Long-distance high-resolution fluorescence imaging device

Abstract

The invention belongs to the technical field of fluorescence imaging, and particularly relates to a long-distance high-resolution fluorescence imaging device. Comprising a laser emission module, a two-color beam splitter, a two-dimensional galvanometer, a telecentric field lens group, a fluorescent light beam collection and detection module, a lock-in amplifier and a computer, the double-color beam splitter reflects the laser beam; the two-dimensional galvanometer adjusts the angle of the laser beam incident to the telecentric field lens group; the telecentric field lens group enables the laser beam to be incident to an object to be measured at a preset angle; the fluorescent light beam collection and detection module obtains a first electric signal and a second electric signal corresponding to the position of the focusing light spot, and obtains a light intensity distribution diagram based on the laser beam; the lock-in amplifier is used for realizing noise suppression and signal amplification processing; and the computer carries out resolving based on an image convolution algorithm to obtain a microstructure image. According to the invention, the application requirements of high spatial resolution and time resolution of far-field observation are met.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fluorescence imaging technology, and particularly relates to a long-distance high-resolution fluorescence imaging device. BACKGROUND

[0002] Laser-Induced Fluorescence (LIF) is a kind of spectral technology based on photoluminescence effect. Its principle is to make molecules or atoms in the sample jump to the excited state by laser excitation, and then emit fluorescence when de-excitation, so as to realize qualitative and quantitative analysis of the composition or properties of the substance. When a sample is irradiated by a laser of a specific wavelength, the molecules absorb light energy and jump to the excited state, and then release energy by spontaneous radiation, emitting fluorescence with a longer wavelength. The fluorescence wavelength is usually longer than the excitation light wavelength due to energy loss, and can be detected by a filter. For example, materials with fluorescence properties can reflect their structure or environmental changes under ultraviolet or near-ultraviolet excitation.

[0003] The existing scheme for observing the microstructure of fluorescent materials in the far field is designed for specific application scenarios. The fluorescence microscope can achieve a long working distance (such as more than 50 mm) observation, but the long focal length objective lens in the fluorescence microscope usually has the following disadvantages due to long distance use: (1) The light field intensity distribution is uneven, mainly manifested as: the excitation light energy gradient decreases due to scattering, absorption and beam divergence during long-distance transmission; in large field imaging, the edge region has increased off-axis light incidence angle, resulting in reduced excitation light intensity and fluorescence collection efficiency, forming a "halo" artifact with a bright center and a dark edge; long optical path aggravates wavefront distortion such as spherical aberration and chromatic aberration, and the distribution of light intensity with a strong center and a weak periphery will result in weak peripheral fluorescence beams, thus causing poor imaging quality due to uneven activation of the molecules to be checked. (2) The collection imaging area is limited by the size of the camera target surface. In large field imaging, especially when the sample size is larger than the target surface size of the camera, the displacement of the sample is generally controlled by the displacement of the objective lens, so as to collect the fluorescence beams of different regions, and then obtain the complete field of view by image stitching, but this method will significantly reduce the time resolution of imaging. (3) The existing long-distance fluorescence microscope is limited by objective use scenarios and optical factors, and its working distance is rarely more than 200 mm. In actual application, when the long-distance fluorescence microscope is used in a high-temperature and high-pressure environment, i.e. the environmental temperature is above 500℃, the measured object will produce strong thermal radiation light, which will generate strong background light at the detection signal end, seriously affecting the information accuracy and reliability of laser-induced fluorescence detection, and the spatial resolution of the structure information of the measured object. SUMMARY

[0004] Therefore, the present application aims to provide a long-distance high-resolution fluorescence imaging device to solve the problem that the prior art cannot realize remote detection under high fluorescence background and special working conditions (such as high temperature and high pressure), and also cannot meet the demand of long-distance observation of microstructure. The present application can quickly capture the details of the microstructure changes of the far-field fluorescence solid-state material, and meet the application demand of high spatial resolution and time resolution of far-field observation.

[0005] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows: A long-distance high-resolution fluorescence imaging device, comprising: a laser emission module, a dichroic beam splitter, a two-dimensional galvanometer, a telecentric field lens group, a fluorescence beam collection and detection module, a lock-in amplifier and a computer, wherein the laser emission module emits a modulated laser beam; the dichroic beam splitter reflects the laser beam; the two-dimensional galvanometer adjusts the angle of the laser beam reflected by the dichroic beam splitter, so that the adjusted laser beam is incident to the telecentric field lens group at different angles; the telecentric field lens group causes the laser beam adjusted by the two-dimensional galvanometer to scan the surface of the measured object, and the included angle between the laser beam and the surface of the measured object is a preset angle, and the laser beams incident at different angles form focusing spots of the same size on the surface of the measured object; the fluorescence beam reflected from the measured object and the laser beam pass through the telecentric field lens group and the two-dimensional galvanometer, and then pass through the dichroic beam splitter to enter the fluorescence beam collection and detection module; the fluorescence beam collection and detection module processes the light transmitted by the dichroic beam splitter based on a specific waveband filter, separates the fluorescence beam into two mutually perpendicular polarization state fluorescence beams, performs photoelectric conversion on the two polarization state fluorescence beams obtained by separation, obtains first and second electric signals corresponding to the focusing spot positions, and obtains the light intensity distribution map of the laser spot based on the presence or absence of the laser beam; the lock-in amplifier performs noise suppression and signal amplification processing on the first and second electric signals corresponding to the current focusing spot position, and obtains first and second polarization characteristic signals corresponding to the current focusing spot position; the computer generates fluorescence intensity and polarization ratio corresponding to each focusing spot position based on the first and second polarization characteristic signals corresponding to each focusing spot position, and generates a position matrix composed of the real-time position data of the two-dimensional galvanometer in each adjustment state, and generates first and second polarization characteristic signal two-dimensional distribution maps, fluorescence intensity distribution map and polarization ratio two-dimensional distribution map based on the position matrix and the first and second polarization characteristic signals, fluorescence intensity and polarization ratio corresponding to each focusing spot position, inputs the first and second polarization characteristic signal two-dimensional distribution maps, fluorescence intensity distribution map and polarization ratio two-dimensional distribution map and the light intensity distribution map of the laser spot into a graph convolution algorithm for deconvolution operation, and obtains a microstructure image.

[0006] Further, the fluorescence beam collection and detection module comprises an achromatic doublet lens group, the achromatic doublet lens group comprises a confocal lens group and a pinhole diaphragm, the confocal lens group comprises a first lens and a second lens, and the pinhole diaphragm is arranged between the first lens and the second lens, and the center of the pinhole diaphragm coincides with the focal point of the confocal lens group.

[0007] Further, the fluorescence beam collection and detection module comprises a switchable filter module, the switchable filter module comprises a notch filter, a narrow-pass filter and a switching mirror, the notch filter is used for transmitting a wave band corresponding to the fluorescence beam, and the narrow-pass filter cooperates with the switching mirror to transmit a wave band corresponding to the laser beam.

[0008] Further, the fluorescence beam collection and detection module comprises a polarization beam splitter, a first detector and a second detector, wherein the polarization beam splitter separates the fluorescence beam transmitted by the switchable filter module into two mutually perpendicular polarization state fluorescence beams, and the first detector and the second detector are used for photoelectric conversion of the two polarization state fluorescence beams respectively to obtain a first electric signal and a second electric signal corresponding to the current focused spot position.

[0009] Further, if the switchable filter module selects to transmit the fluorescence beam, the notch filter is used to transmit a wave band corresponding to the fluorescence beam, so that the fluorescence beam is incident on the polarization beam splitter through the notch filter; if the switchable filter module selects to transmit the laser beam, the narrow-pass filter and the switching mirror are used to transmit a wave band corresponding to the laser beam, so that the laser beam is incident on the camera through the narrow-pass filter and the switching mirror to obtain the light intensity distribution map.

[0010] Further, the distance between the protective window of the telecentric field lens group and the surface of the object to be measured is between 200 mm and 600 mm.

[0011] Further, the first detector adopts a photomultiplier tube or a photodiode, and the second detector adopts a photomultiplier tube or a photodiode.

[0012] Further, the front surface of the object to be measured is located at the focal plane of the telecentric field lens group.

[0013] Further, the preset angle is in a range of -1° to 1°.

[0014] Further, a first polarization characteristic signal two-dimensional distribution map is constructed by using the position matrix and the first polarization characteristic signal corresponding to each focused spot position; a fluorescence distribution map is constructed by using the position matrix and the fluorescence intensity corresponding to each focused spot position, and the fluorescence intensity corresponding to the current focused spot position is the sum of the first polarization characteristic signal and the second polarization characteristic signal corresponding to the current focused spot position. Constructing a second polarization characteristic signal two-dimensional distribution map by using the position matrix and the second polarization characteristic signal corresponding to each focused light spot position; Constructing a polarization ratio two-dimensional distribution map by using the position matrix and the polarization ratio corresponding to each focused light spot position, and the polarization ratio corresponding to the current focused light spot position is the ratio of the difference between the first polarization characteristic signal and the second polarization characteristic signal corresponding to the current focused light spot position and the sum of the first polarization characteristic signal and the second polarization characteristic signal corresponding to the current focused light spot position.

[0015] Compared with the prior art, the present application can achieve the following beneficial effects: (1) The long-distance high-resolution fluorescence imaging device of the present application has a significant increase in working distance compared to existing long-distance fluorescence microscopes, and can meet the scene requirements of long-distance fine observation. Even when the working distance is as far as 600 mm, the resolution can still be maintained at about 20 microns. The use of a telecentric field lens ensures the uniformity of excitation of each point in the entire scanning area, ensuring good imaging quality of each point. The combination of an electric two-dimensional galvanometer and a telecentric field lens can achieve fast observation of large-area objects to be measured while ensuring resolution. Modulated laser scanning technology effectively eliminates high-fluorescence background. Fluorescence polarization contrast imaging improves the signal-to-noise ratio of laser-induced fluorescence, constructs multi-dimensional differences in images, and thus optimizes the observation effect of fine structure distribution under special conditions (such as high temperature). The image convolution algorithm realizes high spatial resolution images without the need for nanoscale ultra-high resolution as in existing long-distance fluorescence microscopes, reducing the requirement for extreme resolution.

[0016] (2) The long-distance high-resolution fluorescence imaging device of the present application proposes an innovative laser-induced fluorescence imaging technology scheme, which realizes fast capture of details of microstructure changes of far-field fluorescence solid materials and meets the requirements of high spatial resolution and time resolution for far-field observation. For large-size surfaces to be measured at a distance of up to 200-600 mm, the resolution requirement is usually in the order of tens of microns. The present application can achieve a resolution of 1-5 microns through telecentric imaging and image spatial analysis processing. The present application solves the problems of insufficient resolution, uneven light field distribution, and slow imaging speed in the prior art when observing at a long distance.

[0017] (3) The long-distance high-resolution fluorescence imaging device provided by the application, adopts a two-dimensional galvanometer and a telecentric field lens combination mode to realize fluorescence scanning, the two-dimensional galvanometer realizes the change of the deflection angle of the laser beam through the fast and accurate control of the reflecting mirror, the telecentric field lens group can eliminate the aberration caused by the laser beam with different deflection angles, and the telecentric angle of the telecentric field lens group is usually less than 4 degrees, the smaller telecentric angle means that the laser beam is focused in a manner closer to the vertical incidence of the surface of the object to be measured, and this design makes the spot shape in the full field of view keep circular and the spot is smaller; the application utilizes spatial filtering to suppress the environmental fluorescence background and improve the spatial distribution capability; the application captures the polarization state characteristic distribution of the fluorescence at the same position, utilizes the polarization difference between different structures, and significantly improves the identification of the low-contrast fine structure in the material; the application relies on modulated laser to eliminate the influence of background light; the application adopts image deconvolution processing, and solves the problem of low resolution of the surface structure of the material under the action of the long-distance large spot. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the application illustrated in the drawings, and their description, are presented to add generic scope to this application. In the drawings: Figure 1 A structure schematic view of the long-distance high-resolution fluorescence imaging device according to the embodiments of the application; Figure 2 A light path switching schematic view according to the embodiments of the application; Figure 3 A structure schematic view of the two-dimensional galvanometer and the telecentric field lens group according to the embodiments of the application.

[0019] Explanation of the reference signs: 1, laser; 2, polarizer; 3, collimating lens group; 4, half-wave plate; 5, beam expander; 6, dichroic beam splitter; 7, two-dimensional galvanometer; 7-1, X galvanometer; 7-2, Y galvanometer; 8, telecentric field lens group; 9, object to be measured; 10, first lens; 11, pinhole diaphragm; 12, second lens; 13, filter; 13-1, narrow-pass filter; 13-2, notch filter; 14, switching mirror; 15, polarization beam splitter; 16, first fluorescence collection lens; 17, second fluorescence collection lens; 18, first detector; 19, second detector; 20, lock-in amplifier; 21, laser modulator; 22, galvanometer controller; 23, camera; 24, computer. DETAILED DESCRIPTION

[0020] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not constitute limitation to the present application.

[0021] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0022] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation to the present application. In addition, the terms "first", "second" and the like are only used for description purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0023] In the description of the present application, it should be noted that unless otherwise specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0024] The process of detection using laser-induced fluorescence technology has the advantages of non-destructive, non-destructive, high sensitivity, effective protection of samples, and is an important research and analysis method. At present, this technology has been widely used in microbial detection, semiconductor detection, environmental detection, fluid detection and other close-range scene detection and testing work. In the field of material manufacturing, chemical process or equipment working condition detection, especially in special environments (such as high temperature, high pressure, etc.), remote fluorescence detection has extremely important significance for process parameter control and real-time observation. By monitoring the changes of fluorescence in special environments, such as the generation of cracks, phase transition and other material dynamic characteristics, key data support is provided for material performance optimization, process improvement and theoretical research. However, there is a contradiction between the requirements of remote operation conditions and the observation of microstructure under high spatial resolution, and the realization of remote fluorescence detection microstructure technology under high temperature background has great difficulty, and there is no corresponding technical design scheme or equipment application at present.

[0025] Among the current main laser-induced fluorescence (Laser-Induced Fluorescence, LIF) imaging technologies, either near-field observation is used to obtain super-resolution images (resolution up to tens of nanometers to hundreds of nanometers); or remote macroscopic imaging has no special resolution requirements; or the fluorescence characteristics of the fluid are monitored in the far field to obtain images of related temperature and concentration; The object of the above-mentioned existing technical solutions is all non-fluorescent background or low-fluorescent background, however, in material science research and actual production, there is a core demand that has not been covered by existing technologies: when solid fluorescent materials are in extreme environments of high temperature and high pressure, the fluorescence background generated by strong heat radiation will seriously interfere with the signal, and the detection equipment cannot be deployed close to the environment, at this time, a technology is needed that can realize three-dimensional imaging of material fluorescence intensity in the far field conditions through laser excitation and fluorescence beam collection—the core is to break through the three technical bottlenecks of "strong background interference suppression", "far-field microscale resolution (such as tens of microns of cracks, collapse, etc.)", "real-time capture of dynamic changes of solid materials", and ultimately realize the intuitive monitoring of the evolution process of the microstructure of the material surface under extreme environments. The lack of such a technical solution has resulted in a long-term observation blind spot in the study of the microstructure of solid fluorescent materials under extreme conditions, and filling this gap has irreplaceable value for promoting breakthroughs in materials science and optimizing industrial production.

[0026] To meet this technical bottleneck, the present application proposes a solution: based on the principle of laser-induced fluorescence imaging, breakthrough the observation bottleneck in extreme environment through the synergistic effect of multiple technologies. Specifically, first, the modulation laser and spatial filtering scanning technology are used to effectively eliminate the high fluorescence background interference generated by strong thermal radiation in high temperature and high pressure environment, laying a pure foundation for subsequent signal processing; On this premise, the fluorescence polarization contrast imaging method is introduced to further improve the signal-to-noise ratio of the laser-induced fluorescence beam and eliminate the background light effect of high-temperature heat radiation, ensuring that the weak fluorescence features can be clearly extracted; At the same time, combined with the image convolution algorithm, the collected signal is optimized, and finally the high spatial resolution image is reconstructed. This scheme can achieve a resolution of 10-20 microns in the far field distance interval of 200-600 mm through telecentric imaging, and further improve the resolution after deconvolution image processing, and finally 1-5 microns of high resolution can be achieved. Fast scanning imaging can be completed, thereby synchronously meeting the high spatial resolution and high timeliness requirements for observing the microstructure of fluorescent characteristic materials, and successfully realizing the far-field precise monitoring of the microstructure of solid-state fluorescent materials in extreme environment.

[0027] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0028] As Figure 1As shown, the present application provides a long-distance high-resolution fluorescence imaging device, a laser emission module, a dichroic beam splitter 6, a two-dimensional galvanometer 7, a telecentric field lens group 8, a fluorescence beam collection and detection module, a lock-in amplifier 20 and a computer 24, wherein the laser emission module emits a modulated linearly polarized laser beam; the dichroic beam splitter 6 reflects the laser beam; the two-dimensional galvanometer 7 adjusts the angle of the laser beam reflected by the dichroic beam splitter 6, so that the adjusted laser beam is incident on the telecentric field lens group 8 at different angles; the telecentric field lens group 8 causes the laser beam adjusted by the two-dimensional galvanometer 7 to scan the surface of the object 9 to be measured, and the angle between the laser beam and the surface of the object 9 to be measured is a preset angle, and the laser beams incident at different angles form focusing spots of the same size on the surface of the object 9 to be measured; the fluorescence beam reflected from the object 9 to be measured and the laser beam reflected from the object 9 to be measured pass through the telecentric field lens group 8 and the two-dimensional galvanometer 7, and then are transmitted through the dichroic beam splitter 6 into the fluorescence beam collection and detection module; the fluorescence beam collection and detection module processes the light transmitted by the dichroic beam splitter 6 based on a filter of a specific waveband, separates the fluorescence beam into two mutually perpendicular polarization state fluorescence beams, photoelectrically converts the two polarization state fluorescence beams obtained by separation to obtain first and second electric signals corresponding to the positions of the focusing spots, and obtains the light intensity distribution of the laser spot based on the presence or absence of the laser beam; the lock-in amplifier 20 performs noise suppression and signal amplification processing on the first and second electric signals corresponding to the current focusing spot position based on a reference signal to obtain first and second polarization characteristic signals corresponding to the current focusing spot position; the computer 24 generates fluorescence intensity and polarization ratio corresponding to each focusing spot position based on the first and second polarization characteristic signals corresponding to each focusing spot position; the computer 24 groups the real-time position data of the two-dimensional galvanometer 7 in each adjustment state into a position matrix, and generates first and second polarization characteristic signal two-dimensional distribution maps, fluorescence intensity distribution maps and polarization ratio two-dimensional distribution maps based on the position matrix and the first and second polarization characteristic signals, fluorescence intensity and polarization ratio corresponding to each focusing spot position; the computer 24 inputs the first and second polarization characteristic signal two-dimensional distribution maps, fluorescence intensity distribution maps, polarization ratio two-dimensional distribution maps and light intensity distribution of the laser spot into a graph convolution algorithm for deconvolution operation to obtain a microscopic structure image with multi-dimensional information.

[0029] It should be noted that the laser emission module includes a laser modulator 21, a laser 1, a polarizer 2, a collimating mirror group 3, a half-wave plate 4 and a beam expander mirror group 5, both ends of the laser modulator 21 are connected with a lock-in amplifier 20 and the laser 1 respectively, the lock-in amplifier 20 obtains a reference signal consistent with the frequency of the modulation signal based on the modulation signal output by the laser modulator 21, at the same time, the laser 1 outputs a linearly polarized type of laser beam after being modulated by the laser modulator 21, the linearly polarized type of laser beam passes through the polarizer 2, the collimating mirror group 3, the half-wave plate 4 and the beam expander mirror group 5 in turn, and the diameter of the laser beam is expanded and the divergence angle is reduced.

[0030] Further, based on the principle of laser-induced fluorescence imaging, the coaxial transmitting and receiving light path is adopted, and the modulated output linearly polarized laser is used to excite the fluorescence of the micro area material, specifically: the modulated laser beam emitted by the laser emission module is incident to the surface of the measured object 9 through the dichroic beam splitter 6 (high-reflective laser wavelength, transmissive other wavelengths), the two-dimensional galvanometer 7 (an electrically controlled micro two-dimensional galvanometer 7 can be used, the incident light is located on the same straight line with the central optical axis of the collimating mirror group 3 and the beam expander mirror group 5), and the telecentric field lens group 8, the point on the surface of the measured object 9 irradiated by the laser spot generates a fluorescence beam under the excitation of the laser, the fluorescence beam is collected by the telecentric field lens group in the reverse light path, and then passes through the telecentric field lens group 8, the two-dimensional galvanometer 7, the dichroic beam splitter 6, the achromatic doublet lens group, the switchable filter module, and is guided to the camera 23 and the fluorescence detection light path (the achromatic doublet lens group, the switchable filter module, the camera 23 and the fluorescence detection light path all belong to the fluorescence beam collection and detection module) respectively, and finally the signal is extracted by the lock-in amplifier 20 to obtain an electrical signal with high signal-to-noise ratio corresponding to the fluorescence beam, and the electrical signal is transmitted to the computer 24 end for real-time processing by software, and a three-dimensional image of the fluorescence beam intensity of the entire scanning range of the measured object 9 is constructed.

[0031] In the present application, the two-dimensional galvanometer 7 is composed of two mutually perpendicular galvanometers, the mirror surface of each galvanometer is driven by an independent motor, and the two galvanometers control the deflection of the X-axis and the Y-axis respectively, and the deflection of the X galvanometer 7-1 and the Y galvanometer 7-2 controls the incident angle of the laser beam reflected by the dichroic beam splitter 6 to the telecentric field lens group 8. The telecentric field lens group 8 collects the laser beams of different angles reflected by the two-dimensional galvanometer 7, and focuses the laser beams to different positions on the surface of the measured object 9 in the far field, and ensures that the chief ray on the surface of the measured object 9 is always parallel to the optical axis. The telecentric field lens group 8 can eliminate aberration, no matter how the deflection angle of the laser changes, the laser beam can be focused on the same plane, and the size of the focused spot can reach microns. The present application realizes continuous two-dimensional surface scanning on the surface of the measured object 9 by galvanometer control, and the deflection angle of the laser beam is controlled by electromagnetic drive and closed-loop feedback of the electric two-dimensional galvanometer 7, so that different positions on the surface of the measured object 9 can be quickly scanned.

[0032] In some embodiments, the fluorescence beam collection and detection module comprises an achromatic double lens group, the achromatic double lens group comprises a confocal lens group and a pinhole diaphragm 11, the confocal lens group comprises a first lens 10 and a second lens 12, and the pinhole diaphragm 11 is arranged between the first lens 10 and the second lens 12, and the center of the pinhole diaphragm 11 coincides with the focal point of the confocal lens group.

[0033] The combination of the first lens 10 and the second lens 12 is a confocal double lens, and a micro-hole (i.e. the pinhole diaphragm 11) at the confocal point is used for spatial filtering to avoid light outside the center of the laser focusing spot from entering the rear optical detection system, filter out stray light outside the center of the laser focusing spot, improve the spatial resolution of the fluorescence, and at the same time reduce the environmental fluorescence interference and improve the signal-to-noise ratio.

[0034] In some embodiments, the fluorescence beam collection and detection module comprises a switchable filter module, the switchable filter module comprises a notch filter 13-2, a narrow-pass filter 13-1 and a switching mirror 14, the notch filter 13-2 is used for transmitting a waveband corresponding to the fluorescence beam, and the narrow-pass filter 13-1 cooperates with the switching mirror 14 to transmit a waveband corresponding to the laser beam.

[0035] It should be noted that the light emitted by the achromatic double lens group is quasi-parallel light, the quasi-parallel light horizontally enters the switchable filter module, and the confocal lens group is coaxially arranged with the notch filter 13-2 or the narrow-pass filter 13-1 in the light transmission state. The notch filter 13-2 and the narrow-pass filter 13-1 are used for selecting light of a specific waveband. Specifically, if the laser beam is selected to be transmitted, the confocal lens group is coaxially arranged with the narrow-pass filter 13-1, the narrow-pass filter 13-1 cooperates with the switching mirror 14 to transmit a waveband corresponding to the laser beam, and the laser beam is sequentially incident into the camera 23 with high resolution through the narrow-pass filter 13-1 and the switching mirror 14. The camera 23 is used to capture images of the excitation spot in each region in two states of laser being on (with laser irradiation) and laser being off (without laser irradiation), and the intensity distribution of the excitation spot is obtained. The images captured in the two states of the laser beam being present and absent are subtracted to eliminate the background of light radiation, and the intensity distribution map of the laser spot is obtained. If the fluorescence beam is selected to be transmitted, the confocal lens group is coaxially arranged with the notch filter 13-2, and the notch filter 13-2 is used for transmitting a waveband corresponding to the fluorescence beam. The fluorescence beam passes through the polarization beam splitter, and two lights with perpendicular polarization directions are collected into high-sensitivity photodetectors and converted into electrical signals.

[0036] In some embodiments, the fluorescence beam collection and detection module comprises a polarization beam splitter 15, a first detector 18 and a second detector 19, wherein the polarization beam splitter 15 separates the fluorescence beam transmitted by the switchable filter module into two mutually perpendicular polarization state fluorescence beams, and the first detector 18 and the second detector 19 are used for photoelectric conversion of the two polarization state fluorescence beams respectively, so as to obtain a first electrical signal and a second electrical signal corresponding to the current focused light spot position.

[0037] It should be noted that a first fluorescence collection lens 16 is arranged between the polarization beam splitter 15 and the first detector 18, and a second fluorescence collection lens 17 is arranged between the polarization beam splitter 15 and the second detector 19, and the first fluorescence collection lens 16 and the second fluorescence collection lens 17 are used for focusing the polarization state fluorescence beams received respectively, and coupling the corresponding polarization state fluorescence beams to the corresponding detectors.

[0038] In some embodiments, if the switchable filter module selects to transmit the fluorescence beam, a notch filter 13-2 is used to transmit the waveband corresponding to the fluorescence beam, so that the fluorescence beam is incident on the polarization beam splitter 15 through the notch filter 13-2; if the switchable filter module selects to transmit the laser beam, a narrow-pass filter 13-1 and a switching mirror 14 are used to transmit the waveband corresponding to the laser beam, so that the laser beam is incident on the camera 23 through the narrow-pass filter 13-1 and the switching mirror 14, and the light intensity distribution map is obtained.

[0039] In some embodiments, the first detector 18 uses a photomultiplier tube or a photodiode, and the second detector 19 uses a photomultiplier tube or a photodiode.

[0040] After the fluorescence beam is converted into an electrical signal by the detector, the first electrical signal and the second electrical signal (i.e. the fluorescence intensity signals of the two polarization states) are obtained by a laser modulation lock-in amplifier 20, further noise suppression and signal-to-noise ratio improvement are performed, and based on the scanning of the two-dimensional galvanometer 7, the fluorescence surface distribution images of the two polarization states are obtained. Both of the two fluorescence distribution images contain the fluorescence image of the laser spot center intensity distribution characteristics. The above operation is repeated, the electrical signals of the two polarization states of different scanning points are transmitted to the computer 24 terminal, the scanning position synchronous data of the two-dimensional galvanometer 7 are combined, and the microscopic structure image is synthesized by using an image processing software (such as an image deconvolution algorithm). It reflects the image related to the fluorescence center distribution in the material, such as crack, stress and other distribution characteristics.

[0041] In some embodiments, the first detector 18 uses a photomultiplier tube or a photodiode, and the second detector 19 uses a photomultiplier tube or a photodiode.

[0042] In some embodiments, the front surface of the object to be measured 9 is located at the focal plane of the telecentric field lens group 8.

[0043] In some embodiments, the preset angle ranges from -1 to 1 degrees.

[0044] In some embodiments, the first polarization characteristic signal two-dimensional distribution map is constructed by using the position matrix and the first polarization characteristic signal corresponding to each focused light spot position. The fluorescence distribution map is constructed by using the position matrix and the fluorescence intensity corresponding to each focused light spot position, and the fluorescence intensity corresponding to the current focused light spot position is the sum of the first polarization characteristic signal and the second polarization characteristic signal corresponding to the current focused light spot position. The second polarization characteristic signal two-dimensional distribution map is constructed by using the position matrix and the second polarization characteristic signal corresponding to each focused light spot position. The polarization ratio two-dimensional distribution map is constructed by using the position matrix and the polarization ratio corresponding to each focused light spot position, and the polarization ratio corresponding to the current focused light spot position is the ratio of the difference between the first polarization characteristic signal and the second polarization characteristic signal corresponding to the current focused light spot position and the sum of the first polarization characteristic signal and the second polarization characteristic signal corresponding to the current focused light spot position.

[0045] For ease of understanding, the specific working mode will be illustrated below. Taking the laser 1 outputting a laser beam with a wavelength of 355 nm as an example, the distance between the surface of the fluorescent material to be observed and the protective window of the telecentric field lens group 8 is set as the working distance of the device. The actual distance value determines the minimum working distance of the system design (the working distance is usually within 600 mm). The protective window of the telecentric field lens is made of transparent and non-fluorescent fused quartz and is subjected to double-sided high polishing treatment. The light transmission ratio of the protective window of the telecentric field lens is higher than 93%, which avoids the phenomena of light absorption, fluorescence and scattering of the protective window under the action of laser. The surface of the dichroic beam splitter 6 needs to be coated. The coating requirement is to achieve high reflection for the laser wavelength and high transmission for other wavelengths. It should be emphasized that although the dichroic beam splitter 6 achieves high reflection for the laser wavelength, a part of the laser beam reflected from the object to be measured 9 still transmits through the fluorescent beam when the fluorescent beam transmits through the dichroic beam splitter 6. According to the properties of the fluorescent material, a laser light source with a corresponding wavelength is selected. In this embodiment, a laser beam with a wavelength of 355 nm is used as the incident excitation light source. The 355 nm laser belongs to the ultraviolet waveband, and the photon energy (about 3.5 eV) is significantly higher than that of visible light laser, which can excite higher energy level electron transition of the substance. At the same time, the shorter wavelength can make the laser focusing spot size smaller.

[0046] The UV light has high energy transfer efficiency in most materials and small thermal influence area. The linearly polarized laser beam is expanded to a laser beam with a diameter of 14 mm by a collimating mirror and a beam expander 5, and the polarization direction of the laser beam is modulated by a half-wave plate 4. The polarization direction of the laser beam can be modulated by the half-wave plate 4, and can be switched between 0° (parallel to the transmission polarization direction of the fluorescence polarization beam splitter 15), 45° and 90°. The modulated laser beam is reflected by a dichroic beam splitter 6 into a motorized two-dimensional galvanometer 7. The X galvanometer 7-1 and the Y galvanometer 7-2 are composed of two independent scanners of X axis and Y axis. The X galvanometer 7-1 and the Y galvanometer 7-2 are both wide-band high-reflectivity mirrors with a reflectivity of >95%.

[0047] The rotation angle program is set by the computer 24, and the rotation angle command is sent to the galvanometer controller 22, so as to control the rotation angle of the X galvanometer 7-1 and the Y galvanometer 7-2, and then adjust the position of the laser beam entering the telecentric field lens group 8. The laser beam with different incident angles can be ensured to be nearly vertically incident on the surface of the measured object 9 (i.e. the scanning area) after passing through the telecentric field lens group 8, and the spot in the whole scanning area can be kept circular and uniform. The position of the front surface of the measured object 9 is located at the focal plane of the telecentric field lens group 8, so as to obtain the smallest spot diameter and realize the maximum spatial resolution. The angle of the X galvanometer 7-1 is slightly changed, and the laser beam focal spot moves horizontally on the surface of the measured object 9. The angle of the Y galvanometer 7-2 is slightly changed, and the laser beam focal spot moves vertically on the surface of the measured object 9. In this way, the measured surface can be scanned row by row upwards / downwards, i.e. the matrix scanning of the measured surface is completed.

[0048] The surface material of each focal point small spot is excited to generate a fluorescence signal, which is mixed with part of the stray laser signal, environmental thermal radiation and stray light. Within the collection solid angle range of the telecentric field lens group 8, the fluorescence signal is collected by the telecentric field lens group 8 in reverse order, returned to the two-dimensional galvanometer 7, and then reflected to the dichroic beam splitter 6. Due to the uncertainty of the direction of the background stray light of the object 9 to be measured, a high-intensity off-axis stray light is formed in the two-dimensional galvanometer 7 area. Therefore, the off-axis light is independently isolated and treated to prevent the off-axis light from being introduced into the subsequent optical system. The fluorescence signal, a small amount of reflected laser light and stray background light pass through the dichroic beam splitter 6. To further suppress the light interference in the non-laser spot center region of the object 9 to be measured, the light transmitted through the dichroic beam splitter 6 enters the confocal achromatic double lens group. A pinhole diaphragm 11 is arranged at the focal point of the confocal lens group. The aperture size of the pinhole diaphragm 11 can suppress the off-axis light. The fluorescence beam collection and detection module can not only improve the signal-to-noise ratio of the system, but also improve the spatial resolution of the scanning point through spatial filtering. The light emitted from the confocal lens group is quasi-parallel light. The quasi-parallel light horizontally enters the coaxially arranged notch filter 13-2 or narrow pass filter 13-1, which is associated with the subsequent turning mirror for transformation. The filter switching mode is divided into two types: 1) the 355 nm notch filter 13-2 can isolate the interference laser of the 355 nm wave band, and has high transmittance in the specific fluorescence wave band to be measured; and 2) the 355 nm narrow pass filter 13-1 is used to realize laser spot distribution imaging. Through the flat push displacement mechanism, when the laser spot distribution imaging is measured, the 355 nm narrow pass filter 13-1 and the switching mirror 14 are integrally linked and simultaneously pushed into the optical path, so that the laser beam is introduced into the camera 23 to obtain a two-dimensional image of the laser spot. When the fluorescence intensity of the scanning point is measured, the notch filter 13-2 is pushed into the optical path, and the fluorescence beam is introduced into the polarization beam splitter 15. After being focused by the lens, the two beams of vertically polarized fluorescence beams are coupled to the corresponding detectors to be converted into electrical signals. Then, the noise is further suppressed and the signal-to-noise ratio is improved through the lock-in amplifier 20. The two quantized signals of different scanning points are transmitted to the computer 24 terminal. Combined with the scanning position synchronous data, the microstructure image is synthesized through the image processing software.

[0049] In the embodiment, the rapid imaging is realized by continuously fine-tuning the orthogonal X galvanometer 7-1 and Y galvanometer 7-2, changing the direction angle of the laser beam, and then eliminating the distortion through the telecentric field lens group 8, so that the incident light is always perpendicular to the surface of the object 9 to be measured. Thus, the focal spot of the laser beam is scanned on the focal plane of the telecentric field lens group 8, and then the microstructure of the fluorescent material is depicted based on the correlation between the fluorescence signal distribution intensity and the focused spot position.

[0050] The telecentric field lens group 8 can be directly selected or customized according to the actual working distance, scanning field size and resolution requirements, then according to the requirements of the telecentric field lens group 8 on the focusing spot diameter and the setting distance of the X galvanometer 7-1 and the Y galvanometer 7-2, the required electric two-dimensional galvanometer 7 is selected, and the optical fiber light source is selected to match the beam diameter, and finally the expansion ratio is calculated and the appropriate expansion mirror is selected.

[0051] Taking the small angle change of the Y galvanometer 7-2 as an example: when the Y galvanometer 7-2 produces a small deflection around its rotation axis, the propagation direction of the laser beam reflected by it will change correspondingly along the vertical direction, thereby causing the focusing position of the laser spot on the surface of the measured object 9 to produce a displacement along the vertical direction. The greater the deflection angle of the galvanometer, the greater the displacement of the laser spot in the vertical direction. The principle of action of the X galvanometer 7-1 is the same: by adjusting the rotation angle of the X galvanometer 7-1, the propagation direction of the laser beam can be changed along the horizontal direction, thereby realizing the scanning displacement change of the laser spot on the surface of the measured object 9 in the horizontal direction. After the electric two-dimensional galvanometer 7 is connected with the telecentric field lens group 8 by screw connection, the distance between the center of the Y galvanometer 7-2 and the surface of the last lens of the telecentric field lens group 8 is fixed, thereby limiting the working distance within a certain range.

[0052] As shown in Figure 3 , assuming that the total length of the distance from the center of the Y galvanometer 7-2 to the vertex of the last lens of the telecentric field lens group 8 is L=300mm, when the Y galvanometer makes the laser beam direction angle deviate from the normal incidence angle θ, the image height of the telecentric field lens group 8 and the scanning angle are in a linear relationship, which satisfies the following relationship: (h is the image height, L is the total length, θ is the optical deflection angle radian value of the galvanometer (X galvanometer 7-1 or Y galvanometer 7-2)), then the linear distance of the total scanning field is When the size of the scanning field is 30mm×30mm, the scanning angle of the system is set to θ=30 / 2 / 300=0.05rad≈2.86°, that is, the scanning angle range of the X and Y galvanometers set by the system at this time is 0°~±2.9°. When the working distance WD of the telecentric field lens group 8 (the distance between the rear surface of the telecentric field lens group and the front surface of the measured object 9) is 370mm, and the focusing spot diameter of the telecentric field lens group 8 at the focal plane is about 12μm, then the minimum amplitude of the step angle of the electric controller for controlling the two-dimensional scanning needs to match the spot size focused on the surface of the measured object 9 by the telecentric field lens group 8 (the measured object 9 is placed at the focal plane position of the telecentric field lens group 8). When the resolution of the galvanometer controller 22 is 12μrad, the scanning linearity displacement under the minimum resolution angle can be calculated as follows: , that is, the minimum variable linearity displacement is h min =300×10 -3 ×12×10 -6= 3.6 μm, which can meet the requirement of the resolution 12 μm of the telecentric field lens 8.

[0053] According to the above, the diameter of the focused spot passing through the telecentric field lens 8 is controlled at 12 microns, and considering the imaging requirement that the spot excitation areas between two test points should have a certain intersection area, so that the changes of the microstructure details can be clearly obtained, then assuming that there is 30% overlap area between the two focused spots, then the scanning point spacing can be calculated as follows: scanning point spacing = spot diameter x (1 - overlap ratio), scanning point spacing = 12 microns x (1 - 0.3) = 12 microns x 0.7 = 8.4 microns, so the displacement amplitude of the focused spot of the telecentric field lens 8 controlled by the rotation angle of the galvanometer should not be higher than 8 microns, and at this time the degree of change of each rotation angle is set to = 8 x 10 -3 / 300 ≈ 26 μrad.

[0054] The scanning time is estimated as follows: for example, the scanning area size is 30 mm x 30 mm, the displacement change step is 8 microns, the continuous movement speed of the galvanometer is 1 m / s, the jump speed is 0.8 m / s, and the step response time is 800 μs, then the scanning time of one row is about 0.03 / 1 x 10 3 + 8 x 10 -6 / 0.8 + 0.8 ≈ 30.8 ms / row (calculated according to continuous scanning in one direction), the total number of rows is 30 x 10 3 / 8 = 3750 rows, and the total scanning time is 3750 x 30.8 ≈ 116 s (1 minute 55.5 seconds) (continuous scanning in one direction), if one-way scanning is not supported, the total time is about 3750 x 69.1 ≈ 259.2 s (4 minutes 19.2 seconds). This is the scanning time of the laser beam on the object to be measured 9, and the propagation speed of the excited fluorescent signal is counted by the speed of light, so the time of recovering the fluorescent signal is very small and can be ignored, which is almost instantaneous reception. At this time, the time resolution of the photomultiplier tube may constitute a limitation. However, the time resolution of the photomultiplier tube covers a very wide range, from sub-nanosecond to tens of picoseconds for high-end models. Even if it is calculated at the sub-nanosecond level, its time resolution is much smaller than the excitation scanning time of the incident light on the fluorescent material, so it will not become a limiting factor.

[0055] Considering the aberration and chromatic aberration of the optical element, the confocal achromatic double lens group combined with the pinhole aperture 11 at the focal point to achieve spatial filtering can eliminate the problem of resolution decline caused by spot diffusion, ensuring that the area of single-point fluorescence collection is not greater than 12 μm. The 12 μm size resolution capability is still insufficient for some fine structures. Polarized fluorescence is extremely sensitive to the environment of the emission center in the material. In different positions, the fine changes of the structure (such as the edge interface of the crack and the deep light-emitting center) will exhibit different excitation and emission polarization characteristics. Based on this, the multi-dimensional difference of the image can be constructed through the distribution of different polarization state fluorescence, thereby improving the detection effect of the fine distribution of the structure under special conditions (such as high temperature). Of course, the influence of the spatial distribution of the laser spot on the polarized fluorescence image also needs to be eliminated, and this influence can be removed by image deconvolution. It is worth noting that the sum of different polarizations (S polarization and P polarization) is equal to the total intensity of the laser spot.

[0056] The switchable filter module, i.e. the filter and the subsequent turning mirror, is co-located as shown in Figure 2 , so that a simple excitation laser band image can be obtained. The image of the laser spot on the surface of the object to be measured 9 after spatial filtering is obtained by the camera 23, and the surface distribution of the intensity of the excitation spot on the object to be measured 9 is obtained . The intensity distribution of the laser beam at the beam waist (focal point) satisfies the characteristics of the Gaussian beam, that is: . The central intensity of the Gaussian beam at the beam waist is the highest, and it decays exponentially along x and y. In this way, the fluorescent substance originally at the center of the laser spot will reduce the contribution to the fluorescence collection as the center of the laser spot formed by the laser beam moves. However, on the contrary, even if the laser does not converge at a certain point, the point will still contribute to the fluorescence. This leads to a decrease in the resolution capability of the material fine structure identification.

[0057] Under the action of the laser spot, the total fluorescence intensity in the excitation area of a certain energy range of the emission of the object to be measured 9 is marked as . Here is the center position of the area, which is also the coordinate of a certain image point in the original fluorescence image. Assuming that the real fluorescence particle distribution state of the object to be measured 9 is only related to the microstructure of the material, i.e. there is no aggregation or partition of itself, but it is uniformly distributed in the material, and changes with the microstructure of the material such as the density or crack, flatness, etc. Under uniform excitation, its fluorescence distribution is a copy of the structure, and the distribution function of the structure is set as : ; wherein represents the light intensity distribution of the laser focus at the center , A is the fluorescence conversion coefficient, The function distribution of f(x, y) is obtained by laser scanning, i.e. the original fluorescence image obtained by the test system, which can be a polarized fluorescence image of two polarizations, a total fluorescence intensity image of the sum of the two polarizations, or a data processing image associated therewith, such as a polarization ratio image and L(x, y) can be obtained from the laser spot image. Through image deconvolution algorithm, f(x, y) can be restored to obtain the fine structure information of the material. After image deconvolution, the resolution of the obtained image can approach the diffraction limit.

[0058] In the image reconstruction process, the laser beam is driven to scan the material surface point by point through the two-dimensional galvanometer 7 control system, and the fluorescence signal of each scanning point is collected in real time by the photomultiplier tube and converted into an electric signal. After phase-sensitive detection by the lock-in amplifier 20, the signal-to-noise ratio is significantly improved. Through two images of vertical polarization and the polarization ratio image, more fine changes of the material structure can be captured, and the polarization ratio can also eliminate the stable non-polarized background light signal, improve the contrast of the image and obtain fine structures. These images provide intuitive reference for observing the changes of the microstructure of the material: if cracks or collapses are found, subsequent operations can be terminated immediately; at the same time, it can also provide a direction for optimizing the proportion of each component of the material.

[0059] The wavelength of the excitation light source in the optical path is not limited to the 355 nm band, and other excitation light sources and corresponding mirror coatings of other wave bands can be matched according to the fluorescence characteristics of the material or actual needs. The detector used in this scheme is a photomultiplier tube, which can also be replaced by other types of detectors such as avalanche photodiodes and silicon photomultipliers according to actual needs. If there is a lot of stray light in the returned fluorescence signal, and the wave band of the fluorescence signal is known, the wavelength selection of the filter is limited, and the filtering accuracy is higher, the detector can be replaced by a monochromator. The monochromator can flexibly adjust the wavelength range, has higher resolution and adaptability, and can meet the use requirements in different scenes.

[0060] It should be understood that the various forms of the flow shown above can be reordered, added, or deleted steps. For example, the steps described in the present disclosure can be executed in parallel, in sequence, or in a different order, as long as the desired results of the technical solutions of the present disclosure can be achieved, which is not limited herein.

[0061] The above specific embodiments do not constitute a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A long-distance, high-resolution fluorescence imaging device, characterized by: include: A laser emission module, a two-color beam splitter, a two-dimensional galvanometer, a telecentric field lens group, a fluorescence beam collection and detection module, a phase-locked amplifier and a computer, wherein the laser emission module emits a modulated laser beam; the two-color beam splitter reflects the laser beam; the two-dimensional galvanometer adjusts the angle of the laser beam reflected by the two-color beam splitter, so that the angle of the adjusted laser beam incident on the telecentric field lens group is different; the telecentric field lens group makes the laser beam adjusted by the two-dimensional galvanometer scan the surface of the object to be measured, and the angle between the laser beam and the surface of the object to be measured is a preset angle, and the laser beam incident at different angles forms a consistent focused spot size on the surface of the object to be measured; the fluorescence beam reflected from the object to be measured and the laser beam are collected and detected by the telecentric field lens group and After the two-dimensional galvanometer, it is transmitted through the two-color beam splitter into the fluorescent beam collection and detection module; the fluorescent beam collection and detection module processes the light transmitted by the two-color beam splitter based on a filter of a specific wavelength band, and separates the fluorescent beam into two mutually perpendicular polarization state fluorescent beams, performs photoelectric conversion on the two polarization state fluorescent beams obtained by separation, obtains a first electrical signal and a second electrical signal corresponding to the position of the focused light spot, and obtains a light intensity distribution diagram of the laser spot based on the presence or absence of the laser beam; the phase-locked amplifier performs noise suppression and signal amplification processing on the first electrical signal and the second electrical signal corresponding to the current focused light spot position, and obtains a first polarization characteristic signal and a second polarization characteristic signal corresponding to the current focused light spot position; The computer generates the fluorescence intensity and polarization ratio corresponding to each focused spot position based on the first polarization characteristic signal and the second polarization characteristic signal corresponding to each focused spot position. The computer composes a position matrix with the real-time position data of the two-dimensional galvanometer in each adjustment state, and generates a two-dimensional distribution map of the first polarization characteristic signal, a two-dimensional distribution map of the second polarization characteristic signal, a fluorescence intensity distribution map, and a two-dimensional distribution map of the polarization ratio based on the position matrix and the first polarization characteristic signal, the second polarization characteristic signal, the fluorescence intensity distribution map, and the polarization ratio. The computer inputs the two-dimensional distribution map of the first polarization characteristic signal, the two-dimensional distribution map of the second polarization characteristic signal, the fluorescence intensity distribution map, the polarization ratio two-dimensional distribution map, and the light intensity distribution map of the laser spot into the graph convolution algorithm for deconvolution operation to obtain a microstructure image.

2. The long-distance, high-resolution fluorescence imaging device according to claim 1, characterized in that: The fluorescence beam collection and detection module includes an achromatic double lens group, which includes a confocal lens group and a pinhole diaphragm. The confocal lens group includes a first lens and a second lens. The pinhole diaphragm is arranged between the first lens and the second lens, and the center of the pinhole diaphragm coincides with the focus of the confocal lens group.

3. The long-distance, high-resolution fluorescence imaging device according to claim 1, characterized in that: The fluorescence beam collection and detection module includes a switchable filtering module, which includes a notch filter, a narrow-pass filter and a switching mirror. The notch filter is used to transmit the wavelength band corresponding to the fluorescence beam, and the narrow-pass filter cooperates with the switching mirror to transmit the wavelength band corresponding to the laser beam.

4. The long-distance, high-resolution fluorescence imaging device according to claim 3, characterized in that: The fluorescence beam collection and detection module includes a polarization beam splitter, a first detector and a second detector. The polarization beam splitter separates the fluorescence beam transmitted by the switchable filter module into two mutually perpendicular polarization state fluorescence beams, and the first detector and the second detector are used to perform photoelectric conversion on the two polarization state fluorescence beams respectively to obtain a first electrical signal and a second electrical signal corresponding to the current focus spot position.

5. The long-distance, high-resolution fluorescence imaging device according to claim 4, characterized in that: If the switchable filter module chooses to transmit the fluorescent beam, a notch filter is used to transmit the wavelength band corresponding to the fluorescent beam, so that the fluorescent beam is incident on the polarization beam splitter through the notch filter; if the switchable filter module chooses to transmit the laser beam, a narrow-pass filter and a switching mirror are used to transmit the wavelength band corresponding to the laser beam, so that the laser beam is incident on the camera through the narrow-pass filter and the switching mirror to obtain a light intensity distribution map.

6. The long-distance, high-resolution fluorescence imaging device according to claim 1, characterized in that: The distance between the protective window of the telecentric field lens assembly and the surface of the object to be measured is between 200 mm and 600 mm.

7. The long-distance, high-resolution fluorescence imaging device according to claim 1, characterized in that: The first detector adopts a photomultiplier tube or a photodiode, and the second detector adopts a photomultiplier tube or a photodiode.

8. The long-distance, high-resolution fluorescence imaging device according to claim 1, characterized in that: The front surface of the object to be measured is located at the focal plane of the telecentric field lens assembly.

9. The long-distance, high-resolution fluorescence imaging device according to claim 1, characterized in that: The preset angle range is: -1°~1°.

10. The long-distance, high-resolution fluorescence imaging device according to claim 1, characterized in that: Constructing a two-dimensional distribution map of the first polarization characteristic signal using the position matrix and the first polarization characteristic signal corresponding to each focused spot position; A fluorescence distribution map is constructed using the position matrix and the fluorescence intensity corresponding to each focused spot position, where the fluorescence intensity corresponding to the current focused spot position is the sum of the first polarization characteristic signal and the second polarization characteristic signal corresponding to the current focused spot position; Constructing a two-dimensional distribution map of the second polarization characteristic signal using the position matrix and the second polarization characteristic signal corresponding to each focused spot position; A two-dimensional distribution diagram of polarization ratios is constructed using the position matrix and the polarization ratios corresponding to each focused spot position. The polarization ratio corresponding to the current focused spot position is the ratio of the difference between the first polarization characteristic signal and the second polarization characteristic signal corresponding to the current focused spot position and the sum of the first polarization characteristic signal and the second polarization characteristic signal corresponding to the current focused spot position.

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