Immersion microscope objectives

Abstract

To provide a liquid immersion microscope objective lens that exerts sufficient performance even when using various solutions such as an immersion liquid, transparentization solution and the like.SOLUTION: A liquid immersion microscope objective lens with a magnification equal to or less than 35 times comprises from an object side: a first lens group that includes a meniscus lens; a second lens group that includes a cemented lens and has negative refractive power converting a diffusion light-ray flux to a convergence light-ray flux; and a third lens group that has negative refractive power. The third lens group is composed of, from the object side, a front group that has a concave surface with negative refractive power on the most image side, and a rear group that has a concave surface with negative refractive power on the most object side. An objective lens is such that the amount of chromatic aberration at the e-line as a reference even when using any of a plurality of immersion liquids, the chromatic aberration at each wavelength ranging from 435.18nm to 656.13nm is smaller than the size of a focal depth of the liquid immersion microscope objective lens at the wavelength, and satisfies the following conditional expression. 0.64≤NA×WD≤3.5 (1), where NA is the numerical aperture on the object side of the objective lens, and WD is the working distance of the objective lens.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an immersion microscope objective. [Background technology]

[0002] Opportunities for observing three-dimensional specimens, such as spheroids, using microscopes are increasing. When observing three-dimensional specimens, it is difficult to observe deep within them due to scattering within the specimen. For this reason, techniques have been proposed that utilize correction collars to observe deep within three-dimensional specimens, as described in Patent Document 1, for example. Various techniques for making specimens transparent have also been developed. Advances in clearing solutions have made it possible to use immunostaining, enabling simultaneous fluorescence observation at multiple wavelengths even with cleared specimens. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-160213 Summary of the Invention [Problem to be solved by the invention]

[0004] Currently, various clearing solutions have been developed, and the substances used for clearing are also diverse. As a result, the refractive index and dispersion of each clearing solution vary. Therefore, no matter which clearing solution is used, it is not easy to simultaneously correct the spherical aberration and chromatic aberration caused by the refractive index and dispersion.

[0005] Furthermore, when an immersion microscope objective is used for observation, if the immersion liquid is difficult to maintain uniformly, such as water, which contains gaseous components or absorbs moisture, the refractive index of the immersion liquid will change over time. This influence causes spherical aberration to change over time, making it even more difficult to achieve the performance required for observation with a single immersion microscope objective and maintain that performance throughout the observation.

[0006] In view of the above circumstances, an object of one aspect of the present invention is to provide an immersion microscope objective that exhibits sufficient performance even when various solutions such as immersion liquids and clearing solutions are used. [Means for solving the problem]

[0007] An immersion microscope objective according to one aspect of the present invention is an immersion microscope objective having a magnification of 35x or less, and comprising, in order from the object side, a first lens group including a meniscus lens, a second lens group including a cemented lens and having positive refractive power for converting a diverging bundle of rays into a converging bundle of rays, and a third lens group having negative refractive power as a whole, wherein any one of the first lens group, the second lens group, and the third lens group includes only one moving group. . before The third lens group consists of, in order from the object side, a front group having a concave surface with negative refractive power closest to the image side, and a rear group having a concave surface with negative refractive power closest to the object side. The rear group has at least one air contact surface between the lens surface of the rear group closest to the object side and the lens surface closest to the image side. When any of a plurality of immersion fluids is used together with the immersion microscope objective, the amount of chromatic aberration based on the e-line at each wavelength in the range of 435.18 nm to 656.13 nm is smaller than the depth of focus of the immersion microscope objective at that wavelength, and satisfies the following conditional expression: 0.64 ≦ NA×WD ≦ 3.5 (1) 0 .003 ≦ |(TANF-TANC) / TANd| ≦ 0.020 (4) where NA is the numerical aperture of the immersion microscope objective on the object side, and WD is the working distance of the immersion microscope objective. 。TANF ​​is the ratio of the vertical direction cosine to the horizontal direction cosine of the axial marginal ray for the F-line, and is a tangent indicating the direction when it emerges from the lens surface of the moving group closest to the image. TANC is the ratio of the vertical direction cosine to the horizontal direction cosine of the axial marginal ray for the C-line, and is a tangent indicating the direction when it emerges from the lens surface of the moving group closest to the image. TANd is the ratio of the vertical direction cosine to the horizontal direction cosine of the axial marginal ray for the d-line, and is a tangent indicating the direction when it emerges from the lens surface of the moving group closest to the image. [Effects of the Invention]

[0008] According to the above aspect, it is possible to provide an immersion microscope objective that exhibits sufficient performance even when various solutions such as immersion liquids and clearing solutions are used. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of an objective lens 1 according to a first embodiment of the present invention in a first state. [Figure 2] FIG. 2 is a cross-sectional view of the objective lens 1 according to the first embodiment of the present invention in a second state. [Figure 3] FIG. 2 is a cross-sectional view of the imaging lens 10. [Figure 4] 1 is a graph showing the amount of chromatic aberration of an optical system consisting of an objective lens 1 and an imaging lens 10. [Figure 5] 1 is an aberration diagram of an optical system consisting of an objective lens 1 and an imaging lens 10 in a first state. [Figure 6] 10 is an aberration diagram of the optical system consisting of the objective lens 1 and the imaging lens 10 in a second state. [Figure 7] FIG. 2 is a cross-sectional view of an objective lens 2 according to a second embodiment of the present invention in a first state. [Figure 8] FIG. 4 is a cross-sectional view of the objective lens 2 according to the second embodiment of the present invention in a second state. [Figure 9] 1 is a graph showing the amount of chromatic aberration of an optical system consisting of an objective lens 2 and an imaging lens 10. [Figure 10]1 is an aberration diagram of an optical system consisting of an objective lens 2 and an imaging lens 10 in a first state. [Figure 11] 10 is an aberration diagram of the optical system consisting of the objective lens 2 and the imaging lens 10 in a second state. [Figure 12] FIG. 10 is a cross-sectional view of an objective lens 3 according to a third embodiment of the present invention in a first state. [Figure 13] FIG. 10 is a cross-sectional view of the objective lens 3 according to the third embodiment of the present invention in a second state. [Figure 14] 10 is a graph showing the amount of chromatic aberration of an optical system consisting of an objective lens 3 and an imaging lens 10. [Figure 15] 1 is an aberration diagram of an optical system consisting of an objective lens 3 and an imaging lens 10 in a first state. [Figure 16] 10 is an aberration diagram of the optical system consisting of the objective lens 3 and the imaging lens 10 in a second state. [Figure 17] FIG. 10 is a cross-sectional view of an objective lens 4 according to a fourth embodiment of the present invention in a first state. [Figure 18] FIG. 10 is a cross-sectional view of an objective lens 4 according to a fourth embodiment of the present invention in a second state. [Figure 19] FIG. 10 is a cross-sectional view of an objective lens 4 according to a fourth embodiment of the present invention in a third state. [Figure 20] FIG. 10 is a cross-sectional view of an objective lens 4 according to a fourth embodiment of the present invention in a fourth state. [Figure 21] 10 is a graph showing the amount of chromatic aberration of an optical system consisting of an objective lens 4 and an imaging lens 10. [Figure 22] 1 is an aberration diagram of an optical system consisting of an objective lens 4 and an imaging lens 10 in a first state. [Figure 23] 10 is an aberration diagram of the optical system consisting of the objective lens 4 and the imaging lens 10 in a second state. [Figure 24] 10 is an aberration diagram of the optical system consisting of the objective lens 4 and the imaging lens 10 in a third state. [Figure 25] 10 is an aberration diagram of the optical system consisting of the objective lens 4 and the imaging lens 10 in a fourth state. [Figure 26]FIG. 10 is a cross-sectional view of an objective lens 5 according to a fifth embodiment of the present invention in a first state. [Figure 27] FIG. 10 is a cross-sectional view of an objective lens 5 according to a fifth embodiment of the present invention in a second state. [Figure 28] 1 is a graph showing the amount of chromatic aberration of an optical system consisting of an objective lens 5 and an imaging lens 10. [Figure 29] 1 is an aberration diagram of an optical system consisting of an objective lens 5 and an imaging lens 10 in a first state. [Figure 30] 10 is an aberration diagram of the optical system consisting of the objective lens 5 and the imaging lens 10 in a second state. [Figure 31] FIG. 10 is a cross-sectional view of an objective lens 6 according to a sixth embodiment of the present invention in a first state. [Figure 32] FIG. 10 is a cross-sectional view of an objective lens 6 according to a sixth embodiment of the present invention in a second state. [Figure 33] 1 is a graph showing the amount of chromatic aberration of an optical system consisting of an objective lens 6 and an imaging lens 10. [Figure 34] 1 is an aberration diagram of an optical system consisting of an objective lens 6 and an imaging lens 10 in a first state. [Figure 35] 10 is an aberration diagram of the optical system consisting of the objective lens 6 and the imaging lens 10 in a second state. [Figure 36] FIG. 10 is a cross-sectional view of an objective lens 7 according to a seventh embodiment of the present invention in a first state. [Figure 37] FIG. 10 is a cross-sectional view of an objective lens 7 according to a seventh embodiment of the present invention in a second state. [Figure 38] 1 is a graph showing the amount of chromatic aberration of an optical system consisting of an objective lens 7 and an imaging lens 10. [Figure 39] 1 is an aberration diagram of an optical system consisting of an objective lens 7 and an imaging lens 10 in a first state. [Figure 40] 10 is an aberration diagram of the optical system consisting of the objective lens 7 and the imaging lens 10 in a second state. DETAILED DESCRIPTION OF THE INVENTION

[0010] An objective lens according to an embodiment of the present application will be described. The objective lens according to this embodiment (hereinafter simply referred to as the objective lens) is an infinity-corrected microscope objective lens used in combination with an imaging lens. This objective lens is a so-called immersion microscope objective lens, which is used when observing a specimen with an immersion liquid interposed between the specimen and the objective lens.

[0011] This objective lens has a low magnification, more specifically, a magnification of 35 or less. That is, if the focal length of this objective lens is f and the focal length of the imaging lens used in combination with this objective lens is ft, then the relationship ft / f≦35 holds.

[0012] This objective lens is also designed to provide good correction of chromatic aberration over a wide wavelength range. Specifically, it is designed so that the amount of chromatic aberration at each wavelength, based on the e-line at 546.07 nm, is smaller than the depth of focus of this objective lens at that wavelength in the wavelength range from 435.18 nm to 656.13 nm, even when various immersion liquids are used. The depth of focus (DOF) here refers to the depth of focus on the object side, i.e., the depth of field, and is expressed as DOF=n×λ / (2×NA 2 ) where n is the refractive index of the immersion liquid, λ is the wavelength, and NA is the numerical aperture on the object side of the objective lens.

[0013] There are no particular limitations on the various immersion liquids that can be used with this objective lens. In the following examples, we will explain the case where two or more immersion liquids are selected from the following five types of immersion liquids. It is desirable that this objective lens be designed so that the chromatic aberration satisfies the above conditions even when such various immersion liquids are used. Specifically, it is desirable that the objective lens be designed so that the above conditions are satisfied even if at least one of the refractive index or Abbe number of the immersion liquid differs by 5% or more. The refractive indexes Nd and Abbe numbers νd of these immersion liquids are as follows: Immersion liquid A: Nd=1.49306, νd=52.67 Immersion liquid B: Nd=1.4042, νd=52.02 Immersion liquid C: Nd=1.33276, νd=55.38 Immersion liquid D: Nd=1.37919, νd=52.40 Immersion liquid E: Nd=1.49306, νd=55.50

[0014] This objective lens is composed of, arranged in order from the object side, a first lens group, a second lens group having positive refractive power, and a third lens group having negative refractive power. The first lens group has, for example, positive refractive power.

[0015] The first lens group includes a meniscus lens. This meniscus lens is arranged in the first lens group with its concave surface facing the object side. The second lens group includes a cemented lens and converts a divergent bundle of rays from the first lens group into a convergent bundle of rays. In other words, the lens (or lens component) closest to the object that converts a divergent bundle of rays from an object point into a convergent bundle of rays is the lens (or lens component) closest to the object in the second lens group. The boundary between the first and second lens groups can be identified by the above characteristics.

[0016] The third lens group consists of a front group and a rear group, arranged in order from the object side, with their concave surfaces facing each other. That is, the third lens group consists of a front group having a concave surface with negative refractive power closest to the image side, and a rear group having a concave surface with negative refractive power closest to the object side. The front group may, for example, consist of a single lens component.

[0017] In this specification, a pencil of light refers to a bundle of light rays emitted from a single point on an object (object point). Furthermore, a lens component refers to a single lens or a cemented lens, a single lens block in which only two surfaces, the object-side surface and the image-side surface, through which light rays from an object point pass, are in contact with air (or immersion liquid).

[0018] The first and second lens groups gradually refract divergent light beams from an object point, converting them into convergent light beams and causing them to enter the third lens group. The third lens group converts the convergent light beams from the second lens group into divergent light beams at their opposite concave surfaces with strong negative refractive power, and then converts them into parallel light beams and emits them.

[0019] The first and second lens groups gradually refract divergent ray bundles from an object point and convert them into convergent ray bundles before they enter the third lens group, thereby making it possible to make the height of marginal rays within the third lens group lower than the height of marginal rays within the second lens group. This makes it possible to effectively correct Petzval sum with the third lens group, which has negative refractive power, and as a result, makes it possible to effectively correct curvature of field over a wide field of view. Furthermore, by including a cemented lens in the second lens group, which has a high ray height, it is possible to effectively correct chromatic aberration.

[0020] With the above lens configuration, this objective lens can achieve a high numerical aperture that allows observation of detailed cellular information at low magnifications of 35x or less, and a long working distance that allows observation of deep specimens.

[0021] Moreover, this objective lens is configured to satisfy the following conditional expression (1). 0.64 ≦ NA×WD ≦ 3.5 (1) Here, NA is the numerical aperture on the object side of this objective lens, and WD is the working distance of this objective lens.

[0022] Conditional formula (1) defines the numerical aperture and working distance of the objective lens. By satisfying conditional formula (1), for example, in a confocal microscope, even when using various immersion liquids with different refractive indices and Abbe numbers, it becomes possible to perform fluorescence observations with bright, high-resolution images deep into the specimen, with spherical and chromatic aberrations simultaneously corrected.

[0023] If the NA × WD exceeds the upper limit, at least one of the numerical aperture and working distance becomes too large. The larger the numerical aperture, the more difficult it becomes to correct chromatic aberration. Furthermore, the amount of chromatic aberration increases in proportion to the working distance. Therefore, if the working distance is too long, it becomes difficult to correct chromatic aberration when using various immersion fluids with different Abbe numbers. Furthermore, if the NA × WD falls below the lower limit, at least one of the numerical aperture and working distance becomes too small. A small numerical aperture results in insufficient resolution and insufficient brightness during fluorescence observation. Furthermore, if the working distance is too short, it becomes difficult to observe deep within a specimen when using a culture vessel with a thick bottom or a thick specimen.

[0024] The objective lens may be configured to satisfy the following conditional formula (1-1) instead of conditional formula (1). 0.65 ≦ NA×WD ≦ 3.1 (1-1)

[0025] The objective lens configured as described above achieves a high numerical aperture and a long working distance at low magnification, and can also correct chromatic aberration over a wide bandwidth. Therefore, even when various solutions with different refractive indices and Abbe numbers are used as immersion liquids, culture media, and clearing solutions, spherical aberration and chromatic aberration can be effectively corrected. Therefore, this objective lens can demonstrate sufficient performance even when various solutions are used.

[0026] A desirable configuration of the objective lens will be described below. This objective lens preferably has a correction collar. Various amounts of spherical aberration may be corrected by moving a movable group included in the objective lens using the correction collar. The correction collar may also be controlled by an automatic correction collar device such as that described in Patent Document 1, which may automatically correct spherical aberration and chromatic aberration for various solutions with different refractive indices and Abbe numbers.

[0027] It is desirable for an objective lens to include only one moving group in either the first, second, or third lens group. In this case, compared to when multiple moving groups are controlled in conjunction with each other, spherical aberration can be corrected with high precision even if a simpler structure is adopted for moving the moving group. It is particularly desirable for the second lens group to include a moving group. Including a moving group within the second lens group, which has a high ray height, makes it easier to correct spherical aberration.

[0028] It is desirable that the first lens group includes a cemented lens closest to the object. Furthermore, it is desirable that the first cemented lens, which is the cemented lens arranged closest to the object in the first lens group, includes, in order from the object side, a first lens and a meniscus lens, and that these are cemented together to form a cemented two-element lens.

[0029] It is desirable for the second lens group to include a plurality of cemented lenses, and it is particularly desirable for one of these to be a moving group, which allows the spacing between the cemented lenses to be changed, making it easier to simultaneously correct spherical aberration and chromatic aberration.

[0030] Furthermore, it is desirable that at least one of the multiple cemented lenses included in the second lens group be a positive-negative-positive triplet cemented lens. This makes it possible to change the lens spacing on the object side or image side of the positive-negative-positive triplet cemented lens with a strong chromatic aberration correction effect that is located in the second lens group where the light ray height is high, making it even easier to correct spherical aberration and chromatic aberration simultaneously.

[0031] The rear group of the third lens group has at least one air contact surface between the lens surface closest to the object and the lens surface closest to the image. In other words, the rear group includes two or more lens components. This reduces the correlation between coma and lateral chromatic aberration, making it easier to correct both coma and lateral chromatic aberration simultaneously.

[0032] It is also desirable that the objective lens satisfy at least one of the following conditional expressions (2) to (5). 0.25 ≦ 1 / |(iνd1-iνd2)×WD| ≦ 10 [mm -1 ] (2) -20 ≦ (νdG1-νdG2) / R1 ≦ -5 [mm -1 ] (3) 0.003 ≦ |(TANF-TANC) / TANd| ≦ 0.020 (4) 0.3 ≦ (νdZ1-νdZ2) / FZ1 ≦ 3 [mm -1 ] (5)

[0033] where iνd1 is the Abbe number of the immersion liquid with the lowest refractive index among multiple immersion liquids used with the objective lens. iνd2 is the Abbe number of the immersion liquid with the highest refractive index among multiple immersion liquids used with the objective lens. νdG1 is the Abbe number of the first lens element constituting the first cemented lens. νdG2 is the Abbe number of the meniscus lens element constituting the first cemented lens. TANF is the ratio of the vertical direction cosine to the horizontal direction cosine of the axial marginal ray for the F-line (horizontal direction cosine / vertical direction cosine), and is the tangent indicating the direction when it emerges from the lens surface closest to the image in the moving group. TANC is the ratio of the vertical direction cosine to the horizontal direction cosine of the axial marginal ray for the C-line (horizontal direction cosine / vertical direction cosine), and is the tangent indicating the direction when it emerges from the lens surface closest to the image in the moving group. TANd is the ratio of the vertical direction cosine to the horizontal direction cosine of the axial marginal ray for the d-line (horizontal direction cosine / vertical direction cosine), and is the tangent that indicates the direction when emitted from the lens surface closest to the image side in the moving group. νdZ1 is the highest Abbe number among the Abbe numbers of one or more positive lenses included in the moving group that is a cemented lens. νdZ2 is the lowest Abbe number among the Abbe numbers of one or more negative lenses included in the moving group that is a cemented lens. FZ1 is the focal length of the moving group.

[0034] Conditional formula (2) specifies the difference in Abbe number between the immersion liquid with the largest refractive index and the immersion liquid with the smallest refractive index used with the objective. The amount of spherical aberration and chromatic aberration varies depending on the immersion liquid, and the longer the working distance, the greater the amount of correction required. By satisfying conditional formula (2), the ratio between the dispersion difference between the two immersion liquids that produce the largest refractive index difference expected to be used and the working distance is optimized, resulting in sufficient correction of spherical aberration and chromatic aberration, even with objectives with high numerical apertures.

[0035] If 1 / |(iνd1-iνd2)×WD| exceeds the upper limit, the working distance will be too short, making it difficult to observe deep inside the specimen. If 1 / |(iνd1-iνd2)×WD| falls below the lower limit, the difference in dispersion between the two immersion liquids, which produces the largest refractive index difference, will be too large, or the working distance will be too long. This results in excessive chromatic aberration relative to spherical aberration, making it difficult to simultaneously correct both spherical and chromatic aberrations.

[0036] Conditional formula (3) defines the relationship between the Abbe number of the cemented lens located closest to the object in the objective lens and the cemented surface. Objective lenses with high numerical apertures and low magnifications require good aberration performance up to high image heights. By satisfying conditional formula (3), the Petzval sum can be corrected with the cemented lens closest to the object, suppressing the occurrence of field curvature, making it possible to maintain good performance up to high image heights.

[0037] When (νdG1-νdG2) / R1 exceeds its upper limit, significant chromatic aberration occurs in the cemented lens closest to the object. This makes it impossible to fully correct chromatic aberration in the lens groups following the cemented lens. In particular, when immersion fluids with different Abbe numbers are used, it becomes difficult to adequately address changes in chromatic aberration occurring in the light emitted from the cemented lens even when the lens spacing is changed using a correction collar. As a result, it becomes difficult to simultaneously correct spherical aberration and chromatic aberration. Furthermore, when (νdG1-νdG2) / R1 falls below its lower limit, it becomes impossible to correct the Petzval sum at the cemented surface of the cemented lens closest to the object, and as a result, it becomes impossible to correct field curvature. This makes it difficult to maintain good performance up to high image heights.

[0038] Conditional formula (4) defines the relationship between the emission directions of the light of each color from the moving group. By satisfying conditional formula (4), the differences in the emission directions of the light of each color are optimized, making it possible to change chromatic aberration in addition to spherical aberration by changing the lens spacing. Therefore, even when using various immersion liquids with different refractive indices and Abbe numbers, both spherical aberration and chromatic aberration can be corrected simultaneously. It is desirable that conditional formula (4) be satisfied regardless of the position of the moving group.

[0039] If |(TANF-TANC) / TANd| exceeds the upper limit, the difference in the emission direction of each color from the moving group becomes too large, resulting in over-correction of chromatic aberration relative to spherical aberration. This makes it difficult to simultaneously correct both spherical aberration and chromatic aberration. On the other hand, if |(TANF-TANC) / TANd| falls below the lower limit, the difference in the emission direction of each color from the moving group becomes too small, resulting in under-correction of chromatic aberration relative to spherical aberration. This makes it difficult to simultaneously correct both spherical aberration and chromatic aberration.

[0040] Conditional formula (5) defines the relationship between the difference in Abbe numbers within the moving group and the focal length of the moving group. By satisfying conditional formula (5), it becomes possible to change the amount of chromatic aberration correction at the cemented surface of the cemented lens, which is the moving group, within an appropriate range by changing the lens spacing. As a result, even when using various immersion liquids with different refractive indices and Abbe numbers, it is possible to simultaneously correct both spherical aberration and chromatic aberration.

[0041] If (νdZ1-νdZ2) / FZ1 exceeds the upper limit, the difference in Abbe numbers within the moving groups is too large compared to the focal lengths of the moving groups, resulting in a large amount of chromatic aberration correction at the cemented surfaces of the moving groups. This results in overcorrection of chromatic aberration relative to spherical aberration, making it difficult to simultaneously correct both spherical and chromatic aberration. Conversely, if (νdZ1-νdZ2) / FZ1 falls below the lower limit, the difference in Abbe numbers within the moving groups is too small compared to the focal lengths of the moving groups, resulting in a small amount of chromatic aberration correction at the cemented surfaces of the moving groups. This results in undercorrection of chromatic aberration relative to spherical aberration, making it difficult to simultaneously correct both spherical and chromatic aberration.

[0042] The objective lens may be configured to satisfy the following conditional formula (2-1) instead of conditional formula (2). The objective lens may be configured to satisfy the following conditional formula (3-1) instead of conditional formula (3). The objective lens may be configured to satisfy the following conditional formula (4-1) instead of conditional formula (4). The objective lens may be configured to satisfy the following conditional formula (5-1) instead of conditional formula (5). 0.3 ≦ 1 / |(iνd1-iνd2)×WD| ≦ 5 [mm -1 ] (2-1) -18 ≦ (νdG1-νdG2) / R1 ≦ -7 [mm -1 ] (3-1) 0.0035 ≦ |(TANF-TANC) / TANd| ≦ 0.019 (4-1) 0.45 ≦ (νdZ1-νdZ2) / FZ1 ≦ 2 [mm -1 ] (5-1)

[0043] Examples of the above-mentioned objective lens will now be described in detail. [Example 1] 1 and 2 are cross-sectional views of an objective lens 1 according to this embodiment. Fig. 1 and Fig. 2 show different states of the position of the moving group within the objective lens 1. In this embodiment, the state shown in Fig. 1 is referred to as a first state, and the state shown in Fig. 2 is referred to as a second state.

[0044] The objective lens 1 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The objective lens 1 is an immersion microscope objective lens.

[0045] The first lens group G1 includes, in order from the object side, a cemented lens CL1, a lens L3 which is a meniscus lens with its concave surface facing the object side, and a lens L4 which is a meniscus lens with its concave surface facing the object side. The cemented lens CL1 is a cemented two-lens lens and includes, in order from the object side, lens L1 which is a plano-convex lens with its flat surface facing the object side, and lens L2 which is a meniscus lens with its concave surface facing the object side.

[0046] The second lens group G2 converts the diverging light beam from the first lens group G1 into a converging light beam. The second lens group G2 includes, from the object side, a triplet cemented lens CL2 and a triplet cemented lens CL3. The cemented lens CL2 is a moving group and is a triplet cemented lens consisting of, from the object side, a biconvex lens L5, a biconcave lens L6, and a biconvex lens L7. The cemented lens CL3 includes, from the object side, a biconcave lens L8, a biconvex lens L9, and a meniscus lens L10 with its concave surface facing the object side.

[0047] The third lens group G3 consists of a front group FG (cemented lens CL4) and a rear group BG (cemented lens CL5, lens L15), with their concave surfaces facing each other. The third lens group G3 includes, in order from the object side, a cemented lens CL4, a cemented lens CL5, and lens L15, which is a meniscus lens with its concave surface facing the object side. The cemented lens CL4 consists, in order from the object side, of lens L11, which is a biconvex lens, and lens L12, which is a biconcave lens. The cemented lens CL5 consists, in order from the object side, of lens L13, which is a meniscus lens with its concave surface facing the object side, and lens L14, which is a meniscus lens with its concave surface facing the object side.

[0048] The various data of the objective lens 1 are as follows. Note that β is the magnification when the objective lens 1 is combined with the imaging lens 10. NA ob is the object-side numerical aperture of the objective lens 1. f, f1, f2, and f3 are the focal length of the objective lens, the focal length of the first lens group G1, the focal length of the second lens group G2, and the focal length of the third lens group G3, respectively. The reference wavelength is the d-line.

[0049] β≈30, f=6.0040mm (first state), f=6.0932mm (second state), f1=8.4228mm, f2=40.8210mm, f3=-79.2778mm, NA=1.05, WD=1.050mm (first state), WD=1.005mm (second state), iνd1=52.02, iνd2=52.67, νdG1=64.140, νdG2=40.760, R1=-1.5250mm, νdZ1=81.54, νdZ2=42.41, FZ1=22.636mm (First state) TANF=0.4134, TANC=0.4103, TANd=0.4112 (Second state) TANF=0.4285, TANC=0.4253, TANd=0.4263

[0050] The lens data of the objective lens 1 is as follows: Note that INF in the lens data represents infinity (∞). Objective lens 1 srd nd νd 1 INF 0.1700 1.52397 54.41 2 INF D2 NE2 νD2 3 INF 0.8800 1.51633 64.14 4 -1.5250 5.7678 1.88300 40.76 5 -6.0950 0.1324 6 -40.7697 2.6615 1.56907 71.30 7 -10.8388 0.1500 8 -36.5514 1.8711 1.56907 71.30 9 -14.3560 D9 10 13.0111 6.7427 1.49700 81.54 11 -16.9144 0.8000 1.63775 42.41 12 83.9412 1.9400 1.49700 81.54 13 -27.0247 D13 14 -95.7974 0.8000 1.63775 42.41 15 7.1735 6.9150 1.43875 94.66 16 -8.3854 1.0000 1.63775 42.41 17 -19.9557 0.2500 18 6.7932 5.0145 1.56907 71.30 19 -15.5037 0.5054 1.63775 42.41 20 4.6620 4.2500 21 -4.5224 0.7000 1.88300 40.76 22 -32.7935 2.9403 1.74100 52.64 23 -7.5555 2.4696 24 -12.5960 1.4890 1.85478 24.80 25 -9.1732 120.0000

[0051] Here, s represents the surface number, r represents the radius of curvature (mm), d represents the surface spacing (mm), nd represents the refractive index, and vd represents the Abbe number. The reference wavelength is the d-line (587.56 nm). These symbols are the same in the following examples. The surfaces designated by surface numbers s1 and s2 are the object-side surface of the cover glass CG and the image-side surface of the cover glass CG, respectively. The surfaces designated by surface numbers s3 and s25 are the lens surfaces of the objective lens 1 closest to the object and closest to the image, respectively. For example, the surface spacing d1 represents the distance on the optical axis from the surface designated by surface number s1 to the surface designated by surface number s2. The surface spacing d25 represents the distance on the optical axis from the surface designated by surface number s25 to the imaging lens, which is 115.4934 mm.

[0052] The surface spacings d2, d9, and d13 for the first state shown in Figure 1, where an immersion liquid with ND2 = 1.49306 and νD2 = 52.67 (immersion liquid A) was used, and the second state shown in Figure 2, where an immersion liquid with ND2 = 1.40420 and νD2 = 52.02 (immersion liquid B) was used, are shown below. Note that ND2 and νD2 are the refractive index and Abbe number values ​​of the immersion liquid. The ratio (min / max) of the refractive indexes of these immersion liquids is 0.940, and the ratio (min / max) of the Abbe numbers is 0.988. In this example, the refractive indexes of the immersion liquids differ by 5% or more. First state Second state D2 1.050 1.005 D9 0.1490 0.4277 D13 0.9183 0.6396

[0053] The objective lens 1 satisfies the following conditional expressions (1) to (5). (1) First state: NA × WD = 1.103 mm (1) Second state: NA × WD = 1.055 mm (2) First state: 1 / |(iνd1-iνd2)×WD|=1.465 mm -1 (2) Second state: 1 / |(iνd1-iνd2)×WD|=1.531 mm -1 (3)(νdG1-νdG2) / R1 =-15.331mm -1 (4) First state: |(TANF-TANC) / TANd| = 0.0075 (4) Second state: |(TANF-TANC) / TANd| = 0.0074 (5)(νdZ1-νdZ2) / FZ1=1.729mm -1

[0054] FIG. 3 is a cross-sectional view of an imaging lens 10 used in combination with objective lens 1. The imaging lens 10 is a microscope imaging lens that forms a magnified image of an object in combination with an infinity-corrected objective lens. The imaging lens 10 consists of cemented lenses CTL1 and CTL2, arranged in order from the object side. The cemented lens CTL1 consists of a biconvex lens TL1 and a biconcave lens TL2. The cemented lens CTL2 consists of a biconvex lens TL3 and a meniscus lens TL4 with its concave surface facing the object side. The focal length ft of the imaging lens 10 is 180 mm.

[0055] The lens data of the imaging lens 10 is as follows: Imaging lens 10 srd nd νd 1 214.478 5.7 1.60300 65.44 2 -52.260 3.85 1.51633 64.14 3 152.781 17.76 4 101.004 8.9 1.48749 70.23 5 -54.003 3.85 1.61340 44.27 6 -289.639

[0056] FIG. 4 is a graph showing the amount of chromatic aberration in an optical system consisting of the objective lens 1 and the imaging lens 10. FIGS. 5 and 6 are aberration diagrams of the optical system consisting of the objective lens 1 and the imaging lens 10, showing the aberration on the image plane formed by the objective lens 1 and the imaging lens 10 in a first state and a second state, respectively. FIGS. 5(a) and 6(a) are spherical aberration diagrams, FIGS. 5(b) and 6(b) are diagrams showing the amount of violation of the sine condition, FIGS. 5(c) and 6(c) are astigmatism diagrams, and FIGS. 5(d) and 6(d) are coma aberration diagrams. Note that "M" in the diagrams indicates the meridional component, and "S" indicates the sagittal component.

[0057] As shown in Fig. 4, the chromatic aberration of the objective lens 1 is contained within the depth of focus over a wide wavelength range. Moreover, as shown in Fig. 5 and Fig. 6, in this example, each aberration is well corrected.

[0058] [Example 2] 7 and 8 are cross-sectional views of the objective lens 2 according to this embodiment. Figures 7 and 8 show different states in which the moving groups are positioned within the objective lens 2. In this embodiment, the states shown in Figures 7 and 8 are referred to as a first state and a second state, respectively.

[0059] The objective lens 2 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The objective lens 2 is an immersion microscope objective lens.

[0060] The first lens group G1 includes, in order from the object side, a cemented lens CL1, a lens L3 which is a meniscus lens with its concave surface facing the object side, and a lens L4 which is a meniscus lens with its concave surface facing the object side. The cemented lens CL1 is a cemented two-lens lens and includes, in order from the object side, lens L1 which is a plano-convex lens with its flat surface facing the object side, and lens L2 which is a meniscus lens with its concave surface facing the object side.

[0061] The second lens group G2 converts the diverging light beam from the first lens group G1 into a converging light beam. The second lens group G2 includes, in order from the object side, a triplet cemented lens CL2 and a triplet cemented lens CL3. The cemented lens CL2 is a moving group and is a triplet cemented lens consisting of, arranged in order from the object side, a biconvex lens L5, a biconcave lens L6, and a biconvex lens L7. The cemented lens CL3 includes, in order from the object side, a meniscus lens L8 with its concave surface facing the image side, a biconvex lens L9, and a meniscus lens L10 with its concave surface facing the object side.

[0062] The third lens group G3 consists of a front group FG (cemented lens CL4) and a rear group BG (cemented lens CL5, lens L15), with their concave surfaces facing each other. The third lens group G3 includes, in order from the object side, a cemented lens CL4, a cemented lens CL5, and lens L15, which is a meniscus lens with its concave surface facing the object side. The cemented lens CL4 consists, in order from the object side, of lens L11, which is a biconvex lens, and lens L12, which is a biconcave lens. The cemented lens CL5 consists, in order from the object side, of lens L13, which is a meniscus lens with its concave surface facing the object side, and lens L14, which is a meniscus lens with its concave surface facing the object side.

[0063] The various data of the objective lens 2 are as follows: β≒30, f=6.0029mm (first state), f=6.1475mm (second state), f1=9.4661mm, f2=36.8352mm, f3=-81.6475mm, NA=1.00, WD=0.850mm (first state), WD=0.781mm (second state), iνd1=52.67, iνd2=55.38, νdG1=67.720, νdG2=40.760, R1=-1.5350mm, νdZ1=71.30, νdZ2=42.41, FZ1=23.402mm (First state) TANF=0.3543, TANC=0.3492, TANd=0.3507 (Second state) TANF=0.3749, TANC=0.3695, TANd=0.3711

[0064] The lens data of the objective lens 2 is as follows: Objective Lens 2 srd nd νd 1 INF 0.1700 1.52397 54.41 2 INF D2 NE2 νD2 3 INF 0.8000 1.45847 67.72 4 -1.5350 5.4941 1.88300 40.76 5 -6.5836 0.1500 6 -12.5625 2.5789 1.59240 68.30 7 -7.6530 0.1500 8 -209.1907 2.7297 1.59240 68.30 9 -15.2534 D9 10 14.0480 6.5069 1.56907 71.30 11 -21.8947 0.8000 1.63775 42.41 12 25.0690 2.0677 1.56907 71.30 13 -61.7685 D13 14 59.9028 0.8000 1.63775 42.41 15 7.2185 7.3374 1.43875 94.66 16 -8.7943 0.8000 1.63775 42.41 17 -39.7134 0.2500 18 7.1180 4.9261 1.59240 68.30 19 -12.2879 0.5537 1.63775 42.41 20 4.9117 4.1500 21 -4.9235 0.5123 1.88300 40.76 22 -57.5518 2.2653 1.43875 94.66 23 -7.6624 2.4988 24 -21.0693 2.3246 1.85025 30.05 25 -9.8175 120.0000

[0065] The surfaces indicated by surface numbers s1 and s2 are the object-side surface of the cover glass CG and the image-side surface of the cover glass CG, respectively. The surfaces indicated by surface numbers s3 and s25 are the lens surface of the objective lens 2 closest to the object and the lens surface of the objective lens 2 closest to the image, respectively.

[0066] The values ​​D2, D9, and D13 of the surface spacings d2, d9, and d13 for the first state shown in FIG. 7, where an immersion liquid with ND2 = 1.49306 and νD2 = 52.67 (immersion liquid A) was used, and the second state shown in FIG. 8, where an immersion liquid with ND2 = 1.33276 and νD2 = 55.38 (immersion liquid C) was used, are as follows. The ratio (min / max) of the refractive indexes of these immersion liquids is 0.893, and the ratio (min / max) of the Abbe numbers is 0.951. In this example, the refractive indexes of the immersion liquids differ by more than 10%, and the Abbe numbers differ by nearly 5%. First state Second state D2 0.8500 0.7805 D9 0.1628 0.6302 D13 0.6833 0.2159

[0067] The objective lens 2 satisfies the following conditional expressions (1) to (5). (1) First state: NA × WD = 0.850 mm (1) Second state: NA × WD = 0.781 mm (2) First state: 1 / |(iνd1-iνd2)×WD|=0.434 mm -1 (2) Second state: 1 / |(iνd1-iνd2)×WD|=0.473 mm -1 (3)(νdG1-νdG2) / R1 =-17.564mm -1 (4) First state: |(TANF-TANC) / TANd| = 0.0145 (4) Second state: |(TANF-TANC) / TANd| = 0.0144 (5)(νdZ1-νdZ2) / FZ1=1.235mm -1

[0068] Fig. 9 is a graph showing the amount of chromatic aberration of an optical system consisting of the objective lens 2 and the imaging lens 10. Figs. 10 and 11 are aberration diagrams of the optical system consisting of the objective lens 2 and the imaging lens 10, showing the aberration on the image plane formed by the objective lens 2 and the imaging lens 10 in the first and second states, respectively. Figs. 10(a) and 11(a) are spherical aberration diagrams, Figs. 10(b) and 11(b) are diagrams showing the amount of violation of the sine condition, Figs. 10(c) and 11(c) are astigmatism diagrams, and Figs. 10(d) and 11(d) are coma aberration diagrams.

[0069] As shown in Fig. 9, chromatic aberration is contained within the depth of focus over a wide wavelength range in the objective lens 2. Moreover, as shown in Fig. 10 and Fig. 11, in this example, each aberration is well corrected.

[0070] [Example 3] 12 and 13 are cross-sectional views of the objective lens 3 according to this embodiment. Figures 12 and 13 show different states in which the moving groups are positioned within the objective lens 3. In this embodiment, the states shown in Figures 12 and 13 are referred to as a first state and a second state, respectively.

[0071] The objective lens 3 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The objective lens 3 is an immersion microscope objective lens.

[0072] The first lens group G1 includes, in order from the object side, a cemented lens CL1, a lens L3 which is a meniscus lens with its concave surface facing the object side, and a lens L4 which is a meniscus lens with its concave surface facing the object side. The cemented lens CL1 is a cemented two-lens lens and includes, in order from the object side, lens L1 which is a plano-convex lens with its flat surface facing the object side, and lens L2 which is a meniscus lens with its concave surface facing the object side.

[0073] The second lens group G2 converts the diverging light beam from the first lens group G1 into a converging light beam. The second lens group G2 includes, from the object side, a triplet cemented lens CL2 and a triplet cemented lens CL3. The cemented lens CL2 is a moving group and is a triplet cemented lens consisting of, from the object side, a biconvex lens L5, a biconcave lens L6, and a biconvex lens L7. The cemented lens CL3 includes, from the object side, a biconcave lens L8, a biconvex lens L9, and a meniscus lens L10 with its concave surface facing the object side.

[0074] The third lens group G3 consists of a front group FG (cemented lens CL4) and a rear group BG (cemented lens CL5, lens L15), with their concave surfaces facing each other. The third lens group G3 includes, in order from the object side, a cemented lens CL4, a cemented lens CL5, and lens L15, which is a meniscus lens with its concave surface facing the object side. The cemented lens CL4 consists, in order from the object side, of lens L11, which is a biconvex lens, and lens L12, which is a biconcave lens. The cemented lens CL5 consists, in order from the object side, of lens L13, which is a meniscus lens with its concave surface facing the object side, and lens L14, which is a meniscus lens with its concave surface facing the object side.

[0075] The various data of the objective lens 3 are as follows: β≈30, f=6.0032mm (first state), f=6.0944mm (second state), f1=9.4502mm, f2=34.1154mm, f3=-61.4204mm, NA=1.10, WD=1.050mm (first state), WD=1.006mm (second state), iνd1=52.02, iνd2=52.67, νdG1=67.720, νdG2=40.760, R1=-1.5450mm, νdZ1=71.30, νdZ2=42.41, FZ1=21.333mm (First state) TANF=0.4977, TANC=0.4947, TANd=0.4956 (Second state) TANF=0.5164, TANC=0.5134, TANd=0.5143

[0076] The lens data of the objective lens 3 is as follows: Objective Lens 3 srd nd νd 1 INF 0.1700 1.52397 54.41 2 INF D2 NE2 νD2 3 INF 0.9200 1.45847 67.72 4 -1.5450 5.1290 1.88300 40.76 5 -6.0278 0.1500 6 -15.4024 2.5652 1.56907 71.30 7 -8.1461 0.1500 8 -62.2824 2.7055 1.56907 71.30 9 -13.9511 D9 10 14.5760 6.6491 1.56907 71.30 11 -18.0428 0.8000 1.63775 42.41 12 53.7477 2.3414 1.56907 71.30 13 -36.1182 D13 14 -402.5974 0.8000 1.63775 42.41 15 7.5997 6.5942 1.43875 94.66 16 -8.7656 0.8000 1.63775 42.41 17 -24.0319 0.2500 18 6.9910 5.0586 1.56907 71.30 19 -14.9105 0.6695 1.63775 42.41 20 4.7526 4.1500 21 -4.8267 0.5118 1.88300 40.76 22 -52.9845 2.1486 1.43875 94.66 23 -7.4312 2.4866 24 -17.8978 2.5000 1.85025 30.05 25 -9.3407 120.0000

[0077] The surfaces indicated by surface numbers s1 and s2 are the object-side surface of the cover glass CG and the image-side surface of the cover glass CG, respectively. The surfaces indicated by surface numbers s3 and s25 are the lens surface of the objective lens 3 closest to the object and the lens surface of the objective lens 3 closest to the image, respectively.

[0078] The values ​​D2, D9, and D13 of the surface spacings d2, d9, and d13 for the first state shown in FIG. 12, in which an immersion liquid with ND2=1.49306 and νD2=52.67 (immersion liquid A) was used, and the second state shown in FIG. 13, in which an immersion liquid with ND2=1.40420 and νD2=52.02 (immersion liquid B) was used, are as follows. The ratio (min / max) of the refractive indexes of these immersion liquids is 0.940, and the ratio (min / max) of the Abbe numbers is 0.988. In this example, the refractive indexes of the immersion liquids differ by 5% or more. First state Second state D2 1.0500 1.0059 D9 0.1497 0.4142 D13 0.8126 0.5481

[0079] The objective lens 3 satisfies the following conditional expressions (1) to (5). (1) First state: NA × WD = 1.155 mm (1) Second state: NA × WD = 1.106 mm (2) First state: 1 / |(iνd1-iνd2)×WD|=1.465 mm -1 (2) Second state: 1 / |(iνd1-iνd2)×WD|=1.529 mm -1 (3)(νdG1-νdG2) / R1 =-17.450mm -1 (4) First state: |(TANF-TANC) / TANd| = 0.0061 (4) Second state: |(TANF-TANC) / TANd| = 0.0057 (5)(νdZ1-νdZ2) / FZ1=1.354mm -1

[0080] Fig. 14 is a graph showing the amount of chromatic aberration of an optical system consisting of the objective lens 3 and the imaging lens 10. Figs. 15 and 16 are aberration diagrams of the optical system consisting of the objective lens 3 and the imaging lens 10, showing the aberration on the image plane formed by the objective lens 3 and the imaging lens 10 in the first and second states, respectively. Figs. 15(a) and 16(a) are spherical aberration diagrams, Figs. 15(b) and 16(b) are diagrams showing the amount of violation of the sine condition, Figs. 15(c) and 16(c) are astigmatism diagrams, and Figs. 15(d) and 16(d) are coma aberration diagrams.

[0081] As shown in Fig. 14, chromatic aberration is contained within the depth of focus over a wide wavelength range in the objective lens 3. Moreover, as shown in Figs. 15 and 16, in this example, each aberration is well corrected.

[0082] [Example 4] 17 to 20 are cross-sectional views of the objective lens 4 according to this example. Figures 17 to 20 show states in which the positions of the moving groups within the objective lens 4 are different from one another. In this example, the states shown in Figures 17, 18, 19, and 20 are referred to as the first state, second state, third state, and fourth state, respectively.

[0083] The objective lens 4 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The objective lens 4 is an immersion microscope objective lens.

[0084] The first lens group G1 includes, in order from the object side, a cemented lens CL1 and a lens L3 which is a meniscus lens with its concave surface facing the object side. The cemented lens CL1 is a cemented doublet lens and includes, in order from the object side, lens L1 which is a plano-convex lens with its flat surface facing the object side and lens L2 which is a meniscus lens with its concave surface facing the object side.

[0085] The second lens group G2 converts the diverging light beam from the first lens group G1 into a converging light beam. The second lens group G2 includes, in order from the object side, lens L4, which is a biconvex lens, cemented lens CL2, which is a triplet cemented lens, and cemented lens CL3, which is a doublet cemented lens. The cemented lens CL2 is a positive-negative-positive triplet cemented lens and consists, arranged in order from the object side, of lens L5, which is a biconvex lens, lens L6, which is a biconcave lens, and lens L7, which is a biconvex lens. The cemented lens CL3 is a moving group and consists, arranged in order from the object side, of lens L8, which is a meniscus lens with its concave surface facing the image side, and lens L9, which is a biconvex lens.

[0086] The third lens group G3 consists of a front group FG (cemented lens CL4) and a rear group BG (cemented lens CL5, lens L14), with their concave surfaces facing each other. The third lens group G3 includes, in order from the object side, a cemented lens CL4, a cemented lens CL5, and lens L14, which is a meniscus lens with its concave surface facing the object side. The cemented lens CL4 consists, in order from the object side, of lens L10, which is a meniscus lens with its concave surface facing the image side, and lens L11, which is a meniscus lens with its concave surface facing the image side. The cemented lens CL5 consists, in order from the object side, of lens L12, which is a biconcave lens, and lens L13, which is a biconvex lens.

[0087] The various data of the objective lens 4 are as follows: β≈30, f=6.0079mm (first state), f=6.0028mm (second state), f=5.9993 (third state), f=5.9780mm (fourth state), f1=11.9111mm, f2=17.7457mm, f3=-40.3094mm, NA=1.05, WD=0.797mm (first state), WD = 0.850 mm (second state), WD = 0.885 (third state), WD = 0.861 mm (fourth state), iνd1 = 52.02, iνd2 = 52.40, νdG1 = 67.720, νdG2 = 40.760, R1 = -1.5220 mm, νdZ1 = 94.66, νdZ2 = 52.64, FZ1 = 85.061 mm (First state) TANF=0.1447, TANC=0.1468, TANd=0.1462 (Second state) TANF=0.1446, TANC=0.1467, TANd=0.1462 (Third state) TANF=0.1446, TANC=0.1466, TANd=0.1461 (Fourth state) TANF=0.1447, TANC=0.1465, TANd=0.1460

[0088] The lens data of the objective lens 4 is as follows: Objective Lens 4 srd nd νd 1 INF D1 1.52397 54.41 2 INF D2 NE2 νD2 3 INF 0.9000 1.45847 67.72 4 -1.5220 4.3202 1.88300 40.76 5 -4.9146 0.2000 6 -25.1275 2.9440 1.56907 71.30 7 -9.0618 0.2000 8 31.1362 4.1640 1.56907 71.30 9 -18.3264 0.1500 10 29.7812 5.1322 1.43875 94.66 11 -12.4198 0.7000 1.63775 42.41 12 14.1866 5.0382 1.43875 94.66 13 -16.9637 D13 14 30.2478 0.7000 1.74100 52.64 15 8.3880 5.4520 1.43875 94.66 16 -19.7504 D16 17 6.5227 4.8207 1.56907 71.30 18 64.4447 0.7114 1.88300 40.76 19 4.8201 4.2500 20 -4.7776 0.7000 1.63775 42.41 21 44.1838 2.9892 1.43875 94.66 22 -12.7548 0.3489 23 -19.9219 3.4291 1.73800 32.33 24 -8.7182 120.0000

[0089] The surfaces indicated by surface numbers s1 and s2 are the object-side surface of the cover glass CG and the image-side surface of the cover glass CG, respectively. The surfaces indicated by surface numbers s3 and s24 are the lens surface of the objective lens 4 closest to the object and the lens surface closest to the image, respectively.

[0090] The surface spacings d1, d2, d13, and d16 for the first, second, and third states shown in Figures 17 to 19, in which an immersion liquid (immersion liquid B) with ND2 = 1.40420 and νD2 = 52.02 was used with cover glasses of different thicknesses, and the surface spacings d1, d2, d13, and d16 for the fourth state shown in Figure 20, in which an immersion liquid (immersion liquid D) with ND2 = 1.37919 and νD2 = 52.40 was used, are as follows: Note that the surface spacing d1 is the thickness of the cover glass. The ratio (min / max) of the refractive indices of these immersion liquids is 0.982, and the ratio (min / max) of the Abbe numbers is 0.993. In this example, the refractive indices of the immersion liquids differ by nearly 2%. First state Second state Third state Fourth state D1 0.2300 0.1700 0.1300 0.1300 D2 0.7968 0.8500 0.8854 0.8610 D13 1.0518 0.9541 0.8867 0.4833 D16 0.3428 0.4405 0.5079 0.9112

[0091] The objective lens 4 satisfies the following conditional expressions (1) to (5). (1) First state: NA × WD = 0.837 mm (1) Second state: NA × WD = 0.893 mm (1) Third state: NA × WD = 0.930 mm (1) Fourth state: NA × WD = 0.904 mm (2) First state: 1 / |(iνd1-iνd2)×WD|=3.303 mm -1 (2) Second state: 1 / |(iνd1-iνd2)×WD|=3.096 mm -1 (2) Third state: 1 / |(iνd1-iνd2)×WD|=2.972 mm -1 (2) Fourth state: 1 / |(iνd1-iνd2)×WD|=3.056 mm -1 (3)(νdG1-νdG2) / R1 =-17.714mm -1 (4) First state: |(TANF-TANC) / TANd| = 0.0143 (4) Second state: |(TANF-TANC) / TANd| = 0.0140 (4) Third state: |(TANF-TANC) / TANd| = 0.0138 (4) Fourth state: |(TANF-TANC) / TANd| = 0.0121 (5)(νdZ1-νdZ2) / FZ1=0.494mm -1

[0092] Fig. 21 is a graph showing the amount of chromatic aberration of an optical system consisting of the objective lens 4 and the imaging lens 10. Figs. 22 to 25 are aberration diagrams of the optical system consisting of the objective lens 4 and the imaging lens 10, showing the aberration on the image plane formed by the objective lens 4 and the imaging lens 10 in the first to fourth states, respectively. Figs. 22(a), 23(a), 24(a), and 25(a) are spherical aberration diagrams, Figs. 22(b), 23(b), 24(b), and 25(b) are diagrams showing the amount of violation of the sine condition, Figs. 22(c), 23(c), 24(c), and 25(c) are astigmatism diagrams, and Figs. 22(d), 23(d), 24(d), and 25(d) are coma aberration diagrams.

[0093] As shown in Fig. 21, the chromatic aberration is contained within the depth of focus over a wide wavelength range in the objective lens 4. Moreover, as shown in Figs. 22 to 25, in this example, each aberration is well corrected.

[0094] [Example 5] 26 and 27 are cross-sectional views of the objective lens 5 according to this example. Figures 26 and 27 show different states in which the moving groups are positioned within the objective lens 5. In this example, the states shown in Figures 26 and 27 are referred to as a first state and a second state, respectively.

[0095] The objective lens 5 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The objective lens 5 is an immersion microscope objective lens.

[0096] The first lens group G1 includes, in order from the object side, a cemented lens CL1 and a lens L3 which is a meniscus lens with its concave surface facing the object side. The cemented lens CL1 is a cemented doublet lens and includes, in order from the object side, lens L1 which is a plano-convex lens with its flat surface facing the object side and lens L2 which is a meniscus lens with its concave surface facing the object side.

[0097] The second lens group G2 converts the diverging light beam from the first lens group G1 into a converging light beam. The second lens group G2 includes, in order from the object side, lens L4, which is a biconvex lens, cemented lens CL2, which is a triplet cemented lens, and cemented lens CL3, which is a doublet cemented lens. The cemented lens CL2 is a positive-negative-positive triplet cemented lens and consists, arranged in order from the object side, of lens L5, which is a biconvex lens, lens L6, which is a biconcave lens, and lens L7, which is a biconvex lens. The cemented lens CL3 is a moving group and consists, arranged in order from the object side, of lens L8, which is a meniscus lens with its concave surface facing the image side, and lens L9, which is a biconvex lens.

[0098] The third lens group G3 consists of a front group FG (cemented lens CL4) and a rear group BG (cemented lens CL5, lens L14), with their concave surfaces facing each other. The third lens group G3 includes, in order from the object side, a cemented lens CL4, a cemented lens CL5, and a meniscus lens L14 with its concave surface facing the object side. The cemented lens CL4 consists, in order from the object side, of a biconvex lens L10 and a biconcave lens L11. The cemented lens CL5 consists, in order from the object side, of a biconcave lens L12 and a biconvex lens L13.

[0099] The various data of the objective lens 5 are as follows: β≈30, f=6.0033mm (first state), f=5.9797mm (second state), f1=10.9856mm, f2=17.9133mm, f3=-42.1456mm, NA=1.00, WD=0.850mm (first state), WD=0.796mm (second state), iνd1=52.02, iνd2=55.38, νdG1=67.720, νdG2=40.760, R1=-1.5200mm, νdZ1=94.66, νdZ2=42.41, FZ1=132.759mm (First state) TANF=0.1335, TANC=0.1359, TANd=0.1353 (Second state) TANF=0.1336, TANC=0.1354, TANd=0.1350

[0100] The lens data of the objective lens 5 is as follows: Objective Lens 5 srd nd νd 1 INF 0.1700 1.52397 54.41 2 INF D2 NE2 νD2 3 INF 0.9000 1.45847 67.72 4 -1.5200 4.5127 1.88300 40.76 5 -4.9150 0.1500 6 -34.0286 2.3254 1.56907 71.30 7 -9.7099 0.1500 8 43.2968 2.5557 1.56907 71.30 9 -20.7428 0.2500. 10 48.4359 7.9845 1.56907 71.30 11 -10.6748 0.8000 1.83481 42.73 12 39.2160 3.8527 1.56907 71.30 13 -13.4694 D13 14 41.7232 0.8000 1.63775 42.41 15 7.4012 5.5485 1.43875 94.66 16 -24.0185 D16 17 6.3397 5.0585 1.43875 94.66 18 -88.5427 0.6873 1.63775 42.41 19 4.7166 4.2500 20 -4.7551 0.7000 1.63775 42.41 21 29.7899 2.7115 1.43875 94.66 22 -19.7566 0.3098 23 -27.6274 3.6172 1.73800 32.33 24 -8.6200 120.0000

[0101] The surfaces indicated by surface numbers s1 and s2 are the object-side surface of the cover glass CG and the image-side surface of the cover glass CG, respectively. The surfaces indicated by surface numbers s3 and s24 are the lens surface of the objective lens 5 closest to the object and the lens surface of the objective lens 5 closest to the image, respectively.

[0102] The values ​​D2, D13, and D16 of the surface spacings d2, d13, and d16 for the first state shown in FIG. 26, in which an immersion liquid with ND2=1.40420 and νD2=52.02 (immersion liquid B) was used, and the second state shown in FIG. 27, in which an immersion liquid with ND2=1.33276 and νD2=55.38 (immersion liquid C) was used, are as follows. The ratio (min / max) of the refractive indexes of these immersion liquids is 0.949, and the ratio (min / max) of the Abbe numbers is 0.939. In this example, the refractive index and Abbe number of the immersion liquids both differ by 5% or more. First state Second state D2 0.8500 0.7964 D13 1.0857 0.2947 D16 0.2931 1.0841

[0103] The objective lens 5 satisfies the following conditional expressions (1) to (5). (1) First state: NA × WD = 0.850 mm (1) Second state: NA × WD = 0.796 mm (2) First state: 1 / |(iνd1-iνd2)×WD|=0.350 mm -1 (2) Second state: 1 / |(iνd1-iνd2)×WD|=0.374 mm -1 (3)(νdG1-νdG2) / R1 =-17.737mm -1 (4) First state: |(TANF-TANC) / TANd| = 0.0180 (4) Second state: |(TANF-TANC) / TANd| = 0.0139 (5)(νdZ1-νdZ2) / FZ1=0.394mm -1

[0104] Fig. 28 is a graph showing the amount of chromatic aberration of an optical system consisting of the objective lens 5 and the imaging lens 10. Figs. 29 and 30 are aberration diagrams of the optical system consisting of the objective lens 5 and the imaging lens 10, showing the aberration on the image plane formed by the objective lens 5 and the imaging lens 10 in the first and second states, respectively. Figs. 29(a) and 30(a) are spherical aberration diagrams, Figs. 29(b) and 30(b) are diagrams showing the amount of violation of the sine condition, Figs. 29(c) and 30(c) are astigmatism diagrams, and Figs. 29(d) and 30(d) are coma aberration diagrams.

[0105] As shown in Fig. 28, the chromatic aberration is contained within the depth of focus over a wide wavelength range in the objective lens 5. Moreover, as shown in Fig. 29 and Fig. 30, in this example, each aberration is well corrected.

[0106] [Example 6] 31 and 32 are cross-sectional views of the objective lens 6 according to this example. Figures 31 and 32 show states in which the positions of the moving groups within the objective lens 6 are different from each other. In this example, the states shown in Figures 31 and 32 are referred to as a first state and a second state, respectively.

[0107] The objective lens 6 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The objective lens 6 is an immersion microscope objective lens.

[0108] The first lens group G1 is made up of a cemented lens CL1, which is a two-element cemented lens consisting of, arranged in order from the object side, lens L1, which is a plano-convex lens with its flat surface facing the object side, and lens L2, which is a meniscus lens with its concave surface facing the object side.

[0109] The second lens group G2 converts the diverging light beam from the first lens group G1 into a converging light beam. The second lens group G2 includes, in order from the object side, lens L3, which is a biconvex lens, cemented lens CL2, which is a triplet cemented lens, lens L7, which is a biconvex lens, and cemented lens CL3, which is a triplet cemented lens. The cemented lens CL2 is a positive-negative-positive triplet cemented lens and consists, arranged in order from the object side, of lens L4, which is a biconvex lens, lens L5, which is a biconcave lens, and lens L6, which is a biconvex lens. The cemented lens CL3 is a moving group and consists, arranged in order from the object side, of lens L8, which is a meniscus lens with its concave surface facing the image side, lens L9, which is a biconvex lens, and lens L10, which is a meniscus lens with its concave surface facing the object side.

[0110] The third lens group G3 consists of a front group FG (cemented lens CL4) and a rear group BG (cemented lens CL5, lens L15), with their concave surfaces facing each other. The third lens group G3 includes, in order from the object side, a cemented lens CL4, a cemented lens CL5, and lens L15, which is a meniscus lens with its concave surface facing the object side. The cemented lens CL4 consists, in order from the object side, of lens L11, which is a biconvex lens, and lens L12, which is a biconcave lens. The cemented lens CL5 consists, in order from the object side, of lens L13, which is a meniscus lens with its concave surface facing the object side, and lens L14, which is a meniscus lens with its concave surface facing the object side.

[0111] The various data of the objective lens 6 are as follows: β≒30, f=6.0037mm (first state), f=5.9822mm (second state), f1=16.9061mm, f2=17.4760mm, f3=-38.6087mm, NA=1.00, WD=3.050mm (first state), WD=2.854mm (second state), iνd1=52.02, iνd2=52.67, νdG1=67.720, νdG2=40.760, R1=-3.7000mm, νdZ1=94.66, νdZ2=54.68, FZ1=467.986mm (First state) TANF=0.1747, TANC=0.1761, TANd=0.1757 (Second state) TANF=0.1739, TANC=0.1746, TANd=0.1745

[0112] The lens data of the objective lens 6 is as follows: Objective Lens 6 srd nd νd 1 INF 0.1700 1.52626 54.41 2 INF D2 3 INF 1.5443 1.46007 67.72 4 -3.7000 5.1924 1.88815 40.76 5 -6.6846 0.1500 6 27.3492 6.6359 1.57098 71.30 7 -19.7403 0.1500 8 9236.1801 5.0524 1.43986 94.66 9 -12.9085 1.0000 1.64132 42.41 10 53.7229 3.4076 1.43986 94.66 11 -30.7304 0.1500 12 39.8749 3.0000 1.57098 71.30 13 -52.7232 D13 14 31.6649 1.0000 1.73234 54.68 15 12.6904 6.5041 1.43986 94.66 16 -12.5569 1.0000 1.73234 54.68 17 -29.7362 D17 18 8.5032 5.5038 1.43986 94.66 19 -25.2886 6.4884 1.64132 42.41 20 4.9763 4.2500 21 -4.3237 1.0000 1.88815 40.76 22 -23.9942 3.0751 1.43986 94.66 23 -7.2364 0.2533 24 -13.6517 2.7031 1.85694 30.05 25 -8.5047 120.0000

[0113] The surfaces indicated by surface numbers s1 and s2 are the object-side surface of the cover glass CG and the image-side surface of the cover glass CG, respectively. The surfaces indicated by surface numbers s3 and s25 are the lens surface of the objective lens 6 closest to the object and the lens surface of the objective lens 6 closest to the image, respectively.

[0114] The values ​​D2, D13, and D17 of the surface spacings d2, d13, and d17 for the first state shown in FIG. 31, in which an immersion liquid with ND2=1.49306 and νD2=52.67 (immersion liquid A) was used, and the second state shown in FIG. 32, in which an immersion liquid with ND2=1.40420 and νD2=52.02 (immersion liquid B) was used, are as follows. The ratio (min / max) of the refractive indexes of these immersion liquids is 0.940, and the ratio (min / max) of the Abbe numbers is 0.988. In this example, the refractive indexes of the immersion liquids differ by 5% or more. First state Second state D2 3.0500 2.8539 D13 3.0138 0.8812 D17 0.2683 2.4009

[0115] The objective lens 6 satisfies the following conditional expressions (1) to (4). (1) First state: NA × WD = 3.050 mm (1) Second state: NA × WD = 2.854 mm (2) First state: 1 / |(iνd1-iνd2)×WD|=0.504 mm -1 (2) Second state: 1 / |(iνd1-iνd2)×WD|=0.539 mm -1 (3)(νdG1-νdG2) / R1 =-7.286mm -1 (4) First state: |(TANF-TANC) / TANd| = 0.0079 (4) Second state: |(TANF-TANC) / TANd| = 0.0040 (5) (νdZ1-νdZ2) / FZ1=0.085mm -1

[0116] Fig. 33 is a graph showing the amount of chromatic aberration of an optical system consisting of the objective lens 6 and the imaging lens 10. Figs. 34 and 35 are aberration diagrams of the optical system consisting of the objective lens 6 and the imaging lens 10, showing the aberration on the image plane formed by the objective lens 6 and the imaging lens 10 in the first and second states, respectively. Figs. 34(a) and 35(a) are spherical aberration diagrams, Figs. 34(b) and 35(b) are diagrams showing the amount of violation of the sine condition, Figs. 34(c) and 35(c) are astigmatism diagrams, and Figs. 34(d) and 35(d) are coma aberration diagrams.

[0117] As shown in Fig. 33, chromatic aberration is contained within the depth of focus over a wide wavelength range in the objective lens 6. Moreover, as shown in Figs. 34 and 35, in this example, each aberration is well corrected.

[0118] [Example 7] 36 and 37 are cross-sectional views of the objective lens 7 according to this example. Figures 36 and 37 show different states of the moving group in the objective lens 7. In this example, the states shown in Figures 36 and 37 are referred to as a first state and a second state, respectively.

[0119] The objective lens 7 is composed of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The objective lens 7 is an immersion microscope objective lens.

[0120] The first lens group G1 includes a cemented lens CL1, a lens L3 which is a meniscus lens with its concave surface facing the object side, and a lens L4 which is a meniscus lens with its concave surface facing the object side. The cemented lens CL1 is a two-element cemented lens, and is composed of, arranged in order from the object side, lens L1 which is a plano-convex lens with its flat surface facing the object side, and lens L2 which is a meniscus lens with its concave surface facing the object side.

[0121] The second lens group G2 converts the diverging light beam from the first lens group G1 into a converging light beam. The second lens group G2 includes, in order from the object side, a cemented lens CL2 which is a moving group, and a cemented lens CL3 which is a triplet cemented lens. The cemented lens CL2 is a positive-negative-positive triplet cemented lens. Arranged in order from the object side, the cemented lens CL3 is made up of a biconvex lens L5, a biconcave lens L6, and a biconvex lens L7. Arranged in order from the object side, the cemented lens CL3 is made up of a biconcave lens L8, a biconvex lens L9, and a meniscus lens L10 with its concave surface facing the object side.

[0122] The third lens group G3 consists of a front group FG (cemented lens CL4) and a rear group BG (cemented lens CL5, lens L15), with their concave surfaces facing each other. The third lens group G3 includes, in order from the object side, a cemented lens CL4, a cemented lens CL5, and lens L15, which is a meniscus lens with its concave surface facing the object side. The cemented lens CL4 consists, in order from the object side, of lens L11, which is a biconvex lens, and lens L12, which is a biconcave lens. The cemented lens CL5 consists, in order from the object side, of lens L13, which is a meniscus lens with its concave surface facing the object side, and lens L14, which is a meniscus lens with its concave surface facing the object side.

[0123] The various data of the objective lens 7 are as follows: β≈30, f=5.6500mm (first state), f=5.7216mm (second state), f1=8.1812mm, f2=19.0924mm, f3=-23.5805mm, NA=1.03, WD=1.043mm (first state), WD=0.998mm (second state), iνd1=52.02, iνd2=55.50, νdG1=64.140, νdG2=40.760, R1=-1.5220mm, νdZ1=81.54, νdZ2=42.41, FZ1=23.666mm (First state) TANF=0.4106, TANC=0.4086, TANd=0.4092 (Second state) TANF=0.4229, TANC=0.4213, TANd=0.4217

[0124] The lens data of the objective lens 7 is as follows: Objective Lens 7 srd nd νd 1 INF 0.1700 1.52397 54.41 2 INF D2 3 INF 0.9200 1.51633 64.14 4 -1.5220 5.8724 1.88300 40.76 5 -6.2118 0.1500 6 -32.8721 2.5527 1.56907 71.30 7 -10.3408 0.1500 8 -55.7457 1.9842 1.56907 71.30 9 -15.0584 D9 10 12.3872 6.6514 1.49700 81.54 11 -20.7313 0.8000 1.63775 42.41 12 28.8979 2.0473 1.49700 81.54 13 -32.6014 D13 14 -122.6663 0.8000 1.63775 42.41 15 6.8328 6.9659 1.43875 94.66 16 -7.9309 1.0000 1.63775 42.41 17 -21.1257 0.2500 18 6.5364 5.0213 1.56907 71.30 19 -13.4525 0.5766 1.63775 42.41 20 4.3905 4.2500 21 -4.2715 0.7000 1.88300 40.76 22 -46.7342 2.7417 1.74100 52.64 23 -7.1494 2.4643 24 -11.8812 1.3602 1.85478 24.80 25 -8.5760 120.0000

[0125] The surfaces indicated by surface numbers s1 and s2 are the object-side surface of the cover glass CG and the image-side surface of the cover glass CG, respectively. The surfaces indicated by surface numbers s3 and s25 are the lens surface of the objective lens 7 closest to the object and the lens surface of the objective lens 7 closest to the image, respectively.

[0126] The values ​​D2, D9, and D13 of the surface spacings d2, d9, and d13 for the first state shown in FIG. 36, in which an immersion liquid with ND2=1.49306 and νD2=55.50 (immersion liquid E) was used, and the second state shown in FIG. 37, in which an immersion liquid with ND2=1.40420 and νD2=52.02 (immersion liquid B) was used, are as follows. The ratio (min / max) of the refractive indexes of these immersion liquids is 0.940, and the ratio (min / max) of the Abbe numbers is 0.937. In this example, the refractive index and Abbe number of the immersion liquids both differ by 5% or more. First state Second state D2 1.0428 0.9981 D9 0.7740 1.0120 D13 0.9260 0.6880

[0127] The objective lens 7 satisfies the following conditional expressions (1) to (5). (1) First state: NA × WD = 1.074 mm (1) Second state: NA × WD = 1.028 mm (2) First state: 1 / |(iνd1-iνd2)×WD|=0.276 mm -1 (2) Second state: 1 / |(iνd1-iνd2)×WD|=0.288 mm -1 (3)(νdG1-νdG2) / R1 =-15.361mm -1 (4) First state: |(TANF-TANC) / TANd| = 0.0048 (4) Second state: |(TANF-TANC) / TANd| = 0.0038 (5)(νdZ1-νdZ2) / FZ1=1.653mm -1

[0128] Fig. 38 is a graph showing the amount of chromatic aberration of an optical system consisting of the objective lens 7 and the imaging lens 10. Figs. 39 and 40 are aberration diagrams of the optical system consisting of the objective lens 7 and the imaging lens 10, showing the aberration on the image plane formed by the objective lens 7 and the imaging lens 10 in the first and second states, respectively. Figs. 39(a) and 40(a) are spherical aberration diagrams, Figs. 39(b) and 40(b) are diagrams showing the amount of violation of the sine condition, Figs. 39(c) and 40(c) are astigmatism diagrams, and Figs. 39(d) and 40(d) are coma aberration diagrams.

[0129] As shown in Fig. 38, the chromatic aberration is contained within the depth of focus over a wide wavelength range in the objective lens 7. Moreover, as shown in Fig. 39 and Fig. 40, in this example, each aberration is well corrected. [Explanation of symbols]

[0130] 1 to 7 Objective lens 10. Imaging lens G1: First lens group G2: Second lens group G3: Third lens group FG...front group BG...rear group CG ···Cover glass L1 to L15, TL1 to TL4 lenses CL1~CL5, CTL1, CTL2... cemented lenses

Claims

1. An immersion microscope objective having a magnification of 35x or less, comprising, in order from the object side: a first lens group including a meniscus lens; a second lens group including a cemented lens and having a positive refractive power for changing a diverging bundle of rays into a converging bundle of rays; a third lens group having negative refractive power, any one of the first lens group, the second lens group, and the third lens group includes only one moving group; The third lens group includes, in order from the object side, a front group having a concave surface having negative refractive power closest to the image side; a rear group having a concave surface having negative refractive power closest to the object, the rear group has at least one air contact surface between a lens surface of the rear group closest to the object side and a lens surface of the rear group closest to the image side, When any of a plurality of immersion liquids is used together with the immersion microscope objective lens, the amount of chromatic aberration based on the e-line at each wavelength in the range of 435.18 nm to 656.13 nm is smaller than the magnitude of the focal depth of the immersion microscope objective lens at that wavelength, The following conditional expression is satisfied:

1. An immersion microscope objective lens comprising: 0.64 ≦ NA×WD [mm] ≦ 3.5 (1) 0.003 ≦ | (TANF-TANC) / TANd | ≦ 0.020 (4) Here, NA is the object-side numerical aperture of the immersion microscope objective lens. WD is the working distance of the immersion microscope objective lens. TANF is the ratio of the vertical direction cosine to the horizontal direction cosine of the axial marginal ray for the F-line, and is a tangent indicating the direction when it emerges from the lens surface of the moving group closest to the image. TANC is the ratio of the vertical direction cosine to the horizontal direction cosine of the axial marginal ray for the C-line, and is a tangent indicating the direction when it emerges from the lens surface of the moving group closest to the image. TANd is the ratio of the vertical direction cosine to the horizontal direction cosine of the axial marginal ray for the d-line, and is a tangent indicating the direction when it emerges from the lens surface of the moving group closest to the image.

2. In the immersion microscope objective lens according to claim 1, the first lens group includes a first cemented lens closest to the object, The first cemented lens is From the object side, the first lens and the meniscus lens are included, a cemented two-lens structure in which the first lens and the meniscus lens are cemented together, The following conditional expression is satisfied:

1. An immersion microscope objective lens comprising: -20 ≦ (νdG1-νdG2) / R1 ≦ -5 [mm -1] (3) Here, νdG1 is the Abbe number of the first lens, νdG2 is the Abbe number of the meniscus lens, and R1 is the radius of curvature of the cemented surface between the first lens and the meniscus lens.

3. 3. The immersion microscope objective according to claim 1, the moving group is a cemented lens, The following conditional expression is satisfied:

1. An immersion microscope objective lens comprising: 0.3 ≦ (νdZ1-νdZ2) / FZ1 ≦ 3 [mm －１ ] (5) Here, νdZ1 is the highest Abbe number among the positive lenses included in the moving group, νdZ2 is the lowest Abbe number among the negative lenses included in the moving group, and FZ1 is the focal length of the moving group.

4. 4. The immersion microscope objective according to claim 3, The second lens group includes a plurality of cemented lenses.

1. An immersion microscope objective lens comprising:

5. 5. The immersion microscope objective according to claim 4, The plurality of cemented lenses include a positive-negative-positive triplet cemented lens.

1. An immersion microscope objective lens comprising:

6. 6. The immersion microscope objective according to claim 1, The following conditional expression is satisfied:

1. An immersion microscope objective lens comprising: 0.25 ≦ 1 / |(iνd1-iνd2)×WD| ≦ 10 [mm －１ ] (2) where iνd1 is the Abbe number of the immersion liquid with the lowest refractive index among the plurality of immersion liquids used with the immersion microscope objective, and iνd2 is the Abbe number of the immersion liquid with the highest refractive index among the plurality of immersion liquids used with the immersion microscope objective.

Images