. The spectral-spatial synergistic modulation multispectral stealth device according to claim 5, characterized in that, The microprism array is a total reflection microprism array.

7. The spectral-spatial synergistic modulation multispectral stealth device according to claim 1 or 6, characterized in that, The retroreflective structural layer material is polymethyl methacrylate, polydimethylsiloxane, or a cyclic olefin polymer.

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