microscope objective lens

Abstract

To provide an objective lens which offers a high numerical aperture and a long working distance with an appropriate magnification.SOLUTION: A microscope objective lens 1 provided herein consists of a positive first lens group G1 comprising multiple meniscus lenses with concave surfaces on the object side, a second lens group G2 comprising a first cemented lens consisting of a positive lens on the most object side and a negative lens, a third lens group G3 consisting of a positive single lens, a fourth lens group G4 comprising a first cemented meniscus lens having a concave surface on the object side, a fifth lens group G5 consisting of a second cemented meniscus lens consisting of a positive lens and a negative lens and having a concave surface on the image side, and a sixth lens group G6 comprising a third cemented meniscus lens consisting of a positive lens and a negative lens and having a concave surface of the object side, and satisfies the following conditional expression: 0<|f / f5|<0.15 ...(1), where f represents a focal length of the microscope objective lens 1 and f5 represents a focal length of the fifth lens group G5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to microscope objectives. [Background technology]

[0002] Objective lenses used in industrial applications such as wafer inspection require a high numerical aperture (NA) to achieve high resolution. To achieve high throughput, they also require a wide field of view and a long working distance (WD) to improve transport speed while avoiding the risk of collision between the specimen and the objective lens. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3093835 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, Patent Document 1 discloses an objective lens with a magnification of 20 and an NA of 0.7, but this objective lens has a short WD of 1 mm, which is not sufficient.

[0005] In view of the above circumstances, an object of one aspect of the present invention is to provide an objective lens that achieves a high numerical aperture and a long working distance at a moderate magnification. [Means for solving the problem]

[0006] A microscope objective according to one aspect of the present invention includes, arranged in order from an object side, a first lens group having positive refractive power and including a plurality of meniscus lenses each with a concave surface facing the object side, a second lens group including a first cemented lens closest to the object side, the first cemented lens consisting of a positive lens and a negative lens, a third lens group consisting of a positive single lens, a fourth lens group including a first cemented meniscus lens with a concave surface facing the object side, a fifth lens group including a second cemented meniscus lens with a concave surface facing the image side, the second cemented meniscus lens consisting of a positive lens and a negative lens, and a sixth lens group including a third cemented meniscus lens with a concave surface facing the object side, the third cemented meniscus lens consisting of a positive lens and a negative lens. The microscope objective satisfies the following conditional expression: 0<|f / f5|<0.15 (1) where f is the focal length of the microscope objective lens, and f5 is the focal length of the fifth lens group. [Effects of the Invention]

[0007] According to the above aspect, it is possible to provide an objective lens that achieves a high numerical aperture and a long working distance at a moderate magnification. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a microscope objective lens 1 according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the imaging lens 10. [Figure 3] 1 is an aberration diagram of an optical system consisting of a microscope objective lens 1 and an imaging lens 10. FIG. [Figure 4] FIG. 2 is a cross-sectional view of a microscope objective lens 2 according to a second embodiment of the present invention. [Figure 5] 2 is an aberration diagram of an optical system consisting of a microscope objective lens 2 and an imaging lens 10. FIG. [Figure 6] FIG. 10 is a cross-sectional view of a microscope objective lens 3 according to a third embodiment of the present invention. [Figure 7]2 is an aberration diagram of an optical system consisting of a microscope objective lens 3 and an imaging lens 10. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] A microscope objective lens according to an embodiment of the present application will be described. The microscope objective lens according to this embodiment (hereinafter simply referred to as the microscope objective lens) is an infinity-corrected microscope objective lens used in combination with an imaging lens.

[0010] A microscope objective lens is composed of a first to a sixth lens group, arranged in order from the object side. The first lens group includes multiple meniscus lenses with positive refractive power and a concave surface facing the object side. The second lens group includes a cemented lens (hereinafter referred to as the first cemented lens) consisting of a positive lens and a negative lens closest to the object side. The third lens group includes a positive single lens. The fourth lens group includes a cemented meniscus lens (hereinafter referred to as the first cemented meniscus lens) having a meniscus shape as a whole with its concave surface facing the object side. The fifth lens group includes a cemented meniscus lens (hereinafter referred to as the second cemented meniscus lens) having a meniscus shape as a whole with its concave surface facing the image side. The sixth lens group includes a cemented meniscus lens (hereinafter referred to as the third cemented meniscus lens) having a meniscus shape as a whole with its concave surface facing the object side. The second and third cemented meniscus lenses each include a positive lens and a negative lens.

[0011] Light from an object point enters the first to third lens groups as divergent light, which is then converted by the third lens group into convergent light and then incident on the fourth lens group. The fourth to sixth lens groups convert the convergent light from the third lens group into parallel light. By first converting the divergent light from the object point into convergent light and then incident on the fourth lens group, the height of marginal rays from the fourth lens group onwards can be made lower than the height of marginal rays within the first lens group. This makes it possible to effectively correct Petzval sum in the fifth and sixth lens groups, which form a Gaussian group, and as a result, it is possible to effectively correct field curvature over a wide field of view.

[0012] Furthermore, chromatic aberration can be corrected by arranging cemented lenses (first cemented lens, first cemented meniscus lens) in the peripheral region (second lens group, fourth lens group) of the third lens group, where the light ray height is the highest. In particular, by configuring these cemented lenses as achromatic lenses consisting of a low-dispersion positive lens and a high-dispersion negative lens, favorable chromatic aberration correction is possible.

[0013] Moreover, the microscope objective lens is configured to satisfy the following conditional expression (1). 0<|f / f5|<0.15 (1) where f is the focal length of the microscope objective lens, and f5 is the focal length of the fifth lens group.

[0014] Conditional expression (1) defines the power of the fifth lens group, and is intended primarily to effectively correct coma. If |f / f5| exceeds its upper limit (0.15), the power of the fifth lens group becomes too strong for the focal length. As a result, large coma occurs, and the symmetry of the coma becomes poor.

[0015] The microscope objective lens configured as described above can achieve a high numerical aperture and a long working distance at a moderate magnification.

[0016] The objective lens may be configured to satisfy the following conditional expression (1-1) instead of conditional expression (1). -0.15 <f / f5<0 ···(1-1) Conditional expression (1-1) further defines the power of the fifth lens group in conditional expression (1), and is a conditional expression for effectively correcting also the slight coma that occurs in the imaging lens 10.

[0017] A desirable configuration of the microscope objective lens will now be described. The first lens group desirably consists of a first meniscus lens with a concave surface facing the object side, and a second meniscus lens with a concave surface facing the object side. By configuring the first lens group with only two meniscus lenses with concave surfaces facing the object side, it is possible to reduce the occurrence of spherical aberration while converging light rays.

[0018] The second lens group desirably consists of the first cemented lens. By configuring the second lens group only with the first cemented lens, it is possible to correct chromatic aberration occurring in the first lens group while converging light rays.

[0019] The fourth lens group is preferably made up of a first cemented meniscus lens. By making the fourth lens group consist of only the first cemented meniscus lens, it is possible to reduce chromatic aberration and the occurrence of high-order spherical aberration.

[0020] It is desirable that the sixth lens group be made up of a third cemented meniscus lens. By constructing the sixth lens group solely from a third cemented meniscus lens, Petzval sum can be effectively corrected while lateral chromatic aberration can be satisfactorily corrected.

[0021] Furthermore, it is desirable that the microscope objective lens satisfy at least one of the following conditional expressions (2) to (4). 0.5 <f / f1<1.0 ···(2) 3.4 <n1+n2<4.0 ···(3) 60<ν3<90 (4) where f1 is the focal length of the first lens group. n1 is the refractive index for the e-line of the meniscus lens located closest to the object among the multiple meniscus lenses included in the first lens group. n2 is the refractive index for the e-line of the meniscus lens located second closest to the object among the multiple meniscus lenses included in the first lens group. ν3 is the Abbe number of the single lens that makes up the third lens group.

[0022] Conditional expression (2) defines the power of the first lens group, and is primarily intended to effectively correct spherical aberration. If f / f1 falls below its lower limit (0.5), the power of the first lens group will be too weak, making it difficult to balance the Petzval sum. As a result, the performance of the entire optical system will deteriorate. If f / f1 exceeds its upper limit (1.0), the power of the first lens group will be too strong, causing large negative spherical aberration in the first lens group. As a result, the other lens groups will not be able to fully correct spherical aberration, making it difficult to achieve good aberration correction.

[0023] Conditional expression (3) defines the sum of the refractive indices of the two meniscus lenses in the first lens group closest to the object, and is intended primarily to minimize Petzval's sum while achieving a microscope objective with a high NA. If n1+n2 falls below its lower limit (3.4), the radius of curvature of the meniscus lenses must be reduced to increase the power of the first lens group, making it impossible to fully correct Petzval's sum in the overall optical system. If n1+n2 exceeds its upper limit (4.0), the difference in refractive power between the individual colors becomes too large, making it difficult to effectively correct axial chromatic aberration.

[0024] Conditional expression (4) defines the Abbe number of the third lens group, and is a conditional expression primarily for effectively correcting chromatic aberration. If v3 falls below the lower limit (60), axial chromatic aberration increases, making it difficult to effectively correct axial chromatic aberration. If v3 exceeds the upper limit (90), it becomes difficult to correct lateral chromatic aberration.

[0025] The microscope objective lens having the above-described configuration has a magnification of about 20 and a high NA and a long WD. More specifically, the microscope objective lens has a focal length of 8 mm or more and 10 mm or less, and a WD of 3 mm or more and 6 mm or less.

[0026] Hereinafter, examples of the microscope objective lens described above will be specifically described. [Example 1] 1 is a cross-sectional view of a microscope objective lens 1 according to this embodiment. The microscope objective lens 1 includes, arranged in order from the object side, a first lens group G1 having positive refractive power and including multiple meniscus lenses with their concave surfaces facing the object side, a second lens group G2 including a first cemented lens closest to the object side, a third lens group G3 consisting of a positive single lens, a fourth lens group G4 including a first cemented meniscus lens with its concave surface facing the object side, a fifth lens group G5 consisting of a second cemented meniscus lens with its concave surface facing the image side, and a sixth lens group G6 including a third cemented meniscus lens with its concave surface facing the object side.

[0027] The first lens group G1 is composed of, arranged in order from the object side, a lens L1 which is a meniscus lens with its concave surface facing the object side, and a lens L2 which is a meniscus lens with its concave surface facing the object side.

[0028] The second lens group G2 is made up of a first cemented lens, the cemented lens CL1. The cemented lens CL1 is a two-element cemented lens, and is made up of, arranged in order from the object side, a biconvex lens L3 and a meniscus lens L4 with its concave surface facing the object side. The lens L4 is a negative lens.

[0029] The third lens group G3 consists of a lens L5 which is a positive single lens, more specifically a biconvex lens.

[0030] The fourth lens group G4 is made up of a cemented lens CL2 that is a first cemented meniscus lens, which is made up of, in order from the object side, a biconcave lens L6 and a biconvex lens L7.

[0031] The fifth lens group G5 is made up of a cemented lens CL3 that is a second cemented meniscus lens, which is made up of, in order from the object side, a biconvex lens L8 and a biconcave lens L9.

[0032] The sixth lens group G6 is composed of a cemented lens CL4, which is a third cemented meniscus lens. The cemented lens CL4 is composed of, arranged in order from the object side, a lens L10, which is a meniscus lens with its concave surface facing the object side, and a lens L11, which is a meniscus lens with its concave surface facing the object side. Lens L10 is a negative lens, and lens L11 is a positive lens.

[0033] The various data of the microscope objective lens 1 are as follows. ob is the object-side numerical aperture of the microscope objective lens 1. WD is the working distance of the microscope objective lens 1. f2, f3, f4, and f6 are the focal lengths of the second lens group G2, the third lens group G3, the fourth lens group G4, and the sixth lens group G6, respectively. The other parameters are as described above. NA ob =0.6, WD=3.6004m, f=8.9968mm, f1=13.5880mm, f2=1789.8mm, f3=26.2961mm, f4= -104.3538mm, f5=-63.4877mm, f6=-98.2662mm, n1=1.88815, n2=1.75844, ν3=71.3

[0034] The lens data of the microscope objective lens 1 is as follows: Note that INF in the lens data indicates infinity (∞). Microscope objective lens 1 srd ne νd 1 INF 3.6004 2 -10.6173 9 1.88815 40.76 3 -12.4513 0.3 4 -534.4304 2.5576 1.75844 52.32 5 -17.5195 0.9526 6 90.9109 4.8718 1.43986 94.66 7 -11.2089 1.2 1.61664 44.49 8 -54.4275 0.7449 9 43.0506 3.2787 1.57098 71.3 10 -22.4173 0.3 11 -93.0246 1.2 1.62409 36.26 12 11.0585 4.9999 1.43986 94.66 13 -34.4567 0.2664 14 9.5094 4.971 1.62033 63.33 15 -33.7076 1.5 1.67717 38.26 16 6.3158 4.7868 17 -6.5289 1.2 1.7434 32.33 18 -282.4159 3.5697 1.81643 22.76 19 -10.2299 120

[0035] Here, s represents the surface number, r represents the radius of curvature (mm), d represents the surface spacing (mm), ne represents the refractive index for the e-line, and vd represents the Abbe number. These symbols are the same in the following examples. The surface indicated by surface number s1 is the specimen surface. The surfaces indicated by surface numbers s2 and s19 are the lens surface closest to the object and the lens surface closest to the image of the microscope objective lens 1, respectively. For example, the surface spacing d1 represents the distance on the optical axis from the surface indicated by surface number s1 to the surface indicated by surface number s2. The surface spacing d19 represents the distance (120 mm) on the optical axis from the surface indicated by surface number s19 to the imaging lens.

[0036] The microscope objective lens 1 satisfies the following conditional expressions (1) to (4). (1) |f / f5|=|-0.142|=0.142 (2) f / f1=0.66 (3)n1+n2=3.65 (4)ν3=71.3

[0037] FIG. 2 is a cross-sectional view of a tube lens 10 used in combination with a microscope objective lens 1. The tube lens 10 is a microscope tube lens that forms a magnified image of an object in combination with an infinity-corrected objective lens. The tube lens 10 is composed of cemented lenses TCL1 and TCL2, arranged in order from the object side. The cemented lens TCL1 is composed of, arranged in order from the object side, a biconvex lens TL1 and a meniscus lens TL2 with its concave surface facing the object side. The cemented lens TCL2 is composed of, arranged in order from the object side, a biconvex lens TL3 and a biconcave lens TL4. The tube lens 10 is positioned so that the distance on the optical axis from the lens surface (surface number s19) of the microscope objective lens 1 closest to the image to the lens surface (surface number s1) of the tube lens 10 closest to the object is 120 mm. The focal length of the tube lens 10 is 180 mm.

[0038] The lens data of the imaging lens 10 is as follows: Imaging lens 10 srd ne νd 1 68.7541 7.7321 1.48915 70.23 2 -37.5679 3.4742 1.81078 40.92 3 -102.8477 0.6973 4 84.3099 6.0238 1.83932 37.16 5 -50.7100 3.0298 1.64824 40.82 6 40.6619

[0039] FIG. 3 is a diagram of aberrations of an optical system consisting of a microscope objective lens 1 and an imaging lens 10, showing the aberrations at the image plane where the microscope objective lens 1 and the imaging lens 10 form an optical image. FIG. 3(a) is a diagram of spherical aberration. FIG. 3(b) is a diagram showing the amount of violation of the sine condition. FIG. 3(c) is a diagram of astigmatism. FIG. 3(d) is a diagram of coma aberration at an image height ratio of 80% (image height of 10.60 mm). Note that "M" in the diagram indicates the meridional component, and "S" indicates the sagittal component. As shown in FIG. 3, in this embodiment, aberrations are well corrected over a wide field of view.

[0040] [Example 2] 4 is a cross-sectional view of a microscope objective lens 2 according to this embodiment. The microscope objective lens 2 includes, arranged in order from the object side, a first lens group G1 having positive refractive power and including multiple meniscus lenses with their concave surfaces facing the object side, a second lens group G2 including a first cemented lens closest to the object side, a third lens group G3 including a positive single lens, a fourth lens group G4 including a first cemented meniscus lens with its concave surface facing the object side, a fifth lens group G5 including a second cemented meniscus lens with its concave surface facing the image side, and a sixth lens group G6 including a third cemented meniscus lens with its concave surface facing the object side.

[0041] The first lens group G1 is composed of, arranged in order from the object side, a lens L1 which is a meniscus lens with its concave surface facing the object side, and a lens L2 which is a meniscus lens with its concave surface facing the object side.

[0042] The second lens group G2 is made up of a first cemented lens, the cemented lens CL1. The cemented lens CL1 is a two-element cemented lens, and is made up of, arranged in order from the object side, a biconvex lens L3 and a meniscus lens L4 with its concave surface facing the object side. The lens L4 is a negative lens.

[0043] The third lens group G3 consists of a lens L5 which is a positive single lens, more specifically a biconvex lens.

[0044] The fourth lens group G4 is made up of a cemented lens CL2 that is a first cemented meniscus lens, which is made up of, in order from the object side, a biconcave lens L6 and a biconvex lens L7.

[0045] The fifth lens group G5 is made up of a cemented lens CL3 that is a second cemented meniscus lens, which is made up of, in order from the object side, a biconvex lens L8 and a biconcave lens L9.

[0046] The sixth lens group G6 is composed of a cemented lens CL4 that is a third cemented meniscus lens. The cemented lens CL4 is composed of, arranged in order from the object side, a lens L10 that is a plano-concave lens with its concave surface facing the object side, and a lens L11 that is a plano-convex lens with its convex surface facing the image side.

[0047] The various data of the microscope objective lens 2 are as follows: NA ob =0.55, WD=3.4666m, f=8.9970mm, f1=13.8127mm, f2=106.4855mm, f3=29.9445mm, f4 =-60.8870mm, f5=-65.0208mm, f6=-122.8208mm, n1=1.88815, n2=1.75844, ν3=81.54

[0048] The lens data of the microscope objective lens 2 is as follows: Microscope Objective Lens 2 srd ne νd 1 INF 3.4666 2 -11.5092 9.9104 1.88815 40.76 3 -13.0336 0.371 4 -88.3803 2.5 1.75844 52.32 5 -16.0029 0.7708 6 33.9655 5.0365 1.43986 94.66 7 -11.6881 1.5715 1.61669 44.27 8 -54.1718 1.603 9 57.8054 2.6729 1.49846 81.54 10 -19.8121 0.4311 11 -54.2778 1.502 1.62409 36.26 12 11.0436 3.8454 1.43986 94.66 13 -40.0417 0.317 14 9.2998 4.925 1.62033 63.33 15 -21.2324 1.5 1.67717 38.26 16 6.2637 4.2895 17 -6.2403 1.2064 1.7434 32.33 18 INF 3.3809 1.81643 22.76 19 -9.5936 120

[0049] The microscope objective lens 2 satisfies the following conditional expressions (1) to (4). (1) |f / f5|=|-0.138|=0.138 (2) f / f1=0.65 (3)n1+n2=3.65 (4)ν3=81.5

[0050] FIG. 5 is a diagram of aberrations of an optical system consisting of a microscope objective lens 2 and an imaging lens 10, showing the aberrations at the image plane where the microscope objective lens 2 and the imaging lens 10 form an optical image. FIG. 5(a) is a diagram of spherical aberration. FIG. 5(b) is a diagram showing the amount of violation of the sine condition. FIG. 5(c) is a diagram of astigmatism. FIG. 5(d) is a diagram of coma aberration at an image height ratio of 80% (image height of 10.60 mm). As shown in FIG. 5, in this embodiment, aberrations are well corrected over a wide field of view.

[0051] [Example 3] 6 is a cross-sectional view of a microscope objective lens 3 according to this embodiment. The microscope objective lens 3 includes, arranged in order from the object side, a first lens group G1 having positive refractive power and including multiple meniscus lenses with their concave surfaces facing the object side, a second lens group G2 including a first cemented lens closest to the object side, a third lens group G3 consisting of a positive single lens, a fourth lens group G4 including a first cemented meniscus lens with its concave surface facing the object side, a fifth lens group G5 including a second cemented meniscus lens with its concave surface facing the image side, and a sixth lens group G6 including a third cemented meniscus lens with its concave surface facing the object side.

[0052] The first lens group G1 is composed of, arranged in order from the object side, a lens L1 which is a meniscus lens with its concave surface facing the object side, and a lens L2 which is a meniscus lens with its concave surface facing the object side.

[0053] The second lens group G2 is made up of a first cemented lens, the cemented lens CL1. The cemented lens CL1 is a two-element cemented lens, and is made up of, arranged in order from the object side, a biconvex lens L3 and a meniscus lens L4 with its concave surface facing the object side. The lens L4 is a negative lens.

[0054] The third lens group G3 consists of a lens L5 which is a positive single lens, more specifically a biconvex lens.

[0055] The fourth lens group G4 is made up of a cemented lens CL2 that is a first cemented meniscus lens, which is made up of, in order from the object side, a biconcave lens L6 and a biconvex lens L7.

[0056] The fifth lens group G5 is made up of a cemented lens CL3 that is a second cemented meniscus lens, which is made up of, in order from the object side, a biconvex lens L8 and a biconcave lens L9.

[0057] The sixth lens group G6 is composed of a cemented lens CL4, which is a third cemented meniscus lens. The cemented lens CL4 is composed of, arranged in order from the object side, a lens L10, which is a meniscus lens with its concave surface facing the object side, and a lens L11, which is a meniscus lens with its concave surface facing the object side. Lens L10 is a negative lens, and lens L11 is a positive lens.

[0058] The various data of the microscope objective lens 3 are as follows: NA ob =0.65, WD=3.4661m, f=8.9970mm, f1=15.6389mm, f2=109.3313mm, f3=29.0448mm, f4 =-101.9587mm, f5=-67.4160mm, f6=-128.6295mm, n1=1.8976, n2=1.82017, ν3=71.3

[0059] The lens data of the microscope objective lens 3 is as follows: Microscope Objective Lens 3 srd ne νd 1 INF 3.4661 2 -10.2076 8.4722 1.8976 37.13 3 -12.167 0.2237 4 -59.6793 2.7935 1.82017 46.62 5 -16.7783 1.3465 6 61.0527 5.457 1.43986 94.66 7 -11.0138 1 1.64132 42.41 8 -31.8199 0.2295 9 87.9055 3.3187 1.57098 71.3 10 -20.1597 0.2007 11 -500 1 1.62409 36.26 12 10.6634 4.9398 1.43986 94.66 13 -53.6246 0.2 14 9.3665 5.4442 1.6052 65.44 15 -36.3792 1.541 1.67717 38.26 16 6.284 5.506 17 -6.3324 1.1255 1.7434 32.33 18 -40.2859 3.2353 1.81643 22.76 19 -9.4276 120

[0060] The microscope objective lens 3 satisfies the following conditional expressions (1) to (4). (1) |f / f5|=|-0.133|=0.133 (2) f / f1=0.58 (3)n1+n2=3.72 (4)ν3=71.3

[0061] FIG. 7 is a diagram of aberrations of an optical system consisting of a microscope objective lens 3 and an imaging lens 10, showing the aberrations at the image plane where the microscope objective lens 3 and the imaging lens 10 form an optical image. FIG. 7(a) is a diagram of spherical aberration. FIG. 7(b) is a diagram showing the amount of violation of the sine condition. FIG. 7(c) is a diagram of astigmatism. FIG. 7(d) is a diagram of coma aberration at an image height ratio of 80% (image height of 10.60 mm). As shown in FIG. 7, in this embodiment, aberrations are well corrected over a wide field of view. [Explanation of symbols]

[0062] 1, 2, 3...Microscope objective lens 10. Imaging lens G1: First lens group G2: Second lens group G3: Third lens group G4: Fourth lens group G5: Fifth lens group G6: 6th lens group L1 to L11, TL1 to TL4 lenses CL1~CL4, CTL1, CTL2... cemented lenses

Claims

1. A microscope objective lens, arranged in order from the object side, a first lens group having positive refractive power and including a plurality of meniscus lenses each having a concave surface facing the object side; a second lens group including a first cemented lens closest to the object, the first cemented lens being composed of a positive lens and a negative lens; a third lens group consisting of a positive single lens; a fourth lens group including a first cemented meniscus lens having a concave surface facing the object side; a fifth lens group including a second cemented meniscus lens having a concave surface facing the image side, the second cemented meniscus lens including a positive lens and a negative lens; a sixth lens group including a third cemented meniscus lens having a concave surface facing the object side, the third cemented meniscus lens being composed of a positive lens and a negative lens; A microscope objective lens characterized by satisfying the following conditional formula: 0<|f / f5|<0.15...(1) where f is the focal length of the microscope objective lens, and f5 is the focal length of the fifth lens group.

2. 2. The microscope objective lens according to claim 1, the sixth lens group is made up of the third cemented meniscus lens; A microscope objective lens characterized by:

3. 3. The microscope objective lens according to claim 1, The first lens group is a first meniscus lens having a concave surface facing the object side; a second meniscus lens having a concave surface facing the object side; A microscope objective lens characterized by:

4. 4. The microscope objective lens according to claim 1, The second lens group is made up of the first cemented lens. A microscope objective lens characterized by:

5. 5. The microscope objective lens according to claim 1, the fourth lens group is made up of the first cemented meniscus lens; A microscope objective lens characterized by:

6. 6. The microscope objective lens according to claim 1, A microscope objective lens characterized by satisfying the following conditional formula: 0.5<f / f1<1.0...(2) where f1 is the focal length of the first lens group.

7. 7. The microscope objective lens according to claim 1, A microscope objective lens characterized by satisfying the following conditional formula: 3.4<n1+n2<4.0...(3) Here, n1 is the refractive index for the e-line of the meniscus lens arranged closest to the object among the plurality of meniscus lenses included in the first lens group, and n2 is the refractive index for the e-line of the meniscus lens arranged second closest to the object among the plurality of meniscus lenses included in the first lens group.

8. 8. The microscope objective lens according to claim 1, A microscope objective lens characterized by satisfying the following conditional formula: 60<ν3<90...(4) Here, v3 is the Abbe number of the single lens that constitutes the third lens group.

Images