Ultrasonic transduction module, ultrasonic transducer, ultrasonic test device and terminal

Abstract

Provided in the present application are an ultrasonic transduction module, an ultrasonic transducer, an ultrasonic test device and a terminal. In the ultrasonic transduction module, an acoustic boundary between a substrate layer and a piezoelectric layer divides the ultrasonic transduction module into two sub-resonators, the two sub-resonators respectively creating 1 / 2 wavelength resonance and 1 / 4 wavelength resonance at the same resonant frequency, and a resonator constituted by the entire ultrasonic transduction module creating resonance at another resonant frequency. Therefore, the ultrasonic transduction module provided in the present application has two resonant frequencies and, compared with modules in the prior art each of which has only one resonant frequency, can be applied to environments having different frequency demands.

Description

Ultrasonic transduction module, ultrasonic transducer, ultrasonic detection device and terminal

[0001] The present application claims priority from the Chinese patent application No. 202411359684.4 filed on September 26, 2024, and entitled "Ultrasonic transduction module, ultrasonic transducer, ultrasonic detection device and terminal", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] Embodiments of the present application relate to the field of ultrasonic detection, and in particular to an ultrasonic transduction module, an ultrasonic transducer, an ultrasonic detection device and a terminal. BACKGROUND

[0003] An acoustic transducer is a device that realizes mutual conversion between electric energy and acoustic energy (e.g., mechanical energy). An acoustic transducer based on the piezoelectric principle is called a piezoelectric transducer, which can realize conversion from electric energy to mechanical energy through the inverse piezoelectric effect, and can realize conversion from mechanical energy to electric energy through the positive piezoelectric effect. If the piezoelectric transducer works in the thickness-stretch vibration mode and the working frequency of the piezoelectric transducer is the resonance frequency, the piezoelectric transducer is called a piezoelectric transducer in the thickness resonance mode.

[0004] The resonance frequency of a conventional piezoelectric transducer in the thickness resonance mode is related to the thickness and material of the piezoelectric transducer. After the thickness size and material of the piezoelectric transducer are determined, the resonance frequency of the piezoelectric transducer is also determined. In order to obtain greater sensitivity, the piezoelectric transducer generally works at the resonance frequency, that is, the working frequency of the piezoelectric transducer is the resonance frequency. That is, the piezoelectric transducer works at a single frequency.

[0005] However, in actual acoustic application scenarios, the higher the frequency of the acoustic wave, the higher the resolution of the acoustic wave; the lower the frequency of the acoustic wave, the stronger the penetration ability of the acoustic wave. Since different scenarios have different requirements for resolution and penetration ability, the working frequency of the piezoelectric transducer also has different requirements in different scenarios. Therefore, the conventional piezoelectric transducer in the thickness resonance mode is limited in application scenarios due to the single working frequency. SUMMARY

[0006] The present application provides an ultrasonic transduction module, an ultrasonic transducer, an ultrasonic detection device and a terminal, which are used to provide at least two resonance frequencies, so that the same piezoelectric transducer can be applied to scenarios with different frequency requirements.

[0007] In a first aspect, the present application provides an ultrasonic transduction module, comprising: a substrate layer, a first electrode layer, a piezoelectric layer, a second electrode layer and at least one protective layer arranged in sequence.

[0008] The sum of the first parameters of the stacked layers in the first sub-module is a / 4, a is a positive odd number, the first sub-module comprises a piezoelectric layer, a second electrode layer and at least one protective layer; the sum of the first parameters of the stacked layers in the second sub-module is b / 2, b is a positive integer, the second sub-module comprises a substrate layer and a first electrode layer; wherein the first parameter of any stacked layer in the ultrasonic transducing module is the ratio of the thickness of any stacked layer to the wavelength of the first sound wave in any stacked layer when the first sound wave is transmitted in the stacked layer, and the frequency of the first sound wave is the resonance frequency of the first sub-module and the second sub-module;

[0009] The sum of the second parameters of the substrate layer, the first electrode layer, the piezoelectric layer, the second electrode layer and the at least one protective layer is c / 2, c is a positive integer; the second parameter of any stacked layer in the ultrasonic transducing module is the ratio of the thickness of any stacked layer to the wavelength of the second sound wave in any stacked layer when the second sound wave is transmitted in the stacked layer, and the frequency of the second sound wave is the resonance frequency of the ultrasonic transducing module.

[0010] In the aspect, the sum of the first parameters of the stacked layers in the first sub-module is a / 4, a is a positive odd number, i.e. the first sub-module constitutes a 1 / 4 wavelength resonator, the sum of the first parameters of the stacked layers in the second sub-module is b / 2, b is a positive integer, i.e. the second sub-module constitutes a 1 / 2 wavelength resonator, and the first parameter is the ratio of the thickness of any stacked layer to the wavelength of the first sound wave in any stacked layer when the first sound wave is transmitted in the stacked layer, and the frequency of the first sound wave is the resonance frequency of the first sub-module and the second sub-module (i.e. the first resonance frequency), thus the aforementioned two sub-modules achieve the same frequency resonance at the first resonance frequency. In addition, the sum of the second parameters of the substrate layer, the first electrode layer, the piezoelectric layer, the second electrode layer and the at least one protective layer is c / 2, c is a positive integer, i.e. the entire ultrasonic transducing module constitutes a 1 / 2 wavelength resonator, and the second parameter is the ratio of the thickness of any stacked layer to the wavelength of the second sound wave in any stacked layer when the second sound wave is transmitted in the stacked layer, and the frequency of the second sound wave is the resonance frequency of the ultrasonic transducing module (i.e. the second resonance frequency), thus the entire ultrasonic transducing module resonates at the second resonance frequency. Therefore, the ultrasonic transducing module provided in the aspect has two resonance frequencies, compared with the module having only one resonance frequency in the prior art, the ultrasonic transducing module provided in the aspect can be applied to scenarios with different frequency requirements.

[0011] In a possible implementation, the ratio of the second resonance frequency to the first resonance frequency is d, wherein 0.5 < d < 0.75, the first resonance frequency is the resonance frequency of the first sub-module and the second sub-module, and the second resonance frequency is the resonance frequency of the ultrasonic transducing module.

[0012] In a possible implementation, the acoustic pressure reflectivity of the acoustic boundary between the piezoelectric layer and the substrate layer is e, wherein 20% < |e| < 80%.

[0013] In the embodiment, the acoustic boundary between the piezoelectric layer and the substrate layer has a non-low acoustic pressure reflectivity, which is conducive to dividing the ultrasonic transducer module into two sub-resonators through the acoustic boundary, and conducive to realizing the same frequency resonance of the two sub-resonators.

[0014] In a possible implementation, the ratio of the acoustic impedance of the piezoelectric layer to the acoustic impedance of the substrate layer is less than 0.5. It can be understood that the acoustic impedance of the piezoelectric layer is much smaller than the acoustic impedance of the substrate layer, and therefore, the acoustic boundary from the piezoelectric layer to the substrate layer is a hard boundary, and the acoustic boundary from the substrate layer to the piezoelectric layer is a soft boundary.

[0015] In a possible implementation, the ratio of the acoustic impedance of the substrate layer to the acoustic impedance of the first adjacent medium is greater than 2, and the first adjacent medium is the adjacent medium of the substrate layer away from the piezoelectric layer. It can be understood that the acoustic impedance of the substrate layer is much greater than the acoustic impedance of the first adjacent medium, and therefore, the acoustic boundary from the substrate layer to the first adjacent medium is a soft boundary.

[0016] In a possible implementation, the at least one protective layer includes a first protective layer and a second protective layer, the first protective layer is connected to the side of the second electrode layer away from the piezoelectric layer, the second protective layer is connected to the side of the first protective layer away from the second electrode layer, and the material of the first protective layer is different from the material of the second protective layer.

[0017] In a possible implementation, the ratio of the acoustic impedance of the second protective layer to the acoustic impedance of the second adjacent medium is greater than 2, and the second adjacent medium is the adjacent medium of the second protective layer away from the first protective layer.

[0018] In a possible implementation, the material of the first protective layer includes glue, and the material of the second protective layer includes metal.

[0019] In a possible implementation, the at least one protective layer is one protective layer, the protective layer is connected to the side of the second electrode layer away from the piezoelectric layer, and the ratio of the acoustic impedance of the protective layer to the acoustic impedance of the second adjacent medium is greater than 2, and the second adjacent medium is the adjacent medium of the protective layer away from the second electrode layer.

[0020] In a possible implementation, the second electrode layer includes at least two electrode blocks, each electrode block and the first electrode layer form a capacitor, the at least one capacitor, the inductor connected to the capacitor, and the at least one switching circuit are used to form an oscillation circuit, and the number of electrode blocks connected to the oscillation circuit is controlled by the switch.

[0021] In this embodiment, the number of electrode blocks connected to the circuit is controlled by a switching circuit, thereby controlling the capacitance value of the connected circuit. This allows the resonant frequency of the oscillation circuit to not only reach the desired resonant frequency but also switch between different resonant frequencies as the switch is turned on and off. This improves the flexibility of the frequency of the excitation signal applied to the ultrasonic transducer module.

[0022] In one possible implementation, the second electrode layer includes a first electrode block and a second electrode block, the areas of the first electrode block and the second electrode block satisfying the following formula:

[0023] S1 / (S2+S1)=(f2 / f1) 2 Where S1 is the area of ​​the first electrode block, S2 is the area of ​​the second electrode block, f1 is the first resonant frequency, and f2 is the second resonant frequency.

[0024] In one possible implementation, the second electrode layer includes a first electrode block and a second electrode block, the areas of the first electrode block and the second electrode block satisfying the following formula:

[0025] S1 / S2=(f2 / f1) 2 Where S1 is the area of ​​the first electrode block, S2 is the area of ​​the second electrode block, f1 is the first resonant frequency, and f2 is the second resonant frequency.

[0026] In one possible implementation, the substrate is made of any one of glass, silicon, or polymer.

[0027] In one possible implementation, the piezoelectric layer is made of an organic polymer or an inorganic piezoelectric material.

[0028] In one possible implementation, the second electrode layer is made of any one of graphite, nickel, tungsten, aluminum, copper, silver, gold, or conductive particles.

[0029] In one possible implementation, the operating frequency range of the ultrasonic transducer module includes the frequency range between the first resonant frequency and the second resonant frequency.

[0030] In one possible implementation, the ultrasonic transducer module operates in the range of 5 MHz to 25 MHz.

[0031] Secondly, this application provides an ultrasonic transducer module, characterized in that it comprises: a substrate layer, a first electrode layer, a piezoelectric layer, a second electrode layer and at least one protective layer arranged sequentially; the piezoelectric layer, the second electrode layer and at least one protective layer constitute a first sub-module, and the substrate layer and the first electrode layer constitute a second sub-module;

[0032] The sum of the first parameters of the layers included in the first sub-module is i / 2, i is a positive integer, the first sub-module includes a piezoelectric layer, a second electrode layer and at least one protective layer; the sum of the first parameters of the layers included in the second sub-module is j / 4, j is a positive odd number, the second sub-module includes a substrate layer and a first electrode layer; wherein the first parameter of any layer in the ultrasonic transducing module is the ratio of the thickness of any layer to the wavelength of the first sound wave in any layer when the first sound wave is transmitted in the layer, and the frequency of the first sound wave is the resonance frequency of the first sub-module and the second sub-module;

[0033] The sum of the second parameters of the substrate layer, the first electrode layer, the piezoelectric layer, the second electrode layer and the at least one protective layer is k / 2, k is a positive integer; the second parameter of any layer in the ultrasonic transducing module is the ratio of the thickness of any layer to the wavelength of the second sound wave in any layer when the second sound wave is transmitted in the layer, and the frequency of the second sound wave is the resonance frequency of the ultrasonic transducing module.

[0034] In the aspect, the sum of the first parameters of the layers included in the first sub-module is i / 2, i is a positive integer, i.e. the first sub-module constitutes a 1 / 2 wavelength resonator, the sum of the first parameters of the layers included in the second sub-module is j / 4, j is a positive odd number, i.e. the second sub-module constitutes a 1 / 4 wavelength resonator, and the first parameter is the ratio of the thickness of any layer to the wavelength of the first sound wave in any layer when the first sound wave is transmitted in the layer, and the frequency of the first sound wave is the resonance frequency of the first sub-module and the second sub-module (i.e. the first resonance frequency), thus the two sub-modules resonate at the same frequency at the first resonance frequency. In addition, the sum of the second parameters of the substrate layer, the first electrode layer, the piezoelectric layer, the second electrode layer and the at least one protective layer is k / 2, k is a positive integer, i.e. the entire ultrasonic transducing module constitutes a 1 / 2 wavelength resonator, and the second parameter is the ratio of the thickness of any layer to the wavelength of the second sound wave in any layer when the second sound wave is transmitted in the layer, and the frequency of the second sound wave is the resonance frequency of the ultrasonic transducing module (i.e. the second resonance frequency), thus the entire ultrasonic transducing module resonates at the second resonance frequency. Therefore, the ultrasonic transducing module provided in the aspect has two resonance frequencies, compared with the module having only one resonance frequency in the prior art, the ultrasonic transducing module provided in the aspect can be applied to scenarios with different frequency requirements.

[0035] In a possible implementation, the ratio of the second resonance frequency to the first resonance frequency is d, wherein 0.5 < d < 0.75, the first resonance frequency is the resonance frequency of the first sub-module and the second sub-module, and the second resonance frequency is the resonance frequency of the ultrasonic transducing module.

[0036] In a possible implementation, the acoustic pressure reflectivity of the acoustic boundary between the piezoelectric layer and the substrate layer is e, wherein 20% < |e| < 80%.

[0037] In a possible implementation, a ratio of the acoustic impedance of the piezoelectric layer to the acoustic impedance of the substrate layer is greater than 2.

[0038] In a possible implementation, a ratio of the acoustic impedance of the substrate layer to the acoustic impedance of the first adjacent medium is greater than 2, the first adjacent medium being an adjacent medium of the substrate layer away from the piezoelectric layer.

[0039] In a possible implementation, the at least one protective layer includes a first protective layer and a second protective layer, the first protective layer being connected to the second electrode layer away from the piezoelectric layer, the second protective layer being connected to the first protective layer away from the second electrode layer, and the first protective layer and the second protective layer being made of different materials.

[0040] In a possible implementation, a ratio of the acoustic impedance of the second protective layer to the acoustic impedance of the second adjacent medium is greater than 2, the second adjacent medium being an adjacent medium of the second protective layer away from the first protective layer.

[0041] In a possible implementation, the material of the first protective layer includes glue, and the material of the second protective layer includes metal.

[0042] In a possible implementation, the at least one protective layer is one protective layer, the protective layer being connected to the second electrode layer away from the piezoelectric layer, and a ratio of the acoustic impedance of the protective layer to the acoustic impedance of the second adjacent medium is greater than 2, the second adjacent medium being an adjacent medium of the protective layer away from the second electrode layer.

[0043] In a possible implementation, the second electrode layer includes at least two electrode blocks, each electrode block and the first electrode layer forming a capacitor, the at least one capacitor, an inductor connected to the capacitor, and at least one switching circuit being used to form an oscillation circuit, and the number of electrode blocks connected to the oscillation circuit is controlled by the switching.

[0044] In a possible implementation, the second electrode layer includes a first electrode block and a second electrode block, and areas of the first electrode block and the second electrode block satisfy the following formula:

[0045] S1 / (S2+S1)=(f2 / f1) 2 ; where S1 is the area of the first electrode block, S2 is the area of the second electrode block, f1 is the first resonant frequency, and f2 is the second resonant frequency.

[0046] In a possible implementation, the second electrode layer includes a first electrode block and a second electrode block, and areas of the first electrode block and the second electrode block satisfy the following formula:

[0047] S1 / S2=(f2 / f1) 2; wherein S1 is an area of the first electrode block, S2 is an area of the second electrode block, f1 is the first resonant frequency, and f2 is the second resonant frequency.

[0048] In a possible implementation, the substrate layer is made of any one of glass, silicon, and a polymer material.

[0049] In a possible implementation, the piezoelectric layer is made of an organic polymer material or an inorganic piezoelectric material.

[0050] In a possible implementation, the second electrode layer is made of any one of graphite, nickel, tungsten, aluminum, copper, silver, gold, and a conductive particle.

[0051] In a possible implementation, the working frequency range of the ultrasonic transduction module includes a frequency range between the first resonant frequency and the second resonant frequency.

[0052] In a possible implementation, the working frequency range of the ultrasonic transduction module is 5 megahertz to 25 megahertz.

[0053] It should be noted that the specific implementations and advantages of the present aspect are similar to those of the first aspect, and details can be referred to the specific implementations and advantages of the first aspect, which will not be described herein.

[0054] In a third aspect, the present application provides an ultrasonic transducer, including: a controller and the ultrasonic transduction module according to any one of the implementations of the first aspect; or, a controller and the ultrasonic transduction module according to any one of the implementations of the second aspect; wherein the first electrode layer and the second electrode layer in the ultrasonic transduction module are electrically connected to the controller. Specifically, the controller is configured to provide a first electrical signal to the ultrasonic transduction module; and the ultrasonic transduction module is configured to output a transmitting acoustic wave based on the first electrical signal.

[0055] In a possible implementation, the ultrasonic transduction module is further configured to receive a reflected acoustic wave, and provide a second electrical signal to the controller based on the reflected acoustic wave; and the controller is configured to receive the second electrical signal.

[0056] In a possible implementation, the ultrasonic transducer further includes a switching circuit and an inductor; the second electrode layer in the ultrasonic transduction module includes a first electrode block and a second electrode block, the first electrode block and the first electrode layer form a first capacitor, the second electrode block and the first electrode layer form a second capacitor, the second capacitor is connected in series with the switching circuit, the second capacitor and the switching circuit are connected in parallel with the first capacitor, and the inductor is connected in series with the parallel-connected first capacitor and second capacitor.

[0057] The controller is specifically configured to control the switch circuit to be open, the first capacitor and the inductor are connected in series, and the first capacitor and the inductor form a first oscillation circuit, and a working frequency of the first oscillation circuit is located in a first frequency band; or the controller is specifically configured to control the switch circuit to be closed, the first capacitor and the second capacitor are connected in parallel, and the first capacitor, the second capacitor and the inductor are connected in series, the first capacitor, the second capacitor and the inductor form a second oscillation circuit, and a working frequency of the second oscillation circuit is located in a second frequency band.

[0058] In the embodiment, when the high-frequency driving is performed, the switch is open, and only the first electrode block works; when the low-frequency driving is performed, the switch is closed, and the first electrode block and the second electrode block work together. By adjusting the capacitance in the oscillation circuit through different driving areas, the resonance condition can be met at different resonance frequencies.

[0059] In a possible implementation, the first frequency band includes a first resonance frequency, and the second frequency band includes a second resonance frequency, and the first capacitor and a third capacitor are connected in parallel;

[0060] The capacitance value of the first capacitor, the capacitance value of the second capacitor and the capacitance value of the third capacitor satisfy the following formula: (C1+C3) / (C2+C1+C3)=(f2 / f1) 2 ;

[0061] Wherein, C1 is the capacitance value of the first capacitor, C2 is the capacitance value of the second capacitor, C3 is the capacitance value of the third capacitor, f1 is the first resonance frequency, and f2 is the second resonance frequency.

[0062] In the embodiment, the third capacitor (i.e. the external capacitor and / or the parasitic capacitor) is introduced, the influence of the parasitic capacitor on the circuit is considered, and the matching accuracy of the frequency can be improved. In addition, the external capacitor is added, the adjustment range of the capacitance value of the oscillation circuit can be expanded, and the frequency range matched by the oscillation circuit can be expanded.

[0063] In a possible implementation, the ultrasonic transducer further includes a first switch circuit, a second switch circuit and an inductor; the second electrode layer in the ultrasonic transducer module includes a first electrode block and a second electrode block, the first electrode block and the first electrode layer form a first capacitor, the second electrode block and the first electrode layer form a second capacitor, the first capacitor is connected in series with the first switch circuit, the second capacitor is connected in series with the second switch circuit, the first capacitor and the first switch circuit connected in series and the second capacitor and the second switch circuit connected in series are connected in parallel, and the inductor is connected in series with the first capacitor and the second capacitor connected in parallel;

[0064] The controller is specifically configured to control the first switch circuit to be closed and the second switch circuit to be open, the first capacitor and the inductor are connected in series, the first capacitor and the inductor form a third oscillation circuit, and a working frequency of the third oscillation circuit is located in a third frequency band; or,

[0065] The controller is specifically configured to control the second switch circuit to be closed and the first switch circuit to be opened, the second capacitor and the inductor are connected in series, and the second capacitor and the inductor form a fourth oscillation circuit, and the working frequency of the fourth oscillation circuit is located in a fourth frequency band.

[0066] In the embodiment, the first electrode block and the second electrode block are respectively controlled by the two independent switch circuits (i.e., the first switch circuit and the second switch circuit) to determine whether the first electrode block and the second electrode block are connected to the circuit, so that the size of the capacitance value of the circuit to which the first electrode block and the second electrode block are connected can be flexibly controlled, and the resonant frequency of the oscillation circuit can not only reach the expected resonant frequency, but also be switched at different resonant frequencies according to the on-off state of the switch, thereby improving the flexibility of the frequency of the excitation signal applied to the ultrasonic transducer module.

[0067] In a possible implementation, the third frequency band includes a first resonant frequency, and the fourth frequency band includes a second resonant frequency, and the first capacitor and the fourth capacitor are connected in parallel.

[0068] The capacitance value of the first capacitor, the capacitance value of the second capacitor, and the capacitance value of the fourth capacitor satisfy the following formula: (C1+C4) / (C2+C4)=(f2 / f1) 2 ;

[0069] wherein C1 is the capacitance value of the first capacitor, C2 is the capacitance value of the second capacitor, C4 is the capacitance value of the fourth capacitor, f1 is the first resonant frequency, and f2 is the second resonant frequency.

[0070] In the embodiment, the fourth capacitor (i.e., the external capacitor and / or the parasitic capacitor) is introduced, the influence of the parasitic capacitor on the circuit is considered, and the matching accuracy of the frequency is improved. In addition, the external capacitor is added, the adjustment range of the capacitance value of the oscillation circuit is expanded, and the frequency range matched by the oscillation circuit is expanded.

[0071] In a fourth aspect, the present application provides an ultrasonic detection device, which comprises: a penetration layer and the ultrasonic transducer introduced in any one of the embodiments of the third aspect, the penetration layer covering the ultrasonic transducer module; and the transmitted sound wave and the reflected sound wave pass through the penetration layer.

[0072] In a possible implementation, the penetration layer is a display screen, a glass layer, or a metal layer.

[0073] In a possible implementation, the ultrasonic detection device further comprises a matching layer, the matching layer is used to connect the penetration layer and the ultrasonic transducer module, the transmitted sound wave passes through the ultrasonic transducer module, the matching layer, and the penetration layer in sequence, and the reflected sound wave passes through the penetration layer, the matching layer, and the ultrasonic transducer module in sequence.

[0074] In a fifth aspect, the present application provides a terminal, comprising: an image processing module and the ultrasonic detection device of any one of the preceding fourth aspect; the image processing module is configured to generate an image based on the second electrical signal, the second electrical signal being a signal generated by the reflected sound wave received by the ultrasonic detection device. BRIEF DESCRIPTION OF DRAWINGS

[0075] FIG. 1 is an example diagram of an ultrasonic transducer in the prior art;

[0076] FIG. 2A is an example diagram of an ultrasonic transducer applied to a fingerprint detection scenario;

[0077] FIG. 2B is an example diagram of an ultrasonic transducer applied to a medical flaw detection scenario;

[0078] FIG. 3 is a schematic diagram of an embodiment of an ultrasonic transducing module provided by the present application;

[0079] FIG. 4A is a schematic diagram of another embodiment of an ultrasonic transducing module provided by the present application;

[0080] FIG. 4B is a schematic diagram of another embodiment of an ultrasonic transducing module provided by the present application;

[0081] FIG. 5A is an example diagram of an ultrasonic transducing module provided by the present application;

[0082] FIG. 5B is another example diagram of an ultrasonic transducing module provided by the present application;

[0083] FIG. 5C is another example diagram of an ultrasonic transducing module provided by the present application;

[0084] FIG. 5D is another example diagram of an ultrasonic transducing module provided by the present application;

[0085] FIG. 6 is a simulation example diagram of the ultrasonic transducing module shown in FIG. 5A of the present application;

[0086] FIG. 7A is a schematic diagram of an equivalent circuit of a first electrode block and a second electrode block provided by the present application;

[0087] FIG. 7B is another schematic diagram of an equivalent circuit of a first electrode block and a second electrode block provided by the present application;

[0088] FIG. 7C is another schematic diagram of an equivalent circuit of a first electrode block and a second electrode block provided by the present application;

[0089] FIG. 7D is another schematic diagram of an equivalent circuit of a first electrode block and a second electrode block provided by the present application;

[0090] FIG. 8 is an example diagram of an arrangement of a first electrode block and a second electrode block provided by the present application;

[0091] Fig. 9 is a schematic diagram of an embodiment of an ultrasound transducer provided by the present application;

[0092] Fig. 10 is a schematic diagram of an embodiment of an ultrasound detection device provided by the present application. DETAILED DESCRIPTION

[0093] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments of the present application.

[0094] The terms "first", "second", "third", "fourth" and the like (if any) in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the terms used in this way can be interchanged under appropriate circumstances, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0095] It should be understood that the term "and / or" herein is only a description of the association relationship between the associated objects, which means that there can be three relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, B exists alone, where A and B can be single or multiple. In addition, the character " / " herein generally represents an "or" relationship between the associated objects. In addition, "at least one of the following" or similar expressions herein are used to represent any combination of the listed items; for example, at least one of A, B and (or) C can represent the following six cases: A exists alone, B exists alone, C exists alone, A and B exist together, B and C exist together, A and C exist together, A, B and C exist together, where A, B and C can be single or multiple.

[0096] For ease of understanding, the professional terms involved in the present application will be briefly introduced as follows:

[0097] Specific acoustic impedance: also referred to as acoustic impedance or acoustic specific impedance, represents the ratio of the acoustic pressure of a wave front of a sound wave in a medium to the vibration velocity of a particle on the front. Generally, the specific acoustic impedance is a complex number, the real part of the specific acoustic impedance is referred to as acoustic resistance, and the imaginary part of the specific acoustic impedance is referred to as acoustic reactance. The specific acoustic impedance R can also be represented by the product of the propagation velocity v of a sound wave in a material and the density p of the material, i.e., specific acoustic impedance R = density p x sound velocity v. The unit of the specific acoustic impedance R is mega Rayl (MRayl) or kilogram per square meter per second (kg m -2 · s). Wherein, 1 MRayl = 10 6 kg m -2 · s. In the embodiments of the present application, the term “acoustic impedance” is used for introduction. It should be noted that, in the case of a determined material, the density of the material is fixed, the sound velocity of a sound wave propagating in the material is determined, and thus the acoustic impedance is also determined. Generally, different materials have different acoustic impedances.

[0098] Resonance: also referred to as resonance, refers to the phenomenon that, under the action of a periodic external force, the amplitude of an oscillation system sharply increases when the frequency of the external force is the same as or very close to the natural oscillation frequency of the system. The frequency at which resonance occurs is referred to as resonance frequency. When resonance occurs, the amplitude of a sound wave is enhanced.

[0099] Resonance frequency of a transducer: refers to the frequency at which the transducer reaches the resonance condition, i.e., the frequency at which the mechanical amplitude of the transducer reaches the maximum. When the transducer works at the resonance frequency, the transducer can perform energy conversion with the highest efficiency. Without considering mechanical loss, the resonance frequency of the transducer is the frequency at which the impedance of the piezoelectric transducer is the smallest and the transmission power is the largest. The resonance frequency is related to the physical parameters (e.g., thickness, material, temperature, boundary conditions, etc.) of the piezoelectric transducer, and the resonance frequency of the piezoelectric transducer can be adjusted by adjusting the physical parameters of the transducer. When the physical parameters (e.g., thickness, material, temperature, boundary conditions, etc.) of the piezoelectric transducer are determined, the resonance frequency of the piezoelectric transducer is also determined.

[0100] Operating frequency of a transducer: refers to the frequency of an excitation signal transmitted by a driving circuit to a piezoelectric transducer; or the frequency of an external mechanical wave (e.g., a sound wave) received by a piezoelectric transducer. In practical applications, when the operating frequency matches the resonance frequency, the transducer can obtain the best energy conversion efficiency and performance. For example, when the operating frequency of the transducer is equal to the resonance frequency of the transducer, the transducer is said to work at the resonance frequency, at which the mechanical amplitude of the transducer is the largest and the transmission sensitivity is the largest.

[0101] Sensitivity: refers to the change of the output signal of the transducer under the unit input signal, which can also be regarded as the efficiency of the transducer in converting energy. For example, the higher the sensitivity, the greater the change of the output signal under the unit input signal, and the higher the conversion efficiency. Alternatively, the sensitivity can be divided into transmitting sensitivity and receiving sensitivity. Among them, the transmitting sensitivity refers to the sound pressure size that the transducer can emit under the unit voltage drive, and the unit is Pa per V (Pa / V); the receiving sensitivity refers to the voltage size that the transducer can generate under the unit sound pressure, and the unit is V per Pa (V / Pa). The sensitivity mentioned in the embodiments of the present application refers to the comprehensive transmitting and receiving sensitivity, which refers to the comprehensive sensitivity considering the transmitting sensitivity and the receiving sensitivity. The value of the sensitivity is generally greater than 0 and less than 1.

[0102] Sound transmission coefficient: refers to the ratio of the transmitted sound energy flux to the incident sound energy flux through the interface (for example, the interface of medium 1 to medium 2 with different acoustic characteristics) under given frequency and conditions. The larger the sound transmission coefficient, the less the attenuation of the sound wave in the transmission process of penetrating the interface. Generally, the sound transmission coefficient is related to the material (or acoustic impedance) of the medium on both sides of the interface. The closer the acoustic impedance of the medium on both sides of the interface, the less the attenuation of the sound wave in the transmission process of penetrating the interface, and the larger the sound transmission coefficient.

[0103] Sound reflection coefficient: refers to the ratio of the reflected sound energy flux to the incident sound energy flux through the interface (for example, the interface of medium 1 to medium 2 with different acoustic characteristics) under given frequency and conditions. The larger the sound reflection coefficient, the greater the energy of the sound wave reflected back from the interface. Generally, the sound reflection coefficient is related to the material (or acoustic impedance) of the medium on both sides of the interface. The greater the difference in acoustic impedance of the medium on both sides of the interface, the greater the reflection of the sound wave at the interface, and the larger the sound reflection coefficient.

[0104] It should be noted that the sound transmission coefficient and the sound reflection coefficient are inversely related. Those skilled in the art can determine the sound reflection coefficient of a certain interface when the sound transmission coefficient of the interface is known. The sound reflection coefficient in the embodiments of the present application can be a sound pressure reflection coefficient, a sound intensity reflection coefficient or a sound energy reflection coefficient, which is not limited here. The sound transmission coefficient in the embodiments of the present application can be a sound pressure transmission coefficient, a sound intensity transmission coefficient or a sound energy transmission coefficient, which is not limited here. For example, if the sound wave propagates from medium 1 (acoustic impedance R1) to medium 2 (acoustic impedance R2), the sound pressure reflection coefficient can be represented as (R2-R1) / (R2+R1), the sound energy reflection coefficient can be represented as [(R2-R1) / (R2+R1)] 2 , and the sound energy transmission coefficient can be represented as 1-[(R2-R1) / (R2+R1)]2 .

[0105] Acoustic reflective boundary: refers to when sound waves are incident from medium 1 to medium 2 with different acoustic characteristics, due to the difference in acoustic impedance of the two media, part of the sound waves returns to medium 1, at this time, the boundary between medium 1 and medium 2 is called acoustic reflective boundary. Alternatively, if the acoustic impedance of the aforementioned two media is large, resulting in a large part of the energy of the incident sound waves returning to medium 1, at this time, the boundary between medium 1 and medium 2 is called strong acoustic reflective boundary. Generally, the interface with a sound pressure reflection coefficient of 20% can be called a strong acoustic reflective interface. If the sound pressure reflection coefficients of two acoustic reflective boundaries are large (for example, the two acoustic boundaries are strong acoustic reflective boundaries), and the acoustic impedance of the stack between the two acoustic reflective boundaries is similar, the stack between the two acoustic reflective boundaries can be equivalent to a resonator in the thickness direction of the stack. Acoustic reflective boundary includes acoustic hard boundary and acoustic soft boundary. In the case of sound wave propagation from medium 1 (acoustic impedance R1) to medium 2 (acoustic impedance R2), if R2 is greater than R1, medium 2 is more "hard" in acoustic properties than medium 1, and the boundary between medium 1 and medium 2 is called acoustic hard boundary; if R2 is less than R1, medium 2 is more "soft" in acoustic properties than medium 1, and the boundary between medium 1 and medium 2 is called acoustic soft boundary. The acoustic soft and hard boundary determines the thickness of the resonator at the resonant frequency. For example, if both reflective boundaries of the resonator are acoustic hard boundaries or acoustic soft boundaries, the thickness of the resonator needs to be close to an integer multiple of (1 / 2)λ (i.e. an even multiple of (1 / 4)λ); if the two reflective boundaries of the resonator are acoustic hard boundary and acoustic soft boundary respectively, the thickness of the resonator needs to be close to an odd multiple of (1 / 4)λ. Wherein, λ is the wavelength of the sound wave, λ=v / f, v is the sound speed of the medium in the thickness direction of the resonator, and f is the frequency of the sound wave in the thickness direction of the resonator. In the case where the material and working scenario (for example, temperature, pressure, frequency, etc.) are determined, the sound speed of the sound wave propagating in the material is determined. It should be noted that the sound speed mentioned in the present application can be the longitudinal wave speed, the transverse wave speed or the guided wave speed, the specific selection depends on the form of sound wave transmission under actual working conditions, which is not limited in the present application.

[0106] Parasitic capacitance: also known as stray capacitance, refers to the capacitance generated in the circuit due to the mutual capacitance phenomenon between the wires or between the elements. Parasitic capacitance is not intentionally added when designing the circuit, but is caused by factors such as the structure and material of electronic components.

[0107] In order to facilitate the understanding of the ultrasonic transduction module and the ultrasonic transducer provided in the present application, the working principle of the traditional ultrasonic transduction module and the ultrasonic transducer will be briefly introduced as follows:

[0108] FIG. 1 is an example diagram of an ultrasonic transducer in the prior art. As shown in FIG. 1, the conventional ultrasonic transducer includes an ultrasonic transducing module and a transceiver circuit module. The ultrasonic transducing module mainly includes a substrate layer, and a first electrode layer (also referred to as a lower electrode layer), a piezoelectric layer and a second electrode layer (also referred to as an upper electrode layer) which are sequentially stacked on the substrate layer. The substrate layer is used to support the entire ultrasonic transducing module. The piezoelectric layer is the core element of the conversion between electrical energy and mechanical energy, and can realize the conversion from electrical energy to mechanical energy through the inverse piezoelectric effect, and can realize the conversion from mechanical energy to electrical energy through the positive piezoelectric effect. The second electrode layer and the first electrode layer are connected with the transceiver circuit module, and are used to transmit electrical signals or receive electrical signals converted by the piezoelectric layer. For example, in the case that the transceiver circuit module transmits electrical signals, the first electrode layer and the second electrode layer are loaded with the electrical signals, and the piezoelectric layer located between the second electrode layer and the first electrode layer can vibrate under the action of the electrical signals to emit sound waves outward. For another example, when the piezoelectric layer receives sound waves from the outside (such as reflected sound waves corresponding to the aforementioned transmitted sound waves), the piezoelectric layer can also generate electrical signals based on the sound waves, and the electrical signals can be transmitted to the transceiver circuit module through the first electrode layer and the second electrode layer. The first electrode layer can be provided as a pixelated electrode structure, so that the reflected sound wave signals are received in a pixelated manner. At this time, the thickness of the first electrode layer is set to a relatively thin thickness (for example, a nanometer order thickness), so as to reduce the influence on the flatness of the adjacent piezoelectric layer. In addition, the second electrode layer of the conventional ultrasonic transducing module can also be provided with a protective layer for protecting the second electrode layer from being oxidized and corroded, and providing a certain mechanical buffering effect. In the case that the thickness and material of the stack are determined, the conventional ultrasonic transducer has only one resonant frequency. In order to obtain higher sensitivity, the frequency of the electrical signal (i.e. the excitation signal) applied to the conventional ultrasonic transducer needs to be close to the resonant frequency. However, in actual acoustic application scenarios, the higher the frequency of the sound wave, the higher the resolution of the sound wave; the lower the frequency of the sound wave, the stronger the penetration ability of the sound wave. Therefore, based on the requirements for resolution and penetration ability in different scenarios, the resonant frequency of the ultrasonic transducer is different. Therefore, the use scenarios of the conventional ultrasonic transducer can be limited. For ease of understanding, examples are introduced as follows:

[0109] For example, the ultrasonic transducer can be applied to a scenario of detecting or identifying surface texture of biological tissue or object. For example, in a fingerprint detection scenario, as shown in FIG. 2A, the ultrasonic transducer is applied to an ultrasonic detection device with fingerprint identification or fingerprint imaging, which can also be referred to as a fingerprint imaging device or a fingerprint identification device. The ultrasonic detection device includes a transducer, a matching layer and a penetrating layer. The matching layer (also referred to as a coupling layer) is located between the transducer and the penetrating layer, and is used to match the acoustic impedance of the transducer and the acoustic impedance of the penetrating layer. The penetrating layer (also referred to as a sensing layer) is used to adhere to biological tissue or object with texture such as a finger. Generally, the concave part of the texture (for example, a fingerprint) is referred to as a valley, and the convex part is referred to as a ridge. The transducer emits an acoustic wave in the direction of the penetrating layer. The emitted acoustic wave can generate a reflected acoustic wave after passing through the matching layer and the penetrating layer to the surface of the biological tissue, and the reflected acoustic wave reaches the transducer after passing through the penetrating layer and the matching layer. Because the acoustic impedance of air at the valley of the finger is different from the acoustic impedance of the tissue at the ridge, the reflectivity of the acoustic wave when encountering the valley and the ridge is different, resulting in different signal strengths of the reflected acoustic wave. Therefore, by detecting the signal strength of the reflected acoustic wave at different positions, the valleys and ridges of the biological tissue can be identified. In the fingerprint detection scenario, the penetrating layer is generally a display screen (for example, a mobile phone display screen, a fingerprint lock display screen, a mobile phone side frame button, etc.), and the resonant frequency of the ultrasonic transducer needs to be close to the resonant frequency of the penetrating layer, so as to achieve the same frequency resonance to improve the sensitivity of the ultrasonic transducer. However, the resonant frequencies of different display screens are different. For example, the resonant frequencies of the existing display screens on the market are distributed in the range of 8MHz to 13MHz. The traditional ultrasonic transducer with a single resonant frequency cannot be compatible with display screens with different resonant frequencies. In addition, some display screens will produce frequency drift after being pasted with a protective film (for example, a mobile phone display screen after being pasted with a protective film). That is, the resonant frequency of the whole formed by the display screen and the protective film is different from the resonant frequency of the single display screen. For example, after the mobile phone display screen is pasted with a protective film, the resonant frequency of the mobile phone display screen can decrease from 13MHz to 9MHz, or increase from 9MHz to 13MHz. Therefore, the traditional ultrasonic transducer with a single resonant frequency can not be suitable for scenarios where the resonant frequency of the display screen changes.

[0110] For example, the ultrasonic transducer can be applied to a scenario of detecting tissue differences inside a biological tissue or an object. For example, in a medical detection scenario, as shown in FIG. 2B, the ultrasonic transducer is applied to an ultrasonic detection device for medical detection. The ultrasonic detection device includes a transducer and a matching layer. The matching layer is located between the transducer and the measured tissue, and is used to match the acoustic impedance of the transducer and the acoustic impedance of the measured tissue. The transducer emits an acoustic wave in the direction of the measured tissue. The reflected acoustic wave is generated after the transmitted acoustic wave passes through the matching layer and reaches the measured tissue, and then reaches the transducer after passing through the penetrating layer. Because the acoustic impedance of the tissue defect in the measured tissue is different from that of the normal tissue, the reflectivity of the acoustic wave is different when it encounters different tissues, resulting in different signal strengths of the reflected acoustic wave. Therefore, whether there is a tissue defect and the location of the tissue defect are determined based on the signal strength of the reflected acoustic wave. In the medical detection scenario, the tissue defect to be detected is not necessarily on the surface of the measured tissue. The resonant frequency of the ultrasonic transducer needs to meet a certain penetration capability to reach the location of the tissue defect. However, different depths of tissue defects have different requirements for the resonant frequency of the ultrasonic transducer. The conventional ultrasonic transducer with a single resonant frequency cannot meet the requirements of different depth detection scenarios.

[0111] To this end, the present application provides an ultrasonic transduction module, an ultrasonic transducer, an ultrasonic detection device, and a terminal, which are used to provide at least two resonant frequencies, so that the same piezoelectric transducer can be applied to scenarios with different frequency requirements.

[0112] It should be noted that the ultrasonic transduction module and the ultrasonic transducer provided by the present application are mainly applied to ultrasonic detection scenarios. For example, ultrasonic fingerprint detection scenarios, medical ultrasonic detection scenarios, industrial ultrasonic detection scenarios, and the like. In addition, the ultrasonic transduction module and the ultrasonic transducer provided by the present application can also be applied to ultrasonic detection scenarios. For example, ultrasonic ranging, ultrasonic flow meters, and the like. The present application does not limit the application scenarios of the ultrasonic transduction module and the ultrasonic transducer. Hereinafter, the ultrasonic fingerprint detection scenario and the medical ultrasonic detection scenario will be mainly introduced as examples.

[0113] The main structure and working principle of the ultrasonic transduction module 00 provided by the present application will be introduced below in conjunction with FIG. 3:

[0114] As shown in FIG. 3, the ultrasonic transducing module 00 provided by the present application comprises, in sequence, a substrate layer 01, a first electrode layer 02, a piezoelectric layer 03 and a second electrode layer 04. Optionally, the ultrasonic transducing module 00 further comprises at least one protective layer 05. Optionally, a glue layer (not shown in the figure) can be arranged between the first electrode layer 02 and the piezoelectric layer 03, which is used to increase the bonding force between the first electrode layer 02 and the piezoelectric layer 03. The thickness of the glue layer can be, for example, hundreds of nanometers, which is far less than the wavelength and can be ignored in the calculation of the thickness-to-wavelength ratio. It should be noted that the functions of each layer of the ultrasonic transducing module 00 in the present embodiment are similar to those of the corresponding layers in the ultrasonic transducing module in the prior art, and specific details are described above with reference to FIG. 1. However, compared with the ultrasonic transducing module in the prior art, the material and thickness of each layer of the ultrasonic transducing module 00 are designed in the present application, so that the ultrasonic transducing module 00 has two different resonance frequencies, which is conducive to the ultrasonic transducing module 00 working at a certain frequency (for example, one of the two resonance frequencies or a frequency between the two resonance frequencies) as needed.

[0115] The implementation principle of the ultrasonic transducing module 00 achieving two resonance frequencies will be introduced below.

[0116] The ultrasonic transducing module 00 provided by the present application has an acoustic reflection interface, which divides the ultrasonic transducing module 00 into two sub-modules, and the two sub-modules respectively constitute two resonators. Specifically, as shown in FIG. 3, the acoustic impedance of the substrate layer 01 and the acoustic impedance of the piezoelectric layer 03 have a large difference, resulting in an acoustic reflection interface between the substrate layer 01 and the piezoelectric layer 03. For example, the acoustic impedance of the piezoelectric layer 03 is much smaller than the acoustic impedance of the substrate layer 01, for example, the ratio of the acoustic impedance of the piezoelectric layer 03 to the acoustic impedance of the substrate layer 01 is less than 0.5; or the acoustic impedance of the piezoelectric layer 03 is much greater than the acoustic impedance of the substrate layer 01, for example, the ratio of the acoustic impedance of the piezoelectric layer 03 to the acoustic impedance of the substrate layer 01 is greater than 2. For ease of introduction, the acoustic reflection interface divides the ultrasonic transducing module 00 into a first sub-module 11 and a second sub-module 12. The first sub-module 11 comprises the piezoelectric layer 03, the second electrode layer 04 and at least one protective layer 05, and the second sub-module 12 comprises the substrate layer 01 and the first electrode layer 02. It should be noted that in the case where the ultrasonic transducing module 00 does not contain the protective layer 05, the first sub-module 11 comprises the piezoelectric layer 03 and the second electrode layer 04. It should be further noted that in the case where the size of the first electrode layer 02 can be ignored, for example, the first electrode layer 02 is a pixelated electrode structure, the second sub-module 12 can be understood as comprising only the substrate layer 01.

[0117] In the first sub-module 11, if the boundary of the first sub-module 11 far from the piezoelectric layer 03 is also an acoustic reflective interface, and the acoustic impedance of each layer in the first sub-module 11 is close, then the first sub-module 11 constitutes a resonator, hereinafter referred to as the first resonator. For example, in the case that the first sub-module 11 contains at least one protective layer 05, if the acoustic impedance of the outermost protective layer 05 is greatly different from that of the adjacent medium (not shown in the figure) outside the first sub-module 11, and the acoustic impedance of the piezoelectric layer 03, the second electrode layer 04 and the protective layer 05 is close, then the first sub-module 11 containing the piezoelectric layer 03, the second electrode layer 04 and the protective layer 05 constitutes the first resonator. For another example, in the case that the first sub-module 11 does not contain the protective layer 05, if the acoustic impedance of the second electrode layer 04 is greatly different from that of the adjacent medium (not shown in the figure) outside the first sub-module 11, and the acoustic impedance of the piezoelectric layer 03 and the second electrode layer 04 is close, then the first sub-module 11 containing the piezoelectric layer 03 and the second electrode layer 04 constitutes the first resonator.

[0118] In the second sub-module 12, if the boundary of the second sub-module 12 far from the piezoelectric layer 03 is also an acoustic reflective interface, and the acoustic impedance of each layer in the second sub-module 12 is close, then the second sub-module 12 constitutes a resonator, hereinafter referred to as the second resonator. For example, in the case that the second sub-module 12 contains the substrate layer 01 and the first electrode layer 02, if the acoustic impedance of the substrate layer 01 is greatly different from that of the adjacent medium (not shown in the figure) outside the second sub-module 12, and the acoustic impedance of the substrate layer 01 and the first electrode layer 02 is close, then the second sub-module 12 containing the substrate layer 01 and the first electrode layer 02 constitutes the second resonator. For another example, in the case that the second sub-module 12 contains only the substrate layer 01, if the acoustic impedance of the substrate layer 01 is greatly different from that of the adjacent medium (not shown in the figure) outside the second sub-module 12, then the substrate layer 01 constitutes the second resonator.

[0119] In addition, although the acoustic reflective interface is formed between the substrate layer 01 and the piezoelectric layer 03, in the case that part of the acoustic wave can penetrate the acoustic reflective interface, and the acoustic impedance of the first sub-module 11 is close to that of the second sub-module 12, the whole (i.e. the ultrasonic transducing module 00) constituted by the first sub-module 11 and the second sub-module 12 can also constitute a resonator, hereinafter referred to as the third resonator. It should be noted that the acoustic reflective interface in the corresponding embodiment of FIG. 3 can be a strong acoustic reflective interface, and the definition of the strong acoustic reflective interface is described above and will not be repeated here.

[0120] It should be noted that the resonance frequency of the first resonator is related to the physical properties of each stack (e.g., the piezoelectric layer 03, the second electrode layer 04, and each protective layer 05; or the piezoelectric layer 03 and the second electrode layer 04) contained in the first sub-module 11; the resonance frequency of the second resonator is related to the physical properties of each stack (e.g., the substrate layer 01 and the first electrode layer 02; or the substrate layer 01) contained in the second sub-module 12; the resonance frequency of the third resonator is related to the physical properties of each stack contained in the ultrasonic transduction module 00. Among them, the physical properties mainly include the material and thickness of the stack. Since different materials generally have different acoustic impedances, it can also be understood that the physical properties mainly include the acoustic impedance and thickness of the stack. When the material (or acoustic impedance) of the stack is determined, the speed of sound of the acoustic wave passing through the stack is determined. Since the speed of sound of the acoustic wave is equal to the product of the wavelength of the acoustic wave and the frequency of the acoustic wave, under the condition that the material of the stack is determined, the wavelength of the acoustic wave and the frequency of the acoustic wave are inversely related, and the wavelength of the acoustic wave in the stack can be changed by adjusting the frequency of the acoustic wave in the stack. Further, by controlling the wavelength of the acoustic wave propagating in the stack of a certain material and the thickness of the stack, the acoustic wave propagating in the stack can be resonated, and the frequency of the wavelength of the acoustic wave propagating in the stack is the resonance frequency of the stack. It should be understood that since the ultrasonic transduction module 00 mainly contains the first sub-module 11 and the second sub-module 12, under the condition that the physical properties of the first sub-module 11 and the second sub-module 12 are determined, the physical properties of the ultrasonic transduction module 00 are also determined. Further, under the condition that the resonance frequencies of the first resonator and the second resonator are determined, the resonance frequency of the third resonator is also determined. For ease of introduction, hereinafter, the resonance frequency of the first resonator and the resonance frequency of the second resonator are referred to as the first resonance frequency, and the resonance frequency of the third resonator is referred to as the second resonance frequency, and the first resonance frequency is different from the second resonance frequency.

[0121] In this embodiment, by setting the material (or acoustic impedance) and thickness of each stack contained in the first sub-module 11 and the second sub-module 12, the first resonator and the second resonator are made to resonate at the same resonance frequency (e.g., the first resonance frequency), and the third resonator is made to resonate at another resonance frequency (e.g., the second resonance frequency), thereby realizing an ultrasonic transduction module 00 with two resonance frequencies.

[0122] Specifically, the embodiment sets the thickness-to-wavelength ratio of each stack included in the first sub-module 11 and the second sub-module 12, so that the first sub-module 11 reaches the resonance condition at the first resonance frequency (i.e., constitutes a first resonator), the second sub-module 12 reaches the resonance condition at the first resonance frequency (i.e., constitutes a second resonator), and the ultrasonic transducing module 00 reaches the resonance condition at the second resonance frequency (i.e., constitutes a third resonator). The thickness-to-wavelength ratio refers to the ratio between the thickness of a medium through which a sound wave passes and the wavelength of the sound wave propagating in the medium. For example, the thickness-to-wavelength ratio of the piezoelectric layer 03 is the ratio between the thickness of the piezoelectric layer 03 and the wavelength of the sound wave propagating in the piezoelectric layer 03. For another example, the thickness-to-wavelength ratio of the substrate layer 01 is the ratio between the thickness of the substrate layer 01 and the wavelength of the sound wave propagating in the substrate layer 01. The thickness-to-wavelength ratios of the remaining stacks are similar and will not be listed one by one here. It should be noted that when sound waves of different frequencies propagate in a stack of the same thickness, the thickness-to-wavelength ratio of the stack is different. For ease of introduction, the ratio between the thickness of any stack and the wavelength of the first resonance frequency sound wave propagating in any stack is the first parameter of any stack; the ratio between the thickness of any stack and the wavelength of the second resonance frequency sound wave propagating in any stack is the second parameter of any stack. For example, taking the piezoelectric layer 03 as an example, the first parameter of the piezoelectric layer 03 is the ratio between the thickness of the piezoelectric layer 03 and the wavelength of the first sound wave (i.e., the sound wave of the first resonance frequency) propagating in the piezoelectric layer 03 (i.e., the wavelength corresponding to the first resonance frequency), and the second parameter of the piezoelectric layer 03 is the ratio between the thickness of the piezoelectric layer 03 and the wavelength of the second sound wave (i.e., the sound wave of the second resonance frequency) propagating in the piezoelectric layer 03 (i.e., the wavelength corresponding to the second resonance frequency). For another example, taking the second electrode layer 04 as an example, the first parameter of the second electrode layer 04 is the ratio between the thickness of the second electrode layer 04 and the wavelength of the first sound wave (i.e., the sound wave of the first resonance frequency) propagating in the second electrode layer 04 (i.e., the wavelength corresponding to the first resonance frequency), and the second parameter of the second electrode layer 04 is the ratio between the thickness of the second electrode layer 04 and the wavelength of the second sound wave (i.e., the sound wave of the second resonance frequency) propagating in the second electrode layer 04 (i.e., the wavelength corresponding to the second resonance frequency). The first parameters and the second parameters of the remaining stacks are similar and will not be described here.

[0123] Specifically, based on the different types of soft and hard of the acoustic reflection boundary, the implementation of each stack of the ultrasonic transducing module 00 has the following multiple types:

[0124] In one possible implementation, as shown in FIG. 4A, in the first sub-module 11, if the acoustic impedance of the piezoelectric layer 03 is much smaller than the acoustic impedance of the substrate layer 01 (for example, the ratio of the acoustic impedance of the piezoelectric layer 03 to the acoustic impedance of the substrate layer 01 is less than 0.5), the boundary between the piezoelectric layer 03 and the substrate layer 01 is a hard boundary; if the acoustic impedance of the outermost protective layer 05 is much greater than the acoustic impedance of the second adjacent medium (i.e., the adjacent medium on the side of the first sub-module 11 away from the second electrode layer 04) (for example, the ratio of the acoustic impedance of the outermost protective layer 05 to the acoustic impedance of the second adjacent medium is greater than 2), the boundary between the outermost protective layer 05 and the second adjacent medium is a soft boundary. Based on the resonance principle, when the boundaries on both sides of the resonator are a soft boundary and a hard boundary respectively, the thickness wavelength ratio of the resonator resonates at a thickness wavelength ratio close to an odd multiple of 1 / 4. Therefore, the sum of the first parameters of the piezoelectric layer 03, the first parameters of the second electrode layer 04, and the first parameters of the at least one protective layer 05 is set to a / 4, a being a positive odd number. It can be understood that the sum of the first parameters of each stack included in the first sub-module 11 is set to a / 4, a being a positive odd number. For example, a can be 1, 3, 5, 7, or 9, etc. At this time, the first sub-module 11 can resonate at the first resonance frequency.

[0125] As shown in FIG. 4A, in the second sub-module 12, if the acoustic impedance of the piezoelectric layer 03 is much smaller than the acoustic impedance of the substrate layer 01 (for example, the ratio of the acoustic impedance of the piezoelectric layer 03 to the acoustic impedance of the substrate layer 01 is less than 0.5), the boundary between the substrate layer 01 and the piezoelectric layer 03 is a soft boundary; if the acoustic impedance of the substrate layer 01 is much greater than the acoustic impedance of the first adjacent medium (i.e., the adjacent medium on the side of the substrate layer 01 away from the piezoelectric layer 03) (for example, the ratio of the acoustic impedance of the substrate layer 01 to the acoustic impedance of the first adjacent medium is greater than 2), the boundary between the substrate layer 01 and the first adjacent medium is a soft boundary. Based on the resonance principle, when the boundaries on both sides of the resonator are soft boundaries, the thickness wavelength ratio of the resonator resonates at a thickness wavelength ratio close to an integer multiple of 1 / 2 (i.e., an even multiple of 1 / 4). Therefore, the sum of the first parameters of the substrate layer 01 and the first parameters of the first electrode layer 02 is set to b / 2, b being a positive integer. It can be understood that the sum of the first parameters of each stack included in the second sub-module 12 is set to b / 2, b being a positive integer. For example, b can be 1, 2, 3, 4, 5, 6, 7, or 8, etc. At this time, the second sub-module 12 can resonate at the first resonance frequency.

[0126] In addition, in the case that the acoustic reflection boundary between the piezoelectric layer 03 and the substrate layer 01 allows partial acoustic wave to penetrate, based on the acoustic impedance relationship of the aforementioned each stack, the boundary between the outermost protective layer 05 and the second adjacent medium is a soft boundary, and the boundary between the substrate layer 01 and the first adjacent medium is a soft boundary in the entire ultrasonic transducing module 00. Based on the resonance principle, when the boundaries on both sides of the resonator are soft boundaries, the thickness wave length ratio of the resonator is close to an integer multiple of 1 / 2 (i.e. an even multiple of 1 / 4) to achieve resonance. Therefore, the sum of the second parameters of the substrate layer 01, the second parameter of the first electrode layer 02, the second parameter of the piezoelectric layer 03, the second parameter of the second electrode layer 04 and the second parameter of the at least one protective layer 05 is set to c / 2, c being a positive integer. It can be understood that the sum of the second parameters of each stack of the ultrasonic transducing module 00 is c / 2, c being a positive integer. It can also be understood that the sum of the first parameters of each stack contained in the first sub-module 11 and the second sub-module 12 is c / 2, c being a positive integer. For example, c can be 1, 2, 3, 4, 5, 6, 7 or 8, etc. At this time, the entire ultrasonic transducing module 00 can achieve resonance at the second resonance frequency.

[0127] It should be noted that if the at least one protective layer 05 is only one protective layer (for example, the first protective layer), the first protective layer is connected to the side of the second electrode layer 04 away from the piezoelectric layer 03, and the ratio of the acoustic impedance of the first protective layer to the acoustic impedance of the second adjacent medium is greater than 2, the second adjacent medium being the medium adjacent to the side of the first protective layer away from the second electrode layer 04. If the at least one protective layer 05 includes two protective layers (for example, the first protective layer and the second protective layer), the first protective layer is connected to the side of the second electrode layer 04 away from the piezoelectric layer 03, the second protective layer is connected to the side of the first protective layer away from the second electrode layer 04, and the ratio of the acoustic impedance of the second protective layer to the acoustic impedance of the second adjacent medium is greater than 2, the second adjacent medium being the medium adjacent to the side of the second protective layer away from the first protective layer. If the at least one protective layer 05 includes three protective layers (for example, the first protective layer, the second protective layer and the third protective layer), the first protective layer is connected to the side of the second electrode layer 04 away from the piezoelectric layer 03, the second protective layer is connected to the side of the first protective layer away from the second electrode layer 04, and the third protective layer is connected to the side of the second protective layer away from the second electrode layer 04, and the ratio of the acoustic impedance of the third protective layer to the acoustic impedance of the second adjacent medium is greater than 2, the second adjacent medium being the medium adjacent to the side of the third protective layer away from the first protective layer. Optionally, the third protective layer can be a damping layer, which has a relatively large acoustic attenuation coefficient, can increase the working bandwidth of the ultrasonic transducing module 00, and thus is conducive to improving the imaging resolution. The way of using other number of protective layers for the at least one protective layer is similar, which is not described here.

[0128] It should be noted that the first adjacent medium can be a display screen or air, and the second adjacent medium can also be a display screen or air. For example, if the screen is attached in a positive manner, the substrate layer is in contact with air, and the outermost protective layer is attached to the display screen, then the first adjacent medium is air, and the second adjacent medium is the display screen (usually made of glass). For another example, if the screen is attached in a negative manner, the substrate layer is attached to the display screen, and the outermost protective layer is in contact with air, then the first adjacent medium is the display screen (usually made of glass), and the second adjacent medium is air.

[0129] Optionally, the acoustic reflection boundary between the piezoelectric layer 03 and the substrate layer 01 allows part of the acoustic wave to pass through, including: the acoustic pressure reflectivity of the acoustic boundary (for example, the aforementioned acoustic reflection boundary) between the piezoelectric layer 03 and the substrate layer 01 is e, wherein 20%<|e|<80%. For example, the value of e can be ±25%, ±30%, ±35%, ±40%, ±45%, ±50%, ±55%, ±60%, ±65%, ±70%, ±75%, and the like. In actual application, e can also be other values, which are not listed here. For example, a higher value of e can be set to obtain a first resonator with higher sensitivity; or a lower value of e can be set to obtain a third resonator with higher sensitivity.

[0130] It should be noted that in some scenarios, other acoustic indicators can be used instead of acoustic pressure reflectivity due to different degrees of difficulty in measuring acoustic reflectivity or acoustic transmissivity. In one example, since the acoustic pressure reflectivity is related to the acoustic energy reflectivity, the acoustic pressure reflectivity can be calculated by the acoustic energy reflectivity. For example, if the acoustic pressure reflectivity is e, then the acoustic energy reflectivity is e 2 , and the aforementioned description about the acoustic pressure reflectivity can be replaced by: the acoustic energy reflectivity of the acoustic boundary (for example, the aforementioned acoustic reflection boundary) between the piezoelectric layer 03 and the substrate layer 01 is e 2 , wherein 4%<e 2 <64%. In another example, since the sum of the acoustic energy reflectivity and the acoustic energy transmissivity is 1, the acoustic pressure reflectivity can be calculated by the acoustic energy transmissivity. For example, if the acoustic pressure reflectivity is e, the acoustic energy reflectivity is e 2 , and the acoustic energy transmissivity is 1-e 2 , and the aforementioned description about the acoustic pressure reflectivity can be replaced by: the acoustic energy transmissivity of the acoustic boundary (for example, the aforementioned acoustic reflection boundary) between the piezoelectric layer 03 and the substrate layer 01 is 1-e 2 , wherein 36%<1-e 2 <96%. The embodiments of the present application only take the acoustic pressure reflectivity as an example for introduction, and the indicators reflecting the acoustic pressure reflectivity deduced by the person skilled in the art based on the relationship between the acoustic pressure reflectivity and other acoustic indicators can also fall within the protection scope of the present application.

[0131] Optionally, the ratio of the second resonant frequency to the first resonant frequency is d. The value of d is related to the thickness-to-wavelength ratios of the three resonators (e.g., the thickness-to-wavelength ratio of the first resonator, the thickness-to-wavelength ratio of the second resonator, and the thickness-to-wavelength ratio of the third resonator). For example, at the first resonant frequency (f1), if the thickness-to-wavelength ratio of the first resonator (i.e., the sum of the first parameters of the layers included in the first sub-module 11) is a / 4, the thickness-to-wavelength ratio of the second resonator (i.e., the sum of the first parameters of the layers included in the second sub-module 12) is b / 2, and the equivalent sound speed of the first resonator is v1, the equivalent sound speed of the second resonator is v2, then the thickness of the first resonator (i.e., the thickness of the first sub-module 11) is approximately (a / 4)v1 / f1, the thickness of the second resonator (i.e., the thickness of the second sub-module 12) is approximately (b / 2)v2 / f1, and the total thickness of the first resonator plus the second resonator is (a / 4)v1 / f1+(b / 2)v2 / f1. The equivalent sound speed can be understood as follows: for a single layer, the equivalent sound speed is the sound speed of the sound wave propagating in the layer; for n layers, the equivalent sound speed can be expressed as where m is the thickness-to-wavelength ratio of the n layers as a whole, m i is the thickness-to-wavelength ratio of the i-th layer, v iThe sound velocity of the i-th layer. In addition, at the second resonance frequency (f2), the thickness wavelength ratio (the second parameter of the stack included in the ultrasonic transducing module 00) of the third resonator is c / 2. Since the thickness of the ultrasonic transducing module 00 is determined when the thicknesses of the first sub-module 11 and the second sub-module 12 are determined, [(a / 4)v1 / f1] / (v1 / f2) + [(b / 2)v2 / f1] / (v2 / f2) = c / 2, and further, (a / 4)f2 / f1 + (b / 2)f2 / f1 = c / 2. In an example, if a = 1, b = 1, and c = 1, f2 = (2 / 3)f1. Considering process errors and the like, and the sound velocity of the same material at different frequencies may change, the value of d in this example can be 0.5 < d < 0.75. For example, the value of d can be 0.6, 0.67, 2 / 3, or 0.7, etc. In another example, if a = 1, b = 1, and c = 2, f2 = (4 / 3)f1. Considering process errors and the like, and the sound velocity of the same material at different frequencies may change, the value of d in this example can be 1 < d < 1.5. For example, the value of d can be 1.2, 1.33, 4 / 3, or 1.4, etc. In another example, if a = 2, b = 1, and c = 1, f2 = (1 / 2)f1. Considering process errors and the like, and the sound velocity of the same material at different frequencies may change, the value of d in this example can be 0.3 < d < 0.8. For example, the value of d can be 0.4, 0.5, 0.6, or 0.7, etc. In actual applications, based on different values of a, b, or c, d can also be other values, which are not listed here.

[0132] In the embodiment, in the case of determining the material and thickness of each stack of the first sub-module 11 and the second sub-module 12 based on the first resonance frequency, by adjusting the frequency of the sound wave (for example, reducing the frequency of the sound wave, increasing the wavelength of the sound wave), the second resonance frequency of d times the first resonance frequency can be determined, so that the first sub-module 11 and the second sub-module 12 achieve the same frequency resonance at the first resonance frequency, and the ultrasonic transducing module 00 resonates at the second resonance frequency, thereby obtaining an ultrasonic transducing module 00 with two resonance frequencies.

[0133] It should be noted that when the first sub-module 11 and / or the second sub-module 12 adopts other implementation manners, based on the same resonance principle, each of the foregoing stacks satisfies the following constraints:

[0134] In one example, when the first sub-module 11 does not contain the protective layer 05 and the second sub-module 12 contains the first electrode layer 02, the sum of the first parameter of the piezoelectric layer 03 and the first parameter of the second electrode layer 04 is a / 4, a is a positive odd number; and the sum of the first parameter of the substrate layer 01 and the first parameter of the first electrode layer 02 is b / 2, b is a positive integer; and the sum of the second parameter of the substrate layer 01, the second parameter of the first electrode layer 02, the second parameter of the piezoelectric layer 03 and the second parameter of the second electrode layer 04 is c / 2, c is a positive integer. It should be noted that when determining the thickness wavelength ratio of the ultrasonic transducer module 00, the thickness wavelength ratio of the first electrode layer 02 (i.e. the first parameter of the first electrode layer 02 and the second parameter of the first electrode layer 02) is considered. In order to ensure the resonance effect, the acoustic impedance of the first electrode layer 02 should be close to the acoustic impedance of the substrate layer 01, so that the interface between the first electrode layer 02 and the substrate layer 01 does not produce a large acoustic reflection.

[0135] In another example, when the first sub-module 11 contains the protective layer 05 and the size of the first electrode layer 02 in the second sub-module 12 is negligible, the sum of the first parameter of the piezoelectric layer 03, the first parameter of the second electrode layer 04 and the first parameter of the at least one protective layer 05 is a / 4, a is a positive odd number; and the first parameter of the substrate layer 01 is b / 2, b is a positive integer; and the sum of the second parameter of the substrate layer 01, the second parameter of the piezoelectric layer 03, the second parameter of the second electrode layer 04 and the second parameter of the at least one protective layer 05 is c / 2, c is a positive integer.

[0136] In another example, when the first sub-module 11 does not contain the protective layer 05 and the size of the first electrode layer 02 in the second sub-module 12 is negligible, the sum of the first parameter of the piezoelectric layer 03 and the first parameter of the second electrode layer 04 is a / 4, a is a positive odd number; and the first parameter of the substrate layer 01 is b / 2, b is a positive integer; and the sum of the second parameter of the substrate layer 01, the second parameter of the piezoelectric layer 03 and the second parameter of the second electrode layer 04 is c / 2, c is a positive integer.

[0137] It should be noted that the standard thickness wavelength resonance theory is generally applicable to single stack resonance. For a resonator composed of multiple stacks, due to the acoustic reflection of the acoustic wave inside the resonator, the actual thickness wavelength ratio may deviate from the theoretical value. For example, the sum of the first parameters of the piezoelectric layer 03, the first parameters of the second electrode layer 04 and the first parameters of the at least one protective layer 05 is (a / 4)±0.2, a is an odd positive integer. For another example, the sum of the first parameters of the substrate layer 01 and the first parameters of the first electrode layer 02 is (b / 2)±0.2, b is a positive integer. For another example, the sum of the second parameters of the substrate layer 01, the second parameters of the first electrode layer 02, the second parameters of the piezoelectric layer 03, the second parameters of the second electrode layer 04 and the second parameters of the at least one protective layer 05 is (c / 2)±0.2, c is a positive integer. The same applies to the multiples of one fourth and the multiples of one half hereinafter, and will not be repeated hereinafter.

[0138] In the embodiment, since the two side boundaries of the first sub-module 11 are a soft boundary and a hard boundary respectively, the two side boundaries of the second sub-module 12 are a soft boundary respectively, and the two side boundaries of the ultrasonic transduction module 00 are a soft boundary respectively, the first parameter of the first sub-module 11 is set to an odd multiple of 1 / 4 (i.e. the first sub-module 11 constitutes a (1 / 4) multiple wavelength resonance), the first parameter of the second sub-module 12 is set to an integer multiple of 1 / 2 (i.e. the second sub-module 12 constitutes a (1 / 2) multiple wavelength resonance), and the second parameter of the ultrasonic transduction module 00 is set to an integer multiple of 1 / 2 (i.e. the ultrasonic transduction module 00 constitutes a (1 / 2) multiple wavelength resonance). Therefore, the first sub-module 11 and the second sub-module 12 realize double-frequency resonance at the first resonance frequency (f1), and the ultrasonic transduction module 00 realizes resonance at the second resonance frequency (f2). This is conducive to the transducer composed of the ultrasonic transduction module 00 being applicable to scenarios with different frequency requirements.

[0139] In another possible implementation, as shown in FIG. 4B, in the first sub-module 11, if the acoustic impedance of the piezoelectric layer 03 is much greater than the acoustic impedance of the substrate layer 01 (for example, the ratio of the acoustic impedance of the piezoelectric layer 03 to the acoustic impedance of the substrate layer 01 is greater than 2), the boundary of the piezoelectric layer 03 to the substrate layer 01 is a soft boundary; if the acoustic impedance of the outermost protective layer 05 is much greater than the second adjacent medium (i.e., the adjacent medium on the side of the first sub-module 11 away from the second electrode layer 04) (for example, the ratio of the acoustic impedance of the outermost protective layer 05 to the acoustic impedance of the second adjacent medium is greater than 2), the boundary of the outermost protective layer 05 to the second adjacent medium is a soft boundary. Based on the resonance principle, when the boundaries on both sides of the resonator are soft boundaries, the thickness wavelength ratio of the resonator resonates at an integer multiple close to 1 / 2 (i.e., an even multiple of 1 / 4). Therefore, the sum of the first parameters of the piezoelectric layer 03, the first parameters of the second electrode layer 04, and the first parameters of the at least one protective layer 05 is set to i / 2, i being a positive integer. For example, i can be 1, 2, 3, 4, 5, 6, 7, or 8, etc. It can be understood that the sum of the first parameters of each stack included in the first sub-module 11 is set to i / 2, i being a positive integer. At this time, the first sub-module 11 can resonate at the first resonance frequency.

[0140] As shown in FIG. 4B, in the second sub-module 12, if the acoustic impedance of the piezoelectric layer 03 is much greater than the acoustic impedance of the substrate layer 01 (for example, the ratio of the acoustic impedance of the piezoelectric layer 03 to the acoustic impedance of the substrate layer 01 is greater than 2), the boundary of the substrate layer 01 to the piezoelectric layer 03 is a hard boundary; if the acoustic impedance of the substrate layer 01 is much greater than the first adjacent medium (i.e., the adjacent medium on the side of the substrate layer 01 away from the piezoelectric layer 03) (for example, the ratio of the acoustic impedance of the substrate layer 01 to the acoustic impedance of the first adjacent medium is greater than 2), the boundary of the substrate layer 01 to the first adjacent medium is a soft boundary. Based on the resonance principle, when the boundaries on both sides of the resonator are a soft boundary and a hard boundary respectively, the thickness wavelength ratio of the resonator resonates at an odd multiple close to 1 / 4. Therefore, the sum of the first parameters of the substrate layer 01 and the first parameters of the first electrode layer 02 is set to j / 4, j being a positive odd number. It can be understood that the sum of the first parameters of each stack included in the second sub-module 12 is set to j / 4, j being a positive odd number. For example, j can be 1, 3, 5, 7, or 9, etc. At this time, the second sub-module 12 can resonate at the first resonance frequency.

[0141] In addition, in the case that the acoustic reflection boundary between the piezoelectric layer 03 and the substrate layer 01 allows partial acoustic wave to transmit, based on the acoustic impedance relationship of the aforementioned each stack, the boundary between the outermost protective layer 05 and the second adjacent medium is a soft boundary, and the boundary between the substrate layer 01 and the first adjacent medium is a soft boundary in the entire ultrasonic transducing module 00. Based on the resonance principle, when the boundaries on both sides of the resonator are soft boundaries, the thickness wave length ratio of the resonator is close to an integer multiple of 1 / 2 (i.e. an even multiple of 1 / 4) to achieve resonance. Therefore, the sum of the second parameters of the substrate layer 01, the first electrode layer 02, the piezoelectric layer 03, the second electrode layer 04 and the at least one protective layer 05 is set to k / 2, k is a positive integer. It can be understood that the sum of the second parameters of each stack of the ultrasonic transducing module 00 is k / 2, k is a positive integer. It can also be understood that the sum of the first parameters of each stack contained in the first sub-module 11 and each stack contained in the second sub-module 12 is k / 2, k is a positive integer. For example, k can be 1, 2, 3, 4, 5, 6, 7 or 8, etc. At this time, the entire ultrasonic transducing module 00 can achieve resonance at the second resonance frequency.

[0142] Optionally, the acoustic reflection boundary between the piezoelectric layer 03 and the substrate layer 01 allows partial acoustic wave to transmit, including: the acoustic pressure reflectivity of the acoustic boundary (for example, the aforementioned acoustic reflection boundary) between the piezoelectric layer 03 and the substrate layer 01 is e, wherein 20%<|e|<80%. For the explanation of the acoustic reflection boundary, please refer to the relevant description in the foregoing embodiments, which will not be repeated here.

[0143] Optionally, the ratio of the second resonant frequency to the first resonant frequency is d. The value of d is related to the thickness wavelength ratios of the three resonators (e.g., the thickness wavelength ratio of the first resonator, the thickness wavelength ratio of the second resonator, and the thickness wavelength ratio of the third resonator). For example, at the first resonant frequency (f3), if the thickness wavelength ratio of the first resonator (i.e., the sum of the first parameters of the layers included in the first sub-module 11) is i / 2, the thickness wavelength ratio of the second resonator (i.e., the sum of the first parameters of the layers included in the second sub-module 12) is j / 4, and the equivalent sound speed of the first resonator is v3, the equivalent sound speed of the second resonator is v4, then the thickness of the first resonator (i.e., the thickness of the first sub-module 11) is about (i / 2)v3 / f3, the thickness of the second resonator (i.e., the thickness of the second sub-module 12) is about (j / 4)v4 / f3, and the total thickness of the first resonator and the second resonator is (i / 2)v3 / f3+(j / 4)v4 / f3. In addition, at the second resonant frequency (f4), the thickness wavelength ratio of the third resonator (i.e., the sum of the second parameters of the layers included in the ultrasonic transducing module 00) is k / 2. Since the thickness of the ultrasonic transducing module 00 is determined when the thicknesses of the first sub-module 11 and the second sub-module 12 are determined, [(i / 2)v3 / f3] / (v3 / f4)+[(j / 4)v4 / f3] / (v4 / f4) = (k / 2), and further (i / 2)f4 / f3+(j / 4)f4 / f3 = (k / 2). In one example, if i = 1, j = 1, and k = 1, then f4 = (2 / 3)f3. Considering factors such as process errors and the fact that the sound speed of the same material may change at different frequencies, the value of d in this example can be 0.5 < d < 0.75. For example, the value of d can be 0.6, 0.67, 2 / 3, or 0.7, etc. In one example, if i = 1, j = 2, and k = 1, then f4 = 2f3. Considering factors such as process errors and the fact that the sound speed of the same material may change at different frequencies, the value of d in this example can be 1.8 < d < 2.2. For example, the value of d can be 1.9, 1.95, 2, or 2.1, etc. In actual applications, d can also be other values based on different values of i, j, or k, which are not listed here.

[0144] In this embodiment, when the materials and thicknesses of the layers of the first sub-module 11 and the second sub-module 12 are determined based on the first resonant frequency, the second resonant frequency which is d times the first resonant frequency can be determined by adjusting the frequency of the sound wave (e.g., reducing the frequency of the sound wave, increasing the wavelength of the sound wave), so that the first sub-module 11 and the second sub-module 12 achieve the same frequency resonance at the first resonant frequency, and the ultrasonic transducing module 00 achieves resonance at the second resonant frequency, thereby obtaining an ultrasonic transducing module 00 having two resonant frequencies.

[0145] It should be noted that when the first sub-module 11 and / or the second sub-module 12 adopts other implementation manners, based on the same resonance principle, the aforementioned each stack satisfies the following constraints:

[0146] In one example, in the case that the first sub-module 11 does not contain the protective layer 05 and the second sub-module 12 contains the first electrode layer 02, the sum of the first parameter of the piezoelectric layer 03 and the first parameter of the second electrode layer 04 is i / 2, i is a positive integer; and the sum of the first parameter of the substrate layer 01 and the first parameter of the first electrode layer 02 is j / 4, j is a positive odd number; and the sum of the second parameter of the substrate layer 01, the second parameter of the first electrode layer 02, the second parameter of the piezoelectric layer 03 and the second parameter of the second electrode layer 04 is k / 2, k is a positive integer.

[0147] In another example, in the case that the first sub-module 11 contains the protective layer 05 and the size of the first electrode layer 02 in the second sub-module 12 is negligible, the sum of the first parameter of the piezoelectric layer 03, the first parameter of the second electrode layer 04 and the first parameter of the at least one protective layer 05 is i / 2, i is a positive integer; and the first parameter of the substrate layer 01 is j / 4, j is a positive odd number; and the sum of the second parameter of the substrate layer 01, the second parameter of the piezoelectric layer 03, the second parameter of the second electrode layer 04 and the second parameter of the at least one protective layer 05 is k / 2, k is a positive integer.

[0148] In another example, in the case that the first sub-module 11 does not contain the protective layer 05 and the size of the first electrode layer 02 in the second sub-module 12 is negligible, the sum of the first parameter of the piezoelectric layer 03 and the first parameter of the second electrode layer 04 is i / 2, i is a positive integer; and the first parameter of the substrate layer 01 is j / 4, j is a positive odd number; and the sum of the second parameter of the substrate layer 01, the second parameter of the piezoelectric layer 03 and the second parameter of the second electrode layer 04 is k / 2, k is a positive integer.

[0149] In the embodiment, since the two side boundaries of the first sub-module 11 are a soft boundary and a hard boundary respectively, the two side boundaries of the second sub-module 12 are a soft boundary respectively, and the two side boundaries of the ultrasonic transducing module 00 are a soft boundary respectively, the first parameter of the first sub-module 11 is set to an integer multiple of 1 / 2 (i.e., the first sub-module 11 constitutes a (1 / 2) multiple wavelength resonance), the first parameter of the second sub-module 12 is set to an odd multiple of 1 / 4 (i.e., the second sub-module 12 constitutes a (1 / 4) multiple wavelength resonance), and the second parameter of the ultrasonic transducing module 00 is set to an integer multiple of 1 / 2 (i.e., the ultrasonic transducing module 00 constitutes a (1 / 2) multiple wavelength resonance). Therefore, the first sub-module 11 and the second sub-module 12 realize double-frequency resonance at the first resonance frequency (f3), and the ultrasonic transducing module 00 realizes resonance at the second resonance frequency (f4). This is conducive to the transducer constituted by the ultrasonic transducing module 00 being applicable to scenarios with different frequency requirements.

[0150] It should be noted that the working frequency of the ultrasonic transducing module 00 in the embodiment of the present application can be the first resonance frequency, can be the second resonance frequency, can be a certain frequency between the first resonance frequency and the second resonance frequency, can be a frequency near the first resonance frequency, can be a frequency near the second resonance frequency, and the like, which is not limited herein. The first resonance frequency and the second resonance frequency can be set according to the working scenario and the penetration thickness of the ultrasonic transducer. For example, if the ultrasonic transducing module 00 is applied to a fingerprint imaging scenario, in order to realize the differentiation of fingerprint ridges and valleys, the higher the frequency, the higher the resolution. For another example, if the ultrasonic transducing module 00 is applied to a scenario with a requirement for the penetration thickness of sound waves, since the higher the frequency of sound waves, the greater the attenuation, in order to ensure sufficient echo intensity, the highest resonance frequency is usually limited. Exemplarily, the two resonance frequencies of the ultrasonic transducing module 00 are between 5 MHz and 25 MHz, and the working frequency of the ultrasonic transducing module 00 ranges from 5 MHz to 25 MHz. For example, the working frequency of the ultrasonic transducing module 00 is 5 MHz, 8 MHz, 10 MHz, 12 MHz, 15 MHz, 18 MHz, 20 MHz, or 24 MHz, and the like.

[0151] It should also be noted that, in the case of meeting the acoustic impedance and the thickness-wavelength ratio of the corresponding embodiments of the foregoing FIG. 4A or FIG. 4B, the material of each layer can have multiple optional implementation manners.

[0152] Optionally, the material of the substrate layer 01 can be any one of glass, silicon or polymer material. For example, the material of the substrate layer 01 is glass, and a thin film transistor (TFT) circuit can be deposited on the surface of the glass. For another example, the material of the substrate layer 01 is silicon, and a complementary metal-oxide-semiconductor (CMOS) circuit can be deposited on the surface of the silicon. For yet another example, the substrate layer 01 can be a flexible substrate, and the material of the flexible substrate is polyimide (PI), and a TFT circuit can be deposited on the surface of the flexible substrate.

[0153] Optionally, the material of the first electrode layer 02 can be any one of various conductive materials, including metal materials (e.g., aluminum (Al), gold (Au), silver (Ag), platinum (Pt), copper (Cu), molybdenum (Mo), titanium (Ti), etc.), conductive polymer materials (e.g., Indium-Tin Oxide (ITO) or graphite, etc.

[0154] Optionally, the material of the piezoelectric layer 03 can be any one of organic polymer material, piezoelectric ceramic material or inorganic piezoelectric material. For example, the organic polymer material can be poly(vinylidene fluoride) (PVDF) and its copolymer poly(vinylidene fluoride-trifluoroethylene) (PVDF-TRFE) or blend PVDF-graphene oxide, etc. For example, the piezoelectric ceramic material can be Lead Zirconate Titanate (PZT) and its alloy material (Lead Lanthanum Zirconate Titanate ceramic PLZT, Lead Magnesium Niobate PNZT), KNN (KxNa1-xNbO3), Lead Magnesium Niobate-Lead Titanate (PMN-PT), etc. For example, the inorganic piezoelectric material can be inorganic piezoelectric material aluminum nitride (AlN) and its alloy material (ScxAl1-xN), zinc oxide (ZnO) and its alloy material (VxZn1-xO), etc.

[0155] Optionally, the material of the second electrode layer 04 can be any one of various conductive materials, including graphite, metal materials (e.g., Al, Au, Ag, Pt, nickel (Ni), Cu, Mo, Ti, etc.), conductive polymer materials (e.g., ITO, Ag paste material, Cu paste material, Al paste material, etc.), etc.

[0156] Optionally, the material of the protective layer 05 includes a polymer material and / or a metal. The polymer material can be an optically clear adhesive (OCA) or a pressure sensitive adhesive (PSA), etc. The adhesive layer can be formed by stacking multiple polymer materials, for example, a composite adhesive tape composed of PSA, poly(ethylene terephthalate) (PET) and PSA. The metal material can be Al, Au, Ag, Pt, Cu, Mo, Ti, etc. For example, the at least one protective layer 05 includes a first protective layer and a second protective layer, wherein the material of the first protective layer includes an adhesive, and the material of the second protective layer includes a metal. Optionally, the adhesive layer and the metal layer are implemented by one-step bonding process, for example, a Cu adhesive tape (including a Cu layer and an adhesive layer), an Al adhesive tape, etc.

[0157] Optionally, the metal material of the second protective layer is different from the metal material of the second electrode layer 04. For example, the material of the second electrode layer 04 is silver paste, and the material of the second protective layer is copper. The introduction of the copper layer can reduce the thickness of the high-cost second electrode layer 04, thereby reducing the overall cost.

[0158] It should be noted that one layer in the embodiment of the present application can be a single layer structure or can be obtained by stacking a multi-layer structure. The materials of different layers in the multi-layer structure can be the same or different. One layer can be any layer in the resonator. For example, the second electrode layer 04 can be sputtered with a sub-micron thick metal layer on the surface of the Ag paste electrode layer to improve the roughness of the Ag electrode surface. For another example, the first protective layer is a multi-layer polymer material, and a hard polymer layer can be added to the soft adhesive material on both sides to serve as an electrical isolation between the second electrode layer and the second protective layer. At the same time, the thinning of the soft adhesive material on both sides can also reduce the size of the bubbles in the adhesive layer. For another example, the second protective layer is a multi-layer structure, and an oxidation-resistant metal layer (such as Al, Au, Ni, etc.) or a polymer protective layer can be deposited on the surface of the second protective layer.

[0159] For ease of understanding, the ultrasonic transducer module 00 provided by the present application will be introduced below in combination with specific layer materials:

[0160] Figure 5A is an example diagram of an ultrasonic transducing module 00 of the corresponding embodiment of Figure 4A. As shown in Figure 5A, the substrate layer 01 is made of glass (with TFT circuit on the surface), the piezoelectric layer 03 is made of PVDF-TRFE, the second electrode layer 04 is made of silver paste (Ag + polymer), the first protective layer 051 is made of PET glue, and the second protective layer 052 is made of copper (Cu). The acoustic impedance R1 of PVDF-TRFE is about 4.5 MRaly, and the acoustic impedance R2 of glass is about 13.5 MRaly. Based on the acoustic transmission theory, the acoustic pressure reflection coefficient at the interface between the piezoelectric layer 03 (R1) and the substrate layer 01 (R2) is r1 = (R2 - R1) / (R2 + R1) = 50%. That is, when the acoustic wave transmitted from the piezoelectric layer 03 to the substrate layer 01 passes through the interface, about 50% of the acoustic wave is reflected back to the piezoelectric layer 03, so the interface is a strong acoustic reflection boundary. The strong acoustic reflection boundary divides the ultrasonic transducing module 00 into a first sub-module 11 and a second sub-module 12. In the first sub-module 11, since the acoustic impedance of PVDF-TRFE is smaller than the acoustic impedance of glass, the boundary between the piezoelectric layer 03 and the substrate layer 01 is a hard boundary; since the second protective layer 052 is always in contact with air, the acoustic impedance of copper is much greater than the acoustic impedance of air, so the boundary between the second protective layer 052 and air is a soft boundary. In addition, the acoustic impedance of each layer in the first sub-module 11 is close to 4.5 MRaly, so the first sub-module 11 can be regarded as a whole to form a first resonator with 1 / 4 wavelength resonance. In the second sub-module 12, since the acoustic impedance of PVDF-TRFE is smaller than the acoustic impedance of glass, the boundary between the substrate layer 01 and the piezoelectric layer 03 is a soft boundary; since the substrate layer 01 is always in contact with air (or a display screen), the acoustic impedance of glass is greater than the acoustic impedance of air (or the acoustic impedance of a display screen), so the boundary between the substrate layer 01 and air is a soft boundary. In addition, the thickness and acoustic impedance of the first electrode layer 02 can be ignored, so the acoustic impedance in the second sub-module 12 is close to the acoustic impedance of glass, so the second sub-module 12 can be regarded as a whole to form a second resonator with 1 / 2 wavelength resonance. In addition, since the boundaries on both sides of the ultrasonic transducing module 00 are soft boundaries, and a part of the acoustic wave passes through the interface between the piezoelectric layer 03 and the substrate layer 01, the ultrasonic transducing module 00 can be regarded as a whole to form a third resonator with 1 / 2 wavelength resonance.

[0161] For example, in the under-screen fingerprint recognition scenario, the frequency of the display screen is usually 5-15 MHz, and the resonance frequency of the ultrasonic transducing module 00 should be close to the frequency of the display screen. For example, if the first resonance frequency is set to 13 MHz, and the thickness-to-wavelength ratio of each stack is set according to the manner shown in FIG. 4A, the second resonance frequency can be 8.7 MHz, and the thickness of each stack can be obtained. As shown in FIG. 5A, the thickness of each stack is as follows: the thickness of the substrate layer 01 (made of glass) is 250 um, the thickness of the first electrode layer 02 is negligible, the thickness of the piezoelectric layer 03 (made of PVDF-TRFE) is 9 um, the thickness of the second electrode layer 04 (made of Ag) is 6 um, the thickness of the first protective layer 051 (made of PET glue) is 5 um, and the thickness of the second protective layer 052 (made of Cu) is 6 um. It should be noted that the thickness of each stack shown in FIG. 5A is only an example. In actual applications, if the first resonance frequency, the second resonance frequency, or the material of each stack changes, the thickness of each stack shown in FIG. 5A should also be adaptively adjusted to achieve the resonance effect shown in FIG. 4A. This application will not list examples one by one.

[0162] For example, FIG. 6 is a schematic diagram of the simulation results of the example shown in FIG. 5A, in which the horizontal coordinate is the frequency (unit: megahertz (MHz)), and the vertical coordinate is the electrical impedance (unit: ohm (Ω)). As shown in FIG. 6, there are two resonance peaks in the sweep range of 7-15 MHz, i.e., f2=9.2 MHz and f1=13.6 MHz. Taking f1 as the first resonance frequency, the sum of the thickness-to-wavelength ratios of each stack included in the first sub-module 11 is 0.29, which is close to the theoretical value 1 / 4. Taking f2 as the second resonance frequency, the sum of the thickness-to-wavelength ratios of each stack included in the second sub-module 12 is 0.55, which is close to the theoretical value 1 / 2. The sum of the thickness-to-wavelength ratios of each stack included in the ultrasonic transducing module 00 is 0.57, which is close to the theoretical value 1 / 2. As can be seen, in the example shown in FIG. 5A, the first sub-module 11 and the second sub-module 12 achieve the same frequency resonance at the first resonance frequency f1=13.6 MHz, and the entire ultrasonic transducing module 00 can also achieve resonance at the second resonance frequency f2=9.2 MHz. Therefore, the working frequency of the ultrasonic transducing module 00 can be set to 9.2 MHz or 13.6 MHz. In some scenarios where the sensitivity requirement is not strict, the working frequency of the ultrasonic transducing module 00 can also be set to a frequency near 9.2 MHz (for example, 8 MHz or 10 MHz) or a frequency near 13.6 MHz (for example, 13 MHz or 14 MHz), which is not limited here.

[0163] Figure 5B is another schematic diagram of the ultrasonic transducing module 00 of the corresponding embodiment of Figure 4A. As shown in Figure 5B, the material of the substrate layer 01 in the example shown in Figure 5A is replaced by silicon (e.g., a silicon-based substrate), and the thickness of the substrate layer 01 is set to 350 um, and the materials and thicknesses of the rest of the layers are the same as those of the example shown in Figure 5A. For details, please refer to the corresponding description of Figure 5A, which will not be repeated here. Since the acoustic impedance of the silicon-based substrate and the glass are both much greater than the acoustic impedance of the piezoelectric PVDF-TRFE material, the boundary conditions shown in Figure 5A still apply, i.e., the first sub-module 11 as a whole constitutes a first resonator of 1 / 4 wavelength resonance, the second sub-module 12 as a whole constitutes a second resonator of 1 / 2 wavelength resonance, and the ultrasonic transducing module 00 as a whole constitutes a third resonator of 1 / 2 wavelength resonance. In this example, since the silicon-based substrate can adopt mature CMOS technology, the noise floor of the CMOS circuit is smaller than that of the TFT circuit, and thus it is beneficial to obtain higher imaging quality.

[0164] Figure 5C is an example diagram of an ultrasonic transducing module 00 of the corresponding embodiment of Figure 4B. As shown in Figure 5C, the substrate layer 01 is made of a flexible substrate (PI) with TFT pixel circuits integrated on the surface of the flexible substrate, the piezoelectric layer 03 is made of PZT, the second electrode layer 04 is made of metal, the first protective layer 051 is made of glue, and the second protective layer 052 is made of metal. The metal of the second electrode layer 04 and the metal of the second protective layer 052 can be different. The acoustic impedance R3 of PZT is about 30 MRaly, and the acoustic impedance R4 of the flexible substrate is about 3 MRaly. Based on the acoustic transmission theory, the acoustic pressure reflection coefficient of the interface between the piezoelectric layer 03 (R3) and the substrate layer 01 (R4) is r2 = (R4 - R3) / (R4 + R3) = -81.8%, so the interface is a strong acoustic reflection boundary. The strong acoustic reflection boundary divides the ultrasonic transducing module 00 into a first sub-module 11 and a second sub-module 12. In the first sub-module 11, since the acoustic impedance of PZT is greater than the acoustic impedance of the flexible substrate, the boundary between the piezoelectric layer 03 and the substrate layer 01 is a soft boundary; since the second protective layer 052 is often in contact with air, the acoustic impedance of metal is much greater than the acoustic impedance of air, so the boundary between the second protective layer 052 and air is a soft boundary. In addition, the acoustic impedance of each layer in the first sub-module 11 is close to the acoustic impedance of PZT, for example, the second electrode layer 04 and the second protective layer 052 are made of metal with an acoustic impedance close to 30 MRaly. Since the acoustic impedance of the glue layer is not easy to approach 30 MRaly, in order to achieve effective penetration of acoustic waves to the glue layer, the thickness of the first protective layer 051 (i.e. the glue layer) can be controlled to be much smaller than the wavelength (for example, the thickness of the glue layer is much smaller than < λ / 10). Therefore, the first sub-module 11 can be regarded as a whole to form a first resonator with 1 / 2 wavelength resonance. In the second sub-module 12, since the acoustic impedance of PZT is greater than the acoustic impedance of the flexible substrate, the boundary between the substrate layer 01 and the piezoelectric layer 03 is a hard boundary; since the substrate layer 01 is often in contact with air (or a display screen), the acoustic impedance of the flexible substrate is greater than the acoustic impedance of air (or the acoustic impedance of the display screen), so the boundary between the substrate layer 01 and air is a soft boundary. In addition, the thickness and acoustic impedance of the first electrode layer 02 can be ignored, so the acoustic impedance in the second sub-module 12 is close to the acoustic impedance of the flexible substrate, so the second sub-module 12 can be regarded as a whole to form a second resonator with 1 / 4 wavelength resonance. In addition, since the boundaries on both sides of the ultrasonic transducing module 00 are soft boundaries, and part of the acoustic waves pass through the interface between the piezoelectric layer 03 and the substrate layer 01, the ultrasonic transducing module 00 can be regarded as a whole to form a third resonator with 1 / 2 wavelength resonance. The specific way of calculating the thickness of each layer is similar to the example corresponding to Figure 5A, which is not described here.

[0165] FIG. 5D is another schematic diagram of the ultrasonic transducing module 00 of the embodiment corresponding to FIG. 4B. As shown in FIG. 5D, the material of the substrate layer 01 in the example shown in FIG. 5C is replaced by glass, and the materials of the remaining layers are the same as those in the example shown in FIG. 5C. For details, please refer to the related description of FIG. 5C, which will not be repeated here. Since the acoustic impedance of the flexible substrate and the glass is much smaller than the acoustic impedance of the piezoelectric PZT material, the boundary conditions shown in FIG. 5C still apply, that is, the first sub-module 11 as a whole constitutes a first resonator of 1 / 2 wavelength resonance, the second sub-module 12 as a whole constitutes a second resonator of 1 / 4 wavelength resonance, and the ultrasonic transducing module 00 as a whole constitutes a third resonator of 1 / 2 wavelength resonance.

[0166] It should be noted that in actual applications, other materials and / or thicknesses can be set for each layer based on the specific application scenario of the ultrasonic transducing module 00 to obtain an ultrasonic transducing module 00 with two resonance frequencies. Examples will not be listed one by one here.

[0167] It should be further noted that the two resonance frequencies in the present embodiment mainly refer to the fundamental resonance frequencies of the ultrasonic transducing module 00, denoted as f1 and f2. In some scenarios, the ultrasonic transducing module 00 can be excited by a higher harmonic, wherein the higher harmonic frequency is an integer multiple of the fundamental frequency. Optionally, the higher harmonic includes the second harmonic, the third harmonic, etc., wherein the second harmonic frequency is 2 times the fundamental frequency, and the third harmonic frequency is 3 times the fundamental frequency. For example, if the fundamental frequency is f1, the second harmonic frequency corresponding to the fundamental is 2f1, and the resonance frequencies of the ultrasonic transducing module 00 include f1 and 2f1. For another example, if the fundamental frequency is f2, the third harmonic frequency corresponding to the fundamental is 3f2, and the resonance frequencies of the ultrasonic transducing module 00 include f2, 2f2 and 3f2. In the present embodiment and subsequent embodiments, the fundamental is mainly taken as an example for introduction.

[0168] It should be noted that in order to ensure the sensitivity of the ultrasonic transducer formed by the ultrasonic transducing module 00, a high-voltage (for example, 150V) excitation signal driving circuit is generally required for the ultrasonic transducing module 00. In order to realize the high-voltage excitation signal, the excitation signal is usually amplified by an LC oscillation circuit. In the LC oscillation circuit, L refers to inductance, which is mainly composed of the lead of the ultrasonic transducing module 00 and the external inductance; C refers to capacitance, which is mainly composed of the capacitance between the upper and lower electrodes of the ultrasonic transducing module 00. The resonance frequency of the LC oscillation circuit is The closer the frequency of the excitation signal is to the resonance of the LC oscillation circuit, the better the effect of amplifying the voltage, and thus the greater the sensitivity of the ultrasonic transduction module 00. When the frequency of the excitation signal is the same as the resonance frequency of the ultrasonic transduction module 00, the ultrasonic transduction module 00 works at the resonance frequency, and the sensitivity reaches the maximum. For a specific working frequency, a specific lead length needs to be designed to achieve resonance voltage amplification at the working frequency. The ultrasonic transduction module 00 provided by the embodiments of the present application has two resonance frequencies, and needs to be suitable for a dual-frequency scenario, for example, switching between two frequencies based on the application scenario. However, the traditional single lead length is difficult to be compatible with resonance driving at dual frequencies, thereby leading to a decrease in driving voltage at a certain frequency and sacrificing sensitivity.

[0169] To this end, the embodiments of the present application propose a block electrode design to realize different capacitances and thus drive different frequencies.

[0170] Specifically, the second electrode layer 04 in the foregoing embodiments corresponding to FIG. 3, FIG. 4A or FIG. 4B includes at least two electrode blocks, each of which constitutes a capacitor with the first electrode layer 02. At least one capacitor, an inductor connected with the capacitor and at least one switching circuit are used to constitute an oscillation circuit, and the number of electrode blocks connected to the oscillation circuit is controlled by the switching, and thus the capacitance connected to the oscillation circuit is controlled.

[0171] It should be noted that the number of electrode blocks included in the second electrode layer 04 and the area of different electrode blocks are related to the resonant frequencies of the ultrasonic transducing module 00. In one example, if the ultrasonic transducing module 00 has two resonant frequencies (e.g., the aforementioned first resonant frequency (f1) and the aforementioned second resonant frequency (f2)), the second electrode layer 04 is provided with at least two electrode blocks, which form at least two capacitors. The capacitance value of the oscillation circuit is controlled by controlling the number of electrode blocks accessed by the oscillation circuit, and the switching between the two oscillation circuits is realized by the on-off of the switch. The resonant frequencies of the two oscillation circuits correspond to the two resonant frequencies (e.g., the aforementioned first resonant frequency and the aforementioned second resonant frequency) of the ultrasonic transducing module 00. In another example, if the ultrasonic transducing module 00 has multiple resonant frequencies (e.g., the ultrasonic transducing module 00 has multiple resonant frequencies under high harmonic excitation), the second electrode layer 04 is provided with multiple electrode blocks. The capacitance value of the oscillation circuit is controlled by controlling the number of electrode blocks accessed by the oscillation circuit, and the switching between the multiple oscillation circuits is realized by the on-off of the switch. The resonant frequencies of the multiple oscillation circuits correspond to the multiple resonant frequencies of the ultrasonic transducing module 00. For example, if the ultrasonic transducing module 00 is expanded in the working mode of the second harmonic, the resonant frequencies include f1, f2, 2f1 and 2f2, the second electrode layer 04 is provided with at least four electrode blocks, which form at least four capacitors. The capacitance value of the oscillation circuit is controlled by controlling the number of electrode blocks accessed by the oscillation circuit, and the switching between the four oscillation circuits is realized by the on-off of the switch. The resonant frequencies of the four oscillation circuits correspond to the aforementioned four resonant frequencies (e.g., the aforementioned f1, f2, 2f1 and 2f2). For another example, if the ultrasonic transducing module 00 is expanded in the working mode of the second harmonic and the third harmonic, the resonant frequencies include f1, f2, 2f1, 2f2, 3f1 and 3f2, the second electrode layer 04 is provided with at least six electrode blocks, which form at least six capacitors. The capacitance value of the oscillation circuit is controlled by controlling the number of electrode blocks accessed by the oscillation circuit, and the switching between the six oscillation circuits is realized by the on-off of the switch. The resonant frequencies of the six oscillation circuits correspond to the aforementioned six resonant frequencies (e.g., the aforementioned f1, f2, 2f1, 2f2, 3f1 and 3f2). Other high harmonics are similar, which are not described here.

[0172] In this embodiment, the second electrode layer 04 includes the first electrode block and the second electrode block as an example, and the mode of the second electrode layer 04 including 3 or more electrode blocks is not described. Among them, the first electrode block and the first electrode layer 02 constitute the first capacitor, for example, the first electrode block and the projection area of the first electrode block on the first electrode layer 02 constitute the first capacitor. Since the area of the first electrode layer 02 is larger than the area of the first electrode block, the size of the capacitance value of the first capacitor is related to the area of the first electrode block. For example, the size of the capacitance value of the first capacitor is positively correlated with the area of the first electrode block. In addition, the second electrode block and the first electrode layer 02 constitute the second capacitor, for example, the second electrode block and the projection area of the second electrode block on the first electrode layer 02 constitute the second capacitor. Since the area of the first electrode layer 02 is larger than the area of the second electrode block, the size of the capacitance value of the second capacitor is related to the area of the second electrode block. For example, the size of the capacitance value of the second capacitor is positively correlated with the area of the second electrode block.

[0173] It should be noted that the first electrode block and the second electrode block are connected with the inductor and at least one switching circuit, and different connection modes can realize different oscillation circuits. The following will be introduced respectively:

[0174] In a possible implementation, as shown in FIG. 7A, the second electrode block is connected in series with the switching circuit, the second electrode block and the switching circuit are connected in parallel with the first electrode block, and the inductor is connected in series with the parallel first electrode block and second electrode block. It can be understood that the second capacitor is connected in series with the switching circuit, the series circuit composed of the second capacitor and the switching circuit is connected in parallel with the first capacitor, and the inductor is connected in series with the parallel first capacitor and second capacitor.

[0175] In the case of opening of the switching circuit, the first electrode block is connected to the circuit and the second electrode block is not connected to the circuit, that is, the second capacitor does not work, only the first capacitor is connected in series with the external inductor, and a first oscillation circuit is constituted, and the working frequency of the first oscillation circuit is located in the first frequency band.

[0176] In the case of closing of the switching circuit, the first capacitor and the second capacitor both work, and the first capacitor and the second capacitor are connected in parallel, the parallel first capacitor and second capacitor are connected in series with the inductor, and then the first capacitor, the second capacitor and the inductor constitute a second oscillation circuit, and the working frequency of the second oscillation circuit is located in the second frequency band.

[0177] Optionally, the first frequency band is a frequency range containing the first resonant frequency, and the second frequency is a frequency range containing the second resonant frequency. For example, if the first resonant frequency is 13 MHz, the first frequency band can be 12 MHz-14 MHz; if the second resonant frequency is 9 MHz, the second frequency band can be 8 MHz-10 MHz. Since, when the switch circuit is open, only the first capacitor is connected to the oscillation circuit (i.e., the first oscillation circuit); when the switch circuit is closed, the first capacitor and the second capacitor are connected in parallel to the oscillation circuit (i.e., the second oscillation circuit), therefore, the capacitance value of the first oscillation circuit is greater than that of the second oscillation circuit. Since, the capacitance value of the oscillation circuit is inversely related to the resonant frequency of the oscillation circuit, therefore, the frequency of the first frequency band is greater than that of the second frequency band.

[0178] In this embodiment, by controlling the area or number of the electrode blocks connected to the circuit through the switch circuit, the capacitance value of the circuit is controlled, so that the resonant frequency of the oscillation circuit can not only reach the desired resonant frequency, but also be switched at different resonant frequencies according to the on-off of the switch. This is conducive to improving the flexibility of the frequency of the excitation signal applied to the ultrasonic transducer module 00.

[0179] Optionally, when the switch circuit is open, the working frequency of the first oscillation circuit is the first resonant frequency, i.e., the working frequency applied to the ultrasonic transducer module 00 is the first resonant frequency; when the switch circuit is closed, the working frequency of the second oscillation circuit is the second resonant frequency, i.e., the working frequency applied to the ultrasonic transducer module 00 is the second resonant frequency. Since, the capacitance value is positively related to the area of the electrode block, and the resonant frequency is inversely related to the capacitance value, therefore, the resonant frequency is inversely related to the area of the electrode block. In this example, the areas of the first electrode block and the second electrode block satisfy the following formula:

[0180] S1 / (S2+S1)=(f2 / f1) 2 ; wherein S1 is the area of the first electrode block, S2 is the area of the second electrode block, f1 is the first resonant frequency, and f2 is the second resonant frequency.

[0181] For example, taking the ultrasonic transducer module 00 shown in FIG. 4A as an example, in the case of a=1, b=1, and c=1, f2=(2 / 3)f1, then S1 / (S2+S1)=4 / 9; in the case of a=2, b=1, and c=1, f2=(1 / 2)f1, then S1 / (S2+S1)=1 / 4. For the explanations of a, b, c, f1, and f2, please refer to the relevant descriptions in the foregoing, which will not be repeated here. In actual applications, when a, b, and c take other values, f2 / f1 will change, thereby causing S1 / (S2+S1) to take different values, and examples will not be introduced one by one here.

[0182] In the embodiment, when the high frequency is driven, the switch is turned off, and only the first electrode block works; when the low frequency is driven, the switch is turned on, and the first electrode block and the second electrode block work together. By adjusting the capacitance in the oscillation circuit through different driving areas, the resonance condition can be met at different resonance frequencies.

[0183] Optionally, as shown in FIG. 7B, the first capacitor can be connected in parallel with a third capacitor, which can be an external capacitor or a parasitic capacitor. At this time, the capacitance value of the first capacitor, the capacitance value of the second capacitor and the capacitance value of the third capacitor satisfy the following formula:

[0184] (C1+C3) / (C2+C1+C3)=(f2 / f1) 2 ; wherein C1 is the capacitance value of the first capacitor, C2 is the capacitance value of the second capacitor, C3 is the capacitance value of the third capacitor, f1 is the first resonance frequency, and f2 is the second resonance frequency.

[0185] For example, in the case of the ultrasonic transducer module 00 shown in FIG. 4A, when a=1, b=1 and c=1, f2=(2 / 3)f1, then (C1+C3) / (C2+C1+C3)=4 / 9; when a=2, b=1 and c=1, f2=(1 / 2)f1, then (C1+C3) / (C2+C1+C3)=1 / 4. For the explanation of a, b, c, f1 and f2, please refer to the relevant description in the foregoing, which will not be repeated here. In actual application, when a, b and c take other values, f2 / f1 will change, and then (C1+C3) / (C2+C1+C3) will take different values, which will not be introduced one by one.

[0186] In the embodiment, the third capacitor (i.e. the external capacitor and / or the parasitic capacitor) is introduced, the influence of the parasitic capacitor on the circuit is considered, and the matching accuracy of the frequency is improved. In addition, the external capacitor is added, the adjustment range of the capacitance value of the oscillation circuit is expanded, and the frequency range matched by the oscillation circuit is expanded.

[0187] In another possible embodiment, as shown in FIG. 7C, the first electrode block is connected in series with the first switch circuit, the second electrode block is connected in series with the second switch circuit, the series-connected first electrode block and the first switch circuit are connected in parallel with the series-connected second electrode block and the second switch circuit, and the inductor is connected in series with the parallel-connected first electrode block and the second electrode block. It can be understood that the first capacitor is connected in series with the first switch circuit, the second capacitor is connected in series with the second switch circuit, the series-connected first capacitor and the first switch circuit are connected in parallel with the series-connected second capacitor and the second switch circuit, and the inductor is connected in series with the parallel-connected first capacitor and the second capacitor.

[0188] In the case that the first switch circuit is closed and the second switch circuit is opened, the first electrode block works and the second electrode block does not work, only the first electrode block is in series with the external inductance, that is, the first capacitor and the external inductance constitute a third oscillation circuit. At this time, the working frequency of the third oscillation circuit is located in the third frequency band. It can be understood that the first electrode block is used to drive the third frequency band.

[0189] In the case that the second switch circuit is closed and the first switch circuit is opened, the second electrode block works and the first electrode block does not work, only the second electrode block is in series with the external inductance, that is, the second capacitor and the external inductance constitute a fourth oscillation circuit. At this time, the working frequency of the fourth oscillation circuit is located in the second frequency band. It can be understood that the second electrode block is used to drive the fourth frequency band.

[0190] Optionally, if the area of the first electrode block is smaller than the area of the second electrode block, the frequency of the third frequency band is greater than the frequency of the fourth frequency band; if the area of the first electrode block is greater than the area of the second electrode block, the frequency of the third frequency band is less than the frequency of the fourth frequency band.

[0191] In the embodiment, whether the first electrode block and the second electrode block are connected to the circuit is controlled by two independent switch circuits (i.e., the first switch circuit and the second switch circuit), which is beneficial to flexibly control the size of the capacitance value connected to the circuit, so that the resonant frequency of the oscillation circuit can not only reach the expected resonant frequency, but also can be switched at different resonant frequencies according to the on-off of the switch. It is beneficial to improve the flexibility of the frequency of the excitation signal applied to the ultrasonic transducer module 00.

[0192] Optionally, in the case that the first switch circuit is closed and the second switch circuit is opened, the working frequency of the third oscillation circuit is the first resonant frequency, that is, the working frequency applied to the ultrasonic transducer module 00 is the first resonant frequency; in the case that the second switch circuit is closed and the first switch circuit is opened, the working frequency of the second oscillation circuit is the second resonant frequency, that is, the working frequency applied to the ultrasonic transducer module 00 is the second resonant frequency. Since the capacitance value is positively correlated with the area of the electrode block, and the resonant frequency is inversely correlated with the capacitance value, the resonant frequency is inversely correlated with the area of the electrode block. In the example, the area of the first electrode block and the area of the second electrode block satisfy the following formula:

[0193] S1 / S2=(f2 / f1) 2 ; wherein S1 is the area of the first electrode block, S2 is the area of the second electrode block, f1 is the first resonant frequency, and f2 is the second resonant frequency.

[0194] For example, in the case of the ultrasonic transducer module 00 shown in FIG. 4A, when a = 1, b = 1, and c = 1, f2 = (2 / 3)f1, then S1 / S2 = 4 / 9; when a = 1, b = 1, and c = 2, f2 = (4 / 3)f1, then S1 / S2 = 16 / 9; when a = 2, b = 1, and c = 1, f2 = (1 / 2)f1, then S1 / S2 = 1 / 4. For the explanations of a, b, c, f1, and f2, please refer to the relevant descriptions in the foregoing, which will not be repeated here. In actual applications, when a, b, and c take other values, f2 / f1 will change, thereby resulting in different values of S1 / S2, which will not be introduced one by one here.

[0195] In the embodiment, the first electrode block and the second electrode block are respectively connected through the switching circuit, and when high-frequency driving, the electrode block with a smaller area works; when low-frequency driving, the electrode block with a larger area works. By adjusting the capacitance in the oscillation circuit through different electrode block areas, the resonance condition can be met at different resonance frequencies.

[0196] Optionally, as shown in FIG. 7D, the first capacitor can be connected in parallel with a fourth capacitor, which can be an external capacitor or a parasitic capacitor. At this time, the capacitance value of the first capacitor, the capacitance value of the second capacitor, and the capacitance value of the fourth capacitor satisfy the following formula:

[0197] (C1+C4) / (C2+C4)=(f2 / f1) 2 ; wherein C1 is the capacitance value of the first capacitor, C2 is the capacitance value of the second capacitor, C4 is the capacitance value of the fourth capacitor, f1 is the first resonance frequency, and f2 is the second resonance frequency.

[0198] For example, in the case of the ultrasonic transducer module 00 shown in FIG. 4A, when a = 1, b = 1, and c = 1, f2 = (2 / 3)f1, then (C1+C4) / (C2+C4) = 4 / 9; when a = 1, b = 1, and c = 2, f2 = (4 / 3)f1, then (C1+C4) / (C2+C4) = 16 / 9; when a = 2, b = 1, and c = 1, f2 = (1 / 2)f1, then (C1+C4) / (C2+C4) = 1 / 4. For the explanations of a, b, c, f1, and f2, please refer to the relevant descriptions in the foregoing, which will not be repeated here. In actual applications, when a, b, and c take other values, f2 / f1 will change, thereby resulting in different values of (C1+C4) / (C2+C4), which will not be introduced one by one here.

[0199] In this embodiment, the fourth capacitor (i.e. the external capacitor and / or the parasitic capacitor) is introduced, the influence of the parasitic capacitor on the circuit is considered, and the matching accuracy of the frequency is improved. In addition, the external capacitor is added, the adjustment range of the capacitance value of the oscillation circuit is expanded, and the frequency range matched by the oscillation circuit is expanded.

[0200] It should be noted that the arrangement of the first electrode block and the second electrode block in the second electrode layer 04 has multiple modes. In one example, as shown in example a of FIG. 8, the first electrode block and the second electrode block can be distributed inside and outside, that is, the second electrode block is in a ring structure, and the first electrode block is in the hollow of the ring structure. In another example, as shown in example b or example d of FIG. 8, the first electrode block and the second electrode block can be distributed side by side (or can also be understood as left and right distribution) in the plane where the second electrode layer 04 is located. In another example, as shown in example c of FIG. 8, the first electrode block and the second electrode block can be in a special shape (for example, the first electrode block is a matrix, and the second electrode block is an irregular polygon surrounding the first electrode block). In addition, the arrangement of the first electrode block and the second electrode block in the second electrode layer 04 is also related to the area size of the two electrode blocks, and in actual application, the first electrode block and the second electrode block can also be arranged in other ways, which are not limited in the present embodiment.

[0201] In addition, as shown in FIG. 9, the present application also provides an ultrasonic transducer 20, which comprises a controller 201 and an ultrasonic transducing module 00. Wherein, the ultrasonic transducing module 00 can refer to the ultrasonic transducing module 00 shown in the foregoing FIG. 3, FIG. 4A or FIG. 4B, which will not be repeated here. The first electrode layer 02 and the second electrode layer 04 contained in the ultrasonic transducing module 00 are electrically connected with the controller 201. Specifically, the controller 201 is configured to provide a first electric signal to the ultrasonic transducing module 00; and the ultrasonic transducing module 00 is configured to output a transmitting sound wave based on the first electric signal. The frequency of the transmitting sound wave can be the aforementioned first resonant frequency, or can be the aforementioned second resonant frequency. In addition, in a scene with low sensitivity requirement, the frequency of the transmitting sound wave can also be a certain frequency near the first resonant frequency, can also be a certain frequency near the second resonant frequency, and can also be a certain frequency between the first resonant frequency and the second resonant frequency. If the frequency of the transmitting sound wave is the first resonant frequency, the transmitting sound wave can be understood as the first sound wave (i.e. the sound wave with the first resonant frequency) introduced in the foregoing embodiments, at this time, the ultrasonic transducer 20 resonates at the first resonant frequency; if the frequency of the transmitting sound wave is the second resonant frequency, the transmitting sound wave can be understood as the second sound wave (i.e. the sound wave with the second resonant frequency) introduced in the foregoing embodiments, at this time, the ultrasonic transducer 20 resonates at the second resonant frequency. The present embodiment does not limit the frequency of the transmitting sound wave.

[0202] Optionally, the ultrasonic transducing module 00 is further configured to receive a reflected sound wave and provide a second electrical signal based on the reflected sound wave to the controller 201; and the controller 201 is configured to receive the second electrical signal. For example, the reflected sound wave is a sound wave reflected from an interface where the emitted sound wave reaches the measured tissue (e.g., a finger, a palm, etc.). Due to the difference in acoustic impedance between air in the valleys and tissue in the ridges of the finger, the reflection rates of the sound wave at the valleys and the ridges are different, resulting in different signal strengths of the reflected sound wave. Therefore, the valleys and ridges of the biological tissue can be identified by detecting the signal strengths of the reflected sound wave at different positions.

[0203] In one possible implementation, the ultrasonic transducer 20 includes a switch circuit and an inductor, and the second electrode layer 04 in the ultrasonic transducing module 00 includes a first electrode block and a second electrode block, the first electrode block and the first electrode layer form a first capacitor, the second electrode block and the first electrode layer form a second capacitor, the second capacitor is connected in series with the switch circuit, the second capacitor and the switch circuit are connected in parallel with the first capacitor, and the inductor is connected in series with the parallel-connected first capacitor and second capacitor.

[0204] The controller 201 is specifically configured to control the switch circuit to be closed, so that the first electrical signal provided to the ultrasonic transducing module 00 is located in a first frequency band; or the controller 201 is specifically configured to control the switch circuit to be opened, so that the first electrical signal provided to the ultrasonic transducing module 00 is located in a second frequency band. Optionally, the frequency of the first frequency band is greater than the frequency of the second frequency band.

[0205] In one possible implementation, the ultrasonic transducer 20 includes a first switch circuit and a second switch circuit, and the second electrode layer 04 in the ultrasonic transducing module 00 includes a first electrode block and a second electrode block, the first electrode block and the first electrode layer form a first capacitor, the second electrode block and the first electrode layer form a second capacitor, the first capacitor is connected in series with the first switch circuit, the second capacitor is connected in series with the second switch circuit, the series-connected first capacitor and first switch circuit are connected in parallel with the series-connected second capacitor and second switch circuit, and the inductor is connected in series with the parallel-connected first capacitor and second capacitor.

[0206] The controller 201 is specifically configured to control the first switch circuit to be closed and the second switch to be opened, so that the first electrical signal provided to the ultrasonic transducing module 00 is located in a third frequency band; or,

[0207] The controller 201 is specifically configured to control the second switch circuit to be closed and the first switch circuit to be opened, so that the first electrical signal provided to the ultrasonic transducing module 00 is located in a fourth frequency band.

[0208] In this embodiment, the controller 201 in the ultrasonic transducer 20 can switch between two frequencies by controlling the switching circuit, which is conducive to the application of the ultrasonic transducer 20 in different frequency scenarios. For example, in a fingerprint detection scenario, the ultrasonic transducer 20 can be compatible with display screens of different resonant frequencies. For another example, in a medical detection scenario, the ultrasonic transducer 20 can detect multi-level biological information by adjusting the working frequency, thereby improving the detection range.

[0209] In addition, the present application also provides an ultrasonic detection device. As shown in FIG. 10, the ultrasonic detection device includes the ultrasonic transducer 20 and the penetrating layer 30 covering the ultrasonic transducing module 00. The transmitting sound waves emitted by the ultrasonic transducing module 00 and the reflected sound waves received by the ultrasonic transducing module 00 all pass through the penetrating layer 30. For example, the penetrating layer 30 is a display screen, a glass layer or a metal layer.

[0210] Optionally, the ultrasonic detection device further includes the matching layer 40, which is used to connect the penetrating layer 30 and the ultrasonic transducing module 00. The transmitting sound waves pass through the ultrasonic transducing module 00, the matching layer 40 and the penetrating layer 30 in sequence, and the reflected sound waves pass through the penetrating layer 30, the matching layer 40 and the ultrasonic transducing module 00 in sequence. For example, the matching layer 40 can be a layer of adhesive (for example, a nonconductive adhesive (NCA) layer) as a bonding layer, which is attached between the ultrasonic transducer 20 and the penetrating layer 30 by using a gluing process. In addition, the matching layer 40 can also be a composite stack composed of a metal layer and an adhesive layer (for example, a composite stack composed of pressure sensitive adhesives (PSA) / copper (Cu) / PSA), which is attached between the ultrasonic transducer 20 and the penetrating layer 30 by using a gluing and silk printing process.

[0211] In addition, the present application also provides a terminal, which includes an image processing module and the aforementioned ultrasonic detection device. The image processing module is connected with the controller of the ultrasonic detection device, and the image processing module can obtain the second signal from the controller, and then generate an image based on the second electrical signal, which is the signal generated by the reflected sound waves received by the ultrasonic detection device.

[0212] Optionally, the terminal further includes an image recognition module, which is used to compare the image generated by the image processing module with a stored image. For example, the image processing module generates a fingerprint, and the image recognition module compares the generated fingerprint with a stored fingerprint, thereby realizing the recognition of the fingerprint.

[0213] Exemplarily, the terminal can be a device or apparatus having a biometric feature detection function. For example, a device that can detect a fingerprint, palm print or handprint of a hand. For example, the terminal can be an electronic device such as a mobile phone, a tablet computer, a notebook computer, an e-reader, a personal computer (PC), a personal digital assistant (PDA), a desktop display, a game device, a smart wearable product (for example, a smart watch, a smart bracelet, smart jewelry), a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a drone, a bank automatic teller machine, or the like; or, the electronic device can be a home device such as a smart door lock, a television, a remote controller, a refrigerator, a charging household small appliance, or the like; or, the electronic device can be a vehicle-mounted device such as a vehicle-mounted navigator, a car door handle, an engine ignition, or the like. The electronic device can be an electronic device having a display function, or can be an electronic device without a display function, and the embodiments of the present application are not limited in this regard.

[0214] Exemplarily, the terminal can also be a medical terminal for detecting deep biological tissues. For example, an ultrasonic imaging instrument, and the like.

[0215] Exemplarily, the terminal can also be a device or apparatus in an industrial ultrasonic detection scenario. For example, an ultrasonic range finder, an ultrasonic flowmeter, and the like.

[0216] It should be understood that, in various embodiments of the present application, the size of the sequence number of each process described above does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0217] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the system, apparatus and unit described above can refer to the corresponding processes in the foregoing method embodiments, which will not be described herein again.

Claims

An ultrasonic transducer module, characterized by The application relates to an ultrasonic transducer module. The substrate layer, the first electrode layer, the piezoelectric layer, the second electrode layer and the at least one protective layer are arranged in sequence. The first sub-module comprises the piezoelectric layer, the second electrode layer and the at least one protective layer, and the sum of the first parameters of the stacked layers in the first sub-module is a / 4, wherein a is a positive odd number. The second sub-module comprises the substrate layer and the first electrode layer, and the sum of the first parameters of the stacked layers in the second sub-module is b / 2, wherein b is a positive integer. The first parameter of any stacked layer in the ultrasonic transducer module is the ratio of the thickness of the stacked layer to the wavelength of a first sound wave in the stacked layer when the first sound wave is transmitted in the stacked layer, and the frequency of the first sound wave is the resonant frequency of the first sub-module and the second sub-module. The ultrasonic transducer module of claim 1, wherein The sum of the second parameters of the substrate layer, the first electrode layer, the piezoelectric layer, the second electrode layer and the at least one protective layer is c / 2, wherein c is a positive integer. The ultrasonic transducer module according to claim 1 or 2, characterized in that The second resonant frequency and the first resonant frequency are in the ratio of d, wherein 0.5 < d < 0.75, the first resonant frequency is the resonant frequency of the first sub-module and the second sub-module, and the second resonant frequency is the resonant frequency of the ultrasonic transducer module. The ultrasonic transducer module according to any one of claims 1 to 3, characterized in that The acoustic pressure reflectivity of the acoustic boundary between the piezoelectric layer and the substrate layer is e, wherein 20% < |e| < 80%. The ultrasonic transducer module according to any one of claims 1 to 4, characterized in that The ratio of the acoustic impedance of the piezoelectric layer to the acoustic impedance of the substrate layer is less than 0.

5. The ultrasonic transducer module according to any one of claims 1 to 5, characterized in that The ratio of the acoustic impedance of the substrate layer to the acoustic impedance of a first adjacent medium is greater than 2, and the first adjacent medium is the adjacent medium on the side of the substrate layer away from the piezoelectric layer. The ultrasonic transducer module according to claim 6, characterized in that The at least one protective layer comprises a first protective layer and a second protective layer, the first protective layer is connected to the side of the second electrode layer away from the piezoelectric layer, the second protective layer is connected to the side of the first protective layer away from the second electrode layer, and the material of the first protective layer is different from that of the second protective layer. The ultrasonic transducer module according to claim 6 or 7, characterized in that The ratio of the acoustic impedance of the second protective layer to the acoustic impedance of a second adjacent medium is greater than 2, and the second adjacent medium is the adjacent medium on the side of the second protective layer away from the first protective layer. The ultrasonic transducer module according to any one of claims 1 to 5, characterized in that The material of the first protective layer comprises glue, and the material of the second protective layer comprises metal. The at least one protective layer is one protective layer, the protective layer is connected to the side of the second electrode layer away from the piezoelectric layer, the ratio of the acoustic impedance of the protective layer to the acoustic impedance of a second adjacent medium is greater than 2, and the second adjacent medium is the adjacent medium on the side of the protective layer away from the second electrode layer. The ultrasonic transducer module according to any one of claims 1 to 9, characterized in that The second electrode layer comprises at least two electrode blocks, each of the electrode blocks forms a capacitor with the first electrode layer, at least one of the capacitors, an inductor connected with the capacitor and at least one switching circuit are used to form an oscillation circuit, and the number of electrode blocks accessed to the oscillation circuit is controlled by switching. The ultrasonic transducer module of claim 10, wherein The second electrode layer comprises a first electrode block and a second electrode block, and areas of the first electrode block and the second electrode block satisfy the following formula: S1 / (S2+S1) = (f2 / f1) 2 ; Wherein, S1 is the area of the first electrode block, S2 is the area of the second electrode block, f1 is the first resonant frequency, and f2 is the second resonant frequency. The ultrasonic transducer module of claim 10, wherein The second electrode layer comprises a first electrode block and a second electrode block, and areas of the first electrode block and the second electrode block satisfy the following formula: S1 / S2 = (f2 / f1) 2 ; Wherein, S1 is the area of the first electrode block, S2 is the area of the second electrode block, f1 is the first resonant frequency, and f2 is the second resonant frequency. An ultrasonic transducer, characterized by The ultrasonic transducer comprises: A controller and the ultrasonic transducer module of any one of claims 1 to 12, the first electrode layer and the second electrode layer are electrically connected with the controller; The controller is configured to provide a first electrical signal to the ultrasonic transducer module; The ultrasonic transducer module is configured to output a transmitting acoustic wave based on the first electrical signal. The ultrasonic transducer of claim 13, wherein The ultrasonic transducer module is further configured to receive a reflected acoustic wave and provide a second electrical signal to the controller based on the reflected acoustic wave; The controller is configured to receive the second electrical signal. The ultrasonic transducer according to claim 13 or 14, characterized in that The ultrasonic transducer further comprises a switching circuit and an inductor; the second electrode layer in the ultrasonic transducer module comprises a first electrode block and a second electrode block, the first electrode block forms a first capacitor with the first electrode layer, the second electrode block forms a second capacitor with the first electrode layer, the second capacitor is connected in series with the switching circuit, the second capacitor and the switching circuit are connected in parallel with the first capacitor, and the inductor is connected in series with the first capacitor and the second capacitor in parallel; The controller is specifically configured to control the switching circuit to be open, the first capacitor and the inductor are connected in series, the first capacitor and the inductor form a first oscillation circuit, and the working frequency of the first oscillation circuit is located in a first frequency band; or The controller is specifically configured to control the switching circuit to be closed, the first capacitor and the second capacitor in parallel and the inductor are connected in series, the first capacitor, the second capacitor and the inductor form a second oscillation circuit, and the working frequency of the second oscillation circuit is located in a second frequency band. The ultrasonic transducer of claim 15, wherein The first frequency band comprises a first resonant frequency, the second frequency band comprises a second resonant frequency, and the first capacitor is connected in parallel with a third capacitor; Capacitance values of the first capacitor, the second capacitor and the third capacitor satisfy the following formula: (C1+C3) / (C2+C1+C3) = (f2 / f1) 2 ; Wherein, C1 is the capacitance value of the first capacitor, C2 is the capacitance value of the second capacitor, C3 is the capacitance value of the third capacitor, f1 is the first resonant frequency, and f2 is the second resonant frequency. The ultrasonic transducer according to claim 13 or 14, characterized in that The ultrasonic transducer further comprises a first switch circuit, a second switch circuit and an inductor; the second electrode layer in the ultrasonic transducer module comprises a first electrode block and a second electrode block, the first electrode block and the first electrode layer form a first capacitor, the second electrode block and the first electrode layer form a second capacitor, the first capacitor is connected in series with the first switch circuit, the second capacitor is connected in series with the second switch circuit, the first capacitor and the first switch circuit connected in series are connected in parallel with the second capacitor and the second switch circuit connected in series, and the inductor is connected in series with the first capacitor and the second capacitor connected in parallel; The controller is specifically configured to control the first switch circuit to be closed and the second switch circuit to be opened, the first capacitor and the inductor are connected in series, the first capacitor and the inductor form a third oscillation circuit, and the working frequency of the third oscillation circuit is located in a third frequency band; or, The controller is specifically configured to control the second switch circuit to be closed and the first switch circuit to be opened, the second capacitor and the inductor are connected in series, the second capacitor and the inductor form a fourth oscillation circuit, and the working frequency of the fourth oscillation circuit is located in a fourth frequency band. The ultrasonic transducer of claim 17, wherein The third frequency band comprises a first resonant frequency, and the fourth frequency band comprises a second resonant frequency; and the first capacitor is connected in parallel with a fourth capacitor. The capacitance value of the first capacitor, the capacitance value of the second capacitor and the capacitance value of the fourth capacitor satisfy the following formula: (C1+C4) / (C2+C4) = (f2 / f1) 2 ; Wherein, the C1 is the capacitance value of the first capacitor, the C2 is the capacitance value of the second capacitor, the C4 is the capacitance value of the fourth capacitor, the f1 is the first resonant frequency, and the f2 is the second resonant frequency. An ultrasonic testing device characterized by The ultrasonic detection device comprises: The ultrasonic transducer of any one of claims 17 to 18, and a penetrating layer covering the ultrasonic transducer module; The transmitted sound wave and the reflected sound wave both pass through the penetrating layer. The ultrasonic testing device according to claim 19, characterized in that The penetrating layer is a display screen, a glass layer or a metal layer. The ultrasound detection apparatus according to claim 19 or 20, characterized in that The ultrasonic detection device further comprises a matching layer for connecting the penetrating layer and the ultrasonic transducer module, the transmitted sound wave sequentially passes through the ultrasonic transducer module, the matching layer and the penetrating layer, and the reflected sound wave sequentially passes through the penetrating layer, the matching layer and the ultrasonic transducer module. A terminal, characterized by comprising: The terminal comprises: The image processing module and the ultrasonic detection device of any one of claims 19 to 21; The image processing module is configured to generate an image based on a second electric signal, the second electric signal being a signal generated by the reflected sound wave received by the ultrasonic detection device.

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