Weak signal detection device and three-dimensional acoustic flat-bottom superlens thereof

Abstract

The application discloses a weak signal detection device and a three-dimensional acoustic flat-bottom superlens thereof. O The three-dimensional acoustic flat-bottom superlens is configured as a symmetrical structure, and in a coordinate system with u v w as a coordinate origin, v w the three-dimensional acoustic flat-bottom superlens is symmetrical about u v and includes a multilayer lattice, the multilayer lattice is arranged along a v direction, each layer of the lattice includes a plurality of micro-lattices which are connected to each other and arranged along a u direction and a w direction, the micro-lattices of adjacent two layers of the lattice are connected, and two end surfaces of each layer of the lattice in the v direction are configured as planes, and each micro-lattice includes: a cuboid shell, the shell has an inner cavity, a plurality of through holes which are in communication with the inner cavity are arranged on six surfaces of the shell, and the plurality of through holes are uniformly and symmetrically arranged; and a plurality of trusses, the trusses are arranged in the inner cavity, and the trusses pass through the center of the shell and extend to the shell along body diagonal lines of the shell. According to the three-dimensional acoustic flat-bottom superlens, the three-dimensional acoustic flat-bottom superlens can be integrated with a plane sensor and wide-angle response can be realized, and the degree of freedom of refractive index regulation is expanded.

Description

Technical Field

[0001] This invention relates to the field of weak signal detection technology, and more specifically, to a three-dimensional acoustic flat-bottom metalens for a weak signal detection device and a weak signal detection device having the three-dimensional acoustic flat-bottom metalens. Background Technology

[0002] Acoustic weak signal detection technology has important application value in fields such as industrial inspection and environmental monitoring, but traditional methods face the dual challenges of sound wave attenuation and environmental interference. Among related technologies, sound field manipulation technology based on acoustic metamaterials can enhance the signal, but it is limited by narrowband resonance mechanism and strong directivity, making it difficult to meet the requirements of broadband response and wide-angle detection in practical applications. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a three-dimensional acoustic flat-bottom meta-lens for weak signal detection devices. The three-dimensional acoustic flat-bottom meta-lens for weak signal detection devices overcomes the inherent limitations of traditional curved lenses in integrating with planar sensors and achieving wide-angle response, and expands the degree of freedom in refractive index adjustment.

[0004] The present invention also proposes a weak signal detection device having the aforementioned three-dimensional acoustic flat-bottom meta-lens for weak signal detection.

[0005] According to a first aspect embodiment of the present invention, a three-dimensional acoustic flat-bottom metalens for a weak signal detection device, wherein the three-dimensional acoustic flat-bottom metalens is configured with a symmetrical structure, in order to O The origin of the coordinate system uvw In the coordinate system, respectively about vw flat, UV Planar symmetry and comprising multiple layers of lattice, the multiple layers of said lattice along v The lattice is oriented in a specific direction, and each layer of the lattice comprises lattices that are interconnected and aligned along the direction of each other. u direction and w Multiple microlattices are arranged in an oriented manner, with adjacent layers of the microlattices connected, and each layer of the microlattice is in... v The two end faces in the direction are constructed as planes. Each microlattice includes: a cubic shell having an inner cavity, with six faces of the shell respectively having through holes communicating with the inner cavity, and a plurality of through holes being uniformly and symmetrically arranged; and a plurality of trusses disposed in the inner cavity, the trusses passing through the center of the shell and extending along the body diagonal of the shell to the vertices on opposite sides of the shell, wherein the positions of the plurality of microlattices are determined by the following method: The following formula achieves the desired lens sphere center. The origin xyz coordinate system to uvw Coordinate system transformation: (1) (2) In the formula, u ( x , y )express xyz Midpoint of coordinate system ( x , y The transformed horizontal coordinates; v( x , y )express xyz The vertical coordinates of the point (x, y) after transformation in the coordinate system; R is the radius of the ideal lens; To change the angle; For gradient operators; point A , B , C , D , E , F All located in xy In the plane and point ABCD Forming a rectangle ABCD ,rectangle ABCD Symmetric about the y-axis and with an area larger than the three-dimensional acoustic flat-bottomed meta-lens xy The projected area of ​​a plane, a point E ,point F For the ideal lens in xy The projected profile and side length of a plane BC The intersection between them Calculate the refractive index of the lens using the following formula. n ( r ): (3) In the formula, n 0 represents the refractive index of the surrounding medium. r For point ( x , y The radial distance from the center of the lens is used to calculate the two-dimensional refractive index of the three-dimensional acoustic flat-bottom metalens. : (4) Calculate the Jacobian matrix J using the following formula: (5) The three-dimensional refractive index of the three-dimensional acoustic flat-bottomed meta-lens is calculated using the following formula. n 3d : (6) Based on the structural parameter-equivalent refractive index mapping relationship n DB ( da , dh The three-dimensional acoustic flat-bottom metalens is constructed using a nearest neighbor matching strategy. da This represents the width of the through hole projected onto the horizontal plane. dh This indicates the width of the truss.

[0006] The three-dimensional acoustic flat-bottom metalens for weak signal detection devices according to embodiments of the present invention achieves planar transformation of the three-dimensional lens through quasi-conformal conversion technology, overcoming the inherent limitation of traditional curved lenses being difficult to integrate with planar sensors and achieve wide-angle response. Simultaneously, the microlattice structure combining truss and shell expands the degree of freedom in refractive index adjustment.

[0007] In addition, the three-dimensional acoustic flat-bottom meta-lens for a weak signal detection device according to embodiments of the present invention also has the following additional technical features: According to some embodiments of the present invention, the three-dimensional acoustic flat-bottom meta-lens is constructed according to the following formula: (7) In the formula, The structural parameters of the three-dimensional acoustic flat-bottom metalens are indicated.

[0008] According to some embodiments of the present invention, the through hole is square. da Let be the side length of the through hole.

[0009] According to some embodiments of the present invention, the number of trusses is equal to the number of body diagonals of the housing.

[0010] According to some embodiments of the present invention, each layer of the lattice is in u The width along the axial direction is from the middle outwards w The diameter decreases at both ends of the shaft.

[0011] According to some embodiments of the present invention, in the arrangement direction of the multilayer lattice, the lattice at the middle position is... uw The projected area on the plane is greater than that of the lattice at both ends. uw The projected area on a plane.

[0012] According to some embodiments of the present invention, the inner cavity is cubic. DC This indicates the side length of the inner cavity. DC When =2.8mm, da The value range is 0.5mm-3.5mm. dh The value range is 0.5mm-1.0mm.

[0013] According to some embodiments of the present invention, the three-dimensional refractive index of the three-dimensional acoustic flat-bottom metalens is... n 3d Version 1.0-3.0.

[0014] According to some embodiments of the present invention, the two microlattices are connected by the side of one of the housings being attached to the side of the other housing.

[0015] A weak signal detection device according to a second aspect of the present invention includes a three-dimensional acoustic flat-bottom metalens for a weak signal detection device as described in a first aspect of the present invention.

[0016] The weak signal detection device according to the present invention utilizes the three-dimensional acoustic flat-bottom meta-lens for weak signal detection devices as described above, overcoming the inherent limitation that traditional curved lenses are difficult to integrate with planar sensors and achieve wide-angle response, while expanding the degree of freedom of refractive index adjustment.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] Figure 1 This is a perspective view of a three-dimensional acoustic flat-bottom meta-lens according to an embodiment of the present invention; Figure 2 It is a three-dimensional diagram of a traditional curved lens; Figure 3 This is a three-dimensional view of the microlattice of a three-dimensional acoustic flat-bottom metalens according to an embodiment of the present invention; Figure 4 This is a cross-sectional view of the microlattice of a three-dimensional acoustic flat-bottom metalens according to an embodiment of the present invention; Figure 5 This is an energy band distribution diagram of the microlattice of a three-dimensional acoustic flat-bottom metalens according to an embodiment of the present invention; Figure 6 It is a microlattice according to an embodiment of the present invention. da Graph showing the influence of refractive index-frequency dispersion characteristics; Figure 7 The refractive index of the microlattice in different propagation directions according to embodiments of the present invention varies with da Parameter change trend graph; Figure 8 This is a microlattice joint control according to an embodiment of the present invention. da and dh The range of refractive index coverage at that time; Figure 9 It is a three-dimensional acoustic flat-bottom meta-lens according to an embodiment of the present invention. xyz coordinate system to uvw A diagram illustrating coordinate system transformation, where... Figure 9 (a) is xyz coordinate system Figure 9 (b) is uvw Coordinate system; Figure 10 This is a simulation diagram of a three-dimensional acoustic flat-bottom meta-lens according to an embodiment of the present invention, wherein... Figure 10 (a) is a schematic diagram of the simulation model of a three-dimensional acoustic flat-bottom meta-lens. Figure 10 (b) is a sound pressure amplitude cloud map of a three-dimensional acoustic flat-bottom meta-lens; Figure 11 The spatial distribution characteristics of sound pressure level on the centrally symmetrical cross-section of a three-dimensional acoustic flat-bottom metalens according to an embodiment of the present invention; Figure 12 This is an architecture diagram of an acoustic testing system according to an embodiment of the present invention; Figure 13 This is a diagram showing the acoustic gain curves of a three-dimensional acoustic flat-bottom metalens according to an embodiment of the present invention at different incident angles. Figure 14 This is a comparison diagram of the sound pressure level distribution between a three-dimensional acoustic flat-bottom metalens according to an embodiment of the present invention and a conventional three-dimensional lens, wherein... Figure 14 (a) is a sound pressure level distribution diagram at the focal position of a three-dimensional acoustic flat-bottom meta-lens according to an embodiment of the present invention at various frequencies and angles. Figure 14 (b) shows the maximum sound pressure level at the rear end plane of a traditional three-dimensional lens. Figure 15 This is a voltage curve diagram of a three-dimensional acoustic flat-bottom meta-lens according to an embodiment of the present invention at different incident angles; Figure 16 The graph shows the time-domain waveform and frequency-domain spectrum analysis results of the directly received signal and the signal processed by the three-dimensional acoustic flat-bottom meta-lens of this invention.

[0019] Figure label: Three-dimensional acoustic flat-bottomed meta-lens 10, microlattice 100, housing 110, inner cavity 111, through hole 112, truss 120. Acoustic testing system 20, acoustic measurement host 21, power amplifier 22, planar sound source 23, measuring microphone 24, acoustic signal analyzer 25, scale rotary table 26, single-axis scale moving stage 27. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] This application is based on the inventor's discovery and understanding of the following facts and problems: Acoustic weak signal detection technology refers to the extraction of target acoustic wave signals with energy significantly lower than the noise floor from background noise using highly sensitive acoustic sensing systems and advanced signal processing methods. This technological field has long faced the dual challenges of sound wave propagation attenuation and environmental interference, especially in the perception and identification of weak acoustic events (such as early mechanical fault noises, ultrasonic leaks in pipelines, and long-distance sound source localization). Reliable signal extraction has become a key bottleneck restricting detection accuracy. Current mainstream technologies focus on improving microphone sensitivity and circuit signal-to-noise ratio. While some progress has been made, performance improvements have encountered significant marginal limitations.

[0022] Against this backdrop, acoustic metamaterial-based sound field manipulation technology, by reconstructing the sound wave transmission path to achieve local energy enhancement of the target signal, provides a new paradigm for solving the signal-to-noise ratio bottleneck. This technology breaks through the traditional mindset of "sensor-end improvement" and shifts to the innovative dimension of "sound field-end manipulation," opening a substantial path for a leap in the detection efficiency of weak signals. Although acoustic metamaterials exhibit significant advantages in local sound pressure enhancement, existing technologies still have many limitations. In resonant enhancement mechanisms, narrowband characteristics become the main bottleneck. Narrowband resonant mechanisms cannot cover the broadband spectral characteristics of weak target signals, leading to the loss of key information in multiple frequency domains and making it difficult to support high-precision signal identification. Focusing enhancement structures also face severe challenges. Acoustic Luneburg lenses can achieve focusing of planar sound waves on the opposite side of the incident plane, but due to the mismatch between the focal plane of their curved configuration and the planar sensor, wide-angle sound focusing is difficult to achieve.

[0023] These technical limitations pose significant challenges to existing sound field manipulation methods in the detection of weak signals under complex conditions, especially in practical applications requiring both broadband response and wide-angle detection. Furthermore, while three-dimensional acoustic metamaterials offer advantages over two-dimensional structures in achieving three-dimensional spatial sound field enhancement, extending from two-dimensional microlattice designs to three-dimensional structures still necessitates consideration of additive manufacturing process characteristics (such as maximum overhang size and minimum gap requirements), presenting new technical challenges for the design and implementation of three-dimensional microlattice structures.

[0024] Therefore, this application proposes a three-dimensional acoustic flat-bottom metalens 10 for weak signal detection devices, which can meet the key technical requirements of broadband response and wide-angle detection in weak acoustic signal detection. The three-dimensional acoustic flat-bottom metalens 10 for weak signal detection devices according to an embodiment of the first aspect of the present invention is described below with reference to the accompanying drawings.

[0025] like Figure 1 , Figures 3-16 As shown, the three-dimensional acoustic flat-bottomed meta-lens 10 for a weak signal detection device according to an embodiment of the present invention is constructed with a symmetrical structure, in order to... O The origin of the coordinate system uvw In the coordinate system, respectively about vw flat, UV Planar symmetry.

[0026] Specifically, the three-dimensional acoustic flat-bottom metalens 10 includes a multi-layer lattice, with the multi-layer lattice along... v The directional arrangement, each lattice layer includes interconnected layers along the direction. u direction and w Multiple microlattices 100 are arranged in an oriented manner, with adjacent layers of microlattices 100 connected. Each layer of microlattice is in... v The two end faces in the direction are constructed as planes. In the arrangement direction of the multilayer lattice, the lattice at the middle position is... uw The projected area on the plane is larger than the lattice area at both ends. uw The projected area on the plane, each lattice layer in u The width along the axial direction is from the middle outwards w The axes decrease at both ends. That is, multiple microlattices 100 of each lattice are arranged on a plane parallel to the axis. uw Planar, multiple microlattices 100 along w The axes are arranged in multiple rows, along u The axes are arranged in multiple columns, with adjacent microlattices 100 connected, and the three-dimensional acoustic flat-bottom meta-lens 10 is parallel to... uw The cross-sectional area of ​​the plane along v The axis decreases from the middle towards both ends. For example... Figure 1 As shown, each lattice layer is nearly circular, and the three-dimensional acoustic flat-bottomed meta-lens 10 is a near-spherical shape with a flat-bottomed feature.

[0027] like Figure 3 and Figure 4As shown, each microlattice 100 includes a cubic shell 110 and a plurality of trusses 120. The shell 110 has an inner cavity 111, and each of its six faces has a through-hole 112 communicating with the inner cavity 111. The plurality of through-holes 112 are arranged uniformly and symmetrically. Two microlattices 100 are connected by the side of one shell 110 fitting against the side of the other shell 110. The number of trusses 120 is equal to the number of body diagonals of the shell 110. The trusses 120 are disposed within the inner cavity 111, passing through the center of the shell 110 and extending along the body diagonals of the shell 110 to the vertices on opposite sides of the shell 110. da This indicates the width of the projection of the through hole 112 onto the horizontal plane. dh This indicates the width of truss 120. This composite structure extends the equivalent sound path in the microlattice 100, significantly expanding the degrees of freedom for refractive index modulation. In the figure, the six through-holes 112 are paired and face each other; each through-hole 112 is square. da Let 112 be the side length of the through hole 112, and let 111 be a cube. DC This indicates the side length of the inner cavity 111. Adjustment is possible. da and DC Two geometric parameters allow for variations in the equivalent refractive index within the range of 1.0 to 3.0.

[0028] Figure 5 It is a microlattice 100 with a lattice constant of 4 mm. da =2mm DC =2.8mm dh The band structure at 0.5 mm is used to calculate the equivalent phase velocity. This can be achieved by adjusting... da , dh The volume ratio of the solid-gas two phases can be adjusted to actively control the equivalent sound velocity, thereby establishing a quantitative relationship between structural parameters and acoustic performance. This is achieved when the lattice constant is 4 mm. DC =2.8mm dh Under the condition of 0.5mm, Figure 6 Revealed da Based on the influence of refractive index-frequency dispersion characteristics, 6kHz-10kHz was selected as the target operating frequency. Figure 7 The refractive index at this frequency varies with different propagation directions. da The changing trend of the parameters verifies that the microlattice 100 structure possesses weak anisotropy. Further... dh Incorporate into the control parameter system, Figure 8 The system demonstrates the joint da and dh The range of refractive indices that can be covered by the parameters.

[0029] The positions of the multiple microlattices 100 are determined by the following method: Implemented according to the following formula Figure 9 (a) The center of the ideal lens sphere The origin xyz coordinate system to Figure 9 (b) uvw The transformation of the coordinate system is achieved by constructing a coordinate system from a rectangle. ABCD arrive A'B'C'D' The nonlinear coordinate mapping allows the three-dimensional acoustic flat-bottomed metalens 10 with flat-bottom features to be embedded into a regular rectangular background field. This transformation is achieved by solving two sets of Laplace equations with Dillickerley and Newman boundary conditions: (1) (2) In the formula, u ( x , y )express xyz Midpoint of coordinate system ( x , y The transformed horizontal coordinates; v( x , y )express xyz The vertical coordinates of the point (x, y) after transformation in the coordinate system; R is the radius of the ideal lens; To change the angle; For gradient operators; point A , B , C , D , E , F All located in xy In the plane and point ABCD Forming a rectangle ABCD ,rectangle ABCD Regarding the y-axis symmetric and area larger than the three-dimensional acoustic flat-bottomed meta-lens 10, xy The projected area of ​​a plane, a point E ,point F For an ideal lens xy The projected profile and side length of a plane BC The intersection between them Calculate the refractive index of the lens using the following formula. n ( r ): (3) In the formula, n 0 represents the refractive index of the surrounding medium. r For point ( x , y The radial distance from the center of the lens; the two-dimensional refractive index of the three-dimensional acoustic flat-bottom meta-lens 10 is calculated according to the following formula. : (4) Calculate the Jacobian matrix J using the following formula: (5) Based on obtaining the two-dimensional refractive index distribution, along... v The three-dimensional refractive index distribution can be obtained by rotating the axis once. The three-dimensional refractive index of the three-dimensional acoustic flat-bottom metalens 10 is calculated according to the following formula. n 3d : (6) Based on the structural parameter-equivalent refractive index mapping relationship n DB ( da , dh A three-dimensional acoustic flat-bottomed metalens 10 is constructed using a nearest neighbor matching strategy. The three-dimensional acoustic flat-bottomed metalens 10 is constructed according to the following formula: (7) In the formula, The structural parameters of the three-dimensional acoustic flat-bottom meta-lens 10 are indicated.

[0030] The acoustic focusing characteristics of the three-dimensional acoustic flat-bottom meta-lens 10 are verified through numerical simulation and semi-anechoic chamber experiments. The sound pressure gain law under the condition of incident angle of 0°-45° in the 6kHz-10kHz frequency band is quantitatively analyzed. Comparison samples of the three-dimensional acoustic flat-bottom meta-lens 10 and the traditional three-dimensional lens are prepared to verify the enhancement effect of quasi-conformal angle transformation on wide-angle acoustic focusing.

[0031] like Figure 10 As shown in (a), the acoustic simulation analysis of the three-dimensional acoustic flat-bottomed meta-lens 10 model was performed using the frequency domain method in the pressure acoustics module of COMSOL Multiphysics 6.2 software. The simulation computation domain was set to a cuboid air region of 0.4m × 0.2m × 0.1m. Considering the significant impedance difference between the solid and air media, the solid domain was simplified to an ideal rigid boundary condition in the simulation, and only the air domain was analyzed for acoustic field. The air medium parameters were set as follows: density ρ =1.2kg / m 3 speed of sound c=343 m / s. The mesh was generated using free tetrahedral elements, discretizing the entire computational domain, including the microstructure air cavity inside the lens. To ensure computational accuracy, the maximum element size was controlled to be within 1 / 7 of the wavelength corresponding to the highest analysis frequency of 16 kHz. Due to the large number of meshes caused by the microlattice 100 structure of the three-dimensional acoustic flat-bottom metalens 10, a 1 / 2 symmetric model was used to reduce computational load. Symmetric boundary conditions were applied to the symmetric profile, based on the symmetry of the lens structure itself and the symmetric distribution of the incident sound field. Plane wave radiation boundary conditions were set at the outer boundaries of the computational domain to simulate open boundaries and absorb outward sound waves.

[0032] After setting up the simulation domain, the background radiated sound field was defined, and the sound pressure amplitude of the incident plane wave was fixed at 1 Pa, i.e., the sound pressure level was 91 dB. The incident angles were set to 0°, 15°, 30°, and 45°, respectively, and the incident sound wave frequency covered a wide range from 1 kHz to 20 kHz. The software parametric scanning function was used to perform fine frequency sweep analysis with a step size of 1 kHz. Figure 10 (b) shows the sound pressure amplitude contour map of the three-dimensional acoustic flat-bottomed meta-lens 10 when a plane wave is perpendicularly incident (0°) at a frequency of 8 kHz. After being modulated by the three-dimensional acoustic flat-bottomed meta-lens 10, the plane wave forms a significant energy focusing effect near the designed focal area behind the lens, approximately forming a significant sound pressure converging beam behind the lens. Quantitative analysis, measured at the center of the flat surface of the three-dimensional acoustic flat-bottomed meta-lens 10, shows that the sound pressure level at the focal point reaches 103.49 dB, which is a significant improvement of 11.49 dB compared to the incident background sound field sound pressure level at the same point without the three-dimensional acoustic flat-bottomed meta-lens 10. This data confirms the efficient focusing capability of the three-dimensional acoustic flat-bottomed meta-lens 10 for sound wave energy. Figure 11 The study systematically demonstrates the spatial distribution characteristics of sound pressure level on the centrally symmetrical profile of the three-dimensional acoustic flat-bottom meta-lens 10 design at three operating frequencies of 6kHz, 8kHz and 10kHz, and at four typical incident angles of 0°, 15°, 30° and 45°, clearly revealing the dynamic variation law of sound energy concentration with frequency and incident angle.

[0033] The experimental prototype of the three-dimensional acoustic flat-bottom meta-lens 10 was fabricated using stereolithography (SLA) 3D printing technology. The material used was photosensitive resin No. 8224, which possesses good mechanical strength and molding properties, and exhibits a light green color after curing. Tests showed that the acoustic properties of the cured resin in air approached rigid boundary conditions, consistent with the acoustic assumptions for the solid portion in the simulation. During fabrication, the precision was controlled within 0.2 mm, ensuring the critical dimensional accuracy of the microlattice 100 structure and meeting design requirements. The final experimental prototype had external dimensions of 68 mm in length, 72 mm in width, and 72 mm in height, with a maximum width of 40 mm in the flat-bottom area. To accurately evaluate the enhancement effect of quasi-conformal conversion on wide-angle acoustic focusing, a conventional three-dimensional lens without quasi-conformal conversion was fabricated as a control simultaneously with the fabrication of the three-dimensional acoustic flat-bottom metalens 10. The same SLA technology and photosensitive resin material (8224) were used, maintaining a processing precision of 0.2 mm. Only the lattice units were replaced with a basic simple cubic structure, and the size of the control sample was adjusted to 72 mm × 72 mm × 72 mm to match the spherical characteristics of the conventional three-dimensional lens. This control group provides a reliable benchmark for subsequent sound pressure gain experiments.

[0034] In the performance testing of the experimental prototype, a semi-anechoic chamber was constructed as follows: Figure 12 The acoustic testing system 20 shown includes three core functions: signal generation, signal acquisition, and positioning control. The acoustic measurement host 21 generates a signal at a specified frequency, which is amplified by the power amplifier 22 and then drives the planar sound source 23. The planar sound source 23 consists of a 9-channel speaker array, capable of generating a uniform plane wave sound field within the test area. The measurement microphone 24 uses a diaphragm condenser microphone equipped with a 40dB gain preamplifier, with a frequency response range of 20Hz-20kHz. This unit is directly connected to the acoustic measurement host 21 via a BNC interface, enabling 24-bit / 192kHz high-precision data acquisition. The acoustic signal analyzer 25 connects to the acoustic measurement host 21 and the measurement microphone 24, and is used to analyze the spectral characteristics of the sound signal.

[0035] The test platform integrates a rotary stage 26 and a single-axis movable stage 27. The rotary stage 26 is used to adjust the incident azimuth angle of the three-dimensional acoustic flat-bottomed metalens 10, and the single-axis movable stage 27 is used to control the position of the measuring microphone 24. The three-dimensional acoustic flat-bottomed metalens 10 is set to the target incident angle (0° / 15° / 30° / 45°) using the rotary stage 26, while the single-axis movable stage 27 is simultaneously manipulated to position the microphone in the designed focal region. The focal position is determined based on COMSOL sound pressure field simulation. A planar sound source 23 emits a broadband swept-frequency signal, covering a frequency range of 100Hz to 15kHz, with a frequency interval of 100Hz and a sweep duration of 10 seconds. Under both experimental conditions of the presence and removal of the three-dimensional acoustic flat-bottomed metalens 10, the signals received by the measuring microphone 24 are measured and recorded, and the sound pressure level data at each discrete frequency point is analyzed using Fast Fourier Transform. Based on the sound pressure level dataset, the sound gain curve is calculated and plotted. This curve quantitatively characterizes the increase in sound pressure level after the lens is introduced, i.e., the energy enhancement effect of the target acoustic signal under lens control. Sub-graphs corresponding to different incident angles are shown below. Figure 13 As shown, the experimental results are compared and verified with the gain curves generated by COMSOL multiphysics simulation. The three-dimensional acoustic flat-bottom metalens 10 exhibits an effective gain range in the 6kHz-10kHz range.

[0036] During the test, the three-dimensional acoustic flat-bottom meta-lens 10 is fixed at the target incident angle by the scale rotation stage 26, and the measuring microphone 24 is precisely positioned in the designed focal area by the single-axis scale movement stage 27, and the sound pressure level data is recorded. Figure 14 (a) Demonstrates the sound pressure level distribution at the focal point of the three-dimensional acoustic flat-bottom meta-lens 10 at various frequencies and angles. Figure 14 (b) represents the maximum sound pressure level at the rear end plane of a conventional three-dimensional lens. The results show that the acoustic enhancement angle range of the three-dimensional acoustic flat-bottom meta-lens 10 is significantly better than that of the untransformed conventional three-dimensional lens, which even exhibits sound pressure attenuation at 30° and 45° incidence.

[0037] The following section combines piezoelectric ceramic voltage enhancement experiments (incident angle of 0°-45°) with signal-to-noise ratio improvement performance tests for outdoor weak signal detection to verify engineering applications.

[0038] The PZT-5H piezoelectric ceramic sheet is tightly bonded to the center area of ​​the flat bottom of the three-dimensional acoustic flat-bottom meta-lens 10, continuing the use of... Figure 12 The acoustic testing system 20 shown was used in a standard anechoic chamber environment to record the signal difference with and without a lens at an operating frequency of 8 kHz using a voltage measuring device. Experimental data show that the output voltage after modulation by the three-dimensional acoustic flat-bottom meta-lens 10 is significantly improved, with a peak voltage increase of over 12 dB, fully verifying the enhancing effect of sound field modulation on electroacoustic conversion efficiency. Figure 15The voltage curves at different angles are shown. Under 0° normal incidence, the voltage gain remains stable at 4.92 times the peak value; when the incidence angle increases to 45°, it still maintains an effective gain of 2.62 times. This metalens-piezoelectric integrated system, besides its application in acoustic signal detection, also has significant potential in the field of acoustic energy harvesting. It can effectively capture broadband acoustic energy generated by mechanical vibrations, achieve efficient energy conversion of environmental noise, and provide a novel energy supply solution for low-power sensor nodes in the Internet of Things.

[0039] A large-diaphragm dynamic-coil microphone was closely fitted to the center area of ​​the flat bottom of the three-dimensional acoustic flat-bottom meta-lens 10, and a signal acquisition system was formed by combining a 40dB gain low-noise signal amplifier and a 24-bit high-precision data acquisition card. The experimental site was an open urban space (background noise level 58dB(A)), and the 8kHz pure tone signal was tested and verified under typical environmental noise conditions including human conversation and traffic noise. During the test, a dual-channel synchronous acquisition mode was used to simultaneously record the directly received signal and the signal processed by the three-dimensional acoustic flat-bottom meta-lens 10. Figure 16 The time-domain waveform and frequency-domain spectrum analysis results of the acquired signal are presented. Under the same sound field conditions, a net signal-to-noise ratio gain of 6.98 dB is achieved when using the three-dimensional acoustic flat-bottom metalens 10. This frequency-selective enhancement characteristic stems from the bandpass filtering effect of the three-dimensional acoustic flat-bottom metalens 10: it has a poor enhancement effect on low-frequency sound waves, but a good enhancement effect on high-frequency target signals.

[0040] The three-dimensional acoustic flat-bottom meta-lens 10 for weak signal detection equipment according to an embodiment of the present invention achieves planar transformation of the three-dimensional lens through quasi-conformal conversion technology, overcoming the inherent limitation of traditional curved lenses being difficult to integrate with planar sensors and achieve wide-angle response. Simultaneously, the microlattice 100 structure composed of the truss 120 and the housing 110 expands the degree of freedom for refractive index adjustment. DC When =2.8mm, da The value range is 0.5mm-3.5mm. dh The value ranges from 0.5mm to 1.0mm. The three-dimensional refractive index of the three-dimensional acoustic flat-bottomed meta-lens 10 is... n 3d The gain ranges from 1.0 to 3.0. It exhibits excellent sound wave focusing performance in a wide frequency range of 6kHz to 10kHz, and can achieve a maximum sound pressure gain of 11.5dB at an operating frequency of 8kHz. Even under a large incident angle of 45°, it can still maintain an effective gain of 8.3dB, and significantly improve the signal-to-noise ratio of weak signals by 6.98dB in urban noise backgrounds.

[0041] This application provides a new technical approach for detecting weak acoustic signals in complex environments; the proposed planar design method can be extended to the fabrication of metamaterials in other wavebands; and its frequency-selective enhancement characteristics open up new avenues for intelligent noise suppression. This achievement not only promotes the transformation of acoustic metamaterials from basic research to engineering applications, but also provides valuable reference for interdisciplinary wavefield manipulation research.

[0042] A weak signal detection device according to a second aspect of the present invention includes a three-dimensional acoustic flat-bottom meta-lens 10 for a weak signal detection device according to a first aspect of the present invention.

[0043] According to the weak signal detection device of the present invention, the three-dimensional acoustic flat-bottom meta-lens 10 for weak signal detection device described above overcomes the inherent limitation that traditional curved lenses are difficult to integrate with planar sensors and achieve wide-angle response, while expanding the degree of freedom of refractive index adjustment.

[0044] Other configurations and operations of the weak signal detection device according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here.

[0045] In the description of this invention, it should be understood that the terms "center", "length", "width", "height", "upper", "lower", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0047] In the description of this invention, "first feature" and "second feature" may include one or more of the features. "Above" or "below" the second feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. "Above," "above," and "over" the second feature include the first feature being directly above or diagonally above the second feature, or simply indicating that the first feature is at a higher horizontal level than the second feature.

[0048] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can also refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0049] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "specific embodiment," "example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A three-dimensional acoustic flat-bottom metalens for weak signal detection equipment, characterized in that, The three-dimensional acoustic flat-bottom meta-lens is constructed in a symmetrical structure, in order to... O The origin of the coordinate system uvw In the coordinate system, respectively about vw flat, UV Planar symmetry and comprising multiple layers of lattice, the multiple layers of said lattice along v The lattice is oriented in a specific direction, and each layer of the lattice comprises lattices that are interconnected and aligned along the direction of each other. u direction and w Multiple microlattices are arranged in an oriented manner, with adjacent layers of the microlattices connected, and each layer of the microlattice is in... v The two end faces in the direction are constructed as planes, and each of the microlattices includes: A cubic shell has an inner cavity, and six sides of the shell are respectively provided with through holes communicating with the inner cavity, and a plurality of through holes are evenly and symmetrically arranged; Multiple trusses are disposed within the inner cavity, the trusses passing through the center of the housing and extending along the body diagonal of the housing to the vertices on opposite sides of the housing, wherein the positions of the multiple microlattices are determined by the following method: The following formula achieves the desired lens sphere center. The origin xyz coordinate system to uvw Coordinate system transformation: (1) (2) In the formula, u ( x , y )express xyz Midpoint of coordinate system ( x , y The transformed horizontal coordinates; v( x , y )express xyz The vertical coordinates of the point (x, y) after transformation in the coordinate system; R is the radius of the ideal lens; To change the angle; For gradient operators; point A , B , C , D , E , F All located in xy In the plane and point ABCD Forming a rectangle ABCD ,rectangle ABCD Symmetric about the y-axis and with an area larger than the three-dimensional acoustic flat-bottomed meta-lens xy The projected area of ​​a plane, a point E ,point F For the ideal lens in xy The projected profile and side length of a plane BC The intersection between them Calculate the refractive index of the lens using the following formula. n ( r ): (3) In the formula, n 0 represents the refractive index of the surrounding medium. r For point ( x , y The radial distance from the center of the lens is used to calculate the two-dimensional refractive index of the three-dimensional acoustic flat-bottom metalens. : (4) Calculate the Jacobian matrix J using the following formula: (5) The three-dimensional refractive index of the three-dimensional acoustic flat-bottomed meta-lens is calculated using the following formula. n 3d : (6) Based on the structural parameter-equivalent refractive index mapping relationship n DB ( da , dh The three-dimensional acoustic flat-bottom metalens is constructed using a nearest neighbor matching strategy. da This represents the width of the through hole projected onto the horizontal plane. dh This indicates the width of the truss.

2. The three-dimensional acoustic flat-bottom metalens for weak signal detection equipment according to claim 1, characterized in that, The three-dimensional acoustic flat-bottom meta-lens is constructed according to the following formula: (7) In the formula, The structural parameters of the three-dimensional acoustic flat-bottom metalens are indicated.

3. The three-dimensional acoustic flat-bottom metalens for weak signal detection equipment according to claim 1, characterized in that, The through hole is square. da Let be the side length of the through hole.

4. The three-dimensional acoustic flat-bottom metalens for weak signal detection equipment according to claim 1, characterized in that, The number of trusses is equal to the number of body diagonals of the shell.

5. The three-dimensional acoustic flat-bottom metalens for weak signal detection equipment according to claim 1, characterized in that, Each layer of the lattice is in u The width along the axial direction is from the middle outwards w The diameter decreases at both ends of the shaft.

6. The three-dimensional acoustic flat-bottom metalens for weak signal detection equipment according to claim 1, characterized in that, In the arrangement direction of the multilayered lattice, the lattice at the middle position is in uw The projected area on the plane is greater than that of the lattice at both ends. uw The projected area on a plane.

7. The three-dimensional acoustic flat-bottom metalens for weak signal detection equipment according to claim 1, characterized in that, The inner cavity is cubic. DC This indicates the side length of the inner cavity. DC When =2.8mm, da The value range is 0.5mm-3.5mm. dh The value range is 0.5mm-1.0mm.

8. The three-dimensional acoustic flat-bottom metalens for weak signal detection equipment according to claim 1, characterized in that, The three-dimensional refractive index of the three-dimensional acoustic flat-bottomed meta-lens n 3d Version 1.0-3.

0.

9. The three-dimensional acoustic flat-bottom metalens for a weak signal detection device according to any one of claims 1-8, characterized in that, The two microlattices are connected by the side of one of the housings being attached to the side of the other housing.

10. A weak signal detection device, characterized in that, Includes the three-dimensional acoustic flat-bottom metalens for weak signal detection devices according to any one of claims 1-9.

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