Holographic imaging metasurface structure based on pure phase change and design method

Abstract

The invention discloses a holographic imaging metasurface structure based on pure phase change and a design method. The metasurface comprises a plurality of cellular structures. Each cellular structure comprises a first metal patch layer, a first dielectric material layer, a second metal patch layer, a second dielectric material layer and a third metal patch layer which are stacked in sequence; the first metal patch layer is used for allowing X-polarized electromagnetic waves to transmit; the third metal patch layer is used for allowing transmission of Y-polarized electromagnetic waves; the second metal patch layer serves as a resonant structure, is used for generating a phase difference between a linear polarization electromagnetic wave and an input electromagnetic wave under a linear polarization condition, and comprises an adjustable open regular octagonal metal ring and a resonant metal strip which are located in the center of the cellular structure, and the resonant metal strip is located in the open regular octagonal metal ring; and the spring is not in contact with the adjustable opening regular octagonal metal ring. According to the invention, the transmission type metasurface with high efficiency and flexible regulation and control can be realized.

Description

Technical Field

[0001] This invention relates to the field of metasurface technology, specifically to a holographic imaging metasurface structure and design method based on pure phase change. Background Technology

[0002] Metasurfaces are two-dimensional metamaterials that replace the three-dimensional subwavelength units in metamaterials with two-dimensional subwavelength units. Their manipulation of electromagnetic waves does not rely on the accumulation of optical path during propagation, but rather on the precise modulation of the amplitude, phase, and polarization of electromagnetic waves through changes in parameters such as the size and shape of the two-dimensional units. Compared to metamaterials, metasurfaces are more compact, have lower losses, and are easier to fabricate, offering significant advantages in holographic imaging and thus attracting widespread attention from the academic community.

[0003] Optical holographic imaging has reached a high level of maturity and yielded diverse results, while research progress in microwave holographic imaging is relatively lagging. With the increasing demand for microwave information transmission capacity, the advantages of microwave holographic imaging, such as high confidentiality and high reliability, are becoming increasingly prominent. Therefore, research on microwave holographic imaging technology has gradually become a research hotspot in this field in recent years.

[0004] Patent CN120280698A discloses a dual-polarization terahertz broadband polarization converter and its application in space imaging. By changing the structural parameters of the polarization converter, it constructs "1" and "0" amplitude-coded metasurfaces and utilizes the transmission characteristics of linearly polarized waves to construct amplitude-coded metasurfaces. These coded metasurfaces achieve dual-polarization space imaging under linearly polarized terahertz wave incidence. The holographic imaging in this patent is primarily in the terahertz band. Patent CN115167088A discloses a deep learning-based customizable holographic metasurface design method. Based on a network model and a metasurface structure with adjustable amplitude and phase, it achieves simultaneous control of amplitude and phase by changing the opening angle and rotation angle of the structure. A parameter scanning method is used to collect the dataset, where the input is amplitude and phase information, and the output is unit structure information. In the metasurface structure, the equivalent circuit of the I-shaped patch consists of an I-shaped abrupt arm span and the connection between the I-shaped segments forming an equivalent inductance, and an equivalent capacitance between the two arms. As the arm span decreases, both the equivalent capacitance and equivalent inductance decrease, requiring control of both amplitude and phase parameters during modulation, making the adjustment complex. Patent CN114976667A discloses a 3-bit dual-polarization phase-tunable reconfigurable smart metasurface. In this patent, each 3-bit dual-polarization phase-tunable reconfigurable smart metasurface unit integrates a pair of varactor diodes along both the x and y axes. By controlling the voltage values ​​on both sides of the varactor diodes, independent 3-bit phase modulation can be achieved in both the x and y axes. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a metasurface structure based on the phase change of electromagnetic waves in pure phase holographic imaging in the microwave band.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A holographic imaging metasurface structure based on pure phase change, the metasurface comprising multiple cellular structures; each cellular structure comprising: a first metal patch layer 11, a first dielectric material layer 21, a second metal patch layer 30, a second dielectric material layer 22 and a third metal patch layer 12 stacked sequentially;

[0008] The first metal patch layer 11 is used to allow X-polarized electromagnetic waves to be transmitted; the third metal patch layer 12 is used to allow Y-polarized electromagnetic waves to be transmitted.

[0009] The second metal patch layer 30 serves as a resonant structure for generating the phase difference between the linearly polarized electromagnetic wave and the input electromagnetic wave under linear polarization conditions. It includes an adjustable open octagonal deformable metal ring 31 and a resonant metal strip 32 located at the center of the cell structure. The resonant metal strip 32 is located inside the open octagonal metal ring 31 and does not contact the adjustable open octagonal deformable metal ring 31.

[0010] Technical effect: In the electromagnetic band, the equivalent circuit of the resonant structure of this invention is that the adjustable-opening octagonal deformable metal ring 31 and the resonant metal strip 32 form an equivalent capacitor, and the adjustable-opening octagonal deformable metal ring 31 and the resonant metal strip 32 themselves form equivalent inductances. The adjustable-opening octagonal deformable metal ring 31 of adjacent cell structures form an equivalent capacitor. Only by changing the opening size of the adjustable-opening octagonal deformable metal ring 31, the equivalent capacitor is changed. It is a metasurface structure based on the phase change of electromagnetic waves in pure phase holographic imaging.

[0011] This invention uses transmission line theory to realize the transmission of electromagnetic waves. By changing the coupling structure, the equivalent circuit is changed, which in turn causes a change in impedance and thus a change in phase.

[0012] In this embodiment, the first metal patch layer 11 mainly includes a first metal grating; and the first metal grating includes multiple first rectangular metal strips 110 parallel to the X-axis.

[0013] In this embodiment, the sum of the width of the first rectangular metal strip 110 and the spacing between two adjacent first rectangular metal strips 110 is 1 / 4 of the cell structure length.

[0014] In this embodiment, the third metal patch layer 12 mainly includes a second metal grating; and the second metal grating includes multiple second rectangular metal strips 120 parallel to the Y-axis.

[0015] In this embodiment, the sum of the width of the second rectangular metal strip 120 and the spacing between two adjacent second rectangular metal strips 120 is 1 / 4 of the cell structure length.

[0016] In this embodiment, the design process of the second metal patch layer 30 is as follows:

[0017] S11, at the center of the cell structure, set a regular octagonal deformable metal ring; rotate the regular octagonal deformable metal ring so that the regular octagonal deformable metal ring has two sides parallel to the X-axis and two sides parallel to the Y-axis.

[0018] S12, cut the octagonal deformed metal ring with a cutting rotation angle of psi to form an adjustable open octagonal deformed metal ring 31;

[0019] S13, a resonant metal strip 32 is set at the center of the cell structure and inside the adjustable open regular octagonal metal ring 31;

[0020] S14, the adjustable opening octagonal deformable metal ring 31 and the resonant metal strip 32 are rotated as a whole by an angle of alphal to form the second metal patch layer 30.

[0021] The order of steps S12 and S13 can be adjusted.

[0022] In this embodiment, the rotation angle alphal is 45°.

[0023] In this embodiment, the resonant metal strip 32 is "I" shaped.

[0024] This invention also provides a holographic imaging design method based on metasurfaces, which utilizes the aforementioned holographic imaging metasurface structure based on pure phase change, including:

[0025] S1, a cell structure is used as an image unit; according to the phase requirements of the image unit required to generate a holographic image, the cutting rotation angle psi of the opening size in the adjustable octagonal deformable metal ring 31 and the rotation angle alphal of the second metal patch layer 30 are used as optimization variables to optimize the size parameters of the second metal patch layer 30; wherein, the cutting rotation angle psi corresponding to each image unit is different.

[0026] S2, the image to be imaged is divided into phase hologram units of the array; random phase is added to the phase hologram units; the phase hologram units with random phase are iteratively restored using a mathematical model, and the restoration effect of the phase hologram units with random phase is checked. After the verification is correct, the phase hologram units are divided into phase plates, and the phase plates after division are iteratively restored using a mathematical model to obtain the step restoration image. At this time, the phase plate of the image to be imaged is obtained.

[0027] S3: Obtain the required phase based on the phase plate, and obtain image units with different cutting rotation angles (psi) based on S1, and perform simulation modeling; according to the parameters corresponding to each image unit calculated by phase control, find the parameter values ​​corresponding to the image unit in the scan parameters, and obtain the parameter setting values ​​of the image unit.

[0028] S4. After modeling the corresponding parameter settings for each image unit obtained in step S3, multiple image units are arrayed to form a metasurface.

[0029] In this embodiment, the length and width of the phase hologram unit are the same as the length and width of the image unit.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention utilizes an adjustable-opening regular octagonal metal ring. By adopting the form of a regular octagonal ring, it takes advantage of the anisotropic scattering characteristics generated by linearly polarized wave excitation to naturally generate a 180° phase difference over a wide frequency band.

[0032] This invention combines an adjustable-opening octagonal deformable metal ring and an I-shaped resonant metal strip, utilizing the characteristics of metasurface geometric phase and transmission phase principles to achieve a 360° phase change, thereby maintaining performance while increasing the transmission coefficient. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a holographic imaging metasurface structure based on pure phase change according to an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of the first metal patch layer in an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of the third metal patch layer in an embodiment of the present invention.

[0036] Figure 4 This is a schematic diagram of the second metal patch layer in an embodiment of the present invention.

[0037] Figure 5 This is a schematic diagram of the transmission coefficient of the required frequency band for the cell structure in an embodiment of the present invention.

[0038] Figure 6 This is a schematic diagram of the phase change during the psi transformation of the cutting rotation angle in an embodiment of the present invention.

[0039] Figure 7 The images shown are the original image, random phase, phase hologram unit, and restored image under Matlab simulation in this embodiment of the invention.

[0040] Figure 8 The image shows the phase plate and its graded reconstruction diagram under Matlab simulation in an embodiment of the present invention. Detailed Implementation

[0041] To facilitate understanding of the technical solution of the present invention by those skilled in the art, the technical solution of the present invention will now be further described in conjunction with the accompanying drawings.

[0042] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0043] Example 1

[0044] Please see Figure 1 As shown, the present invention provides a holographic imaging metasurface structure based on pure phase change. The metasurface includes multiple cellular structures, each of which includes: a first metal patch layer 11, a first dielectric material layer 21, a second metal patch layer 30, a second dielectric material layer 22 and a third metal patch layer 12 stacked sequentially.

[0045] The first metal patch layer 11 allows X-polarized electromagnetic waves to pass through while filtering out other polarization components. The third metal patch layer 12 allows Y-polarized electromagnetic waves to pass through while filtering out other polarization components. The second metal patch layer 30 serves as a resonant structure to generate the phase difference between the linearly polarized electromagnetic wave and the input electromagnetic wave under linear polarization conditions. It includes an adjustable open octagonal deformable metal ring 31 and a resonant metal strip 32 located at the center of the cell structure. The resonant metal strip 32 is located inside the open octagonal deformable metal ring 31 and does not contact the adjustable open octagonal deformable metal ring 31.

[0046] Please see Figures 1 to 3 As shown, in this embodiment, the first metal patch layer 11 mainly includes a first metal grating. The first metal grating includes multiple first rectangular metal strips 110 parallel to the X-axis. The sum of the width of the first rectangular metal strip 110 and the spacing between two adjacent first rectangular metal strips 110 is 1 / 4 of the cell structure length to achieve repeatability. In this embodiment, the length of the first rectangular metal strip 110 is p = 5 mm, the width is w1 = 0.2 mm, the spacing between two adjacent first rectangular metal strips 110 is w2 = 1.05 mm, and four first rectangular metal strips 110 are provided.

[0047] In this embodiment, the third metal patch layer 12 mainly includes a second metal grating. The second metal grating includes multiple second rectangular metal strips 120 parallel to the Y-axis. The sum of the width of the second rectangular metal strip 120 and the spacing between two adjacent second rectangular metal strips 120 is 1 / 4 of the cell structure length to achieve repeatability. In this embodiment, the length p of the second rectangular metal strip 120 is 5 mm, the width w1 is 0.2 mm, the spacing between two adjacent second rectangular metal strips 120 is w2 = 1.05 mm, and four second rectangular metal strips 120 are provided.

[0048] In this embodiment, the first dielectric material layer 21 and the second dielectric material layer 22 are made of F4B material with a length and width of p = 5 mm, a height ranging from 1.3 to 1.7 mm, preferably 1.5 mm, a relative permittivity of 2.65, and a tangent loss angle of 0.0009, which supports and connects the first metal patch layer 11 and the second metal patch layer 30.

[0049] Please see Figures 1 to 4 As shown, in this embodiment, the design process of the second metal patch layer 30 is as follows:

[0050] S11, at the center of the cell structure, set a regular octagonal deformable metal ring; rotate the regular octagonal deformable metal ring so that the regular octagonal deformable metal ring has two sides parallel to the X-axis and two sides parallel to the Y-axis.

[0051] In this embodiment, the inner diameter of the regular octagonal deformed metal ring is a regular octagon with a circumscribed circle radius r1 ranging from 1.25 to 1.85 mm and a vertex at (0, 1.55, 0). Its outer diameter is a regular octagon with a circumscribed circle radius r2 ranging from 2.1 to 2.4 mm and a vertex at (0, 2.3, 0). After rotating 22.5°, a regular octagonal deformed metal ring with two sides parallel to the X-axis and two sides parallel to the Y-axis is obtained.

[0052] In this embodiment, the difference between the outer and inner diameters of the octagonal deformable metal ring will change the selected frequency. The closer the size of the circumscribed circle is to the cellular structure, the greater the interference, which will lead to a change in frequency.

[0053] S12, cuts the octagonal deformed metal ring with a cutting rotation angle of psi to form an adjustable open octagonal deformed metal ring 31.

[0054] S13, a resonant metal strip 32 is set at the center of the cell structure and inside the adjustable open regular octagonal metal ring 31.

[0055] S14, the adjustable-opening octagonal deformable metal ring 31 and the resonant metal strip 32 are rotated as a whole by a rotation angle of alphal to form the second metal patch layer 30.

[0056] In this embodiment, the order of steps S12 and S13 is adjustable. The resonant metal strip 32 mainly includes a third rectangular metal strip, and two fourth metal strips are set at both ends of the third rectangular metal strip. The length of the third rectangular metal strip ranges from 112.3 to 2.7 mm, and the width ranges from 30.6 to 0.8 mm. The length of the fourth metal strip ranges from 0.8 to 1.1 mm, and the width ranges from 0.05 to 0.15 mm. Specifically, the resonant metal strip 32 is "I" shaped. The closer the length and width of the resonant metal strip 32 are to the adjustable-opening octagonal deformed metal ring 31, the stronger its equivalent capacitance and the change in frequency. Furthermore, the adjustable-opening octagonal deformed metal ring 31 and the resonant metal strip 32 are rotated 45° as a whole to achieve the maximum transmission coefficient.

[0057] In this embodiment, the metasurface comprises multiple cellular structures, each with a different phase. In this embodiment, the cutting rotation angle psi is taken at 5° intervals, ranging from 0° to 180°, resulting in different rotation angles alphal corresponding to the required cutting rotation angle psi for a fixed resonant frequency, yielding a total of 37 basic states.

[0058] Please see Figures 1 to 4 As shown, in this embodiment, when an electromagnetic wave is input, the first metal patch layer 11 transmits the X-polarized wave to the first dielectric material layer 21, and then transmits it to the second metal patch layer 30 via the first dielectric material layer 21. The adjustable-opening octagonal deformable metal ring 31 and the resonant metal strip 32 constitute an equivalent inductance. As a whole, the adjustable-opening octagonal deformable metal ring 31 and the resonant metal strip 32 constitute an equivalent capacitance. The adjustable-opening octagonal deformable metal ring 31 in adjacent cell structures constitutes an equivalent capacitance. After the electromagnetic wave is resonated by the second metal patch layer 30, it is transmitted through the second dielectric material layer 22 and then the Y-polarized wave is retained by the third metal patch layer 12.

[0059] In this embodiment, the present invention employs transmission line theory to achieve electromagnetic wave transmission. By changing the coupling structure, the equivalent circuit is altered, thereby causing impedance changes and achieving phase changes. The equivalent circuit of the present invention consists of an adjustable-aperture octagonal deformable metal ring 31 and a resonant metal strip 32 forming an equivalent inductance. As a whole, the adjustable-aperture octagonal deformable metal ring 31 and the resonant metal strip 32 form an equivalent capacitance. The adjustable-aperture octagonal deformable metal rings 31 in adjacent cell structures also form an equivalent capacitance. The present invention only changes the opening size of the adjustable-aperture octagonal deformable metal ring 31, thus changing only the equivalent capacitance.

[0060] Example 2

[0061] Please see Figures 1 to 4As shown, the present invention also provides a holographic imaging design method based on metasurfaces, which applies the holographic imaging metasurface structure based on pure phase change described in Example 1, including:

[0062] S1, a cell structure is taken as an image unit; according to the phase requirements of the image unit required to generate a holographic image, the cutting rotation angle psi of the opening size in the adjustable octagonal deformable metal ring 31 and the rotation angle alphal of the second metal patch layer 30 are optimized variables to optimize the size parameters of the second metal patch layer 30; wherein, the cutting rotation angle psi corresponding to each image unit is different.

[0063] In this embodiment, a portion with a rotation angle of psi is cut out from the octagonal deformed metal ring after rotation by an alphal angle, forming an adjustable open octagonal deformed metal ring 31. The cutting rotation angle psi is taken in 5° intervals, ranging from 0° to 180°. Different psi angles correspond to the cutting rotation angles required to fix the resonant frequency, resulting in a total of 37 basic states. Since the phase hologram of the holographic image is divided into 16 orders (i.e., 360° is evenly divided into 22.5° orders), it is necessary to select the required 16 states based on these 37 basic states.

[0064] S2, the image to be imaged is divided into phase hologram units of the array; random phase is added to the phase hologram units; the phase hologram units with added random phase are iteratively restored using a mathematical model, and the restoration effect of the phase hologram units with added random phase is checked. After the verification is correct, the phase hologram units are divided into phase plates, and the phase plates after division are iteratively restored using a mathematical model to obtain the step restoration image. At this time, the phase plate of the image to be imaged is obtained.

[0065] In this embodiment, the desired image is divided into 50x50 phase hologram units in Matlab. Random phases are then added, and the phase holograms with added random phases are subjected to GS (Gerchberg-Saxton) iterative reconstruction. The reconstruction effect of the phase hologram units with added random phases is verified. After verification, the phase hologram units are further divided into phase plates. The phase plates are then subjected to GS iteration to obtain the step reconstruction image, thus obtaining the phase plate of the desired image. The length and width of the phase hologram units are the same as the length and width of the image units, i.e., the unit period of the cell structure is Px = Py = 50. This invention does not limit the mathematical model; it only uses the GS algorithm for illustration. The GS algorithm gradually optimizes the phase distribution by alternately applying constraints (such as amplitude or phase conditions) in the spatial and frequency domains, and is commonly used for hologram calculation or wavefront shaping.

[0066] S3: Obtain the required phase based on the phase plate, and obtain image units with different cutting rotation angles (psi) based on S1, and perform simulation modeling; according to the parameters corresponding to each image unit calculated by phase control, find the parameter values ​​corresponding to the image unit in the scanning results, and obtain the parameter setting value of the image unit.

[0067] In this embodiment, the theoretical metasurface distribution required for imaging is designed based on the phase required by the phase plate and the basic state obtained based on S1. The HFSS full-wave simulation software is used for simulation modeling. The corresponding parameter values ​​are found in the scanning results according to the parameters of each image unit calculated by phase modulation, and the parameter setting values ​​of the image unit are obtained.

[0068] S4. After modeling the corresponding parameter settings for each image unit obtained in step S3, multiple image units are arrayed to form a metasurface.

[0069] In this embodiment, the metasurface array is modeled using HFSS software based on the parameter settings of each cell structure in the metasurface array obtained from Matlab.

[0070] Electromagnetic simulation tests were performed on the image unit with the above parameters, from Figure 5 The figure shows the electromagnetic simulation parameter curves of a metasurface unit based on the phase change of electromagnetic waves in pure phase holographic imaging when the psi parameter changes. It can be seen that the differential transmission coefficient is greater than 0.8 when the psi changes from 0° to 160° in the 8GHz-8.4GHz frequency band. Figure 5 The horizontal axis represents the aperture angle (psi), and the vertical axis represents the transmission coefficient. Several curves represent the selected frequencies. Figure 5 The curves in the figure show that, at the selected frequency, the transmittance remains above 0.8 as the psi changes, indicating a very high transmittance. From... Figure 6 It can be seen that the phase of the electromagnetic wave at port 2 (the port for transmitting electromagnetic waves) changes linearly with the change of psi. Figure 6 The horizontal axis represents psi, the vertical axis represents the phase at the 2-port, and the curves represent the selected frequencies. Figure 6 The linear change in the figure represents the result of a 5° step size chosen by psi. There will be some results that are not specifically simulated, but since it is a linear change, it can be inferred that it can cover the required phase change.

[0071] Figure 7 , 8 The simulation results of the AHU image after adding random phase and restoring it using the GS algorithm in Matlab simulation, as well as the output of the phase plate generated after dividing the phase hologram into levels, and the image restored by the phase plate, are used to verify the feasibility of realizing a metasurface for restoring pure phase holographic images.

[0072] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0073] The above embodiments are merely examples of implementation methods of the invention. The scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A holographic imaging metasurface structure based on pure phase change, characterized in that, The metasurface comprises multiple cellular structures; each cellular structure comprises: a first metal patch layer (11), a first dielectric material layer (21), a second metal patch layer (30), a second dielectric material layer (22), and a third metal patch layer (12) stacked sequentially; The first metal patch layer (11) is used to allow X-polarized electromagnetic waves to be transmitted; the third metal patch layer (12) is used to allow Y-polarized electromagnetic waves to be transmitted. The second metal patch layer (30) serves as a resonant structure for generating the phase difference between the linearly polarized electromagnetic wave and the input electromagnetic wave under linear polarization conditions. It includes an adjustable open octagonal deformable metal ring (31) and a resonant metal strip (32) located at the center of the cell structure. The resonant metal strip (32) is located inside the open octagonal metal ring (31) and does not contact the adjustable open octagonal deformable metal ring (31).

2. The holographic imaging metasurface structure based on pure phase change according to claim 1, characterized in that, The first metal patch layer (11) mainly includes a first metal grating; and the first metal grating includes multiple first rectangular metal strips (110) parallel to the X-axis.

3. The holographic imaging metasurface structure based on pure phase change according to claim 2, characterized in that, The sum of the width of the first rectangular metal strip (110) and the spacing between two adjacent first rectangular metal strips (110) is 1 / 4 of the cell structure length.

4. The holographic imaging metasurface structure based on pure phase change according to claim 1, characterized in that, The third metal patch layer (12) mainly includes a second metal grating; and the second metal grating includes multiple second rectangular metal strips (120) parallel to the Y-axis.

5. The holographic imaging metasurface structure based on pure phase change according to claim 4, characterized in that, The sum of the width of the second rectangular metal strip (120) and the spacing between two adjacent second rectangular metal strips (120) is 1 / 4 of the cell structure length.

6. The holographic imaging metasurface structure based on pure phase change according to claim 1, characterized in that, The design process of the second metal patch layer (30) is as follows: S11, at the center of the cell structure, set a regular octagonal deformable metal ring; rotate the regular octagonal deformable metal ring so that the regular octagonal deformable metal ring has two sides parallel to the X-axis and two sides parallel to the Y-axis. S12, cut the octagonal deformed metal ring with a cutting rotation angle of psi to form an adjustable open octagonal deformed metal ring (31); S13, at the center of the cell structure and inside the adjustable open regular octagonal metal ring (31), a resonant metal strip (32) is set; S14, the adjustable opening octagonal deformable metal ring (31) and the resonant metal strip (32) are rotated as a whole by an angle of alphal to form a second metal patch layer (30); The order of steps S12 and S13 can be adjusted.

7. The holographic imaging metasurface structure based on pure phase change according to claim 6, characterized in that, The rotation angle alphal is set to 45°.

8. The holographic imaging metasurface structure based on pure phase change according to claim 1, characterized in that, The resonant metal strip (32) is "I" shaped.

9. A holographic imaging design method based on metasurfaces, characterized in that, The application of the holographic imaging metasurface structure based on pure phase change according to any one of claims 1-8 includes: S1, take a cell structure as an image unit; according to the requirements of the phase of the image unit required to generate a holographic image, the cutting rotation angle psi of the opening size in the adjustable octagonal deformable metal ring (31) and the rotation angle alphal of the second metal patch layer (30) are optimized variables to optimize the size parameters of the second metal patch layer (30); wherein, the cutting rotation angle psi corresponding to each image unit is different. S2, the image to be imaged is divided into phase hologram units of the array; random phase is added to the phase hologram units; the phase hologram units with random phase are iteratively restored using a mathematical model, and the restoration effect of the phase hologram units with random phase is checked. After the verification is correct, the phase hologram units are divided into phase plates, and the phase plates after division are iteratively restored using a mathematical model to obtain the step restoration image. At this time, the phase plate of the image to be imaged is obtained. S3: Obtain the required phase based on the phase plate, and obtain image units with different cutting rotation angles (psi) based on S1, and perform simulation modeling; according to the parameters corresponding to each image unit calculated by phase control, find the parameter values ​​corresponding to the image unit in the scan parameters, and obtain the parameter setting values ​​of the image unit. S4. After modeling the corresponding parameter settings for each image unit obtained in step S3, multiple image units are arrayed to form a metasurface.

10. The holographic imaging design method based on metasurfaces according to claim 9, characterized in that, The length and width of the phase hologram unit are the same as the length and width of the image unit.

Images