A broadband asymmetric acoustic spiral focusing lens device

Abstract

The present invention discloses a broadband asymmetric acoustic spiral focusing lens device, which belongs to the field of acoustic metamaterials. The lens structure is disk-shaped as a whole, with a solid cylinder at the center, and twelve equally large fan-shaped composite structures connected in the circumferential direction. The radius and height of the central solid cylinder are r and l respectively. The central angle of each fan-shaped composite structure is 30°, and four asymmetric mode converters are arranged in sequence in the diameter direction, and their cross-sections are the same. Each asymmetric mode converter includes four phase-controlled units and a convex waveguide. The phase-controlled units are arranged in sequence along the diameter, and the convex waveguide is located above the phase-controlled units and connected to each other. By changing the phase distribution of the acoustic spiral focusing lens device, first-order, second-order, and third-order acoustic spiral beams can be achieved. The present invention has high transmittance characteristics and can be used in the fields of particle capture, particle suspension and rotation, ocean positioning, information transmission, etc. It has broad application prospects in medical diagnosis and marine communications.

Description

Technical Field

[0001] The present invention relates to acoustic metamaterial technology, and in particular to a broadband asymmetric acoustic spiral focusing lens device. Background Art

[0002] Helical acoustic beams possess unique acoustic orbital angular momentum, opening up new degrees of freedom in acoustic wave manipulation. They can not only transmit mechanical effects on objects, enabling particle manipulation, but also utilize their unique helical phase information for acoustic signal transmission. Designing an acoustic helical focusing lens device to achieve helical focusing in free space can maintain a well-defined helical beam waveform at a specific location. Furthermore, helical focusing can apply a torque remotely, without contacting the object, to precisely manipulate tiny objects. For example, this can capture or select microparticles at specific spatial locations, levitate, and rotate them. This provides a solution for advanced in vivo acoustic tweezers, enabling fracture removal and deeper penetration into lesions, effectively addressing key medical diagnostic challenges. It also provides a foundational device for future technological innovations in deep-sea exploration and positioning. Furthermore, researchers are also focusing on the safety and interference resistance of the device. The device's asymmetric transmission effect effectively isolates external interference and provides internal device protection. Therefore, the research on broadband asymmetric acoustic helical focusing lens devices is not only of fundamental academic significance but also holds great promise for broad application in various critical applications.

[0003] At present, the methods used by researchers at home and abroad to achieve acoustic helical beams with orbital angular momentum can be divided into two categories: active and passive:

[0004] (1) Traditionally, active technology is essentially an acoustic phased array technology. Researchers use multiple independently controlled acoustic transducers to form an array, and use a digital signal processor to modulate the phased source to achieve acoustic-to-electronic signal conversion, thereby generating the required spiral spatial phase distribution to obtain an acoustic spiral beam. On this basis, researchers have also experimentally achieved the manipulation of underwater microparticles using an acoustic vortex beam.

[0005] (2) In passive methods, researchers mainly introduce spiral propagation paths by designing thickness gradient structures or acoustic plates with spiral structures to generate the spiral phase distribution required for the spiral field. In experiments, researchers can observe acoustic spiral beams on the surface of the structure or in waveguides with hard boundaries.

[0006] The disadvantages of traditional technology are :

[0007] (1) The realization of acoustic helical beam based on active system has the disadvantages of complex structure, large size and complicated circuit control, which also leads to high cost. This also brings certain difficulties to its application in high frequency range.

[0008] (2) The acoustic helical beam exciter designed with a passive helical structure has a narrow operating frequency band, mostly a single frequency, and is large in size.

[0009] (3) The acoustic helical beam generated by existing acoustic helical devices can usually only maintain the vortex waveform within a short distance, and the acoustic wave energy transmittance is limited by the structure.

[0010] The reasons for the defects of traditional technology are :

[0011] (1) Using an active system to generate a nearly continuous spiral wavefront requires ensuring that the phase of the drive signal corresponding to each transducer is precisely modulated. This results in the system requiring the use of a large number of transducers to form an acoustic array and the use of complex circuits to independently control each unit.

[0012] (2) To realize an acoustic helical beam based on a passive structure, the structural size must be much larger than the acoustic wavelength, and the structure itself must have the geometric characteristics of a spiral distribution. Summary of the Invention

[0013] To address the technical challenges of conventional acoustic spiral excitation devices, such as their narrow operating frequency band, sometimes even a single frequency, large size, complex structure, and low transmittance due to surface limitations, this paper proposes a broadband asymmetric acoustic spiral focusing lens device with a compact design, broadband bandwidth, the ability to generate an acoustic spiral beam at a specific location in free space, and high transmittance.

[0014] The present invention achieves the above technical objectives through the following technical means.

[0015] A broadband asymmetric acoustic spiral focusing lens device has an overall disc-shaped lens structure with a solid cylinder at its center, connected to twelve equally sized fan-shaped composite structures in the circumferential direction. The radius and height of the central solid cylinder are r and l, respectively. Each fan-shaped composite structure has a central angle of 30°, and four asymmetric mode converters are arranged in sequence in the diameter direction, with the same cross-sectional size. Each asymmetric mode converter includes four phased units and a convex waveguide. The phased units are arranged in sequence along the diameter direction. The convex waveguide is located above the phased units and is interconnected, and its frame wall thickness is t. The height and width of the phased unit are l and r1, respectively. The height and width of the large waveguide in the convex waveguide are h1 and 4r1, respectively. The height and width of the small waveguide are h2 and w1, respectively.

[0016] Furthermore, the structural parameters of the acoustic spiral focusing lens are: the radius of the central solid cylinder is 4.5cm≤r≤6.5cm; the height of the phased unit is 3.6cm≤l≤5cm, and the width is 1cm≤r1≤1.2cm; the frame thickness is 0.8cm≤t≤1.2cm; the height of the convex large waveguide is 1.2cm≤h1≤1.8cm; the height of the convex small waveguide is 0.9cm≤h2≤1.1cm, and the width is 1.8cm≤w1≤2.3cm.

[0017] Furthermore, the broadband asymmetric acoustic spiral focusing lens device is prepared by 3D printing technology.

[0018] Furthermore, the broadband asymmetric acoustic spiral focusing lens device is made of one of organic glass, plastic and metal.

[0019] Furthermore, the order of the acoustic helical beam generated by the broadband asymmetric acoustic helical focusing lens device can be 1, 2, or 3.

[0020] The beneficial effects of the present invention are:

[0021] (1) The broadband asymmetric acoustic spiral focusing lens device achieves rich functional effects

[0022] The acoustic spiral focusing lens device proposed in the present invention can achieve an asymmetric transmission effect, can realize a high-performance acoustic spiral focusing effect at a specific position, and can achieve precise control of tiny objects without contacting the objects.

[0023] (2) The broadband asymmetric acoustic spiral focusing lens device has broadband and adjustable spiral focusing position.

[0024] The acoustic spiral focusing lens device proposed in the present invention achieves an asymmetric acoustic spiral focusing effect in the frequency range of 6200-7400 Hz. In addition, by adjusting the frequency of the incident sound wave, the acoustic spiral focusing lens device can excite acoustic spiral focusing beams at different positions.

[0025] (3) Wideband asymmetric acoustic spiral focusing lens devices can realize a variety of acoustic spiral beams.

[0026] The acoustic spiral focusing lens device proposed in the present invention can excite acoustic spiral beams with diversity, and the phase distribution of the acoustic spiral focusing lens device can be changed, thereby exciting 1st, 2nd and 3rd order acoustic spiral beams. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1Schematic diagrams of the structure of the first embodiment of the broadband asymmetric acoustic spiral focusing lens device described in the present invention. (a) A 3D-printed sample of the acoustic spiral focusing lens; (b) A schematic diagram of a two-dimensional cross-section of the acoustic spiral focusing lens.

[0028] Figure 2 The spatial distribution of the sound pressure amplitude corresponding to the asymmetric mode converter in the acoustic spiral focusing lens device.

[0029] Figure 3 This is the second embodiment of the broadband asymmetric acoustic spiral focusing lens device of the present invention, showing the spatial distribution of acoustic energy generated by the acoustic spiral focusing lens device being excited by (a) top and (b) bottom incident acoustic waves.

[0030] Figure 4 Figure 3. Spatial distribution of acoustic energy generated by acoustic waves passing through the acoustic spiral focusing lens device from (a) the top and (b) the bottom at different input frequencies.

[0031] Figure 5 This is the third embodiment of the broadband asymmetric acoustic spiral focusing lens device of the present invention. The acoustic spiral focusing lens excites spiral orders of (a) first-order and (b) third-order acoustic spiral focusing beams. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0033] The broadband asymmetric acoustic spiral focusing lens device described in the present invention is composed of twelve equal-sized fan-shaped composite structures connected around a solid cylinder at the center. Each fan-shaped composite structure has a central angle of 30°, and four asymmetric mode converters are arranged in sequence in the diameter direction, and their cross-sections are the same. Each asymmetric mode converter includes four phase-controlled units and a convex waveguide. The phase-controlled units are arranged in sequence along the diameter, and the convex waveguide is located above the phase-controlled units and is interconnected. The material of the broadband asymmetric acoustic spiral focusing lens device is one of organic glass, plastic, and metal materials.

[0034] The acoustic spiral focusing lens device has asymmetric spiral focusing properties. When plane wave sound source signals are incident from the top and bottom of the lens, the acoustic spiral focusing lens only allows the sound wave incident from the top to pass through the lens, achieving a spiral focusing effect in a specific area below, while sound waves incident from the bottom are blocked from passing through the lens.

[0035] The acoustic spiral focusing lens device has a wide bandwidth, and the spiral focusing position can be adjusted. For sound waves of different incident frequencies, top-incident sound waves can all pass through the lens, achieving acoustic spiral focusing at different positions; however, bottom-excited sound waves cannot pass through the lens. The operating frequency band is 6200-7400Hz, demonstrating wide-bandwidth characteristics.

[0036] The acoustic spiral focusing lens device can realize a variety of acoustic spiral focusing beams. By changing the phase distribution of the lens, the acoustic spiral focusing lens device can realize first-order, second-order, and third-order acoustic spiral focusing effects.

[0037] In order to verify the sound propagation effect of the broadband asymmetric acoustic spiral focusing lens device of the present invention, the finite element method was used to numerically simulate the acoustic wave enhanced transmission performance. The simulation process and results are as follows:

[0038] Example 1:

[0039] like Figure 1 In the embodiment shown, the acoustic spiral focusing lens is formed by 3D printing. The overall structure is disc-shaped, with a solid cylinder at the center and twelve equal-sized fan-shaped composite structures connected in the circumferential direction. The central angle of each fan-shaped composite structure is 30°. The radius and height of the central solid cylinder are r = 6cm and l = 4cm respectively, and the central angle of each fan-shaped composite structure is 30°. The two-dimensional cross-section of the acoustic spiral focusing lens is shown in FIG. Figure 1 (b) Four asymmetric mode converters are arranged in sequence along the diameter direction, and their shapes and sizes are the same. Each asymmetric mode converter contains four phase-controlled units and a convex waveguide. The phase-controlled units are arranged in sequence along the diameter direction. The convex waveguide is located above the phase-controlled unit and is connected to each other. The frame wall thickness is t = 0.08 cm. Among them, the height and width of the phase-controlled unit are l = 4 cm and r1 = 1.2 cm respectively. The height and width of the large waveguide in the convex waveguide are h1 = 1.5 cm and 4r1 = 4.8 cm respectively. The height and width of the small waveguide are h2 = 1.5 cm and w1 = 2 cm respectively. The material parameters are: the density of the lens structure is 1180 kg / m 3 , longitudinal wave velocity 2720m / s and transverse wave velocity 1460m / s; air density 1.21kg / m 3 The speed of sound is 343 m / s. The wavelength of the incident sound wave is λ = 5 cm.

[0040] Based on the acoustic wave mode conversion theory, in the mode converter, the phase of the two phase-controlled units on the left is selected to be 0, and the phase of the two phase-controlled units on the right is selected to be π. Figure 2Figure 3 shows the spatial distribution of the sound pressure amplitude generated by the mode converter when the sound wave is incident from the top and bottom. It can be seen that when the sound wave is incident from the top, the plane wave can be converted into a first-order sound wave by the mode converter and reach the area below. However, when the sound wave is incident from the bottom, the first-order wave cannot pass through the convex waveguide, thus achieving a good unidirectional sound transmission effect.

[0041] Example 2:

[0042] Figure 3 (a) and 3(b) are the spatial distribution of acoustic energy generated by the acoustic wave incident from the top and bottom respectively through the acoustic spiral focusing lens. It can be seen that when the acoustic wave is incident from the top, the transmitted acoustic energy passes through the lens and is focused on the z = 20 cm area; when the acoustic wave is incident from the bottom, the transmitted acoustic energy cannot pass through the lens. Further, the acoustic energy distribution and phase distribution on the xy cross section (C1 and C2) selected at z = 20 cm. It can be seen that when the acoustic wave is incident from the top, the acoustic energy forms a bright ring in the central area, the transmitted acoustic energy reaches 6 times the energy of the incident acoustic wave, and the phase shows obvious second-order acoustic spiral characteristics; when the acoustic wave is incident from the bottom, the acoustic energy is almost 0, the phase is chaotic, thus forming a good asymmetric second-order acoustic spiral focusing effect.

[0043] Figure 4 Figures (a) and (b) show the spatial distribution of acoustic energy generated by the acoustic spiral focusing lens when incident from the top and bottom, respectively, at different input frequencies. It can be seen that an asymmetric acoustic spiral focusing effect can be achieved in the 6200-7400 Hz range, with an operating bandwidth of up to 1200 Hz, demonstrating broadband characteristics. Furthermore, it can be observed that the focal position of the acoustic spiral focusing lens changes with frequency, offering the advantage of adjustable focus.

[0044] Example 3:

[0045] like Figure 5 In the embodiment shown, the acoustic spiral focusing lens device can achieve acoustic spiral focusing effects of various orders while adjusting the phase distribution of the lens. Figure 5 (a) shows the spatial distribution of acoustic energy when the acoustic spiral focusing lens produces first-order acoustic spiral focusing when the acoustic wave is incident from the top and bottom respectively. It can be seen that when the acoustic wave is incident from the top, the transmitted acoustic energy is still focused in the z=20cm area (cross section C3), but it forms a ring with a smaller radius in the central area, and the phase distribution shows first-order spiral characteristics; when the acoustic wave is incident from the top, the transmitted acoustic energy is almost 0, the phase is chaotic, and a good asymmetric first-order acoustic spiral focusing effect is demonstrated. Figure 5 (a) The spatial distribution of acoustic energy is different, Figure 5(b) shows the third-order acoustic spiral focusing effect produced by the acoustic spiral focusing lens. It can be seen that while maintaining the asymmetric focusing effect, the radius of the ring formed by the acoustic spiral focusing is larger (cross-section C5), and its phase also exhibits third-order acoustic spiral characteristics, indicating that the phase distribution of the lens can be manipulated to achieve acoustic spiral focusing effects of different orders.

[0046] The embodiments described are preferred implementations of the present invention, but the present invention is not limited to the above implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A broadband asymmetric acoustic spiral focusing lens device, characterized in that: The lens structure is disc-shaped as a whole, with a solid cylinder at the center, connected to twelve equal-sized fan-shaped composite structures in the circumferential direction; the radius and height of the central solid cylinder are r and l respectively; the central angle of each fan-shaped composite structure is 30°, and four asymmetric mode converters are arranged in sequence in the diameter direction, and their cross-sections are the same; each asymmetric mode converter contains four phase-controlled units and a convex waveguide, the phase-controlled units are arranged in sequence along the diameter, the convex waveguide is located above the phase-controlled units and is interconnected, and its frame wall thickness is t; among them, the height and width of the phase-controlled unit are l and r1 respectively, the height and width of the large waveguide in the convex waveguide are h1 and 4r1 respectively, and the height and width of the small convex waveguide are h2 and w1 respectively.

2. The broadband asymmetric acoustic spiral focusing lens device according to claim 1, characterized in that: The structural parameters of the acoustic spiral focusing lens are as follows: the radius of the central solid cylinder is 4.5cm≤r≤6.5cm; the height of the phased unit is 3.6cm≤l≤5cm, and the width is 1cm≤r1≤1.2cm; the frame thickness is 0.8cm≤t≤1.2cm; the height of the convex large waveguide is 1.2cm≤h1≤1.8cm; the height of the convex small waveguide is 0.9cm≤h2≤1.1cm, and the width is 1.8cm≤w1≤2.3cm.

3. The broadband asymmetric acoustic spiral focusing lens device according to claim 1, characterized in that: The acoustic spiral focusing lens is prepared by 3D printing technology.

4. The broadband asymmetric acoustic spiral focusing lens device according to claim 1, characterized in that: The acoustic spiral focusing lens is made of one of organic glass, plastic and metal.

5. The broadband asymmetric acoustic spiral focusing lens device according to claim 1, characterized in that: The order n of the acoustic helical beam generated by the acoustic helical focusing lens can be 1, 2, or 3.

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