A multi-photon fiber array endoscopic imaging device and method based on hollow helical scanning

Abstract

The application discloses a kind of multi-photon fiber array endoscopic imaging device and method based on hollow spiral scanning, belong to biological imaging technical field.The device includes laser collimation and beam expansion module, pulse chirp module, beam switching module, endoscopic detection module and fluorescence acquisition module.The beam switching module contains optical switch and at least two low group velocity dispersion single-mode fiber array;Endoscopic detection module drives fiber array to perform hollow spiral scanning by resonant driver, its track starting point is not located at the origin of field of view, to avoid central dense sampling.The method switches fiber by optical switch, so that each fiber performs spatial non-overlapping hollow spiral scanning, collects multi-photon signals such as fluorescence, second harmonic and fluorescence lifetime, and completes the central cavity by image reconstruction and fusion, to obtain complete field of view imaging result.The application significantly reduces the central region light damage, improves the uniformity of imaging resolution, and the fused image is based on physical sampling to ensure authenticity and reliability, with high system stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-imaging, in particular to a multi-photon fiber array endoscopic imaging device and method based on a hollow spiral scanning. BACKGROUND

[0002] At present, multi-photon microscopic endoscopy technology has great application potential in the field of biomedicine due to its advantages such as no need for exogenous markers, strong tissue penetration ability, high sensitivity and specificity, excellent spatial resolution, and intrinsic optical sectioning capability. Among them, the multi-photon endoscopic system based on piezoelectric ceramic tube, gradient refractive index lens (GRIN lens) and low group velocity dispersion optical fiber has become the mainstream scheme, which realizes spiral scanning by driving the cantilever optical fiber through the piezoelectric ceramic tube to complete the imaging.

[0003] However, the traditional spiral scanning has significant defects: the track diameter increases with time but the number of sampling points per circle remains unchanged, resulting in a "central dense and edge sparse" distribution characteristic. This characteristic causes two major problems: first, the central region is prone to photodamage due to high-density repeated sampling, which is particularly serious in high-repetition-rate sampling scenarios such as multi-photon fluorescence lifetime imaging; second, the sampling density at the edge region is insufficient, leading to uneven image resolution and affecting the imaging quality.

[0004] To solve the above problems, the existing technology mainly adopts three types of schemes:

[0005] Change the scanning method: such as grid scanning, Lissajous scanning, etc., but it needs to change the system device (such as multi-core optical fiber, galvanometer), which is easy to introduce new problems (such as multi-core optical fiber core number limits resolution, Lissajous trajectory and circular field of view mismatch leading to resource waste), and is difficult to substantially improve the system performance.

[0006] Optimize the spiral scanning parameters: such as hybrid spiral scanning, constant linear velocity spiral scanning, etc., which can improve the uniformity of resolution, but still based on the traditional spiral principle, the sampling in the central region is still dense, and cannot fundamentally reduce the risk of photodamage; some schemes (such as double spiral scanning) even exacerbate the sampling density in the center.

[0007] Image post-processing algorithm: improve image quality through deep learning algorithm, but may introduce pseudo-structure to reduce credibility, and has high computational resource consumption and poor interpretability, which is difficult to deploy in real time in small systems.

[0008] Therefore, there is an urgent need for a multi-photon endoscopic imaging technology scheme that can fundamentally reduce central photodamage and improve resolution uniformity without complex post-processing. SUMMARY

[0009] In view of the defects of the prior art, the present application provides a multi-photon fiber array endoscopic imaging device and method based on hollow spiral scanning, so as to realize low light damage, high resolution uniformity and complete field of view imaging.

[0010] To achieve the above-mentioned purpose, the present application provides a multi-photon fiber array endoscopic imaging device based on hollow spiral scanning, comprising:

[0011] A laser collimation and beam expansion module is arranged to collimate and expand the femtosecond pulsed laser emitted by the laser.

[0012] A pulse chirp module is connected to the laser collimation and beam expansion module and is arranged to pre-compensate the pulse broadening of the optical pulse after transmission through the optical fiber.

[0013] A beam switching module is connected to the pulse chirp module and comprises an optical switch and an optical fiber array, wherein the optical fiber array comprises at least two low group velocity dispersion single-mode optical fibers, and the optical switch is arranged to selectively couple the laser after pulse chirp compensation to a target optical fiber in the optical fiber array.

[0014] An endoscopic detection module is connected to the beam switching module and comprises a resonant driver, a packaging shell and a micro-lens, wherein the resonant driver is arranged to drive one end of the optical fiber array to generate scanning motion, the packaging shell seals the end of the optical fiber array, the resonant driver and the micro-lens, and the micro-lens is arranged to converge the excitation light to the sample and couple the multi-photon signal of the sample to the optical fiber array.

[0015] A fluorescence acquisition module is connected to the beam switching module and the endoscopic detection module and is arranged to acquire the multi-photon signal transmitted by the optical fiber array, perform image reconstruction and fusion processing, and obtain the imaging result of the complete field of view.

[0016] Preferably, the resonant driver drives the optical fiber array to perform a hollow spiral scanning trajectory, and the starting point of the hollow spiral scanning trajectory is not located at the origin of the scanning field of view.

[0017] Preferably, the laser collimation and beam expansion module comprises a laser, a first lens and a second lens, wherein the first lens and the second lens are arranged in sequence in the light path of the laser and are arranged to collimate and expand the spatial light emitted by the laser.

[0018] Preferably, the pulse chirp module comprises a beam splitter, a prism pair and a mirror, wherein the prism pair comprises a first prism and a second prism and is arranged to cooperate with the mirror to compress the laser pulse and compensate the broadening of the optical pulse after transmission through the optical fiber.

[0019] Preferably, the light beam switching module further comprises a second mirror, a fiber coupler and a low group velocity dispersion fiber, the second mirror is used to reflect the compressed laser to the fluorescence acquisition module, the fiber coupler is used to couple the spatial light to the low group velocity dispersion fiber, one end of the low group velocity dispersion fiber is connected to the fiber coupler, and the other end is connected to the input port of the optical switch.

[0020] Preferably, the fluorescence acquisition module comprises a dichroic mirror, a band-pass filter set, a lens set, a photomultiplier tube set, a time-correlated single photon counter and a computer; the dichroic mirror comprises a first dichroic mirror and a second dichroic mirror, which are used to separate the fluorescence signal and the second harmonic signal respectively; the band-pass filter set comprises a first band-pass filter and a second band-pass filter, which are used to filter signals of specific wave bands respectively; the lens set comprises a third lens and a fourth lens, which are used to focus signals respectively; the photomultiplier tube set comprises a first photomultiplier tube and a second photomultiplier tube, which are used to collect fluorescence signals and second harmonic signals respectively; the time-correlated single photon counter is used to collect fluorescence lifetime signals; and the computer is used to control image reconstruction and fusion processing.

[0021] Among them, the third mirror is arranged in the light path of the second harmonic signal, and is used to fold the second harmonic signal to the second band-pass filter and the fourth lens.

[0022] The application also provides a multi-photon fiber array endoscopic imaging method based on hollow spiral scanning, comprising the following steps:

[0023] S1, providing a fiber array, the fiber array comprising at least two low group velocity dispersion single-mode optical fibers, one end of the fiber array being driven by a resonant driver;

[0024] S2, controlling a laser to emit femtosecond pulse laser, after collimation and beam expansion and pulse chirp compensation, selectively coupling the femtosecond pulse laser to a target optical fiber in the fiber array through a light beam switching module;

[0025] S3, driving one end of the fiber array by the resonant driver to make the target optical fiber perform a hollow spiral scanning trajectory, the starting point of the hollow spiral scanning trajectory not being located at the origin of the scanning field of view;

[0026] S4, collecting multi-photon signals of a sample through the fiber array, the multi-photon signals comprising fluorescence signals and / or second harmonic signals;

[0027] S5, switching the light beam switching module to other optical fibers in the fiber array, and repeating steps S2-S4 to make the other optical fibers respectively perform hollow spiral scanning trajectories that do not coincide in space with the target optical fiber;

[0028] S6, performing image reconstruction on the multi-photon signals collected by each optical fiber to obtain a plurality of sub-images;

[0029] S7, fusing the plurality of sub-images to complete the central hollow area of each hollow spiral scanning track, and obtaining an imaging result of a complete field of view.

[0030] Preferably, in step S3, the function of the hollow spiral scanning track is:

[0031] ;

[0032] wherein, is the radius of the current point to the origin, is the angle, is the initial radius and , is the radial growth coefficient, the initial radius is in the range of 0.1mm to 2mm.

[0033] Preferably, in step S4, the multi-photon signal further includes a fluorescence lifetime signal, the fluorescence lifetime signal is collected by a time-correlated single photon counter, and the laser provides a synchronization signal for the fluorescence lifetime signal collection.

[0034] Preferably, the resonant frequency of the resonant driver is satisfies:

[0035] ;

[0036] wherein, is the cantilever length, is the material Young's modulus, is the cross-sectional moment of inertia, is the material density, is the cross-sectional area.

[0037] Therefore, the application adopts the above-mentioned structure of a kind of multi-photon fiber array endoscopic imaging device and method based on hollow spiral scanning, with the following beneficial effects:

[0038] (1) reduce the risk of photo damage: the present application avoids central area dense sampling by designing hollow spiral scanning track (initial radius a ≠ 0), significantly reduces central light accumulation, especially suitable for photosensitive samples and long time imaging scene;

[0039] (2) improve resolution uniformity: the present application performs complementary hollow spiral track in the fiber array of multiple optical fibers, completes the central hollow through image fusion, solves the problem of sparse edge sampling, and realizes uniform sampling of full field of view;

[0040] (3) reliable image: all pixels of the fusion image of the present application are derived from physical scanning sampling, avoiding the introduction of pseudo-structure by post-processing algorithm, improving the result reliability and clinical applicability;

[0041] (4) High system stability: the application adopts optical switch to switch optical fiber channel, simplifies the complex control of multi-core optical fiber, avoids inter-core crosstalk, and improves system reliability;

[0042] (5) Multi-modal imaging capability: the application synchronously collects fluorescence intensity, fluorescence lifetime and second harmonic signal, enriches the imaging information dimension, and meets the diversified biological imaging requirements.

[0043] The technical solutions of the application will be further described in detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 It is a structural schematic diagram of a multi-photon optical fiber array endoscopic imaging device based on the application;

[0045] Figure 2 It is a schematic diagram of the sampling point distribution of the hollow spiral scanning of the double-core optical fiber array; (a) and (c) are the sampling point distribution of the three groups of hollow spiral tracks of optical fiber one, (d) is the sampling point distribution of the hollow spiral track of optical fiber two, (e) is the fused sampling point distribution, and (f) is the sampling point distribution of the traditional solid spiral scanning;

[0046] REFERENCE NUMERALS

[0047] 1-laser, 2-first lens, 3-second lens, 4-split mirror, 5-first prism, 6-second prism, 7-mirror one, 8-mirror two, 9-dichroic mirror one, 10-fiber coupler, 11-low group velocity dispersion optical fiber, 12-optical switch, 13-optical fiber array, 14-resonant driver, 15-encapsulation shell, 16-micro objective, 17-sample, 18-dichroic mirror two, 19-band pass filter one, 20-third lens, 21-first photomultiplier tube, 22-mirror three, 23-band pass filter two, 24-fourth lens, 25-second photomultiplier tube, 26-controller, 27-acquisition card, 28-time correlation single photon counter, 29-computer. DETAILED DESCRIPTION

[0048] The technical solutions of the application will be further described in detail below with reference to the drawings and examples.

[0049] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the ordinary meanings as understood by one of ordinary skill in the art to which this application pertains. The terms "first", "second", and similar terms do not denote any order, quantity, or importance, but are used to distinguish one element from another, and the terms "comprises", "comprising", "includes", "including" and the like can be used synonymously with "containing" or "containing at least". The terms "connected", "coupled", and the like, can be used synonymously with "connected" or "coupled", and can include electrically connected, either directly or indirectly. The terms "upper", "lower", "left", "right", and the like, are used to denote relative positions only, and can change accordingly when the absolute positions of the described objects change.

[0050] Embodiment

[0051] As shown in Figure 1 The present application provides a multi-photon fiber array endoscopic imaging device based on hollow spiral scanning, specifically as follows:

[0052] Laser collimation and beam expansion module: femtosecond pulsed laser (central wavelength 800 nm, repetition frequency 80 MHz) is emitted by laser 1, collimated and expanded by first lens 2 (focal length 10 mm) and second lens 3 (focal length 20 mm), and the laser spot diameter is expanded to 5 mm;

[0053] Pulse chirp module: the laser is split into two beams by beam splitter 4, one of which is reflected by mirror 7 after passing through a prism pair composed of first prism 5 and second prism 6 (material SF11), achieving pulse compression (compensating for the pulse broadening caused by fiber transmission, so that the pulse width is compressed to 100 fs);

[0054] Beam switching module: the compressed laser is folded by mirror 2 8 to dichroic mirror 1 9 (transmits 800 nm excitation light and reflects 500-600 nm fluorescence), coupled to low group velocity dispersion fiber 1 1 (length 2 m, dispersion coefficient <1 ps / (nm·km)) by fiber coupler 1 0 (coupling efficiency >85%) and transmitted to optical switch 1 2 (1×4 port, switching time <1 ms); fiber array 1 3 is composed of 4 low group velocity dispersion single mode fibers, arranged in a square, with a dense end spacing of 50 μm, and the other end is connected to the 4 output ports of optical switch 1 2 respectively;

[0055] Endoscope detection module: the dense end of the fiber array 13 is driven by a resonant driver 14 (piezoelectric ceramic resonant driver), and a waterproof and insulated seal is achieved by a packaging shell 15 (material 304 stainless steel); a micro-lens 16 (numerical aperture 0.5, focal length 1.8 mm) converges the excitation light to the sample 17 and couples the fluorescence signal back to the fiber array 13; the resonant frequency of the resonant driver 14 is:

[0056] ;

[0057] wherein the cantilever length , the material Young's modulus , the cross-sectional moment of inertia , the material density , the cross-sectional area , the calculated frequency is .

[0058] Fluorescence acquisition module: a dichroic mirror 18 (reflecting 500-600 nm fluorescence and transmitting 800 nm second harmonic) separates the signals; the fluorescence signal is focused to a first photomultiplier tube 21 (model H10722-01) by a band-pass filter 1 9 (center wavelength 550 nm, bandwidth 50 nm) and a third lens 20 (focal length 25 mm); the second harmonic signal is folded by a mirror 22, and is focused to a second photomultiplier tube 25 (model H10722-01) by a band-pass filter 2 3 (center wavelength 400 nm, bandwidth 20 nm) and a fourth lens 24 (focal length 25 mm); a time-correlated single photon counter 28 (model PicoHarp300) acquires the fluorescence lifetime signal; a computer 29 drives the resonant driver 14 through a capture card 27 (model NIPCIe-6363) and a controller 26, and runs an image fusion algorithm.

[0059] Imaging process

[0060] Taking a double-core fiber array (fiber 1 and fiber 2) as an example, the imaging process is as follows:

[0061] The femtosecond laser emitted by the laser 1 is collimated and expanded, and the pulse chirp is compensated, then transmitted to the optical switch 12 through the fiber coupler 10 and the low group velocity dispersion fiber 1;

[0062] The optical switch 12 turns on the fiber 1 channel, and the laser is coupled to the fiber 1; the resonant driver 14 drives the fiber array 13 to make the fiber 1 perform a hollow spiral trajectory: ,( , ), the capture card 27 and the time-correlated single photon counter 28 work synchronously to obtain the sub-image of the sampling point distribution shown in (a) of Figure 2 ;

[0063] Adjust the scanning parameters to The optical fiber was scanned again to obtain... Figure 2 The sub-image shown in (b) is shown in the image.

[0064] Adjust the scan parameters to The fiber optic cable was scanned a third time to obtain... Figure 2 The sub-image shown in (c) is shown in the image.

[0065] Optical switch 12 switches to fiber optic channel 2, fiber optic channel 2 execution trajectory Scan to obtain Figure 2 The sub-image shown in (d) is shown in the image.

[0066] 29 pairs of computers Figure 2 (a) in Figure 2 The sub-images of (d) are fused: through spatial registration (based on sample feature point matching), bilinear interpolation is used to fill in the central holes to generate... Figure 2 The complete image shown in (e) is compared. Figure 2 Compared with the traditional solid spiral scanning result in (f), the present invention has no central dense sampling and the overall sampling is more uniform.

[0067] In summary, this invention is applicable to multiphoton fluorescence and fluorescence lifetime imaging systems. This method significantly reduces laser light damage in the central region of traditional spiral scanning trajectories by designing a hollow spiral scanning trajectory; and by employing multiple fibers in an fiber array to perform hollow spiral scanning with non-overlapping trajectories or sampling points, the resulting multiple reconstructed images are fused to achieve full-field multiphoton fluorescence and fluorescence lifetime imaging, while effectively improving the overall resolution uniformity of the imaging image.

[0068] This invention employs an optical switch as a switching device for the excitation beam, achieving efficient coupling between the excitation light and different optical fibers in the fiber array. Based on the hollow spiral scanning method described above, the system can achieve low-optical-damage imaging of samples. The image data acquired by each fiber in the fiber array is processed by reconstruction and fusion algorithms to obtain a complete field-of-view endoscopic imaging result. All pixels in the imaging result originate from physical sampling of the actual spiral scan, ensuring the authenticity and reliability of the image.

[0069] 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-photon fiber array endoscopic imaging device based on a hollow helical scan, characterized by, The application relates to a laser scanning endoscope system. The laser collimation and beam expansion module is used for collimating and expanding femtosecond pulse laser emitted by a laser; The pulse chirp module is connected with the laser collimation and beam expansion module and is used for pre-compensating pulse broadening of the optical pulse after fiber transmission; The beam switching module is connected with the pulse chirp module and comprises an optical switch and a fiber array, the fiber array comprises at least two low group velocity dispersion single-mode optical fibers, and the optical switch is used for selectively coupling the laser after pulse chirp compensation to a target optical fiber in the fiber array; The endoscopic detection module is connected with the beam switching module and comprises a resonant driver, a packaging shell and a micro-lens, the resonant driver is used for driving one end of the fiber array to generate scanning motion, the packaging shell seals the end of the fiber array, the resonant driver and the micro-lens, and the micro-lens is used for converging excitation light to a sample and coupling multi-photon signals of the sample to the fiber array; The fluorescence acquisition module is connected with the beam switching module and the endoscopic detection module and is used for acquiring the multi-photon signals transmitted by the fiber array, performing image reconstruction and fusion processing and obtaining imaging results of a complete field of view; The resonant driver drives the fiber array to perform a hollow spiral scanning track, and the starting point of the hollow spiral scanning track is not located at the origin of the scanning field of view; The pulse chirp module comprises a beam splitter, a prism pair and a mirror, the prism pair is composed of a first prism and a second prism, is used for cooperating with the mirror to compress the laser pulse and compensate the broadening of the optical pulse after fiber transmission; The fluorescence acquisition module comprises a dichroic mirror, a band-pass filter set, a lens set, a photomultiplier tube set, a time-correlated single photon counter and a computer; the dichroic mirror comprises a dichroic mirror one and a dichroic mirror two and is used for separating the fluorescence signal and the second harmonic signal; the band-pass filter set comprises a band-pass filter one and a band-pass filter two and is used for filtering signals of specific wave bands; the lens set comprises a third lens and a fourth lens and is used for focusing signals; the photomultiplier tube set comprises a first photomultiplier tube and a second photomultiplier tube and is used for acquiring the fluorescence signal and the second harmonic signal; the time-correlated single photon counter is used for acquiring the fluorescence lifetime signal; and the computer is used for controlling image reconstruction and fusion processing. The mirror three is arranged in the light path of the second harmonic signal and is used for folding the second harmonic signal to the band-pass filter two and the fourth lens.

2. The multi-photon fiber array endoscopic imaging device based on hollow helical scanning according to claim 1, wherein: The laser collimation and beam expansion module comprises a laser, a first lens and a second lens, the first lens and the second lens are sequentially arranged in the light path of the laser and are used for collimating and expanding the spatial light emitted by the laser. 3.The multi-photon fiber array endoscopic imaging device based on a hollow helical scanning according to claim 1, wherein: The beam switching module further comprises a mirror two, a fiber coupler and a low group velocity dispersion optical fiber, the mirror two is used for reflecting the compressed laser to the fluorescence acquisition module, the fiber coupler is used for coupling the spatial light to the low group velocity dispersion optical fiber, one end of the low group velocity dispersion optical fiber is connected with the fiber coupler, and the other end is connected with the input port of the optical switch.

4. The multi-photon fiber array endoscopic imaging device based on hollow helical scanning according to claim 1, wherein: Resonant frequency of the resonant driver f satisfies: ； wherein, is the cantilever length, is the material Young's modulus, is the cross-sectional moment of inertia, is the material density, is the cross-sectional area.

5. A method for hollow-core helical scanning based multi-photon fiber array endoscopic imaging, applied to the hollow-core helical scanning based multi-photon fiber array endoscopic imaging device of any one of claims 1-4, characterized in that, The application further discloses a laser scanning endoscope system and a laser scanning endoscope method. S1, providing a fiber array, the fiber array comprises at least two low group velocity dispersion single-mode optical fibers, and one end of the fiber array is driven by a resonant driver; S2, controlling a laser to emit femtosecond pulse laser, after collimation and beam expansion and pulse chirp compensation, selectively coupling the laser to a target optical fiber in the fiber array through the beam switching module; S3, driving one end of the fiber array by the resonant driver to make the target fiber perform a hollow spiral scanning trajectory, and a starting point of the hollow spiral scanning trajectory is not located at an origin of a scanning field of view; S4, collecting a multiphoton signal of the sample by the fiber array, the multiphoton signal including a fluorescence signal and / or a second harmonic signal; S5, switching the beam switching module to other fibers in the fiber array, and repeating steps S2-S4 to make the other fibers respectively perform hollow spiral scanning trajectories that are not spatially coincident with the target fiber; S6, performing image reconstruction on the multiphoton signals collected by each fiber to obtain a plurality of sub-images; S7, performing fusion processing on the plurality of sub-images to complete a central hollow region of each hollow spiral scanning trajectory, and obtaining an imaging result of a complete field of view.

6. The method of claim 5, wherein the method is a multi-photon fiber array endoscopic imaging method based on a hollow helical scanning. In step S3, a function of the hollow spiral scanning trajectory is: ； wherein, is the current point to the origin of the radius, is the angle, is the initial radius and , is the radial growth coefficient, the initial radius is in the range of 0.1 mm to 2 mm.

7. The method of claim 5, wherein the method is a multi-photon fiber array endoscopic imaging method based on a hollow helical scanning. In step S4, the multiphoton signal further includes a fluorescence lifetime signal, the fluorescence lifetime signal is collected by a time-correlated single photon counter, and a laser provides a synchronization signal for the fluorescence lifetime signal collection.

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