Regulation and control method and device for laser ultrasonic system

Abstract

The invention relates to the technical field of ultrasound, in particular to a regulation and control method and device of a laser ultrasonic system, and the laser ultrasonic system comprises a laser and an ultrasonic holographic lens; the ultrasonic holographic lens can reconstruct holographic sound fields of one or more preset frequencies, and is suitable for pulse or continuous modulation of laser beams to obtain the holographic sound fields of the laser beams under one or more preset frequencies. The method specifically comprises the following steps: acquiring a pre-set laser beam, and performing optical focusing to generate a light spot; absorbing light energy of the light spots to generate ultrasonic waves, and performing sound constraint on the ultrasonic waves to form a laser ultrasonic field; a laser ultrasonic field is acoustically matched and coupled to the acoustical holographic layer, generating a holographic sound field in the medium. According to the invention, only by controlling the excitation laser, one or more focused ultrasonic sound fields with one or more preset frequencies can be realized in various propagation media in a time-sharing or simultaneous manner through the ultrasonic holographic lens, and the degree of freedom is better.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic technology, and in particular to a control method and device of a laser ultrasonic system. Background Art

[0002] Acoustic holography has become an important component of a wide range of acoustic applications, such as biomedical imaging, medical therapy, and acoustic tweezers. Holography is based on the spatial storage of the phase and amplitude profile of a desired wavefront so that when illuminated with a suitable coherent source, the wavefront is interferometrically reconstructed to reconstruct the target sound field. Modern computer-generated holograms skip the process of recording the hologram from the physical scene and instead compute the required phase profile before rendering it for reconstruction.

[0003] In the prior art, traditional phased-control systems need to be configured with array-type ultrasonic sensors. Therefore, existing phased-control systems have problems of great manufacturing difficulty and high cost. Traditional control methods based on this phased-control system limit the number of channels for laser ultrasonic field control, making it difficult to obtain holographic sound fields at multiple frequencies, and lacking the degree of freedom in controlling the phased-control system. Summary of the invention

[0004] 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 control method and device for a laser ultrasonic system.

[0005] The technical solution of the present invention is as follows: A control method for a laser ultrasonic system, wherein the laser ultrasonic system comprises: A laser for emitting a laser beam; An ultrasonic holographic lens, the ultrasonic holographic lens comprising a light focusing layer, an acoustic confinement layer, a light absorption layer, an acoustic matching layer and an acoustic holographic layer arranged in sequence along the laser light path, wherein the light absorption layer is used to absorb the light energy of the laser beam to generate ultrasonic waves; the acoustic holographic layer comprises a plurality of holographic units of different thicknesses, and the phase and amplitude of the ultrasonic waves are manipulated by adjusting the thickness of the holographic units to meet the requirements of reconstructing holographic sound fields of multiple preset frequencies; The control method is suitable for continuously modulating a laser beam to obtain a holographic sound field at multiple preset frequencies, and includes: S1, obtaining a continuously modulated laser beam of a preset frequency, and generating a light spot after optical focusing by the light focusing layer; S2, the light absorption layer absorbs the light energy of the light spot to generate at least one ultrasonic wave, and the ultrasonic wave is acoustically constrained by the acoustic confinement layer to form a laser ultrasonic field; S3, using an acoustic matching layer to acoustically match and couple the laser ultrasonic field to the acoustic holographic layer, so as to generate a holographic acoustic field of a preset frequency in a propagation medium; Repeat S1 to S3 to sequentially complete the continuous modulation of the laser beam to obtain the holographic sound field at the preset frequency.

[0006] A control method for a laser ultrasonic system, wherein the laser ultrasonic system comprises: A laser for emitting a laser beam; An ultrasonic holographic lens, the ultrasonic holographic lens comprising a light focusing layer, an acoustic confinement layer, a light absorption layer, an acoustic matching layer and an acoustic holographic layer arranged in sequence along the laser light path, wherein the light absorption layer is used to absorb the light energy of the laser beam to generate ultrasonic waves; the acoustic holographic layer comprises a plurality of holographic units of different thicknesses, and the phase and amplitude of the ultrasonic waves are manipulated by adjusting the thickness of the holographic units to meet the requirements of reconstructing a holographic sound field of a preset target frequency; The control method is applicable to a pulsed laser beam to obtain a holographic sound field at a target preset frequency, and includes: Acquire a pulse modulated laser beam, and generate a light spot after optically focusing through the light focusing layer; The light absorption layer absorbs the light energy of the light spot to generate at least one ultrasonic wave, and the ultrasonic wave is acoustically constrained by the acoustic confinement layer to form a laser ultrasonic field; The laser ultrasonic field is acoustically matched and coupled to the acoustic holographic layer by using an acoustic matching layer, so as to generate a holographic acoustic field of a target preset frequency in a propagation medium.

[0007] In a possible technical solution, further, when the light absorbing layer generates ultrasonic waves, If the number of ultrasonic waves is greater than one, the plurality of ultrasonic waves will be superimposed on each other to form an ultrasonic plane wave, the frequency of which is consistent with the preset frequency of the acoustic holographic layer; The ultrasonic plane wave is acoustically confined to form a laser ultrasonic field.

[0008] In a possible technical solution, further, the light focusing layer includes an optical focusing lens, wherein the optical focusing lens is one or more hemispherical lenses, which are used to focus the laser beam to generate at least one ultrasonic wave.

[0009] In a possible technical solution, further, the phase of the ultrasonic wave and the thickness of the holographic unit satisfy the following relationship: , in, represents the phase of the ultrasonic wave, Indicates the preset ultrasonic frequency, is the speed of sound in the propagation medium, represents the speed of sound of the holographic unit, Indicates the thickness of the holographic unit.

[0010] In a possible technical solution, further, the amplitude of the ultrasonic wave and the thickness of the holographic unit satisfy the following relationship: , in, represents the amplitude of ultrasonic wave, It represents the sound pressure of the ultrasonic spherical wave emitted by the acoustic matching layer after the acoustic characteristics are matched. represents the thickness of the holographic unit, represents the acoustic impedance of the acoustic matching layer, represents the impedance of the acoustic holographic layer, represents the acoustic impedance of the propagation medium, Represents the wave number of the acoustic holographic layer.

[0011] According to the control method of the laser ultrasonic system of the embodiment of the present invention, there is no need to configure an array ultrasonic sensor. Only by controlling the preset excitation laser, multiple focused ultrasonic sound fields of single or multiple preset frequencies can be realized in various propagation media in a time-sharing or simultaneous manner through the ultrasonic holographic lens. Compared with the existing control method with only one center frequency, the ultrasonic focusing focal position and power in the control method of the present invention can be adjusted, and have better freedom.

[0012] According to the control method of the laser ultrasonic system of the embodiment of the present invention, long-distance non-contact laser driving can be achieved by using a laser without the need for high-voltage excitation of cables and wired connections. Compared with the traditional ultrasonic field control method that relies on ultrasonic sensors, the durability, safety, convenience and applicability of use are greatly improved.

[0013] A control device for a laser ultrasonic system, wherein the device is used to execute the control method for the laser ultrasonic system as described above, comprising: A laser ultrasonic system, comprising a laser and an ultrasonic holographic lens, for obtaining a holographic sound field by transmitting a laser beam emitted by the laser through the ultrasonic holographic lens; The recognition module is used to recognize the holographic sound field and feedback the holographic sound field information, and is arranged on the recognition surface of the holographic sound field; The control module is connected to the recognition module and the laser respectively, and is used to control the laser to emit a new laser beam after acquiring the holographic sound field information, so as to reconstruct a new holographic sound field by the ultrasonic holographic lens.

[0014] In a possible technical solution, further, the ultrasonic holographic lens includes: The light focusing layer is used to obtain a previously preset laser beam and generate a light spot after optical focusing; An acoustic confinement layer for forward penetration of the laser beam; A light absorbing layer, used for absorbing the light energy of the light spot and generating at least one ultrasonic wave, the ultrasonic wave is acoustically constrained, and is reflected and superimposed on the acoustic constraining layer to form a laser ultrasonic field; An acoustic matching layer, used for performing feature matching processing on the laser ultrasonic field; The acoustic holographic layer is used to perform holographic processing on the laser ultrasonic field to generate a holographic acoustic field in a propagation medium.

[0015] A laser ultrasonic medical device comprises the control device of the above-mentioned laser ultrasonic system, wherein the laser ultrasonic medical device can be used for ultrasonic manipulation and driving, ultrasonic detection imaging, low-power ultrasonic stimulation and power ultrasonic treatment, etc.

[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 diagram of a control device for a laser ultrasound system according to Embodiment 1 of the present invention; Figure 2 is a schematic structural diagram of a frequency-mixing ultrasonic holographic lens according to Embodiment 1 of the present invention; Figure 3 is a schematic flow chart of a control method for a laser ultrasonic system according to Embodiment 1 of the present invention; Figure 4 is a schematic diagram of generating a focused sound field with a preset frequency of 200 kHz in the air according to Embodiment 1 of the present invention; Figure 5 is a schematic diagram of generating a focused sound field with a preset frequency of 500 kHz in the air according to Embodiment 1 of the present invention; Figure 6 is a schematic structural diagram of a single-frequency ultrasonic holographic lens according to Embodiment 2 of the present invention; Figure 7 It is a schematic diagram of generating a focused sound field with a preset frequency of 5 MHz in water according to Example 2 of the present invention.

[0019] Reference numerals: Laser Ultrasound System 100 Laser 1, ultrasonic holographic lens 2; Light focusing layer 11, acoustic confinement layer 12, light absorption layer 13, acoustic matching layer 14, mixed frequency acoustic holographic layer 15, single frequency acoustic holographic layer 16; Hologram unit 150. 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 See also Figure 1 and Figure 2 As shown, this embodiment provides a control device for a laser ultrasound system, wherein the control device includes: The laser ultrasound system 100 comprises a laser 1 and an ultrasonic holographic lens 2, wherein the laser 1 is used to emit a laser beam, and the ultrasonic holographic lens 2 comprises a light focusing layer 11, an acoustic confinement layer 12, a light absorption layer 13, an acoustic matching layer 14 and a frequency mixing acoustic holographic layer 15 which are sequentially arranged along the optical path of the laser beam, wherein the light absorption layer 13 is used to absorb the optical energy of the laser beam to generate ultrasonic waves; the frequency mixing acoustic holographic layer 15 comprises a plurality of holographic units 150 of different thicknesses, and the phase and amplitude of the ultrasonic waves are manipulated by adjusting the thickness of the holographic unit 150 to meet the requirements of reconstructing holographic sound fields of multiple preset frequencies; The recognition module 3 is used to recognize the holographic sound field and feedback the holographic sound field information, and is arranged on the recognition surface of the holographic sound field; The control module 4 is connected to the recognition module 3 and the laser 1 respectively, and is used to control the laser 1 to emit a new continuously modulated laser beam after acquiring the holographic sound field information, so as to be used for the ultrasonic holographic lens 2 to reconstruct a new holographic sound field.

[0027] The control method is suitable for continuously modulating a laser beam to obtain a holographic sound field at multiple preset frequencies, and includes: S1, obtaining a continuously modulated laser beam of a preset frequency, and generating a light spot after optical focusing by the light focusing layer 11; S2, the light absorption layer 13 absorbs the light energy of the light spot, generates at least one ultrasonic wave, and the ultrasonic wave is acoustically constrained by the acoustic confinement layer 12 to form a laser ultrasonic field; S3, using the acoustic matching layer 14 to acoustically match and couple the laser ultrasonic field to the mixing acoustic holographic layer 15, so as to generate a holographic acoustic field of a previously preset frequency in the propagation medium; Repeat S1 to S3 to sequentially complete the continuous modulation of the laser beam to obtain the holographic sound field at the preset frequency.

[0028] It should be noted that the light focusing layer 11 is used to obtain a continuously modulated laser beam of a preset frequency, and to generate a light spot after optical focusing; the light focusing layer 11 includes an optical focusing lens, wherein the optical focusing lens can be composed of a single-focus optical focusing lens or a multi-focus optical microlens array, which is used to focus the modulated laser beam to generate at least one ultrasonic wave.

[0029] The material of the acoustic confinement layer 12 is a glass rigid material, a thin film flexible material, a gel or a solution material with low optical absorption rate, and is used for forward penetration of the laser beam; The light absorption layer 13 is used to absorb the light energy of the light spot and generate at least one ultrasonic wave. The ultrasonic wave is acoustically confined and reflected and superimposed on the acoustic confinement layer to form a laser ultrasonic field. The light absorption layer 13 is made of a material with high optical absorption rate such as metal, carbon or graphite. In this embodiment, the high optical absorption rate is greater than 0.8 and the low optical absorption rate is less than 0.2.

[0030] The acoustic matching layer 14 is used to perform feature matching processing on the laser ultrasonic field. The material of the acoustic matching layer 14 has a relatively high thermal expansion coefficient. In this embodiment, the thermal expansion coefficient is 0.92×10 -3 K -1 .

[0031] The mixing acoustic holographic layer 15 includes a plurality of holographic units 150, which are used to perform holographic processing on the laser ultrasonic field to generate a holographic acoustic field in the propagation medium. The acoustic impedance of the mixing acoustic holographic layer 15 and the acoustic matching layer 14 are the same or similar.

[0032] Based on the control device of this embodiment, a control method of a laser ultrasound system is provided, which is suitable for continuously modulating a laser beam to obtain a holographic sound field at multiple preset frequencies, such as Figure 3 As shown, including: Step S100, obtaining a continuously modulated laser beam with a frequency of W1, and generating a light spot after optical focusing by the light focusing layer 11; Step S200, the light absorption layer 13 absorbs the light energy of the light spot to generate at least one ultrasonic wave, and the ultrasonic wave is acoustically constrained by the acoustic confinement layer 12 to form a laser ultrasonic field; Step S300, using the acoustic matching layer 14 to acoustically match and couple the laser ultrasonic field to the mixing acoustic holographic layer 15, so as to generate a holographic acoustic field with a frequency of W1 in the propagation medium; Step S400, obtaining a continuously modulated laser beam with a frequency of W2, repeating steps S100 to S300, and generating a holographic sound field with a frequency of W2 in a propagation medium.

[0033] It should be noted that absorbing the light energy of the light spot, generating at least one ultrasonic wave, acoustically confining the ultrasonic wave, and forming a laser ultrasonic field specifically includes: When the number of ultrasonic waves is one, the ultrasonic wave is an ultrasonic spherical wave; When the number of ultrasonic waves is greater than one, the plurality of ultrasonic waves are superimposed on each other to form an ultrasonic plane wave, the frequency of the ultrasonic plane wave is the preset frequency of the continuously modulated laser beam, and the preset frequency of the continuously modulated laser beam is consistent with the preset frequency of the acoustic holographic layer; The ultrasonic plane wave is acoustically confined to form a laser ultrasonic field.

[0034] It should be noted that the phase of the ultrasonic wave and the thickness of the holographic unit satisfy the following relationship: , in, represents the phase of the ultrasonic wave, Indicates the preset ultrasonic frequency, is the speed of sound in the propagation medium, represents the speed of sound of the holographic unit, Indicates the thickness of the holographic unit.

[0035] It should be noted that the amplitude of the ultrasonic wave and the thickness of the holographic unit satisfy the following relationship: , in, represents the amplitude of ultrasonic wave, It represents the sound pressure of the ultrasonic spherical wave emitted by the acoustic matching layer after the acoustic characteristics are matched. represents the thickness of the holographic unit, represents the acoustic impedance of the acoustic matching layer, represents the impedance of the acoustic holographic layer, represents the acoustic impedance of the propagation medium, Represents the wave number of the acoustic holographic layer.

[0036] Taking the preset frequencies of 200kH and 500kHz of the acoustic holographic layer as an example, when the mixed-frequency ultrasonic holographic lens is driven by continuously modulating the laser beam, a focused ultrasonic field with preset frequencies of 200kHz and 500kHz is generated. The focal projection distances controlled by the two preset frequencies are 25mm and 15mm respectively.

[0037] The frequency mixing ultrasonic holographic lens used in this embodiment ( Figure 2) is 30×60 mm in size. All holographic units 150 are evenly divided into two preset frequency areas on the left and right. The size of the holographic unit 150 is 0.5×0.5 mm. The material is photosensitive resin; the acoustic confinement layer material is 0.5 mm polydimethylsiloxane (PDMS); the optical absorption material is 0.3 mm carbon nanoparticle material; the acoustic matching layer material is 0.2 mm polydimethylsiloxane (PDMS). The light focusing layer is a hemispherical lens array of 300×600 with a diameter of 0.1 mm.

[0038] The modulation frequency is preset to 200 kHz, and a continuously modulated laser beam with a frequency of 200 kHz is obtained, and an array of focused light spots is generated through the hemispherical lens array of the light focusing layer to irradiate the optical absorption material; The light absorption layer absorbs the light energy of the focused light spot by the laser thermoelastic effect, generates an array of ultrasonic spherical waves, and coherently forms an ultrasonic plane wave with a frequency of 200kHz. After acoustically constraining the ultrasonic plane wave, an amplified laser ultrasonic field is formed; The amplified laser ultrasonic field is acoustically matched and coupled to the ultrasonic holographic lens, and the phase and amplitude of the ultrasonic plane wave are regulated by adjusting the thickness of each holographic unit 150 in the ultrasonic holographic lens. Finally, a focused acoustic field with a preset frequency of 200 kHz and a focal length of 25 mm is generated in the air. Figure 4 As shown; The modulation frequency is preset to 500kHz, and a continuously modulated laser beam with a frequency of 500kHz is obtained. The above operation is repeated to obtain a focused acoustic field with a preset frequency of 500kHz in the air, and a focal length of 15 mm. Figure 5 shown.

[0039] According to the control method of the laser ultrasonic system of the embodiment of the present invention, it is only necessary to control the preset frequency of the excitation laser to realize single or multiple focused ultrasonic sound fields of one or more preset frequencies in various propagation media in a time-sharing manner through the ultrasonic holographic lens. Compared with the existing control method with only one center frequency, the focusing focus position and power of the excitation laser in the control method of the present invention can be adjusted, and has better freedom.

[0040] According to the control method of the laser ultrasonic system in the embodiment of the present invention, long-distance non-contact laser driving can be realized without the need for high-voltage excitation of cables and wired connections. Compared with the traditional ultrasonic field control method that relies on ultrasonic sensors, the durability, safety, convenience and applicability of use are greatly improved.

[0041] Example 2 This embodiment is further modified on the basis of Embodiment 1, and provides a control device for a laser ultrasound system, wherein the control device includes: A laser ultrasonic system, comprising a laser and an ultrasonic holographic lens, wherein the laser is used to emit a laser beam, and the ultrasonic holographic lens comprises a light focusing layer 11, an acoustic confinement layer 12, a light absorption layer 13, an acoustic matching layer 14 and a single-frequency acoustic holographic layer 16 arranged in sequence along the optical path of the laser beam, wherein the light absorption layer 13 is used to absorb the optical energy of the laser beam to generate ultrasonic waves; the single-frequency acoustic holographic layer 16 comprises a plurality of holographic units 160 of different thicknesses, and the phase and amplitude of the ultrasonic wave are manipulated by adjusting the thickness of the holographic unit 160 to meet the requirements of reconstructing holographic sound fields of multiple preset frequencies; The control method is applicable to a pulsed laser beam to obtain a holographic sound field at a target preset frequency, and includes: Obtaining a pulse modulated laser beam, and generating a light spot after optical focusing by the light focusing layer 11; The light absorption layer 13 absorbs the light energy of the light spot, generates at least one ultrasonic wave, and acoustically constrains the ultrasonic wave through the acoustic confinement layer 12 to form a laser ultrasonic field; The laser ultrasonic field is acoustically matched and coupled to the single-frequency acoustic holographic layer 16 by using the acoustic matching layer 14, so as to generate a holographic acoustic field of a target preset frequency in the propagation medium.

[0042] It should be noted that when the light absorbing layer 13 generates ultrasonic waves, Since the ultrasonic field generated by the pulsed laser beam has infinite bandwidth, if the number of ultrasonic waves is greater than one, multiple ultrasonic waves will superimpose on each other to form an ultrasonic plane wave, and the preset frequency (i.e., center frequency) of the ultrasonic plane wave is consistent with the preset frequency of the acoustic holographic layer.

[0043] The ultrasonic plane wave is acoustically confined to form a laser ultrasonic field.

[0044] It should be noted that the light focusing layer 11 is used to obtain a pulse modulated laser beam of a preset frequency, and to generate a light spot after optical focusing; the light focusing layer 11 includes an optical focusing lens, wherein the optical focusing lens can be composed of a single-focus optical focusing lens or a multi-focus optical microlens array, which is used to focus the modulated laser beam to generate at least one ultrasonic wave.

[0045] It should be noted that absorbing the light energy of the light spot, generating at least one ultrasonic wave, acoustically confining the ultrasonic wave, and forming a laser ultrasonic field specifically includes: When the number of ultrasonic waves is one, the ultrasonic wave is an ultrasonic spherical wave; When the number of ultrasonic waves is greater than one, the multiple ultrasonic waves are superimposed on each other to form an ultrasonic plane wave, and the center frequency of the ultrasonic plane wave is consistent with the preset frequency of the acoustic holographic layer; The ultrasonic plane wave is acoustically confined to form a laser ultrasonic field.

[0046] The material of the acoustic confinement layer 12 is a glass rigid material, a thin film flexible material, a gel or a solution material with low optical absorption rate, and is used for forward penetration of the laser beam; The light absorption layer 13 is used to absorb the light energy of the light spot and generate at least one ultrasonic wave. The ultrasonic wave is acoustically confined and reflected and superimposed on the acoustic confinement layer to form a laser ultrasonic field. The light absorption layer 13 is made of a material with high optical absorption rate such as metal, carbon or graphite. In this embodiment, the high optical absorption rate is greater than 0.8 and the low optical absorption rate is less than 0.2.

[0047] The acoustic matching layer 14 is used to perform feature matching processing on the laser ultrasonic field. The material of the acoustic matching layer 14 has a relatively high thermal expansion coefficient. In this embodiment, the thermal expansion coefficient is 0.92×10 -3 K -1 .

[0048] The single-frequency acoustic holographic layer 16 includes a plurality of holographic units 160, which are used to perform holographic processing on the laser ultrasonic field to generate a holographic acoustic field in the propagation medium. The acoustic impedance of the single-frequency acoustic holographic layer 16 and the acoustic matching layer 14 are the same or similar.

[0049] The control device of this embodiment provides a control method for a laser ultrasound system, which is suitable for pulse modulating a laser beam to obtain a holographic sound field at a target preset frequency, including: Step S110, obtaining a pulse modulated laser beam, and generating a light spot after optical focusing by the light focusing layer 11; Step S210, the light absorption layer 13 absorbs the light energy of the light spot to generate at least one ultrasonic wave, and the ultrasonic wave is acoustically constrained by the acoustic confinement layer 12 to form a laser ultrasonic field; Step S310: using the acoustic matching layer 14 to acoustically match and couple the laser ultrasonic field to the single-frequency acoustic holographic layer 16, so as to generate a holographic acoustic field of a preset frequency in a propagation medium.

[0050] It should be noted that the phase of the ultrasonic wave and the thickness of the holographic unit satisfy the following relationship: , in, represents the phase of the ultrasonic wave, Indicates the preset ultrasonic frequency, is the speed of sound in the propagation medium, represents the speed of sound of the holographic unit, Indicates the thickness of the holographic unit.

[0051] It should be noted that the amplitude of the ultrasonic wave and the thickness of the holographic unit satisfy the following relationship: , in, represents the amplitude of ultrasonic wave, It represents the sound pressure of the ultrasonic spherical wave emitted by the acoustic matching layer after the acoustic characteristics are matched. represents the thickness of the holographic unit, represents the acoustic impedance of the acoustic matching layer, represents the impedance of the single-frequency acoustic holographic layer, represents the acoustic impedance of the propagation medium, Represents the wave number of a single-frequency acoustic holographic layer.

[0052] For example, the frequency of the single-frequency ultrasonic holographic lens is preset to 5 MHz, the focal length and spacing of the dual focal points are 9 mm and 5 mm respectively, and the single-frequency ultrasonic holographic lens is driven by a pulse modulated laser beam to simultaneously generate a dual-focal point focused ultrasonic field with a preset frequency of 5 MHz.

[0053] Taking the preset frequency of the acoustic holographic layer as 5 MHz as an example, the focal length is set to 9 mm, and the single-frequency ultrasonic holographic lens is driven by a pulse-modulated laser beam to simultaneously generate a dual-focus focused ultrasonic field with a preset frequency of 5 MHz.

[0054] The single-frequency ultrasonic holographic lens used in this embodiment ( Figure 6 ) is 10×10 mm in size, the size of the holographic unit is 0.5×0.5 mm, and the material is photosensitive resin; the acoustic confinement layer material is 0.3 mm transparent glass; the optical absorption material is 0.2 mm black metal film; the acoustic matching layer material is 0.2 mm polydimethylsiloxane (PDMS). The light focusing layer is a hemispherical lens array of 100×100 with a diameter of 0.1 mm.

[0055] A pulse modulated laser beam is obtained and passed through the hemispherical lens array of the light focusing layer to generate an array of focused light spots to irradiate the black metal film; The black metal film absorbs the light energy of the focused spot by the laser ablation effect, generates an array of broadband ultrasonic spherical waves, and coherently forms ultrasonic plane waves. After acoustically constraining the ultrasonic plane waves, an amplified laser ultrasonic field is formed. The amplified laser ultrasonic field is acoustically matched and coupled to the single-frequency ultrasonic holographic lens, and the phase and amplitude of the ultrasonic plane wave are regulated by adjusting the thickness of the holographic unit in the single-frequency ultrasonic holographic lens. Finally, a focused acoustic field with a preset frequency (i.e., center frequency) of 5 MHz is generated in water, with a focal length of 9 mm and a focal interval of 5 mm. Figure 7 shown.

[0056] According to the control method of the laser ultrasonic system of the embodiment of the present invention, it is only necessary to control the excitation pulse laser to simultaneously realize a single or multiple focused ultrasonic sound fields of a single preset frequency in various propagation media through a single-frequency ultrasonic holographic lens. Compared with the existing control method with only one center frequency, the ultrasonic focusing focal position and power in the control method of the present invention can be adjusted, and have better freedom.

[0057] According to the control method of the laser ultrasonic system in the embodiment of the present invention, long-distance non-contact laser driving can be realized without the need for high-voltage excitation of cables and wired connections. Compared with the traditional ultrasonic field control method that relies on ultrasonic sensors, the durability, safety, convenience and applicability of use are greatly improved.

[0058] Example 3 A laser ultrasonic medical device of this embodiment includes the control device of the above-mentioned laser ultrasonic system, wherein the laser ultrasonic medical device can be used for ultrasonic control and driving, ultrasonic detection imaging, low-power ultrasonic stimulation and power ultrasonic treatment, etc.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 method for controlling a laser ultrasonic system, characterized in that: The laser ultrasonic system comprises: A laser for emitting a laser beam; An ultrasonic holographic lens, the ultrasonic holographic lens comprising a light focusing layer, an acoustic confinement layer, a light absorption layer, an acoustic matching layer and an acoustic holographic layer arranged in sequence along the laser light path, wherein the light absorption layer is used to absorb the light energy of the laser beam to generate ultrasonic waves; the acoustic holographic layer comprises a plurality of holographic units of different thicknesses, and the phase and amplitude of the ultrasonic waves are manipulated by adjusting the thickness of the holographic units to meet the requirements of reconstructing holographic sound fields of multiple preset frequencies; The control method is suitable for continuously modulating a laser beam to obtain a holographic sound field at multiple preset frequencies, and includes: S1, obtaining a continuously modulated laser beam of a preset frequency, and generating a light spot after optical focusing by the light focusing layer; S2, the light absorption layer absorbs the light energy of the light spot to generate at least one ultrasonic wave, and the ultrasonic wave is acoustically constrained by the acoustic confinement layer to form a laser ultrasonic field; S3, using an acoustic matching layer to acoustically match and couple the laser ultrasonic field to the acoustic holographic layer, so as to generate a holographic acoustic field of a preset frequency in a propagation medium; Repeat S1 to S3 to sequentially complete the continuous modulation of the laser beam to obtain the holographic sound field at the preset frequency.

2. A control method for a laser ultrasonic system, characterized in that: The laser ultrasonic system comprises: A laser for emitting a laser beam; An ultrasonic holographic lens, the ultrasonic holographic lens comprising a light focusing layer, an acoustic confinement layer, a light absorption layer, an acoustic matching layer and an acoustic holographic layer arranged in sequence along the laser light path, wherein the light absorption layer is used to absorb the light energy of the laser beam to generate ultrasonic waves; the acoustic holographic layer comprises a plurality of holographic units of different thicknesses, and the phase and amplitude of the ultrasonic waves are manipulated by adjusting the thickness of the holographic units to meet the requirements of reconstructing a holographic sound field of a preset frequency of a target; The control method is applicable to a pulsed laser beam to obtain a holographic sound field at a target preset frequency, and includes: Acquire a pulsed laser beam, and generate a light spot after optically focusing through the light focusing layer; The light absorption layer absorbs the light energy of the light spot to generate at least one ultrasonic wave, and the ultrasonic wave is acoustically constrained by the acoustic confinement layer to form a laser ultrasonic field; The laser ultrasonic field is acoustically matched and coupled to the acoustic holographic layer by using an acoustic matching layer, so as to generate a holographic acoustic field of a target preset frequency in a propagation medium.

3. The control method of the laser ultrasonic system according to claim 1 or 2, characterized in that: When the light absorbing layer generates ultrasonic waves, If the number of ultrasonic waves is greater than one, the plurality of ultrasonic waves will be superimposed on each other to form an ultrasonic plane wave, the frequency of which is consistent with the preset frequency of the acoustic holographic layer; The ultrasonic plane wave is acoustically confined to form a laser ultrasonic field.

4. The control method of the laser ultrasonic system according to claim 1 or 2, characterized in that: The light focusing layer comprises an optical focusing lens, wherein the optical focusing lens is one or more hemispherical lenses, which are used to focus the laser beam to generate at least one ultrasonic wave.

5. The control method of the laser ultrasonic system according to claim 1 or 2, characterized in that: The phase of the ultrasonic wave and the thickness of the holographic unit satisfy the following relationship: ， in, represents the phase of the ultrasonic wave, Indicates the preset ultrasonic frequency, is the speed of sound in the propagation medium, represents the speed of sound of the holographic unit, Indicates the thickness of the holographic unit.

6. The control method of the laser ultrasonic system according to claim 1 or 2, characterized in that: The amplitude of the ultrasonic wave and the thickness of the holographic unit satisfy the following relationship: ， in, represents the amplitude of ultrasonic wave, It represents the sound pressure of the ultrasonic spherical wave emitted by the acoustic matching layer after the acoustic characteristics are matched. represents the thickness of the holographic unit, represents the acoustic impedance of the acoustic matching layer, represents the impedance of the acoustic holographic layer, represents the acoustic impedance of the propagation medium, Represents the wave number of the acoustic holographic layer.

7. A control device for a laser ultrasonic system, characterized in that: A method for controlling a laser ultrasonic system according to claim 1 or 2, comprising: A laser ultrasonic system, comprising a laser and an ultrasonic holographic lens, for obtaining a holographic sound field by transmitting a laser beam emitted by the laser through the ultrasonic holographic lens; The recognition module is used to recognize the holographic sound field and feedback the holographic sound field information, and is arranged on the recognition surface of the holographic sound field; The control module is connected to the recognition module and the laser respectively, and is used to control the laser to emit a new laser beam after acquiring the holographic sound field information, so as to reconstruct a new holographic sound field by the ultrasonic holographic lens.

8. The control device of the laser ultrasonic system according to claim 7, characterized in that: The ultrasonic holographic lens comprises: The light focusing layer is used to obtain a previously preset laser beam and generate a light spot after optical focusing; An acoustic confinement layer for forward penetration of the laser beam; A light absorbing layer, used for absorbing the light energy of the light spot and generating at least one ultrasonic wave, the ultrasonic wave is acoustically constrained, and is reflected and superimposed on the acoustic constraining layer to form a laser ultrasonic field; An acoustic matching layer, used for performing feature matching processing on the laser ultrasonic field; The acoustic holographic layer is used to perform holographic processing on the laser ultrasonic field to generate a holographic acoustic field in a propagation medium.

9. A laser ultrasonic medical device, comprising the control device of the laser ultrasonic system according to claim 7 or 8, characterized in that: The laser ultrasound medical device can be used for ultrasound manipulation and driving, ultrasound detection imaging, low-power ultrasound stimulation and power ultrasound treatment.

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