Microscope objective lens

Abstract

To provide a microscope objective lens relating to the optical lens field, and suitable for use in a device such as a microscope in particular.SOLUTION: A microscope objective lens sequentially comprises from an emission side to an object side: a first lens having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having positive refractive power; a fifth lens having negative refractive power; and a sixth lens having positive refractive power. The microscope objective lens satisfies the following relationships: -5.00≤R11 / R12≤-1.50; 0.40≤WD / TTL≤0.60; 1.00≤R1 / ((n1-1)*f)≤4.00; and 2.00≤d5 / d4≤6.00.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the field of optical lenses, and in particular to microscope objective lenses suitable for use in instruments such as microscopes. [Background technology]

[0002] In recent years, the demand for microscope lenses has been increasing, but in general microscope lenses, due to the constraints of the optical structure, aberration occurs in the microscopic range. Meanwhile, because microscope lenses are composed of multiple lenses, their length is inevitably affected. In addition, the structure of the microscope lens is long, which shortens the working distance, and the magnification is also affected by the working distance, which is disadvantageous for the operator.

[0003] With the development of technology and the diversification of user needs, the requirements for the observation quality of microscope lenses in scientific research are becoming increasingly higher, and there is a strong demand for microscope lenses with the characteristics of excellent optical properties, low distortion, high magnification, and long working distance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a microscope objective lens that can satisfy the requirements for low distortion and long working distance while obtaining high imaging performance.

[0005] In order to solve the above technical problems, the present invention provides a microscope objective lens, which comprises, in order from the exit side to the object side, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, a fourth lens having positive refractive power, a fifth lens having negative refractive power, and a sixth lens having positive refractive power, the central radius of curvature of the exit surface of the sixth lens being R11, the central radius of curvature of the object side surface of the sixth lens being R12, the axial distance from the object surface of the microscope objective lens to the object side surface of the sixth lens being WD, and the distance of the microscope objective lens from the object surface to the object side surface of the sixth lens being WD. The axial distance from the object surface to the exit surface of the first lens is TTL, the central radius of curvature of the exit surface of the first lens is R1, the refractive index of the first lens is n1, the focal length of the microscope objective lens is f, the axial thickness of the third lens is d5, and the axial distance from the second lens to the third lens is d4, and the following relations are satisfied: -5.00≦R11 / R12≦-1.50; 0.40≦WD / TTL≦0.60; 1.00≦R1 / ((n1-1)*f)≦4.00; 2.00≦d5 / d4≦6.00.

[0006] Preferably, the focal length of the fifth lens is f5, and the following relation is satisfied: -0.30≦f5 / f≦-0.20.

[0007] Preferably, the central radius of curvature of the fourth lens exit surface is R7, which satisfies the following relationship: 0.70≦R7 / f≦2.10.

[0008] Preferably, the exit surface of the first lens is convex at the paraxial position, the object side surface of the first lens is convex at the paraxial position, the central radius of curvature of the exit surface of the first lens is R1, the central radius of curvature of the object side surface of the first lens is R2, the axial thickness of the first lens is d1, and the focal length of the first lens is f1, satisfying the following relations: 0.35≦f1 / f≦1.08; -0.71≦(R1+R2) / (R1-R2)≦0.97; 0.02≦d1 / TTL≦0.11.

[0009] Preferably, the exit surface of the second lens is concave at the paraxial position, the object side surface of the second lens is concave at the paraxial position, the central radius of curvature of the exit surface of the second lens is R3, the central radius of curvature of the object side surface of the second lens is R4, the focal length of the second lens is f2, and the axial thickness of the second lens is d3, satisfying the following relations: -0.75≦f2 / f≦-0.22; -0.56≦(R3+R4) / (R3-R4)≦0; 0.01≦d3 / TTL≦0.07.

[0010] Preferably, the object side surface of the third lens is convex at a paraxial position, the central radius of curvature of the exit surface of the third lens is R5, the central radius of curvature of the object side surface of the third lens is R6, and the focal length of the third lens is f3, satisfying the following relations: 0.26≦f3 / f≦0.94; 0.43≦(R5+R6) / (R5-R6)≦1.52; 0.04≦d5 / TTL≦0.17.

[0011] Preferably, the exit surface of the fourth lens is convex at the paraxial position, the object side surface of the fourth lens is convex at the paraxial position, the focal length of the fourth lens is f4, the central radius of curvature of the exit surface of the fourth lens is R7, the central radius of curvature of the object side surface of the fourth lens is R8, and the axial thickness of the fourth lens is d7, satisfying the following relations: 0.36≦f4 / f≦1.30; 0≦(R7+R8) / (R7-R8)≦0.86; 0.02≦d7 / TTL≦0.12.

[0012] Preferably, the exit surface of the fifth lens is concave at the paraxial position, the object side surface of the fifth lens is concave at the paraxial position, the central radius of curvature of the exit surface of the fifth lens is R9, the central radius of curvature of the object side surface of the fifth lens is R10, and the axial thickness of the fifth lens is d9, satisfying the following relations: -1.34≦(R9+R10) / (R9-R10)≦0.03; 0.01≦d9 / TTL≦0.15.

[0013] Preferably, the exit surface of the sixth lens is a convex surface at the paraxial position, the object side surface of the sixth lens is a convex surface at the paraxial position, the focal length of the sixth lens is f6, the axial thickness of the sixth lens is d11, and the following relations are satisfied: 0.23≦f6 / f≦0.81; 0.03≦d11 / TTL≦0.18.

[0014] Preferably, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all made of glass.

[0015] The beneficial effects of the present invention are that the microscope objective lens according to the present invention has excellent optical performance while having characteristics of low distortion, 4.7 to 5 times magnification, and long working distance, and is particularly suitable for use in optical microscope objective lenses. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic diagram illustrating the configuration of a microscope objective lens according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of axial aberration of the microscope objective lens shown in FIG. [Diagram 3] 2 is a schematic diagram of magnification aberration of the microscope objective lens shown in FIG. 1. [Figure 4] 2 is a schematic diagram of the field curvature and distortion of the microscope objective lens shown in FIG. 1. [Diagram 5] FIG. 5 is a schematic diagram showing the configuration of a microscope objective lens according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a schematic diagram of axial aberration of the microscope objective lens shown in FIG. 5. [Figure 7] FIG. 6 is a schematic diagram of magnification aberration of the microscope objective lens shown in FIG. 5. [Figure 8] 6 is a schematic diagram of the field curvature and distortion of the microscope objective lens shown in FIG. 5. [Figure 9] FIG. 11 is a schematic diagram showing the configuration of a microscope objective lens according to a third embodiment of the present invention. [Figure 10] FIG. 10 is a schematic diagram of axial aberration of the microscope objective lens shown in FIG. [Figure 11] FIG. 10 is a schematic diagram of magnification aberration of the microscope objective lens shown in FIG. [Figure 12] 10 is a schematic diagram of the field curvature and distortion of the microscope objective lens shown in FIG. 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The technical solutions in the embodiments of the present invention are described below clearly and completely, but it is clear that the described embodiments are only some of the embodiments of the present invention, and are not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

[0018] (First embodiment) With reference to the accompanying drawings, the present invention provides a microscope objective lens. Fig. 1 shows a microscope objective lens 10 according to a first embodiment of the present invention, which includes six lenses. Specifically, the microscope objective lens 10 includes, in order from the exit side to the object side, an aperture ST, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and an object surface.

[0019] The central radius of curvature of the exit surface of the sixth lens L6 is defined as R11, and the central radius of curvature of the object side surface of the sixth lens L6 is defined as R12, and the following relational expression is satisfied: -5.00≦R11 / R12≦-1.50. By defining the shape of the sixth lens L6, it contributes to a smooth transition of the exiting light ray within this range, which is advantageous for improving image quality.

[0020] The axial distance from the object surface of the microscope objective lens 10 to the object side surface of the sixth lens L6 is defined as WD, that is, the working distance, and the axial distance from the object surface of the microscope objective lens to the exit surface of the first lens is defined as TTL, that is, the total optical length is defined as TTL, and the following relational expression is satisfied: 0.40≦WD / TTL≦0.60. The working distance WD is the distance from the observed object to the object side surface closest to the object, and the TTL is the distance from the object to the objective lens to the farthest lens. If it is lower than the lower limit of the conditional expression, the distance between the microscope objective lens and the object is too narrow, and the operability of the microscope using this objective lens is deteriorated. On the other hand, if it is higher than the upper limit of the conditional expression, the space occupied by the lens part is insufficient, so the thickness of the lens that can be arranged is limited, and it becomes difficult to correct spherical aberration and chromatic aberration.

[0021] The central radius of curvature of the exit surface of the first lens L1 is defined as R1, the refractive index of the first lens L1 is defined as n1, and the focal length of the microscope objective lens 10 is defined as f, and the following relational expression is satisfied: 1.00≦R1 / ((n1-1)*f)≦4.00. By rationally controlling the relationship between the shape of the first lens, the refractive index of the material, and the focal length of the microscope objective lens within this range, the flow of light rays can be controlled so that the exit light rays are smooth.

[0022] The axial thickness of the third lens L3 is defined as d5, the axial distance from the second lens L2 to the third lens L3 is defined as d4, and the following relational expression is satisfied: 2.00≦d5 / d4≦6.00. By specifying the ratio of the thickness of the third lens L3 to the air gap between the second lens L2 and the third lens L3, it is advantageous to assemble the lenses within the range of the conditional expression.

[0023] When the focal length of the microscope objective lens 10 of the present invention, the focal length of each lens, the total optical length of the microscope objective lens, working distance, axial thickness, numerical aperture, Abbe number of each lens, and central radius of curvature satisfy the above relationship, the microscope objective lens 10 can satisfy the design requirements of low distortion, 4.7 to 5x magnification, and long working distance.

[0024] In addition, the focal length of the fifth lens is defined as f5, and the following relational expression is satisfied: -0.30≦f5 / f≦-0.20. By specifying the ratio between the focal length of the fifth lens L5 and the focal length of the microscope objective lens 10, the diopter (focal power) of the system can be reasonably allocated within the range of the conditional expression, which is favorable for correcting the image dispersion and distortion of the microscope objective lens, and the distortion is |Distortion|≦0.25%, which can effectively reduce the occurrence of dark angles.

[0025] The central radius of curvature of the exit surface of the fourth lens L4 is defined as R7, and the following relational expression is satisfied: 0.70≦R7 / f≦2.10. By specifying the shape of the image side surface of the fourth lens L4, it contributes to a smooth transition of light within the range of the conditional expression, and within this range, the chromatic aberration of the microscope objective lens can be efficiently corrected, and |LC|≦0.6 μm.

[0026] In this embodiment, the exit surface of the first lens L1 is convex at the paraxial position, and the object side surface of the first lens L1 is convex at the paraxial position. The first lens L1 has a positive refractive power. In any other embodiment, the exit surface and the object side surface of the first lens L1 may be arranged in other concave or convex distributions.

[0027] The focal length of the first lens L1 is defined as f1, and the following relational expression is satisfied: 0.35≦f1 / f≦1.08, which specifies the positive refractive power of the first lens L1. It is advantageous to control the total optical length of the microscope objective lens within this range. In addition, it is preferable to satisfy 0.56≦f1 / f≦0.87.

[0028] The radius of curvature of the center of the exit surface of the first lens L1 is defined as R1, and the radius of curvature of the center of the object side surface of the first lens L1 is defined as R2, and the following relational expression is satisfied: -0.71≦(R1+R2) / (R1-R2)≦0.97. The shape of the first lens is appropriately controlled so that the first lens can efficiently correct the system spherical aberration. In addition, it is preferable to satisfy -0.44≦(R1+R2) / (R1-R2)≦0.78.

[0029] The axial thickness of the first lens L1 is defined as d1, and the following relational expression is satisfied: 0.02≦d1 / TTL≦0.11. This is advantageous for controlling the total optical length of the microscope objective lens. In addition, it is preferable that the relational expression is satisfied: 0.04≦d1 / TTL≦0.09.

[0030] In this embodiment, preferably, the exit surface of the second lens L2 is concave at the paraxial position, and the object side surface of the second lens L2 is concave at the paraxial position. The second lens L2 has negative refractive power. In any other embodiment, the exit surface and the object side surface of the second lens L2 may be arranged in other concave or convex distributions.

[0031] The focal length of the second lens L2 is f2, and the following relational expression is satisfied: -0.75≦f2 / f≦-0.22. By controlling the negative diopter of the second lens L2 within an appropriate range, it is advantageous to correct the aberration of the optical system. Also, it is preferable that the relational expression is satisfied: -0.47≦f2 / f≦-0.28.

[0032] The radius of curvature of the center of the exit surface of the second lens L2 is defined as R3, and the radius of curvature of the center of the object side surface of the second lens L2 is defined as R4, and the following relational expression is satisfied: -0.56≦(R3+R4) / (R3-R4)≦0. This defines the shape of the second lens L2, and within this range, it is advantageous for improving the problem of axial chromatic aberration. In addition, it is preferable to satisfy -0.35≦(R3+R4) / (R3-R4)≦0.

[0033] The axial thickness of the second lens L2 is d3, which satisfies the following relation: 0.01≦d3 / TTL≦0.07. This makes it easy to control the total optical length of the microscope objective lens. Preferably, the relation 0.02≦d3 / TTL≦0.05 is satisfied.

[0034] In this embodiment, preferably, the exit surface of the third lens L3 is convex at the paraxial position, and the object side surface of the third lens L3 is convex at the paraxial position. The third lens L3 has a positive refractive power. In any other embodiment, the exit surface and the object side surface of the third lens L3 may be arranged in other concave or convex distributions.

[0035] The focal length of the third lens L3 is defined as f3, and the following relational expression is satisfied: 0.26≦f3 / f≦0.94. By controlling the positive diopter of the third lens L3 within an appropriate range, it is advantageous to correct the aberration of the optical system. Also, it is preferable that the relational expression is satisfied: 0.41≦f3 / f≦0.76.

[0036] The radius of curvature of the exit surface of the third lens L3 is defined as R5, and the radius of curvature of the object side surface of the third lens L3 is defined as R6, and the following relational expression is satisfied: 0.43≦(R5+R6) / (R5-R6)≦1.52. This allows the shape of the third lens L3 to be effectively controlled, contributing to the molding of the third lens L3 and preventing molding defects and stress caused by the surface curvature of the third lens L3 becoming excessively large. In addition, it is preferable to satisfy 0.69≦(R5+R6) / (R5-R6)≦1.22.

[0037] The axial thickness of the third lens L3 is defined as d5, and the following relational expression is satisfied: 0.04≦d5 / TTL≦0.17. This makes it easy to control the total optical length of the microscope objective lens. In addition, it is preferable that the following relational expression is satisfied: 0.06≦d5 / TTL≦0.13.

[0038] In this embodiment, the exit surface of the fourth lens L4 is convex at the paraxial position, and the object side surface of the fourth lens L4 is convex at the paraxial position. The fourth lens L4 has a positive refractive power. In any other embodiment, the exit surface and the object side surface of the fourth lens L4 may be arranged in other concave or convex distributions.

[0039] The focal length of the fourth lens L4 is defined as f4, and satisfies the following relationship: 0.36≦f4 / f≦1.30. With a reasonable distribution of diopters, the system has better imaging quality and low sensitivity. Also, preferably, it satisfies 0.58≦f4 / f≦1.04.

[0040] The radius of curvature of the exit surface of the fourth lens L4 is defined as R7, and the radius of curvature of the object side surface of the fourth lens L4 is defined as R8, and the following relational expression is satisfied: 0≦(R7+R8) / (R7-R8)≦0.86. This defines the shape of the fourth lens L4, and within this range, it is advantageous for correcting problems such as off-axis angle of view aberration. Also, it is preferable to satisfy 0≦(R7+R8) / (R7-R8)≦0.69.

[0041] The axial thickness of the fourth lens L4 is defined as d7, and the following relational expression is satisfied: 0.02≦d7 / TTL≦0.12. This defines the ratio of the axial thickness of the fourth lens L4 to the total optical length TTL of the microscope objective lens 10, which is advantageous for controlling the total optical length of the microscope objective lens. Preferably, the relational expression satisfies 0.04≦d7 / TTL≦0.10.

[0042] In this embodiment, the exit surface of the fifth lens L5 is preferably concave at the paraxial position, and the object side surface of the fifth lens L5 is preferably concave at the paraxial position. The fifth lens L5 has negative refractive power. In any other embodiment, the exit surface and the object side surface of the fifth lens L5 may be arranged in other concave or convex distributions.

[0043] The radius of curvature of the center of the exit surface of the fifth lens L5 is defined as R9, and the radius of curvature of the center of the object side surface of the fifth lens L5 is defined as R10, and the following relational expression is satisfied: -1.34≦(R9+R10) / (R9-R10)≦0.03. This defines the shape of the fifth lens L5, and within this range, it is advantageous for correcting problems such as aberrations of off-axis angles of view. In addition, it is preferable to satisfy -0.84≦(R9+R10) / (R9-R10)≦0.02.

[0044] The axial thickness of the fifth lens L5 is defined as d9, and the following relational expression is satisfied: 0.01≦d9 / TTL≦0.15. This makes it easy to control the total optical length of the microscope objective lens. In addition, it is preferable that the following relational expression is satisfied: 0.02≦d9 / TTL≦0.12.

[0045] In this embodiment, the exit surface of the sixth lens L6 is convex at the paraxial position, and the object side surface of the sixth lens L6 is convex at the paraxial position. The sixth lens L6 has a positive refractive power. In any other embodiment, the exit surface and the object side surface of the sixth lens L6 may be arranged in other concave or convex distributions.

[0046] The focal length of the sixth lens L6 is f6, which satisfies the following relationship: 0.23≦f6 / f≦0.81. With a reasonable distribution of diopters, the system has better imaging quality and low sensitivity. It is also preferable to satisfy 0.37≦f6 / f≦0.65.

[0047] The axial thickness of the sixth lens L6 is defined as d11, and the following relational expression is satisfied: 0.03≦d11 / TTL≦0.18. This defines the ratio of the axial thickness of the sixth lens L6 to the total optical length TTL of the microscope objective lens 10, which is advantageous for controlling the total optical length of the microscope objective lens. In addition, it is preferable that the following relational expression is satisfied: 0.05≦d11 / TTL≦0.15.

[0048] In this embodiment, the total optical length TTL of the microscope objective lens 10 is 95 mm or less.

[0049] In this embodiment, the viewing angle of the microscope objective lens 10 is 6.40° or more.

[0050] In this embodiment, the image height of the microscope objective lens 10 is 2.40 mm or more.

[0051] In this embodiment, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all made of glass.

[0052] The microscope objective lens 10 of the present invention will be described below with reference to examples. The focal length, axial distance, central radius of curvature, and axial thickness position are all in mm.

[0053] TTL: total optical length (the axial distance from the exit surface of the first lens L1 to the object surface), in mm;

[0054] Table 1 shows design data for the microscope objective lens 10 according to the first embodiment of the present invention.

[0055] [Table 1]

[0056] Here, the meanings of the symbols are as follows:

[0057] ST: aperture; R: radius of curvature at the center of the optical surface; R1: the central curvature radius of the exit surface of the first lens L1; R2: the central radius of curvature of the object side of the first lens L1; R3: the central curvature radius of the exit surface of the second lens L2; R4: the central radius of curvature of the object side of the second lens L2; R5: central curvature radius of the exit surface of the third lens L3; R6: the central radius of curvature of the object side of the third lens L3; R7: central curvature radius of the exit surface of the fourth lens L4; R8: the central radius of curvature of the object side of the fourth lens L4; R9: central curvature radius of the exit surface of the fifth lens L5; R10: the central radius of curvature of the object side of the fifth lens L5; R11: the central curvature radius of the exit surface of the sixth lens L6; R12: the central radius of curvature of the object side of the sixth lens L6; d: Axial thickness of the lens, axial distance between the lenses; dST: the axial distance from the aperture stop ST to the exit surface of the first lens; d1: axial thickness of the first lens L1; d2: the axial distance from the object side surface of the first lens L1 to the exit surface of the second lens L2; d3: axial thickness of the second lens L2; d4: the axial distance from the object side surface of the second lens L2 to the exit surface of the third lens L3; d5: axial thickness of the third lens L3; d6: the axial distance from the object side surface of the third lens L3 to the exit surface of the fourth lens L4; d7: Axial thickness of the fourth lens L4; d8: the axial distance from the object side surface of the fourth lens L4 to the exit surface of the fifth lens L5; d9: Axial thickness of the fifth lens L5; d10: the axial distance from the object side surface of the fifth lens L5 to the sixth lens L6; d11: Axial thickness of the sixth lens L6; d12: Axial distance from the object side of the sixth lens L6 to the object surface; Nd: refractive index of d line; n1: refractive index of the first lens L1 at the d line; n2: refractive index of the second lens L2 at the d line; n3: refractive index of the third lens L3 at the d line; n4: refractive index of the fourth lens L4 at the d line; n5: refractive index of the fifth lens L5 at the d line; n6: refractive index of the sixth lens L6 at the d line; vd: Abbe number; v1: Abbe number of the first lens L1; v2: Abbe number of the second lens L2; v3: Abbe number of the third lens L3; v4: Abbe number of the fourth lens L4; v5: Abbe number of the fifth lens L5; v6: Abbe number of the sixth lens L6.

[0058] 2 and 3 are schematic diagrams showing axial aberration and lateral chromatic aberration after light of wavelengths 486 nm, 588 nm, and 656 nm passes through the microscope objective lens 10 of the first embodiment. Fig. 4 is a schematic diagram showing field curvature and distortion after light of wavelength 588 nm passes through the microscope objective lens 10 of the first embodiment. In Fig. 4, field curvature S is the field curvature in the axial direction, and T is the field curvature in the meridian direction.

[0059] Table 4, which will be shown later, shows various numerical values ​​in each of Examples 1, 2, and 3, and values ​​corresponding to parameters defined by conditional expressions.

[0060] As shown in Table 4, the first embodiment satisfies each of the conditional expressions.

[0061] In this embodiment, the microscope objective lens 10 has an entrance pupil diameter ENDP of 11.320 mm, a total field of view image height IH of 2.400 mm, a diagonal field of view angle FOV of 6.88°, a numerical aperture NA of 0.14 mm, a long working distance, and sufficient correction of axial and off-axial chromatic aberrations, providing excellent optical characteristics.

[0062] Second embodiment The second embodiment is basically the same as the first embodiment, and the symbols have the same meanings as in the first embodiment. Please refer to FIG. 5 for the configuration of the microscope objective lens 20 according to the second embodiment. Only the differences will be listed below.

[0063] Table 2 shows design data of the microscope objective lens 20 according to the second embodiment of the present invention.

[0064] [Table 2]

[0065] 6 and 7 are schematic diagrams showing magnification aberration and axial aberration after light of wavelengths 435 nm, 588 nm, and 656 nm passes through the microscope objective lens 20 of the second embodiment. Fig. 8 is a schematic diagram showing field curvature and distortion after light of wavelength 588 nm passes through the microscope objective lens 20 of the second embodiment. In Fig. 8, field curvature S is the field curvature in the axial direction, and T is the field curvature in the meridian direction.

[0066] As shown in Table 4, the second embodiment satisfies each of the conditional expressions.

[0067] In this embodiment, the microscope objective lens has a pupil diameter of 10,700 mm, a total field of view image height of 2,400 mm, a diagonal field of view angle of 6.52°, a numerical aperture NA of 0.13 mm, a long working distance, and sufficient correction of axial and off-axial chromatic aberrations, providing excellent optical characteristics.

[0068] (Third embodiment) The third embodiment is basically the same as the first embodiment, and the symbols have the same meanings as in the first embodiment. In the third embodiment, the exit surface of the third lens L3 is concave at the paraxial position. Please refer to FIG. 9 for the configuration of the microscope objective lens 30 according to the third embodiment. Only the differences will be listed below.

[0069] Table 3 shows design data of the microscope objective lens 30 according to the third embodiment of the present invention.

[0070] [Table 3]

[0071] Fig. 10 and Fig. 11 are schematic diagrams showing magnification aberration and axial aberration after light of wavelengths 435 nm, 588 nm, and 656 nm passes through the microscope objective lens 30 of the third embodiment. Fig. 12 is a schematic diagram showing field curvature and distortion after light of wavelength 588 nm passes through the microscope objective lens 30 of the third embodiment. In Fig. 12, field curvature S is the field curvature in the axial direction, and T is the field curvature in the meridian direction.

[0072] As shown in Table 4, the third embodiment satisfies each of the conditional expressions.

[0073] In this embodiment, the microscope objective lens has a pupil diameter of 10.240 mm, a full-field image height of 2.400 mm, a diagonal field angle of 6.48°, a long working distance, a numerical aperture NA of 0.120 mm, and excellent optical properties with sufficiently corrected axial and off-axial chromatic aberrations.

[0074] [Table 4]

[0075] The above-described embodiments are specific embodiments for realizing the present invention, and it will be understood by those skilled in the art that various changes in form and details can be made in practical application without departing from the spirit and scope of the present invention.

Claims

1. 1. A microscope objective lens, comprising: The microscope objective lens is arranged in the following order from the exit side to the object side: The optical system includes a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, and a sixth lens having a positive refractive power, A microscope objective lens characterized in that a central radius of curvature of the exit surface of the sixth lens is R11, a central radius of curvature of the object side surface of the sixth lens is R12, an axial distance from the object surface of the microscope objective lens to the object side surface of the sixth lens is WD, an axial distance from the object surface of the microscope objective lens to the exit surface of the first lens is TTL, a central radius of curvature of the exit surface of the first lens is R1, a refractive index of the first lens is n1, a focal length of the microscope objective lens is f, an axial thickness of the third lens is d5, and an axial distance from the second lens to the third lens is d4, and the following relationship is satisfied. -5.00≦R11 / R12≦-1.50 0.40≦WD / TTL≦0.60 1.00≦R1 / ((n1-1)*f)≦4.00 2.00≦d5 / d4≦6.00

2. 2. The microscope objective lens according to claim 1, wherein the focal length of the fifth lens is f5 and the following relation is satisfied: −0.30≦f5 / f≦−0.20

3. 2. The microscope objective lens according to claim 1, wherein the central radius of curvature of the exit surface of the fourth lens is R7, and the following relational expression is satisfied: 0.70≦R7 / f≦2.10

4. an exit surface of the first lens is a convex surface at a paraxial position, and an object side surface of the first lens is a convex surface at a paraxial position, The microscope objective lens of claim 1, characterized in that the central radius of curvature of the exit surface of the first lens is R1, the central radius of curvature of the object side surface of the first lens is R2, the axial thickness of the first lens is d1, and the focal length of the first lens is f1, satisfying the following relationship. 0.35≦f1 / f≦1.08 -0.71≦(R1+R2) / (R1-R2)≦0.97 0.02≦d1 / TTL≦0.11

5. an exit surface of the second lens is concave at a paraxial position, and an object side surface of the second lens is concave at a paraxial position; The microscope objective lens of claim 1, characterized in that the central radius of curvature of the exit surface of the second lens is R3, the central radius of curvature of the object side surface of the second lens is R4, the focal length of the second lens is f2, and the axial thickness of the second lens is d3, satisfying the following relationship. −0.75≦f2 / f≦−0.22 -0.56≦(R3+R4) / (R3-R4)≦0 0.01≦d3 / TTL≦0.07

6. the object side surface of the third lens is a convex surface at a paraxial position; The microscope objective lens of claim 1, characterized in that the central radius of curvature of the exit surface of the third lens is R5, the central radius of curvature of the object side surface of the third lens is R6, and the focal length of the third lens is f3, satisfying the following relationship. 0.26≦f3 / f≦0.94 0.43≦(R5+R6) / (R5-R6)≦1.52 0.04≦d5 / TTL≦0.17

7. an exit surface of the fourth lens is a convex surface at a paraxial position, and an object side surface of the fourth lens is a convex surface at a paraxial position, The microscope objective lens of claim 1, characterized in that the focal length of the fourth lens is f4, the central radius of curvature of the exit surface of the fourth lens is R7, the central radius of curvature of the object side surface of the fourth lens is R8, and the axial thickness of the fourth lens is d7, satisfying the following relationship. 0.36≦f4 / f≦1.30 0≦(R7+R8) / (R7-R8)≦0.86 0.02≦d7 / TTL≦0.12

8. an exit surface of the fifth lens is concave at a paraxial position, and an object side surface of the fifth lens is concave at a paraxial position; The microscope objective lens of claim 1, characterized in that the central radius of curvature of the exit surface of the fifth lens is R9, the central radius of curvature of the object side surface of the fifth lens is R10, and the axial thickness of the fifth lens is d9, which satisfy the following relationship. -1.34≦(R9+R10) / (R9-R10)≦0.03 0.01≦d9 / TTL≦0.15

9. an exit surface of the sixth lens is a convex surface at a paraxial position, and an object side surface of the sixth lens is a convex surface at a paraxial position, 2. The microscope objective lens according to claim 1, wherein the focal length of the sixth lens is f6, the axial thickness of the sixth lens is d11, and the following relational expression is satisfied: 0.23≦f6 / f≦0.81 0.03≦d11 / TTL≦0.18

10. 2. The microscope objective lens according to claim 1, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all made of glass.

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