A spherical electromagnetic shielding optical window based on a spirally arranged circular ring grid.

Abstract

This invention relates to a spherical electromagnetic shielding window based on a spirally arranged circular ring grating, belonging to the field of optically transparent electromagnetic shielding. Addressing the current issue of uneven distribution of metal grating unit structures on spherical substrates, leading to wave leakage and degraded imaging quality, this invention proposes a grating structure on a spherical surface using circular rings as basic units arranged in a spiral pattern. The circular ring units can homogenize higher-order diffraction, achieving low sidelobe optical diffraction characteristics. The spiral-guided distribution ensures better positional uniformity of the circular ring grating on the spherical surface. The spherical electromagnetic shielding window based on a spirally arranged circular ring grating proposed in this invention achieves more uniform and stable electromagnetic shielding characteristics and optical transparency at different locations on the surface of the spherical window.

Description

Technical Field

[0001] This invention belongs to the field of optically transparent electromagnetic shielding, and specifically relates to a spherical electromagnetic shielding optical window based on a spirally arranged circular ring grid. Background Technology

[0002] Transparent electromagnetic shielding windows have wide applications in various instruments, communication equipment, and defense equipment, such as optical windows for aircraft, satellites, ships, and automobiles; optical instrument windows and display panels; electromagnetic isolation rooms and security facilities; transparent components for communication equipment; and mobile phone touchscreens. Transparent electromagnetic shielding windows offer high light transmittance and high wavefront quality, enabling accurate and efficient transmission of optical images and signals. Simultaneously, the windows shield electromagnetic waves, preventing leakage of internal electromagnetic waves and interference from external electromagnetic waves. Current research and applications of transparent electromagnetic shielding windows primarily focus on planar windows, with various structural forms of metal mesh gratings proposed and applied, mainly using complex metal mesh gratings arranged on the window surface. Compared to ordinary planar transparent electromagnetic shielding windows, spherical windows offer a wider field of view, better improving the imaging range behind the window. The application prospects of spherical electromagnetic shielding windows are very broad, especially for equipment and facilities operating in environments with high temperature and pressure, high-speed fluid motion, and strong multi-angle interference, where both wide field of view and high imaging quality are required. However, electromagnetic shielding of current dome-shaped optically transparent components remains a technical challenge, with relatively few related research and application cases. Existing research has identified two main types of metal mesh gratings used on spherical substrates. The first type is primarily designed manually, directly arranging the mesh structure on the spherical contour, commonly using basic structures such as concentric circles, latitude and longitude lines, or orthogonal double latitude lines. The second type is typically indirectly fabricated or randomly generated, such as self-assembled cracked mesh gratings created by natural thin-film cracking, or mesh gratings processed by stress stretching from planar structures to spherical structures, resulting in mesh patterns with a degree of randomness. In practical applications, the former type of grating structure typically lacks structural design tailored to spherical features, resulting in poor uniformity of grating distribution. Consequently, the larger the applied spherical span-to-span ratio (the ratio of the spherical cap's height to its aperture), the more pronounced the difference in grating density between the central and edge regions of the sphere, severely impacting the uniformity and stability of light transmission and electromagnetic shielding performance. The latter type of structure exhibits greater randomness, making parameter control difficult and ensuring consistent grating aperture. Even with algorithmic back-calculation of structural density, it's challenging to control variations in grating line thickness during manufacturing, leading to issues such as broken lines and increased local sheet resistance. Electromagnetic shielding is primarily achieved through electromagnetic reflection and absorption. A well-designed and reliable spherical grating structure, with its metal grating layer on the spherical surface, can achieve both electromagnetic reflection and absorption, while also providing better performance in optical image information transmission.

[0003] Currently, the following are typical achievements and patents in the field of spherical substrate grids:

[0004] Patent publication number: CN1488997A "A concave spherical photolithography marking machine" and "Realization of constant exposure laser direct writing control of deep concave spherical grid" and other patents and papers have proposed the design and manufacturing method of spherical substrate grids. However, the grids manufactured by them adopt structures such as "latitude and longitude lines" and "latitude and longitude lines". On spherical substrates with large span ratio, it is difficult to guarantee the uniformity of grid aperture.

[0005] Patent publication number: CN101917837A "An electromagnetic shielding conformal optical window with a latitude and longitude grid structure", the grid structure adopts a concentric circle design, and it is difficult to guarantee the uniformity of the grid aperture on the spherical substrate.

[0006] Patent publication number: CN110931330A "A process for preparing a honeycomb spherical grid", which involves first manufacturing a honeycomb grid on a plane and then pressing it onto a sphere using a hydraulic press. This process cannot avoid deformation and breakage of the linear structure during the stretching and bonding process, resulting in differences in the uniformity of the grid at different positions on the sphere.

[0007] Patent publication number: CN114051372A "A method for manufacturing a concave metal mesh grid for a fairing" describes a grid pattern of "longitude and latitude lines" etched on a concave spherical surface. However, the uniformity of the mesh aperture on the spherical substrate varies considerably.

[0008] Patent applications No. 201911335993.7 and 201510906030.3, patent publication No. CN106298401A "A tooling mold for forming spherical grid and a method for forming spherical grid", and patent publication No. CN218104063U "A tool for preparing a convex light-transmitting shielding window", etc., all involve first manufacturing the grid on a flat surface and then attaching it to a spherical surface. This cannot avoid deformation and breakage of the linear structure during the stretching and attaching process, which will lead to the problem of grid density differences at different positions on the spherical surface.

[0009] Patent publication number: CN104837326A "Method for manufacturing electromagnetic shielding curved optical window with metal mesh structure" uses a method of drying a mask liquid coating to generate cracks to form a curved mesh, which belongs to the "self-assembly" type. The cracks in this method are spontaneously formed by physical phenomena, and the period, linewidth and other parameters of the mesh structure are difficult to control stably.

[0010] The main inventions of patent publication numbers CN205828664U "A Conformal Spherical Antenna Array with Good Shielding Effect" and CN205828676U "A Conformal Spherical Antenna Array" are the design of antenna array structures that allow the antenna array to be fitted with shielding covers to prevent signal interference. However, they do not describe the shielding structure, and the antenna shielding covers do not need to be optically transparent. Therefore, they do not conflict with the content of this patent.

[0011] In summary, most artificially designed spherical substrate grids are based on improvements from planar grids to spherical structures, relying entirely on the basic forms of parallels and concentric circles. They lack design considerations for the geometric features of a three-dimensional sphere, simply connecting the nodes with arcs to form the grid. Viewed from top, they resemble a grid, but high-density areas and structurally deformed gaps appear on the sides over time. These solutions struggle to meet the requirement for uniform and consistent grid cell distribution on spherical substrates with large span-to-span ratios. Other grid structures manufactured using random and stretching methods suffer from low controllability of random structures and line breakage caused by stretching, ultimately affecting the uniformity and stability of the light transmission and electromagnetic shielding performance of the dome-shaped light window. Summary of the Invention

[0012] This invention proposes a spherical electromagnetic shielding window based on a spirally arranged circular ring grid. By setting up circular ring grid units and obtaining a spherical metal grid, the electromagnetic shielding performance and optical performance stability of the spherical substrate grid under multiple incident angles are improved, providing a high-quality transparent electromagnetic shielding grid form for spherical windows.

[0013] The technical solution adopted in this invention is: a spherical electromagnetic shielding window based on a spirally arranged circular ring grid; the electromagnetic shielding window structure consists of a transparent spherical base and a conductive circular ring grid, wherein the conductive circular ring grid is disposed on the convex or concave spherical surface of the transparent spherical base, or simultaneously on both surfaces; the conductive circular ring grid is composed of circular ring units arranged spirally on the spherical surface, and each circular ring unit has at least one intersection point with a spiral line used to indicate the arrangement trend; the spiral line indicating the arrangement trend... The number of spirals is greater than or equal to one, and the trajectory of the spiral is defined by the mathematical function expression of the spiral on a sphere; the distance between the center of the annular unit and the nearest spiral is less than or equal to the radius (R) of the outer circle of the annulus; the annular unit intersects with at least one adjacent annular unit to form an annular grid; the outer diameter (2*R) of the annular unit is less than 0.5 times the wavelength of the shielded electromagnetic wave, and the inner diameter (2*r) is greater than the wavelength of the light wave; the material used to prepare the annular grid is conductive, thereby enabling the spherical light window to have a transparent electromagnetic shielding function.

[0014] In the above-mentioned technical solution of the invention, the types of spirals on the sphere include: Fibonacci spiral, Archimedes spiral, Fermat spiral, equiangular spiral, Euler spiral, logarithmic spiral, and Theodorus spiral.

[0015] In the above-mentioned technical solution of the invention: the starting point of the spiral is located at any position on the complete sphere on which the ring grid is set, that is, the starting point of the spiral can be outside the area of ​​the spherical electromagnetic shielding window.

[0016] In the above-mentioned technical solution of the invention: adjacent annular units on the sphere refer to the N annular units that are closest to each other after the current annular unit is sorted according to the spherical distance between them, and the number of N intersecting annular units is 1 to 8.

[0017] In the above-mentioned technical solution of the invention: the outer diameter (2*R) of the annular unit is on the order of millimeters and sub-millimeters; the line width of the annular unit, i.e. the difference between the inner and outer radii (Rr), is on the order of micrometers or sub-micrometers; when the annular unit intersects with an adjacent annular unit, the minimum width of the interconnected area is also on the order of micrometers or sub-micrometers; and the thickness of the annular unit is greater than 100nm.

[0018] In the above-mentioned technical solution of the invention: the circular grid of the spherical electromagnetic shielding window is made of metal, alloy, metal compound, or graphene with good conductivity.

[0019] In the above-mentioned technical solution, an anti-reflection film is disposed on the outer side of the conductive circular ring grid.

[0020] In the above-mentioned technical solution of the invention, a protective film is disposed on the outside of the conductive circular ring grid.

[0021] In the above-mentioned technical solution of the invention: an anti-reflection film is disposed on the outside of the conductive circular grid, and a protective film is disposed on the outside of the anti-reflection film.

[0022] The innovativeness and good effects of this invention are:

[0023] 1. This invention is based on a transparent dome-shaped optical window. Compared with a regular flat optical window, it allows the optical system to obtain a larger imaging range without using wide-angle or fisheye lenses, thereby reducing aberrations such as distortion and improving the imaging quality of observation and photography equipment behind the optical window.

[0024] 2. This invention uses circular ring units as the most basic grid unit pattern, which can homogenize the higher-order diffraction distribution of the grid and achieve low sidelobe optical diffraction characteristics, which is beneficial for imaging. The grid is constructed by arranging circular ring units in a spiral pattern described by mathematical expressions, which can make the grid units uniformly distributed in all directions and the size of the light-transmitting aperture consistent. This makes the light window have relatively stable light transmission within the viewing angle range, reducing problems such as vignetting and differences in brightness and sharpness caused by uneven grid arrangement in different areas during imaging or observation.

[0025] 3. Based on the use of circular ring units, this invention utilizes the helical pattern of spatial geometry to promote the uniformity of the grid structure, significantly improving the electromagnetic shielding performance of the dome in different directions. This avoids the problem of extreme aperture sizes appearing at the edges of the dome-shaped optical window when traditional spherical grid structures are applied to dome-shaped windows with a large span-to-width ratio, leading to increased electromagnetic wave leakage in those areas and compromising the overall electromagnetic shielding effect of the dome-shaped optical window.

[0026] In summary, this invention uses a spherical substrate as a base and arranges circular units with a spiral as a trend reference line to form a grid structure and manufacture a spherical electromagnetic shielding window. This results in higher stability of electromagnetic shielding performance and optical transparency performance under multiple incident angles. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the pictures described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a cross-sectional schematic diagram of a spherical electromagnetic shielding optical window based on a spirally arranged circular mesh grid.

[0029] Figure 2 This is a schematic diagram of a spherical electromagnetic shielding window based on a spirally arranged circular grid.

[0030] Figure 3 This is a partially enlarged schematic diagram of a spherical electromagnetic shielding optical window based on a spirally arranged circular mesh grid.

[0031] Figure 4 This is the front view perspective of the schematic diagram of the grid structure in Embodiment 1.

[0032] Figure 5 This is a top view of the schematic diagram of the grid structure in Example 1.

[0033] Figure 6 This is the front view perspective of the schematic diagram of the grid structure in Embodiment 2.

[0034] Figure 7 This is a top view of the schematic diagram of the grid structure in Embodiment 2.

[0035] Part numbers in the diagram are explained as follows: 1. Transparent spherical substrate; 2. Conductive circular mesh grid; 31. Antireflective coating; 32. Protective film; 4. Spiral; 5. Mesh grid on a complete sphere; 6. Cut-off spherical mesh grid; 7. Circular ring unit; 8. Structure of interconnected circular rings; R. Outer radius of the circular ring unit; r. Inner radius of the circular ring unit. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments: The object of the present invention is achieved as follows: A point is arbitrarily selected on the surface of a sphere with the same surface size as the target transparent spherical substrate (1) as the starting point, and a spiral (4) is set on the sphere. The spiral (4) starts from the starting point on the complete sphere, winds around the sphere, and reaches the end point that is symmetrical about the center of the sphere with respect to the starting point; the spiral (4) is divided into equal segments, and the endpoints of each segment are used as position nodes; through each position node, a ring is set on the tangent plane of the sphere, and the ring is projected onto the sphere. The structure obtained by projection is the ring unit (5) of the grid. Adjust the size of the ring unit (5) so that adjacent rings intersect and some structures overlap and connect to form a grid (2); the parameters of the rings can be fine-tuned by using genetic algorithms, etc. The objects of adjustment are the center position and radius of the rings, so as to further improve the overall uniformity of the grid; according to the size of the target spherical base (1), a suitable area is cut from the designed spherical grid, and the output is the grid design drawing. Micro-nano processing technology is used to manufacture the transparent spherical base (1) with metals, alloys and metal compounds with good conductivity on the transparent spherical base (1). The spherical light window with transparent electromagnetic shielding performance is manufactured. In the actual use of the spherical light window, when visible light is incident on the grid on the spherical base, the wavelength of the light wave is smaller than the aperture of the grid unit and can pass through smoothly; when the electromagnetic wave that needs to be shielded is incident on the grid of the spherical base, the wavelength of the electromagnetic wave is larger than the aperture of the grid unit, part of the electromagnetic wave is reflected and part is converted into heat energy under the action of electromagnetic induction.

[0037] Figure 1This is a cross-sectional schematic diagram of a spherical electromagnetic shielding light window based on a spirally arranged circular mesh grid. The transparent spherical substrate (1) can be any transparent material, as long as it can be used as a transparent light window material that meets the requirements of the application. At the same time, the circular mesh grid (2) pattern can be processed on its surface according to a certain process flow, including ordinary glass, quartz glass, infrared materials and transparent resin materials. The main part of the circular mesh grid (2) that generates electromagnetic shielding function is made of highly conductive material. It can be processed on the convex spherical surface or concave spherical surface of the spherical light window or on both convex and concave spherical surfaces according to the actual application requirements. An antireflective film (31) and a protective layer (32) are configured to cover the surface of the circular mesh grid (2) according to the actual application requirements. They can be composed of a single layer or a multi-layer film system structure, which can increase the transmittance of visible light. At the same time, the protective layer can prevent the metal parts from being scratched or corroded and oxidized by long-term exposure to air.

[0038] Figure 2 This is a schematic diagram of a spherical electromagnetic shielding window based on a spiral-arranged circular ring grid. The image illustrates the design features of the structure from a top-down view. The multiple spiral lines (4) are coiled around the entire sphere, controlling the arrangement of the circular ring units. Figure 2 The distribution characteristics of the two spiral lines are outlined in the diagram for illustration; the complete spherical grid (5) refers to the spherical grid obtained by arranging the annular units (7) on the entire spherical surface according to the spiral line (4) that winds around the entire spherical surface and its determined position nodes; the truncated spherical grid (6) refers to the appropriate range selected based on the complete spherical grid (5) according to the aperture of the dome-shaped light window, and this part of the grid will be manufactured on the transparent spherical substrate (1).

[0039] Figure 3 This is a partially enlarged schematic diagram of a spherical electromagnetic shielding window based on a spiral-arranged circular ring grid. The circular ring unit (7) is the basic unit that makes up the grid structure. Its position is determined by the equally spaced spiral lines (4). The outer radius and inner radius of each circular ring unit (7) are R and r, respectively. Adjacent circular ring units (7) have overlapping areas (8) that allow the circular ring units (7) to be connected to form a conductive grid. Therefore, twice the outer radius R of the circular ring unit (7) should also be greater than the minimum distance between adjacent units.

[0040] To facilitate understanding of the present invention, the invention will be described more clearly and completely below in conjunction with the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0041] Example 1:

[0042] According to one embodiment of the invention, for example Figure 4 and Figure 5As shown in the figure, the spherical electromagnetic shielding window based on a spiral-arranged circular ring grid in this embodiment uses the Fibonacci spiral function expression as shown in equation (1).

[0043] Equation (1)

[0044] In the formula, n is the total number of grid points on the complete sphere, k is the number of grid points currently being calculated, and R b Let C be the radius of the sphere, and let C be an irrational number that controls the rotation amplitude of the helix, the value of which will affect the number of multiple helices.

[0045] According to equation (1), after substituting the corresponding parameters, the position nodes based on the spherical helix can be obtained. The center coordinates of the k-th annular element in the three-dimensional Cartesian coordinate system are: In this case, the function parameter takes the following values: radius of the sphere. =80mm, the number of nodes in the complete spherical mesh is n=160000 (for global display in the schematic diagram, only 2000 mesh nodes are shown), constant. On the sphere, a tangent plane is created at each position node, and an annulus with an outer radius R = 200µm is set on the plane (the outer radius R of the annulus in the schematic diagram is 2.7mm), and the width of the annulus is 4µm (the width of the annulus in the schematic diagram is 100µm). The annulus is projected perpendicularly onto the sphere to obtain the annular mesh on the sphere. The position of the first annulus of the mesh unit is further fine-tuned. The three annulus adjacent to it (i.e., positions 2, 3, and 4 generated by the helical function) are taken, the centroid is calculated, and the annulus is moved to this position to make the distance between its adjacent mesh units closer. According to the actual aperture of the dome-shaped optical window, a structural design drawing with matching dimensions is extracted from the overall spherical mesh for use in the manufacture of the dome-shaped optical window.

[0046] Example 2:

[0047] According to two embodiments of the present invention, for example Figure 6 and Figure 7 As shown in the figure, the spherical electromagnetic shielding window based on a spiral-arranged circular ring grid in this embodiment uses the spiral function expression in a three-dimensional spherical coordinate system as shown in equation (2).

[0048] Equation (2)

[0049] In the formula, n is the total number of grid points on the complete sphere, and k is the number of grid points currently being calculated.

[0050] According to equation (2), after substituting the corresponding parameters, the coordinates of the center of the k-th annular element in the three-dimensional spherical coordinate system are: , Let be the radius of the sphere. In this case, the function parameter takes the value of: the radius of the sphere. =80mm, the number of nodes in the complete spherical mesh is n=160000 (for global display in the schematic diagram, only 2000 mesh nodes are shown in the schematic diagram); a tangent plane is made on the spherical surface at each position node, and an annulus with an outer radius R=200µm is set on the plane (the outer radius R of the annulus in the schematic diagram is 2.7mm), and the width of the annulus is 6µm (the width of the annulus in the schematic diagram is 100µm); the annulus is projected vertically onto the spherical surface to obtain the annular mesh on the spherical surface; the position spacing of the mesh unit is further optimized and fine-tuned using a genetic algorithm to make the distance deviation between adjacent mesh units smaller; according to the actual aperture of the dome-shaped light window, a structure with matching size is extracted from the overall spherical mesh to generate a design drawing for the manufacture of the dome-shaped light window.

[0051] The above descriptions are merely two specific examples of the present invention. The spherical electromagnetic shielding optical window manufactured through these examples can be used in scenarios requiring electromagnetic wave shielding in the X and Ku bands. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and detail without departing from the principles and structure of the present invention. However, these modifications and changes based on the concept of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A spherical electromagnetic shielding optical window based on a spirally arranged circular ring grid, characterized in that: The electromagnetic shielding light window structure consists of a transparent spherical base (1) and a conductive circular ring grid (2). The conductive circular ring grid (2) is disposed on the convex spherical surface or concave spherical surface of the transparent spherical base (1), or exists on both the convex spherical surface and the concave spherical surface. The conductive circular ring grid (2) is composed of circular ring units (7) arranged in a spiral shape on the spherical surface. Each circular ring unit (7) has at least one intersection point with the spiral line (4) used to indicate the arrangement trend characteristics. The number of spiral lines (4) illustrating the arrangement trend is greater than or equal to one, and the trajectory of the spiral line (4) is defined by the mathematical function expression of the spiral line on the sphere; the distance between the center of the annular unit (7) and the nearest spiral line is less than or equal to the radius (R) of the outer circle of the annular unit; the annular unit (7) intersects with at least one adjacent annular unit to form an annular grid; the outer diameter (2*R) of the annular unit (7) is less than 0.5 times the wavelength of the shielded electromagnetic wave, and the inner diameter (2*r) is greater than the wavelength of the light wave; the material used to prepare the annular grid is conductive, thereby giving the spherical light window a transparent electromagnetic shielding function.

2. The spherical electromagnetic shielding optical window based on a spirally arranged circular mesh grid according to claim 1, characterized in that: The types of spirals (4) on a sphere include: Fibonacci spiral, Archimedes spiral, Fermat spiral, equiangular spiral, Euler spiral, logarithmic spiral, and Theodorus spiral.

3. The spherical electromagnetic shielding optical window based on a spirally arranged circular mesh grid according to claim 1, characterized in that: The starting point of the spiral (4) is located at any position on the complete sphere (5) on which the ring grid is set, that is, the starting point of the spiral (4) can be outside the spherical electromagnetic shielding window area (6).

4. The spherical electromagnetic shielding optical window based on a spirally arranged circular mesh grid according to claim 1, characterized in that: Adjacent annular units (7) on the sphere refer to the N annular units (7) that are closest to each other after the current annular unit (7) is sorted according to the spherical distance between them. The number of N intersecting annular units (7) is 1 to 8.

5. A spherical electromagnetic shielding optical window based on a spirally arranged circular mesh grid according to claim 1, characterized in that: The outer diameter (2*R) of the circular unit (7) is on the order of millimeters and sub-millimeters. The line width of the circular unit (7), i.e. the difference between the inner and outer radii (Rr), is on the order of micrometers or sub-micrometers. When the circular unit (7) intersects with an adjacent circular unit, the minimum width of the interconnected area (8) is also on the order of micrometers or sub-micrometers. The thickness of the circular unit is greater than 100nm.

6. A spherical electromagnetic shielding optical window based on a spirally arranged circular ring grid according to claim 1, characterized in that: The circular grid (2) of the spherical electromagnetic shielding window is made of metals, alloys, metal compounds, or graphene with good conductivity.

7. A spherical electromagnetic shielding optical window based on a spirally arranged circular mesh grid according to claim 1, characterized in that: An antireflective film (31) is disposed on the outside of the conductive circular grid (2).

8. A spherical electromagnetic shielding optical window based on a spirally arranged circular mesh grid according to claim 1, characterized in that: A protective film (32) is disposed on the outside of the conductive circular grid (2).

9. A spherical electromagnetic shielding optical window based on a spirally arranged circular mesh grid according to claim 1, characterized in that: An antireflective film (31) is disposed on the outside of the conductive circular grid (2), and a protective film (32) is disposed on the outside of the antireflective film (31).

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