Resonant holographic sensing acoustic 3d imaging method and image sensor

Abstract

The application discloses a kind of acoustic three-dimensional imaging method and image sensor of resonant holographic sensing, applied to acoustic imaging field, the imaging method utilizes acoustic lens focusing reception target object reflected ultrasonic echo, forms imaging sound field and is imaged in acoustic image sensor surface, the acoustic image sensor is by Helmholtz type microcavity metasurface, RS type laminated MUT unit array and special integrated circuit sequentially laminated and constitutes, and it is arranged in pixelization array, imaging sound field enters corresponding internal microcavity through each surface through hole of metasurface, and it is carried out resonant interference with the reference sound field radiated by the bottom RS type laminated diaphragm, forms holographic sound field and reacts on RS type laminated diaphragm, generates holographic resonance signal, after the signal is peak detection, denoising processing, addressing readout and phase reconstruction, the three-dimensional image of target object ultrasonic echo is formed.The present application can overcome the existing acoustic three-dimensional imaging technology faces the imaging problem of large field of view, high resolution and fast real-time.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of acoustic imaging, and particularly relates to an acoustic three-dimensional imaging method and an image sensor based on resonant holographic sensing. BACKGROUND

[0002] In the field of acoustic imaging such as medical ultrasonic diagnosis and treatment and underwater acoustic sonar detection, most of the current system devices adopt a conventional B-scan imaging system, which obtains the azimuth and distance information of a target by using the pulse echo time of flight, and then generates a two-dimensional azimuth-distance image by scanning, but the imaging effect has problems such as non-intuitive information and difficult understanding. In order to realize intuitive and visual acoustic three-dimensional imaging, people have explored acoustic holographic three-dimensional imaging methods such as direct interference recording of the sound field wave front by using an external reference sound source and virtual interference detection scanning of the sound field wave front. However, due to the lack of a high-resolution, large-array wave front information recording medium, these imaging methods either have a limited detection range due to the array aperture of the transducer, or have reduced imaging real-time performance due to scanning splicing.

[0003] In recent years, researchers have tried to study another form of three-dimensional imaging method, i.e., beamforming three-dimensional imaging, based on a two-dimensional array formed by splicing conventional piezoelectric transducers, combined with pulse time of flight and beamforming algorithms. However, this method has problems such as complex hardware circuit and time-consuming beamforming algorithm. Even if array compression sparsity or a sound lens is used to directly form multiple beams to simplify signal processing, it is still inevitable to cause problems in image quality and imaging real-time performance.

[0004] With the micro-nano manufacturing capabilities of MEMS (Micro-Electro-Mechanical System) and semiconductor technology, CMUT (Capacitive Micromachined Ultrasonic Transducer) and PMUT (Piezoelectric Micromachined Ultrasonic Transducer) can realize large-scale arrays and high integration on a silicon substrate. However, due to the time-domain vibration characteristics of acoustic signals, people have to use a large number of channels to sample the acoustic pressure signals of each array element in the MUT (Micro-Mechanical Ultrasonic Transducer) array in parallel, just like the signal processing method of conventional transducer arrays. Although both can be integrated with an application-specific integrated circuit (ASIC) front end to expand the array size, a large-scale array inevitably has problems such as a large number of pinouts and signal processing. Simplification by using row-column cross addressing and array discrete sparsity is only a compromise between array size and imaging quality and real-time performance.

[0005] Therefore, whether it is conventional acoustic holographic imaging, or recent beamforming imaging, or even MUT array imaging, the problem of real-time imaging with a large field of view and high resolution in acoustic three-dimensional imaging has not been effectively solved. SUMMARY

[0006] Therefore, the present application aims to provide a resonant holographic sensing acoustic three-dimensional imaging method and an image sensor, to solve the problem that it is difficult to realize large field of view, high resolution and real-time imaging in the existing acoustic three-dimensional imaging technology.

[0007] To solve the above technical problems, the present application provides a resonant holographic sensing acoustic three-dimensional imaging method, comprising:

[0008] An ultrasonic sound source is excited to emit ultrasonic waves to irradiate a target object, and an acoustic lens is used to focus and receive ultrasonic echoes reflected by the target object, to form an imaging acoustic field containing intensity distribution and phase distribution, and to be imaged on the surface of an acoustic image sensor; the acoustic image sensor is placed on the image plane focal plane of the acoustic lens, and is used to receive the spatial distribution information of the intensity and phase of the imaging acoustic field; the acoustic image sensor is an array of acousto-electric conversion pixel units provided with a Helmholtz type microcavity super surface on the surface; each structural unit of the Helmholtz type microcavity super surface corresponds to one acousto-electric conversion pixel unit, or corresponds to a plurality of parallelly arranged acousto-electric conversion pixel units;

[0009] The imaging acoustic field enters the corresponding internal microcavity through the surface through hole of each structural unit of the Helmholtz type microcavity super surface in the acoustic image sensor; the bottom of the internal microcavity is composed of a laminated diaphragm of the acousto-electric conversion pixel unit; the laminated diaphragm is provided with a reference diaphragm and a sensing diaphragm; the reference diaphragm and the sensing diaphragm are connected in a stacked manner from top to bottom;

[0010] A reference signal with the same frequency as the ultrasonic echo is applied to the excitation electrode of the reference diaphragm, to cause the reference piezoelectric layer inside the reference diaphragm to resonate and deform, thereby driving the reference diaphragm and the sensing diaphragm to vibrate at the same frequency, and at the same time, radiating a reference acoustic field with the same frequency as the ultrasonic echo into the internal microcavity;

[0011] The reference acoustic field and the imaging acoustic field entering from each surface through hole locally resonate and superimpose in the corresponding internal microcavity, and through interference, convert the intensity information and phase information of the imaging acoustic field into an interference acoustic field amplified by resonance; the interference acoustic fields in each internal microcavity together form a holographic acoustic field of the ultrasonic echo reflected by the target object;

[0012] The holographic acoustic field reacts in each internal microcavity to the laminated diaphragm of each acousto-electric conversion pixel unit, and superimposes with the same frequency vibration excited by the reference signal, to form a holographic resonance, to drive the reference diaphragm and the sensing diaphragm to vibrate together, so that the sensing piezoelectric layer in the sensing diaphragm induces a corresponding resonant holographic signal on the sensing electrode layer.

[0013] Optionally, it comprises:

[0014] The resonant holographic signal is transmitted to a signal processing unit for peak detection and denoising to obtain a preprocessed resonant holographic signal;

[0015] The preprocessed resonant holographic signal is subjected to pixel array addressing reading and phase reconstruction imaging to form a three-dimensional image of the ultrasonic echo wave front distribution of the target object.

[0016] The application further provides an acoustic image sensor for resonant holographic sensing, which is applied to the above-mentioned acoustic three-dimensional imaging method for resonant holographic sensing and comprises:

[0017] The acoustic image sensor is sequentially provided from top to bottom with a Helmholtz type microcavity metasurface, an RS type stacked MUT unit array and an application specific integrated circuit; the diaphragm of the RS type stacked MUT unit is one of an RS type stacked diaphragm with double piezoelectric layers or an RS type stacked diaphragm with a single piezoelectric layer compounded on a capacitive MUT diaphragm;

[0018] The Helmholtz type microcavity metasurface comprises surface through holes arranged in an array and internal microcavities in one-to-one correspondence with the surface through holes; the bottom of each internal microcavity is formed by an RS type stacked diaphragm of the RS type stacked MUT unit or by a plurality of RS type stacked diaphragms of the RS type stacked MUT unit arranged in parallel;

[0019] The RS type stacked MUT unit array comprises a plurality of RS type stacked MUT units arranged in a pixelated array; each RS type stacked MUT unit comprises a suspended RS type stacked diaphragm and a peripheral support substrate; the RS type stacked diaphragm is a multilayer structure sequentially provided from top to bottom with a silicon layer, a silicon dioxide layer, a reference electrode layer, a reference piezoelectric layer, a common electrode layer, a sensing piezoelectric layer and a sensing electrode layer;

[0020] The reference electrode layers of the RS type stacked MUT units are connected to each other to form a single electrode; the polarization directions of the reference piezoelectric layers in the RS type stacked MUT units are the same, the polarization directions of the sensing piezoelectric layers are the same, and the polarization direction of the sensing piezoelectric layer is opposite to that of the reference piezoelectric layer; the common electrode layers of the RS type stacked MUT units are a common seamless metal thin layer connected to ground and used for shielding the charge crosstalk between the reference piezoelectric layer and the sensing piezoelectric layer of each RS type stacked MUT unit;

[0021] The application specific integrated circuit is an integrated circuit composed of a plurality of signal processing unit circuits arranged in an array, each signal processing unit circuit corresponding to the resonant holographic signal output by one RS type stacked MUT unit or the resonant holographic signals output by a plurality of RS type stacked MUT units connected in parallel.

[0022] Optionally, the silicon layers in the RS type laminated diaphragm of the RS type MUT unit are etched and separated from each other in the array composition, arranged in a pixelated array.

[0023] Optionally, the RS type laminated diaphragm of the RS type MUT unit is a laminated diaphragm provided with a plurality of piezoelectric layers.

[0024] Optionally, the surface via of the Helmholtz type microcavity super surface is set as an inverted conical via for preventing the reference sound field in the internal microcavity from radiating outward.

[0025] Optionally, the peak rectification module in each of the signal processing unit circuits is set to perform unidirectional peak voltage clamping rectification on the resonance holographic signal.

[0026] It can be seen that the application irradiates a target object with ultrasonic waves by exciting an ultrasonic sound source to emit ultrasonic waves, and focuses the ultrasonic echo reflected by the target object with an acoustic lens to form an imaging acoustic field containing intensity distribution and phase distribution, and the imaging acoustic field is imaged on the surface of an acoustic image sensor. The acoustic image sensor is placed on the image plane focal plane of the acoustic lens to receive the spatial distribution information of the intensity and phase of the imaging acoustic field. The acoustic image sensor is an array of acousto-electric conversion pixel units provided with a Helmholtz microcavity super surface on the surface. Each structural unit of the Helmholtz microcavity super surface corresponds to an acousto-electric conversion pixel unit, or corresponds to a plurality of parallelly arranged acousto-electric conversion pixel units. The imaging acoustic field enters the corresponding internal microcavity through the surface through hole of each structural unit of the Helmholtz microcavity super surface in the acoustic image sensor. The bottom of the internal microcavity is composed of a laminated diaphragm of an acousto-electric conversion pixel unit. The laminated diaphragm is provided with a reference diaphragm and a sensing diaphragm, and the reference diaphragm and the sensing diaphragm are connected in a stack from top to bottom. A reference signal with the same frequency as the ultrasonic echo is applied to the excitation electrode of the reference diaphragm to cause the reference piezoelectric layer in the reference diaphragm to resonate and deform, thereby driving the reference diaphragm and the sensing diaphragm to vibrate at the same frequency and radiate a reference acoustic field with the same frequency as the ultrasonic echo to the internal microcavity. The reference acoustic field and the imaging acoustic field entering from each surface through hole locally resonate and superimpose in the corresponding internal microcavity, and through interference, the intensity information and phase information of the imaging acoustic field are converted into a resonantly amplified interference acoustic field. The interference acoustic fields in each internal microcavity together form a holographic acoustic field of the ultrasonic echo reflected by the target object. The holographic acoustic field reacts in each internal microcavity to the laminated diaphragm of each acousto-electric conversion pixel unit and superimposes with the same frequency vibration excited by the reference signal to form a holographic resonance, which drives the reference diaphragm and the sensing diaphragm to vibrate together, so that the sensing piezoelectric layer in the sensing diaphragm induces a corresponding resonant holographic signal on the sensing electrode layer. The above-mentioned resonant holographic sensing acoustic three-dimensional imaging method can solve the problems of large field of view, high resolution and fast real-time imaging that the conventional acoustic holographic imaging, beamforming imaging and MUT array imaging and other acoustic three-dimensional imaging methods currently face.

[0027] In addition, the application also provides a resonant holographic sensing acoustic image sensor, which also has the above-mentioned beneficial effects. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the provided drawings.

[0029] Figure 1A schematic diagram illustrating the principle of an acoustic three-dimensional imaging method based on resonant holographic sensing provided in an embodiment of the present invention;

[0030] Figure 2 A flowchart illustrating an acoustic three-dimensional imaging method using resonant holographic sensing, provided as an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram illustrating the generation and processing of acoustic-electric conversion signals in an acoustic three-dimensional imaging method based on resonant holographic sensing, as provided in an embodiment of the present invention.

[0032] Figure 4 This is a schematic diagram of the structure of an acoustic image sensor for resonant holographic sensing provided in an embodiment of the present invention;

[0033] Figure 5 A schematic diagram of the structure of another acoustic image sensor for resonant holographic sensing provided in an embodiment of the present invention;

[0034] Appendix Figure 1 , 3 The markings in -5 are explained below:

[0035] 1: Acoustic image sensor;

[0036] 1.1: Helmholtz-type microcavity metasurface; 1.1-A: Surface through-hole; 1.1-B: Internal microcavity;

[0037] 1.2: RS-type stacked MUT unit, 1.2-A: Silicon layer, 1.2-B: Silicon dioxide layer, 1.2-C: Reference electrode layer, 1.2-D: Reference piezoelectric layer, 1.2-E: Common electrode layer, 1.2-F: Sensing piezoelectric layer, 1.2-G:

[0038] Supporting substrate, 1.2-H: Sensing electrode layer;

[0039] 1.3: Application-Specific Integrated Circuit; 1.3-A: Peak Rectifier Module;

[0040] 2: Ultrasonic sound source;

[0041] 3: Target object;

[0042] 4: Acoustic lens. Detailed Implementation

[0043] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0044] Reference is made to Figure 1 , Figure 1 A principle schematic diagram of an acoustic three-dimensional imaging method of a resonant holographic sensing provided by the embodiments of the present application.

[0045] The application discloses a resonance holographic sensing acoustic three-dimensional imaging method, which comprises the following steps: irradiating a target object with ultrasonic waves by exciting an ultrasonic sound source; focusing and receiving ultrasonic echoes reflected by the target object by using an acoustic lens; forming an imaging acoustic field containing intensity distribution and phase distribution; and imaging on the surface of an acoustic image sensor. The acoustic image sensor is placed on the image plane focal plane of the acoustic lens, and is used for receiving the spatial distribution information of the intensity and phase of the imaging acoustic field. The acoustic image sensor is an array of acousto-electric conversion pixel units provided with a Helmholtz microcavity super surface on the surface. Each structural unit of the Helmholtz microcavity super surface corresponds to one acousto-electric conversion pixel unit, or corresponds to a plurality of parallelly arranged acousto-electric conversion pixel units. The imaging acoustic field enters the corresponding internal microcavity through the surface through hole of each structural unit of the Helmholtz microcavity super surface in the acoustic image sensor. The bottom of the internal microcavity is formed by a laminated diaphragm of an acousto-electric conversion pixel unit. The laminated diaphragm is provided with a reference diaphragm and a sensing diaphragm, and the reference diaphragm and the sensing diaphragm are connected in a laminated manner from top to bottom. A reference signal with the same frequency as the ultrasonic echo is applied to the excitation electrode of the reference diaphragm, so that the reference piezoelectric layer in the reference diaphragm resonates and deforms, and then drives the reference diaphragm and the sensing diaphragm to vibrate at the same frequency, and at the same time, radiates a reference acoustic field with the same frequency as the ultrasonic echo to the internal microcavity. The reference acoustic field and the imaging acoustic field entering from each surface through hole locally resonate and superimpose in the corresponding internal microcavity, and through interference, the intensity information and the phase information of the imaging acoustic field are converted into an interference acoustic field amplified by resonance. The interference acoustic fields in each internal microcavity together form a holographic acoustic field of the ultrasonic echo reflected by the target object. The holographic acoustic field acts on the laminated diaphragm of each acousto-electric conversion pixel unit in each internal microcavity, and is superimposed with the same frequency vibration excited by the reference signal, forms a holographic resonance, drives the reference diaphragm and the sensing diaphragm to vibrate together, so that the sensing piezoelectric layer in the sensing diaphragm induces a corresponding resonance holographic signal on the sensing electrode layer. In addition, the resonance holographic signal transmitted to the signal processing unit is peak-detected and denoised to obtain a preprocessed resonance holographic signal, and the preprocessed resonance holographic signal is subjected to pixel array addressing reading and phase reconstruction imaging to form a three-dimensional image of the ultrasonic echo wave front distribution of the target object. Through the above-mentioned resonance holographic sensing acoustic three-dimensional imaging method, the problems that the conventional acoustic holographic imaging, beam forming imaging and MUT array imaging cannot realize large field of view, high resolution and fast real-time imaging can be solved.

[0046] Further, in order to make the application more convenient to understand, please refer to Figure 2 . Figure 2 A flow chart of a resonance holographic sensing acoustic three-dimensional imaging method provided by the application, which can include:

[0047] S101: irradiate the target object with ultrasonic waves emitted by exciting the ultrasonic sound source, and focus the ultrasonic echo reflected by the target object with the acoustic lens to form an imaging acoustic field containing intensity distribution and phase distribution, and image on the surface of the acoustic image sensor.

[0048] It should be noted that in the embodiment, the acoustic image sensor is placed on the image plane focal plane of the acoustic lens, and is used to receive the spatial distribution information of the intensity and phase of the imaging acoustic field. The acoustic image sensor is an array of acousto-electric conversion pixel units provided with a Helmholtz microcavity super surface on the surface. Each structural unit of the Helmholtz microcavity super surface corresponds to an acousto-electric conversion pixel unit, or corresponds to a plurality of parallelly arranged acousto-electric conversion pixel units. In the embodiment, the holographic signal of the target object can be obtained by signal processing of the imaging acoustic field containing intensity distribution and phase distribution.

[0049] S102: The imaging acoustic field enters the corresponding internal microcavity through the surface through hole of each structural unit of the Helmholtz microcavity super surface in the acoustic image sensor.

[0050] It should be noted that in the embodiment, the bottom of the internal microcavity is composed of a laminated diaphragm of an acousto-electric conversion pixel unit. The laminated diaphragm is provided with a reference diaphragm and a sensing diaphragm, and the reference diaphragm and the sensing diaphragm are connected in layers one above another.

[0051] S103: A reference signal with the same frequency as the ultrasonic echo is applied to the excitation electrode of the reference diaphragm to cause the reference piezoelectric layer inside the reference diaphragm to resonate and deform, thereby driving the reference diaphragm and the sensing diaphragm to vibrate together at the same frequency, and at the same time, radiating a reference acoustic field with the same frequency as the ultrasonic echo into the corresponding internal microcavity.

[0052] It should be noted that in the embodiment, since the reference diaphragm and the sensing diaphragm are connected in layers at the bottom of the internal microcavity, when the reference signal with the same frequency as the ultrasonic echo is applied to the excitation electrode of the reference diaphragm to drive the reference piezoelectric layer inside the reference diaphragm to resonate and deform, the reference diaphragm and the sensing diaphragm will be driven to vibrate together at the same frequency, and at the same time, radiate a reference acoustic field with the same frequency as the ultrasonic echo into the corresponding internal microcavity.

[0053] S104: The reference acoustic field and the imaging acoustic field entering from each surface through hole locally resonate and superimpose in the corresponding internal microcavity, and through interference, the intensity information and phase information of the imaging acoustic field are converted into a resonantly amplified interference acoustic field, and the interference acoustic fields in each internal microcavity together form a holographic acoustic field of the ultrasonic echo reflected by the target object.

[0054] It needs to be explained that in the embodiment, the interference sound field formed in each internal microcavity is collectively composed of the holographic sound field of the ultrasonic echo reflected by the target object, and the acoustic three-dimensional imaging of the target object is completed by using the holographic sound field. The spatial information required for three-dimensional imaging is generated by combining the intensity distribution of the holographic sound field with the phase reconstruction algorithm.

[0055] S105: The holographic sound field reacts on the laminated diaphragm of each acoustoelectric conversion pixel unit in each internal microcavity, and is superimposed with the same frequency vibration excited by the reference signal to form a holographic resonance, drive the reference diaphragm and the sensing diaphragm to vibrate together, so that the sensing piezoelectric layer in the sensing diaphragm induces a corresponding resonance holographic signal on the sensing electrode layer.

[0056] It needs to be explained that the laminated diaphragm in the embodiment is a multi-layer structure, which can be provided with a silicon layer, a silicon dioxide layer, a reference electrode layer, a reference piezoelectric layer, a common electrode layer, a sensing piezoelectric layer and a sensing electrode layer from top to bottom. In the embodiment, when the holographic sound field reacts on the laminated diaphragm of each acoustoelectric conversion pixel unit in each internal microcavity, the reference signal excitation drives the reference diaphragm and the sensing diaphragm to vibrate together at the same frequency, and at the same time, the holographic sound field is superimposed with the same frequency vibration excited by the reference signal to form a holographic resonance, drive the reference diaphragm and the sensing diaphragm to vibrate together.

[0057] Further, in order to realize the acoustic three-dimensional imaging of the resonance holographic sensing, the following steps can be included:

[0058] Peak detection and noise removal processing are performed on the resonance holographic signal transmitted to the signal processing unit to obtain a preprocessed resonance holographic signal.

[0059] The preprocessed resonance holographic signal is subjected to pixel array addressing reading and phase reconstruction imaging to form a three-dimensional image of the ultrasonic echo wavefront distribution of the target object. Specifically, the processing process of the resonance holographic signal by the signal processing unit includes:

[0060] Step S1: The peak detection subunit in the signal processing unit performs peak detection processing on the resonance holographic signal to convert the resonance holographic signal into a steady direct current voltage.

[0061] It needs to be explained that in the embodiment, the peak detection subunit performs peak detection processing on the resonance holographic signal to obtain the peak voltage of the resonance holographic signal, and converts it into a steady direct current voltage.

[0062] Step S2: The noise removal subunit in the signal processing unit performs noise removal processing on the steady direct current voltage to obtain a steady direct current voltage after noise removal processing.

[0063] Step S3: The addressing and reading subcomponent addresses and samples the steady-state direct current voltage after the noise processing of all the acoustoelectric conversion pixel units according to the pixel position, and reads out the voltage value and stores it in pixels.

[0064] Step S4: The voltage value of all the acoustoelectric conversion pixel units stored in pixels is transmitted to the phase reconstruction subcomponent, so that the phase reconstruction subcomponent reconstructs the overall phase of the ultrasonic echo to obtain the spatial information of the ultrasonic echo, and completes the three-dimensional imaging of the ultrasonic echo wavefront distribution.

[0065] In order to facilitate the understanding of the present application, the technical solutions provided by the present application need to be described, that is, when no reference signal is applied to the excitation electrode of the reference diaphragm, the above-mentioned acoustic three-dimensional imaging method of resonant holographic sensing can be converted into acoustic two-dimensional intensity imaging.

[0066] Specifically, the acoustic two-dimensional intensity imaging includes:

[0067] Step S11: An ultrasonic wave is emitted by exciting the ultrasonic sound source to irradiate the target object, and the ultrasonic echo reflected by the target object is focused by the acoustic lens to form an imaging sound field, and the surface through hole of each structural unit of the Helmholtz type microcavity super surface in the acoustic image sensor enters the corresponding internal microcavity, and acts on the laminated diaphragm of each acoustoelectric conversion pixel unit in each internal microcavity to drive the laminated diaphragm to vibrate, so that the sensing piezoelectric layer in the laminated diaphragm induces a corresponding acoustoelectric signal on the sensing electrode layer.

[0068] Step S12: The signal processing unit performs peak detection and noise processing on the acoustoelectric signal to obtain a steady-state direct current voltage after peak detection and noise processing.

[0069] Step S13: The addressing and reading subcomponent addresses and samples the steady-state direct current voltage after the noise processing of all the acoustoelectric conversion pixel units according to the pixel position, and reads out the voltage value and stores it in pixels.

[0070] Step S14: The voltage value of all the acoustoelectric conversion pixel units stored in pixels is combined to form a two-dimensional intensity image of the ultrasonic echo according to the pixel position.

[0071] Next, a resonant holographic sensing acoustic image sensor provided by an embodiment of the present application is introduced, and the resonant holographic sensing acoustic image sensor described below is applied to the above-mentioned resonant holographic sensing acoustic three-dimensional imaging method, and can be correspondingly referred to the above-mentioned resonant holographic sensing acoustic three-dimensional imaging method.

[0072] For details, please refer to Figure 3 . Figure 3A schematic diagram of the generation and processing of the acoustoelectric conversion signal in the acoustic three-dimensional imaging method of the resonant holographic sensor provided by the embodiment of the present application can include:

[0073] The acoustic image sensor 1 is sequentially provided from top to bottom with a Helmholtz type micro-cavity metasurface 1.1, an RS type stacked MUT unit 1.2 array, and an application specific integrated circuit 1.3; the diaphragm of the RS type stacked MUT unit 1.2 is one of an RS type stacked diaphragm with double piezoelectric layers or an RS type stacked diaphragm with a single piezoelectric layer compounded on a capacitive MUT diaphragm;

[0074] The Helmholtz type micro-cavity metasurface 1.1 includes surface through holes 1.1-A arranged in an array, and internal micro-cavities 1.1-B corresponding to the surface through holes 1.1-A in a one-to-one correspondence; the bottom of each internal micro-cavity 1.1-B is formed by an RS type stacked diaphragm of an RS type stacked MUT unit 1.2, or by a plurality of RS type stacked diaphragms of RS type stacked MUT units 1.2 arranged in parallel;

[0075] The RS type stacked MUT unit 1.2 array is a plurality of RS type stacked MUT units 1.2 arranged in a pixelated array; each RS type stacked MUT unit 1.2 includes a suspended RS type stacked diaphragm and a peripheral support substrate 1.2-G; the RS type stacked diaphragm is a multi-layer structure sequentially provided from top to bottom with a silicon layer 1.2-A, a silicon dioxide layer 1.2-B, a reference electrode layer 1.2-C, a reference piezoelectric layer 1.2-D, a common electrode layer 1.2-E, a sensing piezoelectric layer 1.2-F, and a sensing electrode layer 1.2-H;

[0076] The reference electrode layers 1.2-C of the respective RS type stacked MUT units 1.2 are connected together as a single electrode; the polarization directions of the reference piezoelectric layers 1.2-D in the respective RS type stacked MUT units 1.2 are the same, the polarization directions of the sensing piezoelectric layers 1.2-F are the same, and the polarization direction of the sensing piezoelectric layer 1.2-F is opposite to the polarization direction of the reference piezoelectric layer 1.2-D; the common electrode layer 1.2-E of each RS type stacked MUT unit 1.2 is a complete and seamless metal thin layer shared by all the RS type stacked MUT units 1.2 and is connected to ground, and is used to shield the charge crosstalk between the reference piezoelectric layer 1.2-D and the sensing piezoelectric layer 1.2-F of each RS type stacked MUT unit 1.2;

[0077] The application specific integrated circuit 1.3 is an integrated circuit composed of a plurality of signal processing unit circuits arranged in an array, each signal processing unit circuit processing the resonant holographic signal output by one RS type stacked MUT unit 1.2 or the resonant holographic signals output by a plurality of RS type stacked MUT units 1.2 connected in parallel.

[0078] It needs to be explained that the RS type laminated diaphragm in the embodiment corresponds to the laminated diaphragm in the acoustic three-dimensional imaging method. In the embodiment, the reference diaphragm receives a reference signal, and radiates a reference sound field in the internal microcavity 1.1-B of the Helmholtz type microcavity metasurface 1.1 according to the reference signal, wherein the frequency of the reference sound field is the same as that of the ultrasonic echo reflected by the target object 3, so that the reference sound field and the imaging sound field are locally resonated and superimposed in the internal microcavity 1.1-B, and the intensity distribution and the phase distribution of the imaging sound field are converted into a resonantly amplified interference sound field through interference, as a holographic sound field. In the embodiment, the reference electrodes of each pixel unit are interconnected, and the same reference signal voltage is loaded, and the reference sound field radiated is limited to the inside of the Helmholtz type microcavity. In the embodiment, the polarization directions of the reference piezoelectric layer 1.2-D and the sensing piezoelectric layer 1.2-F of the double-piezoelectric laminated structure of the MUT diaphragm are set to be opposite, so that the polarity of the acoustoelectric signal induced on the sensing electrode layer 1.2-H is the same as that of the reference signal voltage loaded on the reference electrode layer 1.2-C when the MUT diaphragm deforms.

[0079] Further, in order to reduce the imaging noise of the resonant holographic sensing acoustic image sensor, the silicon layers 1.2-A in the RS type laminated diaphragm of the RS type MUT unit can be etched and separated from each other in the array composition, and arranged in a pixelized array.

[0080] It needs to be explained that in the embodiment, the silicon layers 1.2-A in the RS type laminated diaphragm of the RS type MUT unit are etched and separated from each other, and arranged in a pixelized array, wherein the pixelized silicon layers 1.2-A are correspondingly arranged with the pixelized RS type laminated MUT unit 1.2.

[0081] Further, in order to improve the imaging performance of the resonant holographic sensing acoustic image sensor 1, the RS type laminated diaphragm of the RS type MUT unit can be a laminated diaphragm provided with a plurality of piezoelectric layers.

[0082] It needs to be explained that in the embodiment, the plurality of piezoelectric layers are correspondingly arranged in a pixelized array.

[0083] Further, in order to ensure that the imaging sound field entering the pixelized internal microcavity 1.1-B through the surface through hole 1.1-A of the Helmholtz type microcavity metasurface 1.1 does not escape from the internal microcavity 1.1-B, the surface through hole 1.1-A of the Helmholtz type microcavity metasurface 1.1 can be arranged as an inverted conical through hole for preventing the reference sound field in the internal microcavity 1.1-B from radiating outward.

[0084] Further, in order to reduce the noise of the resonance holographic signal generated in the image sensor 1 of the resonance holographic sensor, the peak rectification module 1.3-A in each signal processing unit circuit can be configured to perform unidirectional peak voltage clamping rectification on the resonance holographic signal.

[0085] The peak detection subunit 1.3A is configured to perform unidirectional peak voltage clamping rectification on the resonance holographic signal, which can reduce the sensing voltage when the diaphragm restores the initial deformation, reduce the leakage of sensing charge in the peak detection subunit 1.3A, and reduce the imaging noise.

[0086] Further, for the convenience of understanding, in the embodiment, the holographic acoustic image sensor 1 can refer to Figure 4 and Figure 5 . Figure 4 A structure schematic diagram of a resonance holographic sensing acoustic image sensor device provided by the embodiment of the present application, Figure 5 Another structure schematic diagram of a resonance holographic sensing acoustic image sensor device provided by the embodiment of the present application.

[0087] It should be noted that, Figure 4 The cavity bottom of each internal microcavity 1.1-B in the embodiment is composed of the RS type laminated diaphragm of the RS type laminated MUT unit 1.2; Figure 5 The cavity bottom of each internal microcavity 1.1-B in the embodiment is composed of the RS type laminated diaphragm of the RS type laminated MUT unit 1.2;

[0088] The resonant holographic sensing acoustic image sensor 1 provided by the embodiment of the present application is sequentially provided from top to bottom with a Helmholtz type micro-cavity metasurface 1.1, an RS type stacked MUT unit 1.2 array and an application specific integrated circuit 1.3. The diaphragm of the RS type stacked MUT unit 1.2 is one of an RS type stacked diaphragm with double piezoelectric layers or an RS type stacked diaphragm with a single piezoelectric layer compounded on a capacitive MUT diaphragm. The Helmholtz type micro-cavity metasurface 1.1 comprises surface through holes 1.1-A arranged in an array and internal micro-cavities 1.1-B corresponding to the surface through holes 1.1-A in one-to-one correspondence. The cavity bottom of each internal micro-cavity 1.1-B is formed by an RS type stacked diaphragm of an RS type stacked MUT unit 1.2 or by an RS type stacked diaphragm arrangement of a plurality of parallelly connected RS type stacked MUT units 1.2. The RS type stacked MUT unit 1.2 array comprises a plurality of RS type stacked MUT units 1.2 arranged in a pixelated array. Each RS type stacked MUT unit 1.2 comprises a suspended RS type stacked diaphragm and a peripheral support substrate 1.2-G. The RS type stacked diaphragm is a multi-layer structure sequentially provided from top to bottom with a silicon layer 1.2-A, a silicon dioxide layer 1.2-B, a reference electrode layer 1.2-C, a reference piezoelectric layer 1.2-D, a common electrode layer 1.2-E, a sensing piezoelectric layer 1.2-F and a sensing electrode layer 1.2-H. The reference electrode layers 1.2-C of the respective RS type stacked MUT units 1.2 are connected together into a single electrode. The polarization directions of the reference piezoelectric layers 1.2-D in the respective RS type stacked MUT units 1.2 are the same. The polarization direction of the sensing piezoelectric layer 1.2-F is opposite to that of the reference piezoelectric layer 1.2-D. The common electrode layer 1.2-E of the respective RS type stacked MUT units 1.2 is a complete and seamless metal layer shared by the RS type stacked MUT units 1.2 and is connected to ground, for shielding the charge crosstalk between the reference piezoelectric layer 1.2-D and the sensing piezoelectric layer 1.2-F of each RS type stacked MUT unit 1.2. The application specific integrated circuit 1.3 is an integrated circuit comprising a plurality of signal processing unit circuits arranged in an array. Each signal processing unit circuit processes the resonant holographic signals output by one RS type stacked MUT unit 1.2 or a plurality of parallelly connected RS type stacked MUT units 1.2. The image sensor provided by the present application can solve the problems of large field of view, high resolution and fast real-time imaging currently faced by conventional acoustic holographic imaging, beamforming imaging and MUT array imaging.Furthermore, the application reduces the inter-pixel coupling noise of the image sensor of the resonant holographic sensing by etching the silicon layer 1.2-A in the RS type laminated diaphragm of the RS type MUT unit from each other in the array composition to arrange in a pixelated array; improves the performance of the acoustic three-dimensional imaging of the acoustic image sensor 1 using the resonant holographic sensing by setting the RS type laminated diaphragm of the RS type MUT unit as a laminated diaphragm of multiple piezoelectric layers; prevents the reference sound field in the internal microcavity 1.1-B from radiating outward by setting the surface through hole 1.1-A of the Helmholtz type microcavity metasurface 1.1 as an inverted conical through hole, thereby ensuring that the imaging sound field entering the pixelated internal microcavity 1.1-B through the surface through hole 1.1-A of the Helmholtz type microcavity metasurface 1.1 does not escape from the internal microcavity 1.1-B; and reduces the noise of the resonant holographic signal generated in the image sensor of the resonant holographic sensing to complete the acoustic three-dimensional imaging by setting the peak rectification module 1.3-A in each signal processing unit circuit as a peak voltage one-way clamping rectifier for the resonant holographic signal and setting the peak detection subunit 1.3A in the application specific integrated circuit 1.3 as a peak detection subunit for the positive peak detection of the sound pressure.

[0089] In order to make the application more convenient to understand, the preparation method of the resonant holographic sensing acoustic image sensor of the embodiment of the application is introduced as follows:

[0090] Step S21: etching the neck through hole and the cavity of the Helmholtz type microcavity metasurface in the top silicon layer of the SOI wafer.

[0091] It should be noted that each cavity corresponds to at least one RS type laminated MUT unit.

[0092] Step S22: preparing an RS type laminated MUT unit array.

[0093] Each RS type laminated MUT unit includes a suspended RS type laminated diaphragm and a peripheral support substrate, wherein the RS type laminated diaphragm is a multilayer structure, and the silicon layer, the silicon dioxide layer, the reference electrode layer, the reference piezoelectric layer, the common electrode layer, the sensing piezoelectric layer and the sensing electrode layer are sequentially arranged from top to bottom; the reference electrode layer is formed by interconnecting the reference electrodes of each pixel unit; the polarization directions of the reference piezoelectric layer and the sensing piezoelectric layer are opposite; the common electrode layer is grounded to shield the electromagnetic interference between the reference piezoelectric layer and the sensing piezoelectric layer.

[0094] Step S23: performing low-temperature metal bonding treatment on the etched top silicon layer of the SOI wafer and the prepared RS type laminated MUT unit array, and interconnecting the prepared RS type laminated MUT unit array and the application specific integrated circuit through low-temperature metal bonding, and etching the substrate and the oxide layer of the SOI wafer as the image sensor of the resonant holographic sensing.

[0095] The low-temperature bonding process between the etched top silicon layer of the SOI wafer and the prepared RS type stacked MUT cell array, and between the prepared RS type stacked MUT cell array and the application specific integrated circuit in this embodiment is not specifically required. For example, wafer-level low-temperature metal bonding can be used, or other low-temperature bonding methods can be used.

[0096] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the various embodiments can be referred to each other. For the device disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the relevant part can be referred to the method part.

[0097] Finally, it should be noted that in this document, relationships such as first and second, and the like, are used to distinguish one entity or action from another, without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, so that a process, method, article, or apparatus that includes a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0098] The above describes in detail the acoustic three-dimensional imaging method and image sensor of the resonant holographic sensing provided by the present application. The principle and implementation manner of the present application are described by using specific examples. The above embodiment is only used to help understand the method of the present application and its core idea. Meanwhile, for the general technical personnel in the field, according to the idea of the present application, the specific implementation manner and application range will be changed. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A resonant holographic sensing acoustic three-dimensional imaging method, characterized in that, include: An ultrasonic source is excited to emit ultrasonic waves that irradiate a target object, and an acoustic lens focuses and receives the ultrasonic echo reflected from the target object, forming an imaging sound field containing intensity and phase distributions, which is then imaged onto the surface of an acoustic image sensor. The acoustic image sensor is placed on the image-side focal plane of the acoustic lens to receive the spatial distribution information of the intensity and phase of the imaging sound field. The acoustic image sensor is an array of acoustic-to-electric conversion pixel units with a Helmholtz-type microcavity metasurface on its surface. Each structural unit of the Helmholtz-type microcavity metasurface corresponds to one acoustic-to-electric conversion pixel unit, or to multiple acoustic-to-electric conversion pixel units arranged in parallel. The acoustic image sensor is arranged from top to bottom as a Helmholtz-type microcavity metasurface, an RS-type stacked MUT unit array, and a dedicated integrated circuit. The diaphragm of the RS-type stacked MUT unit is either an RS-type stacked diaphragm with a double piezoelectric layer, or an RS-type stacked diaphragm with a single piezoelectric layer on a capacitive MUT diaphragm. The imaging sound field enters the corresponding internal microcavity through the surface through-holes of each structural unit of the Helmholtz-type microcavity metasurface in the acoustic image sensor; the bottom of the internal microcavity is composed of the stacked diaphragm of the acoustic-electric conversion pixel unit; the stacked diaphragm is provided with a reference diaphragm and a sensing diaphragm; the reference diaphragm and the sensing diaphragm are stacked and connected sequentially. By applying a reference signal with the same frequency as the ultrasonic echo to the excitation electrode of the reference diaphragm, the reference piezoelectric layer inside the reference diaphragm is caused to resonate and deform, thereby driving the reference diaphragm and the sensing diaphragm to vibrate together at the same frequency, and simultaneously radiating a reference sound field with the same frequency as the ultrasonic echo into the internal microcavity. The reference sound field and the imaging sound field entering from each of the surface through-holes are locally resonated and superimposed in the corresponding internal microcavities, and the intensity and phase information of the imaging sound field are converted into a resonant amplified interference sound field through interference. The interference sound fields in each of the internal microcavities together form the holographic sound field of the ultrasonic echo reflected by the target object. The holographic sound field reacts in each of the internal microcavities to the stacked diaphragms of each acoustic-electric conversion pixel unit, and is superimposed with the same-frequency vibration excited by the reference signal to form a holographic resonance, driving the reference diaphragm and the sensing diaphragm to vibrate together, so that the sensing piezoelectric layer in the sensing diaphragm induces the corresponding resonant holographic signal on the sensing electrode layer.

2. The acoustic three-dimensional imaging method of resonant holographic sensing according to claim 1, characterized in that, include: The resonant holographic signal transmitted to the signal processing unit is subjected to peak detection and denoising to obtain a preprocessed resonant holographic signal; The preprocessed resonant holographic signal is subjected to pixel array addressing readout and phase reconstruction imaging to form a three-dimensional image of the ultrasonic echo wavefront distribution of the target object.

3. An acoustic image sensor for resonant holographic sensing, applied to the acoustic three-dimensional imaging method for resonant holographic sensing as described in claim 1, characterized in that, include: The acoustic image sensor is configured from top to bottom with a Helmholtz-type microcavity metasurface, an RS-type stacked MUT unit array, and a dedicated integrated circuit. The diaphragm of the RS-type stacked MUT unit is either an RS-type stacked diaphragm with a double piezoelectric layer or an RS-type stacked diaphragm with a single piezoelectric layer on a capacitive MUT diaphragm. The Helmholtz-type microcavity metasurface includes an array of surface vias and corresponding internal microcavities; the bottom of each internal microcavity is formed by an RS-type stacked diaphragm of one RS-type stacked MUT unit, or by an arrangement of multiple RS-type stacked diaphragms of RS-type stacked MUT units in parallel. The RS-type stacked MUT unit array consists of multiple RS-type stacked MUT units arranged in a pixelated array; each RS-type stacked MUT unit includes a suspended RS-type stacked diaphragm and a surrounding supporting substrate; The RS-type stacked diaphragm is a multi-layer structure, consisting of a silicon layer, a silicon dioxide layer, a reference electrode layer, a reference piezoelectric layer, a common electrode layer, a sensing piezoelectric layer, and a sensing electrode layer, arranged sequentially from top to bottom. The reference electrode layers of each RS-type stacked MUT unit are interconnected to form a single electrode; The reference piezoelectric layer in each RS-type stacked MUT unit has the same polarization direction, the sensing piezoelectric layer has the same polarization direction, and the polarization direction of the sensing piezoelectric layer is opposite to that of the reference piezoelectric layer; the common electrode layer of each RS-type stacked MUT unit is a shared, complete, seamless metal thin layer and grounded, used to shield the charge crosstalk between the reference piezoelectric layer and the sensing piezoelectric layer of each RS-type stacked MUT unit; The application-specific integrated circuit is an integrated circuit composed of multiple signal processing unit circuits arranged in an array. Each signal processing unit circuit processes the resonant holographic signal output by an RS-type stacked MUT unit, or the resonant holographic signal output by multiple parallel RS-type stacked MUT units.

4. The acoustic image sensor for resonant holographic sensing according to claim 3, characterized in that, The silicon layers in the RS-type stacked diaphragm of the RS-type MUT unit are etched and separated from each other in the array composition, and arranged in a pixelated array.

5. The acoustic image sensor for resonant holographic sensing according to claim 3, characterized in that, The RS-type MUT unit has an RS-type stacked diaphragm with multiple piezoelectric layers.

6. The acoustic image sensor for resonant holographic sensing according to claim 3, characterized in that, The surface vias of the Helmholtz-type microcavity metasurface are configured as inverted conical vias to prevent the reference sound field in the internal microcavity from radiating outward.

7. The acoustic image sensor for resonant holographic sensing according to claim 3, characterized in that, The peak rectification module in each of the signal processing unit circuits is configured to perform peak voltage unidirectional clamping rectification on the resonant holographic signal.

Images