Single-frequency laser ultrasonic focusing device and design method thereof

Abstract

The invention provides a single-frequency laser ultrasonic focusing device, and belongs to the field of laser ultrasound. Comprising a laser, a beam expander, a collimating mirror, a reflector and a single-frequency ultrasonic holographic lens. Wherein the laser is used for outputting a laser beam; the beam expander is used for adjusting the diameter of the laser beam; the collimating lens is arranged on the backlight side of the beam expanding lens, and the collimating lens enables the laser beam to be linearly propagated; the reflecting mirror is arranged on the backlight side of the collimating mirror and is used for changing the propagation path of the laser beam; the single-frequency ultrasonic holographic lens is arranged on the backlight side of the reflecting mirror, the single-frequency ultrasonic holographic lens comprises a plurality of holographic units with different thicknesses, and the single-frequency ultrasonic holographic lens is used for absorbing laser beams and generating an adjustable focusing ultrasonic field with the same lens frequency as the single-frequency ultrasonic holographic lens on the backlight side of the single-frequency ultrasonic holographic lens; the adjustable focusing ultrasonic field with adjustable focus number, sound pressure and focal length is generated through long-distance non-contact laser driving.

Description

Technical Field

[0001] The present application relates to the field of laser ultrasonic technology. Specifically, it relates to a single-frequency laser ultrasonic focusing device and a design method for a single-frequency laser ultrasonic focusing device. Background Art

[0002] Acoustic holography technology has been widely applied in fields such as biomedical imaging and medical treatment. The basis of holography lies in the spatial storage of the phase and amplitude profiles of the desired wavefront, so that when irradiated with a suitable coherent source, the target sound field can be reconstructed through interference. Modern computer-generated holograms bypass the traditional process of recording holograms from physical scenes and instead calculate the required phase profiles before rendering for reconstruction.

[0003] Currently, traditional phased systems based on array ultrasonic sensors face some challenges; due to the complexity of manufacturing and cost limitations of phased systems, the number of channels in traditional phased systems is limited, thus restricting the complexity or degrees of freedom that can be obtained in ultrasonic wavefronts; for ultrasonic sensors that require high-voltage drive, there is still a risk of dielectric breakdown; therefore, there is an urgent need for a single-frequency laser ultrasonic focusing device, which is more convenient and safe to use compared with traditional ultrasonic sensors and can generate the required ultrasonic focused sound field at a long distance. Summary of the Invention

[0004] The present application aims to solve at least one of the technical problems existing in the prior art or related technologies.

[0005] To this end, in the first aspect of the present application, a single-frequency laser ultrasonic focusing device is proposed.

[0006] In the second aspect of the present application, a design method for a single-frequency laser ultrasonic focusing device is proposed.

[0007] In the third aspect of the present application, an ultrasonic device is proposed.

[0008] In view of this, according to the first aspect of the present application, a single-frequency laser ultrasonic focusing device is provided, and the device includes: A laser for outputting a laser beam; A beam expander for adjusting the diameter of the laser beam; A collimator disposed on the backlight side of the beam expander, and the collimator is used to adjust the direction of the laser beam so that the laser beam propagates linearly; A reflector disposed on the backlight side of the collimator for changing the propagation path of the laser beam; A single-frequency ultrasonic holographic lens is disposed on the reflection side of the mirror. The single-frequency ultrasonic holographic lens includes a plurality of holographic units with different thicknesses. The single-frequency ultrasonic holographic lens is used to absorb the laser beam and generate an adjustable focused ultrasonic field consistent with the frequency of the single-frequency ultrasonic holographic lens on the backlight side of the single-frequency ultrasonic holographic lens.

[0009] In a possible technical solution, further, the single-frequency ultrasonic holographic lens includes: An optical focusing layer is disposed on the reflection side of the mirror and is used for condensing the laser beam reflected by the mirror. An acoustic confinement layer is disposed on the backlight side of the optical focusing layer. An optical absorption layer is disposed on the backlight side of the acoustic confinement layer and is used for absorbing the laser beam and jointly converting the laser beam into a laser ultrasonic field through the acoustic confinement layer. An acoustic matching layer is disposed on the backlight side of the optical absorption layer and is used for performing characteristic matching processing on the laser ultrasonic field. A single-frequency acoustic holographic layer includes a plurality of holographic units with different thicknesses. The single-frequency acoustic holographic layer is disposed on the backlight side of the acoustic matching layer and is used for performing holographic processing on the laser ultrasonic field.

[0010] In a possible technical solution, further, the optical focusing layer is a hemispherical lens or a plurality of hemispherical lenses arranged in an array. The hemispherical lens condenses the laser beam to generate a focused light spot. The acoustic confinement layer is a first light-transmitting nylon layer, and the focused light spot passes through the first light-transmitting nylon layer and enters the optical absorption layer. The optical absorption layer is a black metal film. After the black metal film absorbs the focused light spot, ultrasonic spherical waves are emitted simultaneously on the incident light side and the backlight side of the black metal film. The ultrasonic spherical waves on the incident light side are reflected and constrained by the first light-transmitting nylon layer and then superposed with the ultrasonic spherical waves on the backlight side to form a laser ultrasonic field. The acoustic matching layer is a second light-transmitting nylon layer, and the second light-transmitting nylon layer performs acoustic characteristic matching processing on the laser ultrasonic field. The single-frequency acoustic holographic layer is composed of a plurality of holographic units with different thicknesses connected together. The holographic units perform holographic processing on the laser ultrasonic field to obtain the adjustable focused ultrasonic field.

[0011] In a possible technical solution, further, the phase and amplitude of the ultrasonic waves in the adjustable focused ultrasonic field are controlled by adjusting the thickness of the holographic units.

[0012] In a possible technical solution, further, the thickness of the holographic unit and the phase of the ultrasonic wave satisfy the following relationship: , wherein, represents the phase of the ultrasonic wave, represents the preset ultrasonic frequency, represents the sound velocity of the propagation medium, represents the sound velocity of the holographic unit, represents the thickness of the holographic unit.

[0013] In a possible technical solution, further, the thickness of the holographic unit and the amplitude of the ultrasonic wave satisfy the following relationship: , wherein, represents the amplitude of the ultrasonic wave, represents the sound pressure of the ultrasonic spherical wave after acoustic characteristic matching emitted by the acoustic matching layer, 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 the single-frequency acoustic holographic layer.

[0014] In a possible technical solution, further, the number of foci of the single-frequency ultrasonic holographic lens is one or more, and the number of foci of the adjustable focusing ultrasonic field generated on the backlight side of the single-frequency ultrasonic holographic lens corresponds to one or more.

[0015] In a possible technical solution, further, the laser is any one of a continuous modulation laser and a pulsed laser.

[0016] According to the second aspect of the present application, a design method of a single-frequency laser ultrasonic focusing device is provided, and the method includes: Arranging the positions of the laser, the beam expander, the collimator and the reflector so that the laser beam output by the laser sequentially passes through the beam expander, the collimator and the reflector; Using transparent nylon for 3D printing to generate 90×90 hemispherical lenses with a diameter of 0.1 mm, and arranging the hemispherical lens array to obtain an optical focusing layer; Using transparent nylon for 3D printing to generate an acoustic confinement layer with a thickness of 1 mm and an acoustic matching layer with a thickness of 0.5 mm; Using a black metal film with a thickness of 0.2 mm as the light absorption layer, and pasting the acoustic confinement layer and the acoustic matching layer on both sides of the light absorption layer respectively; Pasting the optical focusing layer on the side of the acoustic confinement layer away from the light absorption layer; According to a preset focal length, a plurality of holographic units made of a polymer with acoustic impedance matched to the acoustic propagation medium are fabricated by 3D printing technology, with different thicknesses. The single-frequency acoustic holographic layer is formed by closely connecting the holographic units, and the single-frequency acoustic holographic layer is adhered to the side of the acoustic matching layer away from the light absorption layer to obtain a single-frequency ultrasonic holographic lens. The single-frequency ultrasonic holographic lens is arranged on the reflection side of the mirror, so that the laser beam emitted from the mirror passes through the light focusing layer and enters the single-frequency ultrasonic holographic lens, and an adjustable focusing ultrasonic field with the same frequency as the single-frequency ultrasonic holographic lens is generated from the single-frequency acoustic holographic layer.

[0017] According to the third aspect of the present application, an ultrasonic device is provided, including a single-frequency laser ultrasonic focusing device provided by any of the above designs. The ultrasonic device can be used for ultrasonic manipulation and driving, ultrasonic detection and imaging, low-power ultrasonic stimulation, and power ultrasonic treatment.

[0018] For a single-frequency laser ultrasonic focusing device provided according to the first aspect of the present application, first, a laser beam modulated by pulse or continuous is output by a laser; this laser beam has a preset intensity, providing an energy basis for generating an ultrasonic field subsequently; after passing through a beam expander, the diameter of the laser beam is adjusted to a suitable size; the beam expander enlarges or reduces the diameter of the beam by changing the divergence angle of the laser beam to ensure that subsequent optical elements can receive a uniform and appropriately sized laser beam; then, the laser beam enters a collimator; the main function of the collimator is to adjust the direction of the laser beam to keep it propagating in a straight line; this helps to ensure that the laser beam can be accurately received and processed by subsequent mirrors and the single-frequency ultrasonic holographic lens; after passing through the collimator, the laser beam is reflected by a mirror, thus changing its propagation path; the setting of the mirror enables the laser beam to enter the single-frequency ultrasonic holographic lens along a predetermined path; finally, the laser beam enters the single-frequency ultrasonic holographic lens; the single-frequency ultrasonic holographic lens includes a plurality of holographic units with different thicknesses. The single-frequency ultrasonic holographic lens absorbs the energy of the laser beam according to the thermoelastic or thermoablation effect. Since the number of focal points of the single-frequency ultrasonic holographic lens is one or more, the number of focal points of the adjustable focusing ultrasonic field generated on the backlight side of the single-frequency ultrasonic holographic lens is one or more. The adjustable focusing ultrasonic field is consistent with the frequency of the single-frequency ultrasonic holographic lens, and the phase and amplitude of the adjustable focusing ultrasonic field are controlled by controlling the thickness of the holographic units; the thickness of the holographic units in the single-frequency ultrasonic holographic lens is designed according to requirements, so that it can generate an adjustable focusing ultrasonic field that meets the required number of focal points, sound pressure, and focal length. The number of focal points, sound pressure, and focal length of the adjustable focusing ultrasonic field are adjusted by adjusting the thickness of the holographic units, thereby realizing the adjustability of the adjustable focusing ultrasonic field.

[0019] For a single-frequency laser ultrasonic focusing device provided according to the first aspect of the present application, its beneficial effects are as follows: Through the synergistic effect of the laser and the single-frequency ultrasonic holographic lens, the device can efficiently convert the energy of the laser beam into the energy of the ultrasonic field, thereby achieving precise ultrasonic focusing on the target area; by adjusting the thickness of the holographic unit, the adjustment of the number of foci, sound pressure, and focal length of the adjustable focusing ultrasonic field can be realized, thereby achieving the adjustability of the adjustable focusing ultrasonic field; through the design of multiple holographic units with different thicknesses, the number of foci of the single-frequency ultrasonic holographic lens can be one or more, resulting in the number of foci of the generated adjustable focusing ultrasonic field can also be one or more, increasing the flexibility of the device in practical applications such as ultrasonic manipulation and driving; due to the linear propagation characteristics of the laser beam and the precise reflection effect of the mirror, the device can achieve high-precision positioning of the target area; this helps to ensure that the ultrasonic field can accurately act on the target area, improving the treatment effect or detection accuracy; the single-frequency ultrasonic holographic lens can be rapidly, low-cost, and mass-produced by 3D printing without the molds required for the preparation of traditional ultrasonic sensors; the single-frequency laser ultrasonic focusing device can achieve long-distance non-contact laser driving without high-voltage excitation and wired connection of cables, greatly improving the durability, safety, convenience, and applicable fields compared with traditional ultrasonic sensors.

[0020] The additional aspects and advantages of the present application will become apparent in the following description section or be learned through the practice of the present application. Description of the Drawings

[0021] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 Shows a schematic structural diagram of a single-frequency laser ultrasonic focusing device according to an embodiment of the present application; Figure 2 Shows a schematic structural diagram of the single-frequency holographic lens of a single-frequency laser ultrasonic focusing device according to an embodiment of the present application; Figure 3 Shows a schematic structural diagram of an adjustable focusing ultrasonic field with two foci generated by a single-frequency laser ultrasonic focusing device according to an embodiment of the present application.

[0022] Wherein, Figures 1 to 3 The corresponding relationship between the reference numerals and the component names in the drawings is: 1. Laser; 2. Beam expander; 3. Collimator; 4. Mirror; 5. Single-frequency ultrasonic holographic lens; 51. Optical focusing layer; 52. Acoustic confinement layer; 53. Optical absorption layer; 54. Acoustic matching layer; 55. Single-frequency acoustic holographic layer; 551. Holographic unit. Detailed Embodiments

[0023] In order to more clearly understand the above-mentioned objects, features, and advantages of the present application, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0024] In the following description, many specific details are set forth in order to fully understand the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0025] The following refers to Figures 1 to 3 Describe a single-frequency laser ultrasonic focusing device and its design method provided according to some embodiments of the present application.

[0026] Embodiment 1 A single-frequency laser ultrasonic focusing device includes a laser 1, a beam expander 2, a collimator 3, a reflector 4, and a single-frequency ultrasonic holographic lens 5. Among them, the laser 1 is used to output a laser beam; the beam expander 2 is used to adjust the diameter of the laser beam; the collimator 3 is arranged on the backlight side of the beam expander 2, and the collimator 3 is used to adjust the direction of the laser beam so that the laser beam propagates linearly; the reflector 4 is arranged on the backlight side of the collimator 3 and is used to change the propagation path of the laser beam; the single-frequency ultrasonic holographic lens 5 is arranged on the reflection side of the reflector. The single-frequency ultrasonic holographic lens 5 includes a plurality of holographic units 551 with different thicknesses. The single-frequency ultrasonic holographic lens 51 is used to absorb the laser beam and generate an adjustable focusing ultrasonic field with the same frequency as the single-frequency ultrasonic holographic lens 5 on the backlight side of the single-frequency ultrasonic holographic lens 5.

[0027] It should be understood that, first, the laser 1 outputs a laser beam, which has a preset specific intensity and provides an energy basis for generating an ultrasonic field subsequently; after passing through the beam expander 2, the diameter of the laser beam is adjusted to a suitable size; the beam expander 2 enlarges or shrinks the diameter of the beam by changing the divergence angle of the laser beam to ensure that the subsequent optical elements can receive a uniform and appropriately sized laser beam; then, the laser beam enters the collimating mirror 3; the main function of the collimating mirror 3 is to adjust the direction of the laser beam so that it propagates in a straight line; this helps to ensure that the laser beam can be accurately received and processed by the subsequent mirror 4 and the single-frequency ultrasonic holographic lens 5; after passing through the collimating mirror 3, the laser beam is reflected by the mirror 4, thereby changing its propagation path; the setting of the mirror 4 enables the laser beam to enter the single-frequency ultrasonic holographic lens 5 along a predetermined path; finally, the laser beam enters the single-frequency ultrasonic holographic lens 5; the single-frequency ultrasonic holographic lens 5 includes a plurality of holographic units 551 with different thicknesses, and the single-frequency ultrasonic holographic lens 5 can absorb the energy of the laser beam according to the thermoelastic or thermoablation effect, generating an adjustable focusing ultrasonic field consistent with the frequency of the single-frequency ultrasonic holographic lens 5 on the backlight side of the single-frequency ultrasonic holographic lens 5, and the phase and amplitude of the adjustable focusing ultrasonic field are regulated by controlling the thickness of the holographic units 551; the thickness of the holographic units 551 in the single-frequency ultrasonic holographic lens 5 is designed according to requirements, so that it can generate an adjustable focusing ultrasonic field that meets the required number of foci, sound pressure, and focal length, and the number of foci, sound pressure, and focal length of the adjustable focusing ultrasonic field are adjusted by adjusting the thickness of the holographic units 551.

[0028] It should be noted that through the synergistic effect of the laser 1 and the single-frequency ultrasonic holographic lens 5, the device can efficiently convert the energy of the laser beam into the energy of the ultrasonic field, thereby achieving precise ultrasonic focusing on the target area; through the design of a plurality of holographic units 551 with different thicknesses, the thickness of the holographic units 551 can be designed according to the required number of foci, sound pressure, and focal length of the adjustable focusing ultrasonic field, so as to achieve the required adjustable focusing ultrasonic field; due to the linear propagation characteristics of the laser beam and the precise reflection effect of the mirror 4, the device can achieve high-precision positioning of the target area; this helps to ensure that the ultrasonic field can accurately act on the target area, improving the treatment effect or detection accuracy; the single-frequency laser ultrasonic focusing device can achieve long-distance non-contact laser drive without high-voltage excitation and wired connection of cables, greatly improving the durability, safety, convenience, and application fields compared with traditional ultrasonic sensors.

[0029] Further, the single-frequency ultrasonic holographic lens 5 includes a light focusing layer 51, an acoustic confinement layer 52, a light absorption layer 53, an acoustic matching layer 54, and a single-frequency acoustic holographic layer 55 arranged in sequence; wherein, the light focusing layer 51 is arranged on the reflection side of the mirror 4 and is used for condensing the laser beam reflected by the mirror 4; the acoustic confinement layer 52 is arranged on the backlight side of the light focusing layer 51; the light absorption layer 53 is arranged on the backlight side of the acoustic confinement layer 52 and is used for absorbing the laser beam and jointly converting the laser beam into a laser ultrasonic field through the acoustic confinement layer 52; the acoustic matching layer 54 is arranged on the backlight side of the light absorption layer 53 and is used for performing characteristic matching processing on the laser ultrasonic field; the single-frequency acoustic holographic layer 55 includes a plurality of holographic units 551 with different thicknesses, and the single-frequency acoustic holographic layer 55 is arranged on the backlight side of the acoustic matching layer 54 and is used for performing holographic processing on the laser ultrasonic field.

[0030] It should be understood that based on the above characteristic definitions, the light focusing layer 51 is the first part that the laser beam enters. It can have the characteristics of a convex lens or a concave lens and is used for initially focusing the laser beam or adjusting its direction to better match the requirements of subsequent layers; the acoustic confinement layer 52 is located behind the light focusing layer 51, and its main function is to limit or guide the propagation path of the sound wave or ultrasonic field generated by the laser beam and can transmit through the focused spot; this helps to reduce the scattering and loss of sound waves inside the lens and improve the focusing efficiency and directivity of the ultrasonic field; the light absorption layer 53 is a key part of the single-frequency ultrasonic holographic lens 5, and it is responsible for absorbing the focused and confined laser beam; during the absorption process, the energy of the laser beam is converted into mechanical energy or other forms of energy, thereby generating ultrasonic spherical waves on both the incident light side and the backlight side of the light absorption layer 53. After the spherical ultrasonic wave on the incident light side of the light absorption layer 53 is reflected by the acoustic confinement layer 52, it is superimposed with the ultrasonic spherical wave on the backlight side of the light absorption layer 53 to form a laser ultrasonic field; the acoustic matching layer 54 is located between the light absorption layer 53 and the single-frequency acoustic holographic layer 55, and its main function is to ensure that the laser ultrasonic field generated by the light absorption layer 53 can be efficiently transmitted to the single-frequency acoustic holographic layer 55; the acoustic matching layer 54 usually has acoustic characteristics similar to those of adjacent layers, such as acoustic impedance, sound velocity, and density, to reduce the reflection and loss of sound waves at the interface; the single-frequency acoustic holographic layer 55 is the final processing layer in the single-frequency acoustic holographic lens 5. It includes a plurality of holographic units 551 (or called pixels) with different thicknesses, and these holographic units 551 perform phase modulation on the ultrasonic waves in the laser ultrasonic field; by precisely designing the thickness and distribution of these holographic units 551, focusing, deflection, or other forms of manipulation of ultrasonic waves can be achieved; finally, an adjustable focusing ultrasonic field with the same frequency as the single-frequency ultrasonic holographic lens 5, and adjustable number of focal points, sound pressure, and focal length is generated in the acoustic propagation medium (solid, liquid, or gaseous medium) on the backlight side of the acoustic holographic layer 55.

[0031] It should be noted that the energy of the laser beam is efficiently converted into ultrasonic waves through the light absorption layer 53, realizing the conversion from light energy to sound energy. This conversion process features high efficiency and stability, contributing to the generation of a stable ultrasonic field. The single-frequency acoustic holographic layer 55 achieves precise focusing and manipulation of ultrasonic waves through the structure of the precisely designed holographic unit 551. This helps generate an ultrasonic field with high resolution and high intensity, suitable for various precision detection and imaging tasks. By adjusting the thickness and distribution of the holographic unit 551 in the single-frequency acoustic holographic layer 55, parameters such as the focusing position, intensity, and direction of the ultrasonic field can be flexibly changed. This flexibility enables the device to adapt to different application scenarios and requirements. Since the device uses the interaction between the laser beam and the ultrasonic field for detection, there is no need to directly contact the object to be measured. This helps reduce interference and damage to the object to be measured and improves the accuracy and reliability of detection. The single-frequency laser ultrasonic focusing device has broad application prospects, including fields such as acoustic control and drive, biomedical imaging and treatment, and industrial non-destructive testing and characterization. Its characteristics of high precision, high efficiency, and non-contact make it have unique advantages in these fields. Furthermore, the light focusing layer 51 is a hemispherical lens or an array of multiple hemispherical lenses. The hemispherical lens focuses the laser beam to generate a focused spot. The acoustic confinement layer 52 is a first light-transmitting nylon layer, and the focused spot passes through the first light-transmitting nylon layer and enters the light absorption layer 53. The light absorption layer 53 is a black metal film. After the black metal film absorbs the focused spot, ultrasonic spherical waves are emitted simultaneously on the light-incident side and the backlight side of the black metal film. The ultrasonic spherical waves on the light-incident side are reflected and confined by the first light-transmitting nylon layer and then superposed with the ultrasonic spherical waves on the backlight side to form a laser ultrasonic field. The acoustic matching layer 54 is a second light-transmitting nylon layer, and the second light-transmitting nylon layer performs acoustic characteristic matching processing on the laser ultrasonic field. The single-frequency acoustic holographic layer 55 is composed of multiple holographic units 551 with different thicknesses connected together. The holographic unit 551 performs holographic processing on the laser ultrasonic field to obtain an adjustable focused ultrasonic field.

[0032] It should be understood that based on the above feature limitations, the laser enters from the light incident side of the light focusing layer 51; the laser passes through a hemispherical lens or a plurality of hemispherical lenses arranged in an array in the light focusing layer 51; the hemispherical lenses can be rapidly prepared by 3D printing, and the design of these hemispherical lenses enables the laser beam to be focused, thereby forming a focused spot or an array of multiple focused spots on the backlight side of the light focusing layer; the number and position of the focused spots depend on the number, shape, and arrangement of the hemispherical lenses in the light focusing layer 51; the focused spots enter from the light incident side of the acoustic confinement layer 52, and the acoustic confinement layer 52 is a first light-transmitting nylon layer, enabling the focused spots generated by the light focusing layer 51 to pass through the first light-transmitting nylon layer and reach the light absorption layer 53, and the first light-transmitting nylon layer can confine and direct the ultrasonic spherical wave generated by the light absorption layer 53; the nylon material has good light transmittance and certain acoustic properties, enabling the acoustic confinement layer 52 to both allow the focused spots to pass through and confine and reflect the ultrasonic waves generated by the light absorption layer 53; through its material properties and structural design, the acoustic confinement layer 52 limits the propagation range of the ultrasonic waves within the layer, preventing them from spreading to the surroundings, thereby maintaining the focused state of the ultrasonic spherical wave; the focused spots passing through the acoustic confinement layer 52 enter from the light incident side of the light absorption layer 53, and the light absorption layer 53 is a black metal thin film, which can convert the energy of the focused spots into mechanical energy; in the black metal thin film, the focused spots are absorbed and converted into ultrasonic spherical waves; these ultrasonic spherical waves are emitted from both the light incident side and the backlight side of the black metal thin film; it should be noted that due to the structural design of the black metal thin film, it allows part of the laser energy to be emitted from the backlight side of the black metal thin film in the form of ultrasonic spherical waves, and at the same time, a part of the ultrasonic spherical waves are emitted from the light incident side of the black metal thin film. The ultrasonic spherical waves emitted from the light incident side of the black metal thin film are superimposed with the ultrasonic spherical waves emitted from the backlight side of the black metal thin film under the confinement and reflection of the first light-transmitting nylon layer to form a laser ultrasonic field; the laser ultrasonic field enters from the light incident side of the acoustic matching layer 54, and the acoustic matching layer 54 is a second light-transmitting nylon layer; the main function of the second light-transmitting nylon layer is to adjust the acoustic characteristics of the laser ultrasonic field to match the subsequent single-frequency acoustic holographic layer 55; this includes adjusting the propagation speed and impedance of the laser ultrasonic field to reduce reflection and scattering; after being processed by the acoustic matching layer 54, the laser ultrasonic field is emitted from the backlight side of the acoustic matching layer 54, and at this time its acoustic characteristics have been matched with the single-frequency acoustic holographic layer 55; the laser ultrasonic field after acoustic characteristic matching enters from the light incident side of the single-frequency acoustic holographic layer 55; the single-frequency acoustic holographic layer 55 is composed of a plurality of holographic units 551 with different thicknesses, and these holographic units 551 are all made of polymers with acoustic impedance matching the acoustic propagation medium. These holographic units 551 can generate a specific ultrasonic field according to the propagation path and phase difference of the sound waves; in the single-frequency acoustic holographic layer 551, the laser ultrasonic field undergoes holographic processing, is focused, and converted into an adjustable focused ultrasonic field;The thickness of the holographic unit 551 can be designed according to the number of focal points, sound pressure, and focal length of the adjustable focused ultrasound field as needed, so as to obtain an adjustable focused ultrasound field that meets the design requirements, thereby realizing the adjustability of the adjustable focused ultrasound field; finally, the adjustable focused ultrasound field is emitted from the backlight side of the single-frequency acoustic holographic layer and is ready for subsequent applications or detection tasks.

[0033] Specifically, the thickness of the first light-transmitting nylon layer is 1 mm; the thickness of the black metal film is 0.2 mm; the thickness of the second light-transmitting nylon layer is 0.5 mm.

[0034] It should be understood that based on the above characteristic limitations, a thickness of 1 mm provides sufficient space to confine the ultrasonic waves generated by the focused light spot; the nylon material has good toughness and light transmittance, and can effectively limit the propagation range of ultrasonic waves while maintaining the transmissibility of the laser beam, preventing it from spreading to the surroundings; this design helps to maintain the focused state of the ultrasonic waves and improve the energy density of the ultrasonic field; a thickness of 0.2 mm enables the black metal film to maintain good flexibility and processability while ensuring sufficient light absorption; the black metal film has a very high absorption rate for the laser beam and can quickly convert the energy of the laser beam into mechanical energy; this design helps to achieve efficient photo-thermal conversion and thus generate high-intensity ultrasonic waves; a thickness of 0.5 mm is a good acoustic transition between the acoustic matching layer 54 and the single-frequency acoustic holographic layer 55; the nylon material has good acoustic properties and can reduce the reflection and scattering of ultrasonic waves during transmission; this design helps to ensure that ultrasonic waves can be efficiently transmitted to the single-frequency acoustic holographic layer 55 and reduce the energy loss during transmission.

[0035] It should be noted that through reasonable layer thickness design, each layer can work together to achieve efficient conversion of the laser beam to the focused ultrasound field; this design ensures high-precision focusing of the ultrasonic beam and meets the precise control requirements of the position and intensity of the ultrasonic beam in different application scenarios; the thin thickness design of the black metal film enables it to efficiently absorb the energy of the laser beam and convert it into mechanical energy; this design improves the energy conversion efficiency of the entire system and reduces energy consumption; although the layer thickness design itself does not directly determine the frequency of the ultrasonic field, reasonable layer thickness helps to maintain the focused state and energy density of the ultrasonic waves, thus supporting the single-frequency acoustic holographic layer to generate an adjustable focused ultrasound field with focusing characteristics at the preset focal length; this device has the advantages of high-precision focusing, efficient energy conversion, and adjustable frequency characteristics, so it can be widely used in fields such as non-destructive testing, medical diagnosis and treatment, and materials science research; especially in application scenarios that require precise control of the position and intensity of the ultrasonic beam, this device has significant advantages.

[0036] Furthermore, by adjusting the thickness of the holographic unit 551, the phase and amplitude of the ultrasonic waves in the adjustable focused ultrasound field are controlled.

[0037] It should be understood that based on the above feature definitions, the single-frequency acoustic holographic layer 55 is composed of multiple closely connected holographic units 551; these holographic units 551 may vary in size, shape, and thickness to achieve precise control of the acoustic wave propagation path and phase difference; the thickness of each holographic unit 551 is carefully designed to ensure that when the acoustic wave passes through, specific phase delays and amplitude changes can be generated; the phase of the acoustic wave refers to the time or phase angle by which the vibration state of the acoustic wave at a certain point in space lags behind the vibration state of a certain reference point; in the single-frequency acoustic holographic layer, by adjusting the thickness of the holographic unit 551, the phase delay generated when the acoustic wave passes through different holographic units can be changed; this difference in phase delay enables the acoustic wave to form a specific phase distribution during propagation, thereby achieving a focusing effect; the amplitude of the acoustic wave refers to the vibration amplitude of the acoustic wave at a certain point in space; although the thickness of the holographic unit 551 mainly affects the phase of the acoustic wave, it also affects the amplitude of the acoustic wave to a certain extent; when the acoustic wave passes through holographic units with different thicknesses, part of the acoustic wave energy may be absorbed, refracted, or reflected, resulting in changes in the amplitude of the acoustic wave; however, in the design of the single-frequency acoustic holographic layer 55, more emphasis is placed on achieving the focusing effect through phase control, while the change in amplitude is considered as a secondary factor; therefore, the thickness of each holographic unit 551 in the single-frequency acoustic holographic layer 55 can be precisely designed and adjusted according to the required focal length to achieve precise control of the acoustic wave propagation path and phase difference; when the laser ultrasonic field passes through the single-frequency acoustic holographic layer 55, the acoustic wave will be focused and converted into an adjustable focused ultrasonic field with the required number of focal points, sound pressure, and focal length, thereby achieving the adjustability of the focused ultrasonic field.

[0038] It should be noted that the single-frequency acoustic holographic layer 55 plays a crucial role in the single-frequency laser ultrasonic focusing device; by precisely controlling the phase and amplitude of the ultrasonic wave, this device can achieve efficient, precise, and flexible laser ultrasonic focusing; this technology has broad application prospects in the fields of material detection, biomedical imaging, non-destructive testing, etc.; for example, in biomedical imaging, this technology can be used to achieve high-resolution imaging of internal organs and tissues of the human body; in non-destructive testing, it can be used to detect defects and damages in materials such as metals and plastics; however, the single-frequency acoustic holographic layer 55 achieves precise control of the phase and amplitude of the ultrasonic wave through its unique holographic unit structure and precise thickness design; this technology provides broad space and possibilities for the application of the single-frequency laser ultrasonic focusing device.

[0039] Specifically, the thickness of the holographic unit 551 and the phase of the ultrasonic wave satisfy the following relationship: , where, represents the phase of the ultrasonic wave, represents the preset ultrasonic frequency, represents the sound speed of the propagation medium, represents the sound speed of the holographic unit, represents the thickness of the holographic unit.

[0040] It should be noted that the phase of the ultrasonic wave is directly proportional to both the preset ultrasonic frequency and the thickness of the holographic unit.

[0041] Specifically, the thickness of the holographic unit 551 and the amplitude of the ultrasonic wave satisfy the following relationship: , wherein, represents the amplitude of the ultrasonic wave, represents the sound pressure of the ultrasonic spherical wave that has undergone acoustic characteristic matching and is emitted from the acoustic matching layer, represents the thickness of the polygonal 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 the single-frequency acoustic holographic layer.

[0042] It should be noted that the amplitude of the ultrasonic wave is directly proportional to both the sound pressure of the ultrasonic spherical wave and the thickness of the holographic unit.

[0043] Furthermore, the number of focal points of the single-frequency ultrasonic holographic lens 5 is one or more, and the number of focal points of the adjustable focusing ultrasonic field generated on the backlight side of the single-frequency ultrasonic holographic lens 5 correspondingly is one or more.

[0044] It should be understood that based on the above characteristic definitions, the number of focal points of the single-frequency ultrasonic holographic lens 5 can be one or more; by adjusting the parameters and structure of the single-frequency ultrasonic holographic lens 5, the single-frequency ultrasonic holographic lens 5 can generate one or more clear focal points on the backlight side; since there is a corresponding relationship between the number of focal points of the single-frequency ultrasonic holographic lens 5 and the number of focal points of the adjustable focusing ultrasonic field, when the number of focal points of the single-frequency ultrasonic holographic lens 5 is one, the number of focal points of the adjustable focusing ultrasonic field generated on the backlight side is also one; when the number of focal points of the single-frequency ultrasonic holographic lens 5 is multiple, the number of focal points of the adjustable focusing ultrasonic field generated on the backlight side is also multiple; It should be noted that the focus is the preset point where the single - frequency ultrasonic holographic lens 5 converges ultrasonic energy, and it is the core part of the adjustable focusing ultrasonic field; at the focus, the energy density of ultrasonic waves is the highest, so it has the strongest effect; the adjustable focusing ultrasonic field is formed by the outward expansion of the ultrasonic energy at the focus; in the ultrasonic field, except at the focus, the energy density of ultrasonic waves in other regions gradually decreases, but still has a certain effect; since the focus is the core part of the ultrasonic field generated by the single - frequency ultrasonic holographic lens 5, the number of foci directly determines the number of adjustable focusing ultrasonic fields; therefore, when the single - frequency ultrasonic holographic lens 5 has one focus, the backlight side will generate an adjustable focusing ultrasonic field with the number of foci; when the single - frequency ultrasonic holographic lens 5 has multiple foci, the backlight side will generate multiple adjustable focusing ultrasonic fields with the number of foci.

[0045] Furthermore, the laser 1 can be either a continuous - modulation laser or a pulsed laser.

[0046] It should be noted that when the laser 1 is a continuous - modulation laser, its modulation frequency is the same as the frequency of the single - frequency ultrasonic holographic lens 5, and the frequency of the adjustable focusing ultrasonic field generated on the backlight side of the single - frequency ultrasonic holographic lens 5 is the same as the frequency of the single - frequency ultrasonic holographic lens 5; however, since the ultrasonic field generated by the laser beam emitted by the pulsed laser has an infinite bandwidth, when the laser 1 is a pulsed laser, the center frequency of the adjustable focusing ultrasonic field generated on the backlight side of the single - frequency ultrasonic holographic lens 5 is the same as the frequency of the single - frequency ultrasonic holographic lens 5.

[0047] A single-frequency laser ultrasonic focusing device according to this embodiment, the laser beam output by the laser 1, which is the starting light source of the entire device; the beam expander 2 receives the laser beam from the laser 1 and adjusts its diameter to meet the requirements of subsequent optical elements; the collimating mirror 3 is arranged on the backlight side of the beam expander 2 to ensure that the expanded laser beam propagates in a straight line and avoid beam divergence; the reflecting mirror 4 changes the propagation path of the laser beam and guides it to the single-frequency ultrasonic holographic lens 5; inside the single-frequency ultrasonic holographic lens 5, the laser beam first passes through the light focusing layer 51, where a hemispherical lens or an array of multiple hemispherical lenses focuses the laser beam to form a focused spot or an array of multiple focused spots; the focused spot enters the acoustic confinement layer 52, which performs acoustic confinement processing on the laser beam to ensure that the laser energy is effectively converted into acoustic energy; the focused spot after acoustic confinement processing enters the light absorption layer 53, which absorbs the laser energy and converts it into an ultrasonic spherical wave; ultrasonic spherical waves are emitted simultaneously on both sides of the light absorption layer 53; the ultrasonic spherical wave emitted from the light incident side of the light absorption layer 53 is reflected by the acoustic confinement layer 52 and superimposed with the ultrasonic spherical wave emitted from the backlight side of the light absorption layer 53 to form a laser ultrasonic field; the laser ultrasonic field enters the acoustic matching layer 54, which performs acoustic characteristic matching on the laser ultrasonic field to ensure that it matches the acoustic characteristics of the target material; the laser ultrasonic field after acoustic characteristic matching enters the single-frequency acoustic holographic layer 55, which processes the laser ultrasonic field using holographic technology to form an adjustable focusing ultrasonic field. Since the number of focal points of the single-frequency ultrasonic holographic lens 5 can be one or more, the number of focal points of the finally generated adjustable focusing ultrasonic field also corresponds to one or more, and the thickness of the holographic unit 551 in the single-frequency ultrasonic holographic lens 5 can be designed according to needs, so that it can generate an adjustable focusing ultrasonic field with the number of focal points, sound pressure and focal length meeting the design requirements, and the number of focal points, sound pressure and focal length of the adjustable focusing ultrasonic field are adjusted by adjusting the thickness of the holographic unit 551; so that the finally generated adjustable focusing ultrasonic field meets the set focusing requirements; the adjustable focusing ultrasonic field is emitted from the backlight side of the single-frequency acoustic holographic layer 55 for non-contact detection or processing of the target material.

[0048] Embodiment 2 A design method of a single-frequency laser ultrasonic focusing device, including: Arrange the positions of the laser, beam expander, collimating mirror and reflecting mirror so that the laser beam output by the laser passes through the beam expander, collimating mirror and reflecting mirror in sequence; Use transparent nylon for 3D printing to generate 90×90 hemispherical lenses with a diameter of 0.1 mm, arrange the hemispherical lens array to obtain a light focusing layer with a focal length of 1 mm; Use transparent nylon for 3D printing to generate an acoustic confinement layer with a thickness of 1 mm and an acoustic matching layer with a thickness of 0.5 mm; A black metal thin film with a thickness of 0.2 mm is used as the light absorption layer, and the acoustic confinement layer and the acoustic matching layer are respectively pasted on both sides of the light absorption layer; The light focusing layer is pasted on the side of the acoustic confinement layer away from the light absorption layer; Taking the preset frequency of the acoustic holographic layer as 300 KHz as an example, according to the preset focal length of 6 mm and the interval of 3 mm between the double focal point projections, through the 3D printing process, polymers with acoustic impedance matching the acoustic propagation medium are made into a plurality of holographic units with different thicknesses, and the size of the holographic unit is 0.5 mm × 0.5 mm; The single-frequency acoustic holographic layer with a size of 9 mm × 9 mm is formed by closely connecting the holographic units, and the single-frequency acoustic holographic layer is pasted on the side of the acoustic matching layer away from the light absorption layer to obtain a single-frequency ultrasonic holographic lens with a preset ultrasonic frequency of 300 KHz; The single-frequency ultrasonic holographic lens is arranged on the reflection side of the mirror, so that the laser beam emitted from the mirror enters the single-frequency ultrasonic holographic lens through the light focusing layer, and an adjustable focusing ultrasonic field consistent with the frequency of the single-frequency ultrasonic holographic lens is generated from the single-frequency acoustic holographic layer.

[0049] A design method of a single-frequency laser ultrasonic focusing device according to this embodiment uses a pulsed laser or a continuous modulation laser with a modulation frequency of 300 KHz to generate a laser beam. This laser beam passes through a beam expander to enlarge or reduce the beam diameter to ensure that the beam can match the entire optical focusing layer. Subsequently, the laser is calibrated by a collimating mirror to ensure that the beam is parallel and collimated. The reflecting mirror is used to reflect and direct the laser beam to the optical focusing layer to achieve the focusing and guiding of the laser. The optical focusing layer composed of 90×90 hemispherical lenses with a diameter of 0.1 mm can further focus the laser beam to a smaller point or line, improving the energy density of the laser. Each hemispherical lens can be regarded as a small focusing element, jointly forming a high-precision laser focusing array. The black metal film serves as an optical absorption layer, which can absorb the laser energy not focused by the optical focusing layer to prevent its scattering or reflection from interfering with the device. The acoustic confinement layer is used to limit the propagation direction of sound waves to ensure that the sound waves can propagate along a predetermined path to the single-frequency acoustic holographic layer. The acoustic matching layer is used to reduce the reflection and scattering of sound waves when propagating between different media, improving the transmission efficiency of sound waves. The polymer holographic units fabricated by 3D printing have an acoustic impedance matching the acoustic propagation medium (such as air), which can reduce the reflection of sound waves between the acoustic propagation medium (such as air) and the holographic units. These holographic units are closely connected to form a single-frequency acoustic holographic layer. When the laser beam is focused on the holographic units through the optical focusing layer, a thermal effect will cause the gas in the holographic units to expand, thereby generating ultrasonic waves. Due to the different thicknesses of the holographic units, their absorption and conversion efficiencies for the laser are also different, so that ultrasonic waves with different phases and amplitudes can be generated. These ultrasonic waves interfere with each other within the single-frequency acoustic holographic layer to form an adjustable focusing ultrasonic field consistent with the frequency of the single-frequency ultrasonic holographic lens.

[0050] Since the design method of a single-frequency laser ultrasonic focusing device in this embodiment prepares the single-frequency laser ultrasonic focusing device in Embodiment 1, it has all the beneficial effects of this single-frequency laser ultrasonic focusing device and will not be elaborated here.

[0051] Embodiment 3 An ultrasonic device includes a single-frequency laser ultrasonic focusing device provided in Embodiment 1, and the ultrasonic device can be used for ultrasonic manipulation and driving, ultrasonic detection and imaging, low-power ultrasonic stimulation, and power ultrasonic treatment.

[0052] An ultrasonic device according to this embodiment includes a single-frequency laser ultrasonic focusing device provided in Embodiment 1, so it has all the beneficial effects of this single-frequency laser ultrasonic focusing device and will not be elaborated here.

[0053] In this application, the term "a plurality of" means two or more, unless otherwise clearly defined. Terms such as "installed", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "coupled" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0054] In the description of this specification, the descriptions of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or instance. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0055] The foregoing are only the preferred embodiments of this application and are not intended to limit this application. For those skilled in the art, various modifications and variations can be made to this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A single-frequency laser ultrasonic focusing device, characterized in that The device includes: a laser for outputting a laser beam; a beam expander for adjusting the diameter of the laser beam; a collimating mirror disposed on the backlight side of the beam expander, the collimating mirror being used to adjust the direction of the laser beam so that the laser beam propagates linearly; a reflecting mirror disposed on the backlight side of the collimating mirror for changing the propagation path of the laser beam; a single-frequency ultrasonic holographic lens disposed on the reflection side of the reflecting mirror, the single-frequency ultrasonic holographic lens including a plurality of holographic units with different thicknesses, the single-frequency ultrasonic holographic lens being used to absorb the laser beam and generate an adjustable focusing ultrasonic field consistent with the frequency of the single-frequency ultrasonic holographic lens on the backlight side thereof.

2. The single-frequency laser ultrasonic focusing device according to claim 1, characterized in that, The single-frequency ultrasonic holographic lens includes: an optical focusing layer disposed on the reflection side of the reflecting mirror for condensing the laser beam reflected by the reflecting mirror; an acoustic confinement layer disposed on the backlight side of the optical focusing layer; an optical absorption layer disposed on the backlight side of the acoustic confinement layer for absorbing the laser beam and jointly converting the laser beam into a laser ultrasonic field through the acoustic confinement layer; an acoustic matching layer disposed on the backlight side of the optical absorption layer for performing characteristic matching processing on the laser ultrasonic field; a single-frequency acoustic holographic layer including a plurality of holographic units with different thicknesses, the single-frequency acoustic holographic layer being disposed on the backlight side of the acoustic matching layer for performing holographic processing on the laser ultrasonic field.

3. A single-frequency laser ultrasonic focusing device according to claim 2, characterized in that The optical focusing layer is a hemispherical lens or a plurality of hemispherical lenses arranged in an array, and the hemispherical lens condenses the laser beam to generate a focused spot; The acoustic confinement layer is a first light-transmitting nylon layer, and the focused spot passes through the first light-transmitting nylon layer and enters the optical absorption layer; The optical absorption layer is a black metal film. After the black metal film absorbs the focused spot, ultrasonic spherical waves are emitted simultaneously on the light-incident side and the backlight side of the black metal film. The ultrasonic spherical wave on the light-incident side is reflected and constrained by the first light-transmitting nylon layer and superposed with the ultrasonic spherical wave on the backlight side to form a laser ultrasonic field; The acoustic matching layer is a second light-transmitting nylon layer, and the second light-transmitting nylon layer performs acoustic characteristic matching processing on the laser ultrasonic field; The single-frequency acoustic holographic layer is formed by connecting a plurality of holographic units with different thicknesses, and the holographic units perform holographic processing on the laser ultrasonic field to obtain the adjustable focusing ultrasonic field.

4. The single-frequency laser ultrasonic focusing device according to claim 3, wherein The phase and amplitude of the ultrasonic waves in the adjustable focusing ultrasonic field are controlled by adjusting the thickness of the holographic units.

5. A single-frequency laser ultrasonic focusing device according to claim 4, characterized in that, The thickness of the holographic unit and the phase of the ultrasonic wave satisfy the following relationship: ， Among them, represents the phase of the ultrasonic wave, represents the preset ultrasonic frequency, represents the sound velocity of the propagation medium, represents the sound velocity of the holographic unit, represents the thickness of the holographic unit.

6. The single-frequency laser ultrasonic focusing device according to claim 4, characterized in that, The thickness of the holographic unit and the amplitude of the ultrasonic wave satisfy the following relationship: ， Among them, represents the amplitude of the ultrasonic wave, represents the sound pressure of the ultrasonic spherical wave after acoustic characteristic matching emitted from the acoustic matching layer, 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 the single-frequency acoustic holographic layer.

7. A single-frequency laser ultrasonic focusing device according to claim 2, characterized in that, The number of focal points of the single-frequency ultrasonic holographic lens is one or more, and the number of focal points of the adjustable focusing ultrasonic field generated on the backlight side of the single-frequency ultrasonic holographic lens corresponds to one or more.

8. A single-frequency laser ultrasonic focusing device according to claim 1, characterized in that, The laser is any one of a continuous modulation laser and a pulsed laser.

9. A design method of a single-frequency laser ultrasonic focusing device, capable of fabricating a single-frequency laser ultrasonic focusing device according to any one of claims 1-8, characterized in that, The method includes: arranging the positions of the laser, the beam expander, the collimating mirror and the reflecting mirror so that the laser beam output by the laser sequentially passes through the beam expander, the collimating mirror and the reflecting mirror; 3D printing is carried out using transparent nylon to generate 90×90 hemispherical lenses with a diameter of 0.1 mm, and the hemispherical lens array is arranged to obtain a light focusing layer; 3D printing is carried out using transparent nylon to generate an acoustic confinement layer with a thickness of 1 mm and an acoustic matching layer with a thickness of 0.5 mm; A black metal film with a thickness of 0.2 mm is used as the light absorption layer, and the acoustic confinement layer and the acoustic matching layer are respectively pasted on both sides of the light absorption layer; The light focusing layer is pasted on the side of the acoustic confinement layer away from the light absorption layer; According to the preset focal length, through the 3D printing process, polymers with acoustic impedance matching the acoustic propagation medium are made into a plurality of holographic units with different thicknesses; The single-frequency acoustic holographic layer is formed by closely connecting the holographic units, and the single-frequency acoustic holographic layer is pasted on the side of the acoustic matching layer away from the light absorption layer to obtain a single-frequency ultrasonic holographic lens; The single-frequency ultrasonic holographic lens is arranged on the reflection side of the mirror, so that the laser beam emitted from the mirror passes through the light focusing layer and enters the single-frequency ultrasonic holographic lens, and an adjustable focusing ultrasonic field with the same frequency as the single-frequency ultrasonic holographic lens is generated from the single-frequency acoustic holographic layer.

10. An ultrasonic device, comprising a single-frequency laser ultrasonic focusing device according to any one of claims 1-8, characterized in that, The ultrasonic device can be used for ultrasonic manipulation and driving, ultrasonic detection and imaging, low-power ultrasonic stimulation, and power ultrasonic therapy.

Images