A design method of a spherical mesh structure based on weft arrangement circular ring

Abstract

The application relates to a spherical mesh structure based on weft arrangement annular rings and a design method thereof, and belongs to the field of optical transparent electromagnetic shielding. In view of the current uneven distribution of the metal mesh unit structure of a spherical base, which leads to wave leakage and imaging quality deterioration, the application proposes that annular ring units located on a spherical surface are distributed along weft, and adjacent annular ring units are connected in an intersecting mode to form a spherical mesh structure. The spherical mesh design method based on the weft arrangement annular rings can make the annular mesh structure arrangement have better position uniformity, cooperate with the annular unit homogenization high-order diffraction characteristics, and make the electromagnetic shielding characteristics and optical transparency at different positions of the spherical window surface more uniform and stable. Moreover, the regularity of the annular unit distribution is strong, which is helpful to reduce the processing difficulty of the spherical mesh.

Description

Technical Field

[0001] This invention belongs to the field of optically transparent electromagnetic shielding, and specifically relates to a design method for a spherical mesh structure based on a lattice-arranged circular ring. 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 design method for a spherical mesh grid structure based on latitudinal arrangement of circular rings. Circular ring units are arranged according to the uniformly divided latitudinal positions to obtain a spherical metal mesh grid. This invention provides a high-quality transparent electromagnetic shielding mesh grid design method for dome-shaped optical windows, achieving spherical mesh grid structures with more stable electromagnetic shielding performance and more uniform optical performance under various incident angles. The arrangement characteristics of the circular ring units in this invention exhibit high regularity; therefore, for existing spherical mesh grid manufacturing equipment with latitudinal and concentric circle structures, higher-performance dome-shaped transparent electromagnetic shielding optical window products can be obtained with minimal changes to hardware and operating modes.

[0013] The technical solution adopted in this invention is: a spherical grid structure based on the arrangement of circular rings along latitudes and its design method. The spherical grid structure is characterized by circular ring units distributed along latitudes on the spherical surface, with adjacent circular ring units connected in an intersecting manner. The design process includes the following steps: Step 1: Construct a sphere based on the surface curvature radius of the target dome-shaped light window. The sphere intersects with any straight line passing through its center to obtain two poles. Using the straight line as the axis, arrange latitudes between the two poles to divide the sphere, ensuring that the spherical distance dw between any two adjacent latitudes in the meridian direction is equal. Step 2: Divide each latitude line equidistantly according to its circumference. The lengths of the arc segments after division are denoted by ds1, ds2, ds3… The error between these arc segment lengths and their average value does not exceed 10%. The endpoints of each arc segment after division along the latitude line are taken as position nodes. Step 3: On the tangent plane between the position node and the sphere, with the position node as the center of the ring, and R… c Let R be the outer radius of the annulus. Arrange the annular elements, where R is the outer radius of the annulus element. cThe value range is greater than half of the maximum value among the arc segment lengths ds1, ds2, ds3... and less than the maximum value; Step 4: Project the annular unit onto the sphere along the diameter direction passing through the corresponding node of the annular unit to obtain the annular unit located on the sphere. All annular units together constitute the spherical annular grid structure. Each annular unit is connected to at least one adjacent annular unit by intersecting each other; Step 5: According to the actual light-transmitting aperture size of the dome-shaped light window, cut out the corresponding range of the spherical grid and output the data as a design drawing. This design drawing is used for the structural manufacturing of the dome-shaped transparent electromagnetic shielding light window.

[0014] In the technical solution of the above invention: the spherical distance dw between adjacent parallels and the arc lengths ds1, ds2, ds3... after dividing all parallels, are typically in the millimeter and sub-millimeter range. The line width W of the annular unit is set according to the position node. c The range is in the micrometer or submicrometer range.

[0015] 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.

[0016] In the technical solution of the above invention: the design drawing generated by cutting the spherical grid according to the size requirements of the light window is any area on the sphere.

[0017] 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.

[0018] In the above-mentioned technical solution of the invention: the circular mesh is disposed on the convex spherical surface or the concave spherical surface of the transparent spherical cover substrate, or exists on both the convex spherical surface and the concave spherical surface.

[0019] The innovativeness and good effects of this invention are:

[0020] 1. This invention addresses the structural characteristics of a spherical optical window by first dividing the latitude along the meridian direction into equally spaced parallels and equally spaced position nodes along the latitude direction, and then arranging circular units as the most basic unit pattern on each position node. This division rule reduces the tolerance of the distance between the circular units, making the arrangement of the spherical grating structure more consistent. The circular basic units can homogenize the higher-order diffraction distribution of the grating, achieving low sidelobe optical diffraction characteristics, which is beneficial for imaging. Combining these two approaches allows the optical window to have relatively stable light transmission within the visible angle range, reducing vignetting and differences in brightness and sharpness in different areas during imaging. Furthermore, it avoids the problem of extreme aperture sizes appearing at the edge of the optical window when traditional spherical grating structures are applied to large span-to-width dome-type optical windows, leading to electromagnetic wave leakage in that area and compromising the overall electromagnetic shielding effect of the dome-type optical window.

[0021] 2. The positional relationship of the annular units in this invention has a high degree of regularity, which can greatly reduce the complexity of the processing process. This allows the original "latitude and longitude" type spherical mesh processing equipment to process spherical meshes with superior performance after minor upgrades and modifications.

[0022] In summary, this invention proposes a grid structure based on a spherical substrate, in which circular ring-shaped unit structures are arranged and interconnected along equally spaced parallels. The spherical electromagnetic shielding window manufactured using this design method exhibits higher stability in both electromagnetic shielding and optical transparency under multiple incident angles. Furthermore, the parallel arrangement of the ring-shaped units requires minimal modification to the operating logic of the processing equipment, making it easy to upgrade and modify. Attached Figure Description

[0023] 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.

[0024] Figure 1 This is a side view schematic diagram of the spherical latitude arrangement in the grid design process. This diagram illustrates the arrangement of the axis passing through the center of the sphere and the spherical latitude lines in design step 1 of this invention from a spherical side view perspective. The spherical spacing between any two adjacent latitude lines is equal. The actual number of latitude lines is determined by the electromagnetic shielding application requirements of the spherical dome-shaped optical window and is not limited to the number shown in the diagram.

[0025] Figure 2This is a top-view schematic diagram illustrating the division of latitude lines into position nodes during the grid design process. This diagram, from a spherical top-view perspective, shows the distribution of latitude lines and position nodes in design step 2 of this invention. Centered on one pole of the sphere, the latitude lines are arranged in concentric circles, converging towards another pole below the surface. Each latitude line is equidistantly divided into arc segments. The length of the arc segments on the same latitude line is exactly equal, while the lengths of the arc segments on different latitude lines are not equal, but the difference from the average length of all arc segments does not exceed 10%. The position nodes in the diagram are only for illustrative purposes; the actual number of position nodes is determined based on the electromagnetic shielding application requirements of the spherical optical window.

[0026] Figure 3 This is a top-view schematic diagram of the arrangement of circular ring units in the grid design process. This diagram, from a spherical top-view perspective, illustrates the method of setting up the circular ring unit grid in design steps 3 and 4 of this invention. The vertices of the arc segments after latitude division serve as position nodes, and circular ring units are set up. There are intersecting portions between adjacent rings, thus forming a grid structure as a whole.

[0027] Figure 4 This is a partially enlarged schematic diagram of a circular grid with latitude lines. The purpose of this diagram is to illustrate the structural features of the intersections between the circular grid units.

[0028] Figure 5 This is a top view of the schematic diagram of the mesh structure in the embodiment.

[0029] Figure 6 This is the front view perspective of the schematic diagram of the grid structure in the embodiment.

[0030] Part numbers in the diagram are explained as follows: 1. Sphere; 2. Axis; 3. Pole; 4. Parallel; 5. Location node; 6. Circular element; 7. Connection method of intersecting grids; 8. Area captured in the grid design drawing; R c The outer radius of the annular element; W c The line width of the circular element. Detailed Implementation

[0031] 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.

[0032] According to one embodiment of the invention, for example Figure 5 and Figure 6 As shown in the figure, this embodiment presents a spherical mesh structure based on a circular ring with latitude arrangement and its design method. The basic parameters and design expectations of the spherical transparent electromagnetic shielding window are as follows: the spherical curvature radius of the mesh surface is 60mm, and the sag-to-span ratio (the ratio of sag height to aperture) of the spherical cap is 0.3:1.

[0033] Based on the above conditions, in a three-dimensional spherical coordinate system, the radius is set to... For the sphere, take the pitch angles on the sphere. and The points are taken as the two poles of the sphere. Based on the expected electromagnetic wave wavelength of the design target, the distance between the parallels along the meridian direction is... The number of latitude lines on the entire sphere is calculated using equation (1) and rounded down. strip.

[0034] Equation (1)

[0035] Based on the Pythagorean theorem and the altitude of the parallels, the expression for the perimeter of the i-th parallel (2) can be derived as follows:

[0036] Equation (2)

[0037] According to equation (2), the perimeter of the first parallel of latitude To ensure adequate connection of the ring grid structure, the position nodes between each ring layer and the position nodes of the next layer must be arranged in at least an isosceles triangle. Therefore, the average length of the latitude line segment is taken as [value missing]. mm. Since the quotient of the perimeter of a parallel and the average length of a parallel segment is not an integer, the number of segments is rounded to 5. Dividing the perimeter of the first parallel by 5 again yields the length of each arc segment on the first parallel. mm. Repeat the above steps to divide each parallel of latitude, obtaining the position nodes distributed on the sphere. The lengths of the arc segments divided by each parallel of latitude are ds1, ds2, ds3...ds377. Among all the arc lengths, ds1 has the largest value, so ds1 is used as the diameter of the ring unit of the grid, and ring units are set on the sphere. Project each ring onto the sphere to obtain the ring grid structure of the sphere. According to the actual size of the dome-shaped optical window, a 63.5mm high spherical crown portion is cut from the complete spherical grid, and the output data is used to generate the grid design drawing for the manufacture of the dome-shaped transparent electromagnetic shielding optical window.

[0038] In practical applications of dome-shaped light windows, when visible light is incident on the grid on the spherical substrate, the wavelength of the light wave is smaller than the aperture of the grid unit, and it can pass through smoothly; when electromagnetic waves that need to be shielded are incident on the grid on the spherical substrate, the electromagnetic waves cannot pass through the grid structure, some of the electromagnetic waves are reflected, and some are converted into heat energy under the action of electromagnetic induction.

[0039] Obviously, those skilled in the art, after understanding the content and principles of this invention, may make various modifications and changes in form and detail without departing from the principles and structure of this invention. However, these modifications and changes based on the ideas of this invention are still within the scope of protection of the claims of this invention.

Claims

1. A design method for a spherical grid structure based on a circular ring with latitude arrangement, characterized in that... The spherical grid structure consists of circular ring units (7) distributed along the latitude lines on the sphere, with adjacent circular ring units (7) connected in an intersecting manner. Its design process includes the following steps: Step 1: Make a sphere (1) according to the surface curvature radius of the target dome-shaped light window. The sphere (1) intersects with any straight line (2) passing through the center of the sphere to obtain the two poles (3) of the sphere. With the straight line (2) as the axis, arrange the parallels (4) between the two poles (3) to divide the sphere (1) so that the spherical distance dw between any two adjacent parallels (4) in the meridian direction is equal. Step 2: Divide each parallel of latitude into equal intervals according to the perimeter of the parallel of latitude. The lengths of the arc segments after the division of each parallel of latitude (4) are represented by ds1, ds2, ds3... The error between these arc segment lengths and their average values ​​does not exceed 10%. The endpoints of each arc segment after the division on the parallel of latitude (4) are taken as position nodes (5). Step 3: On the tangent plane between position node (5) and the sphere, with position node (5) as the center of the annulus, and R... c Let R be the outer radius of the annulus. Arrange the annular elements (6), where R is the outer radius of the annulus element (6). c The range of values ​​is greater than half of the maximum value among the arc segment lengths ds1, ds2, ds3... and less than the maximum value; Step 4: Project the annular unit (6) onto the sphere along the diameter direction of the corresponding node (5) of the annular unit to obtain the annular unit (7) located on the sphere. All the annular units (7) together constitute the spherical annular grid structure. Each annular unit (7) is connected to at least one adjacent annular unit (7) through an intersection (8). Step 5: Based on the actual light-transmitting aperture size of the dome-shaped light window, cut out the corresponding range of spherical mesh (9), and output the data as a design drawing. This design drawing is used for the structural manufacturing of the dome-shaped transparent electromagnetic shielding light window.

2. The design method for a spherical grid structure based on a circular ring with latitude arrangement according to claim 1, characterized in that: The spherical distance dw between adjacent parallels (4) and the arc lengths ds1, ds2, ds3... after dividing all parallels (4) are typically in the millimeter and sub-millimeter range. The line width W of the annular unit (6) is set according to the position node. c The range is in the micrometer or submicrometer range.

3. The design method for a spherical grid structure based on a circular ring with latitude arrangement 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.

4. The design method for a spherical grid structure based on a circular ring with latitude arrangement according to claim 1, characterized in that: The design drawing generated by cutting the spherical grid (9) according to the size requirements of the light window is an arbitrary spherical cap area on the sphere.

5. The design method for a spherical grid structure based on a circular ring with latitude arrangement according to claim 1, characterized in that: The circular grid of the dome-shaped electromagnetic shielding window is made of metals, alloys, metal compounds, or graphene with good electrical conductivity.

6. The design method for a spherical grid structure based on a circular ring with latitude arrangement according to claim 1, characterized in that: The circular grid is disposed on the convex or concave spherical surface of the transparent spherical cover substrate, or simultaneously on both the convex and concave spherical surfaces.

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