Design method and system for acoustic holographic mask with variable patterns

Abstract

The invention discloses a design method of a variable pattern acoustical holography mask, which comprises the following steps: generating a random phase matrix, constructing an object plane initial complex amplitude field based on sound pressure distribution of the lower surface of an acoustical holography mask sheet and the random phase matrix, normalizing a gray value of a target image into a matrix, and taking the matrix as a target sound pressure distribution constraint condition, target phase distribution is solved based on a gradient acceleration iteration angular spectrum method; repeating the steps under different pressurization conditions to obtain target phase distribution under different pressure conditions, and determining optimal thickness distribution of the acoustical holography mask meeting different pressurization conditions simultaneously by using a direct search method; and generating an acoustic holographic mask sheet entity structure according to the thickness distribution. The invention further discloses a system corresponding to the design method. According to the design method and system provided by the invention, the single acoustical holographic mask can generate different target sound field patterns under different pressures by utilizing a phase regulation and control mechanism of an acoustic velocity variable material, so that single-mask multi-image loading is realized.

Description

Technical Field

[0001] This invention relates to the field of acoustic metamaterials, particularly sound field manipulation and acoustic holography, and especially to a design method and system for a variable pattern acoustic holographic mask. Background Technology

[0002] At present, two main methods are used for patterned focusing of surface acoustic wave excited sound fields: (1) single pattern focusing is achieved by processing the thickness structure of the transducer mask; (2) variable sound field distribution is achieved by using a transducer array and element-wise modulation. The above technical means can achieve a certain degree of sound field focusing effect. For example, Chinese Patent CN115625100A discloses a piezoelectric metasurface that can generate a specific sound field, including a piezoelectric material, on which a pre-designed patterned electrode is deposited. After the patterned electrode is positively and negatively polarized, a phase difference distribution of 0 and π is formed on the surface of the piezoelectric material, generating a sound field with a specific pattern. For example, Chinese patent CN121036721A discloses an integrated programmable surface acoustic wave (SAW) microparticle patterning manipulation system. The first surface of the piezoelectric substrate is provided with an interdigital transducer region, a manipulation region, and other regions. The interdigital transducer is used to realize bidirectional transmission of electrical and acoustic signals through the piezoelectric effect to control the sound field pattern in real time. The host computer is used to provide the waveform data and driving instructions required by the SAW signal source board. The SAW signal source board generates the resonant frequency required by the SAW transducer based on the waveform data and driving instructions, thereby exciting the SAW device to perform microparticle manipulation.

[0003] Among them, transducer masks have the advantages of simple manufacturing and high focusing accuracy, but once their structure is determined, they can only output a fixed sound field pattern and cannot freely switch the display content; transducer arrays have strong variability, but the array layout is complex, and the output sound field resolution is limited by the array element size and array scale, making it difficult to achieve high-precision patterned sound field control.

[0004] In summary, current surface acoustic wave (SAW) excitation sound field manipulation methods have the following shortcomings: The mask design can only output a fixed single pattern, lacking the ability to switch patterns. Existing SAW excitation sound field mask structures can only achieve a single pattern display after sound propagation manipulation, and cannot achieve dynamic switching between multiple patterns without changing the mask. This limits their application in scenarios requiring variable sound field focusing areas, such as acoustic manipulation, microfluidics, and biomedicine. Transducer array solutions suffer from limited display accuracy, structural complexity, and high cost.

[0005] Schemes represented by the existing technology CN120126625A (A Surface Acoustic Wave Holographic Metamaterial and Its Design Method) reconstruct the target sound field by assigning a discrete phase to each pixel through the difference in sound velocity of the material. However, this type of technology still has significant limitations. First, these holographic masks are all fixed structures, and their phase distribution cannot be changed after processing. Therefore, they can only output a single pattern and lack the ability to switch patterns or load multiple patterns according to different application requirements, resulting in insufficient flexibility. Second, most existing schemes use a finite number of discrete phase levels within the range of 0 to 2π for structural design, which is a typical multi-level discrete phase encoding method. Since the phase cannot be continuously adjusted, its resolution and fidelity are significantly limited, making it difficult to present the continuous grayscale distribution of complex sound fields, and constraining both imaging quality and reconstruction accuracy. In addition, in the phase design process, existing technologies usually use methods such as direct search and traversal optimization, searching for the optimal solution point by point within a finite phase set. The computational load of these methods is extremely large, increasing exponentially with the number of pixels, and they are prone to getting trapped in local optima, resulting in low design efficiency and difficulty in guaranteeing the globally optimal phase distribution.

[0006] There is currently a lack of a sound field control method that combines a monolithic structure, variable pattern display, and high-resolution focusing capabilities. Therefore, how to achieve switchable focusing of different patterned sound fields under a single mask structure has become an urgent problem to be solved. Summary of the Invention

[0007] The purpose of this invention is to provide a design method and system for a variable pattern acoustic holographic mask. The design method and system provided by this invention utilize the phase modulation mechanism of a material with variable sound velocity to enable a single acoustic holographic mask to generate different target sound field patterns under different pressures, thereby realizing multi-image loading on a single mask.

[0008] A method for designing a variable pattern acoustic holographic mask, the method comprising: (1) The lower surface of the acoustic holographic mask is uniformly divided into M*N discrete pixels. The sound field is discretized and simulated to obtain the sound pressure distribution. ; (2) Divide the target image into M*N discrete pixels, read the gray values ​​of the target image and normalize them into a matrix. ; (3) Generate a random M*N phase matrix Based on sound pressure distribution With random phase matrix Construct the initial complex amplitude field of the object surface and with As a constraint on the target sound pressure distribution, the target phase distribution is solved based on the gradient-accelerated iterative angular spectrum method. ; (4) Repeat steps (1)-(3) above under different pressure conditions to obtain the target phase distribution under different pressure conditions. The optimal thickness distribution of an acoustic holographic mask that simultaneously satisfies different pressure conditions was determined using a direct search method. (5) Generate an acoustic holographic mask model based on the thickness distribution obtained in step (4) and convert it into an acoustic holographic mask solid structure.

[0009] This invention is based on the principle of propagation phase difference caused by sound velocity difference. Under different pressures, the sound velocity of silicone changes → the wavenumber of the sound wave propagating in the raised area changes → the phase difference changes accordingly → the target sound field pattern automatically switches with pressure changes. Therefore, the same mask can achieve multiple patterned focused sound field outputs under different pressure conditions. In the specific implementation process, the phase distribution corresponding to multiple pressure conditions is obtained based on the gradient accelerated iterative angular spectrum method. Then, the thickness distribution of the acoustic holographic mask is solved based on the periodic phase matching and direct search method. Thus, the pressure-adjustable sound velocity characteristics of silicone material are used to realize the acoustic holographic mask structure with switchable sound field patterns, realizing a design method for single-mask multi-pattern sound field imaging using the phase difference of materials with variable sound velocity.

[0010] In this invention, the acoustic holographic mask is designed as a three-dimensional surface with multiple protrusions and depressions of varying heights. The mask and the external medium together form the sound wave propagation path. The medium fills the recessed areas of the mask, and the target sound field imaging plane is set inside the medium, with its planar range consistent with the upper surface of the mask, thereby ensuring that the sound field propagation areas match. Specifically, the upper surface of the acoustic holographic mask has multiple stepped protrusions of varying thicknesses, and the material is silicone; the medium is water, which fills the spaces between the protrusions of the acoustic holographic mask and between the acoustic holographic mask and the target plane. The velocity of sound in the medium is determined. The operating frequency of the piezoelectric element The object plane and image plane are divided into M*N segments, with a pixel side length of PIESIZE, and the wavelength in the liquid is calculated. , wave number .

[0011] In step (1), the sound pressure distribution on the surface of the piezoelectric sheet is simulated, normalized, and discretized into a matrix. ,matrix The size is M*N. Since the mask thickness is small, the sound pressure distribution on the upper surface (object surface) of the mask can be approximated as the sound pressure distribution on the lower surface (approximately the piezoelectric surface), i.e., the matrix... .

[0012] In step (2), the target image (image plane) is discretized into M*N discrete pixels, and the gray values ​​of the target image are read and normalized into a matrix. .

[0013] In step (3), specifically: (3-1) Based on sound pressure distribution With random phase matrix Construct the initial complex amplitude field of the object surface ; (3-2) Establish frequency domain coordinates , And construct an angular spectrum propagation operator based on sound field propagation parameters. and ; (3-3) Set the number of iterations, and perform the following operation in each iteration: (3-3-1) Based on and Calculate the complex amplitude field transmitted from the object plane to the image plane. ; (3-3-2) with As a constraint condition for the target sound pressure distribution, based on The complex amplitude field of the new image plane is obtained. ; (3-3-3) Based on and Calculate the complex amplitude field propagating backward from the image plane to the object plane. And extract a new phase of the surface ; (3-3-4) Based on A gradient acceleration strategy is used to speed up the phase update process and obtain the updated phase. ; (3-3-5) Based on the updated phase With sound pressure distribution Reconstructing the complex amplitude of the object surface ; (3-3-6) Calculate the loss function, quantitatively evaluate the quality of the current iteration result, and monitor the convergence process; (3-3-7) Repeat (3-3-1)-(3-3-6) until the set number of iterations is reached, then output the final phase. .

[0014] Furthermore, in (3-1), a random phase matrix of size M*N is generated. ∈[0,2π], construct the initial complex amplitude field: .

[0015] Furthermore, in (3-2), frequency domain coordinates are established. , And construct the angular spectrum propagation operator. and : ; ; in, j imaginary unit , d It is the distance between the object plane and the phase plane.

[0016] Furthermore, in (3-3-1), the complex amplitude field transmitted from the object plane to the image plane is calculated: the complex amplitude field of the object plane is transformed into the frequency domain to obtain its spatial spectrum and compared with the system's transfer function. Multiplying the two results in the spatial spectrum of the complex amplitude field of the image plane. Then, the inverse Fourier transform is used to convert the spectrum back to the spatial domain, yielding the complex amplitude field of the image plane. : ; Calculate image plane intensity and the complex amplitude field Normalization.

[0017] Furthermore, in (3-3-2), the phase plane constraint preserves the image plane phase. Using the target amplitude Replace Amplitude The complex amplitude field of the new image plane is obtained. : ; Furthermore, in (3-3-3), the complex amplitude field propagating backward from the image plane to the object plane is calculated: the complex amplitude field of the image plane is... Transform to the frequency domain to obtain its spatial spectrum and compare it with the system's inverse transfer function. Multiplying the two results in the spatial spectrum of the complex amplitude field of the object surface. Then, the inverse Fourier transform is used to convert the spectrum back to the spatial domain, yielding the complex amplitude field of the object surface. : ; New phase of the extract surface: .

[0018] Furthermore, in (3-3-4), a gradient acceleration strategy is used to accelerate the phase update method and speed up the iterative process: Let the phase difference be: ; Calculate the acceleration factor: ; Update the phase using the acceleration term and normalize it. (For acceleration parameters), where, After the last iteration : .

[0019] Furthermore, in (3-3-5), the complex amplitude of the object surface is reconstructed, and the updated phase is used. With sound pressure distribution Substitute into the complex amplitude field: .

[0020] Furthermore, in (3-3-6), the loss is calculated. Using PSNR, quantitatively evaluate the quality of the current iteration results and monitor the convergence process: .

[0021] In step (4), in order to achieve different patterned loading at the same target height under different pressures, it is necessary to calculate the phase of various different patterns multiple times using the above steps, which correspond to the display patterns of the acoustic holographic mask under different pressures.

[0022] In step (4), specifically: (4-1) Since the sound velocity of silicone changes with pressure, let the sound velocities corresponding to the two pressure states be respectively and wave number is and Based on phase periodicity, for each pixel satisfy: ; in , For any integer, and These correspond to the object phase of the two patterns, respectively; (4-2) Since sound waves attenuate to some extent when passing through silicone material, in order to reduce sound wave loss, the search range of m and n is limited to (-5, 5), and the equation conditions are relaxed to: ; in This is the set allowable error value; (4-3) Perform a traversal search on the equation to find the solution that best meets the conditions. Thickness distribution: 。

[0023] In step (5), 3D printing molds and casting processes are used to transform the calculated three-dimensional thickness distribution into a silicone mask solid structure.

[0024] The present invention also provides a design system for a variable pattern acoustic holographic mask that performs the method, the system comprising: The sound field modeling and simulation module is used to uniformly divide the lower surface of the acoustic holographic mask into M*N discrete pixels, perform discrete sound field modeling and simulation, and obtain and output the sound pressure distribution matrix A. The target image processing module is used to uniformly divide the input target image into M*N discrete pixels, read its grayscale values ​​and normalize them, and output the target sound pressure distribution matrix. ; The iterative phase solution module is used to receive the sound pressure distribution matrix A and the target sound pressure distribution matrix. A random phase matrix is ​​generated, and iterative calculations are performed based on the gradient-accelerated iterative angular spectrum method to solve and output the target phase distribution finalphasek that satisfies the target constraints. The multi-state phase processing module is used to control the repeated invocation of the sound field modeling and simulation module, the target image processing module and the iterative phase solving module under different pressure conditions to acquire and store multiple target phase distributions corresponding to different pressure conditions; The thickness optimization and determination module is used to receive the phase distribution of the multiple targets, apply the direct search method, and calculate and determine the optimal thickness distribution of the acoustic holographic mask based on the model of sound speed changing with pressure and the phase periodicity condition. The mask model generation and output module is used to generate a corresponding three-dimensional model of the acoustic holographic mask according to the optimal thickness distribution, and output it to the manufacturing equipment to generate a solid structure.

[0025] The present invention also provides an application of the above-described design method or design system in the fields of acoustic manipulation, microfluidic systems or biomedical engineering.

[0026] This invention utilizes the property that the sound velocity of a material changes with pressure, and determines the mask thickness through phase design and direct search method to achieve patterned sound field focusing that can switch with changes in external pressure. This solves the problem of traditional masks having a fixed single pattern that cannot be reconfigured, and has important application value in engineering fields such as acoustic particle manipulation and biological cell manipulation.

[0027] Compared with existing technologies, this invention has the following superior effects: This invention provides a variable-pattern acoustic holographic mask design method based on iterative optimization and direct search, combining sound wave propagation theory and angular spectrum diffraction models to achieve high-precision customized control of the target plane sound field pattern; by introducing a gradient acceleration strategy, the problem of slow iteration speed is effectively solved, significantly improving the speed and quality of acoustic holographic imaging. In particular, this invention innovatively employs a direct search method, determining the mask thickness distribution for pattern transformation under different sound velocities (pressures) by traversing and solving periodic phase-matching equations, thereby achieving controllable changes in acoustic holographic images under a single mask. The variable-pattern acoustic holographic mask design method proposed in this invention is applicable to complex external field environments and multi-physics coupling scenarios, and has significant application value in acoustic manipulation, microfluidic systems, and biomedical engineering. Attached Figure Description

[0028] Figure 1 A flowchart illustrating a design method for a variable pattern acoustic holographic mask provided in this embodiment; Figure 2 A schematic diagram of a variable pattern acoustic holographic mask provided for an embodiment; Figure 3 This is a cross-sectional view of the ultrasonic excitation component packaging method in the embodiment; Figure 4 The grayscale image of the target sound pressure distribution on the target plane is expected to be achieved in the design method of the variable pattern acoustic holographic mask provided in the embodiment. Figure 5 The silicone acoustic holographic mask structure obtained by reverse optimization in the design method of the variable pattern acoustic holographic mask provided in the embodiment; Figure 6 The grayscale image of the target plane sound pressure distribution obtained by theoretical calculation in the design method of the variable pattern acoustic holographic mask provided in the embodiment. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0030] The design method provided by this invention is implemented through the following system: consisting of a variable pattern acoustic holographic mask, a dielectric environment, an ultrasonic excitation component, a fixing device, and a signal driving system, such as... Figure 2 As shown: Acoustic holographic mask: The upper surface has multiple stepped protrusions of different thicknesses, and the material is silicone. Medium: Water is used to fill the spaces between the protrusions of the mask and between the mask and the target plane. Ultrasonic excitation device: includes a lead zirconate titanate piezoelectric ceramic sheet with flanged electrodes, a backing layer, a matching layer, and an encapsulation structure, such as... Figure 3 As shown, the encapsulated ultrasonic excitation assembly is cylindrical in shape, with a square base at the bottom and a circular through-hole near the bottom sidewall for leading out the electrode wires. The diameter of the upper opening is slightly smaller than the outer diameter of the cylinder, which serves to position and fix the piezoelectric sheet. During encapsulation, the backing layer is prepared first: the device is inverted, and the piezoelectric ceramic sheet with the pre-welded positive and negative electrode wires is placed in the opening, with the wires led out from the through-hole in the sidewall. Then, an appropriate amount of silicone is poured in, and it is left to stand for about 24 hours to fully cure. Next, the matching layer is prepared: the device is restored to its upright position, and another appropriate amount of silicone is poured into the upper opening, minimizing internal air bubbles. It is then left to stand for about 24 hours again to allow the matching layer to fully cure. Fixing device: A 3D-printed bracket with a groove on the lower side to secure the ultrasonic excitation component and a groove on the top to secure the acoustic holographic mask. The mask and transducer are kept parallel and at a fixed distance. Signal driving section: Signal generator + power amplifier, realizing surface acoustic wave excitation of the piezoelectric element. The positive and negative electrodes of the lead zirconate titanate piezoelectric ceramic sheet are connected to an external power amplifier, which is connected to the signal generator. The signal generator sends a sinusoidal signal to the power amplifier, which amplifies the signal and inputs it to the positive and negative electrodes of the lead zirconate titanate piezoelectric ceramic sheet. The positive and negative electrodes excite the piezoelectric ceramic sheet to generate surface acoustic waves, which form a sinusoidal sound field that is transmitted to the mask.

[0031] This embodiment enables the formation of two switchable patterned focused sound fields at a height of 50 mm from the acoustic holographic mask by surface acoustic wave excitation. The target patterns correspond to atmospheric pressure and 1 MPa pressurized environments, respectively. Figure 4 a in Figure 4 As shown in b in the figure.

[0032] like Figure 2 As shown, an ultrasonic excitation device is installed in a groove below the fixing device. The ultrasonic excitation assembly uses a lead zirconate titanate piezoelectric ceramic sheet as the sound source, and its encapsulation structure is as follows. Figure 3 As shown, silicone is used as both a matching layer and a backing layer. In the experiment, the acoustic wave operating frequency was 1MHz, and the acoustic holographic mask material was silicone with a planar dimension of 50mm × 50mm. The mask was fixed in a groove at the top of the device, aligning its center with the center of the ultrasonic excitation device. The entire device was placed in water, and the positive and negative electrodes of the piezoelectric ceramic sheet were connected to a power amplifier and a signal generator via wires, respectively. The piezoelectric transducer was excited on a lithium niobate substrate to generate surface acoustic waves that propagated along the surface, forming a specific sound field distribution on the piezoelectric sheet surface. Due to the thickness differences of each pixel on the mask surface, different propagation phases were introduced, ultimately achieving a patterned focused sound field in the target area.

[0033] like Figure 1 As shown, the variable pattern acoustic holographic mask design method of this embodiment includes the following steps: 1) Discretize the lower surface (piezoelectric surface) and upper surface (object surface) of the mask into 100*100 pixels.

[0034] 2) The sound pressure distribution on the lower surface of the mask (piezoelectric surface) was simulated and normalized using COMSOL Multiphysics simulation software. The sound pressure distribution data was then discretized into a 100*100 matrix. Since the mask thickness is small, the sound pressure distribution on the upper surface (object surface) of the mask can be approximated as the sound pressure distribution matrix on the mask surface. .

[0035] 3) Discretize the target image (image plane) into 100*100 pixels, read the grayscale value of each pixel in the target image and normalize it, and convert the grayscale value data into a matrix. .

[0036] 4) Use the rand function to randomly generate a 100*100 matrix. That is, each element follows a sequence from 0 to 2. The uniform distribution between them constructs the initial complex amplitude field of the object surface. Initialize frequency domain coordinates , And calculate the angular spectrum propagation function. With backpropagation function : ; .

[0037] 5) Set the number of iterations Each iteration includes: a) The propagation from the object plane to the image plane yields the complex amplitude field of the image plane. : ; Calculate image plane intensity and normalize; b, Phase constraint. Preserving phase. Using the target amplitude Replace Amplitude The complex amplitude field of the new image plane is obtained. : ; c, the image propagates backward to the object plane, yielding the complex amplitude field of the object plane. : ; New phase of the extract surface: ; d, Employ a gradient-accelerated phase update strategy: , ; ; e, Update complex amplitude: ; f, calculate the loss Using PSNR, quantitatively evaluate the quality of the current iteration results and monitor the convergence process: ; g, repeat step af, and after reaching the set number of iterations step, output the phase. .

[0038] 6) This embodiment uses Figure 4 The two target images shown (sound pressure is zero in pure black areas, maximum in pure white areas, and sound pressure is negatively correlated with grayscale in other areas) are as follows: a is the target image under normal pressure, and b is the target image under 1 MPa pressure. The phase corresponding to the target pattern is calculated through steps 2)-8). and .

[0039] This embodiment designs two patterned loading methods at the same target height under two different environmental pressures, with the sound velocity of the silicone material set at [value missing]. and The display shows that α is the multiple of the change in sound speed, and the sound speed of silicone material at normal pressure is... Increased to 1 MPa pressure , Speed ​​of sound in liquid piezoelectric element operating frequency Imaging height Number of horizontal and vertical grids pixel side length The wavelength in the liquid was calculated. , wave number Wavelength in silicone under normal pressure , wave number Wavelength after pressurization , wave number .

[0040] 7) To enable the mask to output under two different pressure conditions. and A thickness equation is established, and the search is extended using phase periodicity: ; in , For any integer, since sound waves attenuate to some extent when passing through silicone material, in order to reduce sound wave loss, [the following is omitted as it is not explicitly stated in the original text]. , The search range is limited to (-3, 3), and the equation conditions are relaxed to: ; in In order to be in , The minimum absolute value found within the search range.

[0041] Perform a traversal search on the equation to find the solution that best meets the conditions. The thickness distribution of the silicone acoustic holographic mask was obtained. : .

[0042] 8) Generate an STL model of the silicone mask based on the obtained thickness distribution, such as... Figure 5 As shown, the mask was fabricated using a molding process. A 60×60×10mm mold was constructed using the 3D software Magic. A Boolean difference operation was performed between the mold and the mask model to obtain the molding structure. The molding mold was then 3D printed. Liquid silicone was poured into the mold, and air bubbles were removed. After the silicone solidified, a silicone mask sheet was obtained. The outer edge of the mask has a locking structure approximately 1mm thick and 0.5mm wide, used to embed into the groove above the fixing device for stable installation. The mask body is discretely divided into 100×100 pixel units, each pixel corresponding to a different thickness distribution. Since the ultrasonic excitation component only generates effective sound pressure within a region with a central diameter of approximately 50mm, the acoustic holographic mask also exhibits thickness variation only within the corresponding circular region with a central diameter of 50mm, while the outer region maintains a preset uniform thickness.

[0043] The sound pressure distribution at the target height after the initial sound pressure field excited by the surface acoustic wave, propagating through the holographic metamaterial, can be calculated using the relationship between the sound propagation formula and the hydrostatic pressure-silica velocity. Figure 6 As shown (the sound pressure level is zero in pure black areas, maximum in pure white areas, and the sound pressure level in other areas is negatively correlated with grayscale), this is displayed under normal pressure as follows: Figure 6 In the figure, 'a' is displayed at a pressure of 1 MPa. Figure 6 In the formula 'b', the sound pressure distribution of the target plane is matched, thus achieving patterned focusing of the sound field on the target plane.

[0044] Based on the same technical concept, this invention also provides a design system for a variable pattern acoustic holographic mask that performs the aforementioned method, comprising: a sound field modeling and simulation module, used to uniformly divide the lower surface of the acoustic holographic mask into M*N discrete pixels, perform discrete sound field modeling and simulation, and obtain and output a sound pressure distribution matrix A; and a target image processing module, used to uniformly divide the input target image into M*N discrete pixels, read its grayscale values ​​and normalize them, and output a target sound pressure distribution matrix. The iterative phase solution module is used to receive the sound pressure distribution matrix A and the target sound pressure distribution matrix. The system generates a random phase matrix, performs iterative calculations based on the gradient-accelerated iterative angular spectrum method, solves for and outputs the target phase distribution finalphasek that satisfies the target constraints; a multi-state phase processing module controls the repeated invocation of the sound field modeling and simulation module, the target image processing module, and the iterative phase solving module under different pressure conditions to acquire and store multiple target phase distributions corresponding to different pressure conditions; a thickness optimization and determination module receives the multiple target phase distributions, applies a direct search method, and calculates and determines the optimal thickness distribution of the acoustic holographic mask based on the model of sound velocity changing with pressure and the phase periodicity condition; a mask model generation and output module generates the corresponding three-dimensional model of the acoustic holographic mask according to the optimal thickness distribution and outputs it to the manufacturing equipment to generate a solid structure.

[0045] It should be noted that when designing variable pattern acoustic holographic masks, the system provided in the above embodiments should be illustrated using the above-described division of functional modules. The functions can be assigned to different functional modules as needed, i.e., the internal structure of the terminal or server can be divided into different functional modules to complete all or part of the functions described above. Furthermore, the system provided in the above embodiments and the method embodiments of the present invention belong to the same concept; the specific implementation process is detailed in the embodiments of the method of the present invention, and will not be repeated here.

[0046] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for designing a variable pattern acoustic holographic mask, characterized in that, The design method includes: (1) The lower surface of the acoustic holographic mask is uniformly divided into M*N discrete pixels. The sound field is discretized and simulated to obtain the sound pressure distribution. ; (2) Divide the target image into M*N discrete pixels, read the gray values ​​of the target image and normalize them into a matrix. ; (3) Generate a random M*N phase matrix Based on sound pressure distribution With random phase matrix Construct the initial complex amplitude field of the object surface and with As a constraint on the target sound pressure distribution, the target phase distribution is solved based on the gradient-accelerated iterative angular spectrum method. ; (4) Repeat steps (1)-(3) above under different pressure conditions to obtain the target phase distribution under different pressure conditions. The optimal thickness distribution of an acoustic holographic mask that simultaneously satisfies different pressure conditions was determined using a direct search method. (5) Generate an acoustic holographic mask model based on the thickness distribution obtained in step (4) and convert it into an acoustic holographic mask solid structure.

2. The design method of the variable pattern acoustic holographic mask according to claim 1, characterized in that, In step (1), the sound pressure distribution on the surface of the piezoelectric sheet is simulated, normalized, and discretized into a matrix. ,matrix The size is M*N.

3. The design method of the variable pattern acoustic holographic mask according to claim 1, characterized in that, In step (3), specifically: (3-1) Based on sound pressure distribution With random phase matrix Construct the initial complex amplitude field of the object surface ; (3-2) Establish frequency domain coordinates , And construct an angular spectrum propagation operator based on sound field propagation parameters. and ; (3-3) Set the number of iterations, and perform the following operation in each iteration: (3-3-1) Based on and Calculate the complex amplitude field transmitted from the object plane to the image plane. ; (3-3-2) with As a constraint condition for the target sound pressure distribution, based on The complex amplitude field of the new image plane is obtained. ; (3-3-3) Based on and Calculate the complex amplitude field propagating backward from the image plane to the object plane. And extract a new phase of the surface ; (3-3-4) Based on A gradient acceleration strategy is used to speed up the phase update process and obtain the updated phase. ; (3-3-5) Based on the updated phase With sound pressure distribution Reconstructing the complex amplitude of the object surface ; (3-3-6) Calculate the loss function, quantitatively evaluate the quality of the current iteration result, and monitor the convergence process; (3-3-7) Repeat (3-3-1)-(3-3-6) until the set number of iterations is reached, then output the final phase. .

4. The design method of the variable pattern acoustic holographic mask according to claim 3, characterized in that, In (3-1), a random phase matrix of size M*N is generated. ∈[0,2π], construct the initial complex amplitude field: ； In (3-2), frequency domain coordinates are established. , And construct the angular spectrum propagation operator. and : ； 。 5. The design method of the variable pattern acoustic holographic mask according to claim 3, characterized in that, In (3-3-1), the complex amplitude field of the object surface is transformed into the frequency domain to obtain its spatial spectrum and compared with the system's transfer function. Multiplying the two results in the spatial spectrum of the complex amplitude field of the image plane. Then, the inverse Fourier transform is used to convert the spectrum back to the spatial domain, yielding the complex amplitude field of the image plane. : ; Calculate image plane intensity and the complex amplitude field Normalization; In (3-3-2), the image plane phase is preserved. Using the target amplitude Replace Amplitude The complex amplitude field of the new image plane is obtained. : ； In (3-3-3), the complex amplitude field of the image plane is... Transform to the frequency domain to obtain its spatial spectrum and compare it with the system's inverse transfer function. Multiplying the two results in the spatial spectrum of the complex amplitude field of the object surface. Then, the inverse Fourier transform is used to convert the spectrum back to the spatial domain, yielding the complex amplitude field of the object surface. : ； New phase of the extract surface: ; In (3-3-4), a gradient acceleration strategy is used to speed up the phase update process: Let the phase difference be: ； Calculate the acceleration factor: ； Update the phase using the acceleration term and normalize it. (For acceleration parameters): ； In (3-3-5), the complex amplitude of the object surface is reconstructed, and the updated phase is used. With sound pressure distribution Substitute into the complex amplitude field: 。 6. The design method of the variable pattern acoustic holographic mask according to claim 1, characterized in that, In step (4), specifically: (4-1) Let the sound velocities corresponding to the two pressure states be respectively and wave number is and Based on phase periodicity, for each pixel satisfy: ； in , For any integer, and These correspond to the object phase of the two patterns, respectively; (4-2) The search range of m and n is restricted to (-5, 5), and the equation conditions are relaxed to: ;in This is the set allowable error value; (4-3) Perform a traversal search on the equation to find the solution that best meets the conditions. Thickness distribution: 。 7. The design method of the variable pattern acoustic holographic mask according to claim 1, characterized in that, The upper surface of the acoustic holographic mask has multiple stepped protrusions of different thicknesses, and the material is silicone. The medium is water, which fills the spaces between the protrusions of the acoustic holographic mask and between the acoustic holographic mask and the target plane.

8. A design system for a variable pattern acoustic holographic mask that performs the method according to any one of claims 1-7, characterized in that, The system includes: The sound field modeling and simulation module is used to uniformly divide the lower surface of the acoustic holographic mask into M*N discrete pixels, perform discrete sound field modeling and simulation, and obtain and output the sound pressure distribution matrix A. The target image processing module is used to uniformly divide the input target image into M*N discrete pixels, read its grayscale values ​​and normalize them, and output the target sound pressure distribution matrix. ; The iterative phase solution module is used to receive the sound pressure distribution matrix A and the target sound pressure distribution matrix. A random phase matrix is ​​generated, and iterative calculations are performed based on the gradient-accelerated iterative angular spectrum method to solve and output the target phase distribution finalphasek that satisfies the target constraints. The multi-state phase processing module is used to control the repeated invocation of the sound field modeling and simulation module, the target image processing module and the iterative phase solving module under different pressure conditions to acquire and store multiple target phase distributions corresponding to different pressure conditions; The thickness optimization and determination module is used to receive the phase distribution of the multiple targets, apply the direct search method, and calculate and determine the optimal thickness distribution of the acoustic holographic mask based on the model of sound speed changing with pressure and the phase periodicity condition. The mask model generation and output module is used to generate a corresponding three-dimensional model of the acoustic holographic mask according to the optimal thickness distribution, and output it to the manufacturing equipment to generate a solid structure.

9. The application of the design method according to any one of claims 1-7 or the design system according to claim 8 in the fields of acoustic manipulation, microfluidic systems or biomedical engineering.

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