A miniature photoacoustic endoscopic probe and photoacoustic endoscopic imaging system
Patent Information
- Application Number
- CN202611537492.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-30
- Publication Date
- 2026-11-03
AI Technical Summary
The matching layer of existing transparent ultrasound transducers only has the function of light transmission and cannot actively control the wavefront of the emitted light, resulting in unstable imaging under the undulation of biological tissue surface. In addition, the addition of optical components increases the probe length and structural complexity.
A meta-optical structure is integrated into the output end face of the matching layer of a transparent ultrasonic transducer. The beam focusing enhancement and depth of focus are achieved through spatial phase modulation. The meta-optical structure is then fabricated using micro-nano 3D printing technology to form a focused beam with a specific light field distribution.
It achieves improved imaging consistency and resolution of photoacoustic imaging without increasing probe length and components, making it suitable for endoscopic imaging scenarios in narrow cavities.
Smart Images
Figure CN123023847A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of biomedical imaging and micro-optical device technology, specifically relating to a micro photoacoustic endoscope probe and a photoacoustic endoscope imaging system. Background Technology
[0002] Photoacoustic endoscopy combines the advantages of optical excitation and ultrasound detection, making it valuable for minimally invasive diagnosis and treatment. In this technology, the coaxial transmission of the excitation light and ultrasound signal is crucial for achieving high-quality imaging. While existing transparent ultrasound transducers achieve coaxial integration of optical and acoustic channels, their matching layer only provides acoustic impedance matching and light transmission, lacking the ability to actively control the wavefront of the emitted light. Furthermore, the illumination light is not shaped and optimized before reaching the tissue; its depth of focus and spot morphology are limited by the inherent parameters of the fiber optic output, making it difficult to maintain stable excitation efficiency under the uneven conditions of biological tissue surfaces.
[0003] To address these issues, previous research has attempted to add independent optical lenses or beam shaping devices to the outside of the transducer to achieve spot focusing or depth of focus extension. However, adding external optical components not only increases the probe length and structural complexity, introducing additional challenges in optical path alignment and packaging, but also disrupts the original acoustic matching and geometric configuration of the transducer front end, making it difficult to meet the dual requirements of compact structure and acousto-optic performance for miniaturized photoacoustic endoscopes.
[0004] Therefore, there is an urgent need for a coaxial integrated solution that integrates optical control functions at the transducer matching layer level, without adding extra components and volume, and can achieve beam shaping and depth of focus extension under limited aperture conditions. Summary of the Invention
[0005] The purpose of this invention is to provide a miniature photoacoustic endoscope probe that overcomes the limitations of traditional transparent transducer matching layers, which only have light transmission function and cannot actively control the outgoing light wavefront. Without adding additional optical components, it achieves enhanced focusing and extended depth of focus of the illumination beam, significantly improving the imaging consistency and resolution of photoacoustic endoscope imaging under complex biological tissue surface undulation conditions.
[0006] Another objective of this invention is to combine the aforementioned meta-transparent ultrasonic transducer with a photoacoustic endoscopic imaging system to provide a compact, naturally coaxial, and easily integrated miniature photoacoustic endoscopic probe design. By integrating a meta-optical structure with spatial phase modulation function into the front end face of the matching layer of the transparent ultrasonic transducer, high-quality photoacoustic coaxial excitation and detection can be achieved without introducing additional optical path alignment or mechanical focusing.
[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: The first aspect is a miniature photoacoustic endoscope probe, comprising a super-transparent ultrasonic transducer, an optical module, and a protective housing: The meta-transparent ultrasonic transducer includes a transparent piezoelectric material, a transparent electrode layer, and a transparent matching layer. The exit end face of the matching layer integrates a meta-optical structure. The meta-optical structure is composed of subwavelength-scale meta-units arranged according to a phase distribution scheme. By spatially modulating the wavefront of the emitted light, a focused beam with a specific optical field distribution is formed at the front end of the probe. The optical module is used to guide the light beam to the meta-transparent ultrasonic transducer. The light beam, after being adjusted by the meta-optical structure, is used to emit into biological tissue to excite the photoacoustic effect. The aforementioned meta-transparent ultrasonic transducer is used to convert the acoustic signal generated by the photoacoustic effect into an electrical signal that can be used for imaging. The protective housing is used to house the meta-transparent ultrasonic transducer and optical module.
[0008] Furthermore, the phase distribution of the meta-optical structure is based on the axial pyramid phase superposition and off-axis compensation term, and its expression is: ; in, Radial distance, It is the azimuth angle. For wave number, Here are the base angle parameters of the axial pyramid. For the second phase compensation coefficient, This is the off-axis phase compensation coefficient.
[0009] Furthermore, the phase distribution is obtained through the following optimization: the target phase distribution is discretized into a phase matrix, and a global search algorithm based on Bayesian optimization is used to optimize the parameter combinations ( , , The optimization is carried out with the mean square error between the on-axis light intensity distribution and the ideal flat-top function as the objective function. In each iteration, the Rayleigh-Sommerfeld diffraction integral formula is used to calculate the on-axis light field distribution to evaluate the performance of candidate solutions. After multiple iterations, the optimal phase matrix is obtained.
[0010] Furthermore, the metaunit adopts a regular square frustum shape, and the unit period p is fixed as a specific proportion of the design wavelength λ, satisfying... , where 0 < < 1; The design variable for each hyperstructure unit is height. With the side length of the upper surface The side length of the lower surface is fixed. .
[0011] Furthermore, the structural parameters of the metaunit are determined as follows: a simulation model of the regular square frustum metaunit is established, and different ( , The phase response and transmittance are calculated by combining the parameters to generate a phase-structure parameter database. The required phase values at each position in the target phase matrix are matched with the database, and the value with the smallest phase error is selected under the condition of satisfying the transmittance threshold. , The combination serves as the unit structure at that location.
[0012] Furthermore, the meta-optical structure is fabricated on the exit face of the transparent matching layer using micro / nano 3D printing technology.
[0013] Furthermore, by determining the distance between the optical fiber and the right-angle mirror, as well as the height of the meta-transparent ultrasonic transducer, it is possible to precisely maintain the complex amplitude of the beam while expanding the beam diameter, keeping it in a Gaussian-like beam state to meet the requirements of the meta-optical structure for incident light.
[0014] Furthermore, the optical module includes a single-mode fiber and a right-angle mirror; the right-angle mirror is disposed between the emitting end of the single-mode fiber and the meta-transparent ultrasonic transducer, and is used to reflect the light beam to the matching layer.
[0015] Furthermore, the protective housing includes a probe housing and a torque guide wire connected to the probe housing; the ultrasonic transparent transducer is also connected to a signal line, which is used to transmit electrical signals and includes a grounding wire.
[0016] A photoacoustic endoscopic imaging system further includes a pulsed laser, a motor, a data acquisition module, and a computer; The computer is used to control the operation of the system and to control the motor and the pulsed laser to perform scanning. The motor is used to drive the probe to rotate at a constant speed and retract; The laser emitted by the pulsed laser enters the optical module via a coupler. After being shaped by the meta-transparent ultrasonic transducer, it irradiates the scanned object and excites a photoacoustic effect. The generated ultrasonic signal is converted into an electrical signal by the meta-transparent ultrasonic transducer. After being acquired by the data acquisition module, it is transmitted to the computer for image reconstruction and display. The computer stores and processes the acquired data to complete the image reconstruction.
[0017] The above-described solution of the present invention has at least the following beneficial effects: By integrating a meta-optical structure into the matching layer of a transparent ultrasonic transducer, the matching layer not only performs its primary function of acoustic impedance matching but also possesses active optical wavefront modulation capabilities. This achieves integrated acoustic and optical functions, enabling the acquisition of a long focal depth focused beam without increasing probe length or the number of components. This effectively solves the limitation of traditional transparent transducers that can only transmit light but cannot shape the beam. It eliminates the need for mechanical focusing or external optical lenses, resulting in a simple structure, high stability, and small package size. The natural coaxial photoacoustic channel eliminates the need for additional optical path alignment, maintaining relatively stable photoacoustic excitation efficiency even when there are surface undulations in biological tissues or probe position deviations. This improves imaging consistency and signal-to-noise ratio, making it particularly suitable for photoacoustic endoscopic imaging scenarios. Attached Figure Description
[0018] To more clearly illustrate the technical solutions implemented in this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a schematic diagram of the photoacoustic endoscope probe used in this invention.
[0020] Figure 2 This is a flowchart of the photoacoustic endoscopy system used in this invention.
[0021] The following are the symbols in the attached diagram: 1-Signal line, 2-Single-mode fiber, 3-Transparent ultrasonic transducer, 4-Right-angle reflector, 5-Probe housing, 6-Torque guide wire. Detailed Implementation
[0022] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
[0023] Miniature photoacoustic endoscope probe, including a super-transparent ultrasonic transducer, optical module and protective housing; The meta-transparent ultrasonic transducer includes a transparent piezoelectric material, a transparent electrode layer, and a transparent matching layer. The exit end face of the matching layer integrates a meta-optical structure. The meta-optical structure is composed of subwavelength-scale meta-units arranged according to a phase distribution scheme. By spatially modulating the wavefront of the emitted light, a focused beam with a specific optical field distribution is formed at the front end of the probe. The optical module is used to guide the light beam to the meta-transparent ultrasonic transducer. The light beam, after being adjusted by the meta-optical structure, is used to emit into biological tissue to excite the photoacoustic effect. The aforementioned meta-transparent ultrasonic transducer is used to convert the acoustic signal generated by the photoacoustic effect into an electrical signal that can be used for imaging. The protective housing is used to house the meta-transparent ultrasonic transducer and optical module.
[0024] In this invention, a meta-optical structure is directly integrated into the exit face of the matching layer of the transparent ultrasonic transducer. This allows the matching layer, which originally only had a light-transmitting function, to not only achieve acoustic impedance matching but also to actively control the spatial phase modulation of the emitted light wavefront, thus realizing the integrated acoustic and optical functions. Since the beam shaping function is built into the transducer, there is no need to add a focusing lens or beam shaping device to the probe, effectively avoiding the increased length, larger packaging volume, and optical path alignment problems caused by external optical components. This results in a more compact overall probe structure and a significantly shorter rigid section. Simultaneously, the excitation light exits along the same axis after passing through the transparent transducer, and the acousto-optic channels are naturally coaxial, fundamentally eliminating the eccentricity error caused by assembly or bending of discrete optical paths, eliminating the need for mechanical focusing or complex calibration. Meta-optical structures can form a long focal depth focused beam at the probe tip by precisely modulating the wavefront. Even when there are undulations on the surface of biological tissue or deviations in the radial position of the probe, the spot size remains stable over a long axial range and the excitation efficiency fluctuates little, thereby significantly improving the axial consistency and signal-to-noise ratio of photoacoustic imaging. This is especially suitable for endoscopic imaging scenarios in narrow cavities such as the digestive tract and blood vessels.
[0025] In this invention, the phase distribution of the meta-optical structure is based on the phase superposition of an axial pyramid and an off-axis compensation term, and its expression is as follows: φ(r,θ) = -k(r·sinα + β·r 2 ) + γ·cosθ; Where r is the radial distance, θ is the azimuth angle, k is the wave number, α is the base angle parameter of the axial pyramid, β is the second phase compensation coefficient, and γ is the off-axis phase compensation coefficient.
[0026] In a preferred embodiment of the present invention, the target phase distribution of the metalens is first determined based on the performance requirements of photoacoustic endoscopy for depth of focus and resolution. The entire array surface employs pure phase modulation, and the phase distribution formula is based on the superposition of an axial pyramid phase and an off-axis compensation term. This phase distribution generates a long-depth-of-focus, diffraction-free beam through the axial pyramid term, ensuring that the beam spot maintains dimensional stability over a long axial range, effectively overcoming the inherent limitation of the short depth of focus of traditional Gaussian beams. The secondary phase compensation term is used to regulate the lateral energy distribution of the beam spot, suppressing the common sidelobe oscillations of axial pyramid beams and forming a more uniform flat-top light field. The off-axis compensation term is used to correct the wavefront tilt caused by the deflection of the internal reflector of the probe or assembly errors, ensuring that the focused beam spot can still maintain good symmetry and energy concentration under off-axis illumination conditions. The synergistic effect of these three factors allows the miniature probe to simultaneously obtain a long-depth-of-focus and high-resolution excitation beam spot under limited aperture conditions, significantly improving the imaging consistency and signal-to-noise ratio of photoacoustic endoscopy on complex tissue surfaces.
[0027] In this invention, the phase distribution is obtained through the following optimization: the target phase distribution is discretized into a phase matrix, and a global search algorithm based on Bayesian optimization is used to optimize the parameter combination (α, β, γ). The mean square error between the on-axis light intensity distribution and the ideal flat-top function is used as the objective function. In each iteration, the on-axis light field distribution is calculated using the Rayleigh-Sommerfeld diffraction integral formula to evaluate the performance of candidate solutions. After multiple iterations, the optimal phase matrix is obtained.
[0028] In a preferred embodiment of the present invention, the phase distribution is discretized into a phase matrix of N×N pixels. A global search algorithm based on Bayesian optimization is used to optimize the key parameter combination (α, β, γ). The mean square error between the on-axis light intensity distribution and the ideal flat-top function is used as the objective function. In each iteration, the Rayleigh-Sommerfeld diffraction integral formula is used. ; The on-axis optical field distribution is calculated to evaluate the performance of candidate solutions, and the optimal phase matrix is obtained after multiple iterations. This optimization method employs a Bayesian global search strategy, using the Rayleigh-Sommerfeld diffraction integral as a precise evaluation criterion. It efficiently traverses the parameter space and avoids getting trapped in local optima, thus rapidly converging to the globally optimal phase combination. The resulting phase matrix allows the on-axis intensity distribution to accurately approximate the ideal flat-top function, effectively suppressing sidelobes, balancing axial energy, and achieving uniform intensity distribution over long focal depths. This significantly improves the stability of photoacoustic excitation efficiency and imaging consistency.
[0029] In this invention, the metacellular unit adopts a regular square frustum shape, and the unit period p is fixed as a specific proportion of the design wavelength λ, satisfying... , where 0 < < 1; The design variable for each hyperstructure unit is height. With the side length of the upper surface The side length of the lower surface is fixed. .
[0030] The structural parameters of the metaunit are determined as follows: a simulation model of the regular square frustum metaunit is established, and different ( The phase response and transmittance are calculated by combining the parameters to generate a phase-structure parameter database. The required phase values at each position in the target phase matrix are matched with the database, and the value with the smallest phase error is selected under the condition of satisfying the transmittance threshold. The combination serves as the unit structure at that location.
[0031] In a preferred embodiment of the present invention, the pixel positions of the optimized phase matrix are then matched with corresponding supercell structures. The supercells adopt a regular square truncated pyramid shape, and the cell period is... Fixed to the design wavelength A specific proportion ( , 0< <1), the design variable for each unit is height. With the side length of the upper surface The lower surface side length is fixed at p. A simulation model of a regular square frustum metastructure is built using the open-source software torcwa (a GPU-accelerated rigorous coupled-wave analysis (RCWA) tool based on PyTorch). Parameters such as element period, incident wavelength, and material refractive index are set. The model is then analyzed by scanning different... The phase response and transmittance corresponding to each geometric parameter are calculated in combination to generate a phase-structure parameter lookup database. Then, the required phase values at each position in the target phase matrix are matched with the database, and the value with the smallest phase error is selected under the condition of satisfying the transmittance threshold. The components are combined as the unit structure at that location; finally, a layout design file is generated based on the matched unit structure parameters, and the transparent matching layer is directly fabricated on the front face, so that the matching layer can achieve spatial phase modulation of the excitation light wave passing through it while completing acoustic impedance matching.
[0032] This truncated square prism shape, with height and upper surface side length as dual design variables and a fixed lower surface side length, offers greater freedom in phase modulation compared to cylindrical or square prism structures. It achieves 0-2π phase coverage at a relatively low structure height, reducing the aspect ratio of micro / nano fabrication and effectively improving fabrication stability and yield. Simultaneously, by pre-scanning variable combinations to establish a phase-structure parameter database and then using transmittance thresholds to screen and match optimal units, it is possible to quickly and accurately achieve the reverse mapping of the target phase distribution to the actual structure. This ensures that each metaunit provides precise phase modulation while meeting sufficient transmittance requirements, thereby guaranteeing the overall control precision and light energy utilization efficiency of the meta-optical structure.
[0033] In this invention, the meta-optical structure is fabricated on the exit end face of the transparent matching layer using micro-nano 3D printing technology.
[0034] In this invention, by determining the distance between the optical fiber and the right-angle mirror, as well as the height of the meta-transparent ultrasonic transducer, the complex amplitude of the beam can be precisely maintained while expanding the beam diameter, keeping it in a Gaussian-like beam state to meet the requirements of the meta-optical structure for incident light. In this application, a Gaussian-like beam refers to a beam whose complex amplitude distribution is sufficiently close to that of an ideal fundamental mode Gaussian beam, allowing the meta-optical structure to still effectively modulate according to the designed phase distribution. Specifically, it satisfies one or more of the following conditions: mode matching efficiency not less than 90%, root mean square wavefront phase deviation not greater than λ / 10, beam quality factor not greater than 1.5, and fundamental mode energy ratio not less than 90%, where λ represents the wavelength of the light.
[0035] In a preferred embodiment of the present invention, this fabrication method utilizes micro-nano 3D printing technology to directly mold the meta-optical structure onto the exit face of the matching layer, eliminating the need for additional transfer or bonding steps and ensuring a stable bond and precise alignment between the meta-unit and the matching layer. Simultaneously, by optimizing the distance between the optical fiber and the right-angle mirror, as well as the transducer height, the beam can be effectively expanded to increase the illumination field of view while maintaining an approximate standard Gaussian beam complex amplitude distribution. This ensures a high degree of matching between the incident light field and the design premise of the meta-optical structure, thereby guaranteeing that the phase modulation accuracy of the meta-unit on the light wavefront is consistent with theoretical expectations, ultimately achieving high-quality long-focus depth-of-focal-length focused beam output.
[0036] In this invention, the optical module includes a single-mode fiber and a right-angle mirror; the right-angle mirror is disposed between the emitting end of the single-mode fiber and the meta-transparent ultrasonic transducer, and is used to reflect the light beam to the matching layer.
[0037] In this invention, the protective housing includes a probe housing and a torque guide wire connected to the probe housing; the ultrasonic transparent transducer is also connected to a signal line, which is used to transmit electrical signals and includes a grounding wire.
[0038] In a preferred embodiment of the invention, this optical layout uses a right-angle mirror to deflect the fiber-emitter beam by 90° and guide it to the transducer matching layer. This achieves a compact optical path within the limited radial dimensions of the probe, ensuring lateral illumination while maximizing space utilization. The probe housing, in conjunction with a torque guide wire, ensures both structural integrity and sealing safety during in vivo rotational scanning, while also providing mechanical drive for 360° circular imaging. The signal line with an attached ground wire effectively suppresses electromagnetic interference and ensures high-fidelity transmission of weak photoacoustic signals. These three elements work together to ensure stable and clear imaging data during dynamic rotational scanning.
[0039] A photoacoustic endoscopic imaging system further includes a pulsed laser, a motor, a data acquisition module, and a computer; The computer is used to control the operation of the system and to control the motor and the pulsed laser to perform scanning. The motor is used to drive the probe to rotate at a constant speed and retract; The laser emitted by the pulsed laser enters the optical module via a coupler. After being shaped by the meta-transparent ultrasonic transducer, it irradiates the scanned object and excites a photoacoustic effect. The generated ultrasonic signal is converted into an electrical signal by the meta-transparent ultrasonic transducer. After being acquired by the data acquisition module, it is transmitted to the computer for image reconstruction and display. The computer stores and processes the acquired data to complete the image reconstruction.
[0040] In another preferred embodiment of the present invention, a metalens design method is provided that is directly integrated into the front end face of the matching layer of a transparent ultrasonic transducer. First, based on the performance requirements of photoacoustic endoscopy for depth of focus and resolution, the target phase distribution of the metalens is determined. The entire array surface employs pure phase modulation, and the phase distribution formula is based on the axial pyramid phase superposition with off-axis compensation terms, and its expression is: ; Where r is the radial distance, θ is the azimuth angle, k is the wavenumber, α is the axial pyramid base angle parameter, β is the quadratic phase compensation coefficient, γ is the off-axis phase compensation coefficient, the array diameter is designed to be several hundred micrometers, and the target focal depth is set to the millimeter range; then the above phase distribution is discretized into an N×N pixel phase matrix, and a Bayesian optimization-based global search algorithm is used to optimize the key parameter combination (α, β, γ), with the mean square error between the on-axis light intensity distribution and the ideal flat-top function as the objective function. In each iteration, the Rayleigh-Sommerfeld diffraction integral formula is used: ; The optical field distribution along the computational axis is used to evaluate the performance of candidate solutions, and the optimal phase matrix is obtained after multiple iterations. Then, the pixel positions of the optimized phase matrix are matched with corresponding supercell structures. The supercells adopt a regular square frustum shape, and the cell period is... Fixed to the design wavelength At a specific ratio, the design variable for each unit is height. With the side length of the upper surface The side length of the lower surface is fixed. A simulation model of a regular square frustum metastructure was built using the open-source software Torcwa. Parameters such as element period, incident wavelength, and material refractive index were set. The model was then analyzed by scanning different (…). The phase response and transmittance corresponding to each geometric parameter are calculated in combination to generate a phase-structure parameter lookup database. Then, the required phase values at each position in the target phase matrix are matched with the database, and the value with the smallest phase error is selected under the condition of satisfying the transmittance threshold. The components are combined as the unit structure at that location; finally, a layout design file is generated based on the matched unit structure parameters, and the transparent matching layer is directly fabricated on the front face, so that the matching layer can achieve spatial phase modulation of the excitation light wave passing through it while completing acoustic impedance matching.
[0041] In another preferred embodiment of the present invention, a photoacoustic endoscope probe based on a transparent ultrasonic transducer is provided, comprising a transparent transducer body and a meta-optical structure disposed on a matching layer of the transparent transducer. The probe includes an optical module, an acoustic module, and a protective shell.
[0042] like Figure 1 As shown, the optical module includes a single-mode fiber 2, a right-angle mirror 4, and a meta-optical structure in a transparent ultrasonic transducer 3. After the mirror reflects the light beam to the matching layer of the transparent ultrasonic transducer, the meta-structure of the matching layer further shapes the light beam to form a long depth of focus, high-resolution light beam. The shaped light beam is reflected out of the protective shell and illuminates the scanning object, thereby exciting the photoacoustic effect.
[0043] like Figure 1 As shown, the acoustic module is specifically composed of a transparent ultrasonic transducer 3, which has a high-efficiency sound wave conversion capability and is equipped with an auxiliary signal line 1 connected to it for transmitting the sound wave signal generated by the transducer. The signal line 1 also includes a grounding wire, the main function of which is to ensure the electrical safety of the entire acoustic module and prevent equipment failure caused by static electricity or other electrical interference.
[0044] like Figure 1 The protective housing includes a probe housing 5 and a torque guide wire 6 connected to the housing. The housing can ensure that the optical fiber and transparent transducer are not damaged in the living body environment and prevent liquid from entering the probe and affecting the propagation of light. The guide wire conducts torque, allowing the probe to rotate and scan.
[0045] In another preferred embodiment of the present invention, the imaging system and imaging method are as follows: like Figure 2The computer manages the entire system, activating the photoacoustic endoscope system and controlling the motor and pulsed laser for scanning. The motor drives the probe to rotate at a constant speed and retract. The laser emitted by the pulsed laser enters the optical fiber through a coupler. The beam illuminates the transparent transducer under the action of a mirror, and the beam is further shaped after passing through a matching layer. The focused light illuminates the scanned object, exciting a photoacoustic effect and generating an ultrasonic signal. The ultrasonic signal is converted into an electrical signal by the ultrasonic transducer and sent back to the computer. Finally, the acquired signals are used for image reconstruction and display. The computer stores and processes the acquired data to complete the photoacoustic image reconstruction.
[0046] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A miniature photoacoustic endoscope probe, characterized in that, Includes a super-transparent ultrasonic transducer, optical module, and protective housing; The meta-transparent ultrasonic transducer includes a transparent piezoelectric material, a transparent electrode layer, and a transparent matching layer. The exit end face of the matching layer integrates a meta-optical structure. The meta-optical structure is composed of subwavelength-scale meta-units arranged according to a phase distribution scheme. By spatially modulating the wavefront of the emitted light, a focused beam with a specific optical field distribution is formed at the front end of the probe. The optical module is used to guide the light beam to the meta-transparent ultrasonic transducer. The light beam, after being adjusted by the meta-optical structure, is used to emit into biological tissue to excite the photoacoustic effect. The aforementioned meta-transparent ultrasonic transducer is used to convert the acoustic signal generated by the photoacoustic effect into an electrical signal that can be used for imaging. The protective housing is used to house the meta-transparent ultrasonic transducer and optical module.
2. The miniature photoacoustic endoscope probe according to claim 1, characterized in that, The phase distribution of the meta-optical structure is based on the phase superposition of an axial pyramid and an off-axis compensation term, and its expression is as follows: ； in, Radial distance, It is the azimuth angle. For wave number, For the base angle parameters of the axial pyramid, These are the secondary phase compensation coefficients. This is the off-axis phase compensation coefficient.
3. The miniature photoacoustic endoscope probe according to claim 2, characterized in that, The phase distribution is obtained through the following optimization: the target phase distribution is discretized into a phase matrix, and a Bayesian optimization-based global search algorithm is used to optimize the parameter combinations ( , , The optimization is carried out with the mean square error between the on-axis light intensity distribution and the ideal flat-top function as the objective function. In each iteration, the Rayleigh-Sommerfeld diffraction integral formula is used to calculate the on-axis light field distribution to evaluate the performance of candidate solutions. After multiple iterations, the optimal phase matrix is obtained.
4. The miniature photoacoustic endoscope probe according to claim 3, characterized in that, The meta-unit adopts a regular square frustum shape, and the unit period p is fixed as a specific proportion of the design wavelength λ, satisfying... , where 0 < < 1; The design variable for each hyperstructure unit is height. With the side length of the upper surface The side length of the lower surface is fixed. .
5. The miniature photoacoustic endoscope probe according to claim 4, characterized in that, The structural parameters of the metaunit are determined as follows: a simulation model of the regular square frustum metaunit is established, and different ( The phase response and transmittance are calculated by combining the parameters to generate a phase-structure parameter database. The required phase values at each position in the target phase matrix are matched with the database, and the value with the smallest phase error is selected under the condition of satisfying the transmittance threshold. The combination serves as the unit structure at that location.
6. The miniature photoacoustic endoscope probe according to claim 5, characterized in that, The meta-optical structure is fabricated on the exit face of the transparent matching layer using micro-nano 3D printing technology.
7. The miniature photoacoustic endoscope probe according to claim 6, characterized in that, By determining the distance between the optical fiber and the right-angle mirror, as well as the height of the meta-transparent ultrasonic transducer, it is possible to precisely maintain the complex amplitude of the beam while expanding the beam diameter, keeping it in a Gaussian-like beam state to meet the requirements of the meta-optical structure for incident light.
8. The miniature photoacoustic endoscope probe according to claim 7, characterized in that, The optical module includes a single-mode fiber and a right-angle mirror; the right-angle mirror is disposed between the emitting end of the single-mode fiber and the meta-transparent ultrasonic transducer, and is used to reflect the light beam to the matching layer.
9. The miniature photoacoustic endoscope probe according to claim 8, characterized in that, The protective housing includes a probe housing and a torque guide wire connected to the probe housing; The ultra-transparent ultrasonic transducer is also connected to a signal line, which is used to transmit electrical signals and includes a grounding wire.
10. A photoacoustic endoscopic imaging system, characterized in that, The miniature photoacoustic endoscope probe, as described in any one of claims 1 to 9, further includes a pulsed laser, a motor, a data acquisition module, and a computer; The computer is used to control the operation of the system and to control the motor and the pulsed laser to perform scanning. The motor is used to drive the probe to rotate at a constant speed and retract; The laser emitted by the pulsed laser enters the optical module via a coupler. After being shaped by the meta-transparent ultrasonic transducer, it irradiates the scanned object and excites a photoacoustic effect. The generated ultrasonic signal is converted into an electrical signal by the meta-transparent ultrasonic transducer. After being acquired by the data acquisition module, it is transmitted to the computer for image reconstruction and display. The computer stores and processes the acquired data to complete the image reconstruction.