A multi-modal optical fiber endoscope imaging system and method

Abstract

The application provides a multi-modal optical fiber endoscope imaging system and method, and belongs to the technical field of multi-modal microscope imaging technology.The device comprises a laser space and time beam combining module, a compressed pulse module, a laser collimation module, a spatial light and optical fiber coupling module, a piezoelectric ceramic tube brake optical fiber module and an acquisition module.The application separates a light transmission optical fiber from an acquisition optical fiber in the multi-modal optical fiber endoscope, collects nonlinear signals generated by a plurality of optical fibers with a relatively high numerical aperture, and introduces an adjustable differential mechanical structure to adjust the position of the brake optical fiber and the micro lens group, improve the focusing effect, and further improve the imaging quality;the adjustable brake optical fiber and the micro lens group are concentrated in the multi-modal optical fiber endoscope imaging system, which is conducive to obtaining high-resolution images of biological samples by multiple components;and three modes are combined to realize multi-modal endoscopic imaging.

Description

Technical Field

[0001] This invention relates to the field of multimodal microscopy imaging technology, and in particular to a multimodal fiber optic endoscope imaging system and method. Background Technology

[0002] Multimodal microscopy imaging technology integrates various nonlinear optical imaging techniques. Its core principle is to utilize the nonlinear effect of matter under strong laser and low power to respond specifically to the chemical properties of biological tissues. This imaging method can avoid photobleaching and damage to biological tissues, thereby enabling label-free interrogation of biological tissues, which is of great significance in the field of biomedical research.

[0003] Common nonlinear optical imaging techniques include two-photon excitation fluorescence (2PEF) imaging, second harmonic generation (SHG) imaging, and coherent anti-Stokes Raman scattering (CARS) imaging. These techniques all achieve imaging based on the coherent characteristics of nonlinear effects. However, existing multimode fiber optic endoscopes typically transmit swept-frequency short-pulse signals through piezoelectrically actuated fibers and rely on the same fiber to collect nonlinear signals excited by the transmitted light. However, the precision of single-fiber excitation focusing (when numerical aperture mismatch) and the transmission effect of the beam excited by the sample through the same objective lens in the collection path limit the lateral resolution of fiber optic imaging, making it difficult to meet the requirements of higher-precision biological tissue imaging. At the same time, if the miniature objective lens is not precisely aligned, a single fiber will not produce a tightly focused spot, resulting in defocusing and insufficient imaging excitation power. In addition, the difficulty in concentrating multiple modes of imaging within the fiber, separating multiple nonlinear signals, and obtaining multimodal high-contrast images restricts the further development and application of this technology. Summary of the Invention

[0004] The purpose of this invention is to provide a multimodal fiber optic endoscope imaging system and method. In the multimodal fiber optic endoscope, the light transmission fiber and the acquisition fiber are separated. The nonlinear signal generated is collected by a multimode fiber bundle with a high numerical aperture. An adjustable differential mechanical structure is introduced to adjust the position of the braking fiber and the microlens group, thereby improving the beam focusing effect and the imaging quality. The three modes are combined to realize multimodal endoscopic imaging.

[0005] To achieve the above objectives, this invention proposes a multimodal fiber optic endoscope imaging system, comprising a laser spatial and temporal beam combining module, a compressed pulse module, a laser collimation module, a spatial light and fiber optic coupling module, a piezoelectric ceramic tube braking fiber optic module, and an acquisition module.

[0006] The laser spatial and temporal beam combining module includes a dual-color laser, a half-wave plate I, a polarizing beam splitter I, a dispersive medium delay glass rod I, a reflector A, a half-wave plate II, a polarizing beam splitter II, a dispersive medium delay glass rod II, a lens A, a reflector B, a reflector C, a lens B, a time delay stage, a reflector D, a reflector E, a beam combiner, a reflector G, a reflector H, a reflector I, a lens C, a lens D, and a reflector J;

[0007] The laser collimation module includes a reflector F, a lens E, a lens F, a reflector K, a lens G, a reflector L, and a lens H;

[0008] The compressed pulse module includes a beam splitter prism, a reflector M, a grating pair, and a reflector N;

[0009] The space light and fiber optic coupling module includes a microscope objective and a hollow fiber optic cable;

[0010] The piezoelectric ceramic tube braking fiber optic module includes a probe and a sample;

[0011] The acquisition module includes a dichroic mirror I, a lens I, a filter I, a lens J, a photomultiplier tube I, a dichroic mirror II, a lens K, a filter II, a lens L, a photomultiplier tube II, a dichroic mirror III, a lens M, a filter III, a lens N, and a photomultiplier tube III.

[0012] Preferably, half-wave plate I, half-wave plate II, and polarizing beam splitter I, polarizing beam splitter II are used, or a combination of beam splitter and attenuator is used instead.

[0013] Preferably, the grating pair is replaced with a prism grating pair, and a transmissive optical path is adopted, removing the reflector M and the reflector N.

[0014] Preferably, the probe includes a hollow single-mode optical fiber at the center, a piezoelectric ceramic tube and mounting mechanical parts, a differential structure mechanical parts, a microlens assembly and adapter mechanical parts, and a multimode fiber bundle.

[0015] Preferably, the piezoelectric ceramic tube and mounting mechanical components are replaced by a microelectromechanical system (MEMS) driven by electrostatics or electromagnetics; the differential mechanical components are used to adjust the distance between the optical fiber and the microlens group and the adapter mechanical components.

[0016] Preferably, the scanning laser transmitted through the hollow fiber is focused onto the sample by a microlens group, exciting the sample to generate nonlinear signal light, which is then collected by a multimode fiber bundle to generate the nonlinear signal.

[0017] The present invention also provides a multimodal fiber optic endoscope imaging method, comprising the following steps:

[0018] Step S1: Two laser beams are emitted from a dual-color laser, one is an infrared beam and the other is a tunable wavelength beam. After the power is adjusted by a half-wave plate and a polarizing beam splitter, the two broadband pulsed laser beams are linearly chirped in time by a dispersive medium delay glass rod.

[0019] Step S2: Guide the dual-beam pulse beam into the lens group for spatial overlap, guide the spatially overlapped dual-beam pulse beam into the time delay platform for time overlap, control the dual-beam pulses to overlap at a specific wavelength in time, and then guide them to the beam combiner via the reflector to combine the two beams.

[0020] Step S3: Guide the combined beam into the collimating lens group for laser collimation, then guide it through the reflector to the beam splitter prism for beam splitting, and guide it through the beam splitter prism and reflector to the grating pair. Adjust the angle of the grating pair to change the beam diffraction and disperse light of different wavelengths. Then, compress the fiber optic double beam and perform pulse broadening after passing through the fiber.

[0021] Step S4: The compressed beam is guided through the reflector and beam splitter to the collimating lens group to collimate the beam. The collimated beam is then transmitted to the microscope objective. The beam is coupled to the hollow fiber through the microscope objective, and the spatial light is transmitted to the hollow fiber in a coupled manner.

[0022] Step S5: The spatial light is guided to the output end through the hollow single-mode fiber at the center. The piezoelectric ceramic tube and the installation mechanical parts convert electricity into force to drive the fiber to vibrate. Then, the distance between the fiber and the microlens group is adjusted by the differential structure mechanical parts to achieve focusing. The scanning laser transmitted by the fiber is focused on the sample by the microlens group, which excites the sample to generate nonlinear signal light. The excited nonlinear signal light is collected by the outer multimode fiber bundle.

[0023] Step S6: The collected nonlinear signal light is separated into channel light of different wavelengths by a dichroic mirror, and then passed through a lens to three different narrowband filters for filtering. After the effective signal is filtered out, it is collimated by a lens and guided to a photomultiplier tube to collect the light signal.

[0024] Step S7: Convert the optical signal into an electrical signal and amplify it. After processing by subsequent circuits, perform multimodal image reconstruction.

[0025] Preferably, in step S5, the nonlinear signal source of the biological sample excited by the two laser beams is CARS, 2PEF, or SHG.

[0026] Therefore, this invention proposes a multimodal fiber optic endoscope imaging system and method, the advantages of which are as follows:

[0027] (1) The imaging device proposed in this invention has higher spatial resolution than traditional multimodal endoscope systems and can acquire high-resolution images of biological samples based on nonlinear optical imaging.

[0028] (2) The present invention uses a large numerical aperture optical fiber to collect nonlinear signals and uses a differential mechanical structure to controllably change the distance between the optical fiber and the microlens group to improve the beam focusing effect.

[0029] (3) The present invention concentrates three nonlinear effects in the endoscope, which can provide more biological information on biological samples at a higher resolution. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a multimodal fiber optic endoscope imaging system;

[0031] Figure 2 This is a schematic diagram of the probe structure of a multimodal fiber optic endoscope imaging system.

[0032] Figure 3 A flowchart of a multimodal fiber optic endoscope imaging method;

[0033] Figure 4 This is a schematic diagram of the transmission of a point light source;

[0034] Figure 5 This is a ray trajectory diagram using a 2μm Gaussian excitation source;

[0035] Figure 6 This is for imaging the lateral intensity map.

[0036] Figure Labels

[0037] 1. Two-color laser; 2. Half-wave plate I; 3. Polarizing beam splitter I; 4. Dispersive medium delay glass rod I; 5. Mirror A; 6. Half-wave plate II; 7. Polarizing beam splitter II; 8. Dispersive medium delay glass rod II; 9. Lens A; 10. Mirror B; 11. Mirror C; 12. Lens B; 13. Time delay stage; 14. Mirror D; 15. Mirror E; 16. Beam combiner; 17. Mirror F; 18. Mirror G; 19. Mirror H; 20. Mirror I; 21. Lens C; 22. Lens D; 23. Mirror J; 24. Lens E; 25. Lens F; 26. Mirror K; 27. Beam splitter prism; 28. Mirror M; 29. ​​Grating pair; 30. 31. Reflector N; 32. Lens G; 33. Reflector L; 34. Lens H; 35. Dichroic mirror I; 36. Lens I; 37. Filter I; 38. Lens J; 39. Photomultiplier tube I; 40. Dichroic mirror II; 41. Lens K; 42. Filter II; 43. Lens L; 44. Photomultiplier tube II; 45. Dichroic mirror III; 46. Lens M; 47. Filter III; 48. Lens N; 49. Photomultiplier tube III; 50. Microscope objective; 51. Hollow-core optical fiber; 52. Probe; 53. Sample; 54. Hollow-core single-mode optical fiber at the center; 55. Piezoelectric ceramic tube and mounting mechanical parts; 56. Differential structure mechanical parts; 57. Miniature lens group and its mechanical parts; 58. Multimode fiber bundle. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0040] Example 1

[0041] like Figure 1 and Figure 2 As shown, this invention provides a multimodal fiber optic endoscope imaging system. This system separates the transmission fiber and the acquisition fiber in the multimodal fiber optic endoscope, introduces an adjustable differential mechanical structure to improve the imaging quality, and combines three modes to realize multimodal endoscopic imaging. The system includes a laser spatial and temporal beam combining module, a compressed pulse module, a laser collimation module, a spatial light and fiber optic coupling module, a piezoelectric ceramic tube braking fiber optic module, and an acquisition module.

[0042] The laser spatial and temporal beam combining module includes a dual-color laser 1, a half-wave plate I 2, a polarizing beam splitter I 3, a dispersive medium delay glass rod I 4, a reflector A 5, a half-wave plate II 6, a polarizing beam splitter II 7, a dispersive medium delay glass rod II 8, a lens A 9, a reflector B 10, a reflector C 11, a lens B 12, a time delay stage 13, a reflector D 14, a reflector E 15, a beam combiner 16, a reflector G 18, a reflector H 19, a reflector I 20, a lens C 21, a lens D 22, and a reflector J 23.

[0043] The laser collimation module includes reflector F17, lens E24, lens F25, reflector K26, lens G31, reflector L32, and lens H33;

[0044] The compressed pulse module includes a beam splitter prism 27, a reflector M28, a grating pair 29, and a reflector N30;

[0045] The space light and fiber optic coupling module includes a microscope objective 49 and a hollow fiber 50;

[0046] The piezoelectric ceramic tube braking fiber optic module includes a probe 51 and a sample 52;

[0047] The acquisition module includes a dichroic mirror I34, a lens I35, a filter I36, a lens J37, a photomultiplier tube I38, a dichroic mirror II39, a lens K40, a filter II41, a lens L42, a photomultiplier tube II43, a dichroic mirror III44, a lens M45, a filter III46, a lens N47, and a photomultiplier tube III48.

[0048] The laser spatial and temporal beam combining module is used to expand the laser beam and maintain the spatial and temporal overlap efficiency of the two laser beams, providing a stable light source for multimodal signal excitation. The dual-color laser 1 is the core light source of the entire system, providing two laser beams: one a long-wavelength beam and the other a tunable wavelength beam, serving as the excitation source for CARS, 2PEF, and SHG signals, meeting the excitation wavelength requirements of different nonlinear signals. Half-wave plate I2, half-wave plate II6, polarizing beam splitter I3, and polarizing beam splitter II7 work together to adjust the laser power. Half-wave plate I2 and half-wave plate II6 change the laser polarization direction, while polarizing beam splitter I3 and polarizing beam splitter II7 separate the beams according to the polarization direction. Adjusting the waveplate angle controls the output power ratio of the two laser beams, ensuring intensity matching of the excitation signals. Dispersive medium delay glass rods I4 and II8 introduce linear chirp into the two broadband pulsed laser beams, dispersing different wavelength components in time, providing a basis for subsequent time overlap adjustment, and ensuring the time synchronization accuracy of the two beams. Through reflector D14, the power is adjusted using a reflector... Mirror G18 and mirror H19 guide the light beams into and out of time delay stage 13. Time delay stage 13 precisely controls the time difference between the two pulsed laser beams. By adjusting the optical path length, the two laser beams achieve precise temporal overlap at a specific wavelength, providing a key condition for signal excitation that relies on dual-beam time synchronization. Mirrors A5 and C11 guide the two pulsed light beams into lenses A9 and B12, and mirrors B10 and I20 guide the two pulsed light beams into lenses C21 and D22, achieving spatial overlap of the two laser beams. Through the focusing and collimating effect of the lenses, the two originally separate laser beams are spatially superimposed, ensuring that subsequent coupling and transmission result in the same composite beam. Mirrors E15 and J23 guide the composite beam to beam combiner 16. Beam combiner 16 integrates the two beams, completely merging the two spatially and temporally adjusted laser beams into one beam, which is then output to subsequent modules, ensuring the spatiotemporal consistency of the excitation light.

[0049] The compressed pulse module alters beam diffraction by adjusting the angle of the grating pair, providing different dispersion capabilities for different wavelengths of light to control the pulse broadening of the dual-beam beam entering the fiber. The beam splitter prism 27 splits the optical path, guiding the combined laser beam to the grating pair while simultaneously returning the beam to the main optical path, achieving dispersion adjustment. Reflectors M28 and N30 redirect the optical path, guiding the beam to the grating pair and reflecting the processed beam back to the beam splitter prism, ensuring a closed optical path. The grating pair 29, acting as the dispersion compensation core, changes the beam diffraction characteristics by adjusting the grating angle, generating differentiated dispersion for different wavelengths of light, opposite to the dispersion in the fiber. This counteracts the pulse broadening caused by dispersion during laser transmission in the fiber, maintaining a short pulse width and improving the excitation efficiency of nonlinear signals.

[0050] The laser collimation module ensures beam stability during long-distance transmission, reducing divergence or offset and providing a stable optical path for subsequent coupling and detection. Reflector F17 guides the laser from the compressed pulse module to lenses E24 and F25, while reflectors K26 and L32 guide it to lenses G31 and H33, and redirect it between the lenses to ensure long-distance transmission along the designed path. Lenses E24, F25, G31, and H33 collimate the beam, focusing and parallelizing it to transform divergent beams into parallel or small-divergence-angle beams, reducing beam spread during long-distance transmission and ensuring stable input light for subsequent coupling modules.

[0051] The spatial light and fiber optic coupling module reduces transmission loss and provides excitation light for the endoscope probe. By coupling the spatial light to the fiber optic cable via the microscope objective 49, the spatial light is transmitted to the curved fiber optic cable 50 in a highly efficient manner. The microscope objective 49 is key to efficient coupling. By selecting an objective with a numerical aperture close to that of the hollow fiber optic cable 50, the propagation angle of the spatial light is matched to the receiving angle of the fiber optic cable, maximizing optical coupling efficiency and reducing light leakage loss. The hollow fiber optic cable 50 serves as the light transmission carrier, transmitting the coupled spatial light to the endoscope probe through a curved path, adapting to the flexible detection requirements of the endoscope and avoiding the influence of probe curvature on the optical path.

[0052] The piezoelectric ceramic tube-driven fiber optic module drives the fiber optic scanning to excite signals from biological samples and collects nonlinear signals, serving as the core actuator of the endoscope probe. A central hollow single-mode fiber 53 precisely guides the laser transmitted to the probe to its output end, ensuring the excitation light is focused on the sample. The piezoelectric ceramic tube and its mounting mechanism 54 convert electricity into force, driving the fiber optic vibration and causing the excitation light to form a scanning spot on the sample, covering the imaging area. A differential mechanical component 55 slightly adjusts the distance between the fiber optic cable and the microlens assembly and its mechanical component 56, optimizing beam focusing, minimizing the spot size, and improving imaging resolution. The microlens assembly and its mechanical component 56 are used for beam converging, focusing the laser emitted from the fiber onto the surface of the sample 52, increasing local light intensity to meet the high-intensity requirements of nonlinear signal excitation. The outer multimode fiber bundle 57 collects the CARS, 2PEF, and SHG nonlinear signal light generated by the sample excitation and transmits it to the subsequent acquisition module. The sample 52 generates multimodal nonlinear signals under the action of the excitation light.

[0053] The acquisition module separates, filters, and detects multimodal signals, converting optical signals into electrical signals for imaging. Dichroic mirrors I34, II39, and III44 separate the mixed signal collected by the outer multimode fiber bundle 57 into different channels based on the wavelength differences of CARS, 2PEF, and SHG, thus avoiding signal interference. Filters I36, II41, and III46 filter stray light, with each channel equipped with a specific narrowband filter that allows only the effective signal of the target wavelength to pass through, filtering out ambient light, laser scattering, and other stray light to improve signal purity. Lenses I35, J37, K40, L42, M45, and N47 transmit the signal, focusing the separated and filtered signal light onto the photomultiplier tube to ensure efficient incident light onto the detector. Photomultiplier tubes I38, II43, and III48 collect the signal light and perform photoelectric conversion, converting the optical signal into an electrical signal and amplifying it to output an electrical signal sequence that can be processed by subsequent circuits, ultimately used for multimodal image reconstruction.

[0054] Example 2

[0055] like Figure 3 As shown, the present invention also provides a multimodal fiber optic endoscope imaging method, comprising the following steps:

[0056] Step S1: Two laser beams are emitted from a dual-color laser, one is an infrared beam and the other is a tunable wavelength beam. After the power is adjusted by half-wave plate I2, polarizing beam splitter I3, half-wave plate II6 and polarizing beam splitter II7, the two broadband pulsed laser beams are linearly chirped in time by dispersive medium delay glass rod I4 and dispersive medium delay glass rod II8 respectively.

[0057] Step S2: The dual-beam pulse beams are guided by reflectors A5 and C11 into lenses A9 and B12 for spatial alignment, then guided by reflector D14 into a time-delay platform for time alignment, and then guided out of the time-delay platform by reflectors G18 and H19. The dual-beam pulses are controlled to coincide at a specific wavelength in time, and then guided to the beam combiner by reflector E15. The dual-beam pulse beams are then guided by reflectors B10 and I20 into lenses C21 and D22 for spatial alignment, and then guided to the beam combiner by reflector J23 to combine the two beams.

[0058] Step S3: The combined beam is guided by mirror F17 into lens E24 and lens F25 for laser collimation, then guided by mirror K26 to beam splitter prism 27 for beam splitting, and then guided by beam splitter prism 27 and mirror M28 to grating pair 29. The angle of grating pair 29 is adjusted to change the beam diffraction and disperse light of different wavelengths. Then the pulse broadening of the compressed fiber double beam after passing through the fiber is performed.

[0059] Step S4: The compressed beam is guided through mirror N30, beam splitter prism 27, mirror K26, mirror M28 and mirror L32 to lens G31 and lens H33 to collimate the beam. The collimated beam is then transmitted to microscope objective 49. The beam is coupled to hollow fiber 50 through microscope objective 49, and the spatial light is transmitted to the bent hollow fiber 50 in a coupled manner.

[0060] Step S5: The spatial light is guided to the output end through the hollow single-mode fiber 53 at the center. The piezoelectric ceramic tube and the mounting mechanical parts 54 convert electricity into force to drive the fiber to vibrate. Then, the distance between the fiber and the microlens group is adjusted by the differential structure mechanical parts 55 to achieve focusing. The scanning laser transmitted by the fiber is focused onto the sample 52 through the microlens group and its mechanical parts 56, which excites the sample to generate nonlinear signal light CARS, 2PEF, and SHG. The excited nonlinear signal light is collected by the outer multimode fiber bundle 57.

[0061] Step S6: The collected nonlinear signal light is separated into channel light of different wavelengths by dichroic mirrors I34, II39, and III44. The light is then passed through lenses I35, K40, and M45 to three different narrowband filters: filter I36, filter II41, and filter III46. After filtering out the effective signal, the light is collimated by lenses J37, L42, and N47 and then guided to photomultiplier tubes I38, II43, and III48 to collect the light signal.

[0062] Step S7: Convert the optical signal into an electrical signal and amplify it. After processing by subsequent circuits, perform multimodal image reconstruction.

[0063] The invention will be further illustrated below through specific implementation examples.

[0064] In a specific embodiment of the present invention, a hollow anti-resonant optical fiber is used to excite the sample, with a specific excitation wavelength of 920 nm. The specific design parameters of the microlens group are: numerical aperture 0.22 on the fiber side and 0.58 on the sample side.

[0065] Step S1: Turn on the 920nm wavelength excitation source made of hollow-core anti-resonant fiber, adjust the output power of the source to a stable state, and fused the hollow-core anti-resonant layer fiber to a small-sized GRIN fiber. The GRIN fiber determines the numerical aperture at the focal point on the fiber side. Align it with the microlens group, and through the coupling structure with a numerical aperture of 0.22 on the fiber side, the beam is efficiently injected and transmitted to the distal end of the endoscope lens. Perform preliminary pre-calibration, and scan the piezoelectric ceramic-controlled fiber to acquire the beam trajectory.

[0066] Step S2: GRIN fibers with different refractive indices are fused with hollow fibers. The output spot size and divergence angle are tested. The output divergence angle is matched with the divergence angle of the GRIN objective to obtain a larger coupling efficiency. A smaller output spot size achieves the tightest focusing effect. There is a trade-off between divergence angle and spot size. Adjusting the differential mechanical structure can improve the system's imaging quality.

[0067] Step S3: Perform axial position calibration. In the initial state, adjust the lens group to the reference position through the adjustable focus assembly so that the excitation beam is focused by the GRIN lens and the focal point is located at the fiber side focal length of the microlens group. Fine-tune the variable mechanical structure and synchronously adjust the laser output power to make the image clear.

[0068] Step S4: The signal excited by the sample is collected by the outer multimode fiber bundle and transmitted to the detector to acquire the signal source. The acquired signal is processed by the acquisition card and aligned with the output timing of the piezoelectric ceramic tube to restore the imaging information of the scanned curve.

[0069] The following explains how the focused spot and divergence angle affect image quality, and analyzes the simulation results. The specific analysis process and results are as follows:

[0070] Resolution Verification: Based on the theoretical resolution formula for two-photon imaging, the theoretical resolution is calculated. The specific calculation formula is as follows:

[0071] ;

[0072] in, NA represents the resolution of two-photon imaging, and NA represents the numerical aperture of the objective lens on the sample side. This is the excitation wavelength. When two-photon imaging is at full width at half maximum (FWHM), it needs to be multiplied by [missing value]. When the excitation wavelength is 920nm, and the fiber side fills the entrance pupil, as shown... Figure 4 When the beam divergence angle on the fiber side matches the beam from the fiber-side lens, the theoretical two-photon resolution limit is 2× when the numerical aperture on the sample side is 0.58. =607nm; the theoretical resolution limit of Gaussian light is 967.6nm. The theoretical limit of two-photon light is lower than that of Gaussian light, but there is a proportional relationship between the two in the limiting diffraction formula. The improved image-side focusing effect of Gaussian focused beams can simultaneously improve the resolution of nonlinear imaging.

[0073] Resolution Verification: When the object-side numerical aperture and beam numerical aperture do not match, if the object-side numerical aperture is 0.2, the simulated image-side numerical aperture is 0.53. At this point, the Gaussian diffraction limit is 1058 nm, and the two-photon diffraction limit is 665 nm. The diffraction spot increases, reducing resolution. Therefore, it is necessary to measure the incident light divergence angle on the fiber side and select a suitable GRIN fiber for replacement splicing to maintain the match between the beam and the numerical aperture of the microlens group. However, if the beam angle is greater than the ideal angle (the ideal beam angle that matches the numerical aperture on the fiber side of the microlens group), it will affect the incident power, such as... Figure 5 As shown, the increased number of edge rays leads to increased edge ray reflection, which in turn increases aberrations and reduces the focusing spot convergence quality. Furthermore, precisely matching the objective lens with the hollow-core fiber in a GRIN fiber increases probe costs significantly. Therefore, in optical assembly, a GRIN fiber capable of producing a beam slightly smaller than the numerical aperture of the microlens group fiber side is fused with a hollow-core fiber. Simultaneously, by introducing an adjustable mechanical structure and selecting a suitable distance, an increase in the image-side numerical aperture is achieved. For example, for a beam with a numerical aperture of 0.2 (numerical aperture equivalent divergence angle), adjusting the distance theoretically changes the image-side numerical aperture to 0.54, at which point the diffraction spot size is... Figure 6 With a wavelength of 1.05 μm, close to the diffraction limit, the resolution of imaging under mismatched conditions using this probe can be improved. When the beam is aligned without deviation, the Gaussian light focusing resolution reaches 1 μm, close to the theoretical limit, and the two-photon imaging resolution is also correspondingly improved. Compared with nonlinear endoscopes whose imaging resolution is comparable to or slightly higher than that of laser wavelength, the above method can maintain a comparable resolution, ensure the energy density of the focused field, and improve the clarity of the image.

[0074] The multimodal fiber optic endoscope imaging system and method provided in this embodiment achieve high-resolution imaging under conditions of excitation beam shift or defocus by utilizing the efficient transmission of hollow-core anti-resonant fiber, the increased divergence angle of GRIN fiber and hollow-core fiber fusion splicing, the precise focusing of the GRIN lens group, and the compensation of the adjustable focusing component. Its core advantage lies in the combination of mechanical focusing and optical design, which fully utilizes the numerical aperture and stabilizes the focal position, providing a reliable technical solution for endoscopic imaging.

[0075] It is worth noting that all contents not described in detail in this invention are existing technologies and are well known to those skilled in the art.

[0076] Therefore, this invention provides a multimodal fiber optic endoscope imaging system and method. By designing a fiber optic probe structure, three modes of signal light are transmitted through a single hollow fiber to excite a sample with a short-pulse laser. The generated nonlinear signal is collected through a high numerical aperture fiber. GRIN fiber and a microlens group are used to enhance beam focusing, thereby improving the resolution of the multimodal fiber optic endoscope imaging system. A differential structure is designed to adjust the distance between the fiber and the microlens group, improving the system's focusing effect and concentrating it within the multimodal fiber optic endoscope imaging system. This facilitates the acquisition of high-resolution images of multi-component biological samples. Simultaneously, the flexible and bendable nature of optical fibers makes them suitable for in vivo imaging research. Compared to traditional multimodal fiber optic endoscope imaging schemes, this application not only improves image resolution but also enables label-free imaging of biological tissues such as the gastrointestinal tract and oral cavity, obtaining multi-component, clear tissue images.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A multi-modal optical fiber endoscope imaging method, characterized by, The method comprises the following steps: Step S1: two beams of laser are emitted by a dual-color laser, one is an infrared light beam, and the other is a tunable wavelength light beam; after the power is adjusted by a half-wave plate and a polarization beam splitter, the two beams of broadband pulsed laser are linearly chirped in time by a dispersion medium delay glass rod; Step S2: the two beams of pulsed light are guided into a lens group for spatial superposition, and then guided into a time delay platform for time superposition; the specific wavelength of the two beams of pulsed light is controlled to be superposed in time, and then guided to a beam combiner by a mirror; and the two beams of light are combined by the beam combiner; Step S3: the combined light beam is guided into a collimating lens group for laser collimation, and then guided to a beam splitter prism by a mirror; the light beam is guided to a grating pair by the beam splitter prism and the mirror; the angle of the grating pair is adjusted to change the diffraction of the light beam, disperse the light of different wavelengths, and then compress the pulse broadening of the fiber after the fiber double-beam light; Step S4: the compressed light beam is guided to a collimating lens group by a mirror and a beam splitter prism for collimation; the collimated light beam is transmitted to a microscope objective; the light beam is coupled to a hollow core fiber through the microscope objective; and the spatial light is coupled to the hollow core fiber in a coupled manner; Step S5: the spatial light is guided to an exit end through a center hollow core single-mode fiber; a piezoelectric ceramic tube and a mounting mechanical part convert electricity into force to drive the fiber to vibrate; the distance between the fiber and a micro lens group is adjusted by a differential structure mechanical part to realize focusing; the scanning laser transmitted by the fiber is focused on a sample through the micro lens group to excite the sample to generate nonlinear signal light; and the excited nonlinear signal light is collected by an outer multi-mode fiber bundle; Step S6: the collected nonlinear signal light is separated into different wavelength channel lights by a dichroic mirror; the different wavelength channel lights are filtered by three different narrowband filters through a lens; the effective signal is filtered out and then collimated by a lens and guided to a photomultiplier tube to collect the optical signal; Step S7: the optical signal is converted into an electrical signal and amplified; and after subsequent circuit processing, a multi-modal image is reconstructed.

2. The multi-modal fiber optic endoscopic imaging method of claim 1, wherein: In step S5, the nonlinear signal light source of the biological sample excited by the two beams of laser is CARS, 2PEF or SHG.

3. A multi-modal optical fiber endoscope imaging system for implementing the multi-modal optical fiber endoscope imaging method of any one of claims 1-2, characterized by: The method comprises a laser space and time beam combining module, a compressed pulse module, a laser collimation module, a spatial light and fiber coupling module, a piezoelectric ceramic tube brake fiber module and an acquisition module; The laser space and time beam combining module comprises a dual-color laser, a half-wave plate I, a polarization beam splitter I, a dispersion medium delay glass rod I, a mirror A, a half-wave plate II, a polarization beam splitter II, a dispersion medium delay glass rod II, a lens A, a mirror B, a mirror C, a lens B, a time delay table, a mirror D, a mirror E, a beam combiner, a mirror G, a mirror H, a mirror I, a lens C, a lens D and a mirror J; The laser collimation module comprises a mirror F, a lens E, a lens F, a mirror K, a lens G, a mirror L and a lens H; The compressed pulse module comprises a beam splitter prism, a mirror M, a grating pair and a mirror N; The spatial light and fiber coupling module comprises a microscope objective and a hollow core fiber; The piezoelectric ceramic tube brake fiber module comprises a probe and a sample. The collection module comprises dichroic mirror I, lens I, filter I, lens J, photomultiplier I, dichroic mirror II, lens K, filter II, lens L, photomultiplier II, dichroic mirror III, lens M, filter III, lens N and photomultiplier III.

4. A multi-modal optical fiber endoscope imaging system according to claim 3, characterized in that: When the optical path is of the transmission type, the prism grating pair is adopted, and the mirrors M and N are removed.

5. The multi-modal fiber optic endoscopic imaging system of claim 3, wherein: The probe comprises a center hollow single-mode optical fiber, a piezoelectric ceramic tube and mounting mechanical component, a differential structure mechanical component, a micro-lens group and adaptive mechanical component, and a multi-mode optical fiber bundle.

6. A multi-modal optical fiber endoscopic imaging system according to claim 5, wherein: The piezoelectric ceramic tube and mounting mechanical component are replaced by a micro-electromechanical structure (MEMS) driven by electrostatic or electromagnetic force; and the differential structure mechanical component is used to adjust the distance between the optical fiber and the micro-lens group and adaptive mechanical component.

7. The multi-modal fiber optic endoscopic imaging system of claim 3, wherein: The scanning laser transmitted by the hollow optical fiber is converged at the sample by the micro-lens group, excites the sample to generate nonlinear signal light, and the nonlinear signal is collected by the multi-mode optical fiber bundle.

Images