Long working distance short cavity ultraviolet fluorescence imaging system

Abstract

This invention discloses a short-cavity ultraviolet fluorescence imaging system with a long working distance, comprising a lens sleeve, and further comprising a first positive meniscus lens, a first plano-convex lens, a second positive meniscus lens, a third positive meniscus lens, a plano-concave lens, and a second plano-convex lens, which are sequentially arranged coaxially within the lens sleeve along the fluorescence imaging direction. Along the fluorescence imaging direction, the two sides of the first positive meniscus lens are concave and convex, respectively; the two sides of the first plano-convex lens are planar and convex, respectively; the two sides of the second positive meniscus lens are convex and concave, respectively; the two sides of the third positive meniscus lens are convex and concave, respectively; the two sides of the plano-concave lens are concave and planar, respectively; and the two sides of the second plano-convex lens are convex and planar, respectively. This invention achieves a long working distance, high resolution, and compact ultraviolet imaging system through the combination of a spherical lens and a microscope. Compared to existing spherical lens systems, the optical path is significantly reduced, and compared to aspherical lens systems, the cost is lower.

Description

Technical Field

[0001] This invention relates to a short-cavity ultraviolet fluorescence imaging system based on a spherical mirror, specifically a short-cavity ultraviolet fluorescence imaging system with a long working distance, which can be used for the collection and imaging of ultraviolet fluorescence, and is particularly suitable for single-ion resolution imaging in ion trap quantum computing and high ionization state ion clock research. Background Technology

[0002] Optical clocks, with their exceptional time and frequency accuracy, have not only provided a new standard for redefining the second but also demonstrated significant value in cutting-edge fundamental science fields such as the study of time-varying fundamental physical constants and dark matter detection. Among these, highly charged ions (HCIs), as candidate systems for next-generation optical clocks, are primarily studied using trapped ion technology. This technology achieves three-dimensional trapping of ions through a combined AC / DC electric field and has developed into several mature systems, widely applied in laser spectroscopy, quantum computing, and quantum information, powerfully promoting the interdisciplinary development of fundamental physics, quantum physics, and particle physics. In these studies, high-resolution single-ion fluorescence imaging plays a central role, providing crucial technical support for optimizing optical clock stability and quantum logic operations through precise monitoring of the quantum state, spatial position, and motion of individual ions.

[0003] Existing ultraviolet fluorescence imaging systems mainly employ the following technical solutions: aspherical mirror imaging systems, hybrid imaging systems combining spherical and aspherical mirrors, commercially available spherical mirror combination systems, and microscope imaging systems. Among these, while aspherical mirror systems can achieve high resolution, they suffer from complex design and high manufacturing costs; hybrid imaging systems also face challenges of high design difficulty and cost; commercially available spherical mirror systems cannot accommodate long object distances and short image distances, resulting in bulky systems; and microscope systems, due to their excessively short object distances, are insufficient to meet experimental requirements. For example, the Max Planck Institute for Nuclear Physics in Germany... 13+ Be used in optical clock research + The ultraviolet imaging system achieves a working distance of 150mm through the combination of multiple aspherical mirrors, obtaining high transmittance in the 313nm ultraviolet band and effectively suppressing chromatic aberration and monochromatic aberration. This design utilizes the complex curved surface characteristics of aspherical mirrors to reduce the number of optical components, but requires extremely high processing and assembly precision, resulting in very high costs. Furthermore, at low temperatures (4K), material thermal shrinkage may cause mirror deformation, affecting imaging stability. Although domestic research teams have made progress in aspherical mirror design algorithms and nanoscale fabrication technology, the overall solution still suffers from high complexity and low cost-effectiveness, hindering technology promotion. Therefore, developing a compact, high-resolution imaging system based on spherical mirrors has become a critical technical problem urgently needing to be solved. Utility Model Content

[0004] This invention addresses the aforementioned problems in existing technologies by proposing a short-cavity ultraviolet fluorescence imaging system with a long working distance. Through a combination of a spherical lens and a microscope, it achieves a long working distance (≥60mm), high resolution (≤5μm), and compact size (total length ≤300mm) ultraviolet imaging system, resulting in lower costs compared to aspherical mirror systems. Given the widespread use of 313nm wavelength imaging in practice, this invention is most suitable for 313nm wavelength ultraviolet light imaging.

[0005] To achieve the above objectives, this utility model is implemented through the following technical solution: A short-cavity ultraviolet fluorescence imaging system with a long working distance includes a lens sleeve and a first positive meniscus lens, a first plano-convex lens, a second positive meniscus lens, a third positive meniscus lens, a plano-concave lens, and a second plano-convex lens arranged coaxially along the fluorescence imaging direction within the lens sleeve. Along the direction of fluorescence imaging, The first positive meniscus lens has a concave surface and a convex surface on its two sides, respectively. The first plano-convex lens has a plane and a convex surface on its two sides, respectively. The second positive meniscus lens has a convex surface and a concave surface on its two sides, respectively. The third positive meniscus lens has a convex surface and a concave surface on its two sides; A plano-concave lens has a concave surface and a flat surface on its two sides, respectively. The second plano-convex lens has a convex surface and a flat surface on its two sides, respectively.

[0006] As mentioned above, the center thickness of both the first positive meniscus lens and the first plano-convex lens is 7.84 mm. The center thickness of both the second and third positive meniscus lenses is 5.36 mm. The center thickness of the plano-concave lens is 2.50 mm. The center thickness of the second plano-convex lens is 19.79 mm; The concave and convex radii of curvature of the first positive meniscus lens are -135.25 mm and -46.53 mm, respectively. The radius of curvature of the convex surface of the first plano-convex lens is -69.01 mm. The radii of curvature of the convex and concave surfaces of the second positive meniscus lens are 97.61 mm and 327.59 mm, respectively. The radii of curvature of the convex and concave surfaces of the third positive meniscus lens are 97.61 mm and 327.59 mm, respectively. The radius of curvature of the concave surface of the plano-concave lens is -45.90 mm. The radius of curvature of the convex surface of the second plano-convex lens is 27.60 mm.

[0007] As described above, the center distance between the convex surface of the first positive meniscus lens and the plane of the first plano-convex lens is 13.088 mm. The convex surface of the first plano-convex lens is tangent to the convex surface of the second positive meniscus lens. The concave surface of the second positive meniscus lens is tangent to the convex surface of the third positive meniscus lens. The center distance between the concave surfaces of the third positive meniscus lens and the concave surfaces of the plano lens is 46.508 mm. The center distance between the plane of the plano-concave lens and the convex surface of the second plano-convex lens is 110.00 mm.

[0008] As described above, the refractive index of the first positive meniscus lens, the first plano-convex lens, the second positive meniscus lens, the third positive meniscus lens, the plano-concave lens, and the second plano-convex lens for 313nm fluorescence is 1.458.

[0009] As mentioned above, the first positive meniscus lens, the first plano-convex lens, the second positive meniscus lens, the third positive meniscus lens, the plano-concave lens, and the second plano-convex lens are made of fused silica.

[0010] As described above, both surfaces of the first positive meniscus lens, the first plano-convex lens, the plano-concave lens, and the second plano-convex lens are coated with anti-reflection films with an anti-reflection wavelength of 245-400nm, and the anti-reflection film of the plano-concave lens has an anti-reflection wavelength of 245-440nm.

[0011] As described above, the lens sleeve is also provided with a first lens retaining ring, a second lens retaining ring, a third lens retaining ring, a fourth lens retaining ring, a fifth lens retaining ring, a sixth lens retaining ring, a seventh lens retaining ring, and an eighth lens retaining ring; The first positive meniscus lens is positioned between the first lens retainer and the second lens retainer. The first plano-convex lens, the second positive meniscus lens, and the third positive meniscus lens are positioned between the third lens retainer and the fourth lens retainer. The plano-concave lens is positioned between the fifth lens retainer and the sixth lens retainer. The second plano-convex lens is positioned between the seventh lens retainer and the eighth lens retainer.

[0012] As described above, the first lens retainer, second lens retainer, third lens retainer, fourth lens retainer, fifth lens retainer, sixth lens retainer, seventh lens retainer, and eighth lens retainer are all circumferentially provided with external threads that are compatible with the internal threads inside the lens sleeve.

[0013] Compared with the prior art, this utility model has the following advantages: The spherical lenses used in this invention are a standard 150mm focal length first positive meniscus lens, a 150mm focal length first plano-convex lens, a 300mm focal length second positive meniscus lens and a third positive meniscus lens, a -100mm focal length plano-concave lens and a 60mm focal length second plano-convex lens, and the materials are easy to obtain and process.

[0014] The spherical mirror surface function used in this invention is simple and easy to process with high precision.

[0015] This invention features a long working distance, specifically a working distance of 66.367 mm between the lens sleeve surface and the imaging object. When applied to actual imaging, the entire optical path is short. Existing commercial spherical mirror assemblies use 1000mm focal length plano-convex lenses, with a similar working distance of ≥60mm, but a total optical path length >1300mm. This invention, with a working distance ≥60mm, has a total optical path length of 280.104mm (including working distance and image distance), significantly reducing the overall optical path length, avoiding excessively long optical paths, facilitating setup and adjustment, and allowing for integration with microscopes to achieve various magnifications.

[0016] This invention can be used in conjunction with microscope objectives to improve the paraxial and angular magnification of the system. Different microscope objectives with different magnifications can achieve different paraxial and angular magnifications. With the addition of microscope objectives, the working distance of the objectives is less than 10mm, the microscope and system are coaxially aligned, the optical path is simple, and the overall optical path remains compact. This invention significantly improves the working distance compared to traditional microscope imaging systems, where the object distance is typically 5-10mm, which cannot meet experimental requirements.

[0017] This invention uses a slotted lens barrel, which makes it easy to determine and adjust the position of the lens.

[0018] Furthermore, the second plano-convex lens of this invention uses a 60mm focal length plano-convex lens to achieve a paraxial magnification of 1.475 times and an angular magnification of 1.508 times for the imaging system.

[0019] In this invention, most lenses are coated with a 245-400nm antireflection film on both sides, resulting in a fluorescence transmittance of over 80% and a resolution of 5μm. The first positive meniscus lens, the first plano-convex lens, and the second plano-convex lens are coated with a 245-400nm antireflection film, while the plano-concave lens is coated with a 245-440nm antireflection film, enabling high fluorescence transmittance across multiple wavelengths.

[0020] This invention employs the aberration correction principle, resulting in high imaging resolution. When the OTF modulus is 0.2, the corresponding spatial frequency is 844.2 lp / mm. Paraxial object imaging is close to the diffraction limit, with an Airy radius of 0.919 μm.

[0021] The first positive meniscus lens, the first plano-convex lens, the second positive meniscus lens, the third positive meniscus lens, the plano-concave lens, and the second plano-convex lens of this utility model are 2-inch spherical mirrors with a large potential field and an object space numerical aperture NA of 0.3.

[0022] The lens sleeve used in this invention is made of aluminum alloy, and the interior is treated with black anodizing to reduce stray light.

[0023] This invention allows for the selection of lenses with different focal lengths as the second plano-convex lens, resulting in different magnifications, changes in image distance, and changes in optical path length.

[0024] This invention is compatible with multiple wavelengths and is suitable for imaging at various wavelengths. The above data are based on a 313nm wavelength. For other wavelengths, the working distance and image distance will change. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view of the short-cavity ultraviolet fluorescence imaging system of this utility model, in which a groove is provided on the inner wall of the lens barrel to facilitate accurate adjustment of the lens position.

[0026] Figure 2 This is a schematic diagram of an embodiment of the present invention, showing the coaxial configuration of a microscope and a short-cavity ultraviolet fluorescence imaging system.

[0027] Figure 3 This is a light path diagram simulating the application of this utility model. The light passes through a short-cavity ultraviolet fluorescence imaging system for a first image, and then passes through a microscope for a second image.

[0028] Figure 4 The image obtained after testing the imaging of this invention using a 1951 USAF resolution test target (3 inches x 3 inches).

[0029] Figure 5 This is the MTF curve of the coaxial imaging system of the detector of this utility model. MTF is the modulation transfer function, which is dimensionless; OTF is the optical transfer function, and the magnitude of OTF is the modulation transfer function MTF.

[0030] In the diagram: 1. Lens sleeve, 2. First lens retainer, 3. First positive meniscus lens, 4. Second lens retainer, 5. Third lens retainer, 6. First plano-convex lens, 7. Second positive meniscus lens, 8. Third positive meniscus lens, 9. Fourth lens retainer, 10. Fifth lens retainer, 11. Plano-concave lens, 12. Sixth lens retainer, 13. Seventh lens retainer, 14. Second plano-convex lens, 15. Eighth lens retainer, 16. Be + 17. Ions, 18. Vacuum cavity, 19. Short cavity ultraviolet fluorescence imaging system, 20. Microscope, 21. Charge-coupled device. Detailed Implementation

[0031] To facilitate understanding and implementation of this invention by those skilled in the art, the following description, in conjunction with the accompanying drawings and embodiments, and using a 1951 USAF resolution test target (3 inches x 3 inches), further describes the imaging performance of this invention. It should be understood that the embodiments described herein are primarily intended to demonstrate the feasibility of this invention and to illustrate and explain it, and are not intended to limit the scope of this invention.

[0032] Example 1: like Figure 1 and Figure 3 As shown, a short-cavity ultraviolet fluorescence imaging system with a long working distance includes a lens sleeve 1, and further includes a first positive meniscus lens 3, a first plano-convex lens 6, a second positive meniscus lens 7, a third positive meniscus lens 8, a plano-concave lens 11, and a second plano-convex lens 14, which are arranged coaxially along the fluorescence imaging direction within the lens sleeve 1. Along the fluorescence imaging direction, the two sides of the first positive meniscus lens 3 are concave and convex, respectively; the two sides of the first plano-convex lens 6 are planar and convex, respectively; the two sides of the second positive meniscus lens 7 are convex and concave, respectively; the two sides of the third positive meniscus lens 8 are convex and concave, respectively; the two sides of the plano-concave lens 11 are concave and planar, respectively; and the two sides of the second plano-convex lens 14 are convex and planar, respectively.

[0033] The center thickness of the first positive meniscus lens 3 and the first plano-convex lens 6 is 7.84 mm, the center thickness of the second positive meniscus lens 7 and the third positive meniscus lens 8 is 5.36 mm, the center thickness of the plano-concave lens 11 is 2.50 mm, and the center thickness of the second plano-convex lens 14 is 19.79 mm.

[0034] The concave and convex radii of curvature of the first positive meniscus lens 3 are -135.25 mm and -46.53 mm, respectively; the convex radius of curvature of the first plano-convex lens 6 is -69.01 mm; the convex and concave radii of curvature of the second positive meniscus lens 7 are 97.61 mm and 327.59 mm, respectively; the convex and concave radii of curvature of the third positive meniscus lens 8 are 97.61 mm and 327.59 mm, respectively; the concave radius of curvature of the plano-concave lens 11 is -45.90 mm; and the convex radius of curvature of the second plano-convex lens 14 is 27.60 mm. The positive and negative signs of the curvature radius are defined as follows: the direction from the first positive meniscus lens 3 to the second plano-convex lens 14 (i.e., the direction of fluorescence imaging) is taken as the positive direction of the lens. When the center of the spherical surface of the lens is located in the positive direction of the lens (including the first positive meniscus lens 3, the first plano-convex lens 6, the second positive meniscus lens 7, the third positive meniscus lens 8, the plano-concave lens 11, and the second plano-convex lens 14), the curvature radius is positive; when the center of the spherical surface of the lens is located in the negative direction of the lens, the curvature radius is negative.

[0035] The center distance between the convex surface of the first positive meniscus lens 3 and the plane of the first plano-convex lens 6 is 13.088 mm. The convex surface of the first plano-convex lens 6 is tangent to the convex surface of the second positive meniscus lens 7. The concave surface of the second positive meniscus lens 7 is tangent to the convex surface of the third positive meniscus lens 8. The center distance between the concave surface of the third positive meniscus lens 8 and the concave surface of the plano-concave lens 11 is 46.508 mm. The center distance between the plane of the plano-concave lens 11 and the convex surface of the second plano-convex lens 14 is 110.00 mm.

[0036] The first positive meniscus lens 3, the first plano-convex lens 6, the second positive meniscus lens 7, the third positive meniscus lens 8, the plano-concave lens 11, and the second plano-convex lens 14 have a refractive index of 1.458 for 313nm fluorescence. In this embodiment, the first positive meniscus lens 3, the first plano-convex lens 6, the second positive meniscus lens 7, the third positive meniscus lens 8, the plano-concave lens 11, and the second plano-convex lens 14 are made of fused silica.

[0037] Furthermore, to increase the transmittance of fluorescence through the first positive meniscus lens 3, the first plano-convex lens 6, the plano-concave lens 11, and the second plano-convex lens 14, antireflection films are deposited on both surfaces of the first positive meniscus lens 3, the first plano-convex lens 6, the plano-concave lens 11, and the second plano-convex lens 14, with an antireflection wavelength of 245-400nm, while the antireflection film of the plano-concave lens 11 has an antireflection wavelength of 245-440nm.

[0038] When applying this invention, the microscope and the short-cavity ultraviolet fluorescence imaging system of this invention are coaxially configured. The 313nm fluorescence emitted by the Be+ ions 16 located in the vacuum chamber 17 passes through the short-cavity ultraviolet fluorescence imaging system (in... Figure 2 (Referred to as a short-cavity ultraviolet fluorescence imaging system 18) performs a primary imaging, and then a secondary imaging is achieved through a microscope 19 onto the charge-coupled device 20, such as... Figures 2-3 As shown.

[0039] Example 2: A short-cavity ultraviolet fluorescence imaging system with a long working distance, based on Embodiment 1, further includes a first lens retainer 2, a second lens retainer 4, a third lens retainer 5, a fourth lens retainer 9, a fifth lens retainer 10, a sixth lens retainer 12, a seventh lens retainer 13, and an eighth lens retainer 15 disposed within a lens sleeve 1. A first positive meniscus lens 3 is secured between the first lens retainer 2 and the second lens retainer 4; a first plano-convex lens 6, a second positive meniscus lens 7, and a third positive meniscus lens 8 are secured between the third lens retainer 5 and the fourth lens retainer 9; the convex surface of the first plano-convex lens 6 is tangent to the convex surface of the second positive meniscus lens 7, and the concave surface of the second positive meniscus lens 7 is tangent to the convex surface of the third positive meniscus lens 8; a plano-concave lens 11 is secured between the fifth lens retainer 10 and the sixth lens retainer 12; and a second plano-convex lens 14 is secured between the seventh lens retainer 13 and the eighth lens retainer 15. The first lens retaining ring 2, the second lens retaining ring 4, the third lens retaining ring 5, the fourth lens retaining ring 9, the fifth lens retaining ring 10, the sixth lens retaining ring 12, the seventh lens retaining ring 13, and the eighth lens retaining ring 15 are all circumferentially provided with external threads that are compatible with the internal threads inside the lens sleeve 1.

[0040] In this embodiment, the lens sleeve 1 has an outer diameter of 56 mm, an internal SM2 thread, and a thickness of 242.50 mm. The inner diameter of the first to eighth lens retaining rings is 48.00 mm, the circumferential thread is SM2, and the thickness is 2.50 mm.

[0041] The first positive meniscus lens 3, the first plano-convex lens 6, the second positive meniscus lens 7, the third positive meniscus lens 8, the plano-concave lens 11, and the second plano-convex lens 14 are all 2-inch spherical mirrors.

[0042] When assembling the above-mentioned short-cavity ultraviolet fluorescence imaging system, the first lens retainer 2 is screwed to the top of the lens sleeve 1, with the first lens retainer 2 parallel to the cross-section of the lens sleeve 1. The first positive meniscus lens 3 is then placed in the sleeve. The second lens retainer 4 is screwed onto the surface of the first positive meniscus lens 3, and the first positive meniscus lens 3 is fixed by the second lens retainer 4. The third lens retainer 5 is placed in the lens sleeve 1, with a distance of 10.59 mm from the second lens retainer 4 (the distance between retainers is assumed to be the distance between the same position of the two retainers; in this embodiment, the thickness of the retainer is 2.5 mm, and the center distance between the convex surface of the first positive meniscus lens 3 and the plane of the first plano-convex lens 6 is 13.088 mm; in actual assembly, the thickness of one retainer 5 should be subtracted from this). Then, the first plano-convex lens 6, the second positive meniscus lens 7, and the third positive meniscus lens 8 are placed in sequence. The fourth lens retainer 9 is screwed onto the surface of the third positive meniscus lens 8, and the first plano-convex lens 6, the second positive meniscus lens 7, and the third positive meniscus lens 8 are fixed by the fourth lens retainer 9. Next, the fifth lens retainer 10 is placed in the lens sleeve 1, with a distance of 44.01 mm from the fourth lens retainer 9. The plano-concave lens 11 is then placed in and contacts the fifth lens retainer 10. The plano-concave lens 11 is then secured with the sixth lens retainer 12. The seventh lens retainer 13 is placed in the lens sleeve 1, with a distance of 107.50 mm between the seventh lens retainer 13 and the sixth lens retainer 12. The second plano-convex lens 14 is then placed in and finally secured with the eighth lens retainer 15. The first positive meniscus lens 3, the first plano-convex lens 6, the second positive meniscus lens 7, the third positive meniscus lens 8, the plano-concave lens 11, and the second plano-convex lens 14 are coaxially arranged.

[0043] The short-cavity ultraviolet fluorescence imaging system of this invention has an object-side numerical aperture (NA) of 0.3, an effective focal length of 43.65 mm, and a working distance of 66.37 mm. The lens sleeve 1 and all lens retainers (including the first lens retainer 2, the second lens retainer 4, the third lens retainer 5, the fourth lens retainer 9, the fifth lens retainer 10, the sixth lens retainer 12, the seventh lens retainer 13, and the eighth lens retainer 15) are made of aluminum alloy with a black anodized surface.

[0044] The total length of the short-cavity ultraviolet fluorescence imaging system of this invention is 280.10 mm. The lenses used are a first positive meniscus lens 3 with a focal length of 150 mm, a first plano-convex lens 6 with a focal length of 150 mm, a second positive meniscus lens 7 and a third positive meniscus lens 8 with a focal length of 300 mm, a plano-concave lens 11 with a focal length of -100 mm, and a second plano-convex lens 14 with a focal length of 60 mm.

[0045] Figure 4The imaging results are obtained by testing the short cavity ultraviolet fluorescence imaging system 18 with a 1951 USAF resolution test target (3 inches x 3 inches). The wavelength of the laser used in the test is 313 nm. Then, diffuse light is obtained by using a scattering sheet, and finally, the image is captured by a CCD camera. The image captured by the CCD camera is displayed using the software HCImageLive, with an exposure time of 400 ms.

[0046] In this embodiment, the scattering sheet, resolution test target, short cavity ultraviolet fluorescence imaging system 18, and CCD camera are coaxially configured.

[0047] During testing, the position of the diffuser affects the imaging effect. If the diffuser is far from the resolution target, the light intensity will be significantly attenuated, the signal-to-noise ratio (SNR) will decrease, the image will become very dark, and weak light areas may not be clearly imaged. If the diffuser is too close, the scattered light from the laser will not diffuse sufficiently, resulting in uneven illumination of the target surface (bright center, dark edges), causing local overexposure or underexposure of the test target stripes, and distorting the test stripes.

[0048] The resolution of all fringes on the 1951 USAF test target can be found on the Thorlabs website. Observation of the image shows that fringe 7-1 is clearly resolved, and the width of a single fringe is 3.9 μm, so the resolution can reach 5 μm. Using the line intensity profile analysis function of the HCImageLive software, the pixel position-intensity data can be filtered and analyzed, which also shows that the resolution of this short-cavity ultraviolet fluorescence imaging system can reach 5 μm.

[0049] The microscope objective used in the test had a magnification of 20X and an aperture of NA=0.38, but in the actual optical path setup, the final image magnification was 14.93.

[0050] like Figure 5 As shown, the axial modulation and demodulation function of the short-cavity ultraviolet fluorescence imaging system 18 of this invention is close to the diffraction limit, and the spatial frequency corresponding to the modulus value of 0.2 is approximately 844.2 lp / mm.

[0051] The above embodiments are only for illustrating the specific implementation of the technology of this utility model. Their purpose is to enable those skilled in the art to understand the content of this utility model and implement it accordingly, and they should not be construed as limiting the protection scope of this utility model.

Claims

1. A short-cavity ultraviolet fluorescence imaging system with a long working distance, comprising a lens sleeve (1), characterized in that, It also includes a first positive meniscus lens (3), a first plano-convex lens (6), a second positive meniscus lens (7), a third positive meniscus lens (8), a plano-concave lens (11), and a second plano-convex lens (14) arranged sequentially and coaxially within the lens sleeve (1) along the fluorescence imaging direction. Along the direction of fluorescence imaging, The first positive meniscus lens (3) has a concave surface and a convex surface on its two sides, respectively; The two surfaces of the first plano-convex lens (6) are a plane and a convex surface, respectively; The second positive meniscus lens (7) has a convex surface and a concave surface on its two sides, respectively; The third positive meniscus lens (8) has a convex surface and a concave surface on its two sides, respectively; The two sides of the plano-concave lens (11) are a concave surface and a plane, respectively; The second plano-convex lens (14) has a convex surface and a plane surface on its two sides, respectively.

2. The short-cavity ultraviolet fluorescence imaging system with a long working distance according to claim 1, characterized in that, The center thickness of both the first positive meniscus lens (3) and the first plano-convex lens (6) is 7.84 mm. The center thickness of both the second positive meniscus lens (7) and the third positive meniscus lens (8) is 5.36 mm. The center thickness of the plano-concave lens (11) is 2.50 mm. The center thickness of the second plano-convex lens (14) is 19.79 mm; The concave and convex radii of curvature of the first positive meniscus lens (3) are -135.25 mm and -46.53 mm, respectively. The radius of curvature of the convex surface of the first plano-convex lens (6) is -69.01 mm. The radii of curvature of the convex and concave surfaces of the second positive meniscus lens (7) are 97.61 mm and 327.59 mm, respectively. The radii of curvature of the convex and concave surfaces of the third positive meniscus lens (8) are 97.61 mm and 327.59 mm, respectively. The radius of curvature of the concave surface of the plano-concave lens (11) is -45.90 mm. The radius of curvature of the convex surface of the second plano-convex lens (14) is 27.60 mm.

3. The short-cavity ultraviolet fluorescence imaging system with a long working distance according to claim 1, characterized in that, The center distance between the convex surface of the first positive meniscus lens (3) and the plane of the first plano-convex lens (6) is 13.088 mm. The convex surface of the first plano-convex lens (6) is tangent to the convex surface of the second positive meniscus lens (7). The concave surface of the second positive meniscus lens (7) and the convex surface of the third positive meniscus lens (8) are tangent. The center distance between the concave surface of the third positive meniscus lens (8) and the concave surface of the plano lens (11) is 46.508 mm. The center distance between the plane of the plano-concave lens (11) and the convex surface of the second plano-convex lens (14) is 110.00 mm.

4. The short-cavity ultraviolet fluorescence imaging system with a long working distance according to claim 1, characterized in that, The first positive meniscus lens (3), the first plano-convex lens (6), the second positive meniscus lens (7), the third positive meniscus lens (8), the plano-concave lens (11), and the second plano-convex lens (14) have a refractive index of 1.458 for 313nm fluorescence.

5. A short-cavity ultraviolet fluorescence imaging system with a long working distance according to claim 4, characterized in that, The first positive meniscus lens (3), the first plano-convex lens (6), the second positive meniscus lens (7), the third positive meniscus lens (8), the plano-concave lens (11), and the second plano-convex lens (14) are made of fused silica.

6. The short-cavity ultraviolet fluorescence imaging system with a long working distance according to claim 1, characterized in that, The first positive meniscus lens (3), the first plano-convex lens (6), the plano-concave lens (11), and the second plano-convex lens (14) are all coated with anti-reflection films with an anti-reflection wavelength of 245-400nm. The anti-reflection film of the plano-concave lens (11) has an anti-reflection wavelength of 245-440nm.

7. The short-cavity ultraviolet fluorescence imaging system with a long working distance according to claim 1, characterized in that, The lens sleeve (1) is also provided with a first lens retaining ring (2), a second lens retaining ring (4), a third lens retaining ring (5), a fourth lens retaining ring (9), a fifth lens retaining ring (10), a sixth lens retaining ring (12), a seventh lens retaining ring (13), and an eighth lens retaining ring (15). The first positive meniscus lens (3) is positioned between the first lens retainer (2) and the second lens retainer (4). The first plano-convex lens (6), the second positive meniscus lens (7), and the third positive meniscus lens (8) are positioned between the third lens retainer (5) and the fourth lens retainer (9). The plano-concave lens (11) is positioned between the fifth lens retainer (10) and the sixth lens retainer (12). The second plano-convex lens (14) is positioned between the seventh lens retainer (13) and the eighth lens retainer (15).

8. A short-cavity ultraviolet fluorescence imaging system with a long working distance according to claim 7, characterized in that, The first lens retainer (2), the second lens retainer (4), the third lens retainer (5), the fourth lens retainer (9), the fifth lens retainer (10), the sixth lens retainer (12), the seventh lens retainer (13), and the eighth lens retainer (15) are all provided with external threads in the circumferential direction that are adapted to the internal threads in the lens sleeve (1).

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