JP7679866B2 - Immersion microscope objective lens, immersion microscope and observation method - Google Patents

Description

The present invention relates to an immersion microscope objective lens, an immersion microscope, and an observation method.

In recent years, various objective lenses for immersion microscopes have been proposed, in which an object is observed while the space between the tip and the object is filled with immersion liquid (see, for example, Patent Document 1). Such objective lenses are required to maintain high optical performance even when different types of immersion liquid are used.

Japanese Patent Application Publication No. 8-292374

The immersion microscope objective lens according to the present invention comprises, arranged in order from the object side, a first lens group having positive refractive power and converting a light beam from an object into a convergent light beam, and a second lens group having negative refractive power and converting the convergent light beam from the first lens group into a parallel light beam, the first lens group having positive refractive power and a first cemented lens disposed closest to the object side, the first cemented lens being made up of a first positive lens having a convex surface formed on the image side, and a first meniscus lens having a concave surface facing the object side and cemented to the image side of the first positive lens, the first cemented lens being supported by a first tip portion support. a lens held by a member and arranged on the image side of the first cemented lens is held by a main body holding member, the first tip holding member and the main body holding member are configured to be detachably connected to each other, in the first lens group, the first cemented lens is configured to be replaceable with a second cemented lens having positive refractive power, the second cemented lens includes a second positive lens having a convex surface formed on the image side, and a second meniscus lens having a concave surface facing the object side and cemented to the image side of the second positive lens, and a refractive index of the second positive lens is different from a refractive index of the first positive lens.

The immersion microscope according to the present invention is equipped with the above-mentioned immersion microscope objective lens.

The observation method according to the present invention is an observation method using an immersion microscope, which is equipped with the above-mentioned immersion microscope objective lens, and one of the first cemented lens and the second cemented lens is selected and placed closest to the object side of the immersion microscope objective lens according to the refractive index of the immersion liquid.

FIG. 2 is a cross-sectional view showing the configuration of a first immersion microscope objective lens according to the first embodiment. FIG. 2 is a cross-sectional view showing the configuration of a second immersion microscope objective lens according to the first embodiment. FIG. 11 is a cross-sectional view showing the configuration of a third immersion microscope objective lens according to the first embodiment. FIG. 2 is a cross-sectional view showing the configuration of an imaging lens in the first example. 5A to 5C are diagrams showing various aberrations of the first immersion microscope objective lens according to the first example when the refractive index of the immersion liquid is 1.33. 4 is a diagram showing coma aberration of the first immersion microscope objective lens according to the first example when the refractive index of the immersion liquid is 1.33. 5A to 5C are diagrams showing various aberrations of the second immersion microscope objective lens according to the first example when the refractive index of the immersion liquid is 1.35. FIG. 11 is a diagram showing coma aberration of the second immersion microscope objective lens according to the first example when the refractive index of the immersion liquid is 1.35. 5A to 5C are diagrams showing various aberrations of the second immersion microscope objective lens according to the first example when the refractive index of the immersion liquid is 1.38. FIG. 4 is a diagram showing coma aberration of the second immersion microscope objective lens according to the first example when the refractive index of the immersion liquid is 1.38. 6A to 6C are diagrams showing various aberrations of the third immersion microscope objective lens according to the first example when the refractive index of the immersion liquid is 1.44. FIG. 11 is a diagram showing coma aberration of the third immersion microscope objective lens according to the first example when the refractive index of the immersion liquid is 1.44. FIG. 11 is a cross-sectional view showing the configuration of a first immersion microscope objective lens according to a second embodiment. FIG. 11 is a cross-sectional view showing the configuration of a second immersion microscope objective lens according to a second embodiment. FIG. 11 is a cross-sectional view showing the configuration of a third immersion microscope objective lens according to the second embodiment. FIG. 11 is a cross-sectional view showing the configuration of an imaging lens in accordance with a second example. 10A to 10C are diagrams showing various aberrations of the first immersion microscope objective lens according to the second example when the refractive index of the immersion liquid is 1.33. FIG. 11 is a diagram showing coma aberration of the first immersion microscope objective lens according to the second example when the refractive index of the immersion liquid is 1.33. 11A to 11C are diagrams showing various aberrations of the second immersion microscope objective lens according to the second example when the refractive index of the immersion liquid is 1.35. FIG. 11 is a diagram showing coma aberration of the second immersion microscope objective lens according to the second example when the refractive index of the immersion liquid is 1.35. 11A to 11C are diagrams showing various aberrations of the second immersion microscope objective lens according to the second example when the refractive index of the immersion liquid is 1.38. FIG. 11 is a diagram showing coma aberration of the second immersion microscope objective lens according to the second example when the refractive index of the immersion liquid is 1.38. 11A to 11C are diagrams showing various aberrations of the third immersion microscope objective lens according to the second example when the refractive index of the immersion liquid is 1.44. FIG. 11 is a diagram showing coma aberration of the third immersion microscope objective lens according to the second example when the refractive index of the immersion liquid is 1.44. FIG. 13 is a cross-sectional view showing the configuration of a first immersion microscope objective lens according to a third embodiment. FIG. 13 is a cross-sectional view showing the configuration of a second immersion microscope objective lens according to the third embodiment. FIG. 13 is a cross-sectional view showing the configuration of a third immersion microscope objective lens according to the third embodiment. FIG. 11 is a cross-sectional view showing the configuration of an imaging lens according to a third example. 13A to 13C are diagrams showing various aberrations of the first immersion microscope objective lens according to the third example when the refractive index of the immersion liquid is 1.33. FIG. 13 is a diagram showing coma aberration of the first immersion microscope objective lens according to the third example when the refractive index of the immersion liquid is 1.33. 13A to 13C are diagrams showing various aberrations of the second immersion microscope objective lens according to the third example when the refractive index of the immersion liquid is 1.35. FIG. 13 is a diagram showing coma aberration of the second immersion microscope objective lens according to the third example when the refractive index of the immersion liquid is 1.35. 13A to 13C are diagrams showing various aberrations of the third immersion microscope objective lens according to the third example when the refractive index of the immersion liquid is 1.38. FIG. 13 is a coma aberration diagram of the third immersion microscope objective lens according to the third example, when the refractive index of the immersion liquid is 1.38. 11 is a cross-sectional view showing a state in which a first tip side lens holding member and a body side lens holding member are joined together. FIG. 13 is a cross-sectional view showing a state in which a second tip side lens holding member and a body side lens holding member are joined together. FIG. 13 is a cross-sectional view showing a state in which a first tip side lens holding member and a body side lens holding member according to a modified example are joined together. FIG. 13 is a cross-sectional view showing a state in which a second tip side lens holding member and a body side lens holding member according to a modified example are joined together. FIG. 1 is a schematic diagram of a main part of an immersion microscope equipped with an immersion microscope objective lens. 1 is a flowchart outlining an observation method using an immersion microscope.

The following describes the immersion microscope objective lens, immersion microscope, observation method, and immersion microscope objective lens series of this embodiment with reference to the figures. In this embodiment, we describe an immersion microscope objective lens that can maintain high optical performance even when the type of immersion liquid is different.

The immersion microscope objective lens according to this embodiment is an objective lens for an immersion microscope in which an object is observed with the space between the tip and the object filled with immersion liquid. As an example of the immersion microscope objective lens OL according to this embodiment, the immersion microscope objective lens OL (1a) shown in FIG. 1 is configured to have, arranged in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power. The first lens group G1 is a lens group that collects a diverging light beam from an object Ob into a convergent light beam. The second lens group G2 is a lens group that converts the convergent light beam from the first lens group G1 into a parallel light beam. Note that in FIG. 1 and other figures, the object Ob indicates an object point on the optical axis.

The first lens group G1 has a first cemented lens CL11a (see FIG. 1) arranged closest to the object side, and a second cemented lens CL11b (see FIG. 2) arranged closest to the object side in place of the first cemented lens CL11a. Both the first cemented lens CL11a and the second cemented lens CL11b are interchangeable lenses having positive refractive power, and one of the first cemented lens CL11a and the second cemented lens CL11b is selectively arranged closest to the object side. Hereinafter, for ease of explanation, the immersion microscope objective lens in the state where the first cemented lens CL11a is arranged closest to the object side may be referred to as the first immersion microscope objective lens OL(1a), and the immersion microscope objective lens in the state where the second cemented lens CL11b is arranged closest to the object side may be referred to as the second immersion microscope objective lens OL(1b).

The first cemented lens CL11a is composed of a first positive lens L11a having a convex surface formed on the image side, and a first meniscus lens L12a cemented to the image side of the first positive lens L11a with its concave surface facing the object side. The second cemented lens CL11b is composed of a second positive lens L11b having a convex surface formed on the image side, and a second meniscus lens L12b cemented to the image side of the second positive lens L11b with its concave surface facing the object side. The refractive index of the second positive lens L11b is different from that of the first positive lens L11a. That is, the refractive index of the second positive lens L11b is higher than that of the first positive lens L11a. This allows one of the first cemented lens CL11a and the second cemented lens CL11b to be selected and placed closest to the object side of the immersion microscope objective lens OL depending on the refractive index of the immersion liquid IM, making it possible to maintain high optical performance even if the type of immersion liquid IM is different.

In the immersion microscope objective lens OL of this embodiment, the first immersion microscope objective lens OL (1a) may be the first immersion microscope objective lens OL (2a) shown in FIG. 13 or the first immersion microscope objective lens OL (3a) shown in FIG. 25. The second immersion microscope objective lens OL (1b) may be the second immersion microscope objective lens OL (2b) shown in FIG. 14 or the second immersion microscope objective lens OL (3b) shown in FIG. 26.

The immersion microscope objective lens OL of this embodiment may satisfy the following conditional expressions (1) and (2).
0.85<nL1/np1<0.95...(1)
0.85<nL2/np2<0.95...(2)
where np1 is the refractive index of the first positive lens L11a, np2 is the refractive index of the second positive lens L11b, nL1 is the refractive index of the immersion liquid IM when the first cemented lens CL11a is disposed closest to the object, and nL2 is the refractive index of the immersion liquid IM when the second cemented lens CL11b is disposed closest to the object.

Conditional formula (1) is a conditional formula that defines the relationship between the refractive index of the first positive lens L11a and the refractive index of the immersion liquid IM. Conditional formula (2) is a conditional formula that defines the relationship between the refractive index of the second positive lens L11b and the refractive index of the immersion liquid IM. By satisfying conditional formulas (1) and (2), it becomes possible to maintain high optical performance even if the type of immersion liquid IM is different.

If the corresponding value of conditional formula (1) falls outside the above range, it becomes difficult to maintain high optical performance when the first cemented lens CL11a is disposed closest to the object. Specifically, if the corresponding value of conditional formula (1) falls below the lower limit, it becomes difficult to correct axial chromatic aberration. If the corresponding value of conditional formula (1) exceeds the upper limit, it becomes difficult to correct spherical aberration. To ensure the effect of this embodiment, the lower limit of conditional formula (1) may preferably be set to 0.90.

If the corresponding value of conditional expression (2) falls outside the above range, it becomes difficult to maintain high optical performance when the second cemented lens CL11b is disposed closest to the object. Specifically, if the corresponding value of conditional expression (2) falls below the lower limit, it becomes difficult to correct axial chromatic aberration. If the corresponding value of conditional expression (2) exceeds the upper limit, it becomes difficult to correct spherical aberration. To ensure the effect of this embodiment, the lower limit of conditional expression (2) may preferably be set to 0.90.

The immersion microscope objective lens OL of this embodiment may satisfy the following conditional expressions (3) and (4).
1.33≦nL1≦1.51 ... (3)
1.33≦nL2≦1.51 ... (4)
where nL1 is the refractive index of the immersion liquid IM when the first cemented lens CL11a is disposed closest to the object side, and nL2 is the refractive index of the immersion liquid IM when the second cemented lens CL11b is disposed closest to the object side.

Conditional formula (3) is a conditional formula that defines an appropriate range for the refractive index of the immersion liquid IM when the first cemented lens CL11a is positioned closest to the object. Conditional formula (4) is a conditional formula that defines an appropriate range for the refractive index of the immersion liquid IM when the second cemented lens CL11b is positioned closest to the object. By satisfying conditional formulas (3) and (4), it becomes possible to maintain high optical performance even if the type of immersion liquid IM is different.

If the value corresponding to conditional expression (3) falls outside the above range, it becomes difficult to maintain high optical performance when the first cemented lens CL11a is positioned closest to the object. In order to ensure the effect of this embodiment, the upper limit value of conditional expression (3) may preferably be set to 1.45.

If the value of conditional expression (4) falls outside the above range, it becomes difficult to maintain high optical performance when the second cemented lens CL11b is disposed closest to the object side. In order to ensure the effects of this embodiment, the upper limit of conditional expression (4) may be preferably set to 1.45.

The immersion microscope objective lens OL of this embodiment may satisfy the following conditional expression (5).
0.80≦NA≦1.30 (5)
where NA is the numerical aperture of the immersion microscope objective lens OL.

Conditional formula (5) is a conditional formula that specifies an appropriate range for the numerical aperture of the immersion microscope objective lens OL. By satisfying conditional formula (5), it is possible to obtain brightness and optimal resolving power suitable for observation. If the corresponding value of conditional formula (5) falls outside the above range, it becomes difficult to obtain brightness and optimal resolving power suitable for observation.

In the immersion microscope objective lens OL of this embodiment, the distance between the first lens group G1 and the second lens group G2 may be changed according to the refractive index of the immersion liquid IM. By changing the air distance between the first lens group G1 and the second lens group G2, it functions as a so-called correction ring, and can correct the spherical aberration that changes according to the refractive index of the immersion liquid IM.

In the immersion microscope objective lens OL of this embodiment, the first lens group G1 may have a third cemented lens CL11c (see FIG. 3) arranged closest to the object side instead of the first cemented lens CL11a and the second cemented lens CL11b. In this case, the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c are all interchangeable lenses having positive refractive power, and one of the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c is selectively arranged closest to the object side. Hereinafter, for ease of explanation, the immersion microscope objective lens in which the third cemented lens CL11c is arranged closest to the object side may be referred to as the third immersion microscope objective lens OL(1c).

The third cemented lens CL11c is composed of a third positive lens L11c having a convex surface formed on the image side, and a third meniscus lens L12c cemented to the image side of the third positive lens L11c with its concave surface facing the object side. The refractive index of the third positive lens L11c is different from the refractive index of the first positive lens L11a and the refractive index of the second positive lens L11b. That is, the refractive index of the third positive lens L11c is higher than the refractive index of the first positive lens L11a and the refractive index of the second positive lens L11b. This allows one of the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c to be selected and placed on the most object side of the immersion microscope objective lens OL according to the refractive index of the immersion liquid IM, making it possible to maintain high optical performance even if the type of immersion liquid IM is different.

The third immersion microscope objective lens OL(1c) may be the third immersion microscope objective lens OL(2c) shown in Fig. 15, or the third immersion microscope objective lens OL(3c) shown in Fig. 27. For ease of explanation, the first immersion microscope objective lens OL(1a), the second immersion microscope objective lens OL(1b), and the third immersion microscope objective lens OL(1c) are defined, but are not limited to these. Any one of the first immersion microscope objective lens OL (1a), the second immersion microscope objective lens OL (1b), and the third immersion microscope objective lens OL (1c) may be a first immersion microscope objective lens in which the first cemented lens is arranged closest to the object, another may be a second immersion microscope objective lens in which the second cemented lens is arranged closest to the object, and the remaining one may be a third immersion microscope objective lens in which the third cemented lens is arranged closest to the object.

In the immersion microscope objective lens OL of this embodiment, when the first lens group G1 has the third cemented lens CL11c, in addition to the above-mentioned conditional expressions (1) and (2), the following conditional expression (6) may be satisfied.
0.85<nL3/np3<0.95...(6)
where np3 is the refractive index of the third positive lens L11c, and nL3 is the refractive index of the immersion liquid IM when the third cemented lens CL11c is disposed closest to the object side.

Conditional formula (6) defines the relationship between the refractive index of the third positive lens L11c and the refractive index of the immersion liquid IM. By satisfying conditional formula (6) in addition to conditional formula (1) and conditional formula (2) described above, it becomes possible to maintain high optical performance even if the type of immersion liquid IM is different.

If the corresponding value of conditional expression (6) falls outside the above range, it becomes difficult to maintain high optical performance when the third cemented lens CL11c is positioned closest to the object. Specifically, if the corresponding value of conditional expression (6) falls below the lower limit, it becomes difficult to correct axial chromatic aberration. If the corresponding value of conditional expression (6) exceeds the upper limit, it becomes difficult to correct spherical aberration. In order to ensure the effect of this embodiment, the lower limit of conditional expression (6) may preferably be set to 0.88.

In the immersion microscope objective lens OL of this embodiment, when the first lens group G1 has the third cemented lens CL11c, in addition to the above-mentioned conditional expressions (3) and (4), the following conditional expression (7) may be satisfied.
1.33≦nL3≦1.51 ... (7)
where nL3 is the refractive index of the immersion liquid IM when the third cemented lens CL11c is disposed closest to the object side.

Conditional formula (3) defines an appropriate range for the refractive index of the immersion liquid IM when the third cemented lens CL11c is positioned closest to the object. By satisfying conditional formula (7) in addition to conditional formulas (3) and (4) described above, it becomes possible to maintain high optical performance even if the type of immersion liquid IM is different.

If the corresponding value of conditional expression (7) falls outside the above range, it becomes difficult to maintain high optical performance when the third cemented lens CL11c is positioned closest to the object. To ensure the effect of this embodiment, the upper limit value of conditional expression (7) may be preferably set to 1.45, more preferably 1.38.

In addition, the magnification of the immersion microscope objective lens OL in this embodiment is preferably 10x to 40x.

In the immersion microscope objective lens OL of this embodiment, the first cemented lens CL11a is held by a first tip side lens holding member BR1a having a cap-shaped outer periphery as shown in FIG. 35. A first tip side coupling part J1a configured with a female screw is provided on the inner edge of the first tip side lens holding member BR1a. The second cemented lens CL11b is held by a second tip side lens holding member BR1b having a cap-shaped outer periphery as shown in FIG. 36. A second tip side coupling part J1b configured with a female screw is provided on the inner edge of the second tip side lens holding member BR1b.

As shown in FIG. 35, a lens (a non-interchangeable lens such as a positive meniscus lens L13) arranged closer to the image side than the first cemented lens CL11a and the second cemented lens CL11b is held by a body-side lens holding member BR2 having a cylindrical outer peripheral shape. A body-side joint J2, which is configured using a male screw and can be screwed into the first tip-side joint J1a and the second tip-side joint J1b, is provided at the tip outer edge of the body-side lens holding member BR2. A correction ring (not shown) may be rotatably provided at the barrel of the body-side lens holding member BR2. The correction ring rotates to move the second lens group G2 along the optical axis, thereby changing the distance between the first lens group G1 and the second lens group G2.

As shown in Fig. 35, the first tip side joint J1a of the first tip side lens holding member BR1a is screwed into the body side joint J2 of the body side lens holding member BR2, so that the first tip side lens holding member BR1a is joined to the tip of the body side lens holding member BR2, and the first cemented lens CL11a is arranged on the most object side of the immersion microscope objective lens OL. As shown in Fig. 36, the second tip side joint J1b of the second tip side lens holding member BR1b is screwed into the body side joint J2 of the body side lens holding member BR2, so that the second tip side lens holding member BR1b is joined to the tip of the body side lens holding member BR2, and the second cemented lens CL11b is arranged on the most object side of the immersion microscope objective lens OL. In this way, by combining one of the first tip-side lens holding member BR1a and the second tip-side lens holding member BR1b with the body-side lens holding member BR2, one of the first cemented lens CL11a and the second cemented lens CL11b is selectively positioned closest to the object side of the immersion microscope objective lens OL.

Similarly, for the third cemented lens CL11c shown in FIG. 3, a third tip-side coupling portion (not shown) provided on the third tip-side lens holding member that holds the third cemented lens CL11c can be screwed into the body-side coupling portion J2 of the body-side lens holding member BR2. Therefore, one of the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c is selectively positioned closest to the object side of the immersion microscope objective lens OL.

In the immersion microscope objective lens OL of this embodiment, as shown in FIG. 37 and FIG. 38, a first tip side coupling part J1'a configured using a permanent magnet may be provided on the inner edge part of the first tip side lens holding member BR1'a. A second tip side coupling part J1'b configured using a permanent magnet may be provided on the inner edge part of the second tip side lens holding member BR1'b. An annular body side coupling part J2' capable of adsorbing the first tip side coupling part J1'a and the second tip side coupling part J1'b may be provided on the outer edge part of the tip of the body side lens holding member BR2'. Even in this way, one of the first tip side lens holding member BR1'a and the second tip side lens holding member BR1'b can be coupled to the body side lens holding member BR'2, and one of the first cemented lens CL11a and the second cemented lens CL11b is selectively arranged on the most object side of the immersion microscope objective lens OL.

Similarly, for the third cemented lens CL11c shown in FIG. 3, a third tip-side coupling portion (not shown) formed using a permanent magnet may be provided on the inner edge of the third tip-side lens holding member (not shown). This allows one of the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c to be selectively positioned closest to the object side of the immersion microscope objective lens OL.

In the immersion microscope objective lens OL of this embodiment, although not shown, the first tip side lens holding member and the second tip side lens holding member may be formed using a resin material such as hard rubber so as to be able to fit with the tip portion of the body side lens holding member. Also, the third tip side lens holding member may be formed using a resin material such as hard rubber so as to be able to fit with the tip portion of the body side lens holding member.

The immersion microscope of this embodiment is configured with the immersion microscope objective lens OL having the above-mentioned configuration. A specific example of an immersion microscope equipped with the immersion microscope objective lens OL according to this embodiment will be described with reference to FIG. 39. This immersion microscope 100 includes a stand 101 and
The stand 101 is configured to include a stage 111 attached to a base portion 102 of the stand 101, a lens barrel 121 attached to an arm portion 103 of the stand 101, and an imaging portion 131 connected to the lens barrel 121. A sample container B that holds an observation object (not shown) (such as a biological sample) together with an immersion liquid is placed on the stage 111. A slide glass (not shown) that holds an observation object (such as a biological sample) between a cover glass (not shown) and the slide glass may be placed on the stage 111. A condenser lens 117 that constitutes a transmission illumination device 116 is attached to the underside of the stage 111. In addition to the stage 111, the above-mentioned transmission illumination device 116 and a transmission illumination light source 118 are attached to the base portion 102 of the stand 101.

The objective lens 122 is attached to a revolver 126 provided below the lens barrel 121. When a sample container B is placed on the stage 111, immersion liquid is filled between the tip of the objective lens 122 and the observation object in the sample container B. When a slide glass (not shown) is placed on the stage 111, immersion liquid is filled between the tip of the objective lens 122 and a cover glass (not shown). The immersion microscope objective lens OL according to this embodiment is used as the objective lens 122 attached below the lens barrel 121. The lens barrel 121 is provided with an imaging lens 123 and a prism 124. The imaging lens 123 provided in the lens barrel 121 is the imaging lens IL described below. The lens barrel 121 is provided with an epifluorescence device 127, an epifluorescence light source 128, an eyepiece 129, and the like. The imaging unit 131 is provided with an imaging element 132.

In such an immersion microscope 100, light from an observation object passes through the immersion liquid (and the cover glass if a slide glass is placed on the stage 111), the objective lens 122, the imaging lens 123, and the prism 124 to reach the image sensor 132. The imaging lens 123 forms an image of the observation object on the imaging surface of the image sensor 132, and the image sensor 132 captures the image of the observation object. The image of the observation object captured by the image sensor 132 is displayed on the monitor MT via the external computer PC. The external computer PC can perform various image processing on the image data of the observation object captured by the image sensor 132. With this configuration, by mounting the immersion microscope objective lens OL according to the above embodiment, a microscope capable of maintaining high optical performance even if the type of immersion liquid is different can be obtained. The immersion microscope 100 may be an upright microscope or an inverted microscope.

Next, an observation method using the immersion microscope 100 of this embodiment will be generally described with reference to FIG. 40. First, a setting step (step ST10) is performed to set various settings of the immersion microscope 100. Then, after the setting step (step ST10), an observation step (step ST20) is performed to observe an observation object using the immersion microscope 100. In the setting step (step ST10), one of the first cemented lens CL11a and the second cemented lens CL11b is selected according to the refractive index of the immersion liquid and placed closest to the object side of the immersion microscope objective lens OL. In this way, even if the type of immersion liquid is different, observation can be performed while maintaining high optical performance.

In the observation method described above, the case where the first lens group G1 has the first cemented lens CL11a and the second cemented lens CL11b has been described. Here, the case where the first lens group G1 further has a third cemented lens CL11c will be described. In this case, in the setting process (step ST10) described above, one of the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c is selected according to the refractive index of the immersion liquid and placed closest to the object side of the immersion microscope objective lens OL. Even in this case, the same effect as the above case can be obtained.

In the immersion microscope objective lens OL of this embodiment, the first lens group G1 has a first cemented lens CL11a arranged closest to the object side, and a second cemented lens CL11b arranged closest to the object side in place of the first cemented lens CL11a, but is not limited to this. For example, a first immersion microscope objective lens OL(1a) in which the first cemented lens CL11a is arranged closest to the object side, and a second immersion microscope objective lens OL(1b) in which the second cemented lens CL11b is arranged closest to the object side may be separately provided and made into a series.

The series of immersion microscope objective lenses of this embodiment will now be described. The series of immersion microscope objective lenses of this embodiment includes, for example, a first immersion microscope objective lens OL (1a) shown in FIG. 1 and a second immersion microscope objective lens OL (1b) shown in FIG. 2.

The first immersion microscope objective lens OL (1a) shown in FIG. 1 is configured to have, in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power. The first lens group G1 is a lens group that collects a divergent light beam from an object Ob into a convergent light beam. The second lens group G2 is a lens group that converts the convergent light beam from the first lens group G1 into a parallel light beam. The first lens group G1 of the first immersion microscope objective lens OL (1a) has a first cemented lens CL11a that has a positive refractive power and is disposed closest to the object side. The first cemented lens CL11a is configured to have a first positive lens L11a formed with a convex surface on the image side, and a first meniscus lens L12a cemented to the image side of the first positive lens L11a with a concave surface facing the object side.

The second immersion microscope objective lens OL (1b) shown in FIG. 2 is configured to have a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power, arranged in order from the object side, like the first immersion microscope objective lens OL (1a). The first lens group G1 of the second immersion microscope objective lens OL (1b) has a second cemented lens CL11b that has a positive refractive power and is arranged closest to the object side. The second cemented lens CL11b is configured to have a second positive lens L11b with a convex surface formed on the image side, and a second meniscus lens L12b cemented to the image side of the second positive lens L11b with its concave surface facing the object side. The refractive index of the second positive lens L11b is different from the refractive index of the first positive lens L11a. That is, the refractive index of the second positive lens L11b is higher than the refractive index of the first positive lens L11a. This allows one of the first immersion microscope objective lens OL(1a) and the second immersion microscope objective lens OL(1b) to be selected and used depending on the refractive index of the immersion liquid IM, making it possible to maintain high optical performance even if the type of immersion liquid IM is different.

In the series of immersion microscope objective lenses of this embodiment, the first immersion microscope objective lens OL (1a) may be the first immersion microscope objective lens OL (2a) shown in FIG. 13 or the first immersion microscope objective lens OL (3a) shown in FIG. 25. The second immersion microscope objective lens OL (1b) may be the second immersion microscope objective lens OL (2b) shown in FIG. 14 or the second immersion microscope objective lens OL (3b) shown in FIG. 26.

In the series of immersion microscope objective lenses of this embodiment, the above-mentioned conditional expressions (1) and (2) may be satisfied. By satisfying conditional expressions (1) and (2), it becomes possible to maintain high optical performance even if the type of immersion liquid IM is different, as in the case of the above-mentioned immersion microscope objective lens OL. In order to ensure the effect of this embodiment, the lower limit value of conditional expression (1) may preferably be set to 0.90. Also, in order to ensure the effect of this embodiment, the lower limit value of conditional expression (2) may preferably be set to 0.90.

In the series of immersion microscope objective lenses of this embodiment, the above-mentioned conditional expressions (3) and (4) may be satisfied. By satisfying conditional expressions (3) and (4), it becomes possible to maintain high optical performance even if the type of immersion liquid IM is different, as in the case of the above-mentioned immersion microscope objective lens OL. In order to ensure the effect of this embodiment, the upper limit value of conditional expression (3) may preferably be set to 1.45. In addition, in order to ensure the effect of this embodiment, the upper limit value of conditional expression (4) may preferably be set to 1.45.

In the series of immersion microscope objective lenses of this embodiment, the above-mentioned conditional expression (5) may be satisfied. By satisfying conditional expression (5), it is possible to obtain brightness suitable for observation and optimal resolving power, as in the case of the above-mentioned immersion microscope objective lens OL.

In the series of immersion microscope objective lenses of this embodiment, the distance between the first lens group G1 and the second lens group G2 may be changed depending on the refractive index of the immersion liquid IM. By changing the air distance between the first lens group G1 and the second lens group G2, it functions as a so-called correction ring, and can correct the spherical aberration that changes depending on the refractive index of the immersion liquid IM.

The series of immersion microscope objective lenses of this embodiment may include a third immersion microscope objective lens OL (1c) shown in FIG. 3. The third immersion microscope objective lens OL (1c) shown in FIG. 3 is configured to have a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power, arranged in order from the object side, like the first immersion microscope objective lens OL (1a). The first lens group G1 of the third immersion microscope objective lens OL (1c) has a third cemented lens CL11c that has a positive refractive power and is arranged closest to the object side. The third cemented lens CL11c is configured to have a third positive lens L11c with a convex surface formed on the image side, and a third meniscus lens L12c cemented to the image side of the third positive lens L11c with a concave surface facing the object side. The refractive index of the third positive lens L11c is different from the refractive index of the first positive lens L11a and the refractive index of the second positive lens L11b. That is, the refractive index of the third positive lens L11c is higher than the refractive index of the first positive lens L11a and the refractive index of the second positive lens L11b. This allows one of the first immersion microscope objective lens OL(1a), the second immersion microscope objective lens OL(1b), and the third immersion microscope objective lens OL(1c) to be selected and used according to the refractive index of the immersion liquid IM, making it possible to maintain high optical performance even if the type of immersion liquid IM is different.

When the refractive index of the immersion liquid increases, it is effective to increase the refractive index of the positive lens in the cemented lens closest to the object side of the immersion microscope objective lens in accordance with the increase in the refractive index of the immersion liquid. In addition, in order to suppress the aberration caused by increasing the refractive index of the positive lens, it is effective to change the distance between the first lens group having positive refractive power and the second lens group having negative refractive power. This tendency is also the same in the examples described later. In addition, it may be possible to further suppress the aberration by changing the cemented surface in the cemented lens closest to the object side of the immersion microscope objective lens, the radius of curvature of the lens surface of the positive lens in the cemented lens that faces the convex surface toward the image side, the thickness of the positive lens in the cemented lens, etc.

The third immersion microscope objective lens OL(1c) may be the third immersion microscope objective lens OL(2c) shown in Fig. 15, or the third immersion microscope objective lens OL(3c) shown in Fig. 27. For ease of explanation, the first immersion microscope objective lens OL(1a), the second immersion microscope objective lens OL(1b), and the third immersion microscope objective lens OL(1c) are defined, but are not limited to these. Any one of the first immersion microscope objective lens OL (1a), the second immersion microscope objective lens OL (1b), and the third immersion microscope objective lens OL (1c) may be a first immersion microscope objective lens in which the first cemented lens is arranged closest to the object, another may be a second immersion microscope objective lens in which the second cemented lens is arranged closest to the object, and the remaining one may be a third immersion microscope objective lens in which the third cemented lens is arranged closest to the object.

In the series of immersion microscope objective lenses of this embodiment, when the third immersion microscope objective lens OL (1c) is included, the above-mentioned conditional formula (6) may be satisfied in addition to the above-mentioned conditional formula (1) and conditional formula (2). By satisfying the conditional formula (6), it becomes possible to maintain high optical performance even if the type of immersion liquid IM is different, as in the case of the above-mentioned immersion microscope objective lens OL. In order to ensure the effect of this embodiment, the lower limit value of the conditional formula (6) may be preferably set to 0.88.

When the series of immersion microscope objective lenses of this embodiment includes a third immersion microscope objective lens OL (1c), the above-mentioned conditional expression (7) may be satisfied in addition to the above-mentioned conditional expressions (3) and (4). By satisfying conditional expression (7), it becomes possible to maintain high optical performance even if the type of immersion liquid IM is different, as in the case of the above-mentioned immersion microscope objective lens OL. In order to ensure the effect of this embodiment, the upper limit value of conditional expression (7) may be preferably set to 1.45, more preferably 1.38.

Furthermore, in the series of immersion microscope objective lenses of this embodiment, it is desirable that the magnifications of the first immersion microscope objective lens OL (1a), the second immersion microscope objective lens OL (1b), and the third immersion microscope objective lens OL (1c) be 10x to 40x.

Below, an immersion microscope objective lens OL according to an example of this embodiment will be described with reference to the drawings. The immersion microscope objective lens OL according to each example is an objective lens for an immersion microscope that observes an object (observation object) Ob with the space between the tip and the object Ob (or cover glass) filled with immersion liquid IM (e.g., water, silicone oil, etc.).

Figures 1 to 3 are cross-sectional views showing the configuration of the immersion microscope objective lens OL {OL (1a) to OL (1c)} according to the first embodiment. Figures 13 to 15 are cross-sectional views showing the configuration of the immersion microscope objective lens OL {OL (2a) to OL (2c)} according to the second embodiment. Figures 25 to 27 are cross-sectional views showing the configuration of the immersion microscope objective lens OL {OL (3a) to OL (3c)} according to the third embodiment. In these figures, each lens group is represented by a combination of the symbol G and a number (or alphabet), and each lens is represented by a combination of the symbol L and a number (or alphabet). In this case, in order to prevent the number and types of symbols and numbers from becoming too large and complicated, lenses, etc. are represented using a combination of symbols and numbers independently for each embodiment. Therefore, even if the same combination of symbols and numbers is used between embodiments, it does not mean that they have the same configuration.

Tables 1 to 4 show data on various elements in the first embodiment. Tables 6 to 9 show data on various elements in the second embodiment. Tables 11 to 13 show data on various elements in the third embodiment. In each embodiment, the d-line (wavelength λ=587.6 nm) is used as the object of calculation of the aberration characteristics.
), g-line (wavelength λ = 435.8 nm), C-line (wavelength λ = 656.3 nm), and F-line (wavelength λ = 486.1 nm) are selected.

In the table of [Overall Specifications], f indicates the focal length of the immersion microscope objective lens OL, NA indicates the numerical aperture, and β indicates the magnification. D0 is the working distance, which indicates the distance on the optical axis from the object Ob (excluding the thickness of the cover glass) to the lens surface of the immersion microscope objective lens OL closest to the object (the first surface described below).

In the [Lens Data] table, the surface numbers indicate the order of the lens surfaces from the object side, R is the radius of curvature corresponding to each surface number (positive values are given for lens surfaces convex to the object side), D is the lens thickness or air space on the optical axis corresponding to each surface number, nd is the refractive index for the d line (wavelength λ = 587.6 nm) of the optical material corresponding to each surface number, and νd is the d line of the optical material corresponding to each surface number.
The Abbe number based on the line is shown, respectively. The "∞" for the radius of curvature indicates a plane or an opening. The refractive index of air, nd = 1.00000, is omitted. Values that change when the refractive index of the immersion liquid changes, specifically, the refractive index and Abbe number of the positive lens in the cemented lens closest to the object, and the value of the air gap between the first lens group and the second lens group, are marked with "**".

In the following, for all specifications, the focal length f, radius of curvature R, surface spacing D, and other lengths are generally given in "mm" unless otherwise specified, but this is not limited to the optical system, as the same optical performance can be obtained even when proportionally enlarged or reduced.

The explanations in the table up to this point are common to all the examples, so we will omit any duplicate explanations below.

(First embodiment)
The first embodiment will be described with reference to FIGS. 1 to 12 and Tables 1 to 5. The immersion microscope objective lens according to the first embodiment is used in a state where an immersion liquid IM is filled between the tip and the object Ob. FIG. 1 is a cross-sectional view showing the configuration of the first immersion microscope objective lens according to the first embodiment. The first immersion microscope objective lens OL (1a) according to the first embodiment is composed of a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power, arranged in order from the object side. The first lens group G1 is a lens group that collects a diverging light beam from the object Ob into a convergent light beam. The second lens group G2 is a lens group that converts the convergent light beam from the first lens group G1 into a parallel light beam.

The first lens group G1 in the first immersion microscope objective lens OL(1a) is composed of, in order from the object side, a first cemented lens CL11a, a positive meniscus lens L13 with a concave surface facing the object side, a positive meniscus lens L14 with a concave surface facing the object side, a cemented lens CL12 formed by cementing a negative lens L15 with a biconvex shape and a positive lens L16 with a biconvex shape, a cemented lens CL13 formed by cementing a negative meniscus lens L17 with a convex surface facing the object side and a positive lens L18 with a biconvex shape, and a positive lens L19 with a biconvex shape. The first cemented lens CL11a is composed of a first positive lens L11a with a plano-convex shape facing the object side, and a first meniscus lens L12a with a concave surface facing the object side and cemented to the image side of the first positive lens L11a. Additionally, the first cemented lens CL11a has positive refractive power overall.

The second lens group G2 is composed of, arranged in order from the object side, a cemented lens CL21 formed by cementing together a negative meniscus lens L21 with its convex surface facing the object side, a biconvex positive lens L22, and a biconcave negative lens L23; a cemented lens CL22 formed by cementing together a biconvex positive lens L24 and a biconcave negative lens L25; and a cemented lens CL23 formed by cementing together a biconcave negative lens L26 and a biconvex positive lens L27.

Figure 2 is a cross-sectional view showing the configuration of the second immersion microscope objective lens according to the first embodiment. The second immersion microscope objective lens OL (1b) according to the first embodiment is configured in the same manner as the first immersion microscope objective lens OL (1a), except that a second cemented lens CL11b is arranged closest to the object side instead of the first cemented lens CL11a. The second cemented lens CL11b is composed of a second positive lens L11b having a plano-convex shape with a flat surface facing the object side, and a second meniscus lens L12b cemented to the image side of the second positive lens L11b with a concave surface facing the object side. The second cemented lens CL11b has a positive refractive power overall.

3 is a cross-sectional view showing the configuration of the third immersion microscope objective lens according to the first embodiment. The third immersion microscope objective lens OL (1c) according to the first embodiment is configured similarly to the first immersion microscope objective lens OL (1a), except that the third cemented lens CL11c is disposed closest to the object side instead of the first cemented lens CL11a. The third cemented lens CL11c is composed of a third positive lens L11c having a plano-convex shape with a flat surface facing the object side, and a third meniscus lens L12c cemented to the image side of the third positive lens L11c with a concave surface facing the object side. The third cemented lens CL11c has a positive refractive power as a whole.

When the refractive index nd(IM) of the immersion liquid IM (water) for the d-line (wavelength λ=587.6 nm) is 1.33, the first immersion microscope objective lens OL(1a) is used. That is, in the immersion microscope objective lens according to the first embodiment, the first cemented lens CL11a is selected from the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c, and is disposed closest to the object side. In the series of immersion microscope objective lenses according to the first embodiment, the first immersion microscope objective lens OL(1a) is selected from the first immersion microscope objective lens OL(1a), the second immersion microscope objective lens OL(1b), and the third immersion microscope objective lens OL(1c) and is used.

The following Table 1 lists the values of the parameters of the first immersion microscope objective lens OL(1a) of the first embodiment when the refractive index nd(IM) of the immersion liquid IM for the d-line is 1.33.

(Table 1)
[Overall specifications]
f=8.0
NA = 1.0
D0 = 2.04
β=25x [lens data]
Surface number R D nd νd
1 ∞ 2.0 1.4585** 67.8**
2 -3.460 4.9 1.8830 40.8
3 -7.000 0.1
4 -22.816 3.5 1.4343 95.0
5 -12.395 0.1
6 -91.696 3.5 1.4978 82.5
7 -23.020 0.1
8 -382.205 1.0 1.6134 44.3
9 25.550 11.45 1.4339 95.2
10 -18.751 0.1
11 103.567 1.1 1.8160 46.6
12 21.493 9.1 1.4978 82.5
13 -34.993 0.2
14 31.731 5.1 1.4343 95.0
15 -92.975 1.0**
16 56.522 1.2 1.6516 58.6
17 21.047 6.25 1.4339 95.2
18 -41.902 1.0 1.8160 46.6
19 47.631 0.2
20 13.040 7.5 1.4343 95.0
21 -140.218 5.4 1.5638 60.7
22 9.070 6.35
23 -11.368 1.05 1.6228 57.0
24 24.469 5.15 1.8044 39.6
25 -17.991

When the refractive index nd(IM) of the immersion liquid IM (oil) for the d-line is 1.35, the second immersion microscope objective lens OL(1b) is used. That is, in the immersion microscope objective lens according to the first embodiment, the second cemented lens CL11b is selected and disposed closest to the object side from among the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c. In the series of immersion microscope objective lenses according to the first embodiment, the second immersion microscope objective lens OL(1b) is selected and used from among the first immersion microscope objective lens OL(1a), the second immersion microscope objective lens OL(1b), and the third immersion microscope objective lens OL(1c). When the refractive index nd(IM) of the immersion liquid IM is 1.35, the distance between the first lens group G1 and the second lens group G2 changes compared to when the refractive index nd(IM) of the immersion liquid IM is 1.33.

Table 2 below lists the values of the parameters of the second immersion microscope objective lens OL(1b) of the first embodiment when the refractive index nd(IM) of the immersion liquid IM for the d line is 1.35.

(Table 2)
[Overall specifications]
f=8.0
NA = 1.0
D0 = 1.98
β=25x [lens data]
Surface number R D nd νd
1 ∞ 2.0 1.4875** 70.3**
2 -3.460 4.9 1.8830 40.8
3 -7.000 0.1
4 -22.816 3.5 1.4343 95.0
5 -12.395 0.1
6 -91.696 3.5 1.4978 82.5
7 -23.020 0.1
8 -382.205 1.0 1.6134 44.3
9 25.550 11.45 1.4339 95.2
10 -18.751 0.1
11 103.567 1.1 1.8160 46.6
12 21.493 9.1 1.4978 82.5
13 -34.993 0.2
14 31.731 5.1 1.4343 95.0
15 -92.975 1.35**
16 56.522 1.2 1.6516 58.6
17 21.047 6.25 1.4339 95.2
18 -41.902 1.0 1.8160 46.6
19 47.631 0.2
20 13.040 7.5 1.4343 95.0
21 -140.218 5.4 1.5638 60.7
22 9.070 6.35
23 -11.368 1.05 1.6228 57.0
24 24.469 5.15 1.8044 39.6
25 -17.991

When the refractive index nd(IM) of the immersion liquid IM (oil) for the d-line is 1.38, the second immersion microscope objective lens OL(1b) is used. That is, in the immersion microscope objective lens according to the first embodiment, the second cemented lens CL11b is selected from the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c, and is arranged closest to the object side. In the series of immersion microscope objective lenses according to the first embodiment, the second immersion microscope objective lens OL(1b) is selected from the first immersion microscope objective lens OL(1a), the second immersion microscope objective lens OL(1b), and the third immersion microscope objective lens OL(1c) and is used. When the refractive index nd(IM) of the immersion liquid IM is 1.38, the distance between the first lens group G1 and the second lens group G2 changes compared to when the refractive index nd(IM) of the immersion liquid IM is 1.33 or 1.35.

Table 3 below lists the values of the parameters of the second immersion microscope objective lens OL(1b) of the first embodiment when the refractive index nd(IM) of the immersion liquid IM for the d line is 1.38.

(Table 3)
[Overall specifications]
f=8.0
NA=1.0
D0 = 2.13
β=25x [lens data]
Surface number R D nd νd
1 ∞ 2.0 1.4875** 70.3**
2 -3.460 4.9 1.8830 40.8
3 -7.000 0.1
4 -22.816 3.5 1.4343 95.0
5 -12.395 0.1
6 -91.696 3.5 1.4978 82.5
7 -23.020 0.1
8 -382.205 1.0 1.6134 44.3
9 25.550 11.45 1.4339 95.2
10 -18.751 0.1
11 103.567 1.1 1.8160 46.6
12 21.493 9.1 1.4978 82.5
13 -34.993 0.2
14 31.731 5.1 1.4343 95.0
15 -92.975 0.32**
16 56.522 1.2 1.6516 58.6
17 21.047 6.25 1.4339 95.2
18 -41.902 1.0 1.8160 46.6
19 47.631 0.2
20 13.040 7.5 1.4343 95.0
21 -140.218 5.4 1.5638 60.7
22 9.070 6.35
23 -11.368 1.05 1.6228 57.0
24 24.469 5.15 1.8044 39.6
25 -17.991

When the refractive index nd(IM) of the immersion liquid IM (oil) for the d-line is 1.44, the third immersion microscope objective lens OL(1c) is used. That is, in the immersion microscope objective lens according to the first embodiment, the third cemented lens CL11c is selected from the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c and is disposed closest to the object side. In the series of the immersion microscope objective lens according to the first embodiment,
Among the first immersion microscope objective lens OL(1a), the second immersion microscope objective lens OL(1b), and the third immersion microscope objective lens OL(1c), the third immersion microscope objective lens OL(1c) is selected and used. Note that when the refractive index nd(IM) of the immersion liquid IM is 1.44, the distance between the first lens group G1 and the second lens group G2 changes compared to when the refractive index nd(IM) of the immersion liquid IM is 1.33, 1.35, or 1.38.

Table 4 below lists the values of the parameters of the third immersion microscope objective lens OL(1c) of the first embodiment when the refractive index nd(IM) of the immersion liquid IM for the d line is 1.44.

(Table 4)
[Overall specifications]
f=8.0
NA=1.0
D0 = 2.00
β=25x [lens data]
Surface number R D nd νd
1 ∞ 2.0 1.5638** 60.7**
2 -3.460 4.9 1.8830 40.8
3 -7.000 0.1
4 -22.816 3.5 1.4343 95.0
5 -12.395 0.1
6 -91.696 3.5 1.4978 82.5
7 -23.020 0.1
8 -382.205 1.0 1.6134 44.3
9 25.550 11.45 1.4339 95.2
10 -18.751 0.1
11 103.567 1.1 1.8160 46.6
12 21.493 9.1 1.4978 82.5
13 -34.993 0.2
14 31.731 5.1 1.4343 95.0
15 -92.975 0.962**
16 56.522 1.2 1.6516 58.6
17 21.047 6.25 1.4339 95.2
18 -41.902 1.0 1.8160 46.6
19 47.631 0.2
20 13.040 7.5 1.4343 95.0
21 -140.218 5.4 1.5638 60.7
22 9.070 6.35
23 -11.368 1.05 1.6228 57.0
24 24.469 5.15 1.8044 39.6
25 -17.991

The immersion microscope objective lens according to the first embodiment is an infinity-corrected lens, and is therefore used in combination with a tube lens that forms an image of an object. Here, the tube lens used in combination with the immersion microscope objective lens according to the first embodiment will be described. FIG. 4 is a cross-sectional view showing the configuration of the tube lens used in combination with the immersion microscope objective lens according to the first embodiment. The various aberration diagrams of the immersion microscope objective lens according to the first embodiment are for use in combination with this tube lens. The tube lens IL(1) shown in FIG. 4 is composed of, in order from the object side, a cemented lens CL31 formed by cementing a biconvex positive lens L31 and a biconcave negative lens L32, and a cemented lens CL32 formed by cementing a biconvex positive lens L33 and a biconcave negative lens L34. This tube lens IL(1) is disposed on the image side of the immersion microscope objective lens according to the first embodiment.

The values of the imaging lens specifications are shown in Table 5 below. Note that in the [Lens Data] table, the surface number, R, D, nd, and vd are the same as those shown in the explanations of Tables 1 to 4 above.

(Table 5)
[Lens data]
Surface number R D nd νd
1 75.043 5.1 1.62801 57.03
2 -75.043 2.0 1.74950 35.19
3 1600.580 7.5
4 50.260 5.1 1.66755 41.96
5 -84.541 1.8 1.61266 44.41
6 36.911

Figure 5 shows various aberrations (spherical aberration, field curvature, and distortion) of the first immersion microscope objective lens OL (1a) according to the first embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.33. Figure 6 shows coma aberrations (meridional coma aberration and sagittal coma aberration) of the first immersion microscope objective lens OL (1a) according to the first embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.33.

Figure 7 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion aberration) of the second immersion microscope objective lens OL (1b) according to the first embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.35. Figure 8 is a diagram showing coma aberrations (meridional coma aberration and sagittal coma aberration) of the second immersion microscope objective lens OL (1b) according to the first embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.35. Figure 9 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion aberration) of the second immersion microscope objective lens OL (1b) according to the first embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.38. FIG. 10 shows the coma aberration (meridional coma aberration and sagittal coma aberration) of the second immersion microscope objective lens OL(1b) of the first embodiment when the refractive index nd(IM) of the immersion liquid IM for the d-line is 1.38.

Figure 11 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion aberration) of the third immersion microscope objective lens OL (1c) of the first embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.44. Figure 12 is a diagram showing coma aberrations (meridional coma aberration and sagittal coma aberration) of the third immersion microscope objective lens OL (1c) of the first embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.44.

In each of the aberration diagrams in FIG. 5 to FIG. 12, d denotes the d-line (wavelength λ=587.6 nm), g denotes the g-line (wavelength λ
A indicates various aberrations for the C-line (wavelength λ=435.8 nm), C indicates the C-line (wavelength λ=656.3 nm), and F indicates the F-line (wavelength λ=486.1 nm). In the spherical aberration diagram, the vertical axis indicates the value normalized with the maximum value of the entrance pupil radius set to 1, and the horizontal axis indicates the aberration value [mm] for each light ray. In the aberration diagram showing the field curvature, the solid line indicates the meridional image plane for each wavelength, and the dashed line indicates the sagittal image plane for each wavelength. In the aberration diagram showing the field curvature, the vertical axis indicates the image height [mm], and the horizontal axis indicates the aberration value [mm]. In the distortion aberration diagram, the vertical axis indicates the image height [mm], and the horizontal axis indicates the ratio of aberration in percentage (%). Each coma aberration diagram shows the aberration value when the image height ratio RFH (Relative Field Height) is 0.00 to 1.00. In the aberration diagrams of the following examples, the same reference numerals as in this example are used, and duplicated explanations will be omitted.

From each aberration diagram, it can be seen that the immersion microscope objective lens of the first embodiment has excellent imaging performance, with various aberrations being well corrected even if the type (refractive index) of the immersion liquid is different, by selecting one of the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c. Also, it can be seen that the series of immersion microscope objective lenses of the first embodiment has excellent imaging performance, with various aberrations being well corrected even if the type (refractive index) of the immersion liquid is different, by selecting one of the first immersion microscope objective lens OL (1a), the second immersion microscope objective lens OL (1b), and the third immersion microscope objective lens OL (1c).

Second Example
The second embodiment will be described with reference to Figures 13 to 24 and Tables 6 to 10. The immersion microscope objective lens according to the second embodiment is used with an immersion liquid IM filled between the tip and the cover glass Cv (which holds the object Ob). The refractive index of the cover glass Cv for the d line (wavelength λ = 587.6 nm) is 1.517, and the thickness of the cover glass Cv is 0.17 mm.
13 is a cross-sectional view showing the configuration of the first immersion microscope objective lens according to the second embodiment. The first immersion microscope objective lens OL (2a) according to the second embodiment is composed of, arranged in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power. The first lens group G1 is a lens group that collects a diverging light beam from an object Ob into a converging light beam. The second lens group G2 is a lens group that converts the converging light beam from the first lens group G1 into a parallel light beam.

The first lens group G1 in the first immersion microscope objective lens OL (2a) is composed of, arranged in order from the object side, a first cemented lens CL11a, a positive meniscus lens L13 with its concave surface facing the object side, a cemented lens CL12 formed by cementing together a negative meniscus lens L14 with its convex surface facing the object side and a biconvex positive lens L15, a cemented lens CL13 formed by cementing together a biconvex positive lens L16, a biconvex positive lens L17, a biconcave negative lens L18 and a biconvex positive lens L19, and a cemented lens CL14 formed by cementing together a negative meniscus lens L120 with its convex surface facing the object side and a biconvex positive lens L121. The first cemented lens CL11a is composed of a first positive lens L11a having a plano-convex shape with a flat surface facing the object side, and a first meniscus lens L12a that faces a concave surface facing the object side and is cemented to the image side of the first positive lens L11a. The first cemented lens CL11a has a positive refractive power as a whole.

The second lens group G2 is composed of, arranged in order from the object side, a cemented lens CL21 formed by cementing a positive meniscus lens L21 with a convex surface facing the object side and a negative meniscus lens L22 with a convex surface facing the object side, and a cemented lens CL22 formed by cementing a biconcave negative lens L23 and a biconvex positive lens L24.

Figure 14 is a cross-sectional view showing the configuration of the second immersion microscope objective lens according to the second embodiment. The second immersion microscope objective lens OL (2b) according to the second embodiment is configured in the same manner as the first immersion microscope objective lens OL (2a), except that a second cemented lens CL11b is arranged closest to the object side instead of the first cemented lens CL11a. The second cemented lens CL11b is composed of a second positive lens L11b having a plano-convex shape with a flat surface facing the object side, and a second meniscus lens L12b cemented to the image side of the second positive lens L11b with a concave surface facing the object side. In addition, the second cemented lens CL11b has a positive refractive power overall.

FIG. 15 is a cross-sectional view showing the configuration of a third immersion microscope objective lens according to the second embodiment.
The third immersion microscope objective lens OL(2c) according to the second embodiment is configured similarly to the first immersion microscope objective lens OL(2a), except that a third cemented lens CL11c is disposed closest to the object side instead of the first cemented lens CL11a. The third cemented lens CL11c is configured from a third positive lens L11c having a plano-convex shape with a flat surface facing the object side, and a third meniscus lens L12c cemented to the image side of the third positive lens L11c with a concave surface facing the object side. The third cemented lens CL11c has a positive refractive power as a whole.

When the refractive index nd(IM) of the immersion liquid IM (water) for the d-line (wavelength λ=587.6 nm) is 1.33, the first immersion microscope objective lens OL(2a) is used. That is, in the immersion microscope objective lens according to the second embodiment, the first cemented lens CL11a is selected from the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c, and is disposed closest to the object side. In the series of immersion microscope objective lenses according to the second embodiment, the first immersion microscope objective lens OL(2a) is selected from the first immersion microscope objective lens OL(2a), the second immersion microscope objective lens OL(2b), and the third immersion microscope objective lens OL(2c) and is used.

Table 6 below lists the values of the parameters of the first immersion microscope objective lens OL(2a) of the second embodiment when the refractive index nd(IM) of the immersion liquid IM for the d line is 1.33.

(Table 6)
[Overall specifications]
f=10.0
N.A. = 0.95
D0 = 1.06
β=20x [lens data]
Surface number R D nd νd
1 ∞ 1.0 1.4585** 67.8**
2 -1.901 6.8 1.8830 40.8
3 -7.750 0.2
4 -71.995 3.0 1.6030 65.4
5 -17.100 0.2
6 87.799 1.2 1.7432 49.3
7 26.174 4.9 1.4339 95.2
8 -23.927 0.2
9 48.219 4.4 1.4978 82.5
10 -37.807 0.3
11 49.228 3.2 1.4978 82.5
12 -43.153 1.2 1.6935 53.2
13 21.400 6.2 1.4343 95.0
14 -24.558 0.2
15 40.229 1.2 1.8348 42.7
16 12.549 6.5 1.4343 95.0
17 -39.060 1.8**
18 10.751 4.9 1.4978 82.5
19 45.256 1.2 1.8160 46.6
20 9.791 6.9
21 -10.409 2.3 1.7292 54.6
22 92.148 5.0 1.8044 39.6
23 -14.53

When the refractive index nd(IM) of the immersion liquid IM (oil) for the d-line is 1.35, the second immersion microscope objective lens OL(2b) is used. That is, in the immersion microscope objective lens according to the second embodiment, the second cemented lens CL11b is selected from the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c and is arranged closest to the object side. In the series of immersion microscope objective lenses according to the second embodiment, the second immersion microscope objective lens OL(2b) is selected from the first immersion microscope objective lens OL(2a), the second immersion microscope objective lens OL(2b), and the third immersion microscope objective lens OL(2c) and is used. When the refractive index nd(IM) of the immersion liquid IM is 1.35, the distance between the first lens group G1 and the second lens group G2 changes compared to when the refractive index nd(IM) of the immersion liquid IM is 1.33.

Table 7 below lists the values of the parameters of the second immersion microscope objective lens OL(2b) of the second embodiment when the refractive index nd(IM) of the immersion liquid IM for the d line is 1.35.

(Table 7)
[Overall specifications]
f=10.0
N.A. = 0.95
D0 = 1.005
β=20x [lens data]
Surface number R D nd νd
1∞1.01.4875** 70.3**
2 -1.901 6.8 1.8830 40.8
3 -7.750 0.2
4 -71.995 3.0 1.6030 65.4
5 -17.100 0.2
6 87.799 1.2 1.7432 49.3
7 26.174 4.9 1.4339 95.2
8 -23.927 0.2
9 48.219 4.4 1.4978 82.5
10 -37.807 0.3
11 49.228 3.2 1.4978 82.5
12 -43.153 1.2 1.6935 53.2
13 21.400 6.2 1.4343 95.0
14 -24.558 0.2
15 40.229 1.2 1.8348 42.7
16 12.549 6.5 1.4343 95.0
17 -39.060 2.25**
18 10.751 4.9 1.4978 82.5
19 45.256 1.2 1.8160 46.6
20 9.791 6.9
21 -10.409 2.3 1.7292 54.6
22 92.148 5.0 1.8044 39.6
23 -14.53

When the refractive index nd(IM) of the immersion liquid IM (oil) for the d-line is 1.38, the second immersion microscope objective lens OL(2b) is used. That is, in the immersion microscope objective lens according to the second embodiment, the second cemented lens CL11b is selected and disposed closest to the object side from among the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c. In the series of immersion microscope objective lenses according to the second embodiment, the second immersion microscope objective lens OL(2b) is selected and used from among the first immersion microscope objective lens OL(2a), the second immersion microscope objective lens OL(2b), and the third immersion microscope objective lens OL(2c). When the refractive index nd(IM) of the immersion liquid IM is 1.38, the distance between the first lens group G1 and the second lens group G2 changes compared to when the refractive index nd(IM) of the immersion liquid IM is 1.33 or 1.35.

Table 8 below lists the values of the parameters of the second immersion microscope objective lens OL(2b) of the second embodiment when the refractive index nd(IM) of the immersion liquid IM for the d line is 1.38.

(Table 8)
[Overall specifications]
f=10.0
N.A. = 0.95
D0 = 1.035
β=20x [lens data]
Surface number R D nd νd
1∞1.01.4875** 70.3**
2 -1.901 6.8 1.8830 40.8
3 -7.750 0.2
4 -71.995 3.0 1.6030 65.4
5 -17.100 0.2
6 87.799 1.2 1.7432 49.3
7 26.174 4.9 1.4339 95.2
8 -23.927 0.2
9 48.219 4.4 1.4978 82.5
10 -37.807 0.3
11 49.228 3.2 1.4978 82.5
12 -43.153 1.2 1.6935 53.2
13 21.400 6.2 1.4343 95.0
14 -24.558 0.2
15 40.229 1.2 1.8348 42.7
16 12.549 6.5 1.4343 95.0
17 -39.060 1.15**
18 10.751 4.9 1.4978 82.5
19 45.256 1.2 1.8160 46.6
20 9.791 6.9
21 -10.409 2.3 1.7292 54.6
22 92.148 5.0 1.8044 39.6
23 -14.53

When the refractive index nd(IM) of the immersion liquid IM (oil) for the d-line is 1.44, the third immersion microscope objective lens OL(2c) is used. That is, in the immersion microscope objective lens according to the second embodiment, of the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c, the third cemented lens CL11c is selected and disposed closest to the object side. In the series of immersion microscope objective lenses according to the second embodiment, of the first immersion microscope objective lens OL(2a), the second immersion microscope objective lens OL(2b), and the third immersion microscope objective lens OL(2c), the third immersion microscope objective lens OL(
When the refractive index nd(IM) of the immersion liquid IM is 1.44, the distance between the first lens group G1 and the second lens group G2 changes compared to when the refractive index nd(IM) of the immersion liquid IM is 1.33, 1.35, or 1.38.

Table 9 below lists the values of the parameters of the third immersion microscope objective lens OL(2c) of the second embodiment when the refractive index nd(IM) of the immersion liquid IM for the d line is 1.44.

(Table 9)
[Overall specifications]
f=10.0
N.A. = 0.95
D0 = 1.055
β=20x [lens data]
Surface number R D nd νd
1 ∞ 1.0 1.5168** 64.1**
2 -1.901 6.8 1.8830 40.8
3 -7.750 0.2
4 -71.995 3.0 1.6030 65.4
5 -17.100 0.2
6 87.799 1.2 1.7432 49.3
7 26.174 4.9 1.4339 95.2
8 -23.927 0.2
9 48.219 4.4 1.4978 82.5
10 -37.807 0.3
11 49.228 3.2 1.4978 82.5
12 -43.153 1.2 1.6935 53.2
13 21.400 6.2 1.4343 95.0
14 -24.558 0.2
15 40.229 1.2 1.8348 42.7
16 12.549 6.5 1.4343 95.0
17 -39.060 0.1**
18 10.751 4.9 1.4978 82.5
19 45.256 1.2 1.8160 46.6
20 9.791 6.9
21 -10.409 2.3 1.7292 54.6
22 92.148 5.0 1.8044 39.6
23 -14.53

The immersion microscope objective lens according to the second embodiment is an infinity-corrected lens, and is therefore used in combination with a tube lens that forms an image of an object. Here, the tube lens used in combination with the immersion microscope objective lens according to the second embodiment will be described. FIG. 16 is a cross-sectional view showing the configuration of the tube lens used in combination with the immersion microscope objective lens according to the second embodiment. The various aberration diagrams of the immersion microscope objective lens according to the second embodiment are for use in combination with this tube lens. The tube lens IL (2) shown in FIG. 16 is composed of, in order from the object side, a cemented lens CL31 formed by cementing a biconvex positive lens L31 and a negative meniscus lens L32 with a concave surface facing the object side, and a cemented lens CL32 formed by cementing a negative meniscus lens L33 with a convex surface facing the object side and a positive meniscus lens L34 with a convex surface facing the object side. This tube lens IL (2) is disposed on the image side of the immersion microscope objective lens according to the second embodiment.

The values of the imaging lens specifications are shown in Table 10 below. Note that in the [Lens Data] table, the surface number, R, D, nd, and vd are the same as those shown in the explanations of Tables 6 to 9 above.

(Table 10)
[Lens data]
Surface number R D nd νd
1 128.670 5.0 1.49782 82.56
2 -65.000 3.0 1.62280 57.03
3 -154.409 0.5
4 84.000 3.0 1.61340 44.27
5 48.000 3.0 1.62280 57.03
6 70.000

Figure 17 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion aberration) of the first immersion microscope objective lens OL (2a) according to the second embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.33. Figure 18 is a diagram showing coma aberrations (meridional coma aberration and sagittal coma aberration) of the first immersion microscope objective lens OL (2a) according to the second embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.33.

Figure 19 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion aberration) of the second immersion microscope objective lens OL (2b) according to the second embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.35. Figure 20 is a diagram showing coma aberrations (meridional coma aberration and sagittal coma aberration) of the second immersion microscope objective lens OL (2b) according to the second embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.35. Figure 21 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion aberration) of the second immersion microscope objective lens OL (2b) according to the second embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.38. FIG. 22 shows the coma aberration (meridional coma aberration and sagittal coma aberration) of the second immersion microscope objective lens OL(2b) of the second embodiment when the refractive index nd(IM) of the immersion liquid IM for the d-line is 1.38.

Figure 23 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion aberration) of the third immersion microscope objective lens OL (2c) according to the second embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.44. Figure 24 is a diagram showing coma aberrations (meridional coma aberration and sagittal coma aberration) of the third immersion microscope objective lens OL (2c) according to the second embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.44.

From each aberration diagram, it can be seen that the immersion microscope objective lens of the second embodiment has excellent imaging performance, with various aberrations being well corrected even if the type (refractive index) of the immersion liquid is different, by selecting one of the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c. Also, it can be seen that the series of immersion microscope objective lenses of the second embodiment has excellent imaging performance, with various aberrations being well corrected even if the type (refractive index) of the immersion liquid is different, by selecting one of the first immersion microscope objective lens OL (2a), the second immersion microscope objective lens OL (2b), and the third immersion microscope objective lens OL (2c).

(Third Example)
The third embodiment will be described with reference to FIGS. 25 to 34 and Tables 11 to 14. The immersion microscope objective lens according to the third embodiment is used in a state where the space between the tip and the object Ob is filled with immersion liquid IM. FIG. 25 is a cross-sectional view showing the configuration of the first immersion microscope objective lens according to the third embodiment. The first immersion microscope objective lens OL (3a) according to the third embodiment is composed of a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power, arranged in order from the object side. The first lens group G1 is a lens group that collects a diverging light beam from the object Ob into a convergent light beam. The second lens group G2 is a lens group that converts the convergent light beam from the first lens group G1 into a parallel light beam.

The first lens group G1 in the first immersion microscope objective lens OL(3a) is composed of, arranged in order from the object side, a first cemented lens CL11a, a positive meniscus lens L13 with its concave surface facing the object side, and a cemented lens CL12 formed by cementing a biconvex positive lens L14, a biconcave negative lens L15, and a biconvex positive lens L16. The first cemented lens CL11a is composed of a biconvex first positive lens L11a and a first meniscus lens L12a cemented to the image side of the first positive lens L11a with its concave surface facing the object side. The first cemented lens CL11a has a positive refractive power overall.

The second lens group G2 is composed of, in order from the object side, a cemented lens CL21 formed by cementing together a negative meniscus lens L21 with a convex surface facing the object side, a biconvex positive lens L22, and a negative meniscus lens L23 with a concave surface facing the object side; a cemented lens CL22 formed by cementing together a biconvex positive lens L24 and a biconcave negative lens L25; and a cemented lens CL23 formed by cementing together a biconcave negative lens L26 and a biconvex positive lens L27.

Figure 26 is a cross-sectional view showing the configuration of the second immersion microscope objective lens according to the third embodiment. The second immersion microscope objective lens OL (3b) according to the third embodiment is configured in the same manner as the first immersion microscope objective lens OL (3a), except that a second cemented lens CL11b is arranged closest to the object side instead of the first cemented lens CL11a. The second cemented lens CL11b is composed of a second positive lens L11b with a biconvex shape and a second meniscus lens L12b cemented to the image side of the second positive lens L11b with its concave surface facing the object side. The second cemented lens CL11b has a positive refractive power overall.

Figure 27 is a cross-sectional view showing the configuration of a third immersion microscope objective lens according to the third embodiment. The third immersion microscope objective lens OL (3c) according to the third embodiment is configured in the same manner as the first immersion microscope objective lens OL (3a), except that a third cemented lens CL11c is arranged closest to the object side instead of the first cemented lens CL11a. The third cemented lens CL11c is composed of a third positive lens L11c having a biconvex shape, and a third meniscus lens L12c cemented to the image side of the third positive lens L11c with its concave surface facing the object side. The third cemented lens CL11c has a positive refractive power overall.

When the refractive index nd(IM) of the immersion liquid IM (water) for the d-line (wavelength λ=587.6 nm) is 1.33, the first immersion microscope objective lens OL(3a) is used. That is, in the immersion microscope objective lens according to the third embodiment, the first cemented lens CL11a is selected from the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c, and is disposed closest to the object side. In the series of immersion microscope objective lenses according to the third embodiment, the first immersion microscope objective lens OL(3a) is selected from the first immersion microscope objective lens OL(3a), the second immersion microscope objective lens OL(3b), and the third immersion microscope objective lens OL(3c) and is used.

The following Table 11 lists the values of the parameters of the first immersion microscope objective lens OL(3a) of the third embodiment when the refractive index nd(IM) of the immersion liquid IM for the d-line is 1.33.

(Table 11)
[Overall specifications]
f=4.5
N.A. = 0.80
D0 = 3.30
β=40x [lens data]
Surface number R D nd νd
1 80.0000 1.6912 1.51633** 64.15**
2 -8.8752 2.5950 1.78650 50.00
3 -6.0510 0.2000
4 -15.4999 2.3337 1.49700 81.61
5 -9.1373 0.2000
6 10.5626 3.7112 1.43875 94.97
7 -71.3466 1.0000 1.78650 50.00
8 15.0752 3.9298 1.49700 81.61
9 -22.3245 0.2000**
10 20.1621 1.3847 1.59551 39.29
11 8.9947 5.6341 1.43875 94.97
12 -6.6141 0.9018 1.78650 50.00
13 -19.8617 0.3000
14 6.6746 5.4724 1.49700 81.61
15 -10.8419 2.9912 1.52944 51.72
16 6.5021 4.7029
17 -3.2522 4.9352 1.50378 66.81
18 30.1585 3.6414 1.58144 40.75
19 -9.3897

When the refractive index nd(IM) of the immersion liquid IM (oil) for the d-line is 1.35, the second immersion microscope objective lens OL(3b) is used. That is, in the immersion microscope objective lens of the third embodiment, the second cemented lens CL11b is selected from the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c and is arranged closest to the object side. In the series of immersion microscope objective lenses of the third embodiment, the second immersion microscope objective lens OL(3b) is selected from the first immersion microscope objective lens OL(3a), the second immersion microscope objective lens OL(3b), and the third immersion microscope objective lens OL(3c) and is used. When the refractive index nd(IM) of the immersion liquid IM is 1.35, the distance between the first lens group G1 and the second lens group G2 changes compared to when the refractive index nd(IM) of the immersion liquid IM is 1.33.

The following Table 12 lists the values of the parameters of the second immersion microscope objective lens OL(3b) of the third embodiment when the refractive index nd(IM) of the immersion liquid IM for the d line is 1.35.

(Table 12)
[Overall specifications]
f=4.5
N.A. = 0.80
D0 = 3.4273
β=40x [lens data]
Surface number R D nd νd
1 80.0000 1.6912 1.53996** 59.46**
2 -8.8752 2.5950 1.78650 50.00
3 -6.0510 0.2000
4 -15.4999 2.3337 1.49700 81.61
5 -9.1373 0.2000
6 10.5626 3.7112 1.43875 94.97
7 -71.3466 1.0000 1.78650 50.00
8 15.0752 3.9298 1.49700 81.61
9 -22.3245 0.1800**
10 20.1621 1.3847 1.59551 39.29
11 8.9947 5.6341 1.43875 94.97
12 -6.6141 0.9018 1.78650 50.00
13 -19.8617 0.3000
14 6.6746 5.4724 1.49700 81.61
15 -10.8419 2.9912 1.52944 51.72
16 6.5021 4.7029
17 -3.2522 4.9352 1.50378 66.81
18 30.1585 3.6414 1.58144 40.75
19 -9.3897

When the refractive index nd(IM) of the immersion liquid IM (oil) for the d-line is 1.38, the third immersion microscope objective lens OL(3c) is used. That is, in the immersion microscope objective lens according to the third embodiment, the third cemented lens CL11c is selected from the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c and arranged closest to the object side. In the series of immersion microscope objective lenses according to the third embodiment, the third immersion microscope objective lens OL(3c) is selected from the first immersion microscope objective lens OL(3a), the second immersion microscope objective lens OL(3b), and the third immersion microscope objective lens OL(3c) and used. When the refractive index nd(IM) of the immersion liquid IM is 1.38, the distance between the first lens group G1 and the second lens group G2 changes compared to when the refractive index nd(IM) of the immersion liquid IM is 1.33 or 1.35.

The following Table 13 lists the values of the parameters of the third immersion microscope objective lens OL(3c) of the third embodiment when the refractive index nd(IM) of the immersion liquid IM for the d-line is 1.38.

(Table 13)
[Overall specifications]
f=4.5
N.A. = 0.80
D0 = 3.46515
β=40x [lens data]
Surface number R D nd νd
1 80.0000 1.6912 1.56384** 60.67**
2 -8.8752 2.5950 1.78650 50.00
3 -6.0510 0.2000
4 -15.4999 2.3337 1.49700 81.61
5 -9.1373 0.2000
6 10.5626 3.7112 1.43875 94.97
7 -71.3466 1.0000 1.78650 50.00
8 15.0752 3.9298 1.49700 81.61
9 -22.3245 0.3000**
10 20.1621 1.3847 1.59551 39.29
11 8.9947 5.6341 1.43875 94.97
12 -6.6141 0.9018 1.78650 50.00
13 -19.8617 0.3000
14 6.6746 5.4724 1.49700 81.61
15 -10.8419 2.9912 1.52944 51.72
16 6.5021 4.7029
17 -3.2522 4.9352 1.50378 66.81
18 30.1585 3.6414 1.58144 40.75
19 -9.3897

The immersion microscope objective lens according to the third embodiment is an infinity-corrected lens, and is therefore used in combination with an imaging lens that forms an image of an object. Here, we will explain the imaging lens used in combination with the immersion microscope objective lens according to the third embodiment. FIG. 28 is a cross-sectional view showing the configuration of the imaging lens used in combination with the immersion microscope objective lens according to the third embodiment. The various aberration diagrams of the immersion microscope objective lens according to the third embodiment are for use in combination with this imaging lens. The imaging lens IL (3) shown in FIG. 28 is composed of, in order from the object side, a cemented lens CL31 formed by cementing a biconvex positive lens L31 and a negative meniscus lens L32 with a concave surface facing the object side, and a cemented lens CL32 formed by cementing a biconvex positive lens L33 and a biconcave negative lens L34. This imaging lens IL (3) is arranged on the image side of the immersion microscope objective lens according to the third embodiment.

The values of the imaging lens specifications are shown in Table 14 below. Note that in the [Lens Data] table, the surface number, R, D, nd, and vd are the same as those shown in the explanations of Tables 11 to 13 above.

(Table 14)
[Lens data]
Surface number R D nd νd
1 68.7541 7.7321 1.48749 70.20
2 -37.5679 3.4742 1.80610 40.95
3 -102.8477 0.6973
4 84.3099 6.0238 1.83400 37.16
5 -50.7100 3.0298 1.64450 40.82
6 40.6619

Figure 29 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion aberration) of the first immersion microscope objective lens OL (3a) according to the third embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.33. Figure 30 is a diagram showing coma aberrations (meridional coma aberration and sagittal coma aberration) of the first immersion microscope objective lens OL (3a) according to the third embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.33.

Figure 31 shows various aberrations (spherical aberration, field curvature, and distortion) of the second immersion microscope objective lens OL (3b) of the third embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.35. Figure 32 shows coma aberrations (meridional coma aberration and sagittal coma aberration) of the second immersion microscope objective lens OL (3b) of the third embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.35.

Fig. 33 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion aberration) of the third immersion microscope objective lens OL (3c) according to the third embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.38. Fig. 34 is a diagram showing coma aberrations (meridional coma aberration and sagittal coma aberration) of the third immersion microscope objective lens OL (3c) according to the third embodiment when the refractive index nd (IM) of the immersion liquid IM for the d line is 1.38.

From each aberration diagram, it can be seen that the immersion microscope objective lens of the third embodiment has excellent imaging performance, with various aberrations being well corrected even if the type (refractive index) of the immersion liquid is different, by selecting one of the first cemented lens CL11a, the second cemented lens CL11b, and the third cemented lens CL11c. Also, it can be seen that the series of immersion microscope objective lenses of the third embodiment has excellent imaging performance, with various aberrations being well corrected even if the type (refractive index) of the immersion liquid is different, by selecting one of the first immersion microscope objective lens OL (3a), the second immersion microscope objective lens OL (3b), and the third immersion microscope objective lens OL (3c).

Next, a table of [Values Corresponding to Conditional Expressions] is shown below. In this table, values corresponding to each of the conditional expressions (1) to (7) are shown for all the examples (Examples 1 to 3).
Conditional expression (1) 0.85<nL1/np1<0.95
Conditional expression (2) 0.85<nL2/np2<0.95
Conditional formula (3): 1.33≦nL1≦1.51
Condition (4) 1.33≦nL2≦1.51
Condition (5) 0.80≦NA≦1.30
Conditional expression (6) 0.85<nL3/np3<0.95
Conditional formula (7) 1.33≦nL3≦1.51

[Conditional expression corresponding value]
Conditional formula 1st Example 2nd Example 3rd Example (1) 0.91 0.91 0.88
(2) 0.91 0.91 0.88
(2) -2 0.93 0.93 -
(3) 1.33 1.33 1.33
(4) 1.35 1.35 1.35
(4)-2 1.38 1.38 -
(5) 1.0 0.95 0.8
(6) 0.92 0.95 0.88
(7) 1.44 1.44 1.38

According to each of the above embodiments, it is possible to realize an immersion microscope objective lens that can maintain high optical performance even when different types of immersion liquid are used.

The above examples are merely examples of this embodiment, and this embodiment is not limited to these.

G1: first lens group G2: second lens group CL11a: first cemented lens CL11b: second cemented lens CL11c: third cemented lens

Claims (11)

The optical system has a first lens group, which has a positive refractive power and converts a light beam from an object into a convergent light beam, and a second lens group, which has a negative refractive power and converts the convergent light beam from the first lens group into a parallel light beam, arranged in order from the object side;
the first lens group includes a first cemented lens having positive refractive power and disposed closest to the object side,
the first cemented lens is an immersion microscope objective lens including a first positive lens having a convex surface formed on an image side, and a first meniscus lens cemented to the image side of the first positive lens with its concave surface facing an object side,
the first cemented lens is held by a first tip holding member,
a lens disposed closer to the image side than the first cemented lens is held by a body holding member;
The first tip portion holding member and the main body portion holding member are configured to be detachably connected to each other,
In the first lens group, the first cemented lens is configured to be replaceable with a second cemented lens having a positive refractive power,
the second cemented lens includes a second positive lens having a convex surface formed on the image side, and a second meniscus lens cemented to the image side of the second positive lens with its concave surface facing the object side,
The refractive index of the second positive lens is different from the refractive index of the first positive lens.
Immersion microscope objectives. 2. The immersion microscope objective lens according to claim 1, which satisfies the following condition:
0.85<nL1/np1<0.95
0.85<nL2/np2<0.95
where np1 is the refractive index of the first positive lens, np2 is the refractive index of the second positive lens, nL1 is the refractive index of the immersion liquid when the first cemented lens is disposed closest to the object, and nL2 is the refractive index of the immersion liquid when the second cemented lens is disposed closest to the object. 3. The immersion microscope objective lens according to claim 1, which satisfies the following condition:
1.33≦nL1≦1.51
1.33≦nL2≦1.51
where nL1 is the refractive index of the immersion liquid when the first cemented lens is disposed closest to the object side, and nL2 is the refractive index of the immersion liquid when the second cemented lens is disposed closest to the object side. 4. The immersion microscope objective lens according to claim 1, which satisfies the following condition:
0.80≦NA≦1.30
where NA is the numerical aperture of the immersion microscope objective lens. The immersion microscope objective lens according to any one of claims 1 to 4, wherein the distance between the first lens group and the second lens group changes depending on the refractive index of the immersion liquid. in the first lens group, the first cemented lens and the second cemented lens are configured to be replaceable with a third cemented lens having a positive refractive power,
the third cemented lens includes a third positive lens having a convex surface formed on the image side, and a third meniscus lens cemented to the image side of the third positive lens with its concave surface facing the object side,
6. The immersion microscope objective lens according to claim 1, wherein the refractive index of the third positive lens is different from the refractive index of the first positive lens and the refractive index of the second positive lens. 7. The immersion microscope objective lens according to claim 6, which satisfies the following condition:
0.85<nL1/np1<0.95
0.85<nL2/np2<0.95
0.85<nL3/np3<0.95
where np1 is the refractive index of the first positive lens, np2 is the refractive index of the second positive lens, np3 is the refractive index of the third positive lens, nL1 is the refractive index of the immersion liquid when the first cemented lens is disposed closest to the object, nL2 is the refractive index of the immersion liquid when the second cemented lens is disposed closest to the object, and nL3 is the refractive index of the immersion liquid when the third cemented lens is disposed closest to the object. 8. The immersion microscope objective lens according to claim 6, which satisfies the following condition:
1.33≦nL1≦1.51
1.33≦nL2≦1.51
1.33≦nL3≦1.51
where nL1 is the refractive index of the immersion liquid when the first cemented lens is disposed closest to the object side, nL2 is the refractive index of the immersion liquid when the second cemented lens is disposed closest to the object side, and nL3 is the refractive index of the immersion liquid when the third cemented lens is disposed closest to the object side. An immersion microscope equipped with an immersion microscope objective lens according to any one of claims 1 to 8. An observation method using an immersion microscope, comprising the steps of:
The immersion microscope comprises an immersion microscope objective lens according to any one of claims 1 to 5,
An observation method in which one of the first cemented lens and the second cemented lens is selected according to a refractive index of an immersion liquid and disposed closest to an object side of the immersion microscope objective lens. The immersion microscope comprises an immersion microscope objective lens according to any one of claims 6 to 8,
The observation method according to claim 10 , wherein one of the first cemented lens, the second cemented lens, and the third cemented lens is selected and placed closest to the object side of the immersion microscope objective lens according to a refractive index of the immersion liquid.

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