Microobjective with wide spectrum and ultra-long working distance

Abstract

The invention discloses a wide-spectrum super-long working distance microscope objective, and relates to the technical field of optical lenses. The microscope lens coaxially and sequentially comprises a first lens group G1, a second lens group G2, a third lens group G3 and a diaphragm from an image side to an object side, the focal lengths of the first lens group G1, the second lens group G2, the third lens group G3 and the diaphragm meet the conditions that f1 / f is larger than or equal to 1.1 and smaller than or equal to 1.6, f2 / f is larger than or equal to 16.8 and smaller than or equal to 17.3, and f3 / f is larger than or equal to 2.2 and smaller than or equal to 2.7, f is the total focal length of the microscope objective, f1 is the focal length of the first lens group G1, f2 is the focal length of the second lens group G2, and f3 is the focal length of the third lens group G3. Through reasonable focal power matching among the first lens group G1, the second lens group G2 and the third lens group G3, the whole light of the system is spread stably, the imaging quality is excellent, and compared with the existing microscope lens with the same magnification, the microscope lens has the advantages of longer working distance, larger numerical aperture, higher resolution and the like, and the microscope lens has a wide application prospect. Therefore, the microscope lens provided by the invention can better meet the increasingly diversified and complicated market requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of optical lenses, and particularly to a wide-spectrum ultra-long working distance microscopic objective lens. Background Art

[0002] With the rapid development of technology, microscopic technology is increasingly widely used in fields such as life science, medicine, semiconductor detection, and materials science, posing higher requirements for the performance of microscopic objective lenses. Especially in terms of large numerical aperture, ultra-long working distance, and wide-spectrum applicability, the functional requirements for microscopic objective lenses have been significantly improved. The ultra-long working distance can provide a larger space between the microscopic objective lens and the observed sample, facilitating the integration of various detection devices (such as light sources, filters, lasers, etc.), and reducing the potential damage risk to the sample during the operation of the microscopic objective lens. The large numerical aperture significantly increases the light input of the microscopic objective lens, enhancing the imaging brightness and resolution, which is crucial for capturing weak signals (such as bioluminescence). In addition, the wide-spectrum applicability enables the microscopic objective lens to provide excellent imaging performance within a larger wavelength range, meeting the requirements of multi-spectral detection, thereby achieving a comprehensive observation of the detected sample. The combination of these functions can significantly improve the efficiency and quality of microscopic detection, providing strong support for technological progress in various fields.

[0003] In the prior art, high-resolution microscopic objective lenses often have difficulty in balancing due to the mutual restriction between the numerical aperture (NA) and the working distance (WD): a high NA requires a short working distance, while a long working distance requires sacrificing resolution. For example, although the NA of the Olympus LUMPLFLN series microscopic objective lens reaches 0.4, its working distance is only 3.3 mm, and the spectral range is limited. In addition, wide-spectrum applications require complex chromatic aberration correction techniques, usually relying on special materials (such as calcium fluoride) or diffractive elements, resulting in high costs and complex processes. Summary of the Invention

[0004] The purpose of the present invention is to provide a wide-spectrum ultra-long working distance microscopic objective lens with a numerical aperture of 0.3, a magnification of 5 times, and a working distance of 45 mm, aiming to solve the problems of short working distance, poor spectral adaptability, and complex chromatic dispersion correction in the prior art.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A wide-spectrum ultra-long working distance microscopic objective lens, which sequentially includes a first lens group, a second lens group, and a third lens group having the same optical axis from the image side to the object side. A diaphragm is installed in the third lens group, and the microscopic objective lens satisfies:

[0007] 1.1 ≤ |f1 / f| ≤ 1.6;

[0008] 16.8 ≤ |f2 / f| ≤ 17.3;

[0009] 2.2 ≤ |f3 / f| ≤ 2.7;

[0010] In the formula, f is the total focal length of the microscope objective lens, f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, and f3 is the focal length of the third lens group;

[0011] The first lens group has a negative optical power, and both the image side and the object side of the first lens group are concave surfaces;

[0012] The second lens group has a positive optical power, the image side of the second lens group is a convex surface, and the object side is a concave surface;

[0013] The third lens group has a positive optical power, the image side of the third lens group is a convex surface, and the object side is a flat surface;

[0014] Wherein, the air gap between the object side of the first lens group and the image side of the second lens group is 6.3 mm to 6.8 mm, and the air gap between the object side of the second lens group and the image side of the third lens group is 15.8 mm to 16.3 mm.

[0015] As a further solution of the present invention: the first lens group sequentially includes a first lens made of heavy flint glass and a second lens made of heavy lanthanum flint glass from the image side to the object side along the same optical axis, and the object side of the first lens and the image side of the second lens are cemented.

[0016] As a further solution of the present invention: the first lens is a meniscus lens with a negative optical power, its focal length is -80 mm to -75 mm, its thickness is 2.3 mm to 2.8 mm, the image side is a concave surface, and the object side is a convex surface;

[0017] The second lens is a double concave lens with a negative optical power, its focal length is -20 mm to -15 mm, its thickness is 2.3 mm to 2.8 mm, the image side is a concave surface, and the object side is a concave surface.

[0018] As a further solution of the present invention: the second lens group sequentially includes a third lens made of barium crown glass, a fourth lens made of heavy flint glass, and a fifth lens made of heavy lanthanum flint glass from the image side to the object side along the same optical axis.

[0019] As a further solution of the present invention: the third lens is a meniscus lens with a negative optical power, its focal length is -43 mm to -38 mm, its thickness is 2.4 mm to 2.9 mm, the image side is a convex surface, and the object side is a concave surface;

[0020] The fourth lens is a biconvex lens with a positive optical power, having a focal length of 2 mm to 7 mm, a thickness of 5.8 mm to 6.3 mm, a convex image side, and a convex object side;

[0021] The fifth lens is a biconcave lens with a negative optical power, having a focal length of -10 mm to -5 mm, a thickness of 2.8 mm to 3.3 mm, a concave image side, and a concave object side.

[0022] As a further aspect of the present invention: The third lens group sequentially includes, from the image side to the object side along the same optical axis, a sixth lens made of heavy flint glass, a seventh lens made of fluorite crown glass, an eighth lens made of heavy lanthanum flint glass, a ninth lens made of fluorite crown glass, a tenth lens made of fluorite crown glass, an eleventh lens made of fluorite crown glass, and a twelfth lens made of heavy phosphate crown glass. The aperture stop is disposed between the ninth lens and the tenth lens.

[0023] As a further aspect of the present invention: The object side of the sixth lens and the image side of the seventh lens are cemented; the air gap between the object side of the seventh lens and the image side of the eighth lens is 0.6 to 1.1 mm; the object side of the eighth lens and the image side of the ninth lens are cemented; the air gap between the object side of the ninth lens and the image side of the tenth lens is 0.1 mm to 0.6 mm; the air gap between the object side of the tenth lens and the image side of the eleventh lens is 0.1 mm to 0.6 mm; the air gap between the object side of the eleventh lens and the image side of the twelfth lens is 0.2 mm to 0.7 mm.

[0024] As a further aspect of the present invention: The sixth lens is a meniscus lens with a negative optical power, having a focal length of -55 mm to -50 mm, a thickness of 2.8 mm to 3.3 mm, a convex image side, and a concave object side;

[0025] The seventh lens is a biconvex lens with a positive optical power, having a focal length of 25 mm to 30 mm, a thickness of 8.1 mm to 8.6 mm, a convex image side, and a convex object side;

[0026] The eighth lens is a biconcave lens with a negative optical power, having a focal length of -20 mm to -15 mm, a thickness of 2.2 mm to 2.7 mm, a concave image side, and a concave object side;

[0027] The ninth lens is a biconvex lens with a positive optical power, having a focal length of 40 mm to 45 mm, a thickness of 6.1 mm to 6.6 mm, a convex image side, and a convex object side;

[0028] The tenth lens is a biconvex lens with a positive focal power, having a focal length of 80 mm to 85 mm, a thickness of 4.0 mm to 4.5 mm, a convex image side, and a convex object side;

[0029] The eleventh lens is a biconvex lens with a positive focal power, having a focal length of 81 mm to 86 mm, a thickness of 4.3 mm to 4.8 mm, a convex image side, and a convex object side;

[0030] The twelfth lens is a convex-plano lens with a positive focal power, having a focal length of 60 mm to 65 mm, a thickness of 4.5 mm to 5.0 mm, a convex image side, and a flat object side.

[0031] As a further solution of the present invention: the first lens group, the second lens group, and the third lens group are all spherical lenses.

[0032] As a further solution of the present invention: the total focal length f of the microscopic objective lens is 10 mm, the working distance WD is 45 mm, the numerical aperture NA is 0.3, the magnification is 5 times, and the working wavelength range is 500 nm to 600 nm.

[0033] Advantages of the present invention:

[0034] (1) A wide-spectrum ultra-long working distance microscopic objective lens with NA = 0.3 provided by the present invention significantly increases the working distance of the microscopic objective lens to 45 mm by reasonably optimizing the focal power distribution strategy, greatly improving the operability and versatility of the microscopic objective lens. This ultra-long working distance not only provides more space for the integration of other optical and mechanical components in the microscopic system, but also effectively reduces the operation risk of the sample in actual applications, while enhancing the compatibility and flexibility of microscopic detection, especially suitable for high-precision fields such as precision machining. In addition, the present invention uses multiple groups of doublet lens groups and triplet lens groups for chromatic aberration correction, achieving accurate color reproduction and excellent imaging quality in a wide spectral range without introducing special optical materials (such as CaF2) or binary diffraction elements, significantly improving the performance and application range of the microscopic objective lens;

[0035] (2) By optimizing the thickness, material, air gap, and diaphragm position of each lens, the present invention finally achieves an optical index of numerical aperture NA 0.3. In addition, other indexes such as working distance WD, F-number, point spread function, axial aberration, distortion, etc. are all changed according to the improvement of this numerical aperture index. While ensuring its working distance, it has excellent optical performance, a flat field of view, and excellent imaging quality. At the same time, the volume of the optimized microscopic objective lens is greatly reduced, facilitating precise detection during the production and processing process. This microscopic objective lens is suitable for scenarios such as semiconductor wafer detection and multi-spectral imaging of biological samples, especially adapted to automated detection equipment requiring a long working distance. Brief Description of the Drawings

[0036] The present invention will be further described below in conjunction with the accompanying drawings.

[0037] Figure 1 is a schematic optical structure diagram of a wide-spectrum ultra-long working distance microscope objective of the present invention;

[0038] Figure 2 is a modulation transfer function curve diagram of a wide-spectrum ultra-long working distance microscope objective of the present invention;

[0039] Figure 3 is a spot diagram of a wide-spectrum ultra-long working distance microscope objective of the present invention;

[0040] Figure 4 is an axial chromatic aberration curve diagram of a wide-spectrum ultra-long working distance microscope objective of the present invention;

[0041] Figure 5 is a distortion diagram of a wide-spectrum ultra-long working distance microscope objective of the present invention. Detailed Embodiments

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] Please refer to Figure 1 As shown, the embodiment of the present invention provides a wide-spectrum ultra-long working distance microscope objective, which sequentially includes a first lens group G1, a second lens group G2, and a third lens group G3 having the same optical axis from the image side IMA to the object side OBJ. A diaphragm STO is installed in the third lens group G3.

[0044] The first lens group G1 is used to increase the working distance of the objective lens, facilitating the integration and operation of the microscopic system; the second lens group G2 is used to correct the flat field and secondary spectrum of the image plane to ensure the imaging quality under a wide spectrum; the third lens group G3 is used to bear most of the optical power to ensure the imaging performance of the objective lens at a large numerical aperture and high resolution.

[0045] This grouping design enables the microscope objective to achieve a better balance among ultra-long working distance, large numerical aperture, and wide-spectrum performance, meeting the requirements of specific application scenarios. The optical powers of the first lens group G1, the second lens group G2, and the third lens group G3 cooperate with each other to ensure the smooth propagation of the overall light rays of the system.

[0046] The microscope objective satisfies:

[0047] 1.1 ≤ |f1 / f| ≤ 1.6;

[0048] 16.8 ≤ |f2 / f| ≤ 17.3;

[0049] 2.2 ≤ |f3 / f| ≤ 2.7;

[0050] Wherein, f is the total focal length of the microscope objective lens, f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, and f3 is the focal length of the third lens group.

[0051] Please refer to Figure 1 As shown, in this embodiment, the first lens group G1 has a negative optical power and sequentially includes a first lens L1 and a second lens L2 along the same optical axis from the image side to the object side.

[0052] Among them, the object side surface of the first lens L1 and the image side surface of the second lens L2 are cemented. The first lens L1 is a meniscus lens with a negative optical power, its focal length is -80 mm to -75 mm, its thickness is 2.3 mm to 2.8 mm, the material is environmentally friendly heavy flint glass, the image side surface S1 is concave, and the object side surface S2 is convex. The second lens L2 is a biconcave lens with a negative optical power, its focal length is -20 mm to -15 mm, its thickness is 2.3 mm to 2.8 mm, the material is environmentally friendly heavy lanthanum flint glass.

[0053] Please refer to Figure 1 As shown, in this embodiment, the second lens group G2 has a positive optical power and sequentially includes a third lens L3, a fourth lens L4, and a fifth lens L5 along the same optical axis from the image side to the object side.

[0054] Among them, the air gap between the object side surface of the second lens L2 and the image side surface of the third lens L3 is 6.3 to 6.8 mm; the object side surface of the third lens L3 and the image side surface of the fourth lens L4 are cemented; the object side surface of the fourth lens L4 and the image side surface of the fifth lens L5 are cemented. The third lens L3 is a meniscus lens with a negative optical power, its focal length is -43 mm to -38 mm, its thickness is 2.4 mm to 2.9 mm, the material is environmentally friendly barium crown glass, the image side surface S4 is convex, and the object side surface S5 is concave; the fourth lens L4 is a biconvex lens with a positive optical power, its focal length is 2 mm to 7 mm, its thickness is 5.8 mm to 6.3 mm, the material is environmentally friendly heavy flint glass, the image side surface S5 is convex, and the object side surface S6 is convex; the fifth lens L5 is a biconcave lens with a negative optical power, its focal length is -10 mm to -5 mm, its thickness is 2.8 mm to 3.3 mm, the material is environmentally friendly heavy lanthanum flint glass, the image side surface S6 is concave, and the object side surface S7 is concave.

[0055] Please refer to Figure 1As shown, in this embodiment, the third lens group G3 has a positive optical power and sequentially includes a sixth lens L6, a seventh lens L7, an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, and a twelfth lens L12 from the image side to the object side along the same optical axis. The aperture stop is disposed between the ninth lens L9 and the tenth lens L10.

[0056] As the core component for controlling the beam aperture, the position and physical parameters of the aperture stop STO directly affect the imaging quality and light energy utilization rate of the microscope objective.

[0057] In this embodiment:

[0058] The aperture stop STO is precisely located between the ninth lens L9 and the tenth lens L10. The specific position is determined by Zemax optimization, which can effectively balance the requirements for spherical aberration and coma correction. The aperture diameter of the aperture stop STO is Φ3.8 mm, and the light passing amount is adapted to the numerical aperture of NA = 0.3, ensuring that the light energy is concentrated and the marginal vignetting ≤ 5% in the wavelength range of 500 nm - 600 nm. It is made of black anodized aluminum and the surface is matte treated (roughness Ra = 0.15 μm), significantly reducing the stray light reflection (reflectivity < 0.5%) and avoiding ghost image interference. The aperture stop is fixed by a precision ring bracket, and the coaxiality tolerance ≤ 5 μm to ensure the symmetry of the optical path.

[0059] The design of this aperture stop STO can be adapted to the automated assembly process, supports customized aperture sizes (such as Φ3.5 mm for high image quality detection and Φ4.0 mm for low light environments), and meets the requirements of different brightness scenarios in semiconductor detection.

[0060] The air gap between the object side of the fifth lens L5 and the image side of the sixth lens L6 is 15.8 mm to 16.3 mm; the object side of the sixth lens L6 and the image side of the seventh lens L7 are cemented; the air gap between the object side of the seventh lens L7 and the image side of the eighth lens L8 is 0.6 mm to 1.1 mm; the object side of the eighth lens L8 and the image side of the ninth lens L9 are cemented; the air gap between the object side of the ninth lens L9 and the image side of the tenth lens L10 is 0.1 mm to 0.6 mm; the air gap between the object side of the tenth lens L10 and the image side of the eleventh lens L11 is 0.1 mm to 0.6 mm; the air gap between the object side of the eleventh lens L11 and the image side of the twelfth lens L12 is 0.2 mm to 0.7 mm.

[0061] The sixth lens L6 is a meniscus lens with a negative optical power, having a focal length of -55 mm to -50 mm, a thickness of 2.8 mm to 3.3 mm, and is made of environmentally friendly heavy flint glass. The image side S8 is convex, and the object side S9 is concave; the seventh lens L7 is a biconvex lens with a positive optical power, having a focal length of 25 mm to 30 mm, a thickness of 8.1 mm to 8.6 mm, and is made of environmentally friendly barium crown glass. The image side S9 is convex, and the object side S10 is convex; the eighth lens L8 is a biconcave lens with a negative optical power, having a focal length of -20 mm to -15 mm, a thickness of 2.2 mm to 2.7 mm, and is made of environmentally friendly heavy lanthanum flint glass. The image side S11 is concave, and the object side S12 is concave; the ninth lens L9 is a biconvex lens with a positive optical power, having a focal length of 40 mm to 45 mm, a thickness of 6.1 mm to 6.6 mm, and is made of environmentally friendly fluor crown glass. The image side S12 is convex, and the object side S13 is convex; the tenth lens L10 is a biconvex lens with a positive optical power, having a focal length of 80 mm to 85 mm, a thickness of 4.0 mm to 4.5 mm, and is made of environmentally friendly fluor crown glass. The image side S14 is convex, and the object side S15 is convex; the eleventh lens L11 is a biconvex lens with a positive optical power, having a focal length of 81 mm to 86 mm, a thickness of 4.3 mm to 4.8 mm, and is made of environmentally friendly fluor crown glass. The image side S16 is convex, and the object side S17 is convex; the twelfth lens L12 is a plano-convex lens with a positive optical power, having a focal length of 60 mm to 65 mm, a thickness of 4.5 mm to 5.0 mm, and is made of environmentally friendly heavy phosphate crown glass. The image side S18 is convex, and the object side S19 is flat;

[0062] The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the ninth lens L9, the tenth lens L10, the eleventh lens L11, and the twelfth lens L12 are all spherical lenses, which are easy to process and detect.

[0063] The present invention adopts an infinite conjugate imaging system design. Based on the reverse design concept, the light beam emits from the object surface OBJ, successively passes through the third lens group G3 and the aperture stop, the second lens group G2, and the first lens group G1, and finally forms a parallel light beam. This parallel light beam is converged and imaged by the tube lens to ensure the stability of the imaging quality of the system. The design of the microscopic objective lens of the present invention allows optical elements such as filter and beam splitter to be added between the tube lens and the objective lens, greatly improving the flexibility and expandability of the system, and being able to meet various detection requirements.

[0064] In this embodiment, specific optical parameters shown in Table 1 are used for simulation.

[0065]

[0066] In an embodiment, the focal length f1 of the first lens group G1 is -14 mm, the focal length f2 of the second lens group G2 is 172 mm, and the focal length f3 of the third lens group G3 is 26 mm. The working distance WD is 45 mm, the image space F-number is 1.7, the working wavelength band is 500 nm to 600 nm, the numerical aperture NA is 0.3, the effective focal length f is 10 mm, and the magnification is 5 times.

[0067] Please refer to Figure 2 As shown, the transfer function image in the embodiment of the present invention represents the resolution ability at different line pairs in the meridional plane and the sagittal plane of each field of view and each wavelength in the optical system. The horizontal axis represents the resolvable line pairs, and the vertical axis represents the contrast. The higher the contrast, the better the imaging quality. It can be seen from the figure that the transfer function of the present invention is close to the diffraction limit and has excellent imaging quality.

[0068] Please refer to Figure 3 As shown, the spot diagram of this embodiment intuitively reflects the optical performance. From Figure 3 it can be seen that the spot diagrams of the full field of view of the present invention are mostly within the Airy disk, and it has excellent imaging quality.

[0069] Please refer to Figure 4 As shown, the full-field axial aberration curve diagram of this embodiment, the vertical axis is the normalized entrance pupil diameter, and the horizontal axis represents the axial aberration, with the unit of millimeter. From Figure 4 it can be seen that the maximum focal shift between 550 nm and 600 nm of the present invention is less than 4 μm, meeting the achromatic condition.

[0070] Please refer to Figure 5 As shown, the distortion curve diagram of this embodiment, the horizontal axis is the distortion ratio, with the unit of %; the vertical axis is the field of view, with the unit of degree. From Figure 5 it can be seen that the maximum distortion amount of the present invention is 0.46%, and the distortion is effectively corrected.

[0071] This design is optimized and verified through the optical design software Zemax, and the specific steps are as follows:

[0072] Initial structure construction: According to the optical power distribution and material parameters of the lens group, an initial optical model is established in Zemax, and the object distance is set to 45 mm, the numerical aperture NA = 0.3, and the working wavelength band is 500 - 600 nm.

[0073] Application of optimization algorithm: The global optimization (Global Search) and local optimization (Local Optimization) algorithms of Zemax are adopted to adjust the lens curvature radius, thickness, and interval to minimize spherical aberration, astigmatism, and chromatic aberration.

[0074] Tolerance control of bonding surface: Set the curvature radius tolerance of the bonding surface to ≤±0.02mm to ensure that the impact of the bonding process on optical performance is controllable.

[0075] Performance Analysis:

[0076] MTF curve ( Figure 2 ): Contrast ratio > 0.45 at 150lp / mm in the full field of view, close to the diffraction limit;

[0077] Point diagram ( Figure 3 ): Diffuse spot diameter ≤ 4 μm, concentrated in the Airy disk;

[0078] Axial chromatic aberration ( Figure 4 ): Focal shift in the 550nm-600nm band is less than 3.8μm;

[0079] distortion( Figure 5 ): Maximum distortion is 0.46%, meeting the needs of high-precision imaging.

[0080] Tolerance analysis: Monte Carlo Tolerance Analysis of Zemax is used to verify the robustness of the design to processing errors and ensure the feasibility of mass production.

[0081] Industrial Applicability

[0082] This microscope objective is suitable for scenes such as semiconductor wafer inspection and multispectral imaging of biological samples, and is especially suitable for automated inspection equipment that requires a long working distance.

[0083] The above is a detailed description of the preferred embodiments of the present invention, which cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A wide spectrum ultra-long working distance microscope objective lens, characterized in that: The microscope objective lens includes, from the image side to the object side, a first lens group, a second lens group, and a third lens group having the same optical axis, wherein an aperture is installed in the third lens group, and the microscope objective lens satisfies: 1.1≤|f1 / f|≤1.6; 16.8≤|f2 / f|≤17.3; 2.2≤|f3 / f|≤2.7; Wherein, f is the total focal length of the microscope objective lens, f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, and f3 is the focal length of the third lens group; The first lens group has negative optical power, and both the image side surface and the object side surface of the first lens group are concave; The second lens group has positive optical power, the image side surface of the second lens group is convex, and the object side surface is concave; The third lens group has positive optical power, the image side surface of the third lens group is a convex surface, and the object side surface is a flat surface; The air gap between the object side of the first lens group and the image side of the second lens group is 6.3 mm to 6.8 mm, and the air gap between the object side of the second lens group and the image side of the third lens group is 15.8 mm to 16.3 mm.

2. A wide spectrum ultra-long working distance microscope objective lens according to claim 1, characterized in that: The first lens group includes, from the image side to the object side along the same optical axis, a first lens made of heavy flint glass and a second lens made of heavy lanthanum flint glass, and the object side surface of the first lens is glued to the image side surface of the second lens.

3. A wide spectrum ultra-long working distance microscope objective lens according to claim 2, characterized in that: The first lens is a meniscus lens with negative optical power, with a focal length of -80 mm to -75 mm, a thickness of 2.3 mm to 2.8 mm, a concave image side surface, and a convex object side surface; The second lens is a double concave lens with negative optical power, a focal length of -20 mm to -15 mm, a thickness of 2.3 mm to 2.8 mm, a concave image side surface, and a concave object side surface.

4. A wide spectrum ultra-long working distance microscope objective lens according to claim 1, characterized in that: The second lens group includes, from the image side to the object side along the same optical axis, a third lens made of barium crown glass, a fourth lens made of heavy flint glass, and a fifth lens made of heavy lanthanum flint glass.

5. A wide spectrum ultra-long working distance microscope objective lens according to claim 4, characterized in that: The third lens is a meniscus lens with negative focal power, with a focal length of -43 mm to -38 mm, a thickness of 2.4 mm to 2.9 mm, a convex image side surface, and a concave object side surface; The fourth lens is a biconvex lens with positive power, a focal length of 2 mm to 7 mm, a thickness of 5.8 mm to 6.3 mm, a convex image side surface, and a convex object side surface; The fifth lens is a double concave lens with negative optical power, a focal length of -10 mm to -5 mm, a thickness of 2.8 mm to 3.3 mm, a concave image side surface, and a concave object side surface.

6. A wide spectrum ultra-long working distance microscope objective lens according to claim 1, characterized in that: The third lens group includes, from the image side to the object side along the same optical axis, a sixth lens made of heavy flint glass, a seventh lens made of fluor crown glass, an eighth lens made of heavy lanthanum flint glass, a ninth lens made of fluor crown glass, a tenth lens made of fluor crown glass, an eleventh lens made of fluor crown glass, and a twelfth lens made of heavy phosphorus crown glass, and the aperture is arranged between the ninth lens and the tenth lens.

7. A wide spectrum ultra-long working distance microscope objective lens according to claim 6, characterized in that: The object side surface of the sixth lens is glued to the image side surface of the seventh lens; the air gap between the object side surface of the seventh lens and the image side surface of the eighth lens is 0.6mm-1.1mm; the object side surface of the eighth lens is glued to the image side surface of the ninth lens; the air gap between the object side surface of the ninth lens and the image side surface of the tenth lens is 0.1mm-0.6mm; the air gap between the object side surface of the tenth lens and the image side surface of the eleventh lens is 0.1mm-0.6mm; the air gap between the object side surface of the eleventh lens and the image side surface of the twelfth lens is 0.2mm-0.7mm.

8. A wide spectrum ultra-long working distance microscope objective lens according to claim 7, characterized in that: The sixth lens is a meniscus lens with negative optical power, with a focal length of -55 mm to -50 mm, a thickness of 2.8 mm to 3.3 mm, a convex image side surface, and a concave object side surface; The seventh lens is a biconvex lens with positive power, a focal length of 25 mm to 30 mm, a thickness of 8.1 mm to 8.6 mm, a convex image side surface, and a convex object side surface; The eighth lens is a biconcave lens with negative optical power, a focal length of -20 mm to -15 mm, a thickness of 2.2 mm to 2.7 mm, a concave image side surface, and a concave object side surface; The ninth lens is a biconvex lens with positive power, a focal length of 40 mm to 45 mm, a thickness of 6.1 mm to 6.6 mm, a convex image side surface, and a convex object side surface; The tenth lens is a biconvex lens with positive power, a focal length of 80 mm to 85 mm, a thickness of 4.0 mm to 4.5 mm, a convex image side surface, and a convex object side surface; The eleventh lens is a biconvex lens with positive power, a focal length of 81 mm to 86 mm, a thickness of 4.3 mm to 4.8 mm, a convex surface on the image side, and a convex surface on the object side; The twelfth lens is a convex-plano lens with positive power, a focal length of 60 mm to 65 mm, a thickness of 4.5 mm to 5.0 mm, a convex image side surface, and a flat object side surface.

9. A wide spectrum ultra-long working distance microscope objective lens according to claim 1, characterized in that: The first lens group, the second lens group and the third lens group are all spherical lenses.

10. The wide spectrum ultra-long working distance microscope objective lens according to claim 1, characterized in that: The microscope objective lens has a total focal length f=10 mm, a working distance WD=45 mm, a numerical aperture NA=0.3, a magnification of 5 times, and a working wavelength range of 500 nm to 600 nm.

Images