A piezoelectric micromachined underwater acoustic sensor, array and underwater acoustic imaging system

Abstract

The application provides a piezoelectric micromechanical underwater acoustic sensor, an array and an underwater acoustic imaging system, and belongs to the underwater detection field. The problems that a traditional piezoelectric ceramic and an optical fiber sensor are difficult to meet the space constraint of a small-sized system and a MEMS sensor is restricted by narrow bandwidth and low sensitivity caused by inherent resonance characteristics are solved. The sensor comprises a substrate, a plurality of sensitive unit components and a protective layer. The plurality of sensitive unit components are arranged on the substrate to form an array. The protective layer covers the surface of the array. The sensitive unit component comprises a reference sensitive unit and a compensation sensitive unit. The reference sensitive unit and the compensation sensitive unit are different in size, and the resonance peaks of the sensitivity curves of the reference sensitive unit and the compensation sensitive unit are coupled with each other. It is mainly used in high-precision marine surveying and mapping, fish monitoring and the like.

Description

Technical Field

[0001] The present invention belongs to the field of underwater detection, and in particular relates to a piezoelectric micro-mechanical underwater acoustic sensor, an array and an underwater acoustic imaging system. Background Art

[0002] Underwater detection and imaging technology is a core method for marine resource exploration, seabed topography mapping, and underwater target identification. Its core component, the sonar system, is rapidly developing towards miniaturization and intelligence. As the core transducer unit of the sonar system, the sensor plays the key role in converting acoustic signals into electrical signals. Its performance directly determines the system's detection accuracy and imaging resolution. Current mainstream underwater acoustic sensor technologies mainly include the following three solutions:

[0003] Piezoelectric ceramic sensors use ferroelectric materials such as lead zirconate titanate (PZT) to generate charge signals through the polarization effect under acoustic pressure. This approach offers the advantages of high sensitivity and mature fabrication processes. However, limitations include poor ceramic material consistency and bulk, making it difficult to meet the requirements of array integration and susceptible to interference from the complex underwater electromagnetic environment. Fiber optic sensors achieve detection by modulating the optical properties of fiber Bragg gratings or interferometers with acoustic waves. Their electromagnetic interference immunity and distributed measurement capabilities show potential for deep-sea exploration. However, these solutions rely on precision optical components, resulting in bottlenecks such as high manufacturing costs and complex signal demodulation, hindering their widespread adoption in miniaturized devices. Microelectromechanical systems (MEMS) sensors, which use micro-nanofabrication techniques to fabricate vibrating structures, generate electrical signals through acoustically induced mechanical deformation. They are characterized by small size, low power consumption, and high batch consistency. While MEMS technology offers new opportunities for sonar miniaturization, its sensitivity and dynamic range are limited by the mechanical response characteristics of micron-scale structures, resulting in difficulties in achieving greater detection distance and imaging resolution.

[0004] Current technical solutions generally face a contradiction between performance and integration: traditional piezoelectric ceramic and fiber optic sensors, while highly sensitive, struggle to meet the spatial constraints of miniaturized systems; while MEMS sensors, while miniaturized, are constrained by their inherent resonant characteristics, resulting in narrow bandwidth and low sensitivity. In the field of underwater acoustic imaging, insufficient sensor bandwidth limits system resolution, while low sensitivity directly impacts the ability to detect long-range targets. Therefore, achieving broadband, highly sensitive acoustic wave detection through innovative structural design while ensuring device miniaturization has become a key challenge in underwater acoustic sensing technology that urgently needs to be overcome. Summary of the Invention

[0005] In view of this, the present invention aims to propose a piezoelectric micromechanical underwater acoustic sensor, array and underwater acoustic imaging system to solve the problems that traditional piezoelectric ceramics and optical fiber sensors are difficult to meet the spatial constraints of miniaturized systems and the narrow bandwidth and low sensitivity of MEMS sensors due to their inherent resonant characteristics.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A piezoelectric micromechanical underwater acoustic sensor, comprising:

[0008] substrate, multiple sensitive unit components and protective layers;

[0009] The plurality of sensitive unit components are arranged on the substrate to form an array; the protective layer covers the surface of the array;

[0010] Each sensitive unit assembly includes at least one reference sensitive unit and at least one compensation sensitive unit, wherein the reference sensitive unit and the compensation sensitive unit have different sizes, and the resonance peaks of the sensitivity curves of the reference sensitive unit and the compensation sensitive unit are coupled to each other;

[0011] The resonant frequency of the sensitive unit is between 50kHz and 3000kHz. Each sensitive unit includes an upper electrode, a piezoelectric layer and a lower electrode. When sound waves act on the piezoelectric layer, polarization occurs and charges are generated on the surface of the upper electrode and the lower electrode, and electrical signals are output through the upper electrode and the lower electrode.

[0012] Furthermore, a preferred method is proposed, in which the reference sensitive unit and the compensation sensitive unit are capsule-shaped structures, and the capsule-shaped structure is composed of a rectangular diaphragm and a semi-elliptical or semi-circular diaphragm; the short side of the rectangular diaphragm is equal to the short axis of the semi-ellipse or the diameter of the semicircle, which is used to compensate for the difference between the odd-order peaks and even-order troughs of the rectangular diaphragm sensitivity curve.

[0013] Furthermore, a preferred embodiment is proposed, in which the reference sensitive unit and the compensation sensitive unit have different aspect ratios k, and the aspect ratio k is 4-6.

[0014] Furthermore, a preferred embodiment is proposed, in which the upper electrodes of the reference sensitive unit and the compensation sensitive unit include an inner electrode and an outer electrode; and differential reception is adopted for the inner electrode and the outer electrode when receiving sound waves.

[0015] Furthermore, a preferred embodiment is proposed, in which the reference sensitive units and the compensation sensitive units are distributed on the substrate in a centrally symmetrical manner.

[0016] Furthermore, a preferred embodiment is proposed, in which the sensitive unit components are arranged in a single column or multiple columns on the substrate, and the sensitive unit components in adjacent columns are staggered.

[0017] Based on the same inventive concept, the present invention also proposes a piezoelectric micro-mechanical underwater acoustic sensor array, which includes a plurality of piezoelectric micro-mechanical underwater acoustic sensors, a substrate and an acoustic impedance matching layer; the piezoelectric micro-mechanical underwater acoustic sensors are arranged on the substrate in an array, and the distance between adjacent sensors is half the wavelength or full wavelength of the center frequency of the sound wave; the acoustic impedance matching layer covers the surface of the sensor array, and the acoustic impedance matching layer includes at least one layer of acoustic impedance stack, each layer has an acoustic impedance value between the substrate and the external medium, and a thickness of the acoustic wave wavelength. Nλ / 4, where N is a non-zero positive integer and λ is the wavelength of the sound wave propagating in the stack.

[0018] Furthermore, a preferred embodiment is proposed, in which the acoustic impedance value of the middle laminate of the acoustic impedance matching layer is the arithmetic square root of the acoustic impedance values ​​of the two adjacent laminates.

[0019] Furthermore, a preferred embodiment is proposed, in which the piezoelectric micromechanical underwater acoustic sensors in the matrix are arranged in a linear array or a planar array, and two adjacent columns of piezoelectric micromechanical underwater acoustic sensors are staggered.

[0020] Based on the same inventive concept, the present invention also proposes an underwater imaging system, which includes: a piezoelectric micromechanical underwater acoustic sensor array, a transmitting transducer, a processor and a display; the transmitting transducer is connected to the processor, and is used to receive a control signal sent by the processor and transmit sound waves to the target area according to the control signal; the piezoelectric micromechanical underwater acoustic sensor array is connected to the processor, and is used to receive the sound waves reflected back from the target area according to the receiving signal sent by the processor, thereby obtaining echo data; the processor is used to control signal transmission and reception, process echo data and generate images; the display is connected to the processor, and is used to display imaging results.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention breaks through the inherent resonant frequency limitation of a single sensitive unit through the modal coupling design of sensitive unit components of different sizes (a capsule-like structure of the reference unit and the compensation unit). By utilizing the complementary characteristics of the resonance peaks of the sensitivity curves of units of different sizes, the sensor receiving bandwidth is significantly broadened (by not less than 50%). At the same time, multi-order resonant energy superposition is achieved through array arrangement, which comprehensively improves the sensitivity and dynamic range, overcoming the technical bottlenecks of narrow bandwidth and low sensitivity of traditional MEMS sensors.

[0023] 2. The present invention is based on a staggered array of sensitive units (such as linear array / area array) and an intermediate layer design of a multi-layer acoustic impedance matching structure, which effectively suppresses acoustic coupling crosstalk between adjacent units, reduces acoustic reflection loss at the dielectric interface, and more than doubles the acoustic wave transmission efficiency: combined with a differential electrode receiving mode, it eliminates common-mode electromagnetic interference, and improves the signal-to-noise ratio (SNR) by more than 3dB compared to traditional piezoelectric ceramic solutions, making it suitable for complex underwater electromagnetic environments.

[0024] 3. The present invention adopts MEMS technology to prepare micron-scale sensitive units (silicon-based cavity + thin film piezoelectric layer), combined with the compact layout of the capsule-like structure (optimized aspect ratio k=4-6), to achieve multi-sensitive component array integration within a unit area of ​​≤5mm². The device volume is more than halved compared to traditional piezoelectric ceramic solutions, and the array expansion is flexible (supporting linear array, area array and staggered arrangement), meeting the space constraints of miniaturized equipment such as underwater robots and portable sonars.

[0025] 4. The protective layer and symmetrical vibration design (center-symmetrically distributed sensitive units) of the present invention reduce the impact of water flow impact and mechanical deformation on sensor performance, ensuring long-term stable operation of the device in complex underwater environments.

[0026] 5. Based on the broadband characteristics, the present invention improves the axial resolution of the underwater imaging system to the millimeter level. The array's beamforming technology further optimizes target positioning accuracy and supports medium and long-range target detection. It is significantly superior to existing MEMS underwater acoustic sensors and is suitable for scenarios such as high-precision ocean mapping and fish monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 This is a schematic structural diagram of a piezoelectric micromechanical underwater acoustic sensor according to the present invention;

[0029] Figure 2 This is a top view of the planar structure of the piezoelectric micromechanical underwater acoustic array sensor described in the present invention;

[0030] Figure 3 This is a schematic plan view of the composition structure of the capsule-type sensitive unit described in the present invention;

[0031] Figure 4 Schematic diagram of a plane of a capsule-like sensitive unit with different aspect ratios (k) according to the present invention;

[0032] Figure 5 This is a schematic diagram of an independent sensitivity curve of a single sensitive unit according to the present invention;

[0033] Figure 6 A schematic diagram of a sensitivity curve after a reference sensitive unit and two compensation units are coupled to each other according to the present invention;

[0034] Figure 7 This is a structural diagram of another piezoelectric micro-mechanical underwater acoustic array sensor according to the present invention;

[0035] Figure 8 This is a front view of another piezoelectric micro-mechanical underwater acoustic array sensor according to the present invention;

[0036] Figure 9 This is a structural diagram of the parallel piezoelectric micro-mechanical underwater acoustic array sensor described in the present invention;

[0037] Figure 10 This is a structural diagram of the staggered piezoelectric micromechanical underwater acoustic array sensor described in the present invention;

[0038] Figure 11 This is a structural diagram of the symmetrical piezoelectric micro-mechanical underwater acoustic array sensor described in the present invention;

[0039] Figure 12 Schematic diagram of the expansion of the sensor of the present invention along the x-direction or the y-direction, where d represents the distance between adjacent array elements and N represents the number of linear array elements;

[0040] Figure 13 Schematic diagram of the expansion of the sensor of the present invention along the x-direction and the y-direction, d represents the spacing between adjacent array elements along the x-direction or the y-direction, w represents the spacing between adjacent array elements along the y-direction or the x-direction, N represents the number of array elements in the area array along the x-direction or the y-direction, and M represents the number of array elements in the area array along the y-direction or the x-direction;

[0041] Figure 14 This is a schematic structural diagram of an underwater imaging system according to the present invention;

[0042] In the picture:

[0043] 401-sensitive unit assembly, 402-substrate, 403-first protective layer, 404-reference sensitive unit, 405-compensation sensitive unit, 501-first substrate, 502-first lower electrode, 503-first piezoelectric layer, 504-first upper electrode, 505-rectangular diaphragm, 506-elliptical diaphragm, 507-circular diaphragm, 801-second substrate, 802-cavity, 803-structural layer, 804-second lower electrode, 805-second piezoelectric layer, 806-external electrode, 807-inner electrode, 808-second protective layer, 901-acoustic impedance matching layer, 902-transmitting transducer, 903-underwater acoustic sensor, 904-underwater acoustic sensor array. DETAILED DESCRIPTION

[0044] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features therein can be combined with each other in the absence of conflict, and the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0045] Embodiment 1: A piezoelectric micromechanical underwater acoustic sensor according to this embodiment includes:

[0046] substrate, multiple sensitive unit components and protective layers;

[0047] The plurality of sensitive unit components are arranged on the substrate to form an array; the protective layer covers the surface of the array;

[0048] Each sensitive unit assembly includes at least one reference sensitive unit and at least one compensation sensitive unit, wherein the reference sensitive unit and the compensation sensitive unit have different sizes, and the resonance peaks of the sensitivity curves of the reference sensitive unit and the compensation sensitive unit are coupled to each other;

[0049] The resonant frequency of the sensitive unit is 50kHz-3000kHz. Each sensitive unit includes an upper electrode, a piezoelectric layer and a lower electrode. When the sound wave acts, the piezoelectric layer is polarized and generates charges on the surface of the upper electrode and the lower electrode, and outputs electrical signals through the upper electrode and the lower electrode.

[0050] The underwater acoustic sensor proposed in this embodiment utilizes a combination of reference and compensating sensitive units of varying sizes. This design leverages the modal coupling effect of their resonant peaks to effectively compensate for the peak-to-trough variations in the sensitivity curve of a single sensitive unit, significantly broadening the receiving bandwidth (for example, covering a range of 50 kHz to 3000 kHz). Furthermore, the synergistic effect of multiple sensitive units in the array enhances overall receiving sensitivity, addressing the limited dynamic range of traditional MEMS sensors.

[0051] Implementation method 2. This implementation method further limits the piezoelectric micromechanical underwater acoustic sensor described in implementation method 1. The reference sensitive unit and the compensation sensitive unit are capsule-shaped structures, and the capsule-shaped structure is composed of a rectangular diaphragm and a semi-elliptical or semi-circular diaphragm; the short side of the rectangular diaphragm is equal to the short axis of the semi-ellipse or the diameter of the semicircle, which is used to compensate for the difference between the odd-order peaks and even-order troughs of the rectangular diaphragm sensitivity curve.

[0052] Specifically, the reference sensitive unit and the compensation sensitive unit are both capsule-like structures composed of a combination of a rectangular diaphragm and an elliptical diaphragm or a combination of a rectangular diaphragm and a circular diaphragm, and have different sizes, wherein the short side length of the rectangular diaphragm serves as the short axis of the elliptical diaphragm or the diameter of the circular diaphragm, and the semi-elliptical or semi-circular diaphragm connected to the short side of the rectangular diaphragm is used to compensate for the excessive sensitivity difference between the odd-order peaks and even-order troughs on the sensitivity curve of the rectangular diaphragm.

[0053] Implementation method three: This implementation method further limits the piezoelectric micromechanical underwater acoustic sensor described in implementation method one. The reference sensitive unit and the compensation sensitive unit have different aspect ratios k, and the aspect ratio k is 4-6.

[0054] In this embodiment, k is the ratio of the major axis to the minor axis of the centrosymmetric cross-sectional shape of the sensitive unit. If k is too large, the high-order resonant frequency of the sensitive unit will drop significantly, resulting in uneven energy distribution and a decrease in overall bandwidth. If k is too small, the resonant frequencies of the sensitive units will differ significantly, affecting the coupling effect between modes. In this embodiment, the aspect ratio k is preferably 4-6 to achieve a sufficiently wide bandwidth effect.

[0055] Implementation method 4: This implementation method further limits the piezoelectric micromechanical underwater acoustic sensor described in implementation method 1. The upper electrodes of the reference sensitive unit and the compensation sensitive unit include an inner electrode and an outer electrode. When receiving sound waves, differential reception is adopted for the inner electrode and the outer electrode.

[0056] In practical applications, the upper electrodes of the reference sensitive unit and the compensation sensitive unit include at least one inner electrode and at least one outer electrode. When receiving sound waves, differential reception is adopted for the at least one inner electrode and the at least one outer electrode, thereby improving receiving sensitivity.

[0057] Embodiment 5: This embodiment further limits the piezoelectric micromechanical underwater acoustic sensor described in embodiment 1, wherein the reference sensitive unit and the compensation sensitive unit are centrally symmetrically distributed on the substrate.

[0058] In practical applications, at least one reference sensitive unit and at least one compensation sensitive unit are distributed on the substrate in a centrally symmetrical manner to achieve symmetrical vibration and broaden the receiving bandwidth.

[0059] Embodiment 6. This embodiment further limits the piezoelectric micromechanical underwater acoustic sensor described in embodiment 1. The sensitive unit components are arranged in a single row or multiple rows on the substrate, and the sensitive unit components in adjacent rows are staggered.

[0060] Implementation method 7. This implementation method describes a piezoelectric micro-mechanical underwater acoustic sensor array, which includes a plurality of piezoelectric micro-mechanical underwater acoustic sensors, a substrate, and an acoustic impedance matching layer; the piezoelectric micro-mechanical underwater acoustic sensors are arranged in an array on the substrate, and the distance between adjacent sensors is half the wavelength or full wavelength of the center frequency of the sound wave to reduce array element crosstalk and suppress side lobes; the acoustic impedance matching layer covers the surface of the sensor array to improve the efficiency of sound wave transmission and enhance the sensitivity of collecting sound wave signals. The acoustic impedance matching layer includes at least one layer of acoustic impedance stack, each layer has an acoustic impedance value between the substrate and the external medium, and a thickness of the sound wave wavelength. Nλ / 4, where N is a non-zero positive integer and λ is the wavelength of the sound wave propagating in the stack.

[0061] Implementation 8: This implementation further limits the piezoelectric micromechanical underwater acoustic sensor array described in Implementation 7, wherein the acoustic impedance value of the middle layer of the acoustic impedance matching layer is the arithmetic square root of the acoustic impedance values ​​of the two adjacent layers.

[0062] Implementation method 9. This implementation method further limits the piezoelectric micromechanical underwater acoustic sensor array described in implementation method 7. The piezoelectric micromechanical underwater acoustic sensors in the array are arranged in a linear array or a planar array, and two adjacent columns of piezoelectric micromechanical underwater acoustic sensors are staggered.

[0063] The microsensors in each adjacent column of the array are staggered, which can reduce the acoustic coupling crosstalk between adjacent microsensors and improve the signal-to-noise ratio.

[0064] Implementation Method 10: See Figure 14 This embodiment describes an underwater imaging system, comprising a piezoelectric micromachined underwater acoustic sensor array 904, a transmitting transducer 902, a processor, and a display. The transmitting transducer 902 is connected to the processor and configured to receive control signals from the processor and transmit sound waves toward a target area in response to the control signals. The piezoelectric micromachined underwater acoustic sensor array 904 is connected to the processor and configured to receive sound waves reflected from the target area in response to receiving signals from the processor, thereby acquiring echo data. The processor is configured to control signal transmission and reception, process echo data, and generate images. The display is connected to the processor and configured to display imaging results.

[0065] The processor includes a signal control module, a signal transmission / reception and acquisition module, and a signal processing module. The signal control module controls the operation of the signal transmission and reception module, the signal processing module, and the data transmission unit. The transmission module generates the electrical signal required to drive the transmitting transducer to emit sound waves. The receiving and acquisition module implements gain control, amplification, filtering, and AD acquisition of the received acoustic wave signals. The signal processing module implements data synchronization processing, beamforming, data upload and control, and image generation.

[0066] Optionally, an acoustic impedance matching layer 901 and an acoustic lens structure can be added to the front end of the underwater imaging system. The acoustic impedance matching layer is used to match the acoustic impedance difference between the sensor and the medium, improving the efficiency of sound wave transmission; the acoustic lens structure is used to focus the sound waves and increase the signal strength.

[0067] Specifically, using a field-programmable gate array (FPGA) as a control chip, signal control and processing can be performed. Through switch control, a pulse generator generates a pulse excitation wave of a certain frequency, which stimulates the transmitting transducer to convert electrical energy into an acoustic wave signal, which is then transmitted to the current area. The transmitted acoustic wave propagates to the target object, where it is reflected. The echo signal is then received by the underwater acoustic sensor 903. The underwater acoustic sensor 903 and its base array provided in this application convert acoustic energy into an electrical signal through the positive piezoelectric effect. The signal is processed by the acquisition circuit module and transmitted to the control chip for data processing and image generation.

[0068] Implementation method 11, see Figures 1 to 13 This embodiment provides a specific example of the piezoelectric micro-mechanical underwater acoustic sensor described in the first embodiment, and is also used to explain the second to sixth embodiments. Specifically:

[0069] like Figure 1 FIG2 is a schematic diagram of the structure of a piezoelectric micro-machined underwater acoustic sensor according to this embodiment. The sensor may include multiple sensitive unit components 401, a substrate 402, and a first protective layer 403. Each sensitive component includes at least one reference sensitive unit 404 and at least one compensation sensitive unit 405.

[0070] Specifically, each sensitive unit includes a diaphragm, which can include a structural layer, a lower electrode, a piezoelectric layer, and an upper electrode. When sound waves are transmitted to the sensitive unit, the diaphragm deforms, the piezoelectric layer becomes polarized, and charges are generated on the surfaces of the upper and lower electrodes, outputting electrical signals. This received electrical signal can be used to generate a detection image.

[0071] In this embodiment, the number of reference sensitive units and compensation sensitive units is not limited. Generally, the size of the reference sensitive unit 404 is larger than that of the compensation sensitive unit 405, and the number of the reference sensitive units is less than the number of the compensation sensitive units.

[0072] In practical applications, the reference sensitive unit 404 and the compensation sensitive unit 405 may have different cross-sectional areas; the reference sensitive unit 404 and the compensation sensitive unit 405 may have different thicknesses; the reference sensitive unit 404 and the compensation sensitive unit 405 may have different cross-sectional areas and thicknesses.

[0073] Specifically, for the convenience of introduction, the reference sensitive unit and the compensation sensitive unit are described as an example in which the cross-sectional areas are different.

[0074] Figure 2 This is a top view of a planar structure of a sensor sensitive component in an embodiment of the present application. The sensitive unit includes a first substrate 501, a first lower electrode 502, a first piezoelectric layer 503 and a first upper electrode 504. Specifically, Figure 3 As shown, the reference sensitive unit and the compensation sensitive unit are both capsule-like structures composed of a rectangular diaphragm 505 and an elliptical diaphragm 506, or a rectangular diaphragm 505 and a circular diaphragm 507, and have different sizes, wherein the short side length of the rectangular diaphragm serves as the short axis of the elliptical diaphragm or the diameter of the circular diaphragm, and the semi-elliptical or semi-circular diaphragm connected to the short side of the rectangular diaphragm is used to compensate for the excessive sensitivity difference between the odd-order peaks and the even-order troughs on the sensitivity curve of the rectangular diaphragm.

[0075] In practical applications, the reference sensitive unit and the compensation sensitive unit have different aspect ratios k, where k is the ratio of the major axis a to the minor axis b of the centrosymmetric cross-sectional shape of the sensitive unit. Figure 4 When k is too large, the high-order resonant frequency of the sensitive unit drops too much, and there is uneven energy distribution, resulting in a decrease in the overall bandwidth. When k is too small, the resonant frequencies of the sensitive units differ too much, affecting the coupling effect between modes. The aspect ratio k is preferably 4-6.

[0076] Figure 5 Schematic diagram of the sound pressure sensitivity curves of the first reference unit, the first compensation unit, and the second compensation unit. Figure 6 Schematic diagram of the sound pressure sensitivity curve after the first reference unit, the first compensation unit and the second compensation unit are coupled and compensated with each other. Figure 5The solid line in the middle shows the sensitivity curve of the first reference unit, while the dashed line and dotted line show the sensitivity curves of the first and second compensation units, respectively. The first-order resonance peak of the first reference unit's sensitivity curve overlaps with the trough of the sensitivity curves of the first and second compensation units. The second-order resonance peak of the first reference unit's sensitivity curve also overlaps with the third-order resonance peak of the sensitivity curves of the first and second compensation units. Furthermore, the out-of-band resonance peak of the reference unit is close to the first-order resonance peak of the first and second compensation units, indicating a mutual coupling relationship. Figure 6 It can be seen that after the reference unit and the compensation unit are coupled and compensated with each other, the combined sensing component has a larger receiving bandwidth and comprehensive sensitivity characteristics compared to a single sensitive unit.

[0077] This application provides another sensor structure such as Figure 7 and Figure 8 Specifically, the overall structure of the sensor provided in this application may include a second substrate 801, a cavity 802, a structural layer 803, a second lower electrode 804, a second piezoelectric layer 805, an outer electrode 806, an inner electrode 807, and a second protective layer 808. The upper electrode of each sensitive unit is divided into two parts: an inner electrode 807 and an outer electrode 806, and both the inner electrode 807 and the outer electrode 806 are block electrodes.

[0078] The base and substrate materials are typically silicon wafers, but can also be glass sheets or organic polymers. A cavity is formed in the base through etching, releasing the diaphragm structure, including the substrate, above the cavity. The upper and lower electrodes are used to collect the electrical signals generated by the piezoelectric layer in response to acoustic waves. They can be made of various conductive materials, including metals such as Al, Au, Ag, Pt, and Mo, or piezoelectric polymers such as ITO. Piezoelectric layer materials primarily include AlN and its alloys AlScN, ZnO and its alloys ZnVO, PZT, KNN, PVDF and its copolymers PVEF-Trfe. The protective layer is used for electrical isolation and physical protection and can be made of various waterproof polymers, such as Parylene, PDMS, and polyurethane.

[0079] This application provides a larger-scale array sensor structure based on the above-mentioned sensitive unit components, such as Figures 9 to 11 In the array sensor, the sensitive unit components are distributed in at least one column, and each column includes at least one sensitive unit component; the reference sensitive unit and the compensation sensitive unit in each sensitive unit component are arranged in sequence or symmetrically. Specifically, Figure 9 It shows that multiple sequentially arranged sensitive units are distributed in multiple columns and every two adjacent columns are arranged side by side in the same order; Figure 10It shows that multiple sequentially arranged sensitive units are distributed in multiple columns and every two adjacent columns are staggered in the same order; Figure 11 It shows that after multiple sensitive units are arranged in sequence with mirror symmetry, they are distributed in multiple columns, and every two adjacent columns are arranged in parallel or staggered in the same order; in practical applications, the sensing components can be distributed in one column or in multiple columns.

[0080] On this basis, a larger-scale matrix structure can be realized, where the sensor units are mounted on a substrate to form a matrix, such as Figure 12 and Figure 13 For example, the mounting substrate may be a metal substrate, such as aluminum, copper, iron, stainless steel, etc.; a ceramic substrate, such as aluminum oxide, aluminum nitride, etc.; or a polymer substrate, such as polyimide, epoxy resin, acrylic fiber, etc. Figure 12 、 Figure 13 They are array expansion forms of sensors, specifically, Figure 12 The sensor is extended in the x-direction, and the extension direction can also be in the y-direction; Figure 13 The expansion of the sensor along the x and y directions; usually the characteristic dimension d or w along the x or y expansion direction is less than 1.5 times the wavelength to ensure that the array radiation sound field is not affected by side lobes.

[0081] The specific embodiments of the present invention disclosed above are intended only to help illustrate the present invention. The specific embodiments do not describe all details in detail, nor do they limit the invention to the specific embodiments described. Numerous modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention.

Claims

1. A piezoelectric micromechanical underwater acoustic sensor, characterized in that: The sensor comprises: substrate, multiple sensitive unit components and protective layers; The plurality of sensitive unit components are arranged on the substrate to form an array; the protective layer covers the surface of the array; Each sensitive unit assembly includes at least one reference sensitive unit and at least one compensation sensitive unit, wherein the reference sensitive unit and the compensation sensitive unit have different sizes, and the resonance peaks of the sensitivity curves of the reference sensitive unit and the compensation sensitive unit are coupled to each other; The resonant frequency of the sensitive unit is between 50kHz and 3000kHz. Each sensitive unit includes an upper electrode, a piezoelectric layer and a lower electrode. When an acoustic wave acts on the piezoelectric layer, polarization occurs and charges are generated on the surfaces of the upper electrode and the lower electrode, and an electrical signal is output through the upper electrode and the lower electrode. The reference sensitive unit and the compensation sensitive unit are capsule-like structures, which are composed of a rectangular diaphragm and a semi-elliptical or semi-circular diaphragm; the short side of the rectangular diaphragm is equal to the short axis of the semi-ellipse or the diameter of the semicircle.

2. The piezoelectric micromechanical underwater acoustic sensor according to claim 1, characterized in that: The reference sensitive unit and the compensation sensitive unit have different aspect ratios k, and the aspect ratio k is 4-6.

3. The piezoelectric micromechanical underwater acoustic sensor according to claim 1, characterized in that: The upper electrodes of the reference sensitive unit and the compensation sensitive unit include an inner electrode and an outer electrode; differential reception is adopted for the inner electrode and the outer electrode when receiving sound waves.

4. The piezoelectric micromechanical underwater acoustic sensor according to claim 1, characterized in that: The reference sensitive unit and the compensation sensitive unit are distributed on the substrate in a centrally symmetrical manner.

5. The piezoelectric micromechanical underwater acoustic sensor according to claim 1, characterized in that: The sensitive unit components are arranged in a single row or multiple rows on the substrate, and the sensitive unit components in adjacent rows are staggered.

6. A piezoelectric micro-mechanical underwater acoustic sensor array, characterized in that: The base array is constructed based on the piezoelectric micromechanical underwater acoustic sensor according to claim 1, and the base array includes a plurality of piezoelectric micromechanical underwater acoustic sensors, a substrate and an acoustic impedance matching layer; the piezoelectric micromechanical underwater acoustic sensors are arranged on the substrate in an array, and the distance between adjacent sensors is half the wavelength or full wavelength of the center frequency of the sound wave; the acoustic impedance matching layer covers the surface of the sensor array, and the acoustic impedance matching layer includes at least one layer of acoustic impedance stack, each layer has an acoustic impedance value between the substrate and the external medium, and a thickness of the acoustic wave wavelength Nλ / 4, where N is a non-zero positive integer and λ is the wavelength of the sound wave propagating in the stack.

7. The piezoelectric micro-mechanical underwater acoustic sensor array according to claim 6, characterized in that: The acoustic impedance value of the middle laminate of the acoustic impedance matching layer is the arithmetic square root of the acoustic impedance values ​​of the two adjacent laminates.

8. The piezoelectric micro-mechanical underwater acoustic sensor array according to claim 6, characterized in that: The piezoelectric micro-mechanical underwater acoustic sensors in the matrix are arranged in a linear array or a planar array, and two adjacent rows of piezoelectric micro-mechanical underwater acoustic sensors are staggered.

9. An underwater imaging system, characterized in that: The system is constructed based on the piezoelectric micromechanical underwater acoustic sensor array described in claim 6, and the system includes: a piezoelectric micromechanical underwater acoustic sensor array, a transmitting transducer, a processor and a display; the transmitting transducer is connected to the processor, and is used to receive a control signal sent by the processor and transmit sound waves to the target area according to the control signal; the piezoelectric micromechanical underwater acoustic sensor array is connected to the processor, and is used to receive sound waves reflected back from the target area according to the receiving signal sent by the processor, thereby obtaining echo data; the processor is used to control signal transmission and reception, process echo data and generate images; the display is connected to the processor, and is used to display imaging results.

Images