Microscope Objectives

Abstract

To provide an optical lens, in particular a microscope objective lens for use in devices such as a microscope.SOLUTION: A microscope objective lens disclosed herein comprises 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 negative refractive power, and a fifth lens having positive refractive power, arranged in order from the exit pupil side to the object side, and satisfies the following conditional expressions: 0.68≤f3 / f≤2.00, -2.20≤f2 / f1≤-1.40, 0.15≤WD / TTL≤0.35, 6.00≤f*NA≤9.00, where f represents a focal length of the microscope objective lens, f1 represents a focal length of the first lens, f2 represents a focal length of the second lens, f3 represents a focal length of the third lens, WD represents an axial distance from an object-side surface of the microscope objective lens to an object-side surface of the fifth lens, NA represents a numerical aperture, and TTL represents a total optical length. The microscope objective lens of the present invention features low distortion, 1.5X magnification, and long working length.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, the demand for microscope lenses has been increasing. However, due to the constraints of the optical structure of general microscope lenses, distortion aberration occurs within the field of view of the microscope. Meanwhile, since microscope lenses are composed of multiple lenses, their length is inevitably affected. Therefore, the working distance of microscope lenses with long structures is also short, and the magnification is also affected by the working distance, which is disadvantageous for operators to use.

[0003] With the development of technology and the increasing diversity of user needs, the requirements for the observation quality of microscope lenses in scientific research are increasing, and there is a strong demand for microscope lenses with excellent optical properties, low distortion, high magnification, and long working distance. Summary of the Invention [Problem to be solved by the invention]

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

[0005] In order to solve the above technical problems, the present invention provides an objective lens for a microscope, the objective lens for a microscope comprising, in order from an exit pupil 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 negative refractive power, and a fifth lens having positive refractive power, When the focal length of the microscope objective lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the axial distance from the object surface of the microscope objective lens to the object side surface of the fifth lens is WD, the numerical aperture of the microscope objective lens is NA, and the optical length of the microscope objective lens is TTL, the following conditional formulas (1) to (4) are satisfied. 0.68≦f3 / f≦2.00 (1) -2.20≦f2 / f1≦-1.40 (2) 0.15≦WD / TTL≦0.35 (3) 6.00≦f*NA≦9.00 (4)

[0006] Preferably, when the Abbe number of the first lens is v1 and the Abbe number of the second lens is v2, the following conditional expression (5) is satisfied. 35.00≦v1-v2 (5)

[0007] Preferably, when the central radius of curvature of the exit pupil surface of the fifth lens is R9 and the central radius of curvature of the object side surface of the fifth lens is R10, the following conditional expression (6) is satisfied. -5.00≦R10 / R9≦-1.50 (6)

[0008] Preferably, the first lens has an exit pupil surface that is convex on the paraxial direction, and the first lens has an object side surface that is convex on the paraxial direction, When the central radius of curvature of the exit pupil surface of the first lens is R1, the central radius of curvature of the object side surface of the first lens is R2, and the axial thickness of the first lens is d1, the following conditional expressions (7) to (9) are satisfied. 0.08≦f1 / f≦0.29 (7) -0.44≦(R1+R2) / (R1-R2)≦-0.13 (8) 0.02≦d1 / TTL≦0.11 (9)

[0009] Preferably, the second lens has an exit pupil surface that is a paraxial concave surface, and the second lens has an object side surface that is a paraxial convex surface, When the axial thickness of the second lens is d3, the central radius of curvature of the exit pupil surface of the second lens is R3, the central radius of curvature of the object side surface of the second lens is R4, and the axial thickness of the second lens is d3, the following conditional expressions (10) to (12) are satisfied. -0.74≦f2 / f≦-0.22 (10) -3.86≦(R3+R4) / (R3-R4)≦-0.71 (11) 0.01≦d3 / TTL≦0.12 (12)

[0010] Preferably, the third lens has an exit pupil surface which is a concave surface in the paraxial direction, and the third lens has an object side surface which is a convex surface in the paraxial direction, When the central radius of curvature of the exit pupil 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 axial thickness of the third lens is d5, the following conditional expressions (13) and (14) are satisfied. 1.25≦(R5+R6) / (R5-R6)≦20.05 (13) 0.00≦d5 / TTL≦0.02 (14)

[0011] Preferably, when the focal length of the fourth lens is f4, the central radius of curvature of the exit pupil 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, the following conditional expressions (15) to (17) are satisfied. -0.37≦f4 / f≦-0.09 (15) -6.00≦(R7+R8) / (R7-R8)≦-0.65 (16) 0.01≦d7 / TTL≦0.12 (17)

[0012] Preferably, the fifth lens has an exit pupil surface that is convex on the paraxial direction, and the fifth lens has an object side surface that is convex on the paraxial direction, When the focal length of the fifth lens is f5, the central radius of curvature of the exit pupil 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, the following conditional expressions (18) to (20) are satisfied. 0.21≦f5 / f≦1.09 (18) -1.33≦(R9+R10) / (R9-R10)≦-0.13 (20) 0.01≦d9 / TTL≦0.12 (19)

[0013] Preferably, at least one of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens is made of glass. Effect of the Invention

[0014] The beneficial effects of the present invention are as follows: The objective lens for microscopes according to the present invention has excellent optical performance, and has the characteristics of low distortion, 1.5 times magnification and long working distance, and is particularly applicable to the objective lens for optical microscopes. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing the structure of a microscope objective lens according to a first embodiment of the present invention. [Diagram 2] 2 is a schematic diagram showing lateral chromatic aberration of the microscope objective lens shown in FIG. 1. [Diagram 3] 2 is a schematic diagram showing the axial chromatic aberration of the microscope objective lens shown in FIG. 1. [Figure 4] 2 is a schematic diagram showing the field curvature and distortion of the microscope objective lens shown in FIG. 1. [Diagram 5] 5 is a schematic diagram showing the structure of a microscope objective lens according to a second embodiment of the present invention. FIG. [Figure 6] 6 is a schematic diagram showing lateral chromatic aberration of the microscope objective lens shown in FIG. 5. [Figure 7] 6 is a schematic diagram showing the axial chromatic aberration of the microscope objective lens shown in FIG. 5. [Figure 8] 6 is a schematic diagram showing the field curvature and distortion of the microscope objective lens shown in FIG. 5. [Figure 9] 5 is a schematic diagram showing the structure of a microscope objective lens according to a third embodiment of the present invention. FIG. [Figure 10]FIG. 10 is a schematic diagram showing chromatic aberration of magnification of the microscope objective lens shown in FIG. [Figure 11] 10 is a schematic diagram showing the axial chromatic aberration of the microscope objective lens shown in FIG. [Figure 12] 10 is a schematic diagram showing the field curvature and distortion of the microscope objective lens shown in FIG. 9. [Figure 13] FIG. 11 is a schematic diagram showing the structure of a microscope objective lens according to a fourth embodiment of the present invention. [Figure 14] 14 is a schematic diagram showing chromatic aberration of magnification of the microscope objective lens shown in FIG. 13. [Figure 15] 14 is a schematic diagram showing the axial chromatic aberration of the microscope objective lens shown in FIG. 13. [Figure 16] 14 is a schematic diagram showing the field curvature and distortion of the microscope objective lens shown in FIG. 13. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The following provides a clear and complete description of the technical solutions in the embodiments of the present invention, and it is obvious that the described embodiments are only some of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments that a person skilled in the art can obtain without creative labor are all included in the protection scope of the present invention.

[0017] (First embodiment) As shown in the 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 is composed of five lenses. Specifically, the microscope objective lens 10 is composed of, in order from the exit pupil to the object side, a diaphragm ST, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and an object plane OBJ.

[0018] When the focal length of the entire microscope objective lens 10 is f and the focal length of the third lens L3 is f3, the conditional expression 0.68≦f3 / f≦2.00 is satisfied. This expression specifies the ratio between the focal length of the third lens L3 and the focal length of the entire system, and this conditional expression can correct aberrations to ensure imaging quality and effectively reduce the overall length of the optical system.

[0019] When the focal length of the first lens L1 is f1 and the focal length of the second lens L2 is f2, the conditional formula -2.20≦f2 / f1≦-1.40 is satisfied. The ratio of the focal length of the second lens to the focal length of the first lens is specified. By rationally allocating the optical focal length of the system, the system has excellent imaging quality and low sensitivity.

[0020] When the axial distance from the object surface OBJ of the microscope objective lens 10 to the object side surface of the fifth lens is WD and the optical length of the microscope objective lens 10 is TTL, the conditional formula 0.15≦WD / TTL≦0.35 is satisfied, and the TTL optical length is the distance on the optical axis from the object to the lens surface closest to the aperture. If the lower limit of the conditional formula is exceeded, the distance between the microscope objective lens and the object becomes too narrow, and the operability of the microscope using the objective lens is deteriorated. On the other hand, if the upper limit of the conditional formula is exceeded, the space occupied by the lens part becomes insufficient, so the thickness of the lens that can be arranged and the optical path are limited, making it difficult to correct spherical aberration and chromatic aberration.

[0021] When the numerical aperture of the microscope objective lens 10 is NA, the conditional formula 6.00≦f*NA≦9.00 is satisfied. This conditional formula relates to the field of view and image brightness that can be observed with the microscope objective lens, and if the lower limit is exceeded, the magnification of the microscope objective lens will inevitably increase and the observable field of view will become narrower, while if the upper limit is exceeded, the microscope objective lens will become larger and it will become difficult to maintain the focal length of the microscope objective lens.

[0022] When the Abbe number of the first lens is v1 and the Abbe number of the second lens is v2, the conditional formula 35.00≦v1-v2 is satisfied. Within this range of the conditional formula, the chromatic aberration of the system can be effectively corrected, and in particular, |LC|≦5 μm.

[0023] When the central radius of curvature of the exit pupil surface of the fifth lens is R9 and the central radius of curvature of the object side surface of the fifth lens is R10, the conditional formula -5.00≦R10 / R9≦-1.50 is satisfied. By specifying the shape of the fifth lens L5, it is possible to alleviate the degree of deflection of light passing through the lens within the range of the conditional formula, which is useful for correcting the astigmatism and distortion of the microscope objective lens, and the distortion is |Distortion|≦0.2%, reducing the possibility of vignetting.

[0024] When the focal length of the microscope objective lens 10 of the present invention, the focal length of each lens, the optical length, working distance, axial thickness, numerical aperture, Abbe number and central curvature radius of each lens of the microscope objective lens satisfy the above conditional expressions, the microscope objective lens 10 can meet the design needs of low distortion, 1.5x magnification and long working distance.

[0025] In this embodiment, it is preferable that the exit pupil surface of the first lens L1 is a convex surface on the paraxial direction, and the object side surface of the first lens L1 is a convex surface on the paraxial direction. The first lens L1 has positive refractive power.

[0026] When the focal length of the first lens L1 is f1, the conditional expression 0.08≦f1 / f≦0.29 is satisfied, and the positive refractive power of the first lens L1 is specified. If the lower limit of the specified value is exceeded, it is advantageous for making the lens extremely thin, but the positive refractive power of the first lens L1 becomes too strong, making it difficult to correct aberrations and disadvantageous for making the lens wider-angle. Conversely, if the upper limit of the specified value is exceeded, the positive refractive power of the first lens becomes too weak, making it difficult to make the lens extremely thin. Preferably, 0.14≦f1 / f≦0.23.

[0027] When the central radius of curvature of the exit pupil surface of the first lens L1 is R1 and the central radius of curvature of the object side surface of the first lens L1 is R2, the first lens can effectively correct spherical aberration by satisfying the conditional expression -0.44≦(R1+R2) / (R1-R2)≦-0.13 and rationally controlling the shape of the first lens, preferably -0.28≦(R1+R2) / (R1-R2)≦-0.17.

[0028] When the axial thickness of the first lens L1 is d1, the condition 0.02≦d1 / TTL≦0.11 is satisfied, which helps to realize an extremely thin structure. Preferably, 0.04≦d1 / TTL≦0.09 is satisfied.

[0029] In this embodiment, it is preferable that the exit pupil surface of the second lens L2 is a paraxial concave surface, and the object side surface of the second lens L2 is a paraxial convex surface. The second lens L2 has negative refractive power.

[0030] When the focal length of the second lens L2 is f2, the conditional expression -0.74≦f2 / f≦-0.22 is satisfied, and the positive power of the second lens L2 is controlled within a reasonable range, which is useful for correcting the aberration of the optical system, and preferably -0.47≦f2 / f≦-0.27.

[0031] When the central radius of curvature of the exit pupil surface of the second lens L2 is R3 and the central radius of curvature of the object side surface of the second lens L2 is R4, the conditional expression -3.86≦(R3+R4) / (R3-R4)≦-0.71 is satisfied, which defines the shape of the second lens L2, and within this range, it is useful for correcting the problem of axial chromatic aberration as lenses become thinner and wider in angle. Preferably, -2.41≦(R3+R4) / (R3-R4)≦-0.89.

[0032] When the axial thickness of the second lens L2 is d3, the condition 0.01≦d3 / TTL≦0.12 is satisfied, which helps to realize an extremely thin structure. Preferably, 0.01≦d3 / TTL≦0.10.

[0033] In this embodiment, preferably, the exit pupil surface of the third lens L3 is a paraxial concave surface, and the object side surface of the third lens L3 is a paraxial convex surface. The third lens L3 has positive refractive power.

[0034] When the central radius of curvature of the exit pupil surface of the third lens L3 is R5 and the central radius of curvature of the object side surface of the third lens L3 is R6, the conditional formula 1.25≦(R5+R6) / (R5-R6)≦20.05 is satisfied, the shape of the third lens L3 can be effectively controlled, which is helpful for molding the third lens L3 and can prevent molding defects and stress generation due to the surface curvature of the third lens L3 being too large. Preferably, 1.99≦(R5+R6) / (R5-R6)≦16.04.

[0035] When the axial thickness of the third lens L3 is d5, the condition 0.00≦d5 / TTL≦0.02 is satisfied, which helps to realize an extremely thin structure. Preferably, 0.01≦d5 / TTL≦0.02 is satisfied.

[0036] In this embodiment, the exit pupil surface of the fourth lens L4 is a paraxial concave surface, and the object side surface of the fourth lens L4 is a paraxial concave surface. The fourth lens L4 has a negative refractive power. In other optional embodiments, the exit pupil surface and the object side surface of the fourth lens L4 may be arranged in other concave and convex distribution patterns.

[0037] When the focal length of the fourth lens L4 is f4, the condition -0.37≦f4 / f≦-0.09 is satisfied, and the power is distributed reasonably so that the system has excellent imaging quality and low sensitivity, preferably -0.23≦f4 / f≦-0.11.

[0038] When the central radius of curvature of the exit pupil surface of the fourth lens L4 is R7 and the central radius of curvature of the object side surface of the fourth lens L4 is R8, the conditional formula -6.00≦(R7+R8) / (R7-R8)≦-0.65 is satisfied, which defines the shape of the fourth lens L4, and within this range, as lenses become thinner and wider in angle, it is useful for correcting aberrations of the off-axis angle of view, etc. Preferably, -3.75≦(R7+R8) / (R7-R8)≦-0.81.

[0039] When the axial thickness of the fourth lens L4 is d7, the conditional expression 0.01≦d7 / TTL≦0.12 is satisfied, which defines the ratio between the axial thickness of the fourth lens L4 and the optical length TTL of the microscope objective lens 10, and helps to realize an extremely thin lens. Preferably, 0.01≦d7 / TTL≦0.10.

[0040] In this embodiment, it is preferable that the exit pupil surface of the fifth lens L5 is a paraxial convex surface, and the object side surface of the fifth lens L5 is a paraxial convex surface. The fifth lens L5 has positive refractive power.

[0041] When the focal length of the fifth lens L5 is f5, the condition 0.21≦f5 / f≦1.09 is satisfied. Limiting the fifth lens L5 can effectively make the light angle of the microscope lens gentle and reduce the tolerance sensitivity. Preferably, 0.34≦f5 / f≦0.87.

[0042] When the central radius of curvature of the exit pupil surface of the fifth lens L5 is R9 and the central radius of curvature of the object side surface of the fifth lens L5 is R10, the conditional formula -1.33≦(R9+R10) / (R9-R10)≦-0.13 is satisfied, which defines the shape of the fifth lens L5, and within the range of the conditional formula, it is useful for correcting aberrations of off-axis angles of view as lenses become thinner and wider in angle of view. Preferably, -0.83≦(R9+R10) / (R9-R10)≦-0.17.

[0043] When the axial thickness of the fifth lens L5 is d9, the condition 0.01≦d9 / TTL≦0.12 is satisfied, which helps to realize an extremely thin structure. Preferably, 0.02≦d9 / TTL≦0.10.

[0044] In this embodiment, the optical length TTL of the microscope objective lens 10 is 136.25 mm or less, which helps to achieve an extremely thin structure.

[0045] In this embodiment, the aperture F-number of the microscope objective lens 10 is 12.83 or less, which provides excellent imaging performance.

[0046] In this embodiment, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all made of glass.

[0047] The microscope objective lens 10 of the present invention will be described below using examples. The symbols used in each example indicate the following: The focal length, axial distance, central radius of curvature, and axial thickness position are all in mm.

[0048] TTL: Optical length (the axial distance from the exit pupil plane of the first lens L1 to the object plane OBJ) in mm.

[0049] A specific embodiment is described below.

[0050] Table 1 shows design data of the microscope objective lens 10 according to the first embodiment of the present invention.

[0051] [Table 1]

[0052] The meaning of each symbol is as follows: ST:Aperture R: Central radius of curvature at the center of the optical surface R1: Central radius of curvature of the exit pupil surface of the first lens L1 R2: The central radius of curvature of the object side of the first lens L1 R3: The central radius of curvature of the exit pupil 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 pupil surface of the third lens L3 R6: The central radius of curvature of the object side of the third lens L3 R7: The central curvature radius of the exit pupil surface of the fourth lens L4 R8: The central radius of curvature of the object side of the fourth lens L4 R9: The central curvature radius of the exit pupil surface of the fifth lens L5 R10: The central radius of curvature of the object side of the fifth lens L5 d: Axial thickness of lens, axial distance between lenses dST: Axial thickness of aperture ST 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 pupil plane 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 pupil plane 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 pupil plane 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 pupil plane of the fifth lens L5 d9: Axial thickness of the fifth lens L5 d10: Axial distance from the object side surface of the fifth lens L5 to the object surface Nd: Refractive index of the d line n1: refractive index of the d line of the first lens L1 n2: refractive index of the d line of the second lens L2 n3: refractive index of the d line of the third lens L3 n4: Refractive index of the d line of the fourth lens L4 n5: refractive index of the d line of the fifth lens L5 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

[0053] Fig. 2 and Fig. 3 are schematic diagrams showing the lateral chromatic aberration and the axial chromatic aberration of light having wavelengths of 486.1 nm, 587.6 nm, 656.3 nm, 520.0 nm, 435.0 nm, and 700.0 nm after passing through the microscope objective lens 10 according to the first embodiment. Fig. 4 is a schematic diagram showing the field curvature and the distortion aberration of light having wavelength of 587.6 nm after passing through the microscope objective lens 10 according to the first embodiment, where the field curvature S in Fig. 4 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0054] Table 5 described later shows various numerical values ​​in each of Examples 1, 2, 3, and 4 and values ​​corresponding to parameters defined by conditional expressions.

[0055] As shown in Table 5, the first embodiment satisfies each of the conditional expressions.

[0056] In this embodiment, the microscope objective lens has an entrance pupil diameter ENPD of 16.100 mm, a total field of view image height IH of 10.500 mm, a diagonal field angle FOV of 9.02°, a numerical aperture NA of 0.06000 mm, a long working distance, and its axial and off-axial chromatic aberrations are sufficiently corrected, and it has excellent optical properties.

[0057] 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, so the difference is that in the second embodiment, the exit pupil surface of the fourth lens L4 is a paraxial concave surface, and the object side surface of the fourth lens L4 is a paraxial convex surface. The structural form of the microscope objective lens 20 according to the second embodiment is shown in Figure 5, so only the differences are shown below.

[0058] Table 2 shows design data of the microscope objective lens 20 according to the second embodiment of the present invention.

[0059] [Table 2]

[0060] Fig. 6 and Fig. 7 are schematic diagrams showing the lateral chromatic aberration and the axial chromatic aberration of light having wavelengths of 486.1 nm, 587.6 nm, 656.3 nm, 520.0 nm, 435.0 nm, and 700.0 nm after passing through the microscope objective lens 20 according to the second embodiment. Fig. 8 is a schematic diagram showing the field curvature and the distortion aberration of light having wavelength of 587.6 nm after passing through the microscope objective lens 20 according to the second embodiment, where the field curvature S in Fig. 8 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0061] As shown in Table 5, the second embodiment satisfies each of the conditional expressions.

[0062] In this embodiment, the microscope objective lens has an entrance pupil diameter of 12,000 mm, a full field image height of 10,500 mm, a diagonal angle of view of 8.02°, a numerical aperture NA of 0.04000 mm, a long working distance, and its axial and off-axial chromatic aberrations are sufficiently corrected, and it has excellent optical properties.

[0063] 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, so the difference is that in the third embodiment, the exit pupil surface of the fourth lens L4 is a paraxial concave surface, and the object side surface of the fourth lens L4 is a paraxial convex surface. The structural form of the microscope objective lens 30 according to the third embodiment is shown in Figure 9, so only the differences are shown below.

[0064] Table 3 shows design data of the microscope objective lens 30 according to the third embodiment of the present invention.

[0065] [Table 3]

[0066] Fig. 10 and Fig. 11 are schematic diagrams showing the lateral chromatic aberration and the axial chromatic aberration of light having wavelengths of 486.1 nm, 587.6 nm, 656.3 nm, 520.0 nm, 435.0 nm, and 700.0 nm after passing through the microscope objective lens 30 according to the third embodiment. Fig. 12 is a schematic diagram showing the field curvature and the distortion aberration of light having wavelength of 587.6 nm after passing through the microscope objective lens 30 according to the third embodiment, where the field curvature S in Fig. 12 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0067] As shown in Table 5, the third embodiment satisfies each of the conditional expressions.

[0068] In this embodiment, the microscope objective lens has an entrance pupil diameter of 12,000 mm, a full field image height of 10,500 mm, a diagonal angle of view of 8.02°, a long working distance, a numerical aperture NA of 0.06800 mm, and its axial and off-axial chromatic aberrations are sufficiently corrected, and it has excellent optical properties.

[0069] (Fourth embodiment) The fourth embodiment is basically the same as the first embodiment, and the symbols have the same meanings as in the first embodiment, so the difference is that in the fourth embodiment, the exit pupil surface of the fourth lens L4 is a paraxial concave surface, and the object side surface of the fourth lens L4 is a paraxial convex surface. The structural form of the microscope objective lens 40 according to the fourth embodiment is shown in Figure 13, so only the differences are shown below.

[0070] Table 4 shows design data of the microscope objective lens 40 according to the fourth embodiment of the present invention.

[0071] [Table 4]

[0072] Fig. 14 and Fig. 15 are schematic diagrams showing the lateral chromatic aberration and the axial chromatic aberration of light having wavelengths of 486.1 nm, 587.6 nm, 656.3 nm, 520.0 nm, 435.0 nm, and 700.0 nm after passing through the microscope objective lens 40 according to the fourth embodiment. Fig. 16 is a schematic diagram showing the field curvature and the distortion aberration of light having wavelength of 587.6 nm after passing through the microscope objective lens 40 according to the fourth embodiment, where the field curvature S in Fig. 16 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0073] As shown in Table 5, the fourth embodiment satisfies each of the conditional expressions.

[0074] In this embodiment, the microscope objective lens has an entrance pupil diameter of 18,000 mm, a full field image height of 10,500 mm, a diagonal angle of view of 8.51°, a long working distance, a numerical aperture NA of 0.06366 mm, and its axial and off-axial chromatic aberrations are sufficiently corrected, and it has excellent optical properties.

[0075] [Table 5]

[0076] As will be understood by those skilled in the art, the above-described embodiments are specific embodiments for realizing the present invention, and in actual application, various changes in form and details are possible without departing from the spirit and scope of the present invention.

Claims

1. 1. A microscope objective lens, comprising: the microscope objective lens is composed of, in order from an exit pupil 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 negative refractive power, and a fifth lens having positive refractive power; An objective lens for a microscope, characterized in that the following conditional expressions (1) to (4) are satisfied when the focal length of the objective lens for a microscope is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the axial distance from the object surface of the objective lens for a microscope to the object side surface of the fifth lens is WD, the numerical aperture of the objective lens for a microscope is NA, and the optical length of the objective lens for a microscope is TTL. 0.68≦f3 / f≦2.00 (1) −2.20≦f2 / f1≦−1.40 (2) 0.15≦WD / TTL≦0.35 (3) 6.00≦f*NA≦9.00 (4)

2. 2. The objective lens for a microscope according to claim 1, wherein the following conditional expression (5) is satisfied, where v1 is the Abbe number of the first lens and v2 is the Abbe number of the second lens: 35.00≦v1-v2 (5)

3. The objective lens for a microscope according to claim 1, characterized in that when the central radius of curvature of the exit pupil surface of the fifth lens is R9 and the central radius of curvature of the object side surface of the fifth lens is R10, the following conditional expression (6) is satisfied. −5.00≦R10 / R9≦−1.50 (6)

4. an exit pupil surface of the first lens is a convex surface on a paraxial line, and an object side surface of the first lens is a convex surface on a paraxial line, The objective lens for a microscope according to claim 1, characterized in that, when the central radius of curvature of the exit pupil surface of the first lens is R1, the central radius of curvature of the object side surface of the first lens is R2, and the axial thickness of the first lens is d1, the objective lens for a microscope satisfies the following conditional expressions (7) to (9). 0.08≦f1 / f≦0.29 (7) -0.44≦(R1+R2) / (R1-R2)≦-0.13 (8) 0.02≦d1 / TTL≦0.11 (9)

5. an exit pupil surface of the second lens is a paraxial concave surface, and an object side surface of the second lens is a paraxial convex surface, The objective lens for a microscope according to claim 1, characterized in that, when the axial thickness of the second lens is d3, the central radius of curvature of the exit pupil surface of the second lens is R3, the central radius of curvature of the object side surface of the second lens is R4, and the axial thickness of the second lens is d3, the objective lens for a microscope satisfies the following conditional expressions (10) to (12). −0.74≦f2 / f≦−0.22 (10) -3.86≦(R3+R4) / (R3-R4)≦-0.71 (11) 0.01≦d3 / TTL≦0.12 (12)

6. an exit pupil surface of the third lens is a paraxial concave surface, and an object side surface of the third lens is a paraxial convex surface, The objective lens for a microscope according to claim 1, characterized in that, when the central radius of curvature of the exit pupil 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 axial thickness of the third lens is d5, the objective lens for a microscope satisfies the following conditional expressions (13) to (14). 1.25≦(R5+R6) / (R5-R6)≦20.05 (13) 0.00≦d5 / TTL≦0.02 (14)

7. The objective lens for a microscope according to claim 1, characterized in that, when the focal length of the fourth lens is f4, the central radius of curvature of the exit pupil 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, the following conditional expressions (15) to (17) are satisfied. −0.37≦f4 / f≦−0.09 (15) -6.00≦(R7+R8) / (R7-R8)≦-0.65 (16) 0.01≦d7 / TTL≦0.12 (17)

8. the fifth lens has an exit pupil surface that is convex on the paraxial direction, and an object side surface of the fifth lens has a convex surface on the paraxial direction, 2. The microscope objective lens according to claim 1, characterized in that, when the focal length of the fifth lens is f5 and the axial thickness of the fifth lens is d9, the following conditional expressions (18) to (19) are satisfied. 0.21≦f5 / f≦1.09 (18) 0.01≦d9 / TTL≦0.12 (19)

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

Images