A conversion device for an acoustic wave front

Abstract

This invention discloses an acoustic wavefront conversion device, comprising multiple discretized artificial microstructure units. These units, arranged in a determined manner, form a multi-layered, multi-column matrix structure. The discretized artificial microstructure units include "T"-shaped and "U"-shaped branch structures, with the "T"-shaped structure positioned above the "U"-shaped structure. The "T"-shaped unit structure includes horizontal and vertical units that intersect perpendicularly. The "U"-shaped unit structure includes vertical structures on both sides and horizontal structures connected to the vertical structures, with the vertical structures having the same length as the vertical units. When a sound wave enters the device and interacts with the carefully designed unit structures, the refractive index of the sound wave exhibits a gradual change along its travel space due to the different equivalent acoustic parameter responses of each unit structure. This gradual change in refractive index allows for the conversion of the acoustic wavefront.

Description

Technical Field

[0001] This invention relates to the field of acoustic detection technology, specifically to an acoustic wavefront conversion device. Background Technology

[0002] In the field of electromagnetic and optical manipulation, electromagnetic waves and optical fields can be controlled using electromagnetic metamaterials and transformation optics. The resulting control functions and devices are not found in many natural materials. Sound waves, as a type of classical wave, are closely related to people's daily lives and have therefore received widespread attention, just like light and electromagnetic waves. Because they play a crucial role in communication, voice recognition, seismic exploration, underwater detection, ultrasonic testing, and noise control, effectively controlling the propagation of sound waves is of great research significance and application value.

[0003] Shortly after the discovery of photonic crystals, similar phononic crystals were proposed in the field of acoustics and widely used to modulate sound propagation. With further research, the concepts of acoustic metamaterials and metasurfaces were subsequently proposed. These artificial acoustic metastructures can be designed to produce unusual and unconventional effects, differing significantly from natural materials, and possess unique control over sound waves. However, compared to acoustic metamaterials and metasurfaces, phononic crystals have drawbacks such as larger size and less convenient integration design for various environments; conventional acoustic metamaterials, due to their pursuit of negative equivalent density or negative elastic modulus, struggle to achieve a wide operating frequency bandwidth. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the shortcomings of the prior art, the present invention provides an acoustic wavefront conversion device, which solves the above-mentioned technical problems.

[0005] Technical Solution: This invention provides an acoustic wavefront conversion device, which includes multiple microstructure units. After the arrangement of the multiple microstructure units is determined, they form a multi-layer, multi-column matrix structure. The interior of each microstructure unit includes a "T"-shaped branch structure and a "U"-shaped branch structure. The "T"-shaped branch structure is placed above the "U"-shaped branch structure, and the "T"-shaped branch structure includes horizontal units and vertical units. The horizontal units and vertical units intersect perpendicularly. The "U"-shaped branch structure includes vertical structures on both sides and horizontal structures connected to the vertical structures. The vertical structures and vertical units have the same length, denoted as d.

[0006] Furthermore, including:

[0007] Methods for determining the arrangement of microstructural units include:

[0008] (1) Set up the structure of the simulated wavefront conversion device, and set a cylindrical wave emission source at the center of the simulated wavefront conversion device;

[0009] (2) Calculate the equivalent acoustic parameters of the cylindrical wave for waveform conversion based on the relevant parameters of the simulated wavefront conversion device;

[0010] (3) Discretize the simulated wavefront conversion device to obtain multiple positions, and determine the arrangement position of each microstructure unit according to the equivalent acoustic parameters.

[0011] Furthermore, including:

[0012] The structure of the simulated wavefront conversion device is as follows: the exterior is a square, and the interior of the square contains an inner circle and an outer circle. The radius of the inner circle is set to 'a', the radius of the outer circle is set to 'b', and the side length of the square is set to 2c. .

[0013] Furthermore, including:

[0014] Step (2) specifically includes: in a triangle with the cylindrical wave emission source as one vertex and the two adjacent vertices of the square as the other two vertices, x' y' z' are the spatial coordinates in the transformation medium region, and x, y, z are the coordinates in real space, and the two have the following relationship:

[0015] = ,

[0016] = ,

[0017] Using the above equations, the Jacobian transformation matrix is ​​obtained as follows:

[0018]

[0019] Then, the constitutive parameter tensor of the medium in the transformation space, i.e., the equivalent acoustic parameters, is obtained through the Helmholtz equation:

[0020]

[0021]

[0022] in, B represents the density and elastic modulus of the medium in real space. , The converted medium density and elastic modulus are given by det(). The rank of a matrix.

[0023] Furthermore, including:

[0024] Step (3) specifically includes:

[0025] The simulated wavefront conversion device features an internal circular arc distribution and an external square distribution. The arrangement of its microstructure units is designed through the following steps: First, the conversion function of the acoustic wave is calculated according to the conversion function to obtain the theoretical parameter distribution of the equivalent density and elastic modulus of the cylindrical wave after passing through the conversion device; Second, the conversion device is discretized, and each pixel retains the theoretical parameter value at that location; Third, microstructure units are placed into the corresponding pixels, based on the principle that the refractive index of the microstructure unit at that pixel is consistent with the theoretical refractive index at that location; Fourth, after all discrete pixels have been filled with microstructure units, the array structure is fixed onto the substrate material.

[0026] Furthermore, including:

[0027] The theoretical refractive index pass The refractive index of the microstructure unit is obtained by the specific structure of the designed microstructure unit. Furthermore, by changing the d-structure size of the microstructure unit at different positions within the device, the theoretical refractive index that the position should satisfy can be adjusted.

[0028] Furthermore, including:

[0029] The microstructure unit uses ABS or photosensitive resin as the base material.

[0030] Furthermore, including:

[0031] The solid structure of the discrete artificial microstructure unit is fabricated using 3D printing technology.

[0032] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are as follows:

[0033] (1) This invention is based on the theory of transformation acoustics. It arranges the structure with different discrete structural parameters “T” and “U” in an orderly array, with a total of 7 layers. There are two main considerations for choosing such a structure: first, the selected structure should be able to adjust the refractive index of the sound wave to meet the theoretical refractive index requirements; second, the structure should have the widest possible operating bandwidth.

[0034] When a sound wave passes through the device, due to the different positions and sizes of the discrete structural units within the device, the refractive index of the cylindrical sound wave changes to different degrees as it passes through different structural units. The refractive index changes regularly from the inner layer to the outer layer, and eventually the sound wave deviates from its original path, transforming from a cylindrical wave into a plane wave and propagating in a fixed direction. To ensure that the cylindrical wave transforms into a plane wave, the reverse design method adopted in this invention performs a reverse functional conversion under the premise of ensuring that the outgoing wave is a plane wave. Based on conformal transformation and the invariance of the wave equation form, the final functional transformation is specifically manifested as a coordinate transformation of geometric parameters, thereby obtaining the theoretical parameters of the transformed medium. With such theoretical parameters, the desired plane wave conversion effect can be achieved.

[0035] (2) In the frequency range of 3kHz to 8kHz, this invention can convert the target object into multiple plane waves simply by covering the target object with the wavefront conversion device. At the same time, there are no fixed requirements on the size and shape of the target object, and it has a wide range of applications.

[0036] (3) The solution of the present invention also has the advantage of bandwidth. Its structure is simple and can be made of photosensitive resin by 3D printing technology. Its small size makes it easy to use. It can be used in directional sound wave propagation applications and can be widely used in the field of acoustic engineering.

[0037] Therefore, this scheme proposes to apply the concept of coordinate transformation to reverse design the acoustic wave array transformation function, obtain theoretical parameters, and use these as a guide to compile the actual structure of the device, thereby obtaining a broadband acoustic functional device that can be customized in size. Attached Figure Description

[0038] Figure 1 This is a schematic diagram illustrating the working principle of the wavefront converter according to an embodiment of the present invention, wherein... Figure 1 (a) is a schematic diagram of the simulated wavefront conversion device. Figure 1 (b) is the truncated portion Figure 1 Partial rectangular diagram in (a), Figure 1 (c) is the refractive index distribution of the cut rectangular plot;

[0039] Figure 2 This is a model diagram of the wavefront converter described in an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram related to the 2000Hz frequency described in an embodiment of the present invention, wherein... Figure 3 (a) is a simulation diagram of the sound field distribution. Figure 3 (b) is a diagram showing the directional distribution of the external field of the sound wave in the theoretical simulation;

[0041] Figure 4 This is a schematic diagram illustrating the relevant parameters at 4000Hz as described in an embodiment of the present invention. Figure 4 (a) is a simulation diagram of the sound field distribution. Figure 4 (b) is a diagram showing the directional distribution of the external field of the sound wave in the theoretical simulation;

[0042] Figure 5 This is a schematic diagram related to the 8000Hz frequency described in an embodiment of the present invention, wherein... Figure 5 (a) is a simulation diagram of the sound field distribution. Figure 5 (b) is a diagram showing the directional distribution of the external field of the sound wave in the theoretical simulation;

[0043] Figure 6 This is a design diagram of the unit structure described in an embodiment of the present invention;

[0044] Figure 7 This is a graph showing the relationship between frequency, d-value, and refractive index as described in an embodiment of the present invention. Figure 7 (a) is a schematic diagram of the refractive index of the unit structure at different frequencies with different d values. Figure 7 (b) is a schematic diagram showing the relationship between refractive index and frequency for different d values;

[0045] Figure 8 This is a diagram showing the refractive index distribution in an acoustic lens according to an embodiment of the present invention.

[0046] Figure 9 This is a schematic diagram of the overall structural design of the acoustic wavefront conversion device according to an embodiment of the present invention;

[0047] Figure 10 This is a schematic diagram related to the 5000Hz frequency described in an embodiment of the present invention, wherein, Figure 10 (a) represents the total sound pressure field of the sound wave after passing through the simulated device. Figure 10 (b) shows the sound field energy distribution diagram after the sound wave passes through the simulated device;

[0048] Figure 11 Figure 1 shows the total sound pressure field and sound field energy distribution of 2000Hz, 3000Hz and 4000Hz sound waves passing through the simulation device according to the embodiments of the present invention. Figure 2 shows the total sound pressure field of 2000Hz sound waves passing through the simulation device, Figure 3 shows the sound field energy distribution of 2000Hz sound waves passing through the simulation device, Figure 4 shows the total sound pressure field of 3000Hz sound waves passing through the simulation device, Figure 5 shows the sound field energy distribution of 3000Hz sound waves passing through the simulation device, Figure 6 shows the total sound pressure field of 4000Hz sound waves passing through the simulation device, and Figure 7 shows the sound field energy distribution of 4000Hz sound waves passing through the simulation device.

[0049] Figure 12 The radiation patterns of the 2000Hz, 3000Hz, and 4000Hz sound waves passing through the simulation device are shown in the embodiments of the present invention.

[0050] Figure 13 Figure 1 shows the total sound pressure field and sound field energy distribution of 6000Hz, 7000Hz, and 8000Hz sound waves passing through the simulation device according to an embodiment of the present invention; wherein Figure (a) shows the total sound pressure field of 6000Hz sound waves passing through the simulation device, Figure (b) shows the sound field energy distribution of 6000Hz sound waves passing through the simulation device, Figure (c) shows the total sound pressure field of 7000Hz sound waves passing through the simulation device, Figure (d) shows the sound field energy distribution of 7000Hz sound waves passing through the simulation device, Figure (e) shows the total sound pressure field of 8000Hz sound waves passing through the simulation device, and Figure (f) shows the sound field energy distribution of 8000Hz sound waves passing through the simulation device.

[0051] Figure 14 This is the radiation pattern of the 6000Hz, 7000Hz, and 8000Hz sound waves passing through the simulation device, as described in the embodiments of the present invention. Detailed Implementation

[0052] The technical solution of the present invention will be described in detail below.

[0053] First, the present invention discloses an acoustic wavefront conversion device, which is composed of multiple discrete artificial microstructure unit matrices.

[0054] For this unit structure, the working parameters of the manually designed unit structure are first derived by reverse engineering based on the conversion function requirements. Then, the equivalent acoustic parameters of the discrete unit structure are extracted using the two-port network transmission matrix method. Finally, the arrangement position of each microstructure unit is determined based on the obtained equivalent acoustic parameters. After determining the position and equivalent parameters of each unit structure, the equivalent refractive index distribution of the sound wave exhibits a gradual change in space.

[0055] Each discretized microstructure unit corresponds to a discrete parameter of the acoustic wave frontal conversion device. Due to the different discrete parameters, the degree of refractive index change when the acoustic wave interacts with each structural unit also varies. By arranging each discrete unit in an orderly manner according to theoretical parameters, the refractive index of the acoustic wave changes regularly in space, thereby achieving the acoustic wave conversion effect. For example... Figure 11 As shown, when a 5000Hz cylindrical wave interacts with the device, a plane wave appears in the positive direction of the device. Therefore, within a very short range, the cylindrical wave emitted from the cylindrical wave source is directionally converted into a plane wave.

[0056] In specific implementation, the acoustic microstructure unit has directional characteristics, that is, the response of its characteristic parameters is different for mutually perpendicular directions. This characteristic can be used to purposefully control the propagation path of sound waves within the structure, such as modulating the outgoing wavefront into a regular plane wave.

[0057] The working principle of a wavefront converter is as follows: Figure 1 As shown. Let the radii of the inner and outer circles be a and b, respectively, and the side length of the outer square be 2c. Divide the square domain into four triangles. In a triangle with the cylindrical wave emission source as one vertex and the two adjacent vertices of the square as the other two vertices, x', y', and z' are the spatial coordinates in the transformation medium region, and x, y, and z are the coordinates in real space. The relationship between them is as follows:

[0058] = ,

[0059] = ,

[0060] Using the above equations, the Jacobian transformation matrix is ​​obtained as follows:

[0061]

[0062] Then, the constitutive parameter tensor of the medium in the transformation space, i.e., the equivalent acoustic parameters, is obtained through the Helmholtz equation:

[0063]

[0064]

[0065] in, B represents the density and elastic modulus of the medium in real space. , The converted medium density and elastic modulus are given by det(). The rank of the matrix. Here, the conversion medium region and the real space refer to the modulated sound wave. The conversion medium region refers to the device region of this invention, where the sound wave behavior is affected by the conversion medium. This medium has a designable equivalent density and modulus. The phase of the sound wave modulated by the conversion medium corresponds to the coordinate transformation position in the real space. Thus, by reverse designing the desired coordinate position, the wavefront phase arrangement of the sound wave in the real space can be obtained. "Arranging microstructure units at the pixel positions" aims to obtain the equivalent parameters that the conversion medium should possess.

[0066] For simplicity, when verifying the implementation effect, a sample of the device model with an inner circle and outer square in step (3) can be taken for verification. The sampled part is as follows: Figure 1 The rectangular dashed box in (a), and Figure 1 As shown in (b), the refractive index distribution of the selected portion calculated according to theoretical parameters is as follows: Figure 1As shown in (c). It should be noted that the difference between the sampled part and the overall theoretical model is that the theoretical model can convert the radiation from a point sound source placed in the sample into planar beam radiation in four directions, while only one beam is used for actual effect verification. That is, when the beam conversion effect in one direction is observed, the other three directions also have the same radiation effect. Based on this, the following implementation steps are carried out using the designed sample as an example.

[0067] Based on the acoustic parameter distribution characteristics of the waveform conversion, the theoretical medium with wavefront conversion function is first discretized. Since the theoretical medium is continuously distributed, while the actual device consists of a series of designed individual units, discretization is necessary. Each discretized unit is similar to a pixel and is called a discrete unit. The size of the discrete unit is consistent with the size of the acoustic metamaterial unit; that is, the theoretical refractive index of the discrete unit must be consistent with the refractive index of the unit structure at that location.

[0068] Select unit structures that meet the requirements based on the theoretical refractive index. Unit structures whose theoretical refractive index is consistent with or very close to the refractive index exhibited by the metamaterial unit structure are retained. In this unit structure, the d-value is dynamically adjustable; for different refractive indices, there is a corresponding parameter value d, such as... Figure 8 The diagram shows the numerical distribution of the refractive index of a square sampling area. Here, x represents the coordinates along the length of the sample, y represents the coordinates along the thickness, and z represents the refractive index value; a higher refractive index results in a higher height. Therefore, for each different d-structure parameter, there is a specific structural unit corresponding to it. Finally, the selected real unit structures that meet the theoretical requirements of discrete unit theory are arranged according to the theoretical distribution requirements. This is based on the fact that each position in the functional area has a corresponding theoretical refractive index requirement. To place the actual microstructure unit in the functional area to form the device, the microstructure unit must possess the refractive index required at that position. Thus, the discrete pixel positions are arranged with selected microstructure units.

[0069] To make the physical device easier to fabricate, the theoretical medium was discretized into 7 layers, each with 20 unit structures. These unit structures were arranged according to the extracted refractive index, thus obtaining a sample of the acoustic wavefront conversion device. Figure 9 As shown, the unit structure is composed of "T" and "U" shaped branch structures combined vertically, as follows: Figure 6 As shown, the acoustic metamaterial unit size a in the sample is 15 mm, the unit structure height b is 14 mm, the structural gap e is 2 mm, the structural width c is 6 mm, and the structural thickness is... The size is 1mm. Analysis showed that by changing the size d of the unit device, which is adjustable from 1mm to 11mm, the equivalent refractive index parameter of the unit structure can be changed. The figure shows... Figure 1 and 2 A discrete microstructural unit, relative to one of its pixels. Figure 1 The dimensions in the figure represent the spatial distribution during theoretical analysis, while Figure 6 For a specific structural unit, the relationship between the two is that of a whole and a discrete unit, in terms of size, that is, relative to... Figure 1 Given a total size, perform discrete partitioning, with each discrete unit being... Figure 6 The size of this unit, and its refractive index, can be adjusted by the d-parameter of its branched structure, such as... Figure 7 As shown in (a), its refractive index exhibits a gradually varying frequency characteristic, such as Figure 7 As shown in (b), this means that the structure has the advantage of wideband operation. Figure 7 This refers to the refractive index distribution obtained by adjusting the d-parameter of the branch structure. Since the acoustic refractive index is a complex value, its real part is represented by Real, which physically represents the ability to refract sound waves, and its imaginary part is represented by Imag, which represents the attenuation of sound waves. This is not based on experimental results or theoretical calculations.

[0070] After obtaining the samples, full-wave simulations were performed. The results showed that the acoustic wavefront conversion device exhibited the effect of directional conversion of cylindrical waves into plane waves within the operating frequency range of 2kHz to 8kHz. Figure 10 , 11 As shown in Figures 12 and 14.

[0071] To verify that the designed sample can modulate the cylindrical wavefront emitted from the sound source into a planar wavefront, achieving wavefront conversion, numerical simulation methods were applied to compare the total sound pressure field and sound field energy distribution of the sample with a realistic wavefront conversion structure with those of the theoretically equivalent medium. Figure 12 , 13 As shown in Figures 14 and 15.

[0072] To further verify the working characteristics of the acoustic wavefront conversion device, the operating bandwidth of the sample was also discussed. The simulated acoustic wave frequency was increased from 2000Hz to 8000Hz. The results showed that, except for 2000Hz which did not meet the expected target, the cylindrical wave emitted from the sound source could be modulated into a plane wave from 3000Hz to 8000Hz. Figure 12 , 14 As shown. Therefore, the operating frequency of the wavefront conversion device is 3000Hz to 8000Hz, which has the characteristic of wide frequency range.

[0073] The fabrication process of the device of this invention is as follows:

[0074] (1) First, the working device is modeled. The model is a microstructure unit layer with a circular inner contour and a square outer contour, such as Figure 2 As shown

[0075] (2) Based on the acoustic wave conversion function requirements, the material layer is assigned the above theoretical parameters. A cylindrical wave emission source is added at the center, and then numerical simulation is performed on the established model. Figure 3 , 4 As shown in Figure 5

[0076] (3) Design the unit structure of the conversion medium and extract the equivalent acoustic parameters of the designed unit structure. Based on the theoretical parameters of the acoustic wavefront converter, design the overall structure of the sample of the acoustic wavefront converter.

[0077] (3) Performance analysis of the designed acoustic wavefront conversion sample. Not only were the total sound pressure field and sound field energy distribution of the sample compared with the theoretical medium, but its broadband characteristics were also analyzed.

[0078] (4) Based on the wavefront transformation requirements, and after verifying the theoretical mechanism, a 7-layer, 20-column matrix structure was designed. The corresponding unit structure parameters in the sample were extracted. Figure 8 , 9 As shown.

[0079] (5) After verifying the high consistency with the ideal effect through CONSOL multiphysics software simulation, the sample was then printed as a physical object using a 3D printer.

[0080] (6) Finally, the actual sample was tested, and the actual parameters were compared with the theoretical parameters to further confirm that the sample can modulate the cylindrical wavefront emitted by the sound source into a plane wavefront, thus achieving the effect of wavefront conversion.

[0081] This invention theoretically provides analytical expressions for the equivalent acoustic parameters of an acoustically equivalent medium and designs a sound wave conversion device, demonstrating that this transformation concept also has novel controllable effects on the sound wave field. This is because acoustic microstructure unit metamaterials, when designed according to theory, can exhibit unique material parameter values, thus allowing for reverse design of the desired specific material, thereby achieving sound field control capabilities not found in ordinary materials. The sound wave conversion device scheme of this invention can be applied to corresponding designs in underwater detection, ultrasonic testing, noise control, etc., and has broad application prospects, with beneficial application value in fields such as people's livelihood and national defense.

[0082] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0083] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations to the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. An acoustic wavefront conversion device, characterized in that, The device comprises multiple microstructural units, which, after their arrangement is determined, form a multi-layered, multi-column matrix structure. Each microstructural unit internally includes a "T"-shaped branch structure and a "U"-shaped branch structure. The "T"-shaped branch structure is positioned above the "U"-shaped branch structure, and each "T"-shaped branch structure includes horizontal and vertical units that intersect perpendicularly. The "U"-shaped branch structure includes vertical structures on both sides and horizontal structures connected to the vertical structures. The vertical structures and vertical units have the same length, denoted as 'd', which is set according to the theoretical refractive index at different locations within the device. The method for determining the arrangement of the microstructural units includes the following steps: (1) Set up the structure of the simulated wavefront conversion device, and set a cylindrical wave emission source at the center of the simulated wavefront conversion device; (2) Calculate the equivalent acoustic parameters of the cylindrical wave for waveform conversion based on the relevant parameters of the simulated wavefront conversion device and after spatial coordinate transformation and its Jacobian matrix; (3) Discretize the simulated wavefront conversion device to obtain multiple positions, and determine the arrangement position of each microstructure unit according to the equivalent acoustic parameters; The structure of the simulated wavefront conversion device is as follows: the exterior is a square, and the interior of the square contains an inner circle and an outer circle. The radius of the inner circle is set to 'a', the radius of the outer circle is set to 'b', and the side length of the square is set to 2c. .

2. The acoustic wavefront conversion device according to claim 1, characterized in that, Step (2) specifically includes: in a triangle with the cylindrical wave emission source as one vertex and the two adjacent vertices of the square as the other two vertices, x' y' z' are the spatial coordinates in the transformation medium region, and x, y, z are the coordinates in real space, and the two have the following relationship: = , = , Using the above equations, the Jacobian transformation matrix is ​​obtained as follows: Then, the constitutive parameter tensor of the medium in the transformation space, i.e., the equivalent acoustic parameters, is obtained through the Helmholtz equation: in, B represents the density and elastic modulus of the medium in real space. , The converted medium density and elastic modulus are given by det(). The rank of a matrix.

3. The acoustic wavefront conversion device according to claim 2, characterized in that, Step (3) specifically includes: The simulated wavefront conversion device features an internal circular arc distribution and an external square distribution. The arrangement of its microstructure units is designed through the following steps: First, the conversion function of the acoustic wave is calculated according to the conversion function to obtain the theoretical parameter distribution of the equivalent density and elastic modulus of the cylindrical wave after passing through the conversion device; Second, the conversion device is discretized, and each pixel retains the theoretical parameter value at that location; Third, microstructure units are placed into the corresponding pixels, based on the principle that the refractive index of the microstructure unit at that pixel is consistent with the theoretical refractive index at that location; Fourth, after all discrete pixels have been filled with microstructure units, the array structure is fixed onto the substrate material.

4. The acoustic wavefront conversion device according to claim 3, characterized in that, The theoretical refractive index pass The refractive index of the microstructure unit is obtained by the specific structure of the designed microstructure unit.

5. The acoustic wavefront conversion device according to claim 1, characterized in that, The microstructure unit uses ABS or photosensitive resin as the base material.

6. The acoustic wavefront conversion device according to claim 1, characterized in that, The solid structure of the microstructure unit is fabricated using 3D printing technology.

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