Underwater acoustic lens based on focusing technology

Abstract

The invention provides an underwater acoustic lens based on a focusing technology, and relates to the field of acoustic lenses. The underwater acoustic lens based on the focusing technology comprises a lens structure and a peripheral baffle arranged outside the lens structure. The lens structure comprises a side face, a first end face and a second end face, the first end face is of a plane structure, the second end face is of a concave curved surface structure, and the side face is connected with the peripheral baffle. Wherein the lens structure is used for focusing underwater sound waves, and the peripheral baffle is used for shielding the sound waves and reducing dissipation of the sound waves from the two sides of the lens structure. The sound wave energy intensity after focusing of the sound lens is high, and various operations such as underwater detection and communication are facilitated. Moreover, the acoustic lens provided by the invention meets the requirements of light weight and miniaturization, can reduce the complexity and cost of the whole system, and simplifies the installation and maintenance.

Description

Technical Field

[0001] The present application relates to the field of acoustic lenses, and in particular to an underwater acoustic lens based on focusing technology. Background Art

[0002] Sound waves are mechanical waves that are generated by the vibration of objects and propagate through various media. Underwater ultrasonic detection is a technology that uses the propagation characteristics of ultrasonic waves in water to locate underwater targets, identify shapes, detect structures, and analyze medium characteristics. As an important technology for underwater detection, it has been increasingly used, but the underwater environment is relatively complex, and water also has a certain absorption and consumption effect on sound waves, which will affect the detection effect. Summary of the invention

[0003] In view of this, an embodiment of the present application provides an underwater acoustic lens based on focusing technology, comprising a lens structure and a peripheral baffle plate arranged outside the lens structure; the lens structure comprises a side surface and a first end surface and a second end surface arranged opposite to each other, the first end surface is a plane structure, the second end surface is a concave curved surface structure, and the side surface is connected to the peripheral baffle plate;

[0004] The lens structure is used to focus underwater sound waves, and the outer baffle is used to shield the sound waves and reduce the sound waves from escaping from both sides of the lens structure.

[0005] The underwater acoustic lens according to the embodiment of the present application may also have the following additional technical features:

[0006] In the above technical solution, optionally, the acoustic impedance of the material of the lens structure is 0.5 to 2 times the acoustic impedance of water.

[0007] In any of the above technical solutions, optionally, the sound speed of the material of the lens structure is greater than 1.4 times the sound speed of water, or less than 0.7 times the sound speed of water; or, the sound speed of the lens structure material is c≥2100m / s, or c≤1071m / s.

[0008] In any of the above technical solutions, optionally, the material of the outer baffle is a non-sound absorbing or non-noise-reducing material; the acoustic impedance of the material of the outer baffle is not less than 10 7 kg·m -2 ·s -1 .

[0009] In any of the above technical solutions, optionally, the diameter of the underwater acoustic lens is D, the width of the outer baffle is r1, and the radius of the first end face of the lens structure is r2, then D=2r1+2r2.

[0010] In any of the above technical solutions, optionally, the width r1 of the outer baffle is not less than λ / 3, where λ is the wavelength of underwater sound waves, λ=1500 / f, and f is the frequency of the sound waves.

[0011] In any of the above technical solutions, optionally, the height of the outer baffle is equal to the maximum height of the second end surface.

[0012] In any of the above technical solutions, optionally, the cross section of the second end surface is a U-shaped curve, the U-shaped curve includes 2n+1 fitting points, the lateral distance between two adjacent fitting points is equal, and n is greater than or equal to 1;

[0013] The distance between the position of the middle fitting point on the U-shaped curve and the position of the focusing point is greater than 5 times the wavelength of the underwater sound wave.

[0014] In any of the above technical solutions, optionally, the height of the i-th fitting point is h i , the phase of the i-th fitting point is in, p and q are constants.

[0015] In any of the above technical solutions, optionally, after the position of the focusing point is adjusted, focusing is achieved by adjusting the heights of other fitting points on the U-shaped curve except the middle fitting point.

[0016] In an embodiment of the present application, an underwater acoustic lens includes a lens structure and a peripheral baffle. The lens structure includes a side surface and a first end surface and a second end surface that are relatively arranged. The first end surface is a planar structure, which can be understood as the bottom surface of the lens structure. The second end surface is a concave curved surface structure, which can be understood as the upper surface of the lens structure. The side surface is tightly connected to the peripheral baffle. Among them, the lens structure is used to realize the function of underwater sound wave focusing, and the peripheral baffle is used to block the sound waves and prevent the sound wave energy from escaping from both sides of the lens structure. The sound wave energy intensity after focusing by the acoustic lens of the present application is relatively high, which is conducive to various operations such as underwater detection and communication. In addition, the acoustic lens of the present application meets the requirements of lightweight and miniaturization, which can reduce the complexity and cost of the entire system and simplify installation and maintenance.

[0017] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0019] Figure 1 A schematic diagram of a two-dimensional structure of an underwater acoustic lens based on focusing technology according to an embodiment of the present application;

[0020] Figure 2 A schematic diagram of the three-dimensional structure of an underwater acoustic lens based on focusing technology according to an embodiment of the present application;

[0021] Figure 3 This is a simulation diagram of the sound pressure after focusing a plane incident wave with a sound pressure of 1 Pa at a focal position (0,75) using an underwater acoustic lens in a standard water environment with a sound wave frequency of f=50000 Hz using COMSOL software in the embodiment of the present application;

[0022] Figure 4 This is a simulation diagram of the sound pressure level after focusing a plane incident wave with a sound pressure of 1 Pa at a focal position (0,75) using an underwater acoustic lens in a standard water environment with a sound wave frequency of f=50000 Hz using COMSOL software in the embodiment of the present application;

[0023] Figure 5 This is a simulation diagram of the sound pressure after focusing a plane incident wave with a sound pressure of 1 Pa at the focal position (0, 88) using an underwater acoustic lens in a standard water environment with a sound wave frequency of f = 50000 Hz using COMSOL software in the embodiment of the present application;

[0024] Figure 6 This is a simulation diagram of the sound pressure level after focusing a plane incident wave with a sound pressure of 1 Pa at the focal position (0, 88) using an underwater acoustic lens in a standard water environment with a sound wave frequency of f = 50000 Hz using COMSOL software in the embodiment of the present application;

[0025] Figure 7 This is a simulation diagram of the sound pressure after focusing a plane incident wave with a sound pressure of 1 Pa at the focal position (15, 75) using an underwater acoustic lens in a standard water environment with a sound wave frequency of f = 50000 Hz using COMSOL software in the embodiment of the present application;

[0026] Figure 8 This embodiment of the present application uses COMSOL software to simulate the sound pressure level of a plane incident wave with a sound pressure of 1 Pa after focusing at the focal position (15, 75) using an underwater acoustic lens in a standard water environment with a sound wave frequency of f=50000 Hz. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0028] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0029] The underwater acoustic lens based on focusing technology provided by the embodiment of the present application is described in detail below through specific embodiments and their application scenarios in conjunction with the accompanying drawings.

[0030] An acoustic lens is a device that uses the principle of sound wave refraction to focus sound waves. It is similar to an optical lens in optics and can concentrate the energy of sound waves within a specified range, thereby obtaining a very high sound pressure within a certain area. In this way, some weak sound wave signals can also be detected, significantly changing the sound propagation effect, improving the detection effect and detection depth. It has broad research prospects in various underwater detection fields such as deep-sea exploration, national defense security, emergency rescue, underwater building inspection and maintenance, etc.

[0031] The embodiment of the present application provides an underwater acoustic lens based on focusing technology, such as Figure 1 and Figure 2 As shown, the underwater acoustic lens comprises:

[0032] The lens structure and the peripheral baffle, the lens structure includes a side surface and a first end surface and a second end surface that are arranged opposite to each other, the first end surface is a plane structure, which can be understood as the bottom surface of the lens structure, the second end surface is a concave curved surface structure, which can be understood as the upper surface of the lens structure, and the side surface is tightly connected to the peripheral baffle. Among them, the lens structure is used to realize the function of underwater sound wave focusing, and the peripheral baffle is used to block the sound wave to prevent the sound wave energy from escaping from both sides of the lens structure.

[0033] The sound wave can be an ultrasonic wave (f≥20000 Hz, f is the sound wave frequency) or an audible sound wave (f is 20-20000 Hz). However, since the wavelength of underwater sound waves is more than 4 times that of sound waves in the air at the same frequency, too low a frequency will result in a lens structure that is too large, and underwater detection is generally performed using ultrasonic waves without noise influence. Therefore, the lower limit frequency of the underwater acoustic lens focusing sound waves in this application is 20000 Hz.

[0034] The embodiments of the present application provide a simple, efficient, low-cost, and good focusing acoustic lens. Compared with the acoustic lens made by the metasurface method in the related art, the structural design of the acoustic lens of the present application can ensure that there is no energy loss caused by acoustic wave blocking after the plane wave is incident on the lens structure. Therefore, the energy intensity of the acoustic wave after focusing is high, which is conducive to various operations such as underwater detection and communication. In addition, compared with the underwater acoustic focusing system with large volume and large number of unit structures in the related art, the acoustic lens of the present application meets the requirements of lightweight and miniaturization, which can reduce the complexity and cost of the entire system and simplify installation and maintenance. In addition, the acoustic lens of the present application has a curved surface with a fitting curve, which reduces the manufacturing cost and difficulty compared with the jagged structure of the Fresnel acoustic lens in the related art.

[0035] In one embodiment of the present application, the material of the lens structure is selected to satisfy the requirement that the difference between its acoustic impedance and the acoustic impedance of water is small, otherwise it will cause serious attenuation of acoustic energy. The acoustic impedance of the material of the lens structure is in the range of 0.5 to 2 times the acoustic impedance of water (that is, 0.75×10 6 kg·m -2 ·s -1 Up to 3×10 6 kg·m -2 ·s -1 ) is more reasonable.

[0036] In one embodiment of the present application, the sound velocity c of the material of the lens structure must not be too close to the sound velocity of water, otherwise it will lead to low phase modulation efficiency, resulting in the lens structure being too large. In the present application, the sound velocity of the lens structure material is greater than 1.4 times the sound velocity of water, or less than 0.7 times the sound velocity of water, or the sound velocity of the lens structure material is c ≥ 2100 m / s, or c ≤ 1071 m / s, and the sound velocity of water can be 1500 m / s. Since there are very few solid materials with a sound velocity c lower than 1071 m / s, preferably, the sound velocity c of the lens structure material is ≥ 2100 m / s.

[0037] In addition, the material of the lens structure must be able to have sufficient physical and chemical stability in an aqueous environment and remain free of deformation, damage, and deterioration for a long time.

[0038] In one embodiment of the present application, the material of the peripheral baffle plate must be selected to have a large difference between its acoustic impedance and the acoustic impedance of water, so as to play a role similar to a hard sound field wall. In the present application, the acoustic impedance of the material of the peripheral baffle plate is not less than 10 7 kg·m -2 ·s -1 , and the material of the outer baffle has no sound absorption, no sound elimination and other effects.

[0039] In addition, the material of the outer baffle must be able to have sufficient physical and chemical stability in the water environment and remain free of deformation, damage and deterioration for a long time.

[0040] In one embodiment of the present application, Figure 1 As shown, the diameter of the underwater acoustic lens is D, the width of the peripheral baffle is r1, and the radius of the first end face of the lens structure is r2, then D = 2r1 + 2r2. The peripheral baffle fits the side of the lens structure to prevent the sound wave energy from escaping from both sides of the lens structure.

[0041] In one embodiment of the present application, the width r1 of the outer baffle is not less than λ / 3, where λ is the wavelength of sound waves in water, λ=1500 / f, and f is the frequency of the sound waves.

[0042] In one embodiment of the present application, the first end surface of the lens structure is circular, and the second end surface of the lens structure is a concave curved surface structure, that is, the lens structure is a curved surface with a circular bottom surface and a height that increases continuously from the center to the outside. Figure 1 As shown, in the two-dimensional front view, the lens structure is represented as a left-right symmetrical structure with three straight sides and one side being a U-shaped curve, that is, the cross-section of the second end face of the lens structure is a U-shaped curve.

[0043] The U-shaped curve is fitted by 2n+1 fitting points, where n is greater than or equal to 1. The middle fitting point is a0, and the left side includes fitting points a1, a2, ......., a n , and to the right also includes fitting points a1, a2, ..., a n a0, a1, a2, ......., a n The heights are h0, h1, h2, ..., h n The middle fitting point a0 is the center point of the lens structure, and the height h0 of the middle fitting point a0 is the height of the center point of the lens structure. The height of the peripheral baffle is equal to the maximum height of the second end face, that is, the height of the peripheral baffle is the height of both sides of the lens structure, which is also h n .

[0044] In one embodiment of the present application, the height of the fitting point on the U-shaped curve of the lens structure is selected to meet the requirement that when a plane wave incident from the first end face propagates to the focal point through the lens structure and the water environment, the phase of the plane wave propagating from each incident point to the focal point is consistent, that is, the height of the i-th fitting point is h i , the phase of the i-th fitting point is in, p and q are constants, and λ' is the wavelength of the sound wave in the lens structure. For example, at the height h0 of the lens structure, its phase At the height h1 of the lens structure, the phase And so on, through reasonable h0, h1, h2, ..., h n to ensure

[0045] In one embodiment of the present application, the coordinates (x, y) of the focus point cannot be too close to the underwater acoustic lens, otherwise it is difficult to achieve focusing. In the present application, the distance between the focus point and the middle fitting point of the U-shaped curve of the lens structure (that is, the point corresponding to the U-shaped curve directly below) is not less than 5 times the wavelength of the underwater sound wave, that is, 5λ.

[0046] In one embodiment of the present application, after determining the focus point, 2n+1 fitting points are determined on the second end face of the lens structure, and the lateral distances between the fitting points can be the same, that is, the lateral distance from a0 to a1 can be equal to the distance from a1 to a2, and so on. From the middle fitting point a0 to the right, the heights of the fitting points h0, h1, h2, ..., h n to ensure The left and right sides of the middle fitting point of the second end face are symmetrical, so after the right side is calculated, the left side and the right side can be kept symmetrical. Finally, a fitting curve is generated based on the fitting points to complete the design of the underwater acoustic lens.

[0047] The design of the underwater acoustic lens can adjust the focus point up and down and left and right according to the actual needs of the focus position, without changing the diameter D of the acoustic lens and the center height h0 of the lens structure, and only the height of other fitting points needs to be adjusted to complete the focusing. When the focus point deviates from the central axis of the underwater acoustic lens, the lateral distance of the deviation is less than or equal to the bottom radius r2 of the lens structure, so as to avoid the problem of more speckles and prevent the focusing effect from being greatly affected.

[0048] In one embodiment of the present application, when the focus point deviates from the central axis of the underwater acoustic lens, the underwater acoustic lens will be asymmetrical. At this time, the heights of all 2n+1 fitting points need to be calculated according to the method of the above embodiment, and a fitting curve is drawn to complete the design of the underwater acoustic lens. The present application can adjust the focus point up, down, left, and right according to the actual needs of the focus position, allowing the focus point to deviate from the center line of the acoustic lens, which increases the adjustability and flexibility for practical applications.

[0049] In one embodiment of the present application, the material of the lens structure is polystyrene, which has a density of about 1050 kg / m 3 , the speed of sound is about 2350m / s, and its acoustic impedance is about 2.5×10 6 kg·m -2 ·s -1 The material has good physical and chemical stability in water environment, and is not prone to deformation, rust and other problems, meeting the material requirements of the lens structure. The material of the outer baffle is stainless steel, and its acoustic impedance reaches about 4.6×10 7 kg·m -2 ·s -1 Moreover, the material has good physical and chemical stability in water environment, is not prone to deformation, rust and other problems, and meets the material requirements of the outer baffle.

[0050] Select the sound wave frequency f = 50000 Hz, then the wavelength of the sound wave propagating in water λ = 3 cm, the wavelength propagating in the underwater sound lens λ' = 4.7 cm. The bottom radius of the lens structure r2 = 30 cm, the width of the outer baffle r1 = 1 cm, and the diameter of the underwater sound lens D = 2r1 + 2r2 = 62 cm.

[0051] Since the overall size of the underwater acoustic lens is not large, the center height of the lens structure can be h0 = 5 cm, n = 16, and the number of fitting points is 33. Construct an xy two-dimensional coordinate system, with the center point of the bottom of the lens structure as the origin (0,0), and the focus coordinates as (0,75). Through phase calculation, the height of each fitting point can be calculated and a fitting curve can be drawn.

[0052] The COMSOL simulation software was used to draw a two-dimensional plane diagram of the underwater acoustic lens according to the dimensions mentioned above, and a plane wave with a sound pressure value of 1 Pa and a vertically upward direction was applied to the bottom. Figure 3 This is a simulation diagram of the sound pressure after being focused by an underwater acoustic lens. Figure 4 This is a simulation diagram of the sound pressure level after being focused by the underwater acoustic lens.

[0053] The underwater acoustic lens design method can adjust the focus point according to the actual needs of the focus position, without changing the diameter D of the acoustic lens and the center height h0 of the lens structure. Focusing can be completed by adjusting the height of other fitting points. For example, when the focus point coordinates are (0,88), focusing at the preset point can be completed by calculating the heights of the remaining fitting points. The COMSOL sound pressure simulation diagram and sound pressure level simulation diagram of the focus point coordinates (0,88) are shown as follows: Figure 5 and Figure 6 When the focal point coordinates are (15,75), the heights of the remaining fitting points are calculated and the sound pressure simulation diagram and sound pressure level simulation diagram are simulated by COMSOL as shown in Figure 1. Figure 7 and Figure 8 shown.

[0054] Judging from the overall simulation research results, the sound pressure and sound pressure level at the focus are much higher than those at other positions, and the focal spot is smaller; the speckle phenomenon is not obvious at other positions, and the focusing effect of the entire sound focusing structure is relatively ideal.

[0055] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0056] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. An underwater acoustic lens based on focusing technology, characterized in that: It comprises a lens structure and a peripheral baffle plate arranged outside the lens structure; the lens structure comprises a side surface and a first end surface and a second end surface arranged opposite to each other, the first end surface is a plane structure, the second end surface is a concave curved surface structure, and the side surface is connected to the peripheral baffle plate; The lens structure is used to focus underwater sound waves, and the outer baffle is used to shield the sound waves and reduce the sound waves from escaping from both sides of the lens structure.

2. The underwater acoustic lens according to claim 1, characterized in that: The acoustic impedance of the material of the lens structure is 0.5 to 2 times the acoustic impedance of water.

3. The underwater acoustic lens according to claim 1, characterized in that: The sound velocity of the material of the lens structure is greater than 1.4 times the sound velocity of water, or less than 0.7 times the sound velocity of water; or, The sound velocity of the material of the lens structure is c≥2100 m / s, or c≤1071 m / s.

4. The underwater acoustic lens according to claim 1, characterized in that: The material of the outer baffle is a non-sound absorbing or non-sound absorbing material; The acoustic impedance of the material of the peripheral baffle is not less than 10 7 kg·m -2 ·s -1 .

5. The underwater acoustic lens according to claim 1, characterized in that: The diameter of the underwater acoustic lens is D, the width of the outer baffle is r1, and the radius of the first end surface of the lens structure is r2, then D=2r1+2r2.

6. The underwater acoustic lens according to claim 1, characterized in that: The width r1 of the outer baffle is not less than λ / 3, where λ is the wavelength of underwater sound waves, λ=1500 / f, and f is the frequency of the sound waves.

7. The underwater acoustic lens according to claim 1, characterized in that: The height of the peripheral baffle is equal to the maximum height of the second end surface.

8. The underwater acoustic lens according to claim 1, characterized in that: The cross section of the second end surface is a U-shaped curve, the U-shaped curve includes 2n+1 fitting points, the lateral distance between two adjacent fitting points is equal, and n is greater than or equal to 1; The distance between the position of the focusing focus and the position of the middle fitting point on the U-shaped curve is greater than or equal to 5 times the wavelength of the underwater sound wave.

9. The underwater acoustic lens according to claim 8, characterized in that: The height of the i-th fitting point is h i , the phase of the i-th fitting point is Where, i=0,1,......,n, p and q are constants, and λ' is the wavelength of the sound wave in the lens structure.

10. The underwater acoustic lens according to claim 8, characterized in that: After the position of the focusing point is adjusted, focusing is achieved by adjusting the heights of other fitting points on the U-shaped curve except the middle fitting point.

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