Optical microwave integrated invisibility metasurface structure

Abstract

The application discloses an optical microwave integrated invisibility metasurface structure and relates to the field of camouflage technology, comprising a visible light invisibility structure and / or a microwave invisibility structure. The visible light invisibility structure is configured by constructing a refractive microstructure array with different tilt directions on a transparent substrate to perform path reconstruction regulation on incident visible light and form an optical shielding effect in a preset space area. The microwave invisibility structure is configured by setting a transparent metasurface structure on a target object at a certain distance to perform amplitude and / or phase modulation on incident microwaves, so that the modulated electromagnetic waves and the scattering waves of the target object form phase compensation, thereby reducing the radar scattering cross section. The two invisibility structures can be independently implemented or integrally arranged on the same substrate to realize multi-band electromagnetic regulation functions. The structure form of the application is adjustable, the material and form are flexible, and the application is suitable for multi-band electromagnetic invisibility application.

Description

Technical Field

[0001] This invention relates to the field of camouflage technology, and more specifically to an optical-microwave integrated stealth metasurface structure. Background Technology

[0002] Currently, when visible light shines on an object's surface, it is reflected and scattered, creating a shadow area behind the object that obscures background information and makes it observable. Ideal visible light cloaking should be able to control the propagation path of incident light, allowing it to bypass or redistribute to the target area, thus reducing or eliminating the obscuring effect in space. Some current optical cloaking solutions achieve optical path control through bulk materials or complex refractive index distribution structures, but these typically have large volumes and thicknesses, hindering transparent and lightweight applications.

[0003] In the microwave band, with the development of metamaterials and metasurface technologies, it has become possible to achieve scattering cancellation or wavefront reconstruction by controlling electromagnetic parameters. However, stealth structures based on transformation optics often require anisotropic and non-uniform large-scale material combinations, making them complex to manufacture. They also often adopt the form of completely encapsulating the target object, affecting the normal electromagnetic interaction between the target and the external environment.

[0004] Therefore, it is necessary to provide a stealth solution with a simple structure, transparent installation, and no need to completely cover the target, so that it can achieve optical path reconstruction to form a spatial shielding effect in the visible light band, and achieve amplitude and / or phase modulation of scattered waves in the microwave band to reduce radar cross section, and can be applied independently or integrated on the same substrate as needed to meet the requirements of multi-band stealth applications. Summary of the Invention

[0005] In view of this, the present invention provides an optical-microwave integrated stealth metasurface structure. By constructing a visible light refractive structure and a microwave metasurface control structure on a transparent substrate, it achieves optical path reconstruction stealth in the visible light band and scattering phase compensation stealth in the microwave band. The two structures can be set independently or integrated on the same transparent substrate, thereby achieving multi-band electromagnetic control functions while maintaining the structural thinness and transparency.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An optical-microwave integrated stealth metasurface structure includes: a visible light stealth structure and / or a microwave stealth structure; The visible light stealth structure is used to control the refraction path of incident visible light, thereby creating an optical shielding effect in the target area. The microwave stealth structure is used to modulate the amplitude and / or phase of the incident microwaves to reduce the scattering intensity of the target object in a preset direction. The visible light stealth structure and the microwave stealth structure can be set independently or integrated on the same transparent substrate or different substrates.

[0007] Optionally, the visible light cloaking structure includes an array of refractive microstructures disposed on the surface of a transparent substrate; The refractive microstructure array includes at least two sets of refractive structure units with different tilt directions, which are used to refractively control visible light incident vertically or nearly vertically, so that the light path is reconstructed in space and an optical shielding area is formed behind the refractive structure.

[0008] Optionally, the refractive structure unit is a wedge structure, a prism structure, a sawtooth structure, a gradient refractive index structure, or a combination thereof. Optionally, the two sets of refractive structure units are arranged symmetrically, periodically, or alternately. Optionally, the microwave stealth structure includes a transparent metasurface structure disposed on the outside of the target object and maintaining a preset distance from the target object; The transparent metasurface structure includes an array of electromagnetic control units disposed on the surface of a transparent substrate.

[0009] Optionally, the electromagnetic control unit array is used to modulate the amplitude and / or phase of the incident microwave electromagnetic wave, so that the modulated electromagnetic wave and the scattered wave of the target object form phase compensation, thereby reducing the radar cross section of the target object in a preset direction. Optionally, the electromagnetic control unit is a metal patch structure, a slotted structure, a resonant ring structure, a frequency selective structure, a metasurface unit, or a combination thereof.

[0010] Optionally, the visible light cloaking structure is independently disposed on the transparent substrate, specifically as follows: A refractive microstructure array is disposed on both sides of the transparent substrate; The microwave stealth structure is independently mounted on a transparent substrate, specifically as follows: An array of electromagnetic control units is arranged on both sides of the transparent substrate.

[0011] Optionally, the visible light stealth structure and the microwave stealth structure are integrated on the same transparent substrate, specifically: A refractive microstructure array is disposed on one side of the transparent substrate. An array of electromagnetic control units is disposed on the other side of the transparent substrate. Optionally, the refractive microstructure and the electromagnetic control units are arranged in layers or in combination.

[0012] As can be seen from the above technical solution, compared with the prior art, this invention discloses an integrated optical-microwave stealth metasurface structure, including a visible light stealth structure and / or a microwave stealth structure. The visible light stealth structure constructs an array of refractive microstructures with different tilt directions on a transparent substrate to reconstruct and control the path of incident visible light, forming an optical shielding effect in a predetermined spatial region. The microwave stealth structure sets a transparent metasurface structure at a certain distance above the target object to modulate the amplitude and / or phase of the incident microwaves, causing the modulated electromagnetic wave to achieve phase compensation with the scattered wave from the target object, thereby reducing the radar cross-section. The two stealth structures can be implemented independently or integrated on the same substrate to achieve multi-band electromagnetic control functions. This invention has an adjustable structural form and flexible materials and shapes, making it suitable for multi-band electromagnetic stealth applications. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0014] Figure 1 A schematic diagram of the optical-microwave integrated stealth metasurface structure provided by the present invention; wherein, a is the visible light stealth scenario; b is the microwave stealth scenario; Figure 2 A structural diagram of a single microwave periodic unit provided by the present invention; Figure 3 The present invention provides a simulated near-field electric field distribution and far-field RCS distribution; wherein a and b are the electric field distributions of bare objects at 14 GHz and 15 GHz, respectively; c and d are the electric field distributions with the addition of a stealth layer, respectively; e is the RCS distribution of bare objects at 14 GHz and with the addition of a stealth layer; and f is the RCS distribution of bare objects at 15 GHz and with the addition of a stealth layer. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] This invention discloses an optical-microwave integrated stealth metasurface structure, comprising: a visible light stealth structure and / or a microwave stealth structure; The visible light stealth structure is used to control the refraction path of incident visible light, thereby creating an optical shielding effect in the target area. The microwave stealth structure is used to modulate the amplitude and / or phase of the incident microwaves to reduce the scattering intensity of the target object in a preset direction. The visible light stealth structure and the microwave stealth structure can be set independently or integrated on the same transparent substrate or different substrates.

[0017] In one specific embodiment, the visible light stealth structure includes an array of refractive microstructures disposed on the surface of a transparent substrate; The refractive microstructure array comprises at least two sets of refractive structural units with different tilt directions, used to manipulate the refraction of visible light incident perpendicularly or nearly perpendicularly, causing path reconstruction of the light rays in space and forming an optical shielding region behind the refractive structure. The refractive structural units are wedge-shaped structures, prism structures, sawtooth structures, graded refractive index structures, or combinations thereof. The two sets of refractive structural units are arranged symmetrically, periodically, or alternately.

[0018] Specifically, in the visible light band, this invention uses a transparent thin film or transparent glass as the substrate. A smooth incident surface is formed on one side of the substrate, and a periodic sawtooth-shaped refractive microstructure array is formed on the other side.

[0019] When parallel light is incident perpendicularly from a smooth surface into the interior of a transparent substrate, the light continues to propagate in its original direction within the substrate. When the light reaches the serrated interface on the other side, the direction of the interface normal changes, and according to Snell's law, the light is refracted and deflected at the interface, thereby changing its exit direction and reconstructing the spatial light path.

[0020] Assume the refractive index of the transparent matrix is n 1. The refractive index of the outside air is n 2. The angle between the inclined surface of the sawtooth structure and the normal to the base is... α When light propagates perpendicularly within the matrix and is incident on the inclined interface, its angle of incidence relative to the interface normal is: i i = α According to Snell's Law: n 1·sin i i = n 2·sin i t Then the angle of emission is: i t =arcsin[( n 1 / n 2)·sin α The angle of deflection of the light ray relative to its original direction of propagation is: Δ i= i t - α。 By rationally designing the tilt angle of the sawtooth structure α This can cause the emitted light rays to form a specific deflection distribution in space, creating an optical shielding zone in a certain area of ​​space, thus making objects located in that area invisible to the human eye or imaging system.

[0021] Furthermore, when the sawtooth structure comprises two sets of structural units with opposite tilt directions and arranged symmetrically, a symmetrical optical shielding space can be formed behind the structure, achieving a more stable stealth region. By adjusting the sawtooth height, period, and refractive index parameters, the size and position of the stealth region can be controlled.

[0022] In one specific embodiment, the microwave stealth structure includes a transparent metasurface structure disposed on the outside of the target object and maintaining a preset distance from the target object; The transparent metasurface structure includes an array of electromagnetic control units disposed on the surface of a transparent substrate.

[0023] The electromagnetic control unit array is used to modulate the amplitude and / or phase of the incident microwave electromagnetic wave, so that the modulated electromagnetic wave and the scattered wave of the target object form phase compensation, thereby reducing the radar cross section of the target object in a preset direction.

[0024] The electromagnetic control unit is a metal patch structure, a slotted structure, a resonant ring structure, a frequency selective structure, a metasurface unit, or a combination thereof.

[0025] Specifically, in the microwave band, the target object is placed on a background of an ideal conductor (PEC) flat plate. This invention involves depositing an electromagnetically modulated metasurface thin film on the outer side of the target object. This metasurface is composed of a periodic electromagnetically modulated unit array, which can adopt a slotted resonant structure, a metal patch structure, a ring resonant structure, or a frequency-selective unit form. Through geometric parameter design, a controllable additional phase response is introduced during reflection.

[0026] When no target object is present, the reflection coefficient of the PEC plate for the incident plane wave is: C PEC =-1, and its reflection phase is: PEC = π At this point, the near-field reflected wave is an ideal specular plane wave, and the far-field radar cross section (RCS) is a background scattering from a flat plate. When the target object is placed on the PEC plate, the reflected field is distorted due to geometric protrusions and discontinuities in electromagnetic parameters. The equivalent reflection coefficient of the composite structure formed by the target and the background can be expressed as: C ob =| Cob |·exp[j ob ( f )] in, ob ( f The equivalent reflection phase introduced to the target structure. Typically: ob ( f )≠ π This results in: 1) the near-field reflected wavefront deviating from the ideal plane wave shape; 2) additional scattering components being generated in the far field, increasing the RCS.

[0027] To eliminate the above-mentioned effects, this invention uses metasurface units to modulate the phase of the reflected wave. Let the metasurface operate at a frequency... f The additional modulation phase introduced at the point is m ( f If the total equivalent reflection phase of the composite structure is: total ( f )= ob ( f )+ m ( f ) To make the target object / metasurface composite structure electromagnetically equivalent to a continuous PEC plate, the following phase recovery condition should be satisfied: total ( f =π + 2nπ (where n is an integer). That is: m ( f )=π- ob ( f When the above conditions are met, the equivalent reflection coefficient of the composite structure is: )+2nπ. C total ≈1. At this point, the near-field reflected wavefront is approximately a plane wave; the target's additional scattering is effectively suppressed; the radar cross section is close to the background scattering of a flat plate, achieving microwave stealth effect.

[0028] Due to the equivalent reflection phase of the target structure ob ( f To achieve broadband stealth, the metasurface needs to provide phase compensation characteristics that vary with frequency, so that the aforementioned phase recovery conditions remain valid within a preset frequency band.

[0029] This invention achieves precise design of the reflection phase by adjusting the geometric dimensions, material parameters, and interlayer structure of the metasurface unit, thereby achieving a background-consistent microwave stealth effect while ensuring engineering feasibility.

[0030] In one specific embodiment, the visible light refractive microstructure and the microwave metasurface structure of the present invention can be respectively disposed on different sides of the transparent substrate, or layered and compositely disposed on the same side to achieve structural integration.

[0031] In the visible light band, spatial optical path reconstruction and shielding region construction are achieved through geometric refraction; in the microwave band, near-field equivalent reflection and far-field phase compensation are achieved through electromagnetic resonance. The two mechanisms operate at different frequency bands and have independent control principles, enabling independent or coordinated control across multiple bands.

[0032] Since the wavelengths of visible light and microwaves differ by several orders of magnitude, the scale of the visible light sawtooth structure is much smaller than that of the microwave unit period. The two are independent in electromagnetic response and therefore do not produce significant coupling interference.

[0033] The integrated structure maintains its planar and thin characteristics, and does not need to completely cover the target object. It can create a shielding region in the visible light band through spatial optical path reconstruction, and achieve consistent background scattering suppression in the microwave band through phase recovery. The two control mechanisms have different physical principles and operate in separate frequency bands, enabling independent or collaborative stealth control across multiple bands. This invention features a simple structure, controllable thickness, and can be made transparent. It can form an equivalent virtual plane in the near field and reduce scattering intensity in the far field without completely covering the target object, making it suitable for multi-band electromagnetic stealth applications.

[0034] The following specific embodiments are introduced to further illustrate the structure of the present invention.

[0035] Example 1: Visible Light Stealth Structure

[0036] In the visible light band, this structure achieves systematic reconstruction of the spatial optical path through interface geometric refraction manipulation. One side of the transparent substrate is designed as a smooth incident interface, ensuring that the incident light maintains an approximately parallel propagation state after entering the substrate, thereby avoiding the influence of initial interface perturbations on the light field distribution. The other side of the substrate is constructed with an array of tilted refractive structures arranged periodically or quasi-periodically. This microstructure can take the form of sawtooth, wedge, prism, etc., with a clear interface normal variation, used to control the direction of light propagation.

[0037] like Figure 1 As shown in Figure a, the transparent substrate is a transparent PDMS thin film with a refractive index of n 1. The refractive index of the outside air is n2. One side of the substrate is a smooth incident surface, while the other side is machined into a periodic sawtooth structure. The angle between the inclined surface of the sawtooth structure and the normal to the substrate is... α When light rays are incident perpendicularly onto a transparent substrate from a smooth incident surface, the light rays propagate in a straight line within the substrate. However, when the light rays reach an inclined interface, the direction of the interface normal changes. According to Snell's law, the light rays refract, and the outgoing direction is deflected relative to the original direction. Specifically, let the incident angle be... i i = α Angle of refraction i t It can be calculated using Snell's law:

[0038] n 1·sin i i = n 2·sin i t

[0039] i t = arcsin[( n 1 / n 2)·sin α ]

[0040] Using the above formula, the deflection angle of the outgoing ray relative to the incident ray is Δ. θ = θ t - α By rationally designing the tilt angle of the sawtooth structure α This allows the emitted light rays to form a specific deflection distribution in space. This deflection distribution creates a stable optical shielding zone in space, making objects located in this zone invisible to the human eye or imaging system. Furthermore, when the sawtooth structure is designed to contain two sets of structural units with opposite tilt directions and arranged symmetrically, a symmetrical optical shielding zone can be formed behind the structure, thereby maintaining the consistency of the stealth effect within a certain observation angle range.

[0041] Example 2: Microwave Stealth Structure

[0042] The background of the conductor plate has a reflection coefficient amplitude close to 1 and a reflection phase close to 1. π The incident plane wave exhibits specular reflection characteristics in the near-field region and forms a stable background scattering distribution in the far-field region.

[0043] When a metallic protrusion or dielectric target is placed against this background, an additional reflection phase is introduced due to changes in geometry and discontinuities in electromagnetic parameters. ob ( fThis causes distortion in the reflected wavefront, bending the near-field wavefront and creating additional scattering components in the far field, resulting in an increase in the radar cross section (RCS).

[0044] like Figure 1 As shown in Figure b, a metasurface control layer is set on the outer side of the target. Figure 2 As shown, the metasurface is disposed on a transparent PDMS thin film and consists of a periodically arranged array of electromagnetic units. In this embodiment, the unit form is a resonant metal wire structure, which provides a controllable additional phase during reflection by adjusting the linewidth, length, and period parameters. m ( f ).

[0045] like Figure 3 As shown in Figures a and b, at 14 GHz and 15 GHz, there is obvious wavefront bending in the near-field region of the exposed object, indicating that the object introduces frequency-related phase perturbations. Figure 3 Figures c and d show that the near-field reflected wavefront tends to become planar after the addition of the metasurface. The total reflection phase of the composite structure is: total ( f ) = ob ( f ) + m ( f ).when total ( f When the composite structure approaches π within the target operating frequency band, it is electromagnetically equivalent to a continuous ideal conductor plane, thus achieving background uniformity restoration.

[0046] Figure 3 Figures e and f present the far-field RCS distribution results at 14 GHz and 15 GHz, respectively. It can be seen that after adding the metasurface, the scattering in the main lobe direction is significantly reduced, the peak value of the curve decreases, and the scattering intensity is reduced by several decibels compared to the bare target state, verifying the effectiveness of phase compensation.

[0047] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0048] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An optical-microwave integrated stealth metasurface structure, characterized in that, include: Visible light stealth structures and / or microwave stealth structures; The visible light stealth structure is used to control the refraction path of incident visible light, thereby creating an optical shielding effect in the target area. The microwave stealth structure is used to modulate the amplitude and / or phase of the incident microwaves to reduce the scattering intensity of the target object in a preset direction. The visible light stealth structure and the microwave stealth structure can be set independently or integrated on the same transparent substrate or different substrates.

2. The optical-microwave integrated stealth metasurface structure according to claim 1, characterized in that, The visible light stealth structure includes an array of refractive microstructures disposed on the surface of a transparent substrate; The refractive microstructure array includes at least two sets of refractive structure units with different tilt directions, which are used to refractively control visible light incident vertically or nearly vertically, so that the light path is reconstructed in space and an optical shielding area is formed behind the refractive structure.

3. The optical-microwave integrated stealth metasurface structure according to claim 2, characterized in that, The refractive structural unit is a wedge structure, a prism structure, a sawtooth structure, a gradient refractive index structure, or a combination thereof.

4. The optical-microwave integrated stealth metasurface structure according to claim 2, characterized in that, The two sets of refractive structural units are arranged symmetrically, periodically, or alternately.

5. The optical-microwave integrated stealth metasurface structure according to claim 1, characterized in that, The microwave stealth structure includes a transparent metasurface structure disposed on the outside of the target object and maintaining a preset distance from the target object; The transparent metasurface structure includes an array of electromagnetic control units disposed on the surface of a transparent substrate.

6. The optical-microwave integrated stealth metasurface structure according to claim 5, characterized in that, The electromagnetic control unit array is used to modulate the amplitude and / or phase of the incident microwave electromagnetic wave, so that the modulated electromagnetic wave and the scattered wave of the target object form phase compensation, thereby reducing the radar cross section of the target object in a preset direction.

7. The optical-microwave integrated stealth metasurface structure according to claim 6, characterized in that, The electromagnetic control unit is a metal patch structure, a slotted structure, a resonant ring structure, a frequency selective structure, a metasurface unit, or a combination thereof.

8. The optical-microwave integrated stealth metasurface structure according to claim 1, characterized in that, The visible light cloaking structure is independently set on a transparent substrate, specifically as follows: A refractive microstructure array is disposed on both sides of the transparent substrate; The microwave stealth structure is independently mounted on a transparent substrate, specifically as follows: An array of electromagnetic control units is arranged on both sides of the transparent substrate.

9. The optical-microwave integrated stealth metasurface structure according to claim 1, characterized in that, The visible light stealth structure and the microwave stealth structure are integrated on the same transparent substrate, specifically: A refractive microstructure array is disposed on one side of the transparent substrate. An array of electromagnetic control units is disposed on the other side of the transparent substrate.

10. The optical-microwave integrated stealth metasurface structure according to claim 8, characterized in that, The refractive microstructure and the electromagnetic control unit are arranged in layers or in combination.

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