A large field of view high resolution fluorescence microscopic imaging instrument compatible with functional magnetic resonance imaging and application

Abstract

The application relates to the field of fluorescent microscopic imaging technology, and particularly provides a functional magnetic resonance compatible imaging large-field high-resolution fluorescent microscopic imaging instrument and application, the imaging instrument comprises an objective lens, a relay lens unit and a tube lens, the objective lens is used for realizing fluorescence collection and collimation, the relay lens unit is used for replacing a traditional optical fiber bundle to perform long-distance relay transmission of light, and the tube lens focuses parallel light transmitted by the relay lens group on an image sensor to perform imaging. The fluorescent microscopic imaging instrument can perform synchronous fluorescence imaging on a target during functional magnetic resonance imaging, can provide single-cell level resolution under the condition of an 8mm*8mm object field, and the imaging quality is close to the diffraction limit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fluorescence microscopic imaging technology, and particularly provides a large-field high-resolution fluorescence microscopic imaging instrument compatible with functional magnetic resonance imaging and application. BACKGROUND

[0002] Functional magnetic resonance imaging (fMRI) is a non-invasive imaging method that can cover the neural activity of the whole brain of humans and animals. A complete three-dimensional brain neural activity signal can be obtained at one time, which improves our understanding of the structure and function of the brain, and has become an important tool for neuroscientific research. fMRI measures brain neural activity through an indirect method based on blood oxygen level dependence (BOLD), that is, neural activity causes changes in local cerebral hemodynamics, and more oxygenated blood is transported to the area where neural activity is enhanced, which leads to changes in the local magnetic field, affects the diffusion of water molecules around red blood cells, changes their transverse relaxation time, and produces detectable magnetic resonance signals. However, the BOLD signal reflects the complex hemodynamic response of the brain to neuronal activity, and the causal relationship between a certain neurophysiological event and the BOLD signal is not very clear. The exploration of this problem has always been a very active research field in neuroscience.

[0003] In order to understand the relationship between BOLD signal and neuronal activity, a multi-modal method is needed to record BOLD signal and neuronal activity at the same time. In recent years, with the discovery and continuous development of genetically encoded calcium ion indicators (GECIs), fluorescence microscopic imaging technology has been widely used to observe neuronal activity in the brains of living animals due to its advantages of high resolution, high imaging speed, non-invasiveness and non-toxicity. Therefore, the combination of fluorescence microscopic imaging technology and fMRI technology provides a new method for understanding the causal relationship between BOLD signal and neuronal activity.

[0004] However, the strong magnetic field of several to tens of tesla required during fMRI work usually causes the image sensor used in fluorescence microscopy to be unable to work. The current dual-mode system capable of simultaneously performing fMRI imaging and fluorescence microscopy solves this problem by transmitting optical signals to a remote end through a single optical fiber or an optical fiber bundle. The single-fiber-based method is to implant an optical fiber on the brain of an experimental animal, then transmit the optical signals to a place far enough from the fMRI scanner through the optical fiber, and then use a benchtop fluorescence microscope to perform imaging, so as to avoid the influence of the strong magnetic field on the image sensor. The spatial resolution of this single-fiber-based method is relatively poor, and it is usually unable to distinguish individual neurons, and the imaging field of view is limited by the diameter of the optical fiber (usually between 60-400 μm), and the number of observable neurons is very limited. The optical fiber bundle-based method is to use a microscope objective to image neurons, and then transmit the image generated by the objective to a place far from the fMRI scanner through an optical fiber bundle, and then received and recorded by an image sensor. This optical fiber bundle-based method can only achieve a large field of view or high resolution alone, because if both are to be achieved, a larger number of optical fibers with smaller diameters are required, which has very high requirements for the production and manufacture of the optical fiber bundle. SUMMARY

[0005] To solve the above problems, the application provides a large-field high-resolution fluorescence microscope compatible with functional magnetic resonance imaging, which uses multiple relay lenses instead of an optical fiber bundle to relay and transmit light over a long distance, and optimally designs the objective lens and the tube lens. The application of the imaging instrument to synchronous fluorescence imaging during functional magnetic resonance imaging has an optical field of view of 8mmx8mm and single-cell resolution, solving the problem that existing imaging instruments cannot simultaneously achieve a large field of view and high resolution.

[0006] The large-field high-resolution fluorescence microscope compatible with functional magnetic resonance imaging comprises an excitation light source and an image sensor, and an objective lens, a relay lens unit and a tube lens arranged in sequence along an optical axis.

[0007] The objective lens comprises a dichroic mirror and a first lens group, the dichroic mirror has a transmission effect on excitation light of the excitation light source and a reflection effect on fluorescence generated by the excitation target irradiated by the excitation light, and the first lens group processes the fluorescence into parallel light.

[0008] The relay lens unit is an afocal optical path with an angular magnification of-1, and the relay lens unit comprises at least one group of relay lenses, each group of relay lenses comprises two pieces of symmetrically placed image-side telecentric doublet lenses, and the relay lens unit still emits parallel light out of the parallel light emitted in.

[0009] The tube lens is used to focus the parallel light emitted by the relay lens unit onto the image sensor for imaging.

[0010] Preferably, the dichroic mirror is placed at an angle of 45° with the optical axis, and the excitation light generated by the excitation light source is transmitted to the dichroic mirror through the optical fiber.

[0011] Preferably, the first lens group comprises, in sequence along the optical axis: a first lens, a second lens, a third lens, and a fourth lens.

[0012] The first lens is a positive-power spherical lens, the front surface of which is a convex spherical surface, and the rear surface of which is a convex spherical surface.

[0013] The second lens is a negative-power spherical lens, the front surface of which is a concave spherical surface, and the rear surface of which is a plane.

[0014] The third lens is a negative-power spherical lens, the front surface of which is a concave spherical surface, and the rear surface of which is a concave spherical surface.

[0015] The fourth lens is a positive-power spherical lens, the front surface of which is a concave spherical surface, and the rear surface of which is a convex spherical surface.

[0016] Preferably, the relay lens unit comprises two groups of relay lenses, each group of relay lenses comprising a first image-side telecentric doublet lens and a second image-side telecentric doublet lens.

[0017] The first image-side telecentric doublet lens comprises a fifth lens and a sixth lens, the front surface of the fifth lens being a convex spherical surface, and the rear surface of the fifth lens being a concave spherical surface; the front surface of the sixth lens being a convex spherical surface, and the rear surface of the sixth lens being a convex spherical surface.

[0018] The second image-side telecentric doublet lens comprises a seventh lens and an eighth lens, the front surface of the seventh lens being a convex spherical surface, and the rear surface of the seventh lens being a convex spherical surface; the front surface of the eighth lens being a concave spherical surface, and the rear surface of the eighth lens being a convex spherical surface.

[0019] Preferably, each group of relay lenses can relay and transmit 500 mm of parallel light.

[0020] Preferably, the tube lens comprises, in sequence along the optical axis: a plane band-pass filter and a second lens group, the plane band-pass filter performing spectral selection on the incident parallel light, and the second lens group focusing the incident parallel light onto the image sensor.

[0021] Preferably, the second lens group comprises, in sequence along the optical axis: a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens.

[0022] The ninth lens is a positive-power spherical lens, the front surface of which is a convex spherical surface, and the rear surface of which is a concave spherical surface.

[0023] The tenth lens is a negative-power spherical lens, the front surface of which is a concave spherical surface, and the rear surface of which is a concave spherical surface.

[0024] The eleventh lens is a positive focal length spherical lens, the front surface of which is a convex spherical surface, and the rear surface of which is a convex spherical surface;

[0025] The twelfth lens is a positive focal length spherical lens, the front surface of which is a convex spherical surface, and the rear surface of which is a convex spherical surface;

[0026] The thirteenth lens is a negative focal length spherical lens, the front surface of which is a concave spherical surface, and the rear surface of which is a concave spherical surface.

[0027] Preferably, the spectrum of the plane band-pass filter is one band-pass spectrum or multiple band-pass spectra.

[0028] Preferably, the rear surface of the fourth lens is provided with a diaphragm.

[0029] The application of the large-view-field high-resolution fluorescence microscopic imaging instrument compatible with functional magnetic resonance imaging places the excitation light source and the image sensor in an electromagnetic shielding device, places the objective lens and the fluorescence imaging target in the nuclear magnetic resonance imaging instrument, transmits the excitation light generated by the excitation light source to the objective lens through an optical fiber, transmits the excitation light through the dichroic mirror to irradiate the fluorescence imaging target, reflects the fluorescence generated by the fluorescence imaging target into the first lens group through the dichroic mirror, processes the fluorescence into parallel light by the first lens group, transmits the parallel light into the relay lens unit, and still transmits the parallel light into the tube lens, focuses the parallel light emitted by the relay lens unit on the image sensor, and realizes fluorescence imaging during functional magnetic resonance imaging.

[0030] Compared with the prior art, the application can achieve the following beneficial effects:

[0031] The application relays and transmits fluorescence imaging light by using multiple relay lens groups, avoids the influence of the strong magnetic field generated by functional magnetic resonance imaging on fluorescence imaging, solves the problem that there is mutual restriction between the field of view and the resolution when optical fibers are used to transmit light, and realizes fluorescence imaging of the target during functional magnetic resonance imaging, realizes multi-modal imaging of the target, provides single-cell-level resolution under the condition of an 8mm*8mm object field of view, and has close-to-diffraction-limit imaging quality and extremely high imaging accuracy.

[0032] The application can image and observe the neural activity of the cerebral cortex of an animal at single-cell resolution under the condition of a large field of view, can flexibly adjust the distance of parallel light relay transmission by adjusting the number of relay lens groups, and meets different experimental requirements, which has a positive significance for studying the causal relationship between neurophysiological events and BOLD signals.

[0033] In addition, the objective lens and the tube lens are specially designed, the imaging light path and the illumination light path adopt the common light path design, the dichroic mirror at the front end of the objective lens is used for light splitting, and mutual interference of the excitation light and the fluorescence is avoided; the relay lens adopts the completely same double cemented lenses which are symmetrically arranged, the machining cost of the lens is reduced, the light path structure is simplified, and the assembling and adjusting difficulty is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a principle schematic view of a large-view-field high-resolution fluorescence microscopic imaging instrument compatible with functional magnetic resonance imaging according to an embodiment of the application;

[0035] Figure 2 is an optical structure schematic view of an objective lens according to an embodiment of the application;

[0036] Figure 3 is an optical structure schematic view of a first group of relay lenses according to an embodiment of the application;

[0037] Figure 4 is an optical structure schematic view of a second group of relay lenses according to an embodiment of the application;

[0038] Figure 5 is an optical structure schematic view of a tube lens according to an embodiment of the application;

[0039] Figure 6 is an MTF curve diagram of the large-view-field high-resolution fluorescence microscopic imaging instrument compatible with functional magnetic resonance imaging.

[0040] The reference signs in the drawings include:

[0041] objective lens 1, dichroic mirror 11, first lens 12, second lens 13, third lens 14, and fourth lens 15;

[0042] diaphragm 2, first group of relay lenses 3, fifth lens 31, sixth lens 32, seventh lens 33, and eighth lens 34;

[0043] second group of relay lenses 4, fifth lens 41, sixth lens 42, seventh lens 43, and eighth lens 44;

[0044] tube lens 5, planar band-pass filter 51, ninth lens 52, tenth lens 53, eleventh lens 54, twelfth lens 55, and thirteenth lens 56;

[0045] excitation light source 6, image sensor 7, nuclear magnetic resonance imaging instrument 8, electromagnetic shielding device 9, and optical fiber 10. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0047] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying 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 a limitation on the present application.

[0048] As shown in Figure 1 The compatible functional magnetic resonance imaging large field of view high resolution fluorescence microscopic imaging instrument provided by the embodiment of the present application mainly consists of an objective lens 1, a relay lens unit, a tube lens 5, an excitation light source 6 and an image sensor 7. The fluorescence microscopic imaging instrument can be applied to synchronous fluorescence imaging of a target during functional magnetic resonance imaging. The optical elements in the objective lens 1, the relay lens unit and the tube lens 5 are all glass spherical lenses and are arranged on the same optical axis. The arrangement order of the objective lens 1, the relay lens unit and the tube lens 5 along the optical axis from the object plane to the image plane is: the objective lens 1, the relay lens unit and the tube lens 5.

[0049] The objective lens 1 mainly includes a dichroic mirror 11 and a first lens group. It is mainly used for collecting fluorescence generated by the fluorescence imaging target due to the irradiation of the excitation light. In the present embodiment, the fluorescence imaging target is a mouse. During functional magnetic resonance imaging, the mouse and the objective lens 1 are arranged in a nuclear magnetic resonance imaging instrument 8. The excitation light source 6 and the image sensor 7 are arranged in an electromagnetic shielding device 9. The excitation light emitted by the excitation light source 6 is transmitted to the upper side of the dichroic mirror 11 by using an optical fiber 10. The excitation light transmits through the dichroic mirror 11 and is vertically irradiated on the cerebral cortex of the mouse. The excitation light of a specific wave band can excite the cerebral cortex of the mouse to emit light. The optical fiber 10 is a commonly used super flexible optical fiber. Since the surface of the dichroic mirror 11 is coated with a thin film, it only has a specific effect on the excitation light of a specific wave band, and has a reflection effect on the fluorescence generated by the excitation. Figure 2As shown, the dichroic mirror 11 is placed at a 45-degree angle relative to the optical axis. Therefore, the dichroic mirror 11 can refract the propagation direction of fluorescence by 90 degrees. After being reflected by the dichroic mirror 11, the fluorescence passes sequentially through the four spherical lenses in the first lens group, collimating the diverging fluorescence into parallel light. The first lens group includes a first lens 12, a second lens 13, a third lens 14, and a fourth lens 15 arranged sequentially along the optical axis. Among them, the first lens 12, which is closer to the mouse, is a positive power spherical lens made of H-ZLAF69A material. The front and rear surfaces of the first lens 12 are both convex spherical. The second lens 13 is a negative power spherical lens made of H-F4 material. The front and rear surfaces of the second lens 13 are both concave spherical. The third lens 14 is a negative power spherical lens made of H-ZF11 material. The front and rear surfaces of the third lens 14 are both concave spherical. The fourth lens 15 is a positive power spherical lens made of H-ZLAF69A material. The front surface of the fourth lens 15 is concave spherical, and the rear surface is convex spherical. In addition, an aperture 2 is provided on the rear surface of the fourth lens 15. After being processed by the objective lens 1, the fluorescence is converted into parallel light and emitted through the aperture 2.

[0050] In this embodiment of the invention, a relay lens unit is used instead of traditional optical fiber transmission. The relay lens unit is set in the subsequent optical path of objective lens 1. The relay lens unit is an afocal optical path with an angular magnification of -1. The parallel light emitted from objective lens 1 can be relayed and transmitted, and then emitted as parallel light again.

[0051] In this embodiment of the invention, the relay lens unit includes two sets of relay lenses, namely a first set of relay lenses 3 and a second set of relay lenses 4, as shown below. Figure 3 and 4 As shown, the first set of relay lenses 3 and the second set of relay lenses 4 have identical structures and optical elements, both consisting of two symmetrically placed image-side telecentric cemented doublet lenses. Both sets of relay lenses 3 and 4 include four spherical lenses. Each set of relay lenses can relay parallel light over a distance of 500mm. This invention uses two sets of relay lenses, enabling relay transmission of parallel light over a distance of 1000mm. The number of relay lenses can be flexibly adjusted according to actual needs and application scenarios, improving the flexibility of the fluorescence microscopy imager of this invention.

[0052] like Figure 3As shown, the first group of relay lenses 3 includes, in order along the optical axis: a fifth lens 31, a sixth lens 32, a seventh lens 33, and an eighth lens 34, the fifth lens 31 and the sixth lens 32 constitute a first image-side telecentric doublet, the seventh lens 33 and the eighth lens 34 constitute a second image-side telecentric doublet, wherein the fifth lens 31 close to the mouse side is a negative power spherical lens, the material is H-ZLAF90, the front surface of the fifth lens 31 is a convex spherical surface, and the rear surface is a concave spherical surface. The sixth lens 32 is a positive power spherical lens, the material is H-ZLAF55D, the front surface of the sixth lens 32 is a convex spherical surface, and the rear surface is also a convex spherical surface. The seventh lens 33 is a positive power spherical lens, the material is H-ZLAF55D, the front surface of the seventh lens 33 is a convex spherical surface, and the rear surface is also a convex spherical surface. The eighth lens 34 is a negative power spherical lens, the material is H-ZLAF90, the front surface of the eighth lens 34 is a concave spherical surface, and the rear surface is a convex spherical surface.

[0053] As shown in Figure 4 The second group of relay lenses 4 is completely the same as the first group of relay lenses 3, and the second group of relay lenses 4 includes, in order along the optical axis: a fifth lens 41, a sixth lens 42, a seventh lens 43, and an eighth lens 44, the fifth lens 41 and the sixth lens 42 constitute a first image-side telecentric doublet, the seventh lens 43 and the eighth lens 44 constitute a second image-side telecentric doublet, wherein the fifth lens 41 close to the mouse side is a negative power spherical lens, the material is H-ZLAF90, the front surface of the fifth lens 41 is a convex spherical surface, and the rear surface is a concave spherical surface. The sixth lens 42 is a positive power spherical lens, the material is H-ZLAF55D, the front surface of the sixth lens 42 is a convex spherical surface, and the rear surface is also a convex spherical surface. The seventh lens 43 is a positive power spherical lens, the material is H-ZLAF55D, the front surface of the seventh lens 43 is a convex spherical surface, and the rear surface is also a convex spherical surface. The eighth lens 44 is a negative power spherical lens, the material is H-ZLAF90, the front surface of the eighth lens 44 is a concave spherical surface, and the rear surface is a convex spherical surface.

[0054] The parallel light still exits as parallel light after passing through the first group of relay lenses 3 and the second group of relay lenses 4, and enters the tube lens 5 for focusing. As shown in Figure 5As shown, the tube lens 5 includes a flat band-pass filter 51 and a second lens group, which includes, in order along the optical axis, a ninth lens 52, a tenth lens 53, an eleventh lens 54, a twelfth lens 55, and a thirteenth lens 56. The flat band-pass filter 51 is used for spectral selection of the incident parallel light, and the spectrum can be one band-pass spectrum, such as 525nm±50nm, or multiple discrete band-pass spectra, such as 525nm±25nm and 600nm±25nm, or other spectra. The parallel light emitted by the relay lens unit first passes through the flat band-pass filter 51 for spectral selection, and then passes through the five spherical lenses to convert the parallel light into a converging light beam. The focused light is focused onto the target surface of the image sensor 7 in the electromagnetic shielding device 9 through the image sensor window glass. The ninth lens 52 near the mouse side is a positive focal power spherical lens, and the material is H-LAK52. The front surface of the ninth lens 52 is a convex spherical surface, and the rear surface is a concave spherical surface. The tenth lens 53 is a negative focal power spherical lens, and the material is H-ZF11. The front surface of the tenth lens 53 is a concave spherical surface, and the rear surface is also a concave spherical surface. The eleventh lens 54 is a positive focal power spherical lens, and the material is H-LAK52. The front surface of the eleventh lens 54 is a convex spherical surface, and the rear surface is a convex spherical surface. The twelfth lens 55 is a positive focal power spherical lens, and the material is H-ZPK1A. The front surface of the twelfth lens 55 is a convex spherical surface, and the rear surface is also a convex spherical surface. The thirteenth lens 56 is a negative focal power spherical lens, and the material is H-ZLAF90. The front surface of the thirteenth lens 56 is a concave spherical surface, and the rear surface is also a concave spherical surface.

[0055] The parameters of the optical elements in the above objective lens 1, first relay lens 3, second relay lens 4, and tube lens 5 are as follows:

[0056] Table 1 Optical element parameter table

[0057]

[0058]

[0059]

[0060] It should be noted that the above table is computer software output data, wherein "+" (omitted) or "-" in front of the radius of curvature refers to the concave-convex condition of each surface of the optical element relative to an object reference surface, and is not relative to the concave-convex condition of the optical element itself. For example, the first lens 12 is a biconvex spherical lens, and the radii of curvature of the front and rear surfaces should be positive relative to itself, but the concave-convex condition of the optical element itself in the computer software is based on the object reference surface. The front surface of the first lens 12 is convex relative to the object reference surface, so the front surface of the first lens 12 is 17.7, and the rear surface of the first lens 12 is concave relative to the object reference surface, so the rear surface of the first lens 12 is -15.58. The radii of curvature of other optical elements are the same.

[0061] The above-mentioned large-field high-resolution fluorescence microscope imaging instrument compatible with functional magnetic resonance imaging has completed the development of a product prototype, and the theoretical and design verification is feasible. The working waveband of the prototype is 500 nm-550 nm, the object numerical aperture (NA) is 0.1, the relay transmission distance is 1 m; the image element size of the image sensor 7 is 2.2 μm x 2.2 μm; the pixel number is 2592 x 1944; the object field of view is 8 mm x 8 mm, and the magnification is 0.6 times. The modulation transfer function (MTF) curve shown in Figure 6 It can be seen from the curve that at the cut-off frequency of the image sensor 7, the MTF of each field of view is close to the diffraction limit, and the imaging quality is good. The large-field high-resolution fluorescence imaging can be performed synchronously during functional magnetic resonance imaging, and under the condition of a field of view of 8 mm x 8 mm, single-cell resolution imaging can be achieved.

[0062] The above-mentioned fluorescence microscope imaging instrument is applied during functional magnetic resonance imaging, and the process of synchronously performing fluorescence imaging on the cerebral cortex of a mouse is as follows:

[0063] As shown in Figure 1As shown, the mouse and the objective 1 are placed in the nuclear magnetic resonance imaging instrument 8, and the excitation light source 6 and the image sensor 7 are arranged in the electromagnetic shielding device 9. During the functional magnetic resonance imaging process, for the illumination light path, considering the influence of the strong magnetic field on the electronic device, the embodiment of the application places the excitation light source 6 and the image sensor 7 in the same electromagnetic shielding device 9, turns on the excitation light source 6, the excitation light source 6 emits excitation light of a specific wave band, the excitation light is transmitted to the upper side of the dichroic mirror 11 through the optical fiber 10, the dichroic mirror 11 is arranged directly above the mouse head and forms a 45-degree angle with the optical axis, the excitation light transmits through the dichroic mirror 11 and irradiates the cerebral cortex of the mouse, and the excitation light excites the fluorescent substance in the cerebral cortex to emit light. The fluorescence emitted by the cerebral cortex of the mouse is reflected by the dichroic mirror of the objective 1 into the first lens group, and the first lens group processes the fluorescence into parallel light; the parallel light enters the first relay lens group 3 and the second relay lens group 4 in sequence for relay transmission, and still exits as parallel light and enters the tube lens 5, the tube lens 5 focuses the parallel light emitted by the second relay lens group 4 through the image sensor window glass on the image sensor 7 in the electromagnetic shielding device 9, completes the fluorescence imaging during the functional magnetic resonance imaging process, converts the optical signal into an electrical signal, and processes the electrical signal through the subsequent electronic circuit.

[0064] The above-mentioned fluorescence imaging process includes an illumination light path and an imaging light path, and the common light path design of the illumination light path and the imaging light path is realized through the dichroic mirror 11, and mutual interference of the two light paths is avoided.

[0065] Although the embodiments of the application have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the application. Those skilled in the art can make changes, modifications, replacements and variations to the above-mentioned embodiments within the scope of the application.

[0066] The specific embodiments of the application described above do not constitute a limitation on the protection scope of the application. Any various other corresponding changes and modifications made according to the technical concept of the application should be included in the protection scope of the claims of the application.

Claims

1. A large field-of-view, high-resolution fluorescence microscopy imager compatible with functional magnetic resonance imaging, comprising: An excitation light source and an image sensor, characterized in that the excitation light source and the image sensor are disposed within an electromagnetic shielding device; it also includes, arranged sequentially along the optical axis: an objective lens, a relay lens unit, and a tube lens; The objective lens includes a dichroic mirror and a first lens group. The excitation light generated by the excitation source is transmitted to the dichroic mirror through an optical fiber. The dichroic mirror transmits the excitation light from the excitation source and reflects the fluorescence generated by the excitation light illuminating the target. The fluorescence is reflected by the dichroic mirror into the first lens group, which processes the fluorescence into parallel light. The relay lens unit is a focalless optical path with an angular magnification of -1. The relay lens unit includes at least one set of relay lenses, each set of relay lenses consisting of two symmetrically placed image-side telecentric cemented doublet lenses; the relay lens unit will still output parallel light as if it were incident parallel light. The tube lens is used to focus the parallel light emitted by the relay lens unit onto the image sensor for imaging.

2. The large field-of-view, high-resolution fluorescence microscopy imager compatible with functional magnetic resonance imaging as described in claim 1, characterized in that, The dichroic mirror is placed at a 45° angle to the optical axis, and the excitation light generated by the excitation source is transmitted to the dichroic mirror through an optical fiber.

3. The large field-of-view, high-resolution fluorescence microscopy imager compatible with functional magnetic resonance imaging as described in claim 1, characterized in that, The first lens group includes a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis; The first lens is a positive power spherical lens, with its front surface being a convex spherical surface and its rear surface being a convex spherical surface; The second lens is a negative power spherical lens, with a concave spherical front surface and a flat rear surface; The third lens is a negative power spherical lens, with a concave spherical front surface and a concave spherical rear surface. The fourth lens is a positive power spherical lens, with a concave spherical surface on the front surface and a convex spherical surface on the rear surface.

4. The large field-of-view, high-resolution fluorescence microscopy imager compatible with functional magnetic resonance imaging as described in claim 1, characterized in that, The relay lens unit includes two sets of relay lenses, each set of relay lenses including a first image-side telecentric cemented doublet lens and a second image-side telecentric cemented doublet lens; The first image-side telecentric cemented doublet lens includes a fifth lens and a sixth lens. The front surface of the fifth lens is a convex spherical surface and the rear surface is a concave spherical surface; the front surface of the sixth lens is a convex spherical surface and the rear surface is a convex spherical surface. The second image-side telecentric cemented doublet includes a seventh lens and an eighth lens. The front surface of the seventh lens is a convex spherical surface, and the rear surface is a convex spherical surface. The front surface of the eighth lens is a concave spherical surface, and the rear surface is a convex spherical surface.

5. The large field-of-view, high-resolution fluorescence microscopy imager compatible with functional magnetic resonance imaging as described in claim 4, characterized in that, Each relay lens can relay parallel light up to 500mm.

6. The large field-of-view, high-resolution fluorescence microscopy imager compatible with functional magnetic resonance imaging as described in claim 1, characterized in that, The tube lens includes a planar bandpass filter and a second lens group arranged sequentially along the optical axis. The planar bandpass filter performs spectral selection on the incident parallel light, and the second lens group focuses the incident parallel light onto the image sensor.

7. The large field-of-view, high-resolution fluorescence microscopy imager compatible with functional magnetic resonance imaging as described in claim 6, characterized in that, The second lens group includes, in sequence along the optical axis, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens; The ninth lens is a positive power spherical lens, with a convex spherical surface on the front surface and a concave spherical surface on the rear surface; The tenth lens is a negative power spherical lens, with a concave spherical front surface and a concave spherical rear surface. The eleventh lens is a positive power spherical lens, with a convex spherical front surface and a convex spherical rear surface. The twelfth lens is a positive power spherical lens, with a convex spherical surface on its front surface and a convex spherical surface on its rear surface; The thirteenth lens is a negative power spherical lens, with a concave spherical front surface and a concave spherical rear surface.

8. The large field-of-view, high-resolution fluorescence microscopy imager compatible with functional magnetic resonance imaging as described in claim 6, characterized in that, The spectrum of the planar bandpass filter is one bandpass or multiple bandpass bands.

9. The large field-of-view, high-resolution fluorescence microscopy imager compatible with functional magnetic resonance imaging as described in claim 3, characterized in that, The rear surface of the fourth lens is provided with an aperture stop.

10. An application of a large field-of-view, high-resolution fluorescence microscopy imager compatible with functional magnetic resonance imaging as described in any one of claims 1 to 9, characterized in that, The excitation light source and the image sensor are placed inside an electromagnetic shielding device, and the objective lens and the fluorescence imaging target are placed inside a nuclear magnetic resonance imaging (fMRI) scanner. The excitation light generated by the excitation light source is transmitted to the objective lens via an optical fiber. The excitation light is transmitted through the dichroic mirror to illuminate the fluorescence imaging target. The fluorescence generated by the fluorescence imaging target is reflected by the dichroic mirror and enters the first lens group. The first lens group processes the fluorescence into parallel light. The parallel light is transmitted into the relay lens unit and then enters the tube mirror as parallel light. The tube mirror focuses the parallel light emitted from the relay lens unit onto the image sensor, thereby achieving fluorescence imaging during functional magnetic resonance imaging (fMRI).

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