A three-dimensional micro-endoscope

Abstract

The present invention relates to the technical field of endoscopes, and particularly to a three-dimensional micro endoscope, which includes a micro imaging probe. The micro imaging probe includes an objective lens that can face an external sample directly. A front aperture for collecting fluorescent photons generated by the external sample is formed on the objective lens. The objective lens is connected to a photodetector for collecting fluorescent photons that cannot be collected by the front aperture. The photodetector includes a filter, a photosensitive unit, and a driving unit that are connected to each other in sequence. At the same time, it also includes a planar dichroic mirror and a vertical dichroic mirror. The present invention reasonably uses a photodetector to replace additional optical elements in the prior art, reduces the volume of the endoscope on the premise of ensuring the efficiency of the endoscope in collecting fluorescent photons, solves the problem that the large volume of the endoscope in the prior art affects the use of the endoscope, and at the same time realizes three-dimensional scanning of the endoscope by using a planar dichroic mirror scanner and a vertical dichroic mirror scanner.

Description

Technical Field

[0001] The present invention relates to the technical field of endoscopes, and particularly to a three-dimensional micro-endoscope. Background Art

[0002] With the development of science and technology, medical endoscopes have been widely used in the medical field. It is one of the important tools for humans to observe and treat internal organs. During the development of endoscopes over more than 200 years, the structure has undergone four major improvements. From the initial rigid endoscope, semi-flexible endoscope to fiber endoscope, and then to today's electronic endoscope, the image quality has also achieved a qualitative leap time and time again. Nowadays, with LED lighting, endoscopes can obtain color photos or color TV images. At the same time, the images are no longer ordinary images of tissues and organs, but microscopic images observed under a microscope, and minute lesions can be clearly distinguished. According to existing clinical experience, the smaller the volume of the micro-imaging probe of the endoscope and the shorter the rigid section, the greater the reduction of the patient's pain. Therefore, endoscopes have been continuously developing towards miniaturization.

[0003] Existing endoscopes generally include an objective lens, a scanning lens, a focusing lens, a cylindrical lens, a wave plate, and a collecting lens, etc. The objective lens is used to converge the laser from the microelectromechanical scanner into the interior of the living sample to excite the living sample to generate a fluorescence signal and to output the fluorescence signal; the scanning lens is arranged on the optical path between the microelectromechanical scanner and the objective lens and is used to convert the laser with an angular change generated by the two-dimensional scanning of the microelectromechanical scanner into a laser with a position change; the focusing lens is used for laser focusing; the cylindrical lens is used to form a linear focus; the wave plate is used to change the polarization direction of the laser; the collecting lens is used to collect the nonlinear optical signal and input it into the laser output optical fiber.

[0004] For non-linear optical imaging microscopes, especially multi-photon fluorescence microscopes, near-infrared laser pulses are focused by the objective lens to excite isotropically emitted fluorescence signals in the sample. Biological tissues usually exhibit strong absorption and high scattering optical properties. For epi-fluorescence detection, the same objective lens is used both for focusing the excitation light and for collecting the fluorescence signal. The intensity of the fluorescence signal collected by the objective lens depends on the numerical aperture of the objective lens and the front aperture of the objective lens. The larger the numerical aperture and the front aperture of the objective lens, the greater the intensity of the fluorescence signal that the objective lens can collect.

[0005] In recent years, many technologies have emerged to collect fluorescence photons that cannot be collected by an objective lens. For example, a catadioptric objective lens was proposed in 2006; in 2007, an emission detection technology using a parabolic mirror and in 2011, an emission detection technology using a cylindrical mirror were proposed, and a 10-fold enhancement in fluorescence collection efficiency was obtained through simulation and an 8.9-fold enhancement in fluorescence collection efficiency was obtained through experiments. In addition, by arranging 5-8 high numerical aperture optical fibers around the objective lens to collect the fluorescence that cannot be collected by the objective lens, a 2-fold enhancement in fluorescence collection efficiency can be obtained for a high numerical aperture objective lens and a 20-fold enhancement in fluorescence collection efficiency can be obtained for a low numerical aperture objective lens.

[0006] All of the above technologies for enhancing fluorescence collection efficiency use additional optical elements to collect the fluorescence photons that cannot be collected by the objective lens. Since the scattering angles and discreteness of fluorescence photons are very large, the fluorescence photons have a complex multiple reflection path and high loss after entering the additional collection optical path, resulting in limited actual collection efficiency of the additional optical elements. In order to ensure the collection efficiency of fluorescence photons, it is necessary to increase the volume of the additional optical elements for enhancing fluorescence collection efficiency, which poses a serious technical obstacle to the development trend of the endoscope towards miniaturization. Therefore, how to reduce the volume of the endoscope while ensuring the fluorescence photon collection efficiency of the endoscope has become an urgent problem to be solved. Summary of the Invention

[0007] To solve the above problems, the present invention provides a three-dimensional micro-endoscope, which solves the problem that the large volume of the endoscope hinders the use of the endoscope while ensuring the fluorescence photon collection efficiency of the endoscope.

[0008] To achieve the above object, the technical solution adopted by the present invention is: a three-dimensional micro-endoscope, including a micro-imaging probe. The micro-imaging probe includes an objective lens that can face an external sample directly. A front aperture for collecting fluorescence photons generated by the external sample is formed on the objective lens. The objective lens is connected to a photodetector for collecting the fluorescence photons that cannot be collected by the front aperture. The photodetector includes a filter, a photosensitive unit, and a driving unit that are connected to each other in sequence. The filter and the objective lens can face the external sample simultaneously. The filter is used to filter out the fluorescence photons of backscattering and backscattering. The electrically sensitive unit is used to convert the fluorescence photons passing through the filter into electrical signals. The driving unit is used to provide a high voltage and a driving signal to the photosensitive unit and is connected to an external amplifier circuit and a computer.

[0009] The principle of the present invention is as follows: The near-infrared laser pulse is focused by the objective lens to excite a fluorescence signal (i.e., fluorescence photons) with isotropic emission in the sample. Due to the large discreteness of the scattering angles of the fluorescence photons, only part of the fluorescence photons can be collected by the front aperture provided on the objective lens. The fluorescence photons that fail to enter the front aperture are directed towards the photodetector. The filter in the photodetector is used to filter out the backward-reflected and backward-scattered excitation light. Then, the photosensitive unit senses the fluorescence photons filtered by the filter and converts the received fluorescence light signal into an electrical signal. The driving unit is used to provide a high voltage and a driving signal to the photosensitive unit, prompting the photosensitive unit to convert the received fluorescence photon signal into an electrical signal. At the same time, the driving unit is connected to an external amplifier circuit and a computer, and transmits the electrical signal generated by the photosensitive unit to the external amplifier circuit and the computer. Thus, the fluorescence photons that cannot be collected by the front aperture can be detected by the external circuit and the computer through the photodetector, enabling as many fluorescence photons as possible to be collected, thereby increasing the imaging clarity of the endoscope.

[0010] Since a photodetector is used in this application to replace the traditional additional optical elements for collecting fluorescence photons, and the filter, photosensitive unit, and driving unit for collecting the fluorescence photon signal are integrated in the photodetector, the volume of the photodetector is greatly reduced compared to the traditional additional optical elements, resulting in a reduction in the overall volume of the component for enhancing the collection of fluorescence photons, avoiding the occlusion of the imaging area by the component for enhancing the collection of fluorescence photons (the photodetector in this application), thereby enabling a larger operating space for electrophysiological experiments and achieving the accurate and smooth progress of electrophysiological experiments. Moreover, due to the reduction in the volume of the photodetector, it is possible to further reduce the volume of the entire endoscope while ensuring the fluorescence photon collection efficiency, well solving the contradiction between the fluorescence photon collection efficiency and the volume in the current endoscope, and thus improving the endoscope significantly.

[0011] The advantages of adopting the above solution are:

[0012] 1. The endoscope is small in size: Compared with the prior art where additional optical elements are required to collect fluorescence photons that cannot be collected by the front aperture, the optical path of the additional optical elements is complex, resulting in a relatively large volume of the additional optical elements. This makes it impossible to solve the contradiction between the fluorescence photon collection efficiency and the volume of the endoscope. The outer diameter of commercial endoscopes in the prior art is generally 9 - 11 mm. In this application, a photodetector is used to replace the additional optical elements, changing the principle of collecting fluorescence photons by the traditional additional optical elements. This enables the fluorescence photons to be collected by the photodetector and form an electrical signal, simplifies the optical path, and reduces the overall volume of the endoscope. After the improvement of this application, the volume of the endoscope can be reduced to 5×5×5 mm, and its fluorescence photon collection efficiency is relatively high. Therefore, it well solves the problem in the prior art of how to balance the volume of the endoscope and ensure the fluorescence photon collection efficiency, reducing the volume of the endoscope while ensuring the fluorescence photon collection efficiency is guaranteed.

[0013] 2. High efficiency in collecting fluorescence photons: Compared with the prior art where additional optical elements are used to collect fluorescence photons that cannot be collected by the front aperture, the optical path of the additional optical elements is complex. Moreover, the scattering angle and discreteness of fluorescence photons are very large. When the fluorescence photons are collected by the additional optical elements, some fluorescence photons fail to be collected during the propagation of the additional optical elements. In this application, when the photodetector is used to collect fluorescence photons, the fluorescence photons entering the filter are immediately detected by the photosensitive unit and generate an electrical signal. The propagation distance of the fluorescence photons is small, which can reduce unnecessary losses of the fluorescence photons, thereby improving the collection efficiency of the fluorescence photons.

[0014] Further, the number of photodetectors is several, and several photodetectors are evenly distributed in the circumferential direction of the front aperture.

[0015] Compared with the prior art where additional optical elements are used to collect fluorescence photons that cannot be collected by the front aperture, due to the large scattering angle and discreteness of the fluorescence photons, and the limited collection of fluorescence photons by the front aperture, the fluorescence photons outside the periphery of the front aperture cannot be collected. Due to the optical path propagation characteristics of the existing additional optical elements, additional optical elements are required to guide the fluorescence photons, and the additional optical elements cannot be distributed in the circumferential direction of the front aperture (because if they are distributed in the circumferential direction of the front aperture, the optical paths of the individual additional optical elements will interfere with each other, resulting in a reduction in the fluorescence photon collection efficiency). In this solution, since the volume of the photodetector is small, and the fluorescence photons entering the photodetector are directly sensed by the photosensitive unit and form an electrical signal, its optical path is simple and there is no need for additional guidance using optical elements. Thus, multiple photodetectors can be arranged in the circumferential direction of the front aperture, improving the efficiency of the endoscope in collecting fluorescence photons and enhancing the imaging effect of the endoscope.

[0016] Furthermore, it also includes a planar dichroic mirror scanner for separating the laser and the nonlinear optical signal and outputting the nonlinear optical signal, and also for changing the incident angle of the laser to perform two-dimensional point scanning on the plane of the internal tissue of an external sample; a vertical dichroic mirror scanner for performing distal Z-axis scanning to achieve three-dimensional imaging.

[0017] The planar dichroic mirror scanner is used to complete two-dimensional scanning of the plane of the internal tissue of an external sample, and at the same time, the vertical dichroic mirror scanner is used to complete the scanning of the distal Z-axis. By combining the planar dichroic mirror scanner and the vertical dichroic mirror scanner, three-dimensional scanning of the external sample is completed.

[0018] Furthermore, it also includes a collimating lens for collimating the laser output from the laser input fiber, reducing the chromatic aberration between lasers of different frequencies, and outputting a laser signal.

[0019] The collimating lens receives the polarized laser and collimates the polarized laser into parallel light (collimation process), and reduces the chromatic aberration between lasers of different frequencies (achromatic aberration process), so that the laser input to the planar dichroic mirror has better optical performance.

[0020] Furthermore, the planar dichroic mirror scanner includes a dichroic mirror and a microelectromechanical driver for driving the dichroic mirror to change the angle. The dichroic mirror is polarization-sensitive, reflects S-polarized light, and transmits p-polarized light. The dichroic mirror is fixedly connected to the microelectromechanical driver, and the planar dichroic mirror scanner is located at the rear focal plane of the objective lens.

[0021] In this solution, the S-type linearly polarized laser is output from the laser input fiber to the collimating lens. The S-type linearly polarized laser is reflected and focused into a line in a certain direction (X direction) on the surface of the planar dichroic mirror scanner through the cylindrical lens. The planar dichroic mirror scanner reflects the S-type linearly polarized laser, and then the focusing lens collimates the S-type linearly polarized laser in the X direction and focuses it into a line in another direction (Y direction) perpendicular to the X direction. The S-type linearly polarized laser continues to pass through the glass slide, and the polarization direction of the S-type linear polarization rotates by 45 degrees. Then the laser is focused on the surface of the vertical dichroic mirror scanner in the Y direction. The vertical dichroic mirror scanner reflects the laser, and the diverging laser after reflection passes through the glass slide again. The polarization direction of the laser rotates by 45 degrees in the same direction again and becomes a P-type linearly polarized light. It passes through the focusing lens again to become a beam focused in the X direction and collimated in the Y direction and is projected on the surface of the planar dichroic mirror scanner. The planar dichroic mirror scanner transmits the P-type linearly polarized laser of the same wavelength. The dichroic mirror scanner is located in the rear focal plane of the objective lens. The movable mirror in the planar dichroic mirror scanner rotates along the rotation axis parallel to the X axis. Finally, the P-type linearly polarized light forms a linear focus that is collimated in the X direction and focused in the Y direction inside the sample through the objective lens. The linear focus is scanned in the X direction, thereby forming a two-dimensional scanning trajectory, realizing two-dimensional line scanning of the plane of the internal tissue of the external sample by the laser.

[0022] Furthermore, the vertical dichroic mirror scanner has the same structure as the planar dichroic mirror scanner, and the vertical dichroic mirror scanner is located in the rear focal plane of the cylindrical lens.

[0023] The structure of the vertical dichroic mirror scanner is the same as that of the planar dichroic mirror scanner, except that the vertical dichroic mirror scanner is located in the rear focal plane of the cylindrical lens. When the dichroic mirror scanner completes a frame of two-dimensional line scan image, the movable dichroic mirror on the vertical dichroic mirror scanner moves a distance along the optical axis (Z direction). Through the principle of remote scanning (see Botcherby EJ, Smith CW, Kohl MM, et al. Aberration-free three-dimensional multiphoton imaging of neuronal activity at kHz rates. Proceedings of the National Academy of Sciences of the United States of America. 2012; 109(8): 2919-2924. doi: 10.1073 / pnas.1111662109.), the two-dimensional line scan plane of the internal tissue of the external sample also moves a distance along the optical axis, and three-dimensional line scanning is realized through the scanning of the vertical dichroic mirror scanner in the Z direction.

[0024] When using an endoscope, since it is not possible to inject fluorescent dyes into patients during clinical use, only three label-free signal methods, namely two-photon excited autofluorescence, second harmonic generation, and coherent anti-Stokes Raman scattering, can be applied clinically. For the above three label-free signal imaging methods, this solution can be achieved by changing the wavelength of the laser in the laser input optical fiber and configuring dichroic mirror scanners with different parameters. Moreover, since this solution does not have a scanning lens and a tube lens, the overall volume of the micro-optical probe can be effectively reduced to achieve the purpose of reducing the volume of the endoscope. Also, in this solution, since the wavelengths of the laser signal input by the laser input optical fiber and the nonlinear optical signal received by the focusing lens are different (i.e., there are several different wavelengths), the achromatic effect of the collimating lens itself can be used to meet the basic imaging requirements.

[0025] Further, a reflecting mirror is provided on the optical path between the collimating lens and the planar dichroic mirror scanner.

[0026] The reflecting mirror is arranged on the optical path between the collimating lens and the planar dichroic mirror scanner and is used to adjust the angle of the laser output by the collimating lens and reflect it to the planar dichroic mirror scanner, so that the planar dichroic mirror scanner can obtain lasers with different incident angles for easy imaging.

[0027] Further, the reflecting mirror includes a transmission surface and a reflection surface. The transmission surface is provided with a transmission coating layer for enhancing the transmittance, and the reflection surface is provided with a reflection coating layer for enhancing the reflectivity.

[0028] Setting a transmission coating layer for enhancing the transmittance and a reflection coating layer for enhancing the reflectivity on the reflecting mirror is beneficial to enhancing the transmittance and reflectivity of the reflecting mirror, so that the reflecting mirror can achieve a better reflection effect.

[0029] Further, the number of reflecting mirrors is multiple.

[0030] Since the volume of the endoscope is generally small, and the laser input optical fiber and the laser output optical fiber need to minimize the installation volume as much as possible, and their positions are very close, multiple reflecting mirrors are provided inside the endoscope to adjust the optical path.

[0031] Further, the objective lens, the photodetector, the planar dichroic mirror scanner, the vertical dichroic mirror scanner, the cylindrical lens, the collimating lens, and the reflecting mirror are all wrapped with a housing.

[0032] Using the housing to wrap all components separates the internal components of the endoscope from the external sample, avoiding the influence of the external sample on the operation of the endoscope during detection. Description of the Drawings

[0033] Figure 1This is the schematic diagram of a three-dimensional microendoscope in Embodiment 1 of the present invention.

[0034] Figure 2 This is the schematic diagram of a three-dimensional microendoscope in Embodiment 1 of the present invention.

[0035] Figure 3 This is the schematic diagram of the three-dimensional scanning of a three-dimensional microendoscope in Embodiment 1 of the present invention.

[0036] Figure 4 This is the schematic diagram of the photodetector of a three-dimensional microendoscope in Embodiment 1 of the present invention.

[0037] Figure 5 This is the cooperation diagram of the objective lens and the photodetector of a three-dimensional microendoscope in Embodiment 1 of the present invention.

[0038] Figure 6 This is the cooperation diagram of the objective lens and the photodetector of a three-dimensional microendoscope in Embodiment 2 of the present invention. Detailed implementation manners

[0039] The following is a further detailed description through specific implementation manners:

[0040] The reference numerals in the accompanying drawings of the specification include: collimating lens 10, cylindrical lens 12, mirror 20, planar dichroic mirror scanner 30, objective lens 40, focusing lens 50, glass slide 60, vertical dichroic mirror scanner 70, collecting lens 80, laser input optical fiber 90, laser output optical fiber 91, housing 100, substrate 11, driver 22, photodetector 33, filter 331, photosensitive unit 332, and driving unit 333.

[0041] Embodiment 1

[0042] Embodiment 1 is basically as Figure 1 、 Figure 2 and Figure 3 shown. A three-dimensional microendoscope includes a micro imaging probe, which is wrapped by a housing 100. Inside the micro imaging probe, in the order of the optical path, there are: a collimating lens 10, a cylindrical lens 12, a mirror 20, a planar dichroic mirror scanner 30, an objective lens 40, a focusing lens 50, a glass slide 60, a vertical dichroic mirror scanner 70, and a collecting lens 80. The objective lens 40 includes a front aperture for collecting fluorescent photons, and the front aperture is vertically arranged and its lower end passes through the bottom of the housing 100 and can be directly opposite to an external sample.

[0043] The objective lens 40 is an aspherical lens. The collimating lens 10 is used to collimate the laser output from the laser input optical fiber 90, reduce the chromatic aberration between lasers of different frequencies, and output a laser signal to the mirror 20. The objective lens 40 of the aspherical lens has a radius of curvature that varies along the central axis, which is used to improve the optical quality, reduce the number of optical elements, and lower the design cost.

[0044] The cylindrical lens 12 is used to focus the collimated laser into a linear focus in a certain direction (referred to as the X direction here) on the surface of the planar dichroic mirror scanner 30, that is, the focal position of a certain direction (X direction) of the cylindrical lens 12 is on the dichroic mirror surface, and the focal position of the other direction (referred to as the Y direction here) orthogonal to a certain direction (X direction) of the cylindrical lens 12 is not on the dichroic mirror surface.

[0045] The mirror 20 includes a projection surface and a reflection surface, and there are three pieces in number. It is used to translate the optical path. Its material is optical glass or polymer. The projection surface has a transmission coating layer to enhance the transmittance, and the reflection surface has a reflection coating layer to enhance the reflectivity. In this embodiment, the mirror 20 is placed at 45 degrees and is used to reflect the laser (laser signal) by 90 degrees to the planar dichroic mirror scanner 30.

[0046] The planar dichroic mirror scanner 30 is used to separate the laser and the nonlinear optical signal and output the nonlinear optical signal, and is also used to change the incident angle of the laser. The vertical dichroic mirror scanner 70 is used to reflect the laser and transmit the nonlinear optical signal. The planar dichroic mirror scanner 30 includes a dichroic mirror and a microelectromechanical driver for driving the dichroic mirror to rotate. The dichroic mirror is physically connected to the electric driver. The material of the dichroic mirror is optical glass or polymer, and it is used to reflect the s-polarized laser and transmit the p-polarized laser and the nonlinear optical signal. And the planar dichroic mirror scanner 30 is located at the rear focal plane of the objective lens 40; the structure and material of the vertical dichroic mirror scanner 70 are the same as those of the planar dichroic mirror scanner 30, and the vertical dichroic mirror scanner 70 is located at the rear focal plane of the cylindrical lens 12.

[0047] For the schematic diagram of three-dimensional line scanning, see Figure 3, the planar dichroic mirror scanner 30 reflects the s-type linearly polarized laser, and then the focusing lens 50 collimates the s-type linearly polarized laser in the X direction and focuses it into a line in another direction (Y direction) perpendicular to the X direction. The s-type linearly polarized laser continues to pass through the glass slide 60, and the polarization direction of the s-type linear polarization rotates by 45 degrees. Then the laser is focused on the surface of the vertical dichroic mirror scanner 70 in the Y direction. The vertical dichroic mirror scanner 70 reflects the laser, and the reflected and diverging laser passes through the glass slide 60 again. The polarization direction of the laser rotates by 45 degrees in the same direction again and becomes p-type linearly polarized light. It passes through the focusing lens 50 again and becomes a beam focused in the X direction and collimated in the Y direction and is projected onto the surface of the planar dichroic mirror scanner 30. The planar dichroic mirror scanner 30 transmits the p-type linearly polarized laser of the same wavelength. The planar dichroic mirror scanner 30 is located in the rear focal plane of the objective lens 40. The movable mirror in the planar dichroic mirror scanner 30 rotates along the rotation axis parallel to the X axis. Finally, the p-type linearly polarized light forms a linear focus that is collimated in the X direction and focused in the Y direction within the sample through the objective lens 40. The linear focus scans along the X direction, thereby forming a two-dimensional scanning trajectory, realizing two-dimensional line scanning of the laser on the plane of the external sample.

[0048] When the planar dichroic mirror scanner 30 completes a frame of two-dimensional line scan image, the movable dichroic mirror on the vertical dichroic mirror scanner 70 moves a distance along the optical axis (Z direction). Through the principle of remote scanning, the two-dimensional line scan plane of the external sample also moves a distance along the optical axis. Three-dimensional line scanning is realized through the scanning of the vertical dichroic mirror scanner 70 in the Z direction. The non-linear signal excited in the external sample is collected by the objective lens 40, and successively passes through the planar dichroic mirror scanner 30 that transmits the non-linear signal wavelength, the focusing lens 50, the glass slide 60, is linearly focused in the Y direction on the surface of the vertical dichroic mirror scanner 70, the vertical dichroic mirror scanner 70 transmits the non-linear signal wavelength, and then the collection lens 80 linearly focuses the non-linear signal in the X direction on the surface of the laser output optical fiber 91 and finally transmits it to the external photoelectric detection device. Among them, the laser input optical fiber 90 is a large mode field single-mode optical fiber or a polarization-maintaining optical fiber or a photonic crystal optical fiber, and the laser output optical fiber 91 is an optical fiber bundle.

[0049] Due to the linear focus formed by the line scanning method adopted in the present invention, the fluorescence collected by the objective lens 40 is also linear and moves parallel to the end face of the laser output optical fiber 91 as the planar dichroic mirror scanner 30 rotates. Therefore, the detection of the moving linear fluorescence is completed by a scientific complementary metal-oxide-semiconductor (sCMOS) camera with a synchronizable rolling exposure shutter technology. The position of the linear fluorescence is strictly synchronized with a certain row of photoelectric detection units currently read by the rolling shutter of the sCMOS camera, thereby realizing high-speed imaging.

[0050] In addition, in order to improve the efficiency of fluorescent photons and increase the imaging quality of the endoscope, a photodetector 33 is uniformly arranged circumferentially at one end of the front aperture of the objective lens 40 close to the external sample, as Figure 4 shown. The photodetector 33 includes a filter 331, a photosensitive unit 332, and a driving unit 333 arranged in sequence from the lower right to the upper. The filter 331 is used to filter out the backscattered and backscattered fluorescent photons. The photosensitive unit is used to convert the fluorescent photons passing through the filter 331 into electrical signals. The driving unit is used to provide high voltage and driving signals to the photosensitive unit and is connected to an external amplifier circuit and a computer (not shown in the figure).

[0051] In this embodiment, as Figure 5 shown, the photosensitive unit 332 of the photodetector 33 is composed of an annular array of multiple ordinary-sized avalanche diodes. The central hole or transparent material is used to transmit the excitation light of the microscope objective. The multiple ordinary-sized avalanche diodes are used to receive the fluorescent photons that cannot be received by the microscope objective. The photodetector 33 can collect the fluorescent photons that cannot be collected by the front aperture of the objective lens 40, convert the collected fluorescent photon signals into electrical signals, and then transmit them to an external amplifier circuit and a computer, so that the fluorescent photons generated by the external sample can be collected as much as possible, further improving the three-dimensional imaging quality of the endoscope. Compared with using additional optical elements, after using the photodetector 33 in this solution, on the premise of ensuring that the endoscope can efficiently collect fluorescent photons, the volume of the endoscope is reasonably reduced to less than 5mm * 5mm * 5mm, which is smaller than the outer diameter of commercial endoscopes (9mm - 11mm), so that the endoscope in this solution can be directly used in cooperation with commercial endoscopes, greatly improving the practicability of the endoscope.

[0052] Embodiment 2

[0053] The difference between Embodiment 2 and Embodiment 1 is that: as Figure 6 shown, the photosensitive unit of the photodetector 33 is composed of an annular array of two-dimensional pixel photoelectric sensors, such as CCD (Charge Coupled Device) devices, CMOS (Complementary Metal Oxide Semiconductor) devices, FPA (Focal Plane Array) devices, PMT (Photomultiplier Tube) devices, single photon counting devices, or hybrid devices based on any of the above multiple photoelectric conversion principles, such as the hybrid photodetector (HPD) of Hamamatsu Corporation. The central hole or transparent material is used to transmit the excitation light of the objective lens 40. The annular array of two-dimensional pixel photoelectric sensors is used to receive the fluorescent photons that cannot be received by the objective lens 40.

[0054] Embodiment 3

[0055] The difference between Embodiment 3 and Embodiment 1 lies in that: the filter 331, the photosensitive unit 332 and the driving unit 333 are protected by a protective element, which is made of a light-transmitting insulating material, such as optical glass, etc. Setting the protective element can, on the one hand, be used to isolate the external sample from the photodetector 33, and at the same time can also be used for electrical isolation. A protective element with a thickness of several hundred micrometers can withstand the high driving voltage of the avalanche diode and prevent the high voltage of the photosensitive unit 332 from posing a danger to the external detection personnel.

[0056] The above are only the embodiments of the present invention, and common knowledge such as specific structures or characteristics known in the solutions is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application should be subject to the content of its claims, and the specific implementation manners described in the specification can be used to explain the content of the claims.

Claims

1. A three-dimensional microendoscope, comprising a micro imaging probe, the micro imaging probe including an objective lens that can face an external sample directly, and a front aperture for collecting fluorescence photons generated by the external sample is formed on the objective lens. It is characterized in that: The objective lens is connected to a photodetector for collecting fluorescence photons that cannot be collected by the front aperture. The photodetector includes a filter, a photosensitive unit, and a driving unit that are sequentially connected to each other. The filter and the objective lens can face the external sample simultaneously. The filter is used to filter out back-reflected and back-scattered fluorescence photons. The photosensitive unit is used to convert the fluorescence photons passing through the filter into electrical signals. The driving unit is used to provide high voltage and driving signals to the photosensitive unit and is connected to an external amplifier circuit and a computer. The number of the photodetectors is several, and several photodetectors are evenly distributed in the circumferential direction of the front aperture. A planar dichroic mirror scanner, which is used to separate the laser and the nonlinear optical signal and output the nonlinear optical signal, and is also used to change the incident angle of the laser to perform two-dimensional point scanning of the plane of the internal tissue of the external sample by the laser. A vertical dichroic mirror scanner, which is used to perform distal Z-axis scanning to achieve three-dimensional imaging.

2. A three-dimensional microendoscope according to claim 1, It is characterized in that: It further includes a collimating lens for collimating the laser output from the laser input fiber, reducing the chromatic aberration between lasers of different frequencies, and outputting a laser signal.

3. A three-dimensional microendoscope according to claim 1, It is characterized in that: The planar dichroic mirror scanner includes a dichroic mirror and a microelectromechanical driver for driving the dichroic mirror to change the angle. The dichroic mirror is polarization-sensitive, reflects S-type polarized light, and transmits p-type polarized light. The dichroic mirror is fixedly connected to the microelectromechanical driver, and the planar dichroic mirror scanner is located in the rear focal plane of the objective lens.

4. A three-dimensional microendoscope according to claim 3, It is characterized in that: The vertical dichroic mirror scanner has the same structure as the planar dichroic mirror scanner, and the vertical dichroic mirror scanner is located in the rear focal plane of the cylindrical lens.

5. A three-dimensional microendoscope according to claim 4, It is characterized in that: A reflecting mirror is provided on the optical path between the collimating lens and the planar dichroic mirror scanner.

6. A three-dimensional microendoscope according to claim 5, It is characterized in that: The reflecting mirror includes a transmission surface and a reflection surface. The transmission surface is provided with a transmission coating layer for enhancing the transmittance, and the reflection surface is provided with a reflection coating layer for enhancing the reflectance.

7. A three-dimensional microendoscope according to claim 6, It is characterized in that: The number of the reflecting mirrors is multiple.

8. A three-dimensional microendoscope according to any one of claims 1-7, It is characterized in that: The objective lens, the photodetector, the planar dichroic mirror scanner, the vertical dichroic mirror scanner, the cylindrical lens, the collimating lens, and the reflecting mirror are all wrapped with an outer shell.

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