Magnetic field driven fiber optic cantilever beam resonant forward-looking OCT scanning probe and its usage.

Abstract

This invention relates to a magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe and its application method, belonging to the field of optical coherence tomography imaging technology. The scanning probe includes a non-ferromagnetic outer sheath, an internal probe assembly, and an external magnetic field driving assembly. The invention generates an external alternating magnetic field in the probe area using the external magnetic field driving assembly, causing a miniature permanent magnet, elastically bonded and fixed within the non-ferromagnetic outer sheath, to oscillate slightly laterally, applying a periodic lateral force to the root region of the elastic support of the fiber optic cantilever beam. When the excitation frequency of the external alternating magnetic field equals the first-order natural resonant frequency of the fiber optic cantilever beam, resonance occurs, amplifying the lateral oscillation amplitude at its free end. This invention utilizes the resonant amplification of the fiber optic cantilever beam to achieve large-field-of-view controllable forward-looking scanning with low driving energy; it is driven by an external alternating magnetic field and has no internal electrical drive structure; it reduces axial torsional stress and improves long-term operational reliability; and its simple structure facilitates miniaturization.

Description

Technical Field

[0001] This invention belongs to the field of optical coherence tomography imaging technology, and relates to a specific magnetic field driven fiber cantilever beam resonant forward-looking OCT scanning probe and its usage method. It is applicable to medical endoscopy, industrial narrow space inspection and other application scenarios that require forward-looking two-dimensional scanning imaging. Background Technology

[0002] Optical coherence tomography (OCT) is a high-resolution, non-destructive imaging technique based on the principle of low-coherence interference. It is widely used in fields such as biological tissue inspection, medical endoscopic imaging, internal defect detection in materials, and industrial structural inspection. In the inspection of confined spaces such as blood vessels, cavities, pipes, and deep holes, the forward-looking OCT scanning probe can image the area in front along the probe axis, making it of significant application value.

[0003] Existing forward-looking OCT scanning probes typically require the integration of a driving structure within the probe itself to drive the light beam for two-dimensional scanning. For example, Chinese invention patent (application number 202010904529.1) provides an OCT scanning probe and its implementation method capable of simultaneously achieving 360° forward and lateral scanning. This method primarily utilizes a host unit to drive the rotation and extension / retraction of a metal guide wire inside the probe, thereby moving the internal lens assembly and coordinating with a reflective element to achieve forward scanning. Chinese invention patent (application number 202210915262.5) provides a MEMS-based dual-modal otology detector. This probe integrates a MEMS micromirror at its front end, using a control cable to power the micromirror. The forward-looking OCT scanning imaging is achieved through the large-angle deflection of the micromirror along two axes. While existing technologies improve scanning control accuracy, their core driving components (such as MEMS micromirrors and piezoelectric driving elements) and their power supply lines must be integrated within the limited internal space of the probe. In humid, liquid-filled, or conductive medical and industrial environments, the internal electrical structure is highly susceptible to serious safety hazards such as insulation failure and leakage breakdown. Furthermore, the stacking of microelectromechanical components significantly increases the assembly difficulty of the probe, limiting the potential for further miniaturization of the probe diameter. In addition, some driving methods (such as piezoelectric ceramic materials) exhibit nonlinear response or hysteresis effects when operating at high frequencies, which can easily lead to scanning trajectory distortion and thus affect imaging quality.

[0004] Therefore, it is necessary to provide a forward-looking OCT scanning probe solution that is simpler in structure, more secure, and has the potential for miniaturization. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe. This invention generates an external alternating magnetic field in the probe region using an external magnetic field driving component. This causes a miniature permanent magnet, elastically bonded and fixed within a non-ferromagnetic outer casing, to oscillate slightly laterally, thereby applying a periodic lateral force to the root region of the elastic support of the fiber optic cantilever beam near the fiber optic fixing component. When the excitation frequency of the external alternating magnetic field equals the first-order natural resonant frequency of the fiber optic cantilever beam, resonance occurs, amplifying the lateral oscillation amplitude at its free end. Circular or near-circular scanning is achieved through mutually orthogonal alternating magnetic field components with a phase difference, and the scanning radius is altered by low-frequency envelope modulation, thus forming a forward-looking spiral scanning trajectory.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe, comprising a non-ferromagnetic outer sheath, an internal probe assembly, and an external magnetic field driving assembly. Specifically: The non-ferromagnetic outer sheath is the outermost structure of the probe, used to house and protect the internal structure. The non-ferromagnetic outer sheath is a one-piece hollow tubular structure with a large-diameter section and a small-diameter section inside. The large-diameter section is located near the end, and a transparent sealing window is provided at the end.

[0007] The built-in probe assembly is housed inside a non-ferromagnetic outer sleeve and includes an optical fiber, an optical fiber protective sleeve, a miniature permanent magnet, an optical fiber fixing component, and an optical component. The optical fiber fixing component is located at the junction of the large-diameter and small-diameter sections of the non-ferromagnetic outer sleeve. The fixing component has a through-hole in its center for the optical fiber and the protective sleeve to pass through. The fixing component is secured to the non-ferromagnetic outer sleeve using a cured, elastic adhesive. After passing through the fixing component, the portion of the optical fiber and the protective sleeve extending into the large-diameter section of the non-ferromagnetic outer sleeve forms an optical fiber cantilever beam. This cantilever beam extends from the fixing component towards the transparent sealing window, forming an optical fiber cantilever beam with one end elastically supported and the other end free. The optical component is located at the free end of the cantilever beam and is used to collimate, focus, and project the emitted beam from the optical fiber onto the sample to be tested. The miniature permanent magnet has an axial through hole, and its outer surface is bonded and fixed to the small diameter section of the non-ferromagnetic outer casing by a cured elastic adhesive, so that it can oscillate slightly under the action of an external alternating magnetic field and restrict significant axial movement.

[0008] The external magnetic field driving component is located outside the non-ferromagnetic outer casing and includes two sets of electromagnetic coils arranged orthogonally to each other, namely the X-direction coil group and the Y-direction coil group. Each group includes one or more electromagnetic coils, and the two groups contain the same number of electromagnetic coils.

[0009] During operation, an external alternating magnetic field penetrates the non-ferromagnetic outer sheath and acts on the miniature permanent magnet, subjecting it to an alternating magnetic torque. Under elastic bonding conditions, this causes periodic, minute lateral oscillations. These oscillations are transmitted through the optical fiber, fiber optic protective sheath, fiber optic fastener, and its elastic support structure to the root region of the elastic support of the fiber optic cantilever beam. This applies a periodic lateral excitation to the fiber optic cantilever beam that matches its first-order natural resonant frequency. Under this periodic lateral excitation, the fiber optic cantilever beam resonates, amplifying the lateral oscillation amplitude at its free end and enabling the emitted beam to perform high-frequency scanning.

[0010] Furthermore, in the non-ferromagnetic outer casing: a transparent sealing window is used to allow the probe light to transmit and to seal and protect the internal structure of the non-ferromagnetic outer casing. The transition between the large-diameter section and the small-diameter section is smooth.

[0011] Furthermore, in the built-in probe assembly: the fiber optic fixing component can maintain its axial position and allow the alternating lateral force generated by the micro permanent magnet to cause a small lateral displacement of the fiber optic cable and fiber optic protective sleeve. The fiber optic cable is used to transmit the probe light output by the OCT system and to transmit the echo signal returned by the sample to the OCT system. The fiber optic protective sleeve is disposed outside the fiber optic cable to improve the mechanical protection performance and assembly stability of the fiber optic cable. The end of the fiber optic cantilever beam near the fiber optic fixing component is the elastic support root region, and the end near the transparent sealing window is the free end. The fiber optic cable and fiber optic protective sleeve pass through the through-hole of the micro permanent magnet and maintain contact, abutment, or adhesive contact with the inner surface of the micro permanent magnet. The micro permanent magnet, as an elastically limited magnetic force transmission component, transmits alternating force to the elastic support root region of the fiber optic cantilever beam through the fiber optic protective sleeve and fiber optic fixing component under the action of an external magnetic field. The optical component uses a spherical lens or a combination of a GRIN lens and a focusing lens, and can be assembled through a lens mounting bracket.

[0012] Furthermore, in the external magnetic field driving assembly: the axis of the optical fiber is defined as the Z-axis, and two transverse directions perpendicular to the Z-axis and orthogonal to each other are defined as the X-direction and Y-direction, respectively. The X-direction coil group and the Y-direction coil group are used to generate external alternating magnetic field components varying along the X and Y directions in the region where the micro permanent magnet is located. The micro permanent magnet is magnetized along the Z-axis, making the magnetic moment direction of the micro permanent magnet substantially parallel to the axis of the optical fiber. The X-direction coil group and the Y-direction coil group receive high-frequency AC driving signals, and the two high-frequency AC driving signals have a predetermined phase difference, so that the two sets of electromagnetic coils generate two mutually orthogonal external alternating magnetic field components with a phase difference in the region where the micro permanent magnet is located.

[0013] Furthermore, the frequency of the high-frequency AC driving electrical signal is set to be equal to the first-order natural resonant frequency of the fiber cantilever beam.

[0014] Furthermore, the predetermined phase difference is 90 degrees. When the lateral excitations in the X and Y directions have a 90-degree phase difference, the resonant responses of the free ends of the fiber cantilever beam in the two orthogonal directions are synthesized to form a circular or near-circular scanning trajectory, which drives the outgoing beam to achieve high-frequency two-dimensional scanning.

[0015] Furthermore, the high-frequency AC drive signals input to the X-direction coil group and the Y-direction coil group are subjected to low-frequency envelope amplitude modulation, causing the amplitude of the external alternating magnetic field to change periodically with time. Since the resonant oscillation amplitude of the free end of the fiber cantilever beam changes with the transverse excitation amplitude, the low-frequency envelope amplitude modulation can continuously adjust the deflection radius of the free end of the fiber cantilever beam, causing the radius of the high-frequency circular or near-circular scanning trajectory to gradually increase or decrease with time, thereby forming a forward-looking helical scanning trajectory.

[0016] Furthermore, the low-frequency envelope amplitude modulation signal is a triangular wave, sawtooth wave, sine envelope, or other modulation signal capable of changing the amplitude of the external alternating magnetic field.

[0017] Furthermore, there is no mechanical contact or electrical connection between the external magnetic field drive component and the built-in probe component.

[0018] The method for using a magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe includes the following steps: Step 1: Assemble the fiber optic cantilever beam resonant forward-looking OCT scanning probe to be calibrated. This involves forming a fiber optic cantilever beam with one end elastically supported and the other end free within a non-ferromagnetic outer sheath, thus obtaining the scanning probe to be calibrated. Specifically: Step 1.1: Design a non-ferromagnetic outer sleeve and set an optical fiber fixing component at the junction of the large-diameter section and the small-diameter section of the non-ferromagnetic outer sleeve. Fix the optical fiber fixing component inside the non-ferromagnetic outer sleeve with an elastic adhesive after curing to obtain a non-ferromagnetic outer sleeve with an internal optical fiber fixing component. Step 1.2: Based on the non-ferromagnetic outer casing with fiber optic fixing components obtained in Step 1.1, the fiber optic cable and fiber optic protective sleeve are passed through the through holes of the micro permanent magnet and the fiber optic fixing components. The micro permanent magnet is then bonded and fixed to the small-diameter section of the non-ferromagnetic outer casing with a cured and elastic adhesive, thus obtaining an intermediate assembly probe with built-in fiber optic fixing components, micro permanent magnets, fiber optic cables and fiber optic protective sleeves. Step 1.3: Based on the intermediate assembly state probe obtained in Step 1.2, extend the optical fiber and optical fiber protective sleeve from the optical fiber fixing component toward the transparent sealing window to form an optical fiber cantilever beam, and set the optical component at the free end of the optical fiber cantilever beam. Then, bond and install the transparent sealing window to complete the probe encapsulation and obtain the scanning probe to be calibrated.

[0019] Step 2: Based on the scanning probe to be calibrated obtained in Step 1, the first-order natural resonant frequency of the fiber optic cantilever beam is theoretically predicted and experimentally calibrated to obtain the actual first-order natural resonant frequency of the current scanning probe; specifically: Step 2.1, in the design and preliminary research stage of the scanning probe structure to be calibrated, based on the Young's modulus of the optical fiber... Moment of inertia of fiber cross section The suspension length of the fiber optic cantilever beam Equivalent mass of optical components and the equivalent mass of the suspended portion of the fiber optic cantilever beam. The first-order natural resonant frequency of the fiber optic cantilever beam Make theoretical predictions: Step 2.2, based on the theoretical first-order natural resonance frequency obtained in Step 2.1 After the scanning probe to be calibrated is assembled, the amplitude of the input AC signal of the external magnetic field drive component is kept constant, and the frequency of the input AC signal is controlled within a certain range. -100Hz to Within a range of +100Hz, the frequency is gradually changed according to a preset step size to complete the frequency sweep; Step 2.3: Based on the frequency sweeping process in Step 2.2, signals are acquired through a high frame rate monitoring camera, spot position detection device or OCT system to monitor and record the vibration amplitude of the free end of the fiber cantilever beam in real time under different driving frequencies. Step 2.4: Based on the vibration amplitude obtained in Step 2.3, extract the driving frequency corresponding to the peak value of the vibration amplitude, and calibrate the driving frequency as the actual first-order natural resonance frequency of the current scanning probe in the current assembly state.

[0020] Step 3: Based on the actual first-order natural resonance frequency obtained in Step 2, perform forward-looking scanning imaging of the sample under test; specifically: Step 3.1: Use the actual first-order natural resonant frequency obtained in step 2 as the high-frequency carrier operating frequency of the external magnetic field drive component. Step 3.2: Based on the high-frequency carrier operating frequency determined in Step 3.1, input an AC signal with a predetermined phase difference to the X-direction coil group and the Y-direction coil group to make the fiber cantilever beam enter the resonant scanning state and make the free end of the fiber cantilever beam form a circular or approximately circular scanning trajectory. Step 3.3: Based on the circular or near-circular scanning trajectory formed in step 3.2, the AC signal input to the X-direction coil group and the Y-direction coil group is subjected to low-frequency envelope amplitude modulation, so that the deflection radius of the free end of the fiber cantilever beam changes continuously with time, forming a forward-looking spiral scanning trajectory. Step 3.4: Based on the forward-looking spiral scanning trajectory formed in step 3.3, the free end of the fiber cantilever beam drives the outgoing beam to scan the sample under test, and the echo signal returned by the sample under test is transmitted back to the OCT system by fiber 1 to obtain the forward-looking OCT image of the sample under test.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) By utilizing the resonant amplification of the fiber cantilever beam, a large field of view controllable forward scanning with low driving energy can be achieved.

[0022] (2) External alternating magnetic field drive, no internal electrical drive structure. The present invention applies alternating magnetic force to the micro permanent magnet inside the tube through an external magnetic field drive component. The probe does not need to be equipped with electrodes, wires or piezoelectric drive elements for driving scanning, which helps to reduce the risk of leakage and insulation failure in humid, liquid-filled or conductive environments.

[0023] (3) Reduce axial torsional stress and improve long-term operational reliability. This invention magnetizes a miniature permanent magnet along the fiber axial direction, so that the magnetic torque generated by the cross product of the magnetic moment vector and the external alternating magnetic field in the external XY plane is mainly located in the transverse plane. This design ensures that the fiber cantilever beam is mainly subjected to transverse excitation in the elastic support root region, which helps to reduce the torsional torque around the fiber's own central axis, reduce the risk of fiber fatigue fracture caused by shear stress accumulation during high-frequency scanning, and significantly improve the long-term operational reliability of the probe and the stability of the scanning trajectory.

[0024] (4) Simple structure and conducive to miniaturization. The present invention reduces the active electrical drive devices and their supporting circuits inside the probe. The built-in structure mainly includes optical fiber, optical fiber protective sleeve, miniature permanent magnet, optical fiber fixing component and optical components. The structure is compact and the assembly difficulty is low, which is conducive to the miniaturization of the probe. Attached Figure Description

[0025] Figure 1 This is a main sectional view of the internal structure of a magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe provided in Embodiment 1 of the present invention; Figure 2 This is a main sectional view of the internal structure of a magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe provided in Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the optical path when the probe of the present invention is in a stationary state; Figure 4 This is a schematic diagram of the optical path and operation of the probe of the present invention when it is in the resonant scanning state; Figure 5 This is a schematic diagram of the probe of the present invention forming a forward-looking spiral scanning trajectory.

[0026] In the figure: 1. Optical fiber; 2. Optical fiber protective sleeve; 3. Miniature permanent magnet; 4. Non-ferromagnetic outer casing; 5. Optical fiber fastener; 6. Lens mounting bracket; 7. GRIN lens; 8. Focusing lens; 9. Spherical lens; 10. Transparent sealing window; 11. Sample to be tested. Detailed Implementation

[0027] The structure and working principle of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention; the technical features in the various embodiments can be combined with each other without conflict.

[0028] like Figure 1 and Figure 2 As shown, this embodiment provides a magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe, including a non-ferromagnetic outer sleeve 4, a built-in probe assembly, and an external magnetic field driving assembly. The built-in probe assembly is disposed inside the non-ferromagnetic outer sleeve 4, and the external magnetic field driving assembly is disposed outside the non-ferromagnetic outer sleeve 4.

[0029] In this embodiment, the non-ferromagnetic outer sheath 4 is made of medical-grade quartz glass, with an overall outer diameter of 2.5 mm. The non-ferromagnetic outer sheath 4 is a one-piece hollow tubular structure with a large-diameter section and a small-diameter section inside. The large-diameter section is located near the transparent sealing window 10, and the small-diameter section is located at the rear end of the probe. The inner diameter of the large-diameter section is 1.8 mm, and the inner diameter of the small-diameter section is 0.8 mm, with a smooth transition between the two sections.

[0030] In this embodiment, the transparent sealing window 10 is sealed to the front end of the non-ferromagnetic outer casing 4. The transparent sealing window 10 is made of quartz glass and is used to allow the probe light to pass through and to seal and protect the internal structure of the non-ferromagnetic outer casing 4. The sample to be tested 11 is located in front of the transparent sealing window 10, such as... Figure 3 As shown, when the probe is stationary, the detection light emitted from the optical fiber 1 is shaped by the optical components, passes through the transparent sealing window 10, and is projected onto the sample 11 to be tested.

[0031] In this embodiment, the built-in probe assembly includes an optical fiber 1, an optical fiber protective sleeve 2, a miniature permanent magnet 3, an optical fiber fixing component 5, and optical components. The optical fiber 1 is a 9 / 125μm single-mode fiber used to transmit the probe light output by the OCT system and to transmit the echo signal returned by the sample 11 to the OCT system. The optical fiber protective sleeve 2 is made of polyimide and covers the outside of the optical fiber 1 to improve the mechanical protection performance and assembly stability of the optical fiber 1.

[0032] In this embodiment, the fiber optic fixing member 5 is disposed at the junction of the large-diameter section and the small-diameter section of the non-ferromagnetic outer casing 4, and the fiber optic fixing member 5 is made of zirconia ceramic. The fiber optic fixing member 5 has a through hole in the middle for the fiber optic 1 and the fiber optic protective sleeve 2 to pass through. The fiber optic fixing member 5 is fixed in the non-ferromagnetic outer casing 4 by a cured elastic adhesive, so that the fiber optic fixing member 5 is positioned in the axial direction, and allows the alternating lateral force generated by the micro permanent magnet 3 to cause a small lateral displacement of the fiber optic 1 and the fiber optic protective sleeve 2.

[0033] In this embodiment, after the optical fiber 1 and the optical fiber protective sleeve 2 pass through the optical fiber fixing member 5, the portion extending into the large-diameter section of the non-ferromagnetic outer casing 4 forms an optical fiber cantilever beam. The optical fiber cantilever beam extends from the optical fiber fixing member 5 towards the transparent sealing window 10, constituting an optical fiber cantilever beam with one end elastically supported and the other end free. The end of the optical fiber cantilever beam closer to the optical fiber fixing member 5 is the elastically supported root region, and the end closer to the transparent sealing window 10 is the free end. In this embodiment, the suspension length L of the optical fiber cantilever beam is 10 mm.

[0034] In this embodiment, the miniature permanent magnet 3 is made of neodymium iron boron permanent magnet material and is magnetized along the axial direction of the optical fiber 1. The miniature permanent magnet 3 has a through hole extending along the axial direction. The optical fiber 1 and the optical fiber protective sleeve 2 pass through the through hole of the miniature permanent magnet 3 and maintain close contact with the inner surface of the miniature permanent magnet 3. The outer surface of the miniature permanent magnet 3 is bonded and fixed to the small-diameter section of the non-ferromagnetic outer casing 4 by a cured elastic adhesive, so that the miniature permanent magnet 3 can produce a slight oscillation under the action of an external alternating magnetic field and restrict the miniature permanent magnet 3 from significant axial movement.

[0035] In this embodiment, the miniature permanent magnet 3 is located within the small-diameter section behind the optical fiber fixing member 5, and not at the free end of the optical fiber cantilever beam. As an elastically limited magnetic force transmission component, the miniature permanent magnet 3 transmits alternating force to the elastic support root region of the optical fiber cantilever beam via the optical fiber protective sleeve 2 and the optical fiber fixing member 5 under the action of an external alternating magnetic field.

[0036] In Example 1, as Figure 1 As shown, the optical component uses a spherical lens 9. The spherical lens 9 is fixed to the lens holder 6 with optical adhesive and is located at the free end of the fiber cantilever beam to focus the beam emitted from the fiber 1 onto the sample 11 to be tested.

[0037] In Example 2, as Figure 2 As shown, the optical assembly includes a GRIN lens 7 and a focusing lens 8 arranged sequentially along the optical path. The diverging beam emitted from the fiber 1 is collimated into a parallel beam by the GRIN lens 7, and then converged onto the surface of the sample 11 under test by the focusing lens 8. The GRIN lens 7 and the focusing lens 8 are bonded together with optical adhesive and fixed to the lens holder 6.

[0038] In this embodiment, the external magnetic field driving component includes two sets of orthogonally arranged electromagnetic coils, namely an X-direction coil set and a Y-direction coil set. The X-direction coil set includes two opposing electromagnetic coils, and the Y-direction coil set includes two opposing electromagnetic coils. The axis of the optical fiber 1 is defined as the Z-axis, and two transverse directions perpendicular to the Z-axis and orthogonal to each other are defined as the X-direction and Y-direction, respectively. The X-direction coil set and the Y-direction coil set are used to generate external alternating magnetic field components varying along the X-direction and Y-direction in the region where the miniature permanent magnet 3 is located, respectively.

[0039] In this embodiment, the X-direction coil group and the Y-direction coil group respectively receive high-frequency AC drive signals. The phase difference between the two high-frequency AC drive signals is 90 degrees, so that the two sets of electromagnetic coils generate two mutually orthogonal external alternating magnetic field components with a 90-degree phase difference in the region where the miniature permanent magnet 3 is located. There is no mechanical contact or electrical connection between the external magnetic field drive component and the built-in probe component.

[0040] During operation, an external alternating magnetic field penetrates the non-ferromagnetic outer casing 4 and acts on the miniature permanent magnet 3, causing the miniature permanent magnet 3 to experience an alternating magnetic torque and generate periodic minute lateral oscillations under elastic bonding conditions. These periodic minute lateral oscillations are transmitted through the optical fiber 1, the optical fiber protective sleeve 2, and the optical fiber fixing component 5 to the elastic support root region of the optical fiber cantilever beam, thereby applying periodic lateral excitation to the optical fiber cantilever beam.

[0041] like Figure 4 As shown, when the frequency of the high-frequency AC driving signal is equal to the actual first-order natural resonant frequency of the fiber optic cantilever beam, the fiber optic cantilever beam resonates under periodic transverse excitation, amplifying the transverse oscillation amplitude of its free end and driving the emitted beam to achieve high-frequency scanning. When the transverse excitations in the X and Y directions have a 90-degree phase difference, the resonant responses of the free end of the fiber optic cantilever beam in the two orthogonal directions are synthesized to form an approximately circular scanning trajectory.

[0042] This embodiment also provides the assembly, calibration, and usage methods of the above-mentioned magnetic field-driven fiber cantilever beam resonant forward-looking OCT scanning probe, including the following steps: Step 1: Assemble the fiber optic cantilever beam resonant forward-looking OCT scanning probe to be calibrated, so that fiber optic 1 and fiber optic protective sleeve 2 form a fiber optic cantilever beam with one end elastically supported and the other end free within the non-ferromagnetic outer casing 4, thus obtaining the scanning probe to be calibrated; specifically: Step 1.1: Design a non-ferromagnetic outer sleeve 4, and set an optical fiber fixing component 5 at the junction of the large-diameter section and the small-diameter section of the non-ferromagnetic outer sleeve 4. Fix the optical fiber fixing component 5 inside the non-ferromagnetic outer sleeve 4 with an elastic adhesive after curing, and obtain a non-ferromagnetic outer sleeve 4 with an optical fiber fixing component 5 inside. Step 1.2: Based on the non-ferromagnetic outer sleeve 4 with fiber optic fixing component 5 obtained in Step 1.1, fiber optic 1 and fiber optic protective sleeve 2 are passed through the through hole of micro permanent magnet 3 and fiber optic fixing component 5, and micro permanent magnet 3 is bonded and fixed in the small diameter section of non-ferromagnetic outer sleeve 4 with a cured elastic adhesive, thus obtaining an intermediate assembly state probe with fiber optic fixing component 5, micro permanent magnet 3, fiber optic 1 and fiber optic protective sleeve 2 inside. Step 1.3: Based on the intermediate assembly state probe obtained in Step 1.2, the optical fiber 1 and the optical fiber protective sleeve 2 are extended from the optical fiber fixing component 5 toward the transparent sealing window 10 to form an optical fiber cantilever beam. An optical component is set at the free end of the optical fiber cantilever beam, and the transparent sealing window 10 is bonded and installed to complete the probe encapsulation, thus obtaining the scanning probe to be calibrated.

[0043] Step 2: Based on the scanning probe to be calibrated obtained in Step 1, the first-order natural resonant frequency of the fiber optic cantilever beam is theoretically predicted and experimentally calibrated to obtain the actual first-order natural resonant frequency of the current scanning probe; specifically: Step 2.1, in the design and preliminary research stage of the scanning probe structure to be calibrated, based on the Young's modulus of fiber 1... Moment of inertia of fiber cross section The suspension length of the fiber optic cantilever beam Equivalent mass of optical components and the equivalent mass of the suspended portion of the fiber optic cantilever beam. The first-order natural resonant frequency of the fiber optic cantilever beam Make theoretical predictions: Step 2.2, based on the theoretical first-order natural resonance frequency obtained in Step 2.1 After the scanning probe to be calibrated is assembled, the amplitude of the input AC signal of the external magnetic field drive component is kept constant, and the frequency of the input AC signal is controlled to gradually change within a preset step size in the range of 130Hz to 330Hz to complete the frequency sweep. In this embodiment, the theoretical first-order natural resonant frequency is 230Hz; Step 2.3: Based on the frequency sweeping process in Step 2.2, the vibration amplitude of the free end of the fiber optic cantilever beam at different driving frequencies is monitored and recorded by a high frame rate monitoring camera. Step 2.4: Based on the vibration amplitude obtained in Step 2.3, extract the driving frequency corresponding to the peak vibration amplitude, and calibrate this driving frequency as the actual first-order natural resonant frequency of the current scanning probe in the current assembly state. In this embodiment, the actual first-order natural resonant frequency is 240Hz.

[0044] Step 3: Based on the actual first-order natural resonance frequency obtained in Step 2, perform forward-looking scanning imaging on the sample 11 to be tested; specifically: Step 3.1: Use the 240Hz obtained in Step 2 as the high-frequency carrier operating frequency of the external magnetic field drive component; Step 3.2: Based on the high-frequency carrier operating frequency determined in Step 3.1, input a high-frequency AC drive signal with a 90-degree phase difference to the X-direction coil group and the Y-direction coil group, causing the fiber optic cantilever beam to enter a resonant scanning state, and causing the free end of the fiber optic cantilever beam to form as shown in the figure. Figure 4 The approximate circular scanning trajectory shown; Step 3.3: Based on the approximate circular scanning trajectory formed in step 3.2, the high-frequency AC drive signal input to the X-direction coil group and the Y-direction coil group is modulated with a 2Hz triangular wave low-frequency envelope amplitude, so that the deflection radius of the free end of the fiber cantilever beam changes continuously with time. Step 3.4, based on the deflection radius that changes continuously with time in step 3.3, causes the free end of the fiber cantilever beam to drive the emitted beam to form a shape on the surface of the sample 11 under test, as shown in step 3.3. Figure 5 The forward-looking spiral scanning trajectory shown is used to transmit the echo signal returned by the sample 11 to the OCT system via optical fiber 1, so as to obtain the forward-looking OCT image of the sample 11.

[0045] The above description is merely a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For those skilled in the art, various modifications or improvements can be made to the materials, dimensions, magnetization direction, coil arrangement, driving waveform, front-end optical component form, and assembly method without departing from the concept of the present invention, and all such modifications or improvements should fall within the scope of protection of the present invention.

Claims

1. A magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe, characterized in that, The fiber optic cantilever beam resonant forward-looking OCT scanning probe includes a non-ferromagnetic outer sleeve (4), a built-in probe assembly, and an external magnetic field drive assembly. The non-ferromagnetic outer shell (4) is the outermost structure of the probe. It is a hollow tubular structure formed in one piece, with a large-diameter section and a small-diameter section inside. The large-diameter section is near the end, and the end is provided with a transparent sealing window (10). The built-in probe assembly is located inside the non-ferromagnetic outer sleeve (4) and includes an optical fiber (1), an optical fiber protective sleeve (2), a miniature permanent magnet (3), an optical fiber fixing component (5), and an optical component. The optical fiber fixing component (5) is located at the junction of the large-aperture section and the small-aperture section. The middle part of the optical fiber fixing component (5) has a through hole for the optical fiber (1) and the optical fiber protective sleeve (2) to pass through. The optical fiber fixing component (5) is fixed inside the non-ferromagnetic outer sleeve (4) by a cured elastic adhesive. After the optical fiber (1) and the optical fiber protective sleeve (2) pass through the optical fiber fixing component (5), The portion extending into the large aperture section forms an optical fiber cantilever beam with one end elastically supported and the other end free. The optical fiber cantilever beam extends from the optical fiber fixing member (5) toward the end direction. The optical component is set at the free end of the optical fiber cantilever beam to collimate, focus and project the emitted beam of the optical fiber (1) onto the sample to be tested (11). The micro permanent magnet (3) is provided with a through hole that runs through the axis. Its outer surface is bonded and fixed to the small aperture section of the non-ferromagnetic outer casing (4) by an elastic adhesive after curing, so that it swings under the action of an external alternating magnetic field and restricts axial movement. The external magnetic field driving component is located outside the non-ferromagnetic outer casing (4) and includes two sets of electromagnetic coils arranged orthogonally to each other, namely the X-direction coil group and the Y-direction coil group, which contain the same number of electromagnetic coils. During operation, the external alternating magnetic field penetrates the non-ferromagnetic outer casing (4) and acts on the micro permanent magnet (3). The micro permanent magnet (3) generates periodic lateral oscillation, which is transmitted to the elastic support root region of the fiber cantilever beam, thereby applying periodic lateral excitation to the fiber cantilever beam. The fiber cantilever beam resonates, amplifying the lateral oscillation amplitude of its free end, and driving the outgoing beam to achieve high-frequency scanning.

2. The magnetic field-driven fiber cantilever beam resonant forward-looking OCT scanning probe according to claim 1, characterized in that, The large-diameter section and the small-diameter section have a smooth transition.

3. The magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe according to claim 1, characterized in that, In the built-in probe assembly: The fiber optic fastener (5) is able to maintain its position in the axial direction and allows the alternating lateral force generated by the micro permanent magnet (3) to cause lateral displacement of the fiber optic (1) and the fiber optic protective sleeve (2). The optical fiber (1) is used to transmit the probe light output by the OCT system and to transmit the echo signal returned by the sample (11) to the OCT system. The end of the fiber cantilever beam near the fiber fixing member (5) is the elastic support root area, and the end near the transparent sealing window (10) is the free end; The optical fiber (1) and the optical fiber protective sleeve (2) pass through the through hole of the micro permanent magnet (3) and maintain contact with the inner surface of the micro permanent magnet (3) by adhering, abutting or bonding. The micro permanent magnet (3) serves as a magnetic force transmission component with elastic limit. Under the action of an external magnetic field, it transmits alternating force to the elastic support root region of the fiber cantilever beam through the fiber protective sleeve (2) and the fiber fixing component (5). The optical components are spherical lenses (9) or a combination of GRIN lenses (7) and focusing lenses (8), and can be assembled by lens holders (6).

4. The magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe according to claim 1, characterized in that, In the external magnetic field driving component: The axis of the optical fiber (1) is defined as the Z-axis, and the two transverse directions perpendicular to the Z-axis and orthogonal to each other are defined as the X-direction and the Y-direction, respectively. The X-direction coil group and the Y-direction coil group are used to generate external alternating magnetic field components that vary along the X-direction and the Y-direction in the region where the micro permanent magnet (3) is located. The micro permanent magnet (3) is magnetized along the Z-axis direction, so that the magnetic moment direction of the micro permanent magnet (3) is basically parallel to the axis of the optical fiber (1); The X-direction coil group and the Y-direction coil group respectively receive high-frequency AC drive signals. The two high-frequency AC drive signals have a predetermined phase difference, so that the two sets of electromagnetic coils generate two mutually orthogonal external alternating magnetic field components with a phase difference in the region where the micro permanent magnet (3) is located. The frequency of the high-frequency AC drive signal is set to be equal to the first-order natural resonant frequency of the fiber cantilever beam.

5. The magnetic field-driven fiber cantilever beam resonant forward-looking OCT scanning probe according to claim 4, characterized in that, The predetermined phase difference is 90 degrees; when the lateral excitation in the X and Y directions has a 90-degree phase difference, the resonant responses of the free ends of the fiber cantilever beam in the two orthogonal directions are synthesized to form a circular or near-circular scanning trajectory, which drives the outgoing beam to achieve high-frequency two-dimensional scanning.

6. The magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe according to claim 5, characterized in that, The high-frequency AC drive signals input to the X-direction coil group and the Y-direction coil group are subjected to low-frequency envelope amplitude modulation, so that the amplitude of the external alternating magnetic field changes periodically with time. Since the resonant swing amplitude of the free end of the fiber cantilever beam changes with the transverse excitation amplitude, the low-frequency envelope amplitude modulation can continuously adjust the deflection radius of the free end of the fiber cantilever beam, so that the radius of the high-frequency circular or near-circular scanning trajectory gradually increases or decreases with time, and finally forms a forward-looking spiral scanning trajectory.

7. The magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe according to claim 6, characterized in that, The low-frequency envelope amplitude modulation signal is a triangular wave, a sawtooth wave, or a sinusoidal envelope.

8. The magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe according to claim 6, characterized in that, There is no mechanical contact or electrical connection between the external magnetic field drive component and the internal probe component.

9. A method for using a magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe, characterized in that... Based on the magnetic field-driven fiber cantilever beam resonant forward-looking OCT scanning probe according to any one of claims 1-8, the method includes the following steps: Step 1: Assemble the fiber cantilever beam resonant forward-looking OCT scanning probe to be calibrated, so that the fiber (1) and the fiber protective sleeve (2) form a fiber cantilever beam with one end elastically supported and the other end free within the non-ferromagnetic outer casing (4), and obtain the scanning probe to be calibrated; Specifically: Step 1.1: Design a non-ferromagnetic outer shell sleeve (4) and set an optical fiber fixing component (5) at the junction of the large-diameter section and the small-diameter section. Fix the optical fiber fixing component (5) inside the non-ferromagnetic outer shell sleeve (4) with an elastic adhesive after curing to obtain a non-ferromagnetic outer shell sleeve (4) with an optical fiber fixing component (5) inside. Step 1.2: Based on the non-ferromagnetic outer casing (4) with an internal fiber fixing component (5) obtained in Step 1.1, the fiber (1) and the fiber protective sleeve (2) are passed through the through hole of the micro permanent magnet (3) and the fiber fixing component (5), and the micro permanent magnet (3) is bonded and fixed in the small diameter section of the non-ferromagnetic outer casing (4) by the cured elastic adhesive, so as to obtain an intermediate assembly state probe with an internal fiber fixing component (5), micro permanent magnet (3), fiber (1) and fiber protective sleeve (2); Step 1.3: Based on the intermediate assembly state probe obtained in Step 1.2, the optical fiber (1) and the optical fiber protective sleeve (2) are extended from the optical fiber fixing component (5) toward the transparent sealing window (10) to form an optical fiber cantilever beam, and an optical component is set at the free end of the optical fiber cantilever beam. The transparent sealing window (10) is then bonded and installed to complete the probe encapsulation and obtain the scanning probe to be calibrated. Step 2: Based on the scanning probe to be calibrated obtained in Step 1, the first-order natural resonant frequency of the fiber optic cantilever beam is theoretically predicted and experimentally calibrated to obtain the actual first-order natural resonant frequency of the current scanning probe; specifically: Step 2.1, in the design and preliminary research stage of the scanning probe structure to be calibrated, based on the Young's modulus of the optical fiber (1) Moment of inertia of fiber cross section The suspension length of the fiber optic cantilever beam Equivalent mass of optical components and the equivalent mass of the suspended portion of the fiber optic cantilever beam. The first-order natural resonant frequency of the fiber optic cantilever beam The theoretical first-order natural resonance frequency was estimated. ; Step 2.2, based on the theoretical first-order natural resonance frequency obtained in Step 2.1 After the scanning probe to be calibrated is assembled, the amplitude of the input AC signal of the external magnetic field drive component is kept constant, and the frequency range of the input AC signal is controlled to complete the frequency sweep. Step 2.3: Based on the frequency sweeping process in Step 2.2, signals are acquired through a high frame rate monitoring camera, spot position detection device or OCT system to monitor and record the vibration amplitude of the free end of the fiber cantilever beam in real time under different driving frequencies. Step 2.4: Based on the vibration amplitude obtained in Step 2.3, extract the driving frequency corresponding to the peak value of the vibration amplitude, and calibrate the driving frequency as the actual first-order natural resonance frequency of the current scanning probe in the current assembly state. Step 3: Based on the actual first-order natural resonance frequency obtained in Step 2, perform forward-looking scanning imaging on the sample to be tested (11); specifically: Step 3.1: Use the actual first-order natural resonant frequency as the high-frequency carrier operating frequency of the external magnetic field drive component. Step 3.2: Based on the high-frequency carrier operating frequency, input an AC signal with a predetermined phase difference to the X-direction coil group and the Y-direction coil group to make the fiber cantilever beam enter the resonant scanning state and make the free end of the fiber cantilever beam form a circular or approximately circular scanning trajectory. Step 3.3: Based on the circular or near-circular scanning trajectory formed in step 3.2, the AC signal input to the X-direction coil group and the Y-direction coil group is subjected to low-frequency envelope amplitude modulation, so that the deflection radius of the free end of the fiber cantilever beam changes continuously with time, forming a forward-looking spiral scanning trajectory. Step 3.4: Based on the forward-looking spiral scanning trajectory formed in step 3.3, the free end of the fiber cantilever beam drives the outgoing beam to scan the sample under test (11), and the echo signal returned by the sample under test (11) is transmitted back to the OCT system by the fiber (1) to obtain the forward-looking OCT image of the sample under test (11).

10. The method of using the magnetic field-driven fiber optic cantilever beam resonant forward-looking OCT scanning probe according to claim 9, characterized in that, In step 2: In step 2.1, the theoretical first-order natural resonance frequency The calculation formula is: In step 2.2, the frequency of the input AC signal is controlled within... -100Hz to Within a range of +100Hz, the frequency is gradually changed according to a preset step size to complete the frequency sweep.

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