A multi-angle reuse design and simulation method and system for metasurface security lines

Abstract

The present invention discloses a multi-angle multiplexing design and simulation method and system for a metasurface security thread, belonging to the field of micro-nano optics and optical anti-counterfeiting technology, comprising: S1, pre-processing the acquired multi-type anti-counterfeiting images; S2, combining the pre-processed anti-counterfeiting images and the compensated amplitude distribution with the holographic phase map distribution to obtain the metasurface design phase distribution; S3, performing secondary encoding and interference superposition based on different target anti-counterfeiting image intensity distributions to obtain a multi-angle multiplexing phase distribution; S4, calculating the diffraction distance from the metasurface to each point on the observation plane, and obtaining the metasurface post-imaging phase distribution through amplitude superposition, inverse Fourier transform, and normalization; S5, splicing and integrating the multi-angle multiplexing metasurface units to generate a complete security thread image. The present invention achieves the design and simulation of a security thread with high security and multi-dimensional anti-counterfeiting features through micro-nano structure design, multi-physics field coupling simulation, and automated parameter adjustment.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano optics and optical anti-counterfeiting technology, and specifically relates to a multi-angle multiplexing design and simulation method and system for a metasurface security line. Background Art

[0002] In the field of optical anti-counterfeiting, the security thread is a special material strip embedded in the paper of a banknote. It has multiple anti-counterfeiting functions and is one of the core elements of banknote anti-counterfeiting technology. However, with the advancement of printing technology and the development of new scanning and printing technologies, the traditional security thread technology for banknote anti-counterfeiting is easily tampered with or counterfeited by criminals. The security of anti-counterfeiting needs to be improved to meet the increasingly complex anti-counterfeiting challenges. Existing research focuses on how to effectively integrate optics, materials science, and information technology to develop multi-faceted anti-counterfeiting solutions. For example, the 2015 edition of China's 100-yuan banknote debuted a "light-changing hollow window security thread," which dynamically changes color from magenta to green and displays the hollow character "Y100." The "multi-color magnetic security thread" developed by the China Banknote Research Institute improves machine-readable anti-counterfeiting levels through magnetic signal zoning encoding, and its technical level is close to international standards. The Japanese yen security thread uses a semi-buried design and photochromic materials to display dynamic features that appear and disappear under ultraviolet light.

[0003] Metasurfaces are two-dimensional metamaterials, typically composed of a single or few layers of artificial micro-nanostructures with wavelength or subwavelength thickness, exhibiting periodic or quasi-periodic arrays. The unit cell structure of a metasurface, also known as metaatoms, corresponds to the molecular atomic structure of traditional materials and can precisely control parameters such as the amplitude, polarization, and phase of light waves. Through careful design of metaatoms and global sequences, a variety of metasurfaces can be designed with specific capabilities for manipulating light waves, enabling ultra-compact and efficient optical devices for a new generation of integrated optics applications. For example, the paper "Research on Ultracompact Nanoprinting and Holographic Technology Based on Geometric Phase Control" (Wuhan University, 2023) proposes a nanoprinting technology based on geometric phase, encoding grayscale information through the steering angle of nanobricks; and the paper "Research on Multi-channel Nanoprinting and Computational Holography on Metasurfaces" (Wuhan University, 2020) proposes the use of transmission phase modulation to achieve multi-wavelength color holographic display. However, on-chip metasurface holography is a suitable optical anti-counterfeiting medium due to its extremely high counterfeit resistance, large information storage capacity, and high security. Furthermore, there is still ample room for exploration in multi-wavelength holographic multiplexing, holographic anti-counterfeiting encoding algorithms, and security thread anti-counterfeiting design. However, existing research has primarily focused on metasurface phase control mechanisms (such as geometric phase and transmission phase) and holographic image generation algorithms, lacking a comprehensive approach for the multi-angle multiplexing design and simulation of metasurface security threads.

[0004] Although existing research has made some progress in the phase control mechanism (such as geometric phase, transmission phase) and holographic image generation algorithm of metasurfaces, the following problems and shortcomings still exist: Insufficient multi-angle multiplexing coding: Traditional metasurface anti-counterfeiting technology mostly relies on a single incident angle and does not effectively utilize the multi-angle information multiplexing capability, resulting in limited anti-counterfeiting feature dimensions. Fragmentation of simulation process: Metasurface design relies on manual modeling (such as CST software) and parameter adjustment, and lacks automated tool chain support. For example, the research in the document "Multi-dimensional Metasurfaces and Their Applications in Information Encryption and Anti-Counterfeiting" (Infrared and Laser Engineering, 2020) verified the polarization conversion efficiency of nanobricks, but did not propose a full-process closed-loop method from image input to simulation optimization, resulting in a long design cycle and low efficiency.

[0005] Therefore, it is necessary to design a multi-angle reuse design and simulation method and system for metasurface security lines to address the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a multi-angle multiplexing design and simulation method for metasurface security threads, which can perform angle multiplexing coding, greatly reduce repetitive work, and improve simulation efficiency, in order to address the problems of insufficient research and application of multi-angle coding for angle multiplexing anti-counterfeiting in the existing security thread design and simulation processes, and process fragmentation during security thread design and simulation.

[0007] According to one aspect of this specification, a method for designing and simulating multi-angle multiplexing of a metasurface security thread is provided, comprising:

[0008] S1. Preprocessing the acquired multi-type anti-counterfeiting images;

[0009] S2. Combining the preprocessed multi-type anti-counterfeiting images and the compensated amplitude distribution with the holographic phase pattern distribution to form an object light wave for interferometric recording. Then, the designed phase distribution of the metasurface is obtained based on the holographic phase pattern distribution and the object light wave.

[0010] S3, based on different target anti-counterfeiting image intensity distributions, encode them into different holographic phase maps, and then re-encode them into different observation angles for interference superposition to obtain multi-angle multiplexed phase distribution;

[0011] S4. Based on the diffraction distance from the metasurface to each point on the observation plane and the multi-angle multiplexing phase distribution, simulated diffraction calculation and fast Fourier transform are performed. Then, the metasurface post-imaging phase distribution is obtained through amplitude superposition, inverse Fourier transform and normalization.

[0012] S5. Splice and integrate the multi-angle multiplexed metasurface units to generate a complete security thread image with a color bar.

[0013] Furthermore, the obtained multi-type anti-counterfeiting images are pre-processed, including:

[0014] Normalize and resize the obtained anti-counterfeiting image, and then convert it into a grayscale image;

[0015] The light intensity in the grayscale image is converted into amplitude, and the diffraction distortion is corrected using a Bessel function compensation algorithm.

[0016] Furthermore, a metasurface design phase distribution is obtained based on the holographic phase pattern distribution and the object light wave, including:

[0017] Based on the holographic phase pattern distribution, a plane light wave is selected to perform interference recording with the object light wave to obtain interference fringes;

[0018] Based on the recording principle of the metasurface holographic phase image, the corresponding phase distribution is proportional to the intensity distribution of the interference fringes, and the designed phase distribution of the metasurface is finally obtained.

[0019] Furthermore, the S2 further includes:

[0020] The obtained metasurface design phase distribution is displayed in a window of a mathematical software, and color mapping and amplification processing are performed on the metasurface design phase distribution.

[0021] Furthermore, the S3 further includes:

[0022] Based on the phase distribution of the secondary-encoded target anti-counterfeiting image, interference superposition is performed to obtain the complex amplitude distribution of the multi-angle multiplexing of the metasurface security line image;

[0023] The phase distribution of the complex amplitude distribution is retained, and the amplitude part is set to 1, and finally a multi-angle multiplexing phase distribution is obtained.

[0024] Furthermore, the amplitude superposition, inverse Fourier transform and normalization include:

[0025] The total incident light field of the anti-counterfeiting image is synthesized and converted into the frequency domain, and the complex amplitude of the incident light is calculated;

[0026] Based on the frequency domain and the complex amplitude of the incident light, a convolution calculation is used to obtain a plane complex amplitude distribution, and the light intensity information of the plane complex amplitude distribution is extracted to calculate the light intensity distribution and perform normalization.

[0027] Furthermore, simulated diffraction calculations and fast Fourier transforms are performed, including:

[0028] Calculate the distance from each element of the metasurface to each point on the observation plane, and improve the sampling density of the multi-angle multiplexing phase distribution through matrix expansion;

[0029] The Rayleigh-Sommerfeld diffraction integral function is used to calculate the plane light intensity distribution of the target anti-counterfeiting image and perform fast Fourier transform.

[0030] According to one aspect of this specification, a system for designing and simulating a multi-angle multiplexing metasurface security thread is provided, comprising:

[0031] A preprocessing module, used for preprocessing the acquired multi-type anti-counterfeiting images;

[0032] The metasurface design phase distribution module is used to combine the pre-processed multi-type anti-counterfeiting images and the compensated amplitude distribution with the holographic phase pattern distribution to form the object light wave for interference recording. The metasurface design phase distribution is then obtained based on the holographic phase pattern distribution and the object light wave.

[0033] The multi-angle multiplexing phase distribution module is used to encode different holographic phase maps based on the intensity distribution of different target anti-counterfeiting images, and then re-encode them into different observation angles for interference superposition to obtain multi-angle multiplexing phase distribution;

[0034] The metasurface post-imaging phase distribution module is used to perform simulated diffraction calculations and fast Fourier transforms based on the diffraction distances from the metasurface to each point on the observation plane and the multi-angle multiplexing phase distribution. The metasurface post-imaging phase distribution is then obtained through amplitude superposition, inverse Fourier transform, and normalization.

[0035] The security thread image generation module is used to splice and integrate multi-angle multiplexed metasurface units to generate a complete security thread image with color strips.

[0036] According to one aspect of this specification, an electronic device is provided, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the method for multi-angle multiplexing design and simulation of a metasurface security line are implemented.

[0037] According to one aspect of the present specification, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the multi-angle multiplexing design and simulation method of the metasurface security line are implemented.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. This invention significantly improves the anti-counterfeiting performance, design efficiency and anti-counterfeiting ability of the metasurface security thread by integrating a multi-angle phase coding algorithm, a multi-angle multiplexing mechanism and mathematical software design and simulation.

[0040] 2. This invention significantly improves the information density and anti-counterfeiting capability of anti-counterfeiting labels through micro-nanostructure design optimization, multi-physics field coupling simulation, and automated parameter adjustment, providing technical support for optical information security and high-density storage.

[0041] 3. The present invention supports the visual design of multi-angle multiplexed metasurface security threads, and supports the drawing and magnified viewing of holographic phase distribution diagrams and metasurface post-imaging simulation images. It can export the designed multi-angle multiplexed metasurface security thread phase distribution files and complete security thread image files with attached color bars. It has high design flexibility, can greatly reduce repetitive work, improve simulation efficiency, and save time spent in the design and simulation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0044] Figure 2 This is a flow chart of information processing according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] like Figure 1As shown, an embodiment of the present invention provides a multi-angle multiplexing design and simulation method for a metasurface security thread, comprising: step S1: inputting and preprocessing an anti-counterfeiting image; step S2: generating and encoding a holographic phase distribution; step S3: designing for multi-angle multiplexing; step S4: simulation calculation and imaging; and step S5: exporting results. This embodiment of the present invention utilizes mathematical software, combined with the principle of amplitude control of the holographic phase pattern diffraction angle and an intensity strategy for the holographic phase pattern diffraction angle, to develop an angle encoding algorithm to achieve multi-channel information encoding. Combining the metasurface's transmission phase, geometric phase, and hybrid phase control mechanisms with the developed multi-angle encoding algorithm, a comprehensive method is constructed. This method integrates the selection of multi-angle anti-counterfeiting security thread patterns (such as 0° and 30°), metasurface simulation condition settings (such as incident light wavelength, cell size, and reference light complex amplitude), design and simulation image visualization (such as holographic phase distribution images and post-lens imaging simulation images), and exporting the completed security thread design phase distribution file, thus achieving a comprehensive approach to metasurface security thread design.

[0047] Specifically, the embodiment of the present invention provides the following steps for step S1:

[0048] S1.1. Multi-type image input. The present invention supports the input of multiple types of anti-counterfeiting images (including "jpg," "png," and "bmp" formats), including high-resolution color images, high-resolution grayscale images, and anti-counterfeiting shading. The present invention enables visual selection of desired anti-counterfeiting images and displays the selected images in real time at designated locations within the mathematical software window.

[0049] S1.2. Image normalization and Bessel compensation. The selected anti-counterfeiting image is input into the process of the method of the present invention. The image data of the input anti-counterfeiting images is first normalized. The size of the input anti-counterfeiting image is automatically adjusted to match the metasurface unit. The adjusted anti-counterfeiting image is converted into a grayscale image. The converted grayscale anti-counterfeiting image is normalized. The light intensity of the normalized anti-counterfeiting image is converted into amplitude. The Bessel function compensation algorithm is applied to correct the diffraction distortion. The calculation formula is as follows:

[0050] (1)

[0051] in, is the target image intensity distribution, where is the two-dimensional coordinate of the target image, used to locate the position of each pixel, is the inverse function of the zero-order Bessel function, is the reference light amplitude.

[0052] S1.3. Coordinate system and parameter initialization. Set parameters such as the incident light wavelength, output image size, metasurface unit size, and reference light complex amplitude. Generate a gridded coordinate system that matches the metasurface array, ensuring a one-to-one correspondence between image pixels and nanobrick units.

[0053] (2)

[0054] in, is a set of coordinate vectors, is the function representation, is a one-dimensional coordinate vector.

[0055] Specifically, the embodiment of the present invention provides the following steps for step S2:

[0056] S2.1, Periodic phase calculation. Set the tilt angle , constructing a periodic phase distribution , corresponding to the phase delay caused by the oblique incidence of the plane wave:

[0057] (3)

[0058] in, is the wave number, is the size of the metasurface unit, λ is the working wavelength, substitute , which simplifies to:

[0059] (4)

[0060] This phase distribution can form a periodic grating structure to control the diffraction direction.

[0061] S2.2, complex amplitude of object light after Bessel compensation. The amplitude distribution of the input anti-counterfeiting image after preprocessing and compensation Respectively with the holographic phase map distribution Combined to form the object light wave for interference recording , expressed as:

[0062] (5)

[0063] Here, i represents the imaginary unit, which converts phase modulation into a complex operation.

[0064] S2.3. Interference recording. Holographic phase pattern distribution A plane light wave with an amplitude of R is selected to perform interference recording with the compensated object light wave. The interference fringes obtained by the interference recording can be expressed as:

[0065] (6)

[0066] S2.4. Phase distribution generation. According to the recording principle of the metasurface holographic phase image, the corresponding phase distribution is proportional to the intensity distribution of the interference fringes, so the final metasurface design phase distribution can be obtained by the following formula:

[0067] (7)

[0068] S2.5. Generate a visual holographic phase image distribution. Call the relevant functions in the mathematical software to display the metasurface design phase distribution of the anti-counterfeiting image calculated in S2.4 at a specific location in the mathematical software window. Set a color mapping and add a color bar. Also, call the function to enable free zooming, making it easier for users to observe the effect of the selected anti-counterfeiting image when displayed alone. In mathematical software, color bars are an important tool for data visualization, used to show the correspondence between colors and data values ​​in a graph.

[0069] Specifically, the embodiment of the present invention provides the following steps for step S3:

[0070] S3.1, target anti-counterfeiting image encoding. and Encoded into two different holographic phase images, the corresponding phase distribution is and , which can be further expressed as:

[0071] (8)

[0072] in, is the initial period phase distribution, is the inverse function of the Bessel function of the first kind, order 0.

[0073] S3.2. Secondary encoding of target anti-counterfeiting image. Based on the beam deflection capability of the phase grating, the encoded target anti-counterfeiting image information is secondary encoded into different observation angles to obtain the phase distribution after secondary encoding. and It can be expressed as:

[0074] (9)

[0075] in, and The phase distributions of different phase gratings have different period distributions, corresponding to different emission angles.

[0076] S3.3, interference superposition. The phase distribution of the target anti-counterfeiting image after secondary encoding is interfered and superimposed to obtain the complex amplitude distribution of the final metasurface security line image angle multiplexing. , the formula is as follows:

[0077] (10)

[0078] Here, an approximate treatment is adopted for the complex amplitude distribution obtained after the secondary encoding phase superposition, that is, only the phase distribution in the above complex amplitude distribution is retained, and the amplitude part is set to 1. Finally, the phase distribution on the metasurface is It can be obtained by the following formula:

[0079] (11)

[0080] in, It represents the phase angle of the complex number, that is, the angle (phase) of the complex number on the complex plane.

[0081] S3.4. Generate a visual holographic phase map distribution. Call the relevant functions in the mathematical software to display the phase distribution of the metasurface design combined with the anti-counterfeiting image after multi-angle multiplexing calculated in S3.3 at a specific location in the mathematical software window. Set a color mapping and add a color bar for it. At the same time, call the function to enable free zooming, allowing users to easily observe the effect of multi-wavelength multiplexing of the selected anti-counterfeiting image.

[0082] Specifically, the embodiment of the present invention provides the following steps for step S4:

[0083] S4.1. Diffraction distance calculation. Calculate the distance from each element of the metasurface to each point on the observation plane, and increase the sampling density through matrix expansion. The calculation formula is as follows:

[0084] (12)

[0085] in, is the diffraction distance, is the size of the hypersurface unit, ratio1 and ratio2 are the hypersurface expansion ratios of the two input anti-counterfeiting images, and z is the distance between the observation plane and the hypersurface.

[0086] S4.2. Simulated diffraction calculation and fast Fourier transform (FFT). The target plane light intensity distribution is calculated based on the Rayleigh-Sommerfeld diffraction integral function. The light field propagation characteristics are described by mathematical formulas and a two-dimensional fast Fourier transform is performed on it, as shown in formula (14):

[0087] (13)

[0088] (14)

[0089] in, is the complex amplitude transfer function, is the wave number, is the working wavelength, is the fast Fourier transformed , Represents two-dimensional fast Fourier transform.

[0090] S4.3, Amplitude superposition, inverse FFT and normalization. By synthesizing the total incident light field and converting it to the frequency domain, the complex amplitude of the incident light is calculated. The frequency domain representation of different anti-counterfeiting images is: ,in Represents the complex amplitude distribution of the metasurface, and then the plane complex amplitude distribution is obtained by the convolution theorem: ,in For the two-dimensional inverse Fourier transform, after completing the above steps, the light intensity information is extracted from the complex amplitude to calculate the light intensity distribution and normalize it:

[0091] (15)

[0092] (16)

[0093] in, is the complex amplitude of the observation plane, including phase information; is the complex conjugate of the complex amplitude at the observation plane, used to calculate the light intensity (eliminating the phase and retaining the amplitude); () indicates normalization processing.

[0094] S4.4. Generate a visualized metasurface post-imaging simulation image. Call the relevant functions in the mathematical software to display the multi-angle multiplexed metasurface post-imaging simulation image combined with the anti-counterfeiting image calculated in S4.3 at a specific location in the mathematical software window. Set a color mapping and add a color bar for it. At the same time, call the function to enable free zooming, making it easier for users to observe the effect of the metasurface post-imaging simulation image.

[0095] Specifically, the embodiment of the present invention provides the following steps for step S5:

[0096] S5.1. Export the final phase distribution. After selecting the image in step S1 and completing the calculations in S2, S3, and S4, you can export the final phase distribution file after multi-angle multiplexing in the mathematical software. After running the m file in the mathematical software, a TXT file storing the final phase distribution after multi-angle multiplexing will be generated and stored in a designated folder. This TXT file can then be quickly and easily imported into the optical simulation software for modeling and simulation analysis, allowing for further optical performance verification, multi-physics field coupling, and parameter optimization.

[0097] S5.2. Export the metasurface post-simulation image. After the image selection in step S1 and the calculation processes in S2, S3, and S4 are completed, you can choose to export the final phase distribution file of the metasurface post-simulation in the mathematical software. After running the m file in the mathematical software, a TXT file storing the final phase distribution of the metasurface post-simulation will be generated and stored in a designated folder. This TXT file can be easily and quickly imported into the optical simulation software for modeling and simulation analysis to further verify optical performance, multi-physics field coupling, and parameter optimization.

[0098] S5.3. Security Thread Stitching. Set the required security thread dimensions (length, width, etc.), call the relevant functions in the mathematical software, and stitch and integrate the encoded multi-angle multiplexing metasurface units. Finally, generate a complete security thread image and display it in a specific location in the mathematical software window. Set a color mapping and add a color bar for it. Also, call the function to enable free zooming, allowing users to easily observe the overall effect of the designed multi-angle multiplexing metasurface security thread.

[0099] Specifically, the present invention also provides Example 1, which designs a multi-angle multiplexed metasurface security thread that can display different anti-counterfeiting patterns at two different angles, such as the "100" and "Y" patterns. The specific steps of Example 1 include:

[0100] 1. Image input. Select two anti-counterfeiting images ("100.jpg" and "Y.png") as display patterns at two different angles. Load the images using the file selector in the MATLAB interface and display them in real time at the specified location.

[0101] 2. Image preprocessing: Convert all images to grayscale and normalize them to the range [0, 1]. Apply the Bessel compensation algorithm to correct for diffraction distortion. Set the incident light wavelength λ to 633 nm and the metasurface unit size c to 300 nm. Generate a gridded coordinate system to match the metasurface size to the image pixels.

[0102] 3. Holographic Phase Generation and Encoding. A periodic phase distribution is constructed to control the diffraction direction. The compensated amplitude is combined with the periodic phase to generate the complex amplitude of the object lightwave. A plane lightwave with amplitude R is selected to interfere with the compensated object lightwave. The resulting phase distribution is proportional to the intensity distribution of the interference fringes, generating a holographic phase distribution. The holographic phase distribution of the two selected images is visualized in MATLAB, with color bars added.

[0103] 4. Multi-angle multiplexing design. First, encode the target image and encode the two images into phase distributions. and . It is re-encoded and angle multiplexing gratings are added respectively. and Calculate the complex amplitude distribution after interference superposition, approximate the complex amplitude distribution obtained after secondary coded phase superposition, and extract the final phase distribution. Display the visual holographic phase distribution of the multi-angle multiplexed image in MATLAB and add a color bar.

[0104] 5. Simulation calculation and imaging. Calculate the distance from the metasurface to the observation plane using the diffraction distance calculation formula, and increase the sampling density through matrix expansion. Calculate the target light intensity distribution based on the Rayleigh-Sommerfeld diffraction integral function, describe the light field propagation characteristics, perform a fast Fourier transform on it, and then synthesize the total incident light field and convert it to the frequency domain to calculate the complex amplitude of the incident light. Calculate the plane complex amplitude according to the convolution theorem. After completing the above steps, extract the light intensity information for light intensity calculation and normalization. Display the visual holographic phase distribution diagram of the multi-angle multiplexed image in MATLAB and add a color bar.

[0105] 6. Export results. Save the final phase distribution as a TXT file and export the final phase distribution of the multi-angle multiplexing metasurface for subsequent simulation or manufacturing. Save the metasurface post-imaging simulation image as a TXT file and export the metasurface post-simulation results for optical performance verification. Integrate and splice the metasurface units into a complete multi-angle multiplexing metasurface security thread of the required size and display it in MATLAB with a color bar.

[0106] Specifically, this embodiment of the present invention also provides implementation steps when multi-angle multiplexing is not used: first, select an image ("100.jpg") as input, perform image preprocessing and holographic phase generation and encoding, then directly calculate diffraction imaging, and finally perform simulation calculation and imaging. In summary, the results analysis shows that only supporting single-pattern display has low information capacity and is less difficult to counterfeit. The cost of counterfeiting is only 50% of that of a multi-angle multiplexing solution. Since multi-angle encoding is not required, the design cycle is shortened by 30%, but the anti-counterfeiting effect is significantly reduced.

[0107] Specifically, the present invention also provides implementation steps when Bessel compensation is not used: first, input the image, then perform image preprocessing, skip Bessel compensation, and directly use the normalized amplitude for phase encoding. Next, perform holographic phase generation and encoding, directly calculate the diffraction image, and finally perform simulation calculation and imaging. The above results show that diffraction distortion is significant, pattern edges are blurred, and the signal-to-noise ratio is reduced. Due to the reduced imaging quality, the difficulty of counterfeiting is reduced. The design cycle is shortened by 10%, but the anti-counterfeiting effect is significantly reduced.

[0108] Specifically, an embodiment of the present invention also provides an alternative to the data acquisition method, using higher-resolution images, such as 4096×4096 pixels, which increases the computational complexity. The effect of the replacement is: it can provide more accurate anti-counterfeiting details after encoding calculation, but it will greatly increase the computational complexity and the difficulty of metasurface design, simulation, and production, and reduce the design simulation efficiency. The medium-resolution image used in this technology can meet the requirements of anti-counterfeiting accuracy while taking into account the design simulation efficiency.

[0109] Specifically, embodiments of the present invention also provide an alternative to the phase encoding algorithm. This method, which uses Python for deep learning after export and then imports it into MATLAB to generate the phase distribution, requires a large amount of training data. While this alternative improves the quality of the phase distribution, it increases computational and implementation complexity, failing to address the current fragmentation of design and simulation. This technical solution uses only MATLAB for phase encoding and generation, integrating the design and simulation process while effectively generating the required phase encoding, improving research and development efficiency.

[0110] Specifically, embodiments of the present invention also provide for the use of alternative analytical coding methods, such as finite element analysis (FEA), to replace Rayleigh-Sommerfeld diffraction for simulation calculations. These methods employ different probabilistic reasoning methods or deep learning models to handle more complex dependencies. While this substitution improves computational accuracy, it also increases process complexity and computational cost. This technical solution, using Rayleigh-Sommerfeld diffraction, effectively reduces computational complexity, improves design simulation efficiency, and ensures simulation accuracy and precision.

[0111] The implementation of each embodiment of the present invention is based on programmed processing performed by a device with processor functionality. Therefore, in practical engineering, the technical solutions and functions of each embodiment of the present invention are encapsulated into various modules. Based on this reality, and in addition to the aforementioned embodiments, an embodiment of the present invention provides a metasurface security thread multi-angle multiplexing design and simulation system. This system is used to implement the metasurface security thread multi-angle multiplexing design and simulation method described in the aforementioned method embodiment.

[0112] The system includes: a preprocessing module for preprocessing the acquired multi-type anti-counterfeiting images; a metasurface design phase distribution module for combining the preprocessed multi-type anti-counterfeiting images and the compensated amplitude distribution with the holographic phase map distribution to form an object light wave for interference recording, and then obtaining the metasurface design phase distribution based on the holographic phase map distribution and the object light wave; a multi-angle multiplexing phase distribution module for encoding different target anti-counterfeiting image intensity distributions into different holographic phase maps, and then secondary encoding them into different observation angles for interference superposition to obtain a multi-angle multiplexing phase distribution; a metasurface post-imaging phase distribution module for performing simulated diffraction calculation and fast Fourier transform based on the diffraction distance from the metasurface to each point on the observation plane and the multi-angle multiplexing phase distribution, and then obtaining the metasurface post-imaging phase distribution through amplitude superposition, inverse Fourier transform and normalization; a security line image generation module for splicing and integrating the multi-angle multiplexing metasurface units to generate a complete security line image with a color bar.

[0113] An embodiment of the present invention provides a multi-angle multiplexing design and simulation system for a metasurface security thread. This system addresses the problem of insufficient research and application of multi-angle coding for angle multiplexing anti-counterfeiting in existing security thread design and simulation processes. By integrating a multi-angle phase coding algorithm, a wavelength multiplexing mechanism, and mathematical software design and simulation, it adopts several modules to significantly improve the anti-counterfeiting performance, design efficiency, and anti-counterfeiting capability of the metasurface security thread.

[0114] Based on the same inventive concept as the above-mentioned embodiment, an embodiment of the present invention also provides an electronic device, including a memory and a processor, the memory is used to store computer-executable instructions, and the processor is used to execute computer-executable instructions to implement a multi-angle multiplexing design and simulation method of a metasurface security line proposed in the above-mentioned embodiment.

[0115] Embodiments of the present invention also provide a computer-readable storage medium storing a computer program. When executed by a processor, this program addresses the fragmentation and inefficiency of existing design processes, enabling rapid design and verification of security threads with high security and multi-dimensional anti-counterfeiting features. Through micro-nanostructure design optimization, multi-physics field coupling simulation, and automated parameter adjustment, this program significantly improves the information density and anti-counterfeiting capabilities of anti-counterfeiting labels, providing technical support for optical information security and high-density storage.

[0116] The storage medium can be any non-volatile storage device such as a hard disk, solid-state drive, flash drive, optical disk, etc., which is used to store computer program code and necessary data files. The stored computer program includes: a preprocessing module, a metasurface design phase distribution module, a multi-angle multiplexing phase distribution module, a metasurface post-imaging phase distribution module, and a security line image generation module.

[0117] Finally, it should be noted that the above specific embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above specific embodiments and is susceptible to numerous variations. Any simple modifications, equivalent variations, and modifications to the above specific embodiments based on the technical essence of the present invention shall be deemed to fall within the scope of protection of the present invention.

Claims

1. A multi-angle multiplexing design and simulation method for a metasurface security thread, characterized in that: include: S1. Preprocessing the acquired multi-type anti-counterfeiting images; S2. Combining the preprocessed multi-type anti-counterfeiting images and the compensated amplitude distribution with the holographic phase pattern distribution to form an object light wave, and then obtaining the metasurface design phase distribution based on the holographic phase pattern distribution and the object light wave; S3, based on different target anti-counterfeiting image intensity distributions, encode them into different holographic phase maps, and then re-encode them into different observation angles for interference superposition to obtain multi-angle multiplexed phase distribution; S4. Based on the diffraction distance from the metasurface to each point on the observation plane and the multi-angle multiplexing phase distribution, simulated diffraction calculation and fast Fourier transform are performed. Then, the metasurface post-imaging phase distribution is obtained through amplitude superposition, inverse Fourier transform and normalization. S5. Splice and integrate the multi-angle multiplexed metasurface units to generate a complete security thread image with a color bar.

2. The method for multi-angle multiplexing design and simulation of a metasurface security thread according to claim 1, characterized in that: Preprocess the acquired multi-type anti-counterfeiting images, including: Normalize and resize the obtained anti-counterfeiting image, and then convert it into a grayscale image; The light intensity in the grayscale image is converted into amplitude, and the diffraction distortion is corrected using a Bessel function compensation algorithm.

3. The method for multi-angle multiplexing design and simulation of a metasurface security thread according to claim 1, characterized in that: The metasurface design phase distribution is obtained based on the holographic phase pattern distribution and the object light wave, including: Based on the holographic phase pattern distribution, a plane light wave is selected to perform interference recording with the object light wave to obtain interference fringes; Based on the recording principle of the metasurface holographic phase image, the corresponding phase distribution is proportional to the intensity distribution of the interference fringes, and the designed phase distribution of the metasurface is finally obtained.

4. The method for multi-angle reuse design and simulation of a metasurface security thread according to claim 1, characterized in that: Said S2 further includes: The obtained metasurface design phase distribution is displayed in a window of a mathematical software, and color mapping and amplification processing are performed on the metasurface design phase distribution.

5. The method for multi-angle reuse design and simulation of a metasurface security thread according to claim 1, characterized in that: Said S3 further includes: Based on the phase distribution of the secondary-encoded target anti-counterfeiting image, interference superposition is performed to obtain the complex amplitude distribution of the multi-angle multiplexing of the metasurface security line image; The phase distribution of the complex amplitude distribution is retained, and the amplitude part is set to 1, and finally the multi-angle multiplexing phase distribution is obtained.

6. The method for multi-angle reuse design and simulation of a metasurface security thread according to claim 1, characterized in that: The amplitude superposition, inverse Fourier transform and normalization include: The total incident light field of the anti-counterfeiting image is synthesized and converted into the frequency domain, and the complex amplitude of the incident light is calculated; Based on the frequency domain and the complex amplitude of the incident light, a convolution calculation is used to obtain a plane complex amplitude distribution, and the light intensity information of the plane complex amplitude distribution is extracted to calculate the light intensity distribution and perform normalization.

7. The method for multi-angle reuse design and simulation of a metasurface security thread according to claim 1, characterized in that: Perform simulated diffraction calculations and fast Fourier transforms, including: Calculate the distance from each element of the metasurface to each point on the observation plane, and improve the sampling density of the multi-angle multiplexing phase distribution through matrix expansion; The Rayleigh-Sommerfeld diffraction integral function is used to calculate the plane light intensity distribution of the target anti-counterfeiting image and perform fast Fourier transform.

8. A multi-angle multiplexing design and simulation system for a metasurface security thread, characterized in that: include: A preprocessing module, used for preprocessing the acquired multi-type anti-counterfeiting images; The metasurface design phase distribution module is used to combine the pre-processed multi-type anti-counterfeiting images and the compensated amplitude distribution with the holographic phase pattern distribution to form the object light wave for interference recording. The metasurface design phase distribution is then obtained based on the holographic phase pattern distribution and the object light wave. The multi-angle multiplexing phase distribution module is used to encode different holographic phase maps based on the intensity distribution of different target anti-counterfeiting images, and then re-encode them into different observation angles for interference superposition to obtain multi-angle multiplexing phase distribution; The metasurface post-imaging phase distribution module is used to perform simulated diffraction calculations and fast Fourier transforms based on the diffraction distances from the metasurface to each point on the observation plane and the multi-angle multiplexing phase distribution. The metasurface post-imaging phase distribution is then obtained through amplitude superposition, inverse Fourier transform, and normalization. The security thread image generation module is used to splice and integrate multi-angle multiplexed metasurface units to generate a complete security thread image with color strips.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the multi-angle multiplexing design and simulation method of the super-surface security line according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for multi-angle multiplexing design and simulation of a super-surface security line according to any one of claims 1 to 7 are implemented.

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