Superlens-based near-surface defect super-resolution imaging system and imaging method
By designing a periodic cylindrical superlens structure and combining it with the Fabry–pérot resonance theory, subwavelength resolution of the ultrasound imaging system was achieved, solving the problem of diffraction limit limitation in traditional ultrasound imaging technology. It is suitable for non-destructive testing and biomedical diagnosis, and has high resolution and flexible application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN INST OF ADVANCED TECH CHINESE ACAD OF SCI
- Filing Date
- 2023-09-28
- Publication Date
- 2026-05-15
AI Technical Summary
Existing ultrasound imaging technology is limited by the diffraction limit, making it difficult to achieve high-resolution near-surface defect detection, especially in non-destructive testing and biomedical diagnostics. Traditional methods cannot achieve subwavelength ultra-high resolution imaging without sacrificing penetration depth.
A super-resolution imaging system for near-surface defects based on a superlens was designed. A periodically arranged columnar structure was used as the main body of the superlens. The Fabry-Pérot resonance theory was used to realize the efficient transmission of ultrasonic waves from the object plane to the image plane, breaking the dependence on fluid medium and making it suitable for direct contact detection.
It achieves subwavelength ultrasound imaging in the MHz band, which can accurately identify internal defects. It has high resolution and high signal-to-noise ratio, is suitable for non-destructive testing and biological diagnostics, and is easy to process and reuse.
Smart Images
Figure CN119715800B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ultrasonic testing technology, and more specifically, to a super-resolution imaging system and method for near-surface defects based on a superlens. Background Technology
[0002] Ultrasonic imaging technology has been widely applied in biomedical diagnostics and non-destructive testing (NDT). In NDT applications, the reliability of detecting minute defects (such as subsurface cracks and inclusions) is crucial for the structural safety of critical components in high-value applications. Therefore, high-resolution ultrasonic imaging technology capable of early defect detection is highly needed. However, the resolution of traditional ultrasonic testing is inherently limited by the diffraction limit, primarily determined by wavelength. Generally, increasing the detection frequency can achieve high-resolution ultrasonic imaging. However, with increasing frequency, the ultrasonic signal attenuates rapidly, leading to a decrease in signal-to-noise ratio and detection range. Subwavelength ultrasonic imaging (super-resolution imaging) can achieve high detection resolution without sacrificing penetration depth. Therefore, breaking the diffraction limit and achieving ultra-high-resolution imaging of near-surface defects has widespread demand and significant importance.
[0003] In existing technologies, defect detection imaging schemes mainly include signal post-processing technology and acoustic metamaterials technology. Signal post-processing technology achieves high-resolution imaging by post-processing the acquired signal. Acoustic metamaterials technology utilizes acoustic metamaterials to achieve high-resolution imaging, such as hyperbolic superlenses, super-oscillating lenses, and resonant metamaterials.
[0004] Analysis reveals that signal post-processing techniques are limited to processing raw data, and their ability to improve resolution is constrained by the acquired raw signal, making it impossible to achieve deep subwavelength resolution (ultra-high resolution). Furthermore, existing acoustic metamaterials, particularly hyperbolic superlenses, struggle to achieve acoustic imaging at deep subwavelength scales. The design of super-oscillating lenses relies on optimizing mask structures to generate fine wave interference, but the energy focusing and super-resolution generated by super-oscillation phenomena remain confined to a very small region. One type of resonant superlens, composed of periodic porous structures, is primarily used below the acoustic frequency band and must operate in water or air to achieve imaging of slits in thin plates, which differs from non-destructive testing scenarios. Additionally, Rajagopal et al. proposed a series of porous metamaterials based on Fabry-pérot resonances (plastic straws and porous media acting as non-periodic metamaterial lenses) to achieve subwavelength imaging of subsurface defects in aluminum samples through liquid immersion testing. All of these lenses require operation in a liquid as the medium for sound wave propagation. Under these conditions, evanescent wave field enhancement occurs inside the superlens rather than at the receiver, leading to poor resolution contrast and low signal-to-noise ratio. Furthermore, in most cases of non-destructive testing and biomedical diagnostics, the object being tested is not allowed to be immersed in liquid.
[0005] In summary, existing technologies need to be improved to break the diffraction limit and achieve ultra-high resolution imaging of near-surface defects in contact ultrasonic testing. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a near-surface defect super-resolution imaging system and method based on a superlens.
[0007] According to a first aspect of the present invention, a near-surface defect super-resolution imaging system based on a superlens is provided. The system includes: a scanning unit, a signal generation unit, a defect analysis unit, and a superlens structure. The signal generation unit is used to apply ultrasonic waves to a test object. The superlens structure is used to transmit the ultrasonic waves from an object plane to an image plane. The scanning unit is used to acquire scanned images transmitted via the superlens structure. The defect analysis unit is used to analyze the scanned images to determine defect information of the test object.
[0008] The superlens structure includes a substrate and a superlens body fixed on the substrate. The superlens body includes a plurality of periodically arranged columnar bodies, and each columnar body serves as a waveguide for elastic waves, and is periodically arranged on the substrate with a lattice constant.
[0009] According to a second aspect of the present invention, a method for super-resolution imaging of near-surface defects based on a superlens is provided. The method includes the following steps:
[0010] Apply ultrasonic waves to the object being tested;
[0011] A superlens structure is used to transmit ultrasonic waves from the object plane to the image plane;
[0012] Acquire scanned images transmitted via the superlens structure;
[0013] The scanned image is analyzed to determine the defect information of the object under test;
[0014] The superlens structure includes a substrate and a superlens body fixed on the substrate. The superlens body includes a plurality of periodically arranged columnar bodies, and each columnar body serves as a waveguide for elastic waves, and is periodically arranged on the substrate with a lattice constant.
[0015] Compared with existing technologies, the advantages of this invention are that it designs a superlens with a periodic columnar structure arranged on a base, which can be used flexibly according to application requirements, and has the advantages of being reusable and easy to manufacture. Furthermore, it breaks the dependence of the superlens on fluid media (such as water and air), making it suitable for direct contact testing. It can meet the ultrasonic imaging testing requirements in the MHz band, and has broader application prospects in non-destructive testing and biological diagnostics. In summary, this invention can break the diffraction limit and achieve ultra-high resolution imaging of near-surface defects in contact ultrasonic testing.
[0016] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description
[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.
[0018] Figure 1 This is a schematic diagram of a near-surface defect super-resolution imaging system based on a superlens according to an embodiment of the present invention;
[0019] Figure 2 This is a schematic diagram of a superlens structure according to an embodiment of the present invention;
[0020] Figure 3 This is a schematic diagram of sound field propagation using a lens according to an embodiment of the present invention;
[0021] Figure 4 This is a schematic diagram of wavefield simulation results under Fabry-pérot resonance according to an embodiment of the present invention;
[0022] Figure 5 This is a schematic diagram of a superlens fabrication according to an embodiment of the present invention;
[0023] Figure 6 The test block having a transverse through hole is according to an embodiment of the present invention;
[0024] Figure 7 This is a schematic diagram of a super-resolution imaging detection system according to an embodiment of the present invention;
[0025] Figure 8 This is a schematic diagram of the numerical simulation results of a 0.4mm transverse through hole according to an embodiment of the present invention;
[0026] Figure 9 This is a schematic diagram of the experimental results of using a sine wave to detect a 0.4mm transverse through-hole according to an embodiment of the present invention;
[0027] Figure 10This is a schematic diagram of the experimental results of detecting a 0.4mm transverse through-hole using pulse waves according to an embodiment of the present invention, and a numerical simulation result of the 0.4mm transverse through-hole. Detailed Implementation
[0028] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the invention.
[0029] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.
[0030] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.
[0031] In all the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.
[0032] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.
[0033] See Figure 1 As shown, in general, this invention provides a near-surface defect super-resolution imaging system based on a superlens, comprising: a signal generation unit 110, a superlens structure 120, a scanning unit 130, and a defect analysis unit 140. The signal generation unit 110 is used to apply ultrasonic waves to the object being inspected. The superlens structure 120 is used to transmit the ultrasonic waves from the object plane to the image plane. The scanning unit 130 is used to acquire the scanned images transmitted via the superlens structure 120. The defect analysis unit 140 is used to analyze the scanned images to determine the defect information of the object being inspected. This invention proposes a practically valuable superlens and a super-resolution imaging system based on it, exceeding the traditional diffraction limit and laying the foundation for applications in biomedical diagnostics and non-destructive testing evaluation.
[0034] Non-destructive testing (NDT) places high demands on high-resolution ultrasonic imaging, but this is limited by the detection wavelength. Metamaterials possess unprecedented acoustic properties, making them a promising technology for achieving subwavelength resolution ultrasonic imaging beyond the diffraction limit. Given that existing research primarily focuses on fluid-medium-dependent superlenses, suitable for acoustic frequencies below 10 kHz, this invention proposes for the first time a substrate-supported periodic columnar superlens for achieving subwavelength ultrasonic imaging of solid structures in the MHz domain. For example, the superlens structure comprises a substrate and a superlens body fixed to the substrate. The superlens body comprises multiple periodically arranged columnar bodies, each acting as a waveguide for elastic waves, periodically arranged on the substrate with respect to its lattice constant.
[0035] The following sections will describe in detail embodiments of the superlens structure, resonant modes, superlens fabrication, and superlens-based near-surface defect super-resolution imaging system.
[0036] 1. Regarding the design of the superlens structure
[0037] See Figure 2 A superlens structure was designed, consisting of columnar superlenses fixed to a thin-plate substrate. The columnar structure, with dimensions on the order of micrometers, acts as a waveguide for elastic waves and is periodically arranged on the thin plate with a lattice constant A. The thin plate serves as the substrate for fixing the columnar structures, while also allowing the superlens to be tightly coupled to the detection surface as a single unit, and enabling flexible movement. Therefore, the designed superlens exhibits reusability and practicality. Figure 1 In the array, the period is A, the column side length is a, the substrate thickness is T, and the superlens thickness is L. The substrate thickness T is much smaller than the wavelength to reduce the attenuation of the evanescent wave and also to ensure that the impact on the resonant mode is minimized.
[0038] It should be understood that the square columnar structure in the superlens structure can also replace other forms of periodically arranged columnar structures, such as circular columns or one-dimensional strip structures. The columnar structure can be made of ceramic, plexiglass, or metal materials.
[0039] 2. Resonance Modal Analysis
[0040] When detected by transmission, the ultrasonic waves scattered by the defect pass through the superlens. The maximum displacement at the receiving end of the lens is extracted to obtain... Figure 3 The line scan image shown. The ultrasonic field inside the superlens can be represented as:
[0041] U(x)=C1sink mx x+C2cosk mx x, 0 < x < L (1)
[0042] Where C2 and C1 are constants, x represents the coordinate position in the direction of sound propagation, and k mx This is the wave vector in the superlens. Under the Fabry-pérot resonance condition, the transmission coefficient becomes 1, thus the superlens transmits all waves (including evanescent waves) from the object plane to the image plane without any loss, thereby achieving subwavelength imaging. The resonant mode is mainly determined by the height of the columnar structure (e.g., taking an integer multiple of 1 / 4 of the wavelength), which is considered the most important parameter in the design of the Fabry-pérot superlens. Consider... Figure 3 The wave propagation path shown has one end of the lens tightly coupled to the surface to be detected by a coupling agent, while the other end is a freely moving surface. Therefore, the boundary conditions differ from those of a superlens in fluid acoustics. Under the boundary condition of one end being fixed and the other free, when the translational momentum k... mx Satisfying condition k mx When L = (2n-1)π / 2, Fabry-Pérot resonance occurs, where n is an integer. Correspondingly, the resonant frequency is:
[0043]
[0044] in ρ is the longitudinal wave velocity in a slender rod-column structure, E is the Young's modulus of the metallic material, and ρ is the density.
[0045] To verify the applicability of the above theory to the proposed superlens, finite element analysis was performed, and the wave field of the superlens under Fabry–pérot resonance was shown through finite element analysis. Figure 4 This indicates when k mx When L = π / 2, 3π / 2, and 5π / 2, the steady-state sound field in the resonant mode corresponds to the first, second, and third order Fabry–pérot resonances, respectively. (See [reference needed]). Figure 4 (a) Figure 4 (b) and Figure 4 (c). The sound field with and without a base was compared at the first-order resonant frequency; see [reference]. Figure 4 (d) and Figure 4 (f) It can be seen that the thin substrate has almost no effect on the Fabry–pérot resonant mode. At these resonant frequencies, standing waves are formed, and the output surface of the superlens has maximum displacement, which makes the measurement highly robust and has high resolution contrast.
[0046] 3. Fabrication of the superlens structure and the test block under test
[0047] Figure 5 This is a schematic diagram of the fabrication of a superlens. Figure 6 This is a schematic diagram of a test block with a transverse through hole being processed.
[0048] For example, the main material of the superlens is readily available and high-precision manufactured single-crystal silicon. Furthermore, the surface of single-crystal silicon is mirror-like, exhibiting excellent optical backscattering properties, which facilitates subsequent laser vibration measurements. The single-crystal silicon was cut using a precision dicing machine (ADT 7122, Advanced Dicing Technologies, Israel) with a diamond cutting disc of 0.08 mm thickness, achieving a manufacturing tolerance of 0.01 mm. Two side-drilled holes (SDHs) with a diameter of 0.4 mm, a spacing of 0.4 mm (approximately λ / 30), and a distance of 0.1 mm from the top surface were fabricated in a 100 mm × 100 mm × 10 mm 304 stainless steel block via wire electrical discharge machining as near-surface defects to be inspected.
[0049] 4. Super-resolution imaging system based on superlens structure.
[0050] Figure 7 This is a specific embodiment of a super-resolution imaging system based on transmission ultrasonic testing. It includes a superlens structure, a laser vibrometer, a PC, an arbitrary function generator, and a power amplifier. Figure 7 In this study, longitudinal waves were used for transmission-based detection of subsurface defects in a stainless steel block. A superlens was coupled to the detection surface to extract time-domain signals containing defect information, ultimately achieving subwavelength imaging. During the detection process, an optical platform and custom-designed fixtures were used to ensure good coupling and levelness. A piezoelectric transducer (OLYMPUS V101-RB) with a center frequency of 0.50 MHz and a wafer size of 25.4 mm was used to excite longitudinal plane waves via an arbitrary function generator (Tektronix AFG 31152), and the voltage was amplified 200 times by a power amplifier (Ciprian HVA-400-A). A laser vibrometer (Polytec PSV-500HV) was used to probe the displacement field on the lens surface, performing a grating scan with a spatial resolution of 0.2 mm, and averaging the signal 200 times in the time domain to improve the signal-to-noise ratio. The maximum normalized amplitude change from each time-domain signal was plotted relative to the measurement position on the sample to obtain A-scan and C-scan images.
[0051] To further verify the effectiveness of this invention, numerical simulations and experimental verification were conducted. Specifically, two 304 stainless steel samples with a 0.4 mm (λ / 30) spacing between SDHs were designed and manufactured. A sine wave with a center frequency of 0.50 MHz (first-order resonant frequency) was used for detection. A-scan and C-scan imaging of the test blocks were performed using both sine wave and pulse signals. The detection results for the 0.4 mm spacing between SDHs are as follows: Figure 8-10 As shown, where Figure 8 These are the numerical simulation results for a 0.4mm transverse through-hole. Figure 8 (a) is a wave field distribution diagram. Figure 8 (b) is the result of scan A. Figure 9 The results are from an experiment using a sine wave to test a 0.4mm transverse through-hole. Figure 9 (a) is the result of the A scan. Figure 9 (b) is the result of the C scan. Figure 10 These are experimental results from testing a 0.4mm transverse through-hole using pulse waves. Figure 10 (a) is the result of the A scan. Figure 10 (b) shows the C-scan results. The experimental results show that when using a superlens to image internal defects, the signal amplitude drops sharply at the defect location, the defect can be effectively identified, and there is a high detection contrast.
[0052] In summary, this invention designs a silicon-based superlens with a base based on Fabry-pérot resonance theory, with columnar structures arranged periodically on a thin-plate substrate. The frequencies of Fabry-pérot resonances were theoretically analyzed, and the wave field of the superlens in the resonant mode was numerically verified. Experimental results show that using the designed 0.50MHz columnar superlens, high-resolution ultrasonic imaging (λ / 30) with high contrast was achieved, accurately identifying two subsurface defects in a stainless steel structure.
[0053] In summary, compared with the prior art, the present invention has the following main advantages:
[0054] 1) This invention designs a superlens with a periodic columnar structure arrangement on a base, which can be used flexibly according to the needs of use. It has the advantages of being reusable and easy to process, and the significantly reduced feature size makes manufacturing simple.
[0055] 2) This invention adopts a novel superlens structure, which breaks the dependence of superlenses on fluid media (such as water and air), and can be applied to direct contact detection, with broader application prospects in non-destructive testing and biological diagnostics.
[0056] 3) The lens structure designed in this invention is applicable to ultrasonic testing in the MHz band and has practical applications in non-destructive testing and biological diagnostics.
[0057] 4) This invention is the first to analyze the Fabry-pérot resonance mode under elastic wave conditions. The Fabry-pérot resonance frequency was calculated theoretically, and the acoustic field distribution within the superlens under the Fabry-pérot resonance mode was verified by numerical simulation. Experimental results demonstrate the subwavelength ultrasonic imaging capability of the superlens, with a resolution of up to λ / 30.
[0058] This invention can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of the invention.
[0059] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example, but not limited to, electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination thereof. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.
[0060] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.
[0061] The computer program instructions used to perform the operations of this invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages such as Smalltalk, C++, Python, etc., and conventional procedural programming languages such as "C" or similar languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing state information from the computer-readable program instructions. This electronic circuitry can execute the computer-readable program instructions to implement various aspects of the invention.
[0062] Various aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.
[0063] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processor of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner; thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.
[0064] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.
[0065] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions. It will be known to those skilled in the art that implementation in hardware, implementation in software, and implementation using a combination of software and hardware are equivalent.
[0066] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein. The scope of the invention is defined by the appended claims.
Claims
1. A near-surface defect super-resolution imaging system based on a superlens, comprising: The system comprises a scanning unit, a signal generation unit, a defect analysis unit, and a superlens structure. The signal generation unit is used to apply ultrasonic waves to the object under test. The superlens structure is used to transmit ultrasonic waves from the object plane to the image plane. The scanning unit is used to acquire scanned images transmitted via the superlens structure. The defect analysis unit is used to analyze the scanned images to determine the defect information of the object under test. The superlens structure includes a substrate and a superlens body fixed on the substrate. The superlens body includes a plurality of columnar bodies arranged in a periodic manner, and each columnar body serves as a waveguide for elastic waves. The columnar bodies are arranged in a periodic manner on the substrate with a lattice constant. The superlens structure is based on Fabry–pérot resonance and is applicable to contact ultrasonic testing. The columnar body is either a square columnar body or a circular columnar body, and the columnar body is made of ceramic, plexiglass or metal material; The columnar bodies are arranged on the substrate in a one-dimensional or two-dimensional form; In this structure, one end of the superlens is coupled to the surface of the object to be detected by a coupling agent, while the other end is a freely moving surface.
2. The system according to claim 1, characterized in that, The thickness of the substrate is less than the wavelength.
3. The system according to claim 1, characterized in that, The ultrasonic field inside the superlens structure is represented as follows: ， in, C 2 and C 1 is a constant. It is the coordinate position of the direction of sound propagation. It is the wave vector in a superlens, under the boundary condition that one end is fixed and the other end is free, when the translational momentum... Meet the conditions At this time, Fabry–pérot resonance occurs, and the resonant frequency is expressed as: in, It is the longitudinal wave velocity in the columnar structure. E It is the Young's modulus of metallic materials. It represents the density, where n is an integer.
4. The system according to claim 1, characterized in that, The ultrasound waves are either continuous wave signals or pulse signals.
5. An imaging method based on the system according to any one of claims 1 to 4, comprising the following steps: Apply ultrasonic waves to the object being tested; A superlens structure is used to transmit ultrasonic waves from the object plane to the image plane; Acquire scanned images transmitted via the superlens structure; The scanned image is analyzed to determine the defect information of the object under test; The superlens structure includes a substrate and a superlens body fixed on the substrate. The superlens body includes a plurality of periodically arranged columnar bodies, and each columnar body serves as a waveguide for elastic waves, and is periodically arranged on the substrate with a lattice constant.
6. A computer-readable storage medium having a computer program stored thereon, wherein, When the computer program is executed by the processor, it implements the steps of the method according to claim 5.