Plane active focusing air coupling ultrasonic transducer

Abstract

The invention relates to a planar active focusing air coupling ultrasonic transducer, and belongs to the technical field of piezoelectric ultrasonic transducers, and the planar active focusing air coupling ultrasonic transducer is characterized in that a piezoelectric plate and a matching layer are arranged in a shell; the rear cover plate covers the tail end of the shell; the interface is arranged on the shell; a plurality of concentric annular structure electrodes are arranged on the first surface of the piezoelectric plate; the width of each concentric ring in the plurality of concentric ring structure electrodes is gradually increased from outside to inside; a second surface of the piezoelectric plate is provided with a second electrode; and the piezoelectric plate is connected with the interface through leads led out from the plurality of concentric ring-shaped structure electrodes and the whole-surface electrode. According to the plane active focusing air coupling ultrasonic transducer provided by the invention, active focusing of a plane acoustic beam is realized by changing the electrode structure of the piezoelectric plate and arranging a plurality of concentric annular electrode structures on the single surface of the piezoelectric plate, and the plane acoustic impedance matching layer with uniform thickness is matched; and the sensitivity of the focusing air coupling transducer is improved under the condition that the transverse resolution of the transducer is not influenced.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric ultrasonic transducers, and in particular to a planar actively focused air-coupled ultrasonic transducer. Background Art

[0002] Air-coupled ultrasonic transducers have shown great application potential in the fields of biomedicine and non-destructive testing due to their non-contact and completely non-destructive characteristics. With the development of detection technology and medical treatment, high-precision and complex ultrasonic testing has put forward higher requirements on the performance of air-coupled transducers. Ultrasonic focusing technology enables air-coupled transducers to produce extremely narrow high-intensity sound beams, greatly improving the resolution and sensitivity of air-coupled transducers. It has a wide range of applications in ultrasonic imaging, structural health monitoring, medical ultrasound and other fields.

[0003] Traditional focused air-coupled transducers mostly use passive focusing methods to improve the lateral resolution of the transducer, such as acoustic concave lenses. Among them, the focusing method of the acoustic concave lens destroys the thickness condition of acoustic impedance matching and has a negative impact on the sensitivity of the air-coupled transducer; the focusing method of the Fresnel zone plate has a large background noise and low sound pressure at the focus due to the blocking and diffraction effects of the baffle. It can be seen that the passive focusing method of the air-coupled transducer is always accompanied by an adverse effect on the sensitivity of the transducer, that is, it will reduce the sensitivity of the transducer. Summary of the invention

[0004] In view of this, it is necessary to provide a planar actively focused air-coupled ultrasonic transducer to solve the problem of how to improve the sensitivity of the transducer.

[0005] In order to solve the above problems, the present invention provides a planar actively focused air-coupled ultrasonic transducer, comprising: Piezoelectric sheets, matching layers, housings, back covers and interfaces; The piezoelectric sheet and the matching layer are both arranged in the housing; The rear cover plate covers the end of the shell; the interface is arranged on the shell; A plurality of concentric ring structure electrodes are arranged on the first surface of the piezoelectric sheet; the width of each concentric ring of the plurality of concentric ring structure electrodes increases from the outside to the inside; The second surface of the piezoelectric sheet is provided with a whole surface electrode; the first surface and the second surface are two opposite surfaces; The piezoelectric sheet is connected to the interface through the wires led out from the plurality of concentric ring structure electrodes and the whole surface electrodes.

[0006] In a possible implementation, the radius of each concentric ring in the plurality of concentric ring structure electrodes is as follows:

[0007] in, r n Indicates n Radius, n is a positive integer, F represents the focal length, λ Represents the wavelength of sound waves in a medium.

[0008] In a possible implementation manner, the first surface of the piezoelectric sheet and the matching layer are bonded together using epoxy resin glue.

[0009] In a possible implementation, the plurality of concentric ring structure electrodes are prepared by using a screen printing technique on the piezoelectric sheet.

[0010] In a possible implementation, the plurality of concentric ring structure electrodes are silver electrodes.

[0011] In a possible implementation, the diameters of the piezoelectric sheet and the matching layer are the same; The piezoelectric sheet and the matching layer are coaxially arranged.

[0012] In a possible implementation, the thickness of the piezoelectric film is half the wavelength corresponding to the center frequency of the ultrasonic signal.

[0013] In a possible implementation, the material of the piezoelectric sheet is a 1-3 type piezoelectric fiber composite material.

[0014] In a possible implementation manner, the thickness of the matching layer is one quarter of the wavelength corresponding to the center frequency of the ultrasonic signal.

[0015] In a possible implementation, the matching layer is made of a hollow glass microsphere / epoxy resin composite material.

[0016] The beneficial effects of the present invention are as follows: the planar actively focused air-coupled ultrasonic transducer provided by the present invention comprises a plurality of concentric ring structure electrodes through the first electrode on the first surface of the piezoelectric sheet, and the second electrode on the second surface of the piezoelectric sheet is a whole-surface electrode, and the electrode structure of the piezoelectric sheet is changed, and a plurality of concentric ring electrode structures are arranged on a single surface of the piezoelectric sheet, and the width of each concentric ring in the plurality of concentric ring structure electrodes increases successively from the outside to the inside, and active focusing of the planar sound beam can be achieved by applying the same excitation signal to the concentric ring electrodes, and in combination with a planar acoustic impedance matching layer of uniform thickness, the sensitivity of the focused air-coupled transducer can be improved without affecting the lateral resolution of the transducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A cross-sectional view of an embodiment of a planar actively focused air-coupled ultrasonic transducer provided by the present invention; Figure 2 A schematic flow chart of an embodiment of a method for preparing a piezoelectric sheet provided by the present invention; Figure 3 A schematic structural diagram of an embodiment of a 1-3 type piezoelectric fiber composite material provided by the present invention having a single surface with multiple concentric ring electrode structures; Figure 4 This is an experimental test diagram of the sound field distribution of an embodiment of the planar actively focused air-coupled ultrasonic transducer provided by the present invention.

[0019] Reference numerals: 1: piezoelectric sheet; 2: matching layer; 3: housing; 4: back cover; 5: interface. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0021] In the description of the embodiments of the present invention, unless otherwise specified, "multiple" means two or more than two. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" may mean: A exists alone, A and B exist at the same time, and B exists alone.

[0022] The descriptions of "first", "second", etc. involved in the embodiments of the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the technical features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0023] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0024] Figure 1 A cross-sectional view of an embodiment of a planar actively focused air-coupled ultrasonic transducer provided by the present invention, as shown in FIG. Figure 1 As shown, the planar actively focused air-coupled ultrasonic transducer comprises: Piezoelectric sheet 1, matching layer 2, housing 3, back cover 4 and interface 5; The piezoelectric sheet 1 and the matching layer 2 are both arranged in the housing 3; The rear cover plate 4 covers the end of the housing 3; the interface 5 is arranged on the housing 3; A plurality of concentric ring structure electrodes are arranged on the first surface of the piezoelectric sheet 1; the width of each concentric ring of the plurality of concentric ring structure electrodes increases from the outside to the inside; The second surface of the piezoelectric sheet 1 is provided with a whole surface electrode; the first surface and the second surface are two opposite surfaces; The piezoelectric sheet 1 is connected to the interface 5 through the wires led out from the plurality of concentric ring structure electrodes and the whole surface electrodes.

[0025] like Figure 1 As shown, the piezoelectric sheets and matching layers are arranged in sequence in the housing along the ultrasonic signal emission direction.

[0026] The rear cover plate covers the end of the shell, and the interface is fixed to the shell through the rear cover plate, and the interface is used for externally connecting an ultrasonic power supply.

[0027] The electrodes arranged on the first surface of the piezoelectric sheet are a plurality of concentric ring structure electrodes, wherein the width of each concentric ring in the plurality of concentric ring structure electrodes increases sequentially from the outside to the inside.

[0028] The radius size parameters of the concentric ring structures are given by the initial parameters of the Fresnel zone plate structure after simulation optimization. Multiple concentric ring structure electrodes can be made into multiple concentric ring structures with gradually decreasing widths by screen printing technology.

[0029] The electrodes arranged on the second surface of the piezoelectric sheet are full-surface electrodes. The first surface and the second surface are two opposite surfaces of the piezoelectric sheet.

[0030] The piezoelectric piece is connected to the interface through wires respectively led out from a plurality of concentric ring structure electrodes and the whole surface electrodes.

[0031] The planar actively focused air-coupled ultrasonic transducer provided by an embodiment of the present invention comprises a first electrode on the first surface of the piezoelectric sheet including a plurality of concentric ring structure electrodes, and a second electrode on the second surface of the piezoelectric sheet is a whole-surface electrode. The electrode structure of the piezoelectric sheet is changed, and a plurality of concentric ring electrode structures are arranged on a single surface of the piezoelectric sheet, and the width of each concentric ring in the plurality of concentric ring structure electrodes increases successively from the outside to the inside. By applying the same excitation signal to the concentric ring electrodes, active focusing of the planar sound beam can be achieved, and in combination with a planar acoustic impedance matching layer of uniform thickness, the sensitivity of the focused air-coupled transducer can be improved without affecting the lateral resolution of the transducer.

[0032] In some embodiments of the present invention, the first surface of the piezoelectric sheet 1 and the matching layer 2 are bonded with epoxy resin glue.

[0033] The first surface of the piezoelectric sheet is a surface provided with a plurality of concentric ring structure electrodes, and the first surface of the piezoelectric sheet and the matching layer are bonded with epoxy resin glue.

[0034] In some embodiments of the present invention, the radius of each concentric ring in the plurality of concentric ring structure electrodes is as follows:

[0035] in, r n Indicates n Radius, n is a positive integer, F represents the focal length, λ Indicates the wavelength of the sound wave in the medium. In some embodiments of the present invention, the plurality of concentric ring structure electrodes are prepared on the piezoelectric sheet 1 by using screen printing technology.

[0036] In some embodiments of the present invention, the plurality of concentric ring structure electrodes are silver electrodes.

[0037] The multiple concentric ring structure electrodes on the piezoelectric plate can be made of conductive silver paste using screen printing technology to form multiple concentric ring structures with gradually decreasing widths. The radius size parameters of the concentric ring structures are given by the Fresnel zone plate structure after simulation optimization.

[0038] Figure 2 A schematic flow chart of an embodiment of a method for preparing a piezoelectric sheet provided by the present invention is shown in FIG. Figure 2 As shown in (a), the piezoelectric sheet is made of 1-3 type piezoelectric fiber composite material; Figure 2 As shown in (b) in the figure, the upper electrode of the piezoelectric film is removed; Figure 2 As shown in (c), multiple concentric ring structures with gradually decreasing widths are made of conductive silver paste; Figure 2As shown in (d), the single-sided electrode of the obtained piezoelectric sheet is made into multiple concentric ring structures with gradually decreasing widths using screen printing technology, and the other side electrode remains unchanged and is a full-surface electrode.

[0039] For example, Figure 3 A schematic diagram of an embodiment of a 1-3 type piezoelectric fiber composite material having a single surface with multiple concentric ring electrode structures provided by the present invention. Figure 3 As shown, n is 9, and 9 radii can be calculated in sequence according to the calculation formula of the radius of the concentric rings mentioned above.

[0040] The planar actively focused air-coupled ultrasonic transducer provided in the embodiment of the present invention realizes active focusing of the planar piezoelectric air-coupled ultrasonic transducer by optimizing the design of a single-sided multiple concentric annular electrode structure, thereby improving the sensitivity of the focused air-coupled piezoelectric ultrasonic transducer.

[0041] In some embodiments of the present invention, the piezoelectric sheet 1 and the matching layer 2 are coaxially arranged.

[0042] The piezoelectric sheet and the matching layer are coaxially arranged thin discs, which can be bonded to each other using epoxy resin glue.

[0043] In some embodiments of the present invention, the thickness of the piezoelectric sheet 1 is half the wavelength corresponding to the center frequency of the ultrasonic signal.

[0044] In some embodiments of the present invention, the material of the piezoelectric sheet 1 is 1-3 type piezoelectric fiber composite material.

[0045] The piezoelectric sheet is made of 1-3 type piezoelectric fiber composite material, which is composed of evenly arranged piezoelectric columns and epoxy resin filling. The thickness of the piezoelectric sheet is half the wavelength corresponding to the center frequency of the ultrasonic signal.

[0046] In this embodiment, the piezoelectric sheet is preferably a 1-3 type piezoelectric fiber composite material piezoelectric sheet. The principle of selecting the 1-3 type piezoelectric fiber composite material is to minimize the influence of the lateral vibration mode of the piezoelectric material on the sound field distribution.

[0047] In some embodiments of the present invention, the thickness of the matching layer 2 is one quarter of the wavelength corresponding to the center frequency of the ultrasonic signal.

[0048] In some embodiments of the present invention, the matching layer 2 is made of hollow glass microspheres / epoxy resin composite material.

[0049] The thickness of the matching layer is one quarter wavelength corresponding to the center frequency of the ultrasonic signal. The material of the matching layer is a hollow glass microbead / epoxy resin composite material, which can improve the matching between the piezoelectric material and the air medium and improve the sensitivity.

[0050] The present invention proposes a design method of a planar active focusing air-coupled transducer (PAF-ACUT). The core idea is to make multiple concentric ring-shaped single-sided electrode patterns on a bulk planar thin disc piezoelectric film, apply a same excitation signal, and realize active focusing of the sound beam.

[0051] The initial structural parameters of the multiple concentric annular electrode patterns designed by the present invention are given by referring to the design method of FZP. Further, the structural parameters of the multiple concentric annular electrode patterns are optimized by the finite element simulation method, with the sensitivity of the transducer as the optimization target, while ensuring that the focal length and lateral resolution do not change much. After determining the structural parameters, a plurality of concentric annular single-sided electrode patterns are made on the 1-3 type piezoelectric fiber composite piezoelectric sheet using screen printing technology, and a 1 / 4 wavelength uniform thickness acoustic impedance matching layer is made using a high-performance hollow glass microbead / epoxy resin composite material, and finally a planar active focusing air-coupled piezoelectric ultrasonic transducer is developed.

[0052] That is, the present invention proposes a planar active focusing air-coupled ultrasonic transducer, which has the characteristics of non-contact and no coupling agent, and focuses the plane wave beam at the same time. Compared with the traditional focused air-coupled transducer, the focused air-coupled transducer has higher sensitivity under the condition of the same or similar lateral resolution. The present invention mainly realizes the active focusing of the planar sound beam by changing the electrode structure of the piezoelectric sheet, arranging multiple concentric annular electrode structures on a single surface of the piezoelectric sheet, and cooperates with a uniform planar acoustic impedance matching layer to improve the sensitivity of the focused air-coupled transducer without affecting the lateral resolution of the transducer.

[0053] An embodiment of a planar actively focused air-coupled piezoelectric ultrasonic transducer with a plurality of concentric ring electrode structures having a center frequency of 400 kHz is given below: The piezoelectric plate of the planar active focusing air-coupled transducer is made of 1-3 type piezoelectric fiber composite material with an acoustic resistance of 11.9 MRayl, a thickness of 4 mm and a diameter of 26 mm.

[0054] The thickness of the piezoelectric film is calculated according to formula (1), which is half the wavelength corresponding to the center frequency of the ultrasonic signal.

[0055] (1) in, h 1 represents the thickness of the piezoelectric film, c 1 represents the longitudinal wave velocity of the piezoelectric film, f represents the center frequency of the ultrasonic signal, l 1 represents the wavelength of the center frequency of the ultrasonic signal.

[0056] like Figure 2As shown, screen printing technology is preferably used on the piezoelectric sheet, and a plurality of concentric annular electrode structures are preferably prepared using conductive silver paste, wherein the initial parameters corresponding to each radius are preferably calculated according to the Fresnel zone plate formula, which is given by formula (2).

[0057] (2) in r n Indicates n Radius, n is a positive integer, F is the focal length, l 1 is the wavelength of the sound wave in the medium.

[0058] The matching layer material is preferably a hollow glass microsphere / epoxy resin composite material with a density of 350 kg / m³, a longitudinal wave speed of 2100 m / s, a diameter of 26 mm, the same as the diameter of the piezoelectric material, and a thickness of 1.3 mm. The thickness of the matching layer is taken as a quarter wavelength corresponding to the center frequency of the ultrasonic signal and is calculated according to formula (3).

[0059] (3) in, h 2 represents the thickness of the matching layer, c 2 represents the longitudinal wave velocity of the matching layer, f represents the center frequency of the ultrasonic signal, l 2 represents the wavelength of the center frequency of the ultrasonic signal.

[0060] The optimal acoustic impedance of the matching layer is calculated according to formula (4).

[0061] (4) in, Z w represents the acoustic impedance of the matching layer, Z p represents the acoustic resistance of the piezoelectric patch, Z r represents the acoustic resistance of the load medium, preferably the acoustic resistance of air.

[0062] The acoustic field distribution of a planar active focusing air-coupled piezoelectric ultrasonic transducer using a plurality of concentric ring electrode structures provided by the present invention can be experimentally tested by the following method: The focused air-coupled transducer provided by the present invention is placed on a desktop clamping device, and the coaxial alignment is maintained. The same excitation signal is applied to all concentric annular electrodes. The method of measuring the sound field with a hydrophone is used as a transmitting transducer, and a non-focused plane air-coupled transducer with the same center frequency + a metal baffle with a hole in the middle is used as a receiving transducer. The center of the baffle is a small hole with a diameter of 2 mm. The maximum sound pressure at each point in the experimental test space is measured to obtain the sound field distribution.

[0063] For example, Figure 4 This is a test diagram of the acoustic field distribution experiment of an embodiment of the planar active focusing air-coupled ultrasonic transducer provided by the present invention. The acoustic field distribution of the transducer is as follows Figure 4 shown.

[0064] The planar actively focused air-coupled ultrasonic transducer provided by the present invention can be used for non-contact diagnosis and treatment of human epidermal tissue. The focused air-coupled transducer provided by the present invention can produce appropriate deformation on a tiny area of ​​human epidermal tissue in a non-contact manner, helping the system to perform real-time image processing and non-invasive imaging of epidermal tissue.

[0065] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware (such as a processor, a controller, etc.) through a computer program, and the computer program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0066] The planar actively focused air-coupled ultrasonic transducer provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A planar actively focused air-coupled ultrasonic transducer, characterized in that: include: Piezoelectric sheets, matching layers, housings, back covers and interfaces; The piezoelectric sheet and the matching layer are both arranged in the housing; The rear cover plate covers the end of the housing; The interface is arranged on the housing; A plurality of concentric annular structure electrodes are arranged on the first surface of the piezoelectric sheet; The width of each concentric ring in the plurality of concentric ring structure electrodes increases from the outside to the inside; The second surface of the piezoelectric sheet is provided with a whole surface electrode; the first surface and the second surface are two opposite surfaces; The piezoelectric sheet is connected to the interface through the wires led out from the plurality of concentric ring structure electrodes and the whole surface electrodes.

2. The planar actively focused air-coupled ultrasonic transducer according to claim 1, characterized in that: The radius of the concentric rings in the multiple concentric ring structure electrodes is as follows: in, r n Indicates n Radius, n is a positive integer, F represents the focal length, λ Represents the wavelength of sound waves in a medium.

3. The planar actively focused air-coupled ultrasonic transducer according to claim 1, characterized in that: The first surface of the piezoelectric sheet and the matching layer are bonded with epoxy resin glue.

4. The planar actively focused air-coupled ultrasonic transducer according to claim 1, characterized in that: The plurality of concentric ring structure electrodes are prepared by using screen printing technology on the piezoelectric sheet.

5. The planar actively focused air-coupled ultrasonic transducer according to claim 1, characterized in that: The multiple concentric ring structure electrodes are silver electrodes.

6. The planar actively focused air-coupled ultrasonic transducer according to claim 1, characterized in that: The diameters of the piezoelectric sheet and the matching layer are the same; The piezoelectric sheet and the matching layer are coaxially arranged.

7. The planar actively focused air-coupled ultrasonic transducer according to claim 1, characterized in that: The thickness of the piezoelectric film is half the wavelength corresponding to the center frequency of the ultrasonic signal.

8. The planar actively focused air-coupled ultrasonic transducer according to claim 1, characterized in that: The material of the piezoelectric sheet is 1-3 type piezoelectric fiber composite material.

9. The planar actively focused air-coupled ultrasonic transducer according to claim 1, characterized in that: The thickness of the matching layer is one quarter of the wavelength corresponding to the center frequency of the ultrasonic signal.

10. The planar actively focused air-coupled ultrasonic transducer according to claim 1, characterized in that: The matching layer is made of hollow glass microsphere / epoxy resin composite material.

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