Arrayed optical fiber ultrasonic probe based on cross-suspended beam flat concave cavity and imaging system

Abstract

The application discloses a kind of array optical fiber ultrasonic probe based on cross cantilever flat concave cavity and imaging system, belong to ultrasonic detection field.Array optical fiber ultrasonic probe includes the N cross cantilever flat concave cavity array element prepared using based on two-photon polymerization 3D printing, array element includes optical fiber, support cavity, cross cantilever, concave focusing sensitizing diaphragm, reflective film.Ultrasonic pressure acts on concave focusing sensitizing diaphragm, and resonant cavity will change length along with the vibration of diaphragm.This application can realize the detection of ultrasonic signal by detecting the change of reflected light intensity, and the concave focusing sensitizing diaphragm can effectively ensure the beam focusing interference of Fabry-Perot resonant cavity, improve the sensitivity of ultrasonic detection, and the cross cantilever can increase the mechanical response degree of sensor ultrasonic, increase the range.Using the process of two-photon polymerization 3D printing can effectively control the working wavelength of sensor, increase the multiplexing number of array.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic detection, and more specifically, relates to an array-type fiber optic ultrasonic probe and imaging system based on a cross-shaped cantilever flat-concave cavity. Background Technology

[0002] Photoacoustic imaging is a novel non-contact, high-precision, and non-destructive ultrasonic testing technology. It overcomes the optical diffraction limit and combines the advantages of high resolution and large imaging depth. It is now widely used in non-destructive testing, especially in medical imaging such as endoscopy and skin microvascular imaging. Its principle can be briefly described as follows: when a pulsed laser irradiates the surface of an object, each absorber absorbs the light energy, thereby generating a photoacoustic signal. This signal is acquired by an ultrasonic transducer, and the obtained data is then processed and reconstructed using algorithms to obtain an image and functional information of the object.

[0003] Ultrasonic detectors are key components in photoacoustic imaging. Compared to electrical ultrasonic sensors, Fabry-Perot ultrasonic sensors based on fiber optic endfaces offer advantages such as small size, wide frequency response, high detection sensitivity, and resistance to electromagnetic interference. Traditional fiber optic Fabry-Perot ultrasonic sensor structures utilize a three-layer film structure fabricated at the fiber endface or a hollow sleeve fused to the fiber endface to construct a Fabry-Perot cavity. The outermost reflective film shifts under the influence of ultrasonic sound pressure, causing a corresponding change in cavity length. The reflected light intensity is then used to demodulate the corresponding ultrasonic information.

[0004] The sensitivity of Fabry-Perot optical sensors for ultrasound detection is determined by both phase sensitivity and mechanical sensitivity. Traditional acoustic response structures typically use a single, circular diaphragm, limiting further improvements in the sensitivity of this type of sensor. Scanning systems based on single-point ultrasound probes have long data acquisition times, requiring several minutes or even tens of minutes to obtain a complete reconstructed image, which cannot meet the requirements of clinical applications. Furthermore, due to the use of mechanical scanning at thousands of detection positions and the long data acquisition time, vibrations of the mechanical displacement stage and long-term random parameter changes in the instrument inevitably introduce random errors into the detection results, severely affecting the image quality and the reliability and stability of the results. However, limitations in manufacturing processes make it difficult to guarantee the sensitivity and operating point consistency of fiber optic Fabry-Perot sensors, increasing the difficulty of reusing fiber optic sensors. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to overcome the problems of poor wavelength consistency, low sensitivity, complex manufacturing process, and large size of existing fiber optic ultrasonic detection arrays. It provides an array-type fiber optic ultrasonic probe and imaging system based on a cross-beam concave cavity to improve the sensitivity and multiplexing capacity of the array sensing. In conjunction with a corresponding system, it can receive three-dimensional data of ultrasonic signals in real time, quickly, and accurately.

[0006] To achieve the above objectives, the present invention provides an array-type fiber optic ultrasonic probe based on a cross-beam concave-cavity array, comprising an array of N cross-beam concave-cavity array elements, where N is a positive integer; each cross-beam concave-cavity array element includes an optical fiber, a supporting cavity, a concave focusing and sensitizing diaphragm, a first reflective film, a second reflective film, and a cross-beam; the upper surface of the supporting cavity is used to support the concave focusing and sensitizing diaphragm, the concave focusing and sensitizing diaphragm is connected to the edge of the upper surface of the supporting cavity through the cross-beam, and the upper surface of the concave focusing and sensitizing diaphragm is covered with a second reflective film;

[0007] The supporting cavity is cylindrical and filled with liquid or gas;

[0008] The supporting cavity, the concave focusing and sensitizing diaphragm, the first reflective film, the second reflective film, and the cross-shaped cantilever beam constitute a cross-shaped cantilever Fabry-Perot resonant cavity.

[0009] The supporting cavity, concave focusing and sensitizing film, and cross-shaped cantilever beam are all two-photon polymerization 3D printed structures.

[0010] The basic principle of this invention for detecting ultrasound is as follows:

[0011] The first reflective film, the second reflective film, the supporting cavity, the concave focusing and sensitizing diaphragm, and the cross-shaped cantilever beam constitute a plano-concave Fabry-Perot resonant cavity. In the ultrasonic field, the ultrasonic waves generated or scattered by the sample under test have a certain pressure, causing the concave focusing and sensitizing diaphragm to deflect. The length of the Fabry-Perot cavity changes accordingly with the ultrasonic waves. The concave focusing and sensitizing diaphragm in the middle increases the receiving area of ​​the ultrasonic signal. Furthermore, the concave structure and the flat end face constitute a plano-concave Fabry-Perot cavity, which can provide a higher contrast interference spectrum, thereby improving the optical detection sensitivity of the ultrasonic sensing structure. The four fixed beams form a cross-shaped cantilever beam, which keeps the concave focusing and sensitizing diaphragm as parallel as possible to the flat end face of the Fabry-Perot cavity during ultrasonic response. The structure of the cantilever beam can also increase the vibration amplitude of the concave focusing and sensitizing diaphragm, improving the mechanical sensitivity of the ultrasonic sensing structure. The probe light emitted by the laser is coupled into the Fabry-Perot resonant cavity, interferes within the resonant cavity, and then returns, finally being received by the photodetector. The stronger the ultrasonic signal, the greater the deflection displacement of the concave focusing and sensitizing diaphragm, the greater the change in the cavity length of the Fabry-Perot cavity, and the corresponding change in the light intensity received by the photodetector. Therefore, the magnitude of the ultrasonic signal can be obtained by demodulating the intensity of the reflected detection light signal.

[0012] This invention also provides a sensing method for an array-type fiber optic ultrasonic probe based on a cross-shaped cantilever flat-concave cavity, comprising the following steps:

[0013] The probe light, coupled via optical fiber, first enters the first reflective film, then passes through the hollow ambient medium cavity formed by the supporting cavity, and then enters the concave focusing and sensitizing film, finally being reflected by the second reflective film. The reflected light interferes with the probe light within the cross-shaped cantilever beam and the plano-concave cavity structure, returning via the original optical fiber path. When external ultrasound is incident, the ultrasonic waves act on the concave focusing and sensitizing film, causing it to flex and shift under the support of the cross-shaped cantilever beam. This shift changes the optical path of the reflected light from the second reflective film, thus altering the cavity length of the Fabry-Perot cavity, and consequently changing the interference intensity of the Fabry-Perot resonator. The reflected light then propagates backward through the optical fiber and is finally received by the photodetector. The magnitude of the ultrasonic signal is obtained by demodulating the intensity of the reflected light.

[0014] This invention also provides a method for fabricating an array-type fiber optic ultrasonic probe based on a cross-shaped cantilever flat-concave cavity, comprising the following steps:

[0015] S1. Arrange and fix multiple optical fibers according to the number and arrangement of array elements, and cut them into corresponding optical fiber segments;

[0016] S2. Using fiber bundle or fiber array fabrication process, the individual fiber units are softened and bonded together to form an integral fiber bundle. Finally, the fiber bundle is encapsulated with a sleeve to protect the fiber bundle and provide a connection interface.

[0017] S3. After the optical fibers are bundled together, the output end face is polished flat; the end face is then cleaned.

[0018] S4. Multilayer silicon dioxide and titanium dioxide are sequentially and alternately deposited onto the end face of the optical fiber bundle using magnetron sputtering to form a dielectric film with optical selective transmission properties;

[0019] S5. Fix the fiber bundle on the printing platform, use two-photon polymerization 3D printing technology to align each fiber unit of the fiber bundle, and process a cross-beam flat-concave structure on the surface of the dielectric film.

[0020] S6. On the outside of the cross-shaped cantilever flat-concave structure, a second reflective film is prepared by magnetron sputtering, using the same materials as S2, silicon dioxide and titanium dioxide, which are alternately deposited on the outside of the structure.

[0021] This invention also provides an imaging system, including a laser, a 1×N fiber coupler, an array-type fiber optic ultrasonic probe based on a cross-beam concave cavity, an N-channel fiber optic circulator, a photodetector array, a data acquisition module, and a terminal controller; the output end of the laser is connected to the 1×N fiber coupler, the array-type fiber optic ultrasonic probe is connected to the beam splitting port of the 1×N fiber coupler through the N-channel fiber circulator, the output end of the N-channel fiber circulator is connected to the photodetector array, the photodetector array is connected to the data acquisition module, and the terminal controller is connected to the laser, the photodetector array, and the data acquisition module respectively;

[0022] After receiving the signal, the data acquisition module transmits it to the terminal controller, which performs ultrasonic signal filtering, noise reduction, and enhancement processing. The processed signal is then used to reconstruct three-dimensional or two-dimensional image information and displayed on the monitor.

[0023] The terminal controller includes a data processing module, an image processing module, and a timing control module. The terminal controller trigger source is connected to a photodetector, which is connected to a data acquisition module. Under the control of the controller trigger signal, the photodetector array converts the received optical ultrasonic signal into an electrical signal and transmits the real-time electro-ultrasonic signal data to the data acquisition module. The data acquisition module collects and stores the data and transmits the ultrasonic signal data to the terminal controller.

[0024] The system operates on the following principle:

[0025] (1) Different trigger sources are used in different working environments; in photoacoustic imaging mode, the excitation laser irradiates the sample, the sample absorbs the pulsed laser energy and generates an ultrasonic signal, and the ultrasonic probe performs detection. The timing control circuit realizes the synchronous triggering of the excitation laser signal emission and the acquisition of the detection light signal; in ultrasonic detection mode, the ultrasonic emission source irradiates the sample, the sample reflects the ultrasonic signal, and the ultrasonic probe performs detection. The timing control circuit realizes the synchronous triggering of the ultrasonic signal emission and the acquisition of the detection light signal.

[0026] (2) Array-type fiber optic ultrasound probe: It consists of a fiber optic array and a sensitized Fabry-Perot structure. The concave focusing sensitizing diaphragm and the cross-shaped cantilever structure receive the ultrasonic waves generated by the sample in the form of forced vibration. The ultrasonic waves indirectly modulate the intensity of the reflected light from the Fabry-Perot cavity through the axial displacement of the sensitizing diaphragm.

[0027] (3) Ultrasonic signal reception and conditioning: The ultrasonic signals received by the fiber optic ultrasonic array at their respective positions are converted into electrical signals by the corresponding photodetectors carrying photoacoustic information. The electrical signals are collected and recorded in real time by the data acquisition module and transmitted to the terminal controller for filtering and noise reduction.

[0028] (4) Image processing and display: The conditioned ultrasound signal is reconstructed in two or three dimensions by the image processing system using reconstruction algorithms. The reconstructed data is then enhanced, features are extracted, classified and identified, and the resulting imaging data is output to the display unit.

[0029] The present invention also provides an imaging method, comprising the following steps:

[0030] The probe light emitted by the laser is coupled into the incident end a of the N-way fiber optic circulator through the 1×N fiber coupler, and injected into the array-type fiber optic ultrasonic probe from the b end of the N-way fiber optic circulator. The probe light interferes in the sensing structure of the array-type fiber optic ultrasonic probe and is modulated by the external ultrasonic signal. The modulated probe light, carrying ultrasonic information, is reflected from the array-type fiber optic ultrasonic probe, enters again through the b end of the N-way fiber optic circulator, and exits from the c end of the N-way fiber optic circulator. The exited light signal is received by the photodetector array. The photodetector array converts the light signal into a piezoelectric signal, which is received by the data acquisition module and transmitted to the terminal controller for ultrasonic signal filtering, noise reduction, and enhancement processing. The processed signal is then used to reconstruct three-dimensional or two-dimensional image information for imaging. The terminal controller is simultaneously connected to the photodetector array and an external trigger source. Under the control of the trigger signal, the photodetector array synchronously acquires the ultrasonic signal.

[0031] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following results.

[0032] Beneficial effects:

[0033] 1. The array-type fiber optic ultrasonic probe based on a cross-beam concave cavity provided by this invention has a small sensing structure size and a precise array unit arrangement, which can provide high spatial resolution. The cross-beam can increase the ultrasonic mechanical response of the sensor and increase the measurement range.

[0034] 2. The concave focusing and sensitizing diaphragm and the planar reflector at the end face of the optical fiber in the array-type fiber optic ultrasonic probe based on the cross-beam concave cavity provided by the present invention constitute a concave Fabry-Perot resonant cavity structure, generating a high-contrast interference spectrum, which can effectively improve the optical sensitivity of the sensing structure.

[0035] 3. The four supporting beams in the array-type fiber optic ultrasonic probe based on a cross-beam concave cavity provided by the present invention ensure the horizontality of the concave focusing and sensitizing diaphragm and the plane mirror, increase the stability of the resonant cavity, and the beam structure can increase the vibration amplitude of the diaphragm, effectively improving the mechanical sensitivity of the sensing structure.

[0036] 4. The length of the resonant cavity determines the position of the working wavelength. Using two-photon polymerization 3D printing technology, a cross-beam plano-concave resonant cavity was fabricated, which can control the length of the resonant cavity to the order of hundreds of nanometers, increase the number of multiplexed Fabry-Perot resonant sensors, and reduce costs by using a single-wavelength laser.

[0037] 5. The array-type fiber optic ultrasonic probe based on a cross-shaped cantilever flat concave cavity provided by the present invention can receive and record three-dimensional data of photoacoustic imaging in real time and quickly.

[0038] 6. The ultrasonic probe and imaging system provided by this invention have the advantages of high sensitivity, good consistency, stable performance and low cost, and can be widely used in the fields of biology, medicine and materials analysis. Attached Figure Description

[0039] Figure 1 A schematic diagram of the array element structure of the array-type fiber optic ultrasonic probe based on a cross-shaped cantilever flat-concave cavity provided by the present invention.

[0040] Figure 2 A top view of the array elements of the array-type fiber optic ultrasonic probe based on a cross-shaped cantilever flat-concave cavity provided by the present invention.

[0041] Figure 3 SEM images of the array elements of the array-type fiber optic ultrasonic probe based on a cross-shaped cantilever flat-concave cavity provided by the present invention.

[0042] Figure 4 A front view of the array-type fiber optic ultrasonic probe based on a cross-shaped cantilever flat-concave cavity provided by the present invention;

[0043] Figure 5 This is a schematic diagram of the ultrasound imaging system in this invention;

[0044] Reference numerals: 1. Laser; 2. 1×N fiber optic coupler; 3. Array-type fiber optic ultrasonic probe based on a cross-beam concave-convex cavity; 3-1. Fiber optic cable; 3-2. Support cavity; 3-3. Concave focusing and sensitizing diaphragm; 3-4. First reflective film; 3-5. Second reflective film; 3-6. Cross-beam; 3-7. Cross-beam concave-convex cavity array element; 3-8. Sleeve; 4. N-channel fiber optic circulator; 5. Photodetector array; 6. Data acquisition module; 7. Terminal controller. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0046] This invention provides an array-type fiber optic ultrasonic probe based on a cross-shaped cantilever flat-concave cavity. The enhanced-sensitivity structure is prepared by two-photon polymerization 3D printing technology. First, a reflective thin film is prepared on the end face of the optical fiber. The printed ultrasonic sensing structure is located on the surface of the thin film. Its structure is compact, and the volume size of the sensing structure on a single array element is less than 125 micrometers. Furthermore, by utilizing the cross-shaped sensitive structure, it is possible to detect ultrasonic waves.

[0047] Combination Figure 1 and Figure 2 As shown, the technical solution adopted in this invention is an ultrasonic sensing structure based on a cross-beam concave-convex cavity, comprising: an optical fiber 3-1, a supporting cavity 3-2, a concave focusing and sensitizing diaphragm 3-3, a first reflective film 3-4, a second reflective film 3-5, and a cross-beam 3-6. The supporting cavity 3-2, the concave focusing and sensitizing diaphragm 3-3, and the cross-beam 3-6 are all two-photon polymerization 3D printed structures. The lower surface of the supporting cavity 3-2 is connected to the end face of the optical fiber 3-1 through the first reflective film 3-4. The upper surface of the supporting cavity 3-2 supports the concave focusing and sensitizing diaphragm. The cross-beam 3-6 connects to the supporting cavity 3-2 to maintain structural stability. The upper surface of the concave focusing and sensitizing diaphragm 3-3 is covered with the second reflective film 3-5. The supporting cavity 3-2, the concave focusing and sensitizing diaphragm 3-3, the first reflective film 3-4, the second reflective film 3-5, and the cross-beam 3-6 constitute a Fabry-Perot resonant cavity.

[0048] The optical fiber 3-1 has a diameter of 125 micrometers and is used to conduct the detection light. In the photoacoustic detection mode, a double-clad optical fiber can be used. The excitation light is transmitted through the outer cladding and irradiates the sample to generate an ultrasonic signal.

[0049] The supporting cavity adopts a hollow cylindrical structure with a wall thickness of 3 to 10 micrometers and a height of 10 to 150 micrometers.

[0050] The concave focusing and sensitizing film has a thickness of 2–8 micrometers, a diameter of 10–60 micrometers, a radius of curvature of 10–150 micrometers, and a thickness of 3–5 micrometers.

[0051] The cross-shaped cantilever beam has a width of 3–30 micrometers, a length of 32–57 micrometers, and a thickness of 2–8 micrometers; the array element SEM image of the array-type fiber optic ultrasonic probe based on the cross-shaped cantilever beam plano-concave cavity provided by this invention is as follows: Figure 3 As shown.

[0052] The above structural parameters can be adjusted according to the required frequency band of the ultrasonic signal.

[0053] like Figure 4As shown, the array-type fiber optic ultrasonic probe based on a cross-beam flat-concave cavity consists of cross-beam flat-concave cavity array elements 3-7 and a sleeve 3-8. On the already bundled fiber array, a cross-beam flat-concave cavity structure is fabricated corresponding to the end face of each fiber element.

[0054] Furthermore, this invention also proposes a sensing method for an array-type fiber optic ultrasonic probe based on a cross-shaped cantilevered flat-concave cavity, comprising the following steps:

[0055] The probe light is coupled through optical fiber 3-1, first entering the first reflective film 3-4, then passing through the hollow environmental medium cavity formed by the supporting cavity 3-2, and then entering the concave focusing and sensitizing film 3-3, finally being reflected by the second reflective film 3-5. After the reflected light and the probe light interfere with each other in the cross-shaped cantilever beam 3-6 and the flat concave cavity structure, they return along the original path through optical fiber 3-1. When external ultrasound is incident, the ultrasound acts on the concave focusing and sensitizing film 3-3. Under the support of the cross-shaped cantilever beam 3-6, the concave focusing and sensitizing film 3-3 undergoes a flexural displacement. The change in displacement changes the optical path of the reflected light from the second reflective film 3-5, that is, changes the cavity length of the Fabry-Perot cavity, which in turn causes a change in the interference light intensity of the Fabry-Perot resonator. The reflected light then propagates backward through optical fiber 3-1 and is finally received by the photodetector. The magnitude of the ultrasound signal is obtained by demodulating the intensity of the reflected light.

[0056] Furthermore, this invention also proposes a method for preparing the above-mentioned array-type ultrasonic probe based on a cross-shaped cantilever planar concave cavity, the specific steps of which include:

[0057] S1. Based on the required number and arrangement shape of the fiber bundle array elements, such as rectangular parallel arrangement, hexagonal staggered arrangement, or one-dimensional linear arrangement, arrange and fix multiple optical fibers, and cut them into corresponding fiber segments.

[0058] S2. Using fiber bundle or fiber array fabrication processes, the individual fiber units are softened and bonded together to form an integral fiber bundle. Finally, the fiber bundle is encapsulated with a sleeve to protect the fiber bundle and provide a connection interface.

[0059] S3. After the optical fibers are bundled together, the output end face is polished flat; an ultrasonic cleaner is used to clean the end face to remove particles and oil stains from the output end face surface.

[0060] S4. Multilayer silicon dioxide and titanium dioxide are sequentially and alternately deposited onto the end face of the optical fiber bundle using magnetron sputtering to form a dielectric film with optical selective transmission properties.

[0061] S5. Fix the fiber bundle on the printing platform, use two-photon polymerization 3D printing technology to align each fiber unit of the fiber bundle, and process a cross-shaped plano-concave structure on the surface of the dielectric film.

[0062] S6. On the outside of the cross-shaped concave structure, a second reflective medium mirror is prepared by magnetron sputtering, using the same materials as S2, silicon dioxide and titanium dioxide, which are alternately deposited on the outside of the structure.

[0063] To further explain, the wavelength-selective transmission film is a dielectric film composed of alternating depositions of silicon dioxide and titanium dioxide. It utilizes the optical interference between materials with different refractive indices to reflect some wavelengths of incident light while projecting others. By designing the structural parameters of the dielectric film, when excitation light and signal light enter the optical fiber, the excitation light penetrates the dielectric film, and the signal light is reflected, thereby generating a beam of reverse-transmitted optical signal.

[0064] Figure 5 The imaging system of the array-type fiber optic ultrasonic probe based on the cross-beam flat-concave cavity in this invention includes a laser 1, a 1×N fiber optic coupler 2, an array-type ultrasonic probe based on the cross-beam flat-concave cavity 3, an N-channel circulator 4, a photodetector array 5, a data acquisition module 6, and a terminal controller 7.

[0065] To further explain, the laser 1 is connected to the 1×N fiber coupler 2, the array-type fiber ultrasonic probe 3 is connected to the splitting port of the 1×N fiber coupler 2 through the N-way fiber circulator 4, the output end of the N-way fiber circulator 4 is connected to the photodetector array 5, the photodetector array 5 is connected to the data acquisition module 6, and the terminal controller 7 is connected to the laser 1, the photodetector array 5, and the data acquisition module 6 respectively.

[0066] Specifically, the laser 1 generates probe light with a wavelength consistent with the operating wavelength of the array-type fiber optic ultrasonic probe 3. The probe light emitted by the laser 1 is coupled into the incident end a of the N-way fiber optic circulator 4 by the 1×N fiber coupler 2, and injected into the array-type fiber optic ultrasonic probe 3 from the b end of the N-way fiber optic circulator 4. The probe light interferes with the sensing structure in the array-type fiber optic ultrasonic probe 3 and is modulated by an external ultrasonic signal. The modulated probe light signal, carrying ultrasonic information, is reflected from the array-type fiber optic ultrasonic probe 3, re-enters through the b end of the N-way fiber optic circulator 4, and exits from the c end of the N-way fiber optic circulator 4. The exited light signal is received by the photodetector array 5. The photodetector array 5 converts the light signal into a piezoelectric signal, which is received by the data acquisition module 6 and transmitted to the terminal controller 7. The terminal controller 7 is simultaneously connected to the photodetector array 5 and an external trigger source, such as an excitation laser trigger. Under the control of the trigger signal, the photodetector array 5 synchronously acquires the ultrasonic signal.

[0067] Furthermore, the present invention also proposes an imaging method, comprising the following steps:

[0068] The probe light emitted by laser 1 is coupled into the incident end a of the N-way fiber optic circulator 4 through the 1×N fiber coupler 2, and injected into the array-type fiber optic ultrasonic probe 3 from the b end of the N-way fiber optic circulator 4. The probe light interferes in the sensing structure of the array-type fiber optic ultrasonic probe 3 and is modulated by the external ultrasonic signal. The modulated probe light carries ultrasonic information and is reflected from the array-type fiber optic ultrasonic probe 3, enters again through the b end of the N-way fiber optic circulator 4, and exits from the c end of the N-way fiber optic circulator 4. The outgoing light signal is received by the photodetector array 5. The photodetector array 5 converts the light signal into a piezoelectric signal, which is received by the data acquisition module 6 and transmitted to the terminal controller 7 for ultrasonic signal filtering, noise reduction, and enhancement processing. The processed signal is used to reconstruct three-dimensional or two-dimensional image information for imaging. The terminal controller 7 is also connected to the photodetector array 5 and an external trigger source. The photodetector array 5 synchronously acquires ultrasonic signals under the control of the trigger signal.

[0069] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An array-type fiber optic ultrasonic probe based on a cross-shaped cantilevered flat-concave cavity, characterized in that, The system comprises N cross-beam concave-cross cavity elements, where N is a positive integer. Each cross-beam concave-cross cavity element includes an optical fiber (3-1), a supporting cavity (3-2), a concave focusing and sensitizing diaphragm (3-3), a first reflective film (3-4), a second reflective film (3-5), and a cross-beam (3-6). The lower surface of the supporting cavity (3-2) is connected to the end face of the optical fiber (3-1) through the first reflective film (3-4). The upper surface of the supporting cavity (3-2) supports the concave focusing and sensitizing diaphragm (3-3). The concave focusing and sensitizing diaphragm is connected to the edge of the upper surface of the supporting cavity (3-2) through the cross-beam (3-6). The upper surface of the concave focusing and sensitizing diaphragm (3-3) is covered with the second reflective film (3-5). The concave focusing and sensitizing diaphragm (3-3) undergoes flexural displacement under the action of ultrasound, and the flexural displacement causes a change in the cavity length of the Fabry-Perot resonator. The supporting cavity (3-2) is cylindrical and filled with liquid or gas; The supporting cavity (3-2), the concave focusing and sensitizing diaphragm (3-3), the first reflective film (3-4), the second reflective film (3-5), and the cross-shaped cantilever beam (3-6) constitute a cross-shaped cantilever Fabry-Perot resonant cavity; The supporting cavity (3-2), the concave focusing and sensitizing film (3-3), and the cross-shaped cantilever beam (3-6) are all two-photon polymerization 3D printed structures.

2. A sensing method for an array-type fiber optic ultrasonic probe based on a cross-shaped cantilevered flat-concave cavity as described in claim 1, characterized in that, Includes the following steps: The probe light is coupled through an optical fiber (3-1), first entering the first reflective film (3-4), then passing through the hollow ambient medium cavity formed by the supporting cavity (3-2), and then entering the concave focusing and sensitizing film (3-3), finally being reflected by the second reflective film (3-5). The second reflective film (3-5) is attached to the upper surface of the concave focusing and sensitizing film to form a concave mirror. The first reflective film (3-4) and the second reflective film (3-5) form a plano-concave Fabry-Perot resonator. The probe light interferes within the plano-concave cavity structure between the first reflective film (3-4) and the second reflective film (3-5). The light returns via the original path through optical fiber (3-1). When external ultrasound is incident, the ultrasound acts on the concave focusing and sensitizing diaphragm (3-3). Under the support of the cross-shaped cantilever beam (3-6), the concave focusing and sensitizing diaphragm (3-3) undergoes flexural displacement. The change in displacement alters the optical path of the reflected light from the second reflective film (3-5), which in turn changes the cavity length of the Fabry-Perot cavity, leading to a change in the interference light intensity of the Fabry-Perot resonator. The reflected light then propagates backward through optical fiber (3-1) and is finally received by the photodetector. The magnitude of the ultrasound signal is obtained by demodulating the intensity of the reflected light.

3. A method for fabricating an array-type fiber optic ultrasonic probe based on a cross-shaped cantilever flat-concave cavity as described in claim 1, characterized in that, Includes the following steps: S1. Arrange and fix multiple optical fibers according to the number and arrangement of array elements, and cut them into corresponding optical fiber segments; S2. Using fiber bundle or fiber array fabrication process, the individual fiber units are softened and bonded together to form an integral fiber bundle. Finally, the fiber bundle is encapsulated with a sleeve to protect the fiber bundle and provide a connection interface. S3. After the optical fibers are bundled together, the output end face is polished flat; the end face is then cleaned. S4. Multilayer silicon dioxide and titanium dioxide are sequentially and alternately deposited onto the end face of the optical fiber bundle using magnetron sputtering to form a dielectric film with optical selective transmission properties; S5. Fix the fiber bundle on the printing platform, use two-photon polymerization 3D printing technology to align each fiber unit of the fiber bundle to manufacture a cross-beam flat-concave cavity array element, and process the cross-beam flat-concave structure on the surface of the first reflective film in the order of support cavity (3-2), cross-beam (3-6), and concave focusing and sensitizing film (3-3). S6. On the outside of the cross-shaped cantilever flat-concave structure, a second reflective film is prepared by magnetron sputtering, using the same materials as S2, silicon dioxide and titanium dioxide, which are alternately deposited on the outside of the structure.

4. An imaging system, characterized in that, The system includes a laser (1), a 1×N fiber coupler (2), an array-type fiber ultrasonic probe (3) based on a cross-beam concave cavity as described in claim 1, an N-way fiber circulator (4), a photodetector array (5), a data acquisition module (6), and a terminal controller (7). The output end of the laser (1) is connected to the input end of the 1×N fiber coupler (2). The array-type fiber ultrasonic probe (3) is connected to the splitting port of the 1×N fiber coupler (2) through the N-way fiber circulator (4). The output end of the N-way fiber circulator (4) is connected to the photodetector array (5). The photodetector array (5) is connected to the data acquisition module (6). The terminal controller (7) is connected to the laser (1), the photodetector array (5), and the data acquisition module (6) respectively. After receiving the signal, the data acquisition module (6) transmits it to the terminal controller (7) to perform ultrasonic signal filtering, noise reduction and enhancement processing, reconstruct three-dimensional or two-dimensional image information from the processed signal and display it on the screen.

5. The imaging system according to claim 4, characterized in that, The terminal controller (7) includes an image processing module and a timing control module; the trigger source of the terminal controller (7) is connected to the photodetector array (5), the photodetector array (5) is connected to the data acquisition module (6), the photodetector array (5) converts the received optical ultrasonic signal into an electrical signal under the control of the trigger signal of the terminal controller (7), and transmits the real-time electrical ultrasonic signal data to the data acquisition module (6), the data acquisition module (6) collects and stores the data, and transmits the ultrasonic signal data to the terminal controller (7).

6. An imaging method based on the imaging system of claim 4 or 5, characterized in that, Includes the following steps: The probe light emitted by the laser (1) is coupled into the incident a end of the N-way fiber circulator (4) through the 1×N fiber coupler (2), and injected into the array-type fiber ultrasonic probe (3) from the b end of the N-way fiber circulator (4); the probe light interferes in the sensing structure of the array-type fiber ultrasonic probe (3) and is modulated by the external ultrasonic signal. The modulated probe light carries the ultrasonic information and is reflected from the array-type fiber ultrasonic probe (3), enters again through the b end of the N-way fiber circulator (4), and exits from the N-way fiber circulator. (4) The light signal is emitted from the c end and received by the photodetector array (5). The photodetector array (5) converts the light signal into an electrical signal, which is received by the data acquisition module (6) and transmitted to the terminal controller (7). The terminal controller (7) performs ultrasonic signal filtering, noise reduction and enhancement processing, and reconstructs three-dimensional or two-dimensional image information from the processed signal for imaging. The terminal controller (7) is simultaneously connected to the photodetector array (5) and an external trigger source. The photodetector array (5) synchronously acquires ultrasonic signals under the control of the trigger signal.

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