System and method for all-optical-fiber-based ultrasonic detection

Abstract

The present invention relates to the field of photoacoustic detection technology, and in particular, to a system and method for all-optical-fiber-based ultrasonic detection. The system comprises: a photo-induced ultrasonic emission module, an optical ultrasonic sensing module, and an all-optical ultrasonic probe (3); the photo-induced ultrasonic emission module comprises a pulse laser (1) and a first optical fiber (2); the optical ultrasonic sensing module comprises a second optical fiber (5), a third optical fiber (6), a fourth optical fiber (7), a circulator and an isolator (8), a photoelectric detector (9), a tunable laser (10), an acquisition card (11), and a computer (12); the all-optical ultrasonic probe (3) comprises an optical fiber ultrasonic emission set (3-1) and an optical ultrasonic sensing set (3-2). The present invention features improved probe design, optimized manufacturing process and system structure, improved repeatability of manufacturing and consistency of performance, improved contrast and resolution of imaging, and reduced noise interference.

Description

An all-fiber-based ultrasonic testing system and method Technical Field

[0001] This invention relates to the field of photoacoustic detection technology, and in particular to an all-fiber ultrasonic detection system and method. Background Technology

[0002] In the field of modern medical imaging technology, photoacoustic imaging technology, as an innovative technology paradigm combining endoscopic acoustics and optics, provides a unique perspective and method for disease diagnosis. By irradiating tissue with short-pulse lasers, the irradiated area generates ultrasound signals due to thermoelastic expansion. The sound wave signals can be detected by ultrasound sensors and tissue images can be reconstructed. This technology can enable accurate diagnosis and timely intervention of vulnerable plaques in blood vessels at an early stage.

[0003] Both photoacoustic imaging and ultrasound imaging technologies essentially involve the detection of ultrasound waves, specifically the detection of echoes generated after ultrasound interacts with tissue and the imaging of ultrasound waves generated after light waves interact with tissue. Therefore, ultrasound detection technology is a crucial component in ensuring image quality. Based on the ultrasound detection mechanism, currently widely used ultrasound detection schemes can be categorized into piezoelectric transducers, micromechanical transducers, and the emerging all-optical ultrasound detection technology. Among these, all-optical ultrasound detection technology shows promise as the next generation of ultrasound detection technology due to its advantages such as small size, high imaging contrast, simple sensor array structure, minimal wiring, and immunity to electromagnetic interference. An all-optical ultrasound detection system typically consists of a photoacoustic transmitter made of fiber optic devices and an optical ultrasound sensor. The photoacoustic transmitter can provide sound pressure levels comparable to or even higher than those of piezoelectric transducers, as well as a wider bandwidth. Compared to piezoelectric elements of the same size, the optical ultrasound sensor offers higher sensitivity and a higher frequency response. Furthermore, thanks to the light-guiding and electromagnetic interference-resistant properties of optical fibers, all-optical ultrasound detection devices are easily integrated with photoacoustic imaging systems and even magnetic resonance imaging systems, making them suitable for complex clinical applications.

[0004] Despite the significant potential of all-optical ultrasound detection technology, its practical application in scenarios such as vascular disease detection still faces a series of serious challenges. From the perspective of probe design and manufacturing processes, traditional all-optical ultrasound probes have several shortcomings. First, their manufacturing process is complex and lacks standardized procedures, resulting in significant performance differences between different batches of probes, making repeatability and consistency difficult to guarantee. For example, when detecting minute lesions within blood vessels, these performance differences may lead to misjudgment or missed detection of lesion features, severely affecting diagnostic accuracy. Second, the structural design of traditional all-optical ultrasound probes is not optimized enough, resulting in relatively low imaging contrast and resolution, making it difficult to clearly distinguish different layers of the vascular wall and the detailed features of minute lesions, such as the lipid core and fibrous cap in vascular plaques. In addition, noise interference is a prominent problem in traditional all-optical ultrasound detection systems. External environmental noise as well as internal optical and electrical noise can easily mix into the ultrasound signal, reducing the signal-to-noise ratio and further deteriorating image quality, causing great difficulties for clinical diagnosis.

[0005] Therefore, proposing an all-fiber-based ultrasonic testing system and method to overcome the difficulties of existing technologies is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides an all-fiber ultrasonic testing system and method. By using optical fibers, the present invention improves probe design, optimizes manufacturing process and system structure, improves repeatability and performance consistency, enhances imaging contrast and resolution, and reduces noise interference.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An all-fiber-based ultrasonic testing system includes: a photo-induced ultrasonic emission module, an optical ultrasonic sensing module, and an all-optical ultrasonic probe;

[0009] The photo-induced ultrasonic emission module includes: a pulsed laser and a first optical fiber;

[0010] The optical ultrasonic sensing module includes: a second optical fiber, a third optical fiber, a fourth optical fiber, a circulator and isolator, a photodetector, a tunable laser, a data acquisition card, and a computer.

[0011] The all-optical ultrasonic probe consists of: a fiber optic ultrasonic transmitter group and an optical ultrasonic sensor group;

[0012] The pulsed laser in the photo-induced ultrasonic emission module is connected to the fiber optic ultrasonic emission group of the all-optical ultrasonic probe via the first optical fiber.

[0013] The tunable laser in the optical ultrasonic sensing module is connected to the circulator and isolator via the third optical fiber. The acquisition card is connected to the circulator and isolator via the fourth optical fiber and a photodetector. The computer is connected to the acquisition card via the fourth optical fiber. The circulator and isolator are connected to the optical ultrasonic sensing group of the all-optical ultrasonic probe via the second optical fiber.

[0014] Optionally, in the above system, a pulsed laser provides a pulsed light source for the fiber optic ultrasonic emission module in the photo-induced ultrasonic emission module;

[0015] The fiber optic ultrasonic transmitter consists of four identical photo-induced ultrasonic transmitters;

[0016] The first optical fiber is a multimode optical fiber, and the optical fiber ultrasonic transmission group is based on multimode optical fiber to construct a composite film layer.

[0017] The composite film layer includes: polydimethylsiloxane, multi-walled carbon nanotubes and molybdenum disulfide material, or polydimethylsiloxane, multi-walled carbon nanotubes and graphene material;

[0018] Polydimethylsiloxane is a thermoelastic expansion layer;

[0019] The light-absorbing coating in the photo-induced ultrasound composite film includes: light-absorbing particles, thermally conductive materials, and polydimethylsiloxane. The light-absorbing particles and thermally conductive materials exist in a mixed state. Multi-walled carbon nanotubes or graphene are used as light-absorbing particles, and molybdenum disulfide or graphene are used as thermally conductive materials.

[0020] In the above system, optionally, a pulsed laser emits a pulsed laser, which acts on the light-absorbing coating through a first optical fiber. Under the excitation of the incident pulsed light, the light-absorbing coating converts light energy into heat energy, which is rapidly transferred to the thermoelastic expansion layer. The thermoelastic expansion layer expands due to heat. When there is no light, the thermoelastic expansion layer begins to contract after the heat energy is no longer applied, converting the heat energy into ultrasonic mechanical energy.

[0021] In the above system, optionally, in the optical ultrasonic sensing module, a tunable laser is used as the detection light source of the optical ultrasonic sensing group, a data acquisition card is used to acquire ultrasonic echo signals, a computer is used for real-time three-dimensional imaging, a photodetector converts the optical signal into an electrical signal, and a circulator and isolator are set at the front end of the photodetector and the tunable laser.

[0022] The second, third, and fourth optical fibers are all single-mode optical fibers;

[0023] The optical ultrasonic sensing unit consists of a Fabry-Perot (FP) sensor and a fiber Bragg grating (FBG) sensor.

[0024] FP sensors consist of single-mode fiber, hollow fiber, and a vibration-sensitive membrane; FBG sensors consist of single-mode fiber and fiber gratings.

[0025] In the optical FP sensor, the end faces of the second optical fiber and the hollow optical fiber serve as the first reflecting surface, the vibration-sensitive film serves as the second reflecting surface, and the hollow optical fiber serves as the light wave transmission path.

[0026] In the above system, optionally, a tunable laser emits a light source, which passes through a third fiber, a circulator and isolator, and a second fiber. In the optical FP sensor, the second fiber and the hollow fiber end face undergo a first reflection. The transmitted light is transmitted in the hollow fiber to the vibration-sensitive membrane, undergoes a second reflection, and is transmitted through the hollow fiber again and coupled back to the second fiber, interfering with the first reflected light. When the front ultrasonic wave acts on the vibration-sensitive membrane of the optical FP sensor, the vibration-sensitive membrane in the non-fixed area will deform, and the sensor cavity length will also change accordingly, thereby modulating the interference spectrum.

[0027] When a side ultrasonic wave is applied to the FBG sensor, the mechanical vibration induced by the ultrasonic wave causes strain in the single-mode fiber where the FBG sensor is located, resulting in changes in the period and effective refractive index of the fiber grating, and a corresponding change in the wavelength of the reflected light.

[0028] The system accurately collects and processes information on the wavelength changes of reflected light received by multiple FBG sensors at different locations, and uses a specific imaging algorithm to reconstruct an optical image that reflects changes in the internal structure or properties of the detected object.

[0029] An all-fiber-based ultrasonic testing method, comprising:

[0030] S1, The pulsed laser emits laser pulses;

[0031] S2. The fiber optic ultrasonic transmitter generates ultrasonic waves under the action of pulsed laser.

[0032] S3. Ultrasonic waves act on the sample to be tested, and the sample to be tested emits part of the ultrasonic waves.

[0033] S4. The emitted ultrasonic wave is received by the optical ultrasonic sensor group, and at the same time, the tunable laser emits a probe laser that acts on the optical ultrasonic sensor group for reception.

[0034] By changing the cavity length of S5 and FP, the period of the fiber grating, and the effective refractive index, the interference spectrum can be modulated.

[0035] S6. The tunable laser emits a probe laser, and the reflected interference light is used by a photodetector and a data acquisition card to obtain an ultrasonic echo signal.

[0036] S7. The ultrasonic echo signal is analyzed and processed by computer to perform three-dimensional imaging.

[0037] As can be seen from the above technical solution, compared with the prior art, the present invention provides an all-fiber-based ultrasound detection system and method, which has the following beneficial effects: 1) The all-optical ultrasound probe manufactured by the present invention is divided into a photo-induced ultrasound emission group and an optical ultrasound sensing group. The diameter of the all-optical ultrasound probe is less than 1.5mm, which is small in size. The improved probe design realizes the integration of transmission and reception, which is suitable for the detection of vascular diseases; 2) The photo-induced ultrasound emission group consists of four photo-induced ultrasound emission probes. When the ultrasound waves are excited, the photo-induced ultrasound emission group can realize the superposition of the emitted ultrasound waves, which can improve the image contrast and make the difference in acoustic impedance between the target object and the surrounding tissue more obvious, which is beneficial to the imaging of vascular plaques; 3) It can enhance the signal strength and resolution, and accurately capture details such as the boundary and internal echo of thyroid nodules; 4) It can reduce noise interference, thereby making the image clearer, reducing blur and artifacts, and helping to make more accurate ultrasound diagnosis; 5) The system structure and manufacturing process are optimized, the manufacturing process is simple, and the repeatability and performance consistency of the subsequent device manufacturing are improved. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1 is a schematic diagram of an all-fiber ultrasonic testing system provided by the present invention;

[0040] Figure 2 is a schematic diagram of the working principle of an all-fiber ultrasonic testing system provided by the present invention;

[0041] Figure 3 is a flowchart of an all-fiber ultrasonic testing method provided by the present invention;

[0042] Explanation of reference numerals in the attached figures:

[0043] 1 is a pulsed laser; 2 is the first optical fiber; 3 is an all-optical ultrasonic probe; 3-1 is an optical fiber ultrasonic transmitter group; 3-2 is an optical ultrasonic sensor group; 4 is the sample to be tested; 5 is the second optical fiber; 6 is the third optical fiber; 7 is the fourth optical fiber; 8 is a circulator and isolator; 9 is a photodetector; 10 is a tunable laser; 11 is a data acquisition card; 12 is a computer; 13 is a light-absorbing coating; 14 is a thermoelastic expansion layer; 15 is the first reflective surface; 16 is a hollow optical fiber; 17 is a vibration-sensitive film; 18 is a fiber grating. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0046] Referring to FIG1, the present invention discloses an all-fiber ultrasonic detection system, comprising: a photo-induced ultrasonic emission module, an optical ultrasonic sensing module, and an all-optical ultrasonic probe 3;

[0047] The photo-induced ultrasonic emission module includes: a pulsed laser 1 and a first optical fiber 2;

[0048] The optical ultrasonic sensing module includes: a second optical fiber 5, a third optical fiber 6, a fourth optical fiber 7, a circulator and isolator 8, a photodetector 9, a tunable laser 10, a data acquisition card 11, and a computer 12.

[0049] The all-optical ultrasonic probe 3 includes: fiber optic ultrasonic transmitter group 3-1 and optical ultrasonic sensor group 3-2;

[0050] The pulsed laser 1 in the photo-induced ultrasonic emission module is connected to the fiber ultrasonic emission group 3-1 of the all-optical ultrasonic probe 3 via the first optical fiber 2.

[0051] The tunable laser 10 in the optical ultrasonic sensing module is connected to the circulator and isolator 8 via the third optical fiber 6. The acquisition card 11 is connected to the circulator and isolator 8 via the fourth optical fiber 7 and the photodetector 9. The computer 12 is connected to the acquisition card 11 via the fourth optical fiber 7. The circulator and isolator 8 is connected to the optical ultrasonic sensing group 3-2 of the all-optical ultrasonic probe 3 via the second optical fiber 5.

[0052] Furthermore, in the photo-induced ultrasonic emission module, the pulsed laser 1 provides a pulsed light source for the fiber ultrasonic emission group 3-1. The excitation frequency range of the pulsed laser is 400nm-1100nm, the current range is 50mA-600mA, the pulse width range is 5ns-50ns, and the repetition frequency range is 10Hz-1MHz.

[0053] The fiber optic ultrasonic transmitter group 3-1 consists of four identical photo-induced ultrasonic transmitters;

[0054] The first optical fiber 2 is a multimode optical fiber. The optical fiber ultrasonic emission group 3-1 uses the multimode optical fiber as a substrate to construct a composite film layer with a thickness of 15um-25um.

[0055] The composite film layer includes: polydimethylsiloxane, multi-walled carbon nanotubes and molybdenum disulfide (ratio of multi-walled carbon nanotubes to molybdenum disulfide: 1~1.5:1) material, or polydimethylsiloxane, multi-walled carbon nanotubes and graphene material (ratio of multi-walled carbon nanotubes to graphene material: 1:1~2).

[0056] Polydimethylsiloxane is the matrix material of the photo-induced ultrasonic composite film, which is the thermoelastic expansion layer 14;

[0057] The light-absorbing coating 13 in the photo-induced ultrasound composite film includes: light-absorbing particles, thermally conductive material and polydimethylsiloxane. The light-absorbing particles and thermally conductive material exist in a mixed state. Multi-walled carbon nanotubes or graphene are light-absorbing particles, and molybdenum disulfide or graphene are thermally conductive materials. The thickness of the light-absorbing coating 13 is 8 μm to 10 μm.

[0058] Furthermore, the combination of multi-walled carbon nanotubes and graphene allows graphene to improve the efficiency of photothermal conversion and also to conduct heat. The combination of the two can, on the one hand, increase the area and pathway of light absorption, broaden the absorption spectrum range through complementary effects, and absorb more photon energy; on the other hand, they can construct efficient heat conduction channels, convert the absorbed light energy into heat energy more quickly and transfer it effectively, reduce heat loss, and thus improve the overall efficiency of photothermal conversion.

[0059] Furthermore, the polydimethylsiloxane (PDMS) content in the light-absorbing coating 13 is less than 10%. The role of PDMS is to encapsulate the light-absorbing particles and thermally conductive materials, and to firmly coat the light-absorbing coating 13 onto the fiber end face. When the PDMS content is less than 10%, on the one hand, the PDMS material has high transparency and the small proportion will not affect the transmission of pulsed laser. On the other hand, the light-absorbing particles and thermally conductive materials play a role similar to crossbeam supports inside the light-absorbing coating 13. They work together with an appropriate amount of PDMS to build a stable and reasonable coating structure. At the same time, the small PDMS content can significantly reduce the deformation ability of the light-absorbing layer due to heat, which is of positive significance for maintaining the performance stability of the light-absorbing coating under different working conditions.

[0060] Specifically, both the light-absorbing coating 13 and the thermoelastic expansion layer 14 contain PDMS. To achieve precise and effective coating operations, this invention utilizes screen printing. A 20-50 mesh screen is selected, and a mixture of a certain proportion of the light-absorbing layer (polydimethylsiloxane and multi-walled carbon nanotubes & graphene, or polydimethylsiloxane and multi-walled carbon nanotubes & molybdenum disulfide, with polydimethylsiloxane (PDMS) accounting for less than 10%) is poured onto the screen. Excess material is removed using a scraper, leaving the mixture within the screen mesh. The mixture is then allowed to stand at 60-80°C for 3-5 minutes. A three-dimensional adjustment frame is then used to pass an optical fiber through the mesh, transferring the mixture to the fiber end face. This allows control over the thickness of the light-absorbing coating 13. The thermoelastic expansion layer 14 (polydimethylsiloxane) is also fabricated using this method. This coating method and associated control measures not only improve the repeatability of the coating fabrication process but also ensure the consistency of the transmitter's performance across different batches. This significantly contributes to improving the overall reliability of the device and promoting standardized production.

[0061] Furthermore, referring to Figure 2, the pulsed laser 1 emits a pulsed laser, which acts on the light-absorbing coating 13 through the first optical fiber 2. Under the excitation of the incident pulsed light, the light-absorbing coating 13 converts light energy into heat energy and rapidly transfers it to the thermoelastic expansion layer 14. The thermoelastic expansion layer 14 expands due to heat. When there is no light, the thermoelastic expansion layer 14 begins to contract after the heat energy is no longer applied, converting the heat energy into ultrasonic mechanical energy.

[0062] Furthermore, in the optical ultrasonic sensing module, the tunable laser 10 is the detection light source of the optical ultrasonic sensing group 3-2, the acquisition card 11 is used to display the ultrasonic echo signal, the photodetector 9 converts the optical signal into an electrical signal, and a circulator and isolator 8 are provided at the front end of the photodetector 9 and the tunable laser 10.

[0063] The second fiber 5, the third fiber 6, and the fourth fiber 7 are all single-mode fibers;

[0064] The optical ultrasonic sensing group 3-2 consists of a Fabry-Perot FP sensor and a fiber optic grating 18FBG sensor. The FP and FBG sensors are arranged alternately, with a total of 8 sensors. The FP sensor detects the ultrasonic waves from the front, while the FBG sensor receives the ultrasonic waves from the side. Thus, real-time three-dimensional imaging can be performed by simply giving the probe a certain forward step.

[0065] The FP sensor consists of a single-mode fiber, a hollow fiber 16, and a vibration-sensitive membrane 17; the FBG sensor consists of a single-mode fiber and a fiber grating 18.

[0066] In the optical FP sensor, the end faces of the second optical fiber 5 and the hollow optical fiber 16 serve as the first reflecting surface 14, the vibration-sensitive film 17 serves as the second reflecting surface, and the hollow optical fiber 16 serves as the light wave transmission path.

[0067] Hollow-core fiber 16 forms an FP cavity with a cavity length of 40um-80um, which has a light guiding function;

[0068] The vibration-sensitive membrane 17 is made of polydimethylsiloxane (PDMS) material with a membrane thickness of 10 μm-15 μm; the vibration-sensitive membrane 17 can also be a gold and silver membrane, a polytetrafluoroethylene (PTFE) membrane, and the polydimethylsiloxane (PDMS) membrane has the best effect.

[0069] The end face of a single-mode fiber and a hollow fiber 16 is constructed using fiber optic fusion splicing technology. The vibration-sensitive membrane 17 is fixed to the end face of the hollow fiber 16 by fusion splicing or bonding. The sensor constructed by the single-mode fiber, hollow fiber 16 and vibration-sensitive membrane 17 is encapsulated with a flat-headed needle tube, so that the sensor has a high spectral extinction ratio.

[0070] To further improve the mechanical strength of the optical ultrasonic sensor assembly 3-2, and considering the application environment of the sensor, this invention uses a flat-headed needle tube with an inner diameter of 0.5 mm to encapsulate the sensors of the two types of diaphragms.

[0071] In the optical ultrasonic sensing group 3-2, the end faces of the second optical fiber 5 and the hollow optical fiber 16 serve as the first reflecting surface 15, the vibration-sensitive film 17 serves as the second reflecting surface, and the hollow optical fiber 16 serves as the light wave transmission path.

[0072] Furthermore, referring to Figure 2, the tunable laser 10 emits a light source, which passes through the third optical fiber 6, the circulator and isolator 8, and the second optical fiber 5. In the optical FP sensor, the second optical fiber 5 and the end face of the hollow optical fiber 16 undergo a first reflection. The transmitted light is transmitted in the hollow optical fiber 16 to the vibration-sensitive membrane 17, undergoes a second reflection, and is transmitted through the hollow optical fiber 16 and coupled back to the second optical fiber 5, interfering with the first reflected light. When the front ultrasonic wave acts on the vibration-sensitive membrane 17 of the optical FP sensor, the vibration-sensitive membrane 17 in the non-fixed area will deform, and the sensor cavity length will also change accordingly, thereby achieving modulation of the interference spectrum.

[0073] When the side ultrasonic wave is applied to the FBG sensor, the mechanical vibration caused by the ultrasonic wave causes strain in the single-mode fiber where the FBG sensor is located, resulting in changes in the period and effective refractive index of the fiber grating 18, and a corresponding change in the wavelength of the reflected light.

[0074] The system accurately collects and processes information on the wavelength variation of reflected light received by multiple FBG sensors at different locations, and uses a specific imaging algorithm to reconstruct an optical image that reflects the changes in the internal structure or properties of the detected object.

[0075] Referring to Figure 3, an all-fiber ultrasonic testing method includes:

[0076] S1, Pulse laser 1 emits laser pulses;

[0077] S2, Fiber optic ultrasonic transmitter group 3-1 generates ultrasonic waves under the action of pulsed laser;

[0078] S3. Ultrasonic waves are applied to the sample 4 to be tested, and the sample 4 to be tested emits part of the ultrasonic waves.

[0079] S4. The divergent ultrasonic wave is received by the optical ultrasonic sensor group 3-2, and at the same time, the tunable laser 10 emits a probe laser that acts on the optical ultrasonic sensor group 3-2 for reception.

[0080] By changing the cavity length of S5 and FP, the period of fiber grating 18, and the effective refractive index, the interference spectrum can be modulated.

[0081] S6. The tunable laser 10 emits a probe laser, and the reflected interference light is used by the photodetector 9 and the acquisition card 11 to obtain the ultrasonic echo signal.

[0082] S7. The ultrasonic echo signal is analyzed and processed by computer 12 to perform three-dimensional imaging.

[0083] In one specific embodiment, a pulsed laser 1 emits a pulsed laser with a wavelength of 532 nm, a current range of 300 mA, a pulse width range of 5 ns, and a repetition frequency range of 10 Hz. An optical fiber ultrasonic transmitter group 3-1 generates ultrasonic waves under the influence of the pulsed laser, wherein the optical absorption coating 13 has a thickness of 8 μm and the composite film layer has a thickness of 15 μm. An all-optical ultrasonic probe is placed inside the sample, and the ultrasonic waves, after being superimposed, act on the sample 4 to be tested, reflecting ultrasonic waves from the sample and carrying sample information. Simultaneously, a tunable laser 10 emits a probe laser that acts on the optical ultrasonic sensing group. Since the ultrasonic waves carrying sample information are received by the optical ultrasonic sensing group, the reflected interference light is demodulated by a photodetector 9 and a data acquisition card 11. Finally, the computer 12 analyzes and processes the ultrasonic echo signal to perform three-dimensional imaging.

[0084] In another specific embodiment, a pulsed laser 1 emits a pulsed laser with a wavelength of 1064 nm, a current range of 300 mA, a pulse width range of 5 ns, and a repetition frequency range of 10 Hz. The fiber optic ultrasonic transmitter group 3-1 generates ultrasonic waves under the action of the pulsed laser, wherein the optical absorption coating 13 has a thickness of 8 μm and the composite film layer has a thickness of 15 μm. The all-optical ultrasonic probe is placed inside the sample, and the ultrasonic waves are superimposed and act on the sample 4 to be tested, reflecting ultrasonic waves from the sample and carrying sample information. At the same time, a tunable laser 10 emits a probe laser that acts on the optical ultrasonic sensing group. Since the optical ultrasonic sensing group carrying sample information receives the reflected interference light, the interference spectrum is demodulated by the photodetector 9 and the acquisition card 11. Finally, the computer 12 analyzes and processes the ultrasonic echo signal to perform three-dimensional imaging.

[0085] In another specific embodiment, a pulsed laser 1 emits a pulsed laser with a wavelength of 1064 nm, a current range of 400 mA, a pulse width range of 20 ns, and a repetition frequency range of 100 Hz. The fiber optic ultrasonic transmitter group 3-1 generates ultrasonic waves under the action of the pulsed laser, wherein the optical absorption coating 13 has a thickness of 10 μm and the composite film layer has a thickness of 15 μm. The all-optical ultrasonic probe is placed inside the sample, and the ultrasonic waves are superimposed and act on the sample 4 to be tested, reflecting ultrasonic waves from the sample and carrying sample information. At the same time, a tunable laser 10 emits a probe laser that acts on the optical ultrasonic sensing group. Since the ultrasonic waves carrying sample information are reflected by the optical ultrasonic sensing group, the interference light passes through the photodetector 9 and the acquisition card 11 to demodulate the interference spectrum. Finally, the computer 12 analyzes and processes the ultrasonic echo signal to perform three-dimensional imaging.

[0086] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0087] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An all-fiber based ultrasonic detection system, characterized by, include: Photo-induced ultrasonic emission module, optical ultrasonic sensing module, all-optical ultrasonic probe (3); The photo-induced ultrasonic emission module includes: a pulsed laser (1) and a first optical fiber (2); In the photo-induced ultrasonic emission module, a pulsed laser (1) provides a pulsed light source for the fiber optic ultrasonic emission group (3-1); The fiber optic ultrasonic transmitter group (3-1) consists of four identical photo-induced ultrasonic transmitters; The first optical fiber (2) is a multimode optical fiber, and the optical fiber ultrasonic transmission group (3-1) is based on multimode optical fiber to construct a composite film layer; The composite film layer includes: polydimethylsiloxane, multi-walled carbon nanotubes and molybdenum disulfide material, or polydimethylsiloxane, multi-walled carbon nanotubes and graphene material; Polydimethylsiloxane is a thermoelastic expansion layer (14); The light-absorbing coating (13) in the photo-induced ultrasonic composite film includes: light-absorbing particles, thermally conductive materials and polydimethylsiloxane. The light-absorbing particles and thermally conductive materials exist in a mixed state. Multi-walled carbon nanotubes or graphene are light-absorbing particles, and molybdenum disulfide or graphene are thermally conductive materials. The optical ultrasonic sensing module includes: a second optical fiber (5), a third optical fiber (6), a fourth optical fiber (7), a circulator and isolator (8), a photodetector (9), a tunable laser (10), a data acquisition card (11), and a computer (12). The all-optical ultrasonic probe (3) includes: an optical fiber ultrasonic transmitter group (3-1) and an optical ultrasonic sensor group (3-2); the optical ultrasonic sensor group (3-2) consists of a Fabry-Perot FP sensor and a fiber optic grating (18) FBG sensor; The pulsed laser (1) in the photo-induced ultrasonic emission module is connected to the fiber ultrasonic emission group (3-1) of the all-optical ultrasonic probe (3) through the first optical fiber (2); The tunable laser (10) in the optical ultrasonic sensing module is connected to the circulator and isolator (8) via the third optical fiber (6). The acquisition card (11) is connected to the circulator and isolator (8) via the fourth optical fiber (7) and the photodetector (9). The computer (12) is connected to the acquisition card (11) via the fourth optical fiber (7). The circulator and isolator (8) is connected to the optical ultrasonic sensing group (3-2) of the all-optical ultrasonic probe (3) via the second optical fiber (5).

2. The all-fiber-based ultrasonic testing system according to claim 1, characterized in that, The pulsed laser (1) emits a pulsed laser, which acts on the light-absorbing coating (13) through the first optical fiber (2). Under the excitation of the incident pulsed light, the light-absorbing coating (13) converts light energy into heat energy and quickly transfers it to the thermoelastic expansion layer (14). The thermoelastic expansion layer (14) expands due to heat. When there is no light, the thermoelastic expansion layer (14) begins to contract after the heat energy is no longer applied, converting the heat energy into ultrasonic mechanical energy.

3. The all-fiber-based ultrasonic testing system according to claim 1, characterized in that, In the optical ultrasonic sensing module, the tunable laser (10) is the detection light source of the optical ultrasonic sensing group (3-2), the acquisition card (11) is used to acquire ultrasonic echo signals, the computer (12) is used for real-time three-dimensional imaging, the photodetector (9) converts the optical signal into an electrical signal, and a circulator and isolator (8) are set at the front end of the photodetector (9) and the tunable laser (10). The second fiber (5), the third fiber (6), and the fourth fiber (7) are all single-mode fibers; The FP sensor is composed of a single-mode fiber, a hollow fiber (16), and a vibration-sensitive membrane (17); the FBG sensor is composed of a single-mode fiber and a fiber grating (18). In the optical FP sensor, the end faces of the second optical fiber (5) and the hollow optical fiber (16) serve as the first reflecting surface (14), the vibration-sensitive film (17) serves as the second reflecting surface, and the hollow optical fiber (16) serves as the light wave transmission path.

4. The all-fiber-based ultrasonic testing system according to claim 3, characterized in that, The tunable laser (10) emits a light source, which passes through the third fiber (6), circulator and isolator (8), and second fiber (5). In the optical FP sensor, the second fiber (5) and the end face of the hollow fiber (16) undergo a first reflection. The transmitted light is transmitted in the hollow fiber (16) to the vibration-sensitive membrane (17) and undergoes a second reflection. It is transmitted through the hollow fiber (16) and coupled back to the second fiber (5) again, interfering with the first reflected light. When the front ultrasonic wave acts on the vibration-sensitive membrane (17) of the optical FP sensor, the vibration-sensitive membrane (17) in the non-fixed area will deform, and the sensor cavity length will also change accordingly, thereby achieving modulation of the interference spectrum. When the side ultrasonic wave is applied to the FBG sensor, the mechanical vibration caused by the ultrasonic wave causes strain in the single-mode fiber where the FBG sensor is located, resulting in changes in the period and effective refractive index of the fiber grating (18), and the wavelength of the reflected light changes accordingly. The system accurately collects and processes information on the wavelength variation of reflected light received by multiple FBG sensors at different locations, and uses a specific imaging algorithm to reconstruct an optical image that reflects the changes in the internal structure or properties of the detected object.

5. An all-fiber-based ultrasonic testing method, applied to an all-fiber-based ultrasonic testing system according to any one of claims 1-4, comprising: S1, Pulsed laser (1) emits laser pulses; S2, Fiber optic ultrasonic transmitter group (3-1) generates ultrasonic waves under the action of pulsed laser; S3. Ultrasonic waves are applied to the sample to be tested (4), and the sample to be tested (4) emits part of the ultrasonic waves. S4. The divergent ultrasonic wave is received by the optical ultrasonic sensor group (3-2), and at the same time, the tunable laser (10) emits a probe laser that acts on the optical ultrasonic sensor group (3-2) for reception. By changing the cavity length of S5 and FP and the period and effective refractive index of the fiber grating (18), the interference spectrum can be modulated. S6. The tunable laser (10) emits a probe laser, and the reflected interference light is transmitted through the photodetector (9) and the acquisition card (11) to obtain the ultrasonic echo signal. S7, analyzing and processing the ultrasonic echo signals by the computer (12) to perform three-dimensional imaging.

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