Laser ultrasonic holographic lens and design method

Abstract

The present invention relates to the field of ultrasonic technology, and in particular to a laser ultrasonic holographic lens and a design method thereof, wherein the lens comprises a light focusing layer, an acoustic confinement layer, a light absorption layer, an acoustic matching layer, and an acoustic holographic layer. The acoustic holographic layer comprises at least one acoustic field region, and the phase and amplitude of the ultrasonic wave in the laser ultrasonic field within the acoustic field region are controlled by adjusting the thickness of different holographic units in each acoustic field region, thereby obtaining at least one holographic acoustic field of a preset frequency. The design method comprises reconstructing the target acoustic field through an iterative angular spectrum method, and then using the acoustic field to set a virtual sound source in a virtual source time inversion method. Ultimately, the sound pressure magnitude and spatiotemporal distribution of the target acoustic field can be directly reconstructed by simply applying an external laser drive, thereby generating one or more controllable holographic acoustic fields of a preset frequency in a gas, liquid, or solid medium. Compared with traditional single-frequency, single-medium ultrasonic sensors and focusing acoustic lenses, the present invention has a wider range of applications.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic technology, and in particular to a laser ultrasonic holographic lens and a design method thereof. Background Art

[0002] Ultrasound generated by ultrasonic transducers has been widely used in fields such as industrial inspection and medical diagnosis and treatment. Acoustic holography has become an important component of a wide range of acoustic applications, such as biomedical imaging, medical treatment, and acoustic tweezers.

[0003] The basis of holography is the spatial storage of the phase and amplitude profile of a desired wavefront, so that when illuminated by a suitably coherent source, this wavefront is interferometrically used to reconstruct the target sound field. Modern computer-generated holograms skip the process of recording the hologram from a physical scene and instead compute the desired phase profile prior to rendering and reconstruction.

[0004] In acoustic holography applications, conventional phased-control systems based on arrayed ultrasonic transducers have limited channel counts due to manufacturing difficulties and costs. This, in turn, limits the complexity and degrees of freedom that can be achieved in the ultrasonic front. Large ultrasonic array systems, with their numerous cables connecting each element of the arrayed transducer, significantly reduce ease of use. For ultrasonic transducers requiring high-voltage drive, there is still the risk of dielectric breakdown. Summary of the Invention

[0005] The present invention aims to at least improve one of the technical problems existing in the prior art. To this end, the present invention proposes a laser ultrasonic holographic lens and a design method.

[0006] The technical solutions of the present invention are as follows:

[0007] A laser ultrasonic holographic lens, comprising:

[0008] A light focusing layer, used to focus the light spot generated by the laser beam;

[0009] an acoustic confinement layer, disposed on the backlight side of the light focusing layer, for performing acoustic confinement processing on the laser beam;

[0010] a light absorbing layer, disposed on the backlight side of the acoustic confinement layer, for absorbing the laser beam and converting the laser beam into a laser ultrasonic field together with the acoustic confinement layer;

[0011] an acoustic matching layer, disposed on the backlight side of the light absorbing layer, for performing feature matching processing on the laser ultrasonic field;

[0012] An acoustic holographic layer is arranged on the backlight side of the acoustic matching layer. The acoustic holographic layer includes a plurality of holographic units and is used for performing holographic processing on the laser ultrasonic field.

[0013] In a possible technical solution, further, the acoustic holographic layer includes at least one sound field region, and the phase and amplitude of the ultrasonic wave in the laser ultrasonic field in the sound field region are controlled by adjusting the thickness of different holographic units in each sound field region to obtain at least one holographic sound field of a preset frequency.

[0014] A method for designing a laser ultrasonic holographic lens, comprising:

[0015] Design light focusing layer, acoustic confinement layer, light absorption layer, and acoustic matching layer to convert laser beam into ultrasonic field output;

[0016] Designing an acoustic holographic layer includes the following steps:

[0017] S11, receiving the angular spectrum in the target ultrasonic field;

[0018] S12, calculating an acoustic pressure wave of a target ultrasonic field according to the angular spectrum, and obtaining an amplitude and phase mapping of the target ultrasonic field based on the pressure wave calculation;

[0019] S13, designing an acoustic holographic surface, and setting the initial phase of the acoustic holographic surface to zero;

[0020] S14, receiving the initial output sound field and outputting it to the ultrasonic field plane, obtaining the output pressure distribution of the ultrasonic field plane ;

[0021] S15, calculating the amplitude and phase change of the output sound field according to the output pressure distribution;

[0022] S16, judging whether the amplitude and phase changes of the output sound field conform to the mapping of the amplitude and phase of the target sound field, if so, jumping to S17, if not, repeating S14 to S15,

[0023] S17, determining the thickness of the holographic unit of the acoustic holographic layer according to the phase change of the output sound field, and obtaining the acoustic holographic layer.

[0024] In a possible technical solution, further, S12 specifically includes:

[0025] Assume a is the pressure field of a single frequency pressure in a uniform medium:

[0026] ,

[0027] in are the amplitude and relative phase changes in three-dimensional space respectively;

[0028] Given The value of a certain z point in the plane xy defines the angular spectrum of any z plane for The Fourier transform of x and y is:

[0029] ,

[0030] 、 is the component in wavenumber space;

[0031] Assume that z=0 is the acoustic holographic surface, then the angular spectrum of the acoustic holographic surface is P , through acoustic holographic surface angle spectrum Compute the angular spectrum of any z-plane :

[0032] ,

[0033] ,

[0034] in is the transfer function when backpropagating from the z plane to z=0, is the wave number of the propagation medium and λ is the wavelength.

[0035] In a possible technical solution, further, S15 includes:

[0036] The complex amplitude of the ultrasonic field plane is calculated based on the output pressure distribution ,include:

[0037] ,

[0038] ,

[0039] in Z t 、Z h 、Z m are the acoustic impedances of the medium where the acoustic matching layer, acoustic holographic layer and ultrasonic field plane are located, is the complex transmission coefficient, k h is the acoustic impedance of the hologram material, and T(x,y) represents the thickness of the hologram unit.

[0040] In a possible technical solution, further, S17 includes:

[0041] Computed Acoustic Holography The thickness of the holographic unit , assuming that the initial thickness of the acoustic holographic layer is T 0, the phase change determines the acoustic holographic layer Thickness of holographic unit at:

[0042] ,

[0043] ,

[0044] in is the thickness adjustment of the hologram pixel, is the relative phase change, k h and k m are the wave numbers of the acoustic holographic layer material and the medium, respectively.

[0045] A method for designing a laser ultrasonic holographic lens, suitable for reconstructing a target sound field, comprises the following steps:

[0046] S21, constructing an initial ultrasound simulation model, and setting a virtual sound source in the ultrasound simulation model according to the pressure distribution of the target sound field, wherein the initial ultrasound simulation model includes a light focusing layer, an acoustic confinement layer, a light absorption layer, an acoustic matching layer, and an initial acoustic holographic layer;

[0047] S22, inputting a preset frequency into the simulation software, simulating and recording the process of ultrasonic waves propagating from the virtual sound source to the acoustic holographic surface, receiving ultrasonic time domain signals from each holographic unit of the acoustic holographic layer, and reversing the ultrasonic time domain signals on the time axis to obtain time-reversed signals;

[0048] S23, performing Fourier transform on the time-reversed signal, extracting the phase value corresponding to the preset frequency as the holographic unit Phase value corresponding to thickness update ;

[0049] S24, according to the phase value Calculate the thickness of each holographic unit ;

[0050] S25 , adjusting the thickness of each holographic unit based on the initial acoustic holographic layer to obtain an updated acoustic holographic layer to meet the requirement of a preset frequency.

[0051] In a possible technical solution, further, the calculation process of S24 is as follows:

[0052] ,

[0053] in Holographic unit The corresponding phase value, f is the ultrasonic frequency, is the speed of sound in the propagation medium, is the sound velocity of the acoustic matching layer.

[0054] The laser ultrasonic holographic lens according to the embodiment of the present invention can be applied to various transmission media such as gas, liquid and solid. After receiving the excitation laser, it can realize multiple focused ultrasonic sound fields of at least one preset frequency in a time-sharing or simultaneous manner. Compared with traditional single-frequency single-medium ultrasonic sensors and focused acoustic lenses, the present invention has a wider range of applications.

[0055] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the above-mentioned design method of the laser ultrasonic holographic lens when executing the computer program.

[0056] A computer storage medium, wherein the computer storage medium stores instructions, and when the instructions are executed on a computer, the computer executes the above-mentioned design method of the laser ultrasonic holographic lens.

[0057] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. 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.

[0059] Figure 1 is a schematic structural diagram of a laser ultrasonic holographic lens according to an embodiment of the present invention;

[0060] Figure 2 This application provides an example of a phase distribution of a single-frequency, single-focus ultrasonic holographic lens driven by a continuously modulated laser;

[0061] Figure 3 This is a simulation example of a focused sound field reconstructed by a single-frequency, single-focus ultrasonic holographic lens driven by a continuously modulated laser provided in this application;

[0062] Figure 4 An example of phase distribution of a laser-driven frequency-mixing dual-focus ultrasound holographic lens provided in this application;

[0063] Figure 5 This application provides a simulation example of a focused sound field reconstructed by a laser-driven frequency-mixing dual-focus ultrasonic holographic lens.

[0064] Reference numerals:

[0065] Light focusing layer 100 , acoustic confinement layer 200 , light absorption layer 300 , acoustic matching layer 400 , acoustic holographic layer 500 , and holographic unit 510 . DETAILED DESCRIPTION

[0066] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0067] It should be noted that when an element is referred to as being “fixed to” another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intermediate element.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0069] In the specification, claims, and accompanying drawings of this application, the terms "first," "second," "third," and the like are used to distinguish different objects and are not used to describe a particular order. Furthermore, the terms "including," "comprising," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a list of steps or elements may be included, or alternatively, steps or elements not listed may be included, or other steps or elements may be included that are inherent to the process, method, product, or apparatus.

[0070] Only portions relevant to the present application are shown in the accompanying drawings, not all of them. Before discussing the exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flow charts. Although the flow charts describe the various operations (or steps) as sequential processes, many of the operations can be performed in parallel, concurrently, or simultaneously. In addition, the order of the various operations can be rearranged. The process can be terminated when its operations are completed, but can also have additional steps not included in the accompanying drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0071] As used in this specification, the terms "component," "module," "system," "unit," and the like are used to refer to computer-related entities, hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a unit can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or distributed between two or more computers. In addition, these units can be executed from various computer-readable media having various data structures stored thereon. Units can communicate, for example, via local and / or remote processes based on signals having one or more data packets (e.g., data from a second unit interacting with another unit in a local system, a distributed system, and / or a network, such as the Internet, which interacts with other systems via signals).

[0072] Example 1

[0073] Example 1, see Figure 1 As shown, this embodiment provides a laser ultrasonic holographic lens, which includes:

[0074] The light focusing layer 100 is used to focus the light spot generated by the laser beam;

[0075] an acoustic confinement layer 200 , disposed on the backlight side of the light focusing layer 100 , for acoustic confinement of the laser beam;

[0076] The light absorbing layer 300 is provided on the backlight side of the acoustic confinement layer 200 and is used to absorb the laser beam and convert the laser beam into a laser ultrasonic field together with the acoustic confinement layer 200;

[0077] The acoustic matching layer 400 is provided on the backlight side of the light absorbing layer 300 and is used to perform feature matching processing on the laser ultrasonic field;

[0078] The acoustic holographic layer 500 is disposed on the backlight side of the acoustic matching layer 400 . The acoustic holographic layer 500 includes a plurality of holographic units 510 for performing holographic processing on the laser ultrasonic field.

[0079] It should be noted that the acoustic holographic layer 500 includes at least one sound field region. By adjusting the thickness of different holographic units 510 in each sound field region to control the phase and amplitude of the ultrasonic wave in the laser ultrasonic field in the sound field region, a holographic sound field of at least one preset frequency is obtained.

[0080] This embodiment provides a method for designing a laser ultrasonic holographic lens, which includes:

[0081] Design light focusing layer, acoustic confinement layer, light absorption layer, and acoustic matching layer to convert laser beam into ultrasonic field output;

[0082] Designing an acoustic holographic layer includes the following steps:

[0083] S11, receiving the angular spectrum in the target ultrasonic field;

[0084] S12, calculating the acoustic pressure wave of the target ultrasonic field according to the angular spectrum, and obtaining an amplitude and phase mapping of the target ultrasonic field based on the pressure wave calculation, which includes:

[0085] Assume a is the pressure field of a single frequency pressure in a uniform medium:

[0086] ,

[0087] in are the amplitude and relative phase changes in three-dimensional space respectively;

[0088] Given The value of a certain z point in the plane xy defines the angular spectrum of any z plane for The Fourier transform of x and y is:

[0089] ,

[0090] 、 is the component in wave number space, that is, the component of wave vector k, where the wave vector , 、 are the components in three directions in wave number space;

[0091] Assume that z=0 is the acoustic holographic surface, then the angular spectrum of the acoustic holographic surface is P , through acoustic holographic surface angle spectrum Compute the angular spectrum of any z-plane :

[0092] ,

[0093] ,

[0094] in is the transfer function when backpropagating from the z plane to z=0, is the wave number of the propagation medium and λ is the wavelength.

[0095] S13, designing an acoustic holographic surface, and setting the initial phase of the acoustic holographic surface to zero;

[0096] S14, receiving the initial output sound field and outputting it to the ultrasonic field plane, obtaining the output pressure distribution of the ultrasonic field plane ;

[0097] S15, calculating the amplitude and phase change of the output sound field according to the output pressure distribution, wherein the complex amplitude of the ultrasonic field plane is calculated according to the output pressure distribution ,include:

[0098] ,

[0099] ,

[0100] in Z t 、Z h 、Z m are the acoustic impedances of the medium where the acoustic matching layer, acoustic holographic layer and ultrasonic field plane are located, is the complex transmission coefficient, k h is the acoustic impedance of the hologram material, T(x,y) represents the thickness of the hologram unit;

[0101] S16, judging whether the amplitude and phase changes of the output sound field conform to the mapping of the amplitude and phase of the target sound field, if so, jumping to S17, if not, repeating S14 to S15,

[0102] S17, determining the thickness of the holographic unit of the acoustic holographic layer according to the phase change of the output sound field, and obtaining the acoustic holographic layer.

[0103] It should be noted that the thickness of the holographic unit at the acoustic holographic layer (x, y) is calculated , assuming that the initial thickness of the acoustic holographic layer is T 0, the phase change determines the thickness of the holographic unit at the acoustic holographic layer (x, y):

[0104] ,

[0105] ,

[0106] in is the thickness adjustment of the hologram pixel, is the relative phase change, k h and k m are the wave numbers of the acoustic holographic layer material and the medium, respectively.

[0107] Taking the detection of liver tumors as an example, it is assumed that the liver tumor is an ellipsoid with a long axis diameter of 12 mm and a short axis diameter of 4 mm, and is located 50 mm below the abdomen.

[0108] First, the liver tumor is imaged using CT or MRI (Magnetic Resonance Imaging). Next, the shape, size, and depth of the tumor are determined based on the CT or MRI images.

[0109] According to the lateral precision of the 3D printer of 50 microns, the size of each holographic unit of the ultrasonic holographic lens is set to 0.5 microns × 0.5 microns, and the overall size of the ultrasonic holographic lens is determined to be 100 mm × 100 mm.

[0110] The light focusing layer consists of 1000×1000 hemispherical microlenses with a diameter of 0.1 mm printed on transparent photosensitive resin or transparent nylon. The overall size of the microlens array is 100 mm×100 mm and the focusing distance is 0.5 mm.

[0111] Transparent glass with a large difference in acoustic impedance from the light absorbing layer is selected as the acoustic constraint layer with a thickness of 0.5 mm. A 0.3 mm black metal film is used as the light absorbing layer. The actual output sound pressure distribution of the acoustic matching layer is obtained through acoustic field testing and numerical inversion. .

[0112] The acoustic holographic surface is calculated using the iterative angular spectrum method according to the sound field distribution. The angular spectrum of any z plane in the sound field is: , 、 is the component in wavenumber space; is the acoustic pressure field; are amplitude and phase functions respectively. If z=0 is the acoustic holographic surface, the angular spectrum of the acoustic holographic surface is P , through acoustic holographic surface angle spectrum The angular spectrum of any z-plane can be calculated :

[0113] ,

[0114] ,

[0115] in is the transfer function when backpropagating from the z plane to z=0, is the wave number of the propagation medium, λ is the wavelength, , c is the speed of sound, f is the preset frequency. In this embodiment, the preset frequency f is set to 500 kHz.

[0116] Assume that the ultrasonic wave generated by the light absorption layer has a flat phase output after passing through the acoustic matching layer, and set the initial phase of the acoustic holographic surface to zero. Divide the acoustic field containing the tumor into 20 slices. In each slice, the acoustic pressure in the area containing the tumor is set to 10 MPa and the phase is set to 0. The remaining areas are set to 0. Then, repeat S14 and S15 until the amplitude and phase changes of the output acoustic field match the amplitude and phase mapping of the target acoustic field.

[0117] Based on the acoustic matching layer, the thickness information of the holographic unit is calculated and the acoustic holographic layer is printed using photosensitive resin. Finally, the light focusing layer is glued to the side of the acoustic confinement layer using transparent glue. Using a high-energy 500 kHz continuously modulated laser beam to irradiate the light absorption layer, a high-power focused ultrasound field can be generated in the tumor area through the laser ablation effect, such as Figure 3 As shown, the goal of ablation of the tumor is ultimately achieved.

[0118] Example 2

[0119] This embodiment provides a method for designing a laser ultrasonic holographic lens, which is suitable for reconstructing a target sound field and includes the following steps:

[0120] S21, constructing an initial ultrasound simulation model, and setting a virtual sound source in the ultrasound simulation model according to the pressure distribution of the target sound field, wherein the initial ultrasound simulation model includes a light focusing layer, an acoustic confinement layer, a light absorption layer, an acoustic matching layer, and an initial acoustic holographic layer;

[0121] S22, inputting a preset frequency into the simulation software, simulating and recording the process of ultrasonic waves propagating from the virtual sound source to the acoustic holographic surface, receiving ultrasonic time domain signals from each holographic unit of the acoustic holographic layer, and reversing the ultrasonic time domain signals on the time axis to obtain time-reversed signals;

[0122] S23, performing Fourier transform on the time-reversed signal, extracting the phase value corresponding to the preset frequency as the holographic unit Phase value corresponding to thickness update ;

[0123] S24, according to the phase value Calculate the thickness of each holographic unit , the calculation process is as follows:

[0124] ,

[0125] in Holographic unit The corresponding phase value, f is the ultrasonic frequency, is the speed of sound in the propagation medium, is the sound velocity of the acoustic matching layer;

[0126] S25 , adjusting the thickness of each holographic unit based on the initial acoustic holographic layer to obtain an updated acoustic holographic layer to meet the requirement of a preset frequency.

[0127] The laser ultrasonic holographic lens according to the embodiment of the present invention can be applied to various transmission media such as gas, liquid, and solid. After receiving the excitation laser, it can realize multiple focused ultrasonic sound fields of at least one preset frequency in a time-sharing or simultaneous manner. Compared with traditional single-frequency and single-medium ultrasonic sensors and focused acoustic lenses, the present invention has a wider range of applications.

[0128] The following is an explanation based on actual cases:

[0129] In this embodiment, the focal lengths of the two focal points of the preset target sound field are 10 mm and 20 mm respectively, and the projection distance interval is 30 mm; the size of the acoustic hologram layer is 30 mm×60 mm, and the size of the holographic unit is 0.5 mm×0.5 mm.

[0130] The acoustic holographic layer is evenly divided into two areas, each area is 30 mm × 30 mm in size, wherein the holographic unit in the left area controls its ultrasonic frequency to 400 kHz, and the holographic unit in the right area controls its ultrasonic frequency to 150 kHz.

[0131] First, an acoustic field simulation model was established using the k-wave toolbox in MATLAB. A 30×60 mm² acoustic holographic surface was set up to receive ultrasonic waves propagating outward from a virtual sound source. Virtual sound sources were placed at 10 mm and 20 mm from the acoustic holographic surface. The process of ultrasonic waves propagating from the virtual sound source to the ultrasonic holographic lens was simulated at each virtual sound source. The ultrasonic time-domain signal received by each holographic unit of the ultrasonic holographic lens was flipped on the time axis. The time-flipped signal was then Fourier transformed to extract the phase value corresponding to the operating frequency of each holographic unit. The thickness of each pixel was calculated using the following formula:

[0132] ,

[0133] in Holographic unit The corresponding phase value, f is the ultrasonic frequency, is the speed of sound in the propagation medium, is the sound velocity of the acoustic matching layer.

[0134] The light focusing layer consists of 300×600 hemispherical lenses with a diameter of 0.1 mm, with an overall size of 30 mm×60 mm. The focusing distance of the hemispherical lenses is 1 mm.

[0135] A 1 mm thick acoustic constraint layer and a 0.5 mm thick acoustic matching layer were printed using photosensitive resin using a light-curing 3D printer, and a 0.2 mm thick black metal film was bonded between the acoustic constraint layer and the acoustic matching layer using transparent glue as a light absorption layer.

[0136] The acoustic holographic layer is made by using an injection molding process with a gas foam polymer that matches the acoustic impedance of air, and is bonded to the other side of the acoustic matching layer.

[0137] A continuously modulated laser beam with a modulation frequency of 400 kHz is used to irradiate the left area of ​​the light focusing layer to generate a uniform array of focused beams, which are then irradiated on the light absorption layer to generate ultrasonic waves, which are radiated and amplified by the acoustic confinement layer. After regulation, a 400 kHz focused ultrasonic field is finally generated.

[0138] A continuously modulated laser beam with a modulation frequency of 150 kHz was used to illuminate the right area of ​​the optical focusing layer. The generated ultrasound waves were then manipulated by the ultrasonic holographic lens to produce a 150 kHz focused ultrasound field. When continuously modulated laser beams with modulation frequencies of 400 kHz and 150 kHz were used simultaneously to illuminate the left and right areas of the optical focusing layer, the ultrasonic holographic lens manipulated the generated dual-focus ultrasound fields with preset frequencies of 400 kHz and 150 kHz, respectively.

[0139] It should be noted that the ultrasonic holographic lens of this embodiment can also use short pulse laser to irradiate the left and right areas of the light focusing layer simultaneously or in a time-sharing manner. The ultrasonic holographic lens can also simultaneously or in a time-sharing manner control and generate a dual-focus ultrasonic field with preset frequencies of 400 kHz and 150 kHz, such as Figure 5 shown.

[0140] Example 3

[0141] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the above-mentioned design method of the laser ultrasonic holographic lens when executing the computer program.

[0142] Example 4

[0143] A computer storage medium, wherein the computer storage medium stores instructions, and when the instructions are executed on a computer, the computer executes the above-mentioned design method of the laser ultrasonic holographic lens.

[0144] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as a limitation to the invention.

[0145] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "example," "specific example," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0146] Obviously, the described embodiments are only some of the embodiments of the present application, rather than all of the embodiments. Mentioning "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present embodiment application. The appearance of this phrase in various positions in the specification does not necessarily mean that they are all the same embodiments, nor are they independent or alternative embodiments that are mutually exclusive with other embodiments. It can be understood explicitly and implicitly by those skilled in the art that the embodiments described herein can be combined with other embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0147] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A laser ultrasonic holographic lens, characterized in that: include: A light focusing layer (100), the light focusing layer (100) being a microlens array, used for focusing a light spot generated by a laser beam; an acoustic confinement layer (200), arranged on the backlight side of the light focusing layer (100), and used for performing acoustic confinement processing on the laser beam; a light absorbing layer (300), arranged on the backlight side of the acoustic confinement layer (200), for absorbing the laser beam and converting the laser beam into a laser ultrasonic field together with the acoustic confinement layer (200); An acoustic matching layer (400) is provided on the backlight side of the light absorption layer (300) and is used to perform feature matching processing on the laser ultrasonic field; An acoustic holographic layer (500) is provided on the backlight side of the acoustic matching layer (400), the acoustic holographic layer (500) comprising a plurality of holographic units (510) for performing holographic processing on the laser ultrasonic field, wherein the acoustic holographic layer (500) comprises at least one sound field region, and the phase and amplitude of ultrasonic waves in the laser ultrasonic field in the sound field region are controlled by adjusting the thickness of different holographic units (510) in each sound field region, thereby obtaining at least one holographic sound field of a preset frequency.

2. A method for designing a laser ultrasonic holographic lens, characterized in that: For designing the laser ultrasonic holographic lens as claimed in claim 1, the design method comprises: Design light focusing layer, acoustic confinement layer, light absorption layer, and acoustic matching layer to convert laser beam into ultrasonic field output; Designing an acoustic holographic layer includes the following steps: S11, receiving the angular spectrum in the target ultrasonic field; S12, calculating an acoustic pressure wave of a target ultrasonic field according to the angular spectrum, and obtaining an amplitude and phase mapping of the target ultrasonic field based on the acoustic pressure wave calculation; S13, designing an acoustic holographic surface, and setting the initial phase of the acoustic holographic surface to zero; S14, receiving the initial output sound field and outputting it to the ultrasonic field plane, obtaining the output pressure distribution of the ultrasonic field plane ; S15, calculating the amplitude and phase change of the output sound field according to the output pressure distribution; S16, judging whether the amplitude and phase changes of the output sound field conform to the mapping of the amplitude and phase of the target sound field, if so, jumping to S17, if not, repeating S14 to S15, S17, determining the thickness of the holographic unit of the acoustic holographic layer according to the phase change of the output sound field, and obtaining the acoustic holographic layer.

3. The design method of the laser ultrasonic holographic lens according to claim 2, characterized in that: S12 specifically includes: Assume a is the pressure field of a single frequency pressure in a uniform medium: ， in are the amplitude and relative phase changes in three-dimensional space respectively; Given The value of a certain z point in the plane xy defines the angular spectrum of any z plane for The Fourier transform of x and y is: ， 、 is the component in wavenumber space k; Assume that z=0 is the acoustic holographic surface, then the angular spectrum of the acoustic holographic surface is P , through acoustic holographic surface angle spectrum Compute the angular spectrum of any z-plane : ， ， in is the transfer function when backpropagating from the z plane to z=0, is the wave number of the propagation medium and λ is the wavelength.

4. The design method of the laser ultrasonic holographic lens according to claim 2, characterized in that: S17 includes: Computed Acoustic Holography The thickness of the holographic unit , assuming that the initial thickness of the acoustic holographic layer is T 0, the acoustic holographic layer is determined by the phase change Thickness of holographic unit at: ， ， in is the thickness adjustment of the hologram pixel, is the relative phase change, k h and k m are the wave numbers of the acoustic holographic layer material and the medium, respectively.

5. A method for designing a laser ultrasonic holographic lens, characterized in that: For designing the laser ultrasonic holographic lens as claimed in claim 1, the design method comprises the following steps: S21, constructing an initial ultrasound simulation model, and setting a virtual sound source in the ultrasound simulation model according to the pressure distribution of the target sound field, wherein the initial ultrasound simulation model includes a light focusing layer, an acoustic confinement layer, a light absorption layer, an acoustic matching layer, and an initial acoustic holographic layer; S22, inputting a preset frequency into the simulation software, simulating and recording the process of ultrasonic waves propagating from the virtual sound source to the acoustic holographic surface, receiving ultrasonic time domain signals from each holographic unit of the acoustic holographic layer, and reversing the ultrasonic time domain signals on the time axis to obtain time-reversed signals; S23, performing Fourier transform on the time-reversed signal, extracting the phase value corresponding to the preset frequency as the holographic unit Phase value corresponding to thickness update ; S24, according to the phase value Calculate the thickness of each holographic unit ; S25 , adjusting the thickness of each holographic unit based on the initial acoustic holographic layer to obtain an updated acoustic holographic layer to meet the requirement of a preset frequency.

6. The design method of the laser ultrasonic holographic lens according to claim 5, characterized in that: The S24 calculation process is as follows: ， in Holographic unit The corresponding phase value, f is the ultrasonic frequency, is the speed of sound in the propagation medium, is the sound velocity of the acoustic matching layer.

7. A computer device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the method for designing a laser ultrasonic holographic lens according to any one of claims 2 to 4 when executing the computer program.

8. A computer storage medium, characterized in that The computer storage medium stores instructions, and when the instructions are executed on a computer, the computer executes the method for designing a laser ultrasonic holographic lens according to any one of claims 2 to 4.

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