Laser ultrasonic holographic lens and design method

Abstract

The invention relates to the technical field of ultrasound, in particular to a laser ultrasonic holographic lens and a design method, and the lens comprises a light focusing layer, a sound restraint layer, a light absorption layer, a sound matching layer and a sound holographic layer. The acoustical holographic layer comprises at least one sound field area, the phase and amplitude of ultrasonic waves in the laser ultrasonic field in the sound field area are controlled by adjusting the thickness of different holographic units in each sound field area, and a holographic sound field with at least one preset frequency is obtained. The design method comprises the steps that a target sound field is reconstructed through an iterative angular spectrum method, then the sound field is used for setting a virtual sound source in a virtual source time reversal method, and finally the sound pressure and the spatial-temporal distribution of the target sound field can be directly reconstructed only through external laser driving. An adjustable holographic sound field with one or more preset frequencies is generated in a gas, liquid or solid medium. Compared with a traditional single-frequency single-medium ultrasonic sensor and a traditional focusing acoustic lens, the application range is wider.

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 industrial detection and medical diagnosis and treatment. Acoustic holography has become an important part 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 with a suitable coherent source, this wavefront is interfered 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 the application of acoustic holography technology, the traditional phased-control system based on array ultrasonic transducers has limited the number of channels in the phased-control system due to the difficulty and cost of manufacturing the system, which limits the complexity or degree of freedom that can be obtained in front of the ultrasound. The large number of cables connected to each array element of the array transducer in a large ultrasonic array system greatly reduces the convenience of use. For ultrasonic sensors that require high-voltage drive, there is still a 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 solution of the present invention is as follows: A laser ultrasonic holographic lens, comprising: A light focusing layer, used for focusing the light spot generated by the laser beam; An acoustic confinement layer, disposed on the backlight side of the optical focusing layer, for performing acoustic confinement processing on the laser beam; 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; An acoustic matching layer, disposed on the backlight side of the light absorbing layer, for performing feature matching processing on the laser ultrasonic field; The acoustic holographic layer is arranged on the backlight side of the acoustic matching layer, and the acoustic holographic layer includes a plurality of holographic units for performing holographic processing on the laser ultrasonic field. 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.

[0007] A method for designing a laser ultrasonic holographic lens, comprising: 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 an angular spectrum in a target ultrasonic field; 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; 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.

[0008] In a possible technical solution, further, S12 specifically includes: Assume a is the pressure field of a single frequency pressure in a uniform medium: , in are the amplitude and the relative phase change in three-dimensional space respectively; Given The value at 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; 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.

[0009] In a possible technical solution, further, S15 includes: The complex amplitude of the ultrasonic field plane is calculated based on the output pressure distribution. ,include: , , 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.

[0010] In a possible technical solution, further, S17 includes: Computational 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: , , 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.

[0011] A method for designing a laser ultrasonic holographic lens, which is suitable for reconstructing a target sound field, 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 the ultrasonic time domain signal of each holographic unit of the acoustic holographic layer, and reversing the ultrasonic time domain signal on the time axis to obtain a time reversal signal; S23, performing Fourier transform on the time-reversed signal, extracting the phase value corresponding to the preset frequency as a 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.

[0012] In a possible technical solution, further, the calculation process of S24 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.

[0013] 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 time-sharing or simultaneously. Compared with the traditional single-frequency single-medium ultrasonic sensor and focused acoustic lens, the present invention has a wider range of applications.

[0014] 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.

[0015] A computer storage medium, wherein instructions are stored in the computer storage medium, and when the instructions are executed on a computer, the computer executes the above-mentioned design method of the laser ultrasonic holographic lens.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. 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 creative work.

[0018] Figure 1 is a schematic structural diagram of a laser ultrasonic holographic lens according to an embodiment of the present invention; Figure 2 An example of phase distribution of a single-frequency single-focus ultrasonic holographic lens driven by a continuously modulated laser provided in this application; Figure 3 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; Figure 4 An example of phase distribution of a laser-driven frequency-mixing dual-focus ultrasound holographic lens provided in this application; Figure 5 A simulation example of a focused sound field reconstructed by a laser-driven frequency-mixing dual-focus ultrasonic holographic lens provided in this application.

[0019] Reference numerals: The light focusing layer 100 , the acoustic confinement layer 200 , the light absorbing layer 300 , the acoustic matching layer 400 , the acoustic holographic layer 500 , and the holographic unit 510 . DETAILED DESCRIPTION

[0020] 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.

[0021] 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 considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0023] The terms "first", "second", "third", etc. in the specification and claims of the present application and the drawings are used to distinguish different objects rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a series of steps or units are included, or optionally, steps or units not listed are included, or optionally, other steps or units inherent to these processes, methods, products or devices are included.

[0024] Only the part relevant to the present application is shown in the accompanying drawings, but not all of the content. Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processing or methods depicted as flow charts. Although the flow chart describes each operation (or step) as a sequential process, many of the operations therein can be implemented in parallel, concurrently or simultaneously. In addition, the order of each operation can be rearranged. When its operation is completed, the process can be terminated, but it can also have additional steps not included in the accompanying drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0025] The terms "component", "module", "system", "unit", etc. used in this specification are used to represent 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 through local and / or remote processes, for example, 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. For example, the Internet interacts with other systems via signals).

[0026] Example 1 Example 1, see Figure 1 As shown, this embodiment provides a laser ultrasonic holographic lens, which includes: The light focusing layer 100 is used to focus the light spot generated by the laser beam; The acoustic confinement layer 200 is disposed on the backlight side of the light focusing layer 100 and is used to perform acoustic confinement processing on the laser beam; The light absorbing layer 300 is disposed 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; The acoustic matching layer 400 is disposed on the backlight side of the light absorbing layer 300 and is used to perform feature matching processing on the laser ultrasonic field; 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.

[0027] It should be noted that the acoustic holographic layer 500 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 510 in each sound field region to obtain at least one holographic sound field of a preset frequency.

[0028] This embodiment provides a design method for a laser ultrasonic holographic lens, which includes: 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 an angular spectrum in a target ultrasonic field; S12, calculating the acoustic pressure wave of the target ultrasonic field according to the angular spectrum, and obtaining the amplitude and phase mapping of the target ultrasonic field based on the pressure wave calculation, which includes: Assume a is the pressure field of a single frequency pressure in a uniform medium: , in are the amplitude and the relative phase change in three-dimensional space respectively; Given The value at 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 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; 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.

[0029] 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, wherein the complex amplitude of the ultrasonic field plane is calculated according to the output pressure distribution ,include: , , 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; 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.

[0030] 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): , , 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.

[0031] Taking the detection of liver tumors as an example, it is assumed that the liver tumor is an ellipsoid with a major axis diameter of 12 mm and a minor axis diameter of 4 mm, and is located 50 mm below the abdomen.

[0032] 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.

[0033] 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.

[0034] The light focusing layer is composed of 1000×1000 hemispherical microlenses with a diameter of 0.1 mm printed with 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.

[0035] Transparent glass with a large difference in acoustic impedance from the light absorption 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 absorption layer. The actual output sound pressure distribution of the acoustic matching layer is obtained through acoustic field testing and numerical inversion. .

[0036] 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 : , , 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.

[0037] Assume that the phase output of the ultrasonic wave generated by the light absorption layer through the acoustic matching layer is flat, and set the initial phase of the acoustic holographic surface to zero. Divide the acoustic field containing the tumor into 20 sections, set the sound pressure of the area containing the tumor in each section to 10 MPa, the phase to 0, and the remaining areas to 0, and then repeat S14 and S15 until the amplitude and phase changes of the output sound field meet the mapping of the amplitude and phase of the target sound field.

[0038] Based on the acoustic matching layer, the thickness information of the holographic unit is calculated, and the acoustic holographic layer is printed with photosensitive resin. Finally, the light focusing layer is glued to one side of the acoustic confinement layer with 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 ablating the tumor is ultimately achieved.

[0039] Example 2 This embodiment provides a design method of a laser ultrasonic holographic lens, which is suitable for reconstructing a target sound field and includes 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 the ultrasonic time domain signal of each holographic unit of the acoustic holographic layer, and reversing the ultrasonic time domain signal on the time axis to obtain a time reversal signal; S23, performing Fourier transform on the time-reversed signal, extracting the phase value corresponding to the preset frequency as a holographic unit Phase value corresponding to thickness update ; S24, according to the phase value Calculate the thickness of each holographic unit , the 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; 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.

[0040] The laser ultrasonic holographic lens according to the embodiment of the present invention can be applied to various transmission media such as gas, liquid, solid, etc. After receiving the excitation laser, it can realize multiple focused ultrasonic sound fields of at least one preset frequency in time-sharing or simultaneously. Compared with the traditional single-frequency single-medium ultrasonic sensor and focused acoustic lens, the present invention has a wider range of applications.

[0041] The following is an explanation based on actual cases: 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 holographic layer is 30 mm×60 mm, and the size of the holographic unit is 0.5 mm×0.5 mm.

[0042] 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 adjusts its ultrasonic frequency to 400 kHz, and the holographic unit in the right area adjusts its ultrasonic frequency to 150 kHz.

[0043] First, the sound field simulation model was established through the k-wave toolbox in the MATLAB computing software, and a 30×60 square millimeter acoustic holographic surface was set up to receive the ultrasonic waves propagated outward from the virtual sound source, and virtual sound sources were set at 10 mm and 20 mm away from the acoustic holographic surface. The process of ultrasonic waves propagating from the virtual sound source to the ultrasonic holographic lens was simulated at the two virtual sound sources, and the ultrasonic time domain signal received by each holographic unit of the ultrasonic holographic lens was flipped on the time axis; then the time flipped signal was Fourier transformed to extract the phase value corresponding to the operating frequency of each holographic unit, and the thickness of each pixel was calculated according to the following formula: , 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.

[0044] The light focusing layer is composed of 300×600 hemispherical lenses with a diameter of 0.1 mm, with an overall size of 30 mm×60 mm, and the focusing distance of the hemispherical lenses is 1 mm.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] A continuously modulated laser beam with a modulation frequency of 150 kHz is used to irradiate the right area of ​​the light focusing layer. The generated ultrasound is regulated by the ultrasonic holographic lens to produce a 150 kHz focused ultrasound field. When continuously modulated lasers with modulation frequencies of 400 kHz and 150 KHz are used to irradiate the left and right areas of the light focusing layer at the same time, the ultrasonic holographic lens regulates and produces dual-focus ultrasound fields with preset frequencies of 400 kHz and 150 kHz respectively.

[0049] 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, and 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.

[0050] Example 3 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.

[0051] Example 4 A computer storage medium, wherein instructions are stored in the computer storage medium, and when the instructions are executed on a computer, the computer executes the above-mentioned design method of the laser ultrasonic holographic lens.

[0052] In the description of the present invention, it is to 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”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, 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 operated in a specific orientation, and therefore should not be understood as a limitation to the invention.

[0053] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0054] Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all 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 is not necessarily the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It can be explicitly and implicitly understood 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 ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0055] Although the 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 present invention, and that the scope of the present 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), 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 absorption layer (300) is arranged 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); An acoustic matching layer (400) is arranged 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 arranged on the backlight side of the acoustic matching layer (400), and the acoustic holographic layer (500) comprises a plurality of holographic units (510) for performing holographic processing on the laser ultrasonic field.

2. The laser ultrasonic holographic lens according to claim 1, characterized in that: The acoustic holographic layer (500) comprises 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 (510) in each sound field region to obtain at least one holographic sound field of a preset frequency.

3. A method for designing a laser ultrasonic holographic lens, characterized in that: include: 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 an angular spectrum in a target ultrasonic field; 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; 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.

4. The design method of the laser ultrasonic holographic lens according to claim 3 is 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 the relative phase change in three-dimensional space respectively; Given The value at 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 wave number 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.

5. The design method of the laser ultrasonic holographic lens according to claim 3, characterized in that: S15 includes: The complex amplitude of the ultrasonic field plane is calculated based on the output pressure distribution. ,include: ， ， 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.

6. The design method of the laser ultrasonic holographic lens according to claim 3, characterized in that: S17 includes: Computational 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: ， ， 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.

7. A method for designing a laser ultrasonic holographic lens, characterized in that: The steps include: 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 the ultrasonic time domain signal of each holographic unit of the acoustic holographic layer, and reversing the ultrasonic time domain signal on the time axis to obtain a time reversal signal; S23, performing Fourier transform on the time-reversed signal, extracting the phase value corresponding to the preset frequency as a 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.

8. The design method of the laser ultrasonic holographic lens according to claim 7, 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.

9. 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 as claimed in any one of claims 3 to 6 when executing the computer program.

10. 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 as described in any one of claims 3 to 6.

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