JP6562259B2 - Microscope objective lens and microscope apparatus - Google Patents

Description

  The present invention relates to a microscope objective lens or a microscope apparatus provided with a microscope objective lens.

  When attempting to ensure a high numerical aperture (NA) in a microscope objective lens, the overall length of the lens usually becomes long. In particular, the longer the focal length, the longer the overall length. On the other hand, the microscope main body has an upper limit on the clearance between the revolver and the stage. If the entire length is longer than the clearance, the microscope main body cannot be attached to the microscope main body. In addition, a microscope objective lens having a long working distance is required in order to enable observation of an observation object floating in a medium in a thick dish (see, for example, Patent Document 1).

JP 2011-075982 A

  Therefore, there is a need for a microscope objective lens that can form a good image while shortening the overall length while ensuring a working distance, and a microscope apparatus that can observe an observation object that requires a long working distance is desired. .

  The present invention has been made in view of such a problem, and provides a microscope objective lens and a microscope apparatus that are capable of suppressing aberration, ensuring a high numerical aperture (NA) and a long working distance, and suitable for a long focal length. For the purpose.

In order to solve the above problems, a microscope objective lens according to the present invention includes, in order from the object side, have a positive refractive power, a first lens group closer divergent light beam from the object into a parallel light beam, a positive refractive power have a, a second lens group to a convergent light beam from a divergent light beam by surface closest to the object side, substantially consists of three lens groups of the third lens group, the first lens group, the most object side has a cemented lens radius of curvature of the lens surface on the object side is bonded to the meniscus lens having a concave surface facing the first lens and the object side is larger than the lens surface on the image plane side, the third lens group, the most object A meniscus lens-shaped first cemented lens with a concave surface facing the image surface side and a meniscus lens-shaped second cemented lens with a concave surface facing the object side, in order from the side, satisfy the following condition: It is characterized by that.
0.60 ≦ | (n21−n0) / r1 | / (1 / f) ≦ 0.85
0.66 ≦ n21−n0 ≦ 0.85
0.010 ≦ NA × d0 / TL ≦ 0.024
However,
n21: Refractive index of the lens closest to the object side of the second cemented lens n0: Refractive index of the medium contacting the object side of the lens closest to the object side of the second cemented lens r1: Nearest object side of the second cemented lens Radius of curvature of lens surface on the object side of the lens f: focal length of the entire system
NA: Numerical aperture
d0: Distance on the optical axis from the object to the lens surface closest to the object in the first lens group
TL: Overall length
In addition, the microscope objective lens according to the present invention has, in order from the object side, a first lens group that has a positive refractive power and makes a divergent light beam from the object close to a parallel light beam, and has a positive refractive power, and is the most object The first lens group is composed of substantially three lens groups, ie, a second lens group that converts a divergent light beam into a convergent light beam on the side surface, and the third lens group. The first lens having a larger radius of curvature than the lens surface on the image surface side and a meniscus lens having a concave surface facing the object side, and a third lens group in order from the object side to the image surface in order. And a meniscus lens-shaped first cemented lens with a concave surface facing the object side, and a meniscus lens-shaped second cemented lens with a concave surface facing the object side, and satisfying the following condition.
0.60 ≦ | (n21−n0) / r1 | / (1 / f) ≦ 0.85
0.66 ≦ n21−n0 ≦ 0.85
0.9 ≦ f12 / f <1.1
However,
n21: Refractive index of the lens closest to the object side of the second cemented lens
n0: Refractive index of the medium in contact with the object side of the lens closest to the object side of the second cemented lens
r1: radius of curvature of the lens surface on the object side of the lens closest to the object side of the second cemented lens
f: Focal length of the entire system
f12: Composite focal length of the first lens group and the second lens group
In addition, the microscope objective lens according to the present invention has, in order from the object side, a first lens group that has a positive refractive power and makes a divergent light beam from the object close to a parallel light beam, and has a positive refractive power, and is the most object The first lens group is composed of substantially three lens groups, ie, a second lens group that converts a divergent light beam into a convergent light beam on the side surface, and the third lens group. The first lens having a larger radius of curvature than the lens surface on the image surface side and a meniscus lens having a concave surface facing the object side, and a third lens group in order from the object side to the image surface in order. And a meniscus lens-shaped first cemented lens with a concave surface facing the object side, and a meniscus lens-shaped second cemented lens with a concave surface facing the object side, and satisfying the following condition.
0.60 ≦ | (n21−n0) / r1 | / (1 / f) ≦ 0.85
0.66 ≦ n21−n0 ≦ 0.85
0.83 ≦ | r2 / d2 | ≦ 0.95
However,
n21: Refractive index of the lens closest to the object side of the second cemented lens
n0: Refractive index of the medium in contact with the object side of the lens closest to the object side of the second cemented lens
r1: radius of curvature of the lens surface on the object side of the lens closest to the object side of the second cemented lens
f: Focal length of the entire system
r2: radius of curvature of the lens surface closest to the image plane of the cemented lens in the first lens group
d2: distance on the optical axis from the object plane to the lens surface closest to the image plane of the cemented lens of the first lens group
In addition, the microscope objective lens according to the present invention has, in order from the object side, a first lens group that has a positive refractive power and makes a divergent light beam from the object close to a parallel light beam, and has a positive refractive power, and is the most object The first lens group is composed of substantially three lens groups, ie, a second lens group that converts a divergent light beam into a convergent light beam on the side surface, and the third lens group. The first lens having a larger radius of curvature than the lens surface on the image surface side and a meniscus lens having a concave surface facing the object side, and a third lens group in order from the object side to the image surface in order. And a meniscus lens-shaped first cemented lens with a concave surface facing the object side, and a meniscus lens-shaped second cemented lens with a concave surface facing the object side, and satisfying the following condition.
0.60 ≦ | (n21−n0) / r1 | / (1 / f) ≦ 0.85
0.66 ≦ n21−n0 ≦ 0.85
1.20 ≦ D3 / f ≦ 1.65
However,
n21: Refractive index of the lens closest to the object side of the second cemented lens
n0: Refractive index of the medium in contact with the object side of the lens closest to the object side of the second cemented lens
r1: radius of curvature of the lens surface on the object side of the lens closest to the object side of the second cemented lens
f: Focal length of the entire system
D3: Sum of lens thicknesses of the first and second cemented lenses in the third lens group

  When the microscope objective lens according to the present invention is configured as described above, aberration can be suppressed, a high numerical aperture (NA) and a long working distance can be ensured, and a lens suitable for a long focal length can be provided.

It is a lens block diagram of the microscope objective lens which concerns on 1st Example. FIG. 6 is a diagram illustrating various aberrations of the microscope objective lens according to the first example. It is a lens block diagram of the microscope objective lens which concerns on 2nd Example. FIG. 6 is various aberration diagrams of the microscope objective lens according to the second example. It is a lens block diagram of the microscope objective lens which concerns on 3rd Example. FIG. 6 is various aberration diagrams of the microscope objective lens according to the third example. It is a lens block diagram of the microscope objective lens which concerns on 4th Example. FIG. 10 is a diagram illustrating all aberrations of the microscope objective lens according to the fourth example. It is a lens block diagram of the microscope objective lens which concerns on 5th Example. FIG. 10 is a diagram illustrating all aberrations of the microscope objective lens according to the fifth example. It is a lens block diagram of the microscope objective lens which concerns on 6th Example. FIG. 10 is various aberration diagrams of the microscope objective lens according to the sixth example. It is a lens block diagram of the microscope objective lens which concerns on a 7th Example. FIG. 10 is various aberration diagrams of the microscope objective lens according to the seventh example. It is a lens block diagram of the microscope objective lens which concerns on an 8th Example. It is an aberration diagram of the microscope objective lens according to the eighth example. It is a lens block diagram of the imaging lens used with the said microscope objective lens. It is a schematic block diagram of the microscope apparatus provided with the said microscope objective lens.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, the configuration of the microscope objective lens according to the present embodiment will be described with reference to FIG. The microscope objective lens OL includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3. ing.

  In such a microscope objective lens OL, the first lens group G1 is a lens group for bringing a divergent light beam from an object closer to a parallel light beam, and is a lens group from which the divergent light beam is emitted. In the first lens group G1, the first lens L11 having a radius of curvature of the object-side lens surface larger than that of the image-side lens surface and the meniscus lens L12 having a concave surface facing the object side are cemented to the most object side. It has a cemented lens CL11. For example, in FIG. 1, a plano-convex lens is used as the first lens L11.

  The second lens group G2 is a lens group for converting the divergent light beam emitted from the first lens group G1 into a focused light beam. It is desirable that the second lens group G2 has two or more cemented lenses.

  The third lens group G3 is a lens group for converting the focused light beam emitted from the second lens group G2 into a substantially parallel light beam and guiding it to an imaging lens IL described later. The third lens group G3 includes, in order from the object side, a first cemented lens CL31 having a meniscus lens shape with a concave surface facing the image surface side, a second cemented lens CL32 having a meniscus lens shape with a concave surface facing the object side, It is composed of

  Moreover, it is desirable that the microscope objective lens OL according to the present embodiment satisfies the following conditional expressions (1) and (2).

0.60 ≦ | (n21−n0) / r1 | / (1 / f) ≦ 0.85 (1)
0.66 ≦ n21−n0 ≦ 0.85 (2)
However,
n21: Refractive index of the lens closest to the object side of the second cemented lens CL32 of the third lens group G3 n0: of the medium in contact with the object side of the lens closest to the object side of the second cemented lens CL32 of the third lens group G3 Refractive index r1: Radius of curvature of the object side lens surface of the second cemented lens CL32 of the third lens group G3 closest to the object side f: Focal length of the entire system

  This microscope objective lens OL shortens the entire length by converging light beams from an object to be observed by the first lens group G1 and the second lens group G2 at a short distance. That is, the amount of spherical aberration is large because the light rays are bent by making the first lens group G1 and the second lens group G2 have strong refractive power at a short distance. In order to cancel the spherical aberration by the third lens group G3, a strong refractive power is also required on the incident surface side of the second cemented lens CL32 constituting the third lens group G3. Therefore, as shown in the conditional expression (1), the microscope objective lens OL according to the present embodiment has a lens surface closest to the object side of the second cemented lens CL32 (for example, the lens L33 in FIG. 1). The twenty-first surface) has a refractive power of 65% or more with respect to the total refractive power of the microscope objective lens OL, thereby canceling out spherical aberration and reducing the total amount of spherical aberration.

  On the other hand, when the numerical aperture (NA) of the microscope objective lens OL is large, the ray height of the light incident on the second cemented lens CL32 of the third lens group G3 is high. It tends to occur. Therefore, in order to increase the radius of curvature while obtaining the refractive power, the refractive index difference of the boundary surface on the incident side of the second cemented lens CL32 (the 21st surface of the lens L33 described above) is increased to obtain a large refractive power. ing.

  If the lower limit value of the conditional expression (1) is not reached, the negative refractive power of the lens surface closest to the object side of the second cemented lens CL32 is insufficient, and the amount of offset of spherical aberration and Petzval sum are reduced. Is difficult to reduce. In order to secure the effect of the conditional expression (1), it is desirable to set the lower limit value of the conditional expression (1) to 0.61. In order to further secure the effect of the conditional expression (1), it is desirable to set the lower limit value of the conditional expression (1) to 0.62. In order to further secure the effect of the conditional expression (1), it is desirable to set the lower limit value of the conditional expression (1) to 0.63. In order to further secure the effect of the conditional expression (1), it is desirable to set the lower limit value of the conditional expression (1) to 0.64. In order to further secure the effect of the conditional expression (1), it is desirable to set the lower limit value of the conditional expression (1) to 0.65. In order to further secure the effect of the conditional expression (1), it is desirable to set the lower limit value of the conditional expression (1) to 0.66. In order to further secure the effect of the conditional expression (1), it is desirable to set the lower limit value of the conditional expression (1) to 0.67. In order to further secure the effect of the conditional expression (1), it is desirable to set the lower limit value of the conditional expression (1) to 0.68. In order to further secure the effect of the conditional expression (1), it is desirable to set the lower limit of the conditional expression (1) to 0.69. On the other hand, if the upper limit of conditional expression (1) is exceeded, the amount of spherical aberration generated on the object-side lens surface of the second cemented lens CL32 closest to the object side becomes large, resulting in the amount of spherical aberration being reduced. It gets bigger. Further, since the sag amount increases, the total length becomes large. In order to secure the effect of the conditional expression (1), it is desirable to set the upper limit value of the conditional expression (1) to 0.84. In order to further secure the effect of the conditional expression (1), it is desirable to set the upper limit of the conditional expression (1) to 0.83. In order to further secure the effect of the conditional expression (1), it is desirable to set the upper limit of the conditional expression (1) to 0.82.

  Further, if the lower limit of conditional expression (2) is not reached, the radius of curvature of the lens surface on the object side of the lens closest to the object side of the second cemented lens CL32 becomes small in order to gain negative refractive power. As a result, coma increases. In order to secure the effect of the conditional expression (2), it is desirable to set the lower limit value of the conditional expression (2) to 0.67. On the other hand, if the upper limit value of conditional expression (2) is exceeded, the combination of the glass material used for the positive lens on the most image plane side of the second cemented lens CL32 is limited, thereby canceling out the lateral chromatic aberration due to the second cemented lens CL32. The amount is insufficient, resulting in an increase in lateral chromatic aberration.

  The third lens group G3 also has a function of canceling chromatic aberration that occurs in the first lens group G1 and the second lens group G2 (hereinafter referred to as “front group”). The third lens group G3 needs to have a secondary achromatic function in order to aim for an achromatic effect in a wide wavelength range. Therefore, a positive lens on the object side of the first cemented lens CL31 (for example, the lens L31 in FIG. 1) selects a glass material having a low refractive index / low dispersion, while a glass material suitable for secondary chromatic aberration is selected as the first cemented lens CL31. It is necessary to employ a negative lens on the image surface side (for example, the lens L32 in FIG. 1). However, since there is no practical glass material having a high refractive index exceeding 1.66 and appropriate partial dispersion among the glass materials suitable for the secondary chromatic aberration, the image of the first cemented lens CL31. As a result, the refractive index of the negative lens on the surface side cannot give a large refractive index. Therefore, it is very difficult to give a large refractive power so as to eliminate the curvature of field with the negative lens on the image plane side of the first cemented lens CL31.

  On the other hand, in the second cemented lens CL32, a low refractive index / low dispersion glass material is used for the positive lens on the image surface side (for example, the lens L34 in FIG. 1) in order to eliminate chromatic aberration of magnification. For the negative lens (for example, the lens L33 in FIG. 1), a high refractive index / high dispersion glass material is used. At this time, with respect to the function of canceling the secondary chromatic aberration, an amount that can be sufficiently canceled by the first cemented lens CL31 is secured, so that a glass material can be selected for the negative lens on the object side of the second cemented lens CL32. The range is wider than the negative lens on the image plane side of the first cemented lens CL31. Therefore, a high refractive index material is selected here, and a negative lens with a small sag amount and a high refractive power can be adopted. Therefore, the refractive power of the negative lens on the object side of the second cemented lens CL32 is set to (first junction). While preventing the increase of the lens thickness while increasing the lens CL31 relative to the negative lens on the image plane side of the lens CL31, the balance of aberrations (the aberration of the front group and the aberration of the third lens group G3) remains short. Offset).

  Moreover, it is desirable that the microscope objective lens OL according to the present embodiment satisfies the following conditional expression (3).

0.9 ≦ f12 / f <1.1 (3)
However,
f12: Composite focal length of the first lens group G1 and the second lens group G2 f: Focal length of the entire system

  Conditional expression (3) defines the ratio between the combined focal length of the first lens group G1 and the second lens group G2 (front group) and the focal length of the entire system. By satisfying this conditional expression (3), the first lens group G1 and the second lens group G2 gain almost the necessary refractive power, and the third lens group G3 serves as an aberration correction lens group. By assigning various functions to roles, an optical system with a small amount of aberration can be configured as a whole. If the lower limit value of the conditional expression (3) is not reached, the cumulative spherical aberration amount of the first lens group G1 and the second lens group G2 becomes large, so that the third lens group G3 has a very large negative refractive power. An optical surface is required, and it is difficult to suppress an increase in coma aberration. In order to secure the effect of the conditional expression (3), it is desirable to set the lower limit value of the conditional expression (3) to 0.91. In order to further secure the effect of the conditional expression (3), it is desirable to set the lower limit of the conditional expression (3) to 0.92. In order to further secure the effect of the conditional expression (3), it is desirable to set the lower limit of the conditional expression (3) to 0.93. In order to further secure the effect of the conditional expression (3), it is desirable to set the lower limit of the conditional expression (3) to 0.94. In order to further secure the effect of the conditional expression (3), it is desirable to set the lower limit value of the conditional expression (3) to 0.95. On the other hand, if the upper limit value of conditional expression (3) is exceeded, the third lens group G3 needs to compensate for the insufficient refractive power of the first lens group G1 and the second lens group G2, and this occurs in the third lens group G3. As a result, the amount of spherical aberration increases, and as a result, the total amount of spherical aberration increases. In order to secure the effect of the conditional expression (3), it is desirable to set the upper limit of the conditional expression (3) to 1.09.

  Moreover, it is desirable that the microscope objective lens OL according to the present embodiment satisfies the following conditional expression (4).

0.80 ≦ | r2 / d2 | ≦ 0.95 (4)
However,
r2: radius of curvature of the lens surface closest to the image plane of the cemented lens CL11 provided closest to the object side of the first lens group G1 d2: cemented lens CL11 provided closest to the object side of the first lens group G1 from the object plane The distance on the optical axis to the lens surface closest to the image plane

  Conditional expression (4) is obtained from the curvature radius of the lens surface closest to the image plane (for example, the third surface in FIG. 1) and the object surface of the cemented lens CL11 provided on the most object side of the first lens group G1. It defines the ratio of the cemented lens CL11 provided closest to the object side of the lens group G1 to the distance on the optical axis to the lens surface closest to the image plane. The first lens group G1 also has a strong positive value. It shows that it has refractive power. By giving a strong positive refractive power by the cemented lens CL11 of the first lens group G1, it is possible to give a refractive power necessary for refracting a light beam from an object to be observed. On the other hand, the amount of spherical aberration tends to increase, but the amount is corrected by the third lens group G3 as described above. In addition, since the height of the light beam passing through the lens surface closest to the image plane of the cemented lens CL11 of the first lens group G1 is a relatively low position, the amount of coma aberration generated on this lens surface is smaller than that of other refractive surfaces. The increase in coma aberration amount can be suppressed.

  If the lower limit value of the conditional expression (4) is not reached, the number of lenses necessary to obtain the necessary focal length by the first lens group G1 and the second lens group G2 increases, and the overall length of the objective lens becomes long. turn into. In order to secure the effect of the conditional expression (4), it is desirable to set the lower limit value of the conditional expression (4) to 0.81. In order to further secure the effect of the conditional expression (4), it is desirable to set the lower limit value of the conditional expression (4) to 0.82. In order to further secure the effect of the conditional expression (4), it is desirable to set the lower limit value of the conditional expression (4) to 0.83. In order to further secure the effect of the conditional expression (4), it is desirable to set the lower limit of the conditional expression (4) to 0.84. In order to further secure the effect of the conditional expression (4), it is desirable to set the lower limit of the conditional expression (4) to 0.85. In order to further secure the effect of the conditional expression (4), it is desirable to set the lower limit value of the conditional expression (4) to 0.86. On the other hand, if the upper limit value of conditional expression (4) is exceeded, the amount of spherical aberration generated in the first lens group G1 increases, and even if the amount of aberration is canceled out in other lens groups, the amount of aberration can be made sufficiently small. It becomes difficult. In order to secure the effect of the conditional expression (4), it is desirable to set the upper limit of the conditional expression (4) to 0.94. In order to further secure the effect of the conditional expression (4), it is desirable to set the upper limit value of the conditional expression (4) to 0.93. In order to further secure the effect of the conditional expression (4), it is desirable to set the upper limit of the conditional expression (4) to 0.92.

  Moreover, it is desirable that the microscope objective lens OL according to the present embodiment satisfies the following conditional expression (5).

1.20 ≦ D3 / f ≦ 1.65 (5)
However,
D3: Sum of lens thicknesses of the first cemented lens CL31 and the second cemented lens CL32 in the third lens group G3 f: focal length of the entire system

  Conditional expression (5) defines the ratio between the total lens thickness of the first cemented lens CL31 and the second cemented lens CL32 of the third lens group G3 and the focal length of the entire system. Usually, in order to correct coma, the light ray height on the concave surface (the most image side surface of the first cemented lens CL31 and the most object side surface of the second cemented lens CL32) in the third lens group G3 is lowered, In order to reduce the radius of curvature of the concave surface, the total lens thickness D3 of the third lens group G3 tends to increase. However, when the total lens thickness D3 is increased, the entire length is increased, and the same focal length cannot be secured. If the upper limit value of the conditional expression (5) is exceeded, the light ray height at the concave surface of the third lens group G3 becomes low, and the refractive power of this concave surface is determined from the conditional expression (1), so the correction of spherical aberration is insufficient. And Petzval sum reduction. On the other hand, if the lower limit value of conditional expression (5) is not reached, the height of light rays on the concave surface becomes high, which causes an increase in spherical aberration and coma aberration. In order to secure the effect of the conditional expression (5), it is desirable to set the lower limit value of the conditional expression (5) to 1.21. In order to further secure the effect of the conditional expression (5), it is desirable to set the lower limit value of the conditional expression (5) to 1.22. In order to further secure the effect of the conditional expression (5), it is desirable to set the lower limit value of the conditional expression (5) to 1.23.

  Moreover, it is desirable that the microscope objective lens OL according to the present embodiment satisfies the following conditional expression (6).

0.14 ≦ NA × f / TL ≦ 0.16 (6)
However,
NA: numerical aperture TL: total length f: focal length of the entire system

  Conditional expression (6) defines the relationship between the numerical aperture and focal length of the microscope objective lens OL and the total length. Below the lower limit of conditional expression (6), the brightness is insufficient and sufficient resolution cannot be obtained. On the other hand, if the upper limit value of conditional expression (6) is exceeded, the brightness that can be imaged by the optical system of the microscope objective lens OL will be exceeded, and it will be lost in the optical system.

  Moreover, it is desirable that the microscope objective lens OL according to the present embodiment satisfies the following conditional expression (7).

0.010 ≦ NA × d0 / TL ≦ 0.024 (7)
However,
NA: Numerical aperture d0: Distance on the optical axis from the object to the most object side lens surface of the first lens group G1 TL: Total length

  Conditional expression (7) defines the relationship between the numerical aperture of the microscope optical system OL and the distance on the optical axis from the object to the lens surface closest to the object of the first lens group G1 and the total length. If the lower limit value of the conditional expression (7) is not reached, the working distance becomes short, so that workability is deteriorated and sufficient deep part observation becomes impossible. On the other hand, if the upper limit of conditional expression (7) is exceeded, the spread of the light beam becomes large, and the spherical aberration cannot be corrected sufficiently.

  Moreover, it is desirable that the microscope objective lens OL according to the present embodiment satisfies the following conditional expressions (8) and (9).

1.75 ≦ | (Φ0 + Φ1-d × Φ0 × Φ1) / (1 / f) | ≦ 2.30 (8)
1.69 ≦ (n12 + n21) /2≦1.80 (9)
However,
Φ0 = (n0−n12) / r0
Φ1 = (n21−n0) / r1
n0: Refractive index of the medium between the first cemented lens CL31 and the second cemented lens CL32 n12: Refractive index of the medium of the lens on the image plane side of the first cemented lens CL31 n21: Object side of the second cemented lens CL32 Refractive index of the lens medium r0: radius of curvature of the lens surface on the image plane side of the lens on the image plane side of the first cemented lens CL31 r1: lens on the object side of the lens on the object side of the second cemented lens CL32 Radius of curvature of surface d: Air spacing between first cemented lens CL31 and second cemented lens CL32 f: Focal length of entire system

  In the conditional expression (1) described above, of the first cemented lens CL31 and the second cemented lens CL32 constituting the third lens group G3, the concave surface closest to the object side of the second cemented lens CL32 arranged on the image plane side is used. Although the refractive power is defined, the negative refractive power of the first cemented lens CL31 and the second cemented lens CL32 as a whole is relatively strong, and accordingly, the first cemented lens CL31 and the second cemented lens CL31 and the second cemented lens CL32. The refractive index of the negative lens medium constituting the cemented lens CL32 has a high value. This is for correcting the aberration generated in the first lens group G1 and the second lens group G2, similarly to the conditional expression (1) described above, and in particular, for the second cemented lens CL32 on the image plane side. Although the refractive power is increased, the first cemented lens CL31 on the object side also needs to have a high refractive index in order to maintain the refractive power.

  Conditional expression (8) indicates that, in the third lens group G3, the most image side concave surface of the first cemented lens CL31 (for example, the twentieth surface in FIG. 1) and the most object side concave surface of the second cemented lens CL32 (for example, , The ratio of the refractive power in the synthesis of the 21st surface in FIG. 1 and the refractive power of the entire system. If the microscope objective lens OL is low and the numerical aperture (NA) is large, the light beam incident on the first cemented lens CL31 and the second cemented lens CL32 also has a high beam height. Therefore, coma aberration is likely to occur if the radius of curvature of the incident surface is reduced. Therefore, in order to increase the radius of curvature while obtaining the refractive power, the difference in the refractive index of the boundary surface on the incident side of the second cemented lens CL32 is increased as in the conditional expression (2), while the incidence of the first cemented lens CL31 is incident. The difference in refractive index of the side boundary surface is also made as large as possible in a combination of glass materials capable of correcting secondary chromatic aberration, and a large negative refractive power is obtained in the entire third lens group G3. . If the lower limit value of the conditional expression (8) is not reached, the negative refractive power becomes insufficient, and it becomes difficult to reduce the spherical aberration canceling amount and Petzval sum. In order to secure the effect of the conditional expression (8), it is desirable to set the lower limit value of the conditional expression (8) to 1.76. In order to further secure the effect of the conditional expression (8), it is desirable to set the lower limit value of the conditional expression (8) to 1.77. On the other hand, if the upper limit value of conditional expression (8) is exceeded, the amount of spherical aberration occurring on this surface will increase, and as a result, the amount of spherical aberration will increase. Moreover, since the sag amount increases, the total length becomes large. In order to secure the effect of the conditional expression (8), it is desirable to set the upper limit value of the conditional expression (8) to 2.29. In order to further secure the effect of the conditional expression (8), it is desirable to set the upper limit of the conditional expression (8) to 2.28. In order to further secure the effect of the conditional expression (8), it is desirable to set the upper limit value of the conditional expression (8) to 2.27. In order to further secure the effect of the conditional expression (8), it is desirable to set the upper limit value of the conditional expression (8) to 2.26.

  Conditional expression (9) is a medium having a concave surface closest to the image plane of the first cemented lens CL31 and a concave surface closest to the object side of the second cemented lens CL32 (the medium of the lens on the first cemented lens CL31 side, and the first The average value of the refractive index of the medium on the object side of the two-junction lens CL32 is defined. Since the concave surface closest to the image plane of the first cemented lens CL31 and the concave surface closest to the object side of the second cemented lens CL32 have the same role, it is necessary to consider the average value. If the lower limit value of the conditional expression (9) is not reached, the radius of curvature of the concave surface closest to the image plane of the first cemented lens CL31 or the concave surface closest to the object side of the second cemented lens CL32 is required in order to gain negative refractive power. Since it becomes smaller, coma aberration increases. If the upper limit value of conditional expression (9) is exceeded, the amount of chromatic aberration cancellation by the first cemented lens CL31 or the second cemented lens CL32 becomes insufficient, resulting in an increase in chromatic aberration.

  Note that the conditions and configurations described above each exhibit the above-described effects, and are not limited to satisfying all the conditions and configurations. The above-described effects can be obtained even if the combination of the above conditions or configurations is satisfied.

  In addition, as will be described later, the microscope objective lens according to the present embodiment places an observation target under a cover glass (in the case of an upright microscope) or above (in the case of an inverted microscope), and the tip is immersed in the liquid. An immersion type objective lens used in a microscope for observing the observation target in a soaked state, and designed so that the thickness of the cover glass (for example, 0.17 mm) and the refractive index are predetermined values. ing. Therefore, when there is an error in the thickness of the cover glass, in order to correct aberration (particularly spherical aberration) generated by the cover glass, a part of the lenses (or lens groups) constituting the microscope objective lens OL is placed on the optical axis. The correction ring which corrects this aberration is provided by moving along.

  In the present embodiment, the three-group microscope objective lens OL is shown. However, the above-described configuration conditions and the like can be applied to other group configurations such as the fourth group, the fifth group, and the like. Further, a configuration in which a lens or a lens group is added closest to the object side, or a configuration in which a lens or a lens group is added closest to the image plane side may be used.

  Moreover, it is preferable to use the microscope objective lens OL according to the present embodiment for a microscope apparatus as shown below. The microscope apparatus is shown in FIG. A specimen 180 having an observation target to be observed with the microscope apparatus 100 is placed on the stage 170. This stage 170 has a Z drive mechanism 171 and can move the specimen relative to the microscope objective lens OL along the optical axis direction of the microscope objective lens OL. The stage 170 and the Z drive mechanism 171 are supported by the main body 120. The microscope objective lens OL is mounted on the turret 162. In addition, a transmission illumination unit 220 is disposed on the opposite side of the microscope objective lens OL from the stage 170, and the transmission illumination unit 220 is supported by the column 221. The column 221 is supported by the main body 120. In addition, the microscope apparatus 100 includes an epi-illumination half mirror unit 270, a deflection mirror and a relay optical system (not shown) in the main body 120. Note that the alternate long and short dash line in the figure indicates the path of incident illumination light rays propagating in the main body 120 and the path of scattered light from the observation target.

  Meanwhile, the scattered light from the observation target collected by the microscope objective lens OL is transmitted through the epi-illumination half mirror unit 270, and an eyepiece provided with an eyepiece lens via a deflection mirror and a relay optical system (not shown). Guided to the tube 110. From this eyepiece tube 110, an observer can observe a microscope image of the observation object.

  Also, the epi-illumination illumination unit 210 is also fixed to the main body 120, and the illumination light from the epi-illumination illumination unit 210 is guided to the epi-illumination half mirror unit 270 and reflected toward the microscope objective lens OL.

  In such a microscope apparatus 100, the transmission illumination unit 220 is provided above the stage 170, and the microscope objective lens OL is disposed below. For this reason, the allowable stroke amount of the stage 170 can be obtained only to such a stroke amount that the transmitted illumination unit 220 and the microscope objective lens OL do not interfere with each other. For such a microscope apparatus 100, the microscope objective lens OL according to the above-described embodiment is suitable.

  As described above, in the present embodiment, in the microscope apparatus in which the illumination optical system is provided on one side and the microscope objective lens is provided on the other side with respect to the stage on which the sample is placed, It is preferable to include a microscope objective lens OL.

  Further, instead of the eyepiece tube 110, an imaging optical system and a camera that form an image to be observed from a light beam condensed by the microscope objective lens OL may be attached so that a microscope image can be taken with the camera. .

  Hereinafter, eight examples of the microscope objective lens OL according to the present embodiment will be described. The microscope objective lenses OL1 to OL8 in each embodiment are of the infinity correction type, have the configuration shown in FIG. 17, and are used together with the imaging lens IL having the specifications shown in Table 1. In Table 1, the first column m is the number of each optical surface from the object side, the second column r is the radius of curvature of each optical surface, and the third column d is from each optical surface to the next optical surface. The fourth column νd shows the Abbe number with respect to the d-line (wavelength λ = 587.562 nm), and the fifth column nd shows the refractive index with respect to the d-line. Here, the refractive index of air of 1.00000 is omitted. The description of the specification table is the same in the following examples.

(Table 1)
m r d νd nd
1 128.670 5.0 82.56 1.49782
2 -65.000 3.0 57.03 1.62280
3 -154.409 0.5
4 84.000 3.0 44.27 1.61340
5 48.000 3.0 57.03 1.62280
6 70.000

  The imaging lens IL includes, in order from the object side, a cemented lens in which a biconvex lens L41 and a negative meniscus lens L42 having a concave surface facing the object side are cemented, and a negative meniscus lens L43 having a convex surface facing the object side. It is composed of a cemented lens in which a positive meniscus lens L44 having a convex surface facing the object side is cemented.

[First embodiment]
FIG. 1 used in the above description shows a microscope objective lens OL1 according to the first embodiment. This microscope objective lens OL1 is placed under the cover glass C (in the case of an upright microscope) or above (in the case of an inverted microscope), the observation object (object) is placed, and this observation is performed with the tip immersed in an immersion liquid. An immersion type objective lens used in a microscope for observing an object, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative And a third lens group G3 having a refractive power of 5. The first lens group G1 includes, in order from the object side, a cemented lens CL11 formed by cementing a planoconvex lens L11 having a flat surface toward the object side and a negative meniscus lens L12 having a concave surface toward the object side, and a positive surface having a concave surface directed toward the object side. The lens includes a meniscus lens L13 and a cemented lens in which a negative meniscus lens L14 having a convex surface facing the object side and a biconvex lens L15 are cemented. The second lens group G2 includes, in order from the object side, a biconvex lens L21, a cemented lens obtained by cementing the biconvex lens L22, the biconcave lens L23, and the biconvex lens L24, and a negative meniscus lens L25 having a convex surface facing the object side. It is composed of a cemented lens in which a biconvex lens L26 is cemented. In the third lens group G3, in order from the object side, a positive meniscus lens L31 having a convex surface directed toward the object side and a negative meniscus lens L32 having a convex surface directed toward the object side are cemented, and as a whole have a negative refractive power. Then, the first cemented lens CL31 having a meniscus lens shape with the concave surface facing the image surface side, and the biconcave lens L33 and the biconvex lens L34 are cemented, and the second meniscus lens shape with the concave surface facing the object side as a whole. The lens CL32 is configured.

  Table 2 shows the specifications of the microscope objective lens OL1 according to the first example. In Table 2, f shown in the overall specifications is the focal length of the entire system of the microscope objective lens OL1, NA is the numerical aperture, β is the magnification, and d0 is an object (excluding the thickness of the cover glass C). The distance on the optical axis from the observation object) to the apex of the lens surface (first surface) closest to the object side of the first lens (lens L11) closest to the object side, TL is the total length, and f12 is the first lens group. The combined focal lengths of G1 and the second lens group G2 are shown. The cover glass C or the slide glass C has a thickness of 0.17 mm, a refractive index of 1.52439 with respect to the d line, and an Abbe number of 54.29, and the immersion liquid has a refractive index of 1.33255 and an Abbe number of 55 with respect to the d line. .89. The sign of the lens data is the same as that of the imaging lens IL described above. The curvature radius 0.000 indicates a plane. The lens group focal length indicates the start surface and focal length of each of the first lens group G1, the second lens group G2, and the third lens group G3. The conditional expression corresponding values indicate the values of the conditional expressions (1) to (9) described above.

  Here, the focal length f, the radius of curvature r, the surface interval d, and other length units listed in all the following specification values are generally “mm”, but the optical system is proportionally enlarged or proportional. Since the same optical performance can be obtained even if the image is reduced, the present invention is not limited to this. The description of these symbols and the description of the specification table are the same in the following embodiments.

(Table 2) First Example [Overall Specifications]
f = 10
NA = 0.95
β = 20x
d0 = 1.06
TL = 63.98
f12 = 9.82

[Lens data]
m r d νd nd
1 0.000 1.0 67.85 1.45850
2 -1.901 6.8 40.76 1.88300
3 -7.750 0.2
4 -71.995 3.0 65.44 1.60300
5 -17.100 0.2
6 87.799 1.2 49.26 1.74320
7 26.174 4.9 95.25 1.43385
8 -23.927 0.2
9 48.219 4.4 82.57 1.49782
10 -37.807 0.3
11 49.228 3.2 82.57 1.49782
12 -43.153 1.2 53.21 1.69350
13 21.400 6.2 95.02 1.43425
14 -24.558 0.2
15 40.229 1.2 42.72 1.83481
16 12.549 6.5 95.02 1.43425
17 -39.060 1.8
18 10.751 4.9 82.57 1.49782
19 45.256 1.2 46.62 1.81600
20 9.791 6.9
21 -10.409 2.3 54.61 1.72916
22 92.148 5.0 39.59 1.80440
23 -14.530

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 16.958
Second lens group 9 31.613
Third lens group 18 -98.009

[Conditional expression values]
(1) | (n21−n0) / r1 | / (1 / f) = 0.701
(2) n21−n0 = 0.729
(3) f12 / f = 0.98
(4) | r2 / d2 | = 0.875
(5) D3 / f = 1.340
(6) NA × f / TL = 0.148
(7) NA × d0 / TL = 0.0157
(8) | (Φ1 + Φ2-d × Φ1 × Φ2) / (1 / f) | = 1.937
(9) (n12 + n21) /2=1.773

  Thus, it can be seen that all the conditional expressions (1) to (9) are satisfied in the first embodiment.

  FIG. 2 shows spherical aberration and astigmatism with respect to rays of d-line, C-line (λ = 656.273 nm), F-line (λ = 486.133 nm) and g-line (λ = 435.835 nm) in the first embodiment. Each aberration diagram of aberration, lateral chromatic aberration, meridional coma aberration, sagittal coma aberration, and field curvature is shown. Among these aberration diagrams, the spherical aberration diagram shows the aberration amount with respect to the numerical aperture NA, the astigmatism diagram and the lateral chromatic aberration diagram, and the field curvature diagram shows the aberration amount with respect to the image height Y, and the meridional and sagittal coma aberration diagrams. Indicates the amount of aberration when the image height Y is 11.0 mm, 9.0 mm, 6.0 mm, and 0.0 mm. Further, in the spherical aberration diagram, the lateral chromatic aberration diagram, and the meridional and sagittal coma aberration diagrams, the solid line indicates the d line, the broken line indicates the C line, the alternate long and short dash line indicates the F line, and the alternate long and two short dashes line indicates the g line. Yes. Further, in the astigmatism diagram, the solid line indicates the sagittal image plane for each wavelength, and the broken line indicates the meridional image plane for each wavelength. The explanation of these aberration diagrams is the same in the following examples. As is apparent from the respective aberration diagrams shown in FIG. 2, it is understood that various aberrations are corrected well and excellent imaging performance is secured in the first embodiment.

[Second Embodiment]
FIG. 3 shows a microscope objective lens OL2 according to the second example. This microscope objective lens OL2 is placed under the cover glass C (in the case of an upright microscope) or on the top (in the case of an inverted microscope). An immersion type objective lens used in a microscope for observing an object, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative And a third lens group G3 having a refractive power of 5. The first lens group G1 includes, in order from the object side, a cemented lens CL11 formed by cementing a planoconvex lens L11 having a flat surface toward the object side and a negative meniscus lens L12 having a concave surface toward the object side, and a positive surface having a concave surface directed toward the object side. It is composed of a meniscus lens L13 and a cemented lens in which a biconvex lens L14 and a negative meniscus lens L15 having a concave surface facing the object side are cemented. The second lens group G2 includes, in order from the object side, a biconvex lens L21, a cemented lens in which a negative meniscus lens L22 having a convex surface facing the object side and a biconvex lens L23, and a negative lens having a convex surface directed to the object side. It is composed of a cemented lens in which a meniscus lens L24 and a biconvex lens L25 are cemented. In the third lens group G3, in order from the object side, a positive meniscus lens L31 having a convex surface directed toward the object side and a negative meniscus lens L32 having a convex surface directed toward the object side are cemented, and as a whole have a negative refractive power. Then, the first meniscus lens-shaped first cemented lens CL31 with the concave surface facing the image surface side, the negative meniscus lens L33 with the concave surface facing the object side, and the positive meniscus lens L34 with the concave surface facing the object side are cemented. As a whole, it is composed of a second cemented lens CL32 having a meniscus lens shape with a concave surface facing the object side.

  Table 3 shows specifications of the microscope objective lens OL2 according to the second example.

(Table 3) Third Example [Overall Specifications]
f = 10
NA = 0.90
β = 20x
d0 = 0.85
TL = 63.67
f12 = 9.87

[Lens data]
m r d νd nd
1 0.000 0.9 67.85 1.45850
2 -1.801 7.3 46.62 1.81600
3 -8.054 0.2
4 -238.499 4.7 65.44 1.60300
5 -13.105 0.3
6 50.000 6.3 95.25 1.43385
7 -13.188 1.2 46.62 1.81600
8 -30.209 0.3
9 84.756 3.4 82.52 1.49782
10 -76.809 0.3
11 49.699 1.2 44.27 1.61340
12 18.516 6.5 95.25 1.43385
13 -24.272 0.3
14 73.134 1.1 46.62 1.81600
15 12.522 6.3 95.25 1.43385
16 -36.233 1.5
17 11.437 5.4 82.52 1.49782
18 74.720 1.7 55.52 1.69680
19 9.772 6.5
20 -9.601 2.2 53.21 1.69350
21 -150.000 5.2 39.61 1.80440
22 -14.108

[Lens focal length]
Lens group Start surface Focal length first lens group 1 12.960
Second lens group 9 41.299
Third lens group 17 -137.172

[Conditional expression values]
(1) | (n21−n0) / r1 | / (1 / f) = 0.722
(2) n21−n0 = 0.694
(3) f12 / f = 0.99
(4) | r2 / d2 | = 0.890
(5) D3 / f = 1.450
(6) NA × f / TL = 0.141
(7) NA × d0 / TL = 0.0120
(8) | (Φ1 + Φ2-d × Φ1 × Φ2) / (1 / f) | = 1.770
(9) (n12 + n21) /2=1.695

  Thus, it can be seen that all the conditional expressions (1) to (9) are satisfied in the second embodiment.

  FIG. 4 shows respective aberration diagrams of spherical aberration, astigmatism, lateral chromatic aberration, meridional coma aberration, sagittal coma aberration, and field curvature for the d-line, C-line, F-line and g-line light in this second embodiment. Show. As is apparent from the respective aberration diagrams shown in FIG. 4, it can be seen that in the second embodiment, various aberrations are satisfactorily corrected and excellent imaging performance is secured.

[Third embodiment]
FIG. 5 shows a microscope objective lens OL3 according to the third example. This microscope objective lens OL3 is placed under the cover glass C (in the case of an upright microscope) or on the top (in the case of an inverted microscope), the observation object (object) is placed, and this observation is performed with the tip immersed in immersion liquid. An immersion type objective lens used in a microscope for observing an object, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative And a third lens group G3 having a refractive power of 5. The first lens group G1 includes, in order from the object side, a cemented lens CL11 formed by cementing a planoconvex lens L11 having a flat surface toward the object side and a negative meniscus lens L12 having a concave surface toward the object side, and a positive surface having a concave surface directed toward the object side. The lens includes a meniscus lens L13 and a cemented lens in which a negative meniscus lens L14 having a convex surface facing the object side and a biconvex lens L15 are cemented. The second lens group G2 includes, in order from the object side, a cemented lens in which a biconvex lens L21, a biconcave lens L22, and a biconvex lens L23 are cemented, and a negative meniscus lens L24 and a biconvex lens L25 having a convex surface facing the object side. It is comprised with the cemented lens which joined. In the third lens group G3, in order from the object side, a positive meniscus lens L31 having a convex surface directed toward the object side and a negative meniscus lens L32 having a convex surface directed toward the object side are cemented, and as a whole have a negative refractive power. Then, the first meniscus lens-shaped first cemented lens CL31 with the concave surface facing the image surface side, the negative meniscus lens L33 with the concave surface facing the object side, and the positive meniscus lens L34 with the concave surface facing the object side are cemented. As a whole, it is composed of a second cemented lens CL32 having a meniscus lens shape with a concave surface facing the object side.

  Table 4 shows specifications of the microscope objective lens OL3 according to the third example.

(Table 4) Third Example [Overall Specifications]
f = 10
NA = 0.90
β = 20x
d0 = 1.55
TL = 63.47
f12 = 9.75

[Lens data]
m r d νd nd
1 0.000 1.0 67.85 1.45850
2 -2.380 7.8 40.76 1.88300
3 -8.999 0.2
4 -135.734 3.5 65.44 1.60300
5 -15.188 0.2
6 57.749 1.2 51.51 1.73400
7 22.750 5.5 95.02 1.43425
8 -22.318 0.3
9 22.930 6.5 82.57 1.49782
10 -19.900 1.2 53.21 1.69350
11 23.000 5.8 95.02 1.43425
12 -22.372 0.3
13 38.191 1.2 42.72 1.83481
14 11.489 5.8 95.02 1.43425
15 -56.791 1.8
16 10.573 4.9 82.52 1.49782
17 36.594 1.2 46.62 1.81600
18 9.578 6.8
19 -9.418 1.6 55.52 1.69680
20 -211.237 5.0 39.59 1.80440
21 -13.099

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 11.904
Second lens group 9 64.170
Third lens group 16 -128.912

[Conditional expression values]
(1) | (n21−n0) / r1 | / (1 / f) = 0.740
(2) n21−n0 = 0.697
(3) f12 / f = 0.98
(4) | r2 / d2 | = 0.869
(5) D3 / f = 1.270
(6) NA × f / TL = 0.142
(7) NA × d0 / TL = 0.0220
(8) | (Φ1 + Φ2-d × Φ1 × Φ2) / (1 / f) | = 2.020
(9) (n12 + n21) /2=1.756

  Thus, it can be seen that all the conditional expressions (1) to (9) are satisfied in the third embodiment.

  FIG. 6 shows respective aberration diagrams of spherical aberration, astigmatism, lateral chromatic aberration, meridional coma aberration, sagittal coma aberration, and field curvature for the rays of d-line, C-line, F-line and g-line in the third embodiment. Show. As is apparent from the respective aberration diagrams shown in FIG. 6, it is understood that various aberrations are corrected well and excellent imaging performance is ensured in the third embodiment.

[Fourth embodiment]
FIG. 7 shows a microscope objective lens OL4 according to the fourth example. This microscope objective lens OL4 is placed on the observation object (object) under the cover glass C (in the case of an upright microscope) or above (in the case of an inverted microscope), and this observation is performed with the tip immersed in immersion liquid. An immersion type objective lens used in a microscope for observing an object, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative And a third lens group G3 having a refractive power of 5. The first lens group G1 includes, in order from the object side, a cemented lens CL11 formed by cementing a planoconvex lens L11 having a flat surface toward the object side and a negative meniscus lens L12 having a concave surface toward the object side, and a positive surface having a concave surface directed toward the object side. The lens includes a meniscus lens L13 and a cemented lens in which a negative meniscus lens L14 having a convex surface facing the object side and a biconvex lens L15 are cemented. The second lens group G2 includes, in order from the object side, a cemented lens in which a biconvex lens L21, a biconcave lens L22, and a biconvex lens L23 are cemented, and a negative meniscus lens L24 and a biconvex lens L25 having a convex surface facing the object side. It is comprised with the cemented lens which joined. In the third lens group G3, in order from the object side, a positive meniscus lens L31 having a convex surface directed toward the object side and a negative meniscus lens L32 having a convex surface directed toward the object side are cemented, and as a whole have a negative refractive power. Then, the first meniscus lens-shaped first cemented lens CL31 with the concave surface facing the image surface side, the negative meniscus lens L33 with the concave surface facing the object side, and the positive meniscus lens L34 with the concave surface facing the object side are cemented. As a whole, it is composed of a second cemented lens CL32 having a meniscus lens shape with a concave surface facing the object side.

  Table 5 shows specifications of the microscope objective lens OL4 according to the fourth example.

(Table 5) Fourth Example [Overall Specifications]
f = 10
NA = 0.95
β = 20x
d0 = 1.55
TL = 63.81
f12 = 9.93

[Lens data]
m r d νd nd
1 0.000 1.2 67.85 1.45850
2 -2.542 7.1 40.76 1.88300
3 -8.500 0.2
4 -76.420 2.9 65.44 1.60300
5 -15.218 0.2
6 104.191 1.2 51.51 1.73400
7 24.673 6.0 95.25 1.43385
8 -18.068 0.2
9 21.717 7.0 82.57 1.49782
10 -27.765 1.2 53.21 1.69350
11 29.153 5.4 95.02 1.43425
12 -26.824 0.2
13 41.785 1.2 42.72 1.83481
14 11.755 6.3 95.02 1.43425
15 -38.708 1.8
16 10.796 4.6 82.52 1.49782
17 58.125 1.6 46.62 1.81600
18 9.899 7.6
19 -9.305 1.2 57.35 1.67000
20 -79.115 5.0 39.59 1.80440
21 -12.956

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1
Second lens group 9 49.712
Third lens group 16 -111.885

[Conditional expression values]
(1) | (n21−n0) / r1 | / (1 / f) = 0.720
(2) n21−n0 = 0.670
(3) f12 / f = 0.99
(4) | r2 / d2 | = 0.863
(5) D3 / f = 1.240
(6) NA × f / TL = 0.149
(7) NA × d0 / TL = 0.0231
(8) | (Φ1 + Φ2-d × Φ1 × Φ2) / (1 / f) | = 1.995
(9) (n12 + n21) /2=1.743

  Thus, it can be seen that all the conditional expressions (1) to (9) are satisfied in the fourth embodiment.

  FIG. 8 shows respective aberration diagrams of spherical aberration, astigmatism, lateral chromatic aberration, meridional coma aberration, sagittal coma aberration, and curvature of field for the d-line, C-line, F-line and g-line rays in the fourth embodiment. Show. As is apparent from the respective aberration diagrams shown in FIG. 8, it is understood that various aberrations are corrected satisfactorily and excellent imaging performance is secured in the fourth embodiment.

[Fifth embodiment]
FIG. 9 shows a microscope objective lens OL5 according to the fifth example. This microscope objective lens OL5 is placed on the observation object (object) under the cover glass C (in the case of an upright microscope) or above (in the case of an inverted microscope), and this observation is performed with the tip immersed in immersion liquid. An immersion type objective lens used in a microscope for observing an object, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative And a third lens group G3 having a refractive power of 5. The first lens group G1 includes, in order from the object side, a cemented lens CL11 formed by cementing a planoconvex lens L11 having a flat surface toward the object side and a negative meniscus lens L12 having a concave surface toward the object side, and a positive surface having a concave surface directed toward the object side. The lens includes a meniscus lens L13, a cemented lens in which a biconcave lens L14 and a biconvex lens L15 are cemented, and a biconvex lens L16. The second lens group G2 includes, in order from the object side, a cemented lens in which a biconvex lens L21, a biconcave lens L22, and a biconvex lens L23 are cemented, and a negative meniscus lens L24 and a biconvex lens L25 having a convex surface facing the object side. It is comprised with the cemented lens which joined. In the third lens group G3, in order from the object side, a positive meniscus lens L31 having a convex surface directed toward the object side and a negative meniscus lens L32 having a convex surface directed toward the object side are cemented, and as a whole have a negative refractive power. Then, the first meniscus lens-shaped first cemented lens CL31 with the concave surface facing the image surface side, the negative meniscus lens L33 with the concave surface facing the object side, and the positive meniscus lens L34 with the concave surface facing the object side are cemented. As a whole, it is composed of a second cemented lens CL32 having a meniscus lens shape with a concave surface facing the object side.

  Table 6 shows specifications of the microscope objective lens OL5 according to the fifth example.

(Table 6) Fifth Example [Overall Specifications]
f = 10
NA = 1.00
β = 20x
d0 = 0.65
TL = 63.83
f12 = 9.55

[Lens data]
m r d νd nd
1 0.000 1.0 67.85 1.45850
2 -1.901 6.8 40.76 1.88300
3 -7.371 0.2
4 -144.200 2.3 65.44 1.60300
5 -18.056 0.2
6 -462.353 1.2 49.26 1.74320
7 24.751 4.9 95.25 1.43385
8 -21.013 0.2
9 49.573 6.0 82.57 1.49782
10 -33.053 0.2
11 37.468 3.3 82.57 1.49782
12 -89.669 1.2 53.21 1.69350
13 24.530 6.2 95.25 1.43385
14 -24.594 0.2
15 51.232 1.2 42.72 1.83481
16 12.688 6.7 95.02 1.43425
17 -28.786 0.5
18 10.587 4.5 82.57 1.49782
19 37.397 1.2 46.62 1.81600
20 9.472 7.3
21 -9.604 2.7 54.61 1.72916
22 -387.144 5.3 39.59 1.80440
23 -14.091

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 10.526
Second lens group 11 56.212
Third lens group 18 -82.783

[Conditional expression values]
(1) | (n21−n0) / r1 | / (1 / f) = 0.759
(2) n21−n0 = 0.729
(3) f12 / f = 0.95
(4) | r2 / d2 | = 0.872
(5) D3 / f = 1.370
(6) NA × f / TL = 0.157
(7) NA × d0 / TL = 0.0102
(8) | (Φ1 + Φ2-d × Φ1 × Φ2) / (1 / f) | = 2.98
(9) (n12 + n21) /2=1.773

  Thus, it can be seen that all the conditional expressions (1) to (9) are satisfied in the fifth embodiment.

  FIG. 10 is a diagram showing spherical aberration, astigmatism, lateral chromatic aberration, meridional coma aberration, sagittal coma aberration, and field curvature for d-line, C-line, F-line, and g-line in this fifth embodiment. Show. As is apparent from the respective aberration diagrams shown in FIG. 10, it is understood that various aberrations are satisfactorily corrected and excellent imaging performance is secured in the fifth embodiment.

[Sixth embodiment]
FIG. 11 shows a microscope objective lens OL6 according to the sixth example. This microscope objective lens OL6 is placed under the cover glass C (in the case of an upright microscope) or on the top (in the case of an inverted microscope), the observation object (object) is placed, and this observation is performed with the tip immersed in an immersion liquid. An immersion type objective lens used in a microscope for observing an object, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative And a third lens group G3 having a refractive power of 5. The first lens group G1 includes, in order from the object side, a cemented lens CL11 formed by cementing a planoconvex lens L11 having a flat surface toward the object side and a negative meniscus lens L12 having a concave surface toward the object side, and a positive surface having a concave surface directed toward the object side. The lens includes a meniscus lens L13 and a cemented lens in which a negative meniscus lens L14 having a convex surface facing the object side and a biconvex lens L15 are cemented. The second lens group G2 includes, in order from the object side, a cemented lens in which a positive meniscus lens L21 having a convex surface facing the object side, a negative meniscus lens L22 having a convex surface facing the object side, and a biconvex lens L23, and It is composed of a cemented lens in which a negative meniscus lens L24 having a convex surface facing the object side and a biconvex lens L25 are cemented. In the third lens group G3, in order from the object side, a positive meniscus lens L31 having a convex surface directed toward the object side and a negative meniscus lens L32 having a convex surface directed toward the object side are cemented, and as a whole have a negative refractive power. Then, the first meniscus lens-shaped first cemented lens CL31 with the concave surface facing the image surface side, the negative meniscus lens L33 with the concave surface facing the object side, and the positive meniscus lens L34 with the concave surface facing the object side are cemented. As a whole, it is composed of a second cemented lens CL32 having a meniscus lens shape with a concave surface facing the object side.

  Table 7 shows the specifications of the microscope objective lens OL6 according to the sixth example.

(Table 7) Sixth Example [Overall Specifications]
f = 8
NA = 1.10
β = 25x
d0 = 0.75
TL = 59.47
f12 = 8.68

[Lens data]
m r d νd nd
1 0.000 1.0 67.85 1.45850
2 -2.040 5.7 40.76 1.88300
3 -6.560 0.2
4 -35.789 3.2 71.31 1.56907
5 -11.483 0.2
6 71.352 2.0 44.27 1.61340
7 22.857 6.5 95.25 1.43385
8 -19.584 0.2
9 23.789 2.2 82.57 1.49782
10 43.143 1.2 44.27 1.61340
11 17.770 6.6 95.02 1.43425
12 -33.082 0.2
13 33.551 1.2 42.72 1.83481
14 11.479 7.2 95.02 1.43425
15 -25.452 0.2
16 8.789 4.5 82.52 1.49782
17 25.025 1.0 42.72 1.83481
18 7.191 7.8
19 -7.774 1.5 38.15 1.67300
20 -19.435 6.0 29.57 1.71736
21 -11.470

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 10.282
Second lens group 9 32.421
Third lens group 16 -50.610

[Conditional expression values]
(1) | (n21−n0) / r1 | / (1 / f) = 0.693
(2) n21−n0 = 0.673
(3) f12 / f = 1.09
(4) | r2 / d2 | = 0.881
(5) D3 / f = 1.625
(6) NA × f / TL = 0.148
(7) NA × d0 / TL = 0.139
(8) | (Φ1 + Φ2-d × Φ1 × Φ2) / (1 / f) | = 2.248
(9) (n12 + n21) /2=1.754

  Thus, it can be seen that all the conditional expressions (1) to (9) are satisfied in the sixth embodiment.

  FIG. 12 is a diagram showing spherical aberration, astigmatism, lateral chromatic aberration, meridional coma aberration, sagittal coma aberration, and field curvature for d-line, C-line, F-line, and g-line in this sixth embodiment. Show. As is apparent from the respective aberration diagrams shown in FIG. 12, it is understood that various aberrations are corrected well and excellent imaging performance is secured in the sixth embodiment.

[Seventh embodiment]
FIG. 13 shows a microscope objective lens OL7 according to the seventh example. This microscope objective lens OL7 is placed under the cover glass C (in the case of an upright microscope) or above (in the case of an inverted microscope), the observation object (object) is placed, and this observation is performed with the tip immersed in the immersion liquid. An immersion type objective lens used in a microscope for observing an object, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative And a third lens group G3 having a refractive power of 5. The first lens group G1 includes, in order from the object side, a cemented lens CL11 formed by cementing a planoconvex lens L11 having a flat surface toward the object side and a negative meniscus lens L12 having a concave surface toward the object side, and a positive surface having a concave surface directed toward the object side. The lens includes a meniscus lens L13 and a cemented lens in which a negative meniscus lens L14 having a convex surface facing the object side and a biconvex lens L15 are cemented. The second lens group G2 includes, in order from the object side, a cemented lens in which a biconvex lens L21, a biconcave lens L22, and a biconvex lens L23 are cemented, and a negative meniscus lens L24 and a biconvex lens L25 having a convex surface facing the object side. It is comprised with the cemented lens which joined. In the third lens group G3, in order from the object side, a positive meniscus lens L31 having a convex surface directed toward the object side and a negative meniscus lens L32 having a convex surface directed toward the object side are cemented, and as a whole have a negative refractive power. Then, the first meniscus lens-shaped first cemented lens CL31 with the concave surface facing the image surface side, the negative meniscus lens L33 with the concave surface facing the object side, and the positive meniscus lens L34 with the concave surface facing the object side are cemented. As a whole, it is composed of a second cemented lens CL32 having a meniscus lens shape with a concave surface facing the object side.

  Table 8 shows the specifications of the microscope objective lens OL7 according to the seventh example.

(Table 8) Seventh Example [Overall specifications]
f = 10
NA = 0.90
β = 20x
d0 = 1.55
TL = 63.47
f12 = 9.80

[Lens data]
m r d νd nd
1 0.000 1.0 67.85 1.45850
2 -2.380 7.8 40.76 1.88300
3 -9.025 0.2
4 -112.132 3.5 65.44 1.60300
5 -15.052 0.2
6 57.749 1.2 51.51 1.73400
7 22.750 5.5 95.02 1.43425
8 -22.328 0.3
9 22.770 6.5 82.57 1.49782
10 -20.063 1.2 53.21 1.69350
11 23.000 5.8 95.25 1.43385
12 -21.929 0.3
13 38.375 1.2 42.72 1.83481
14 11.453 5.8 95.02 1.43425
15 -58.253 1.8
16 10.866 4.9 82.52 1.49782
17 24.185 1.2 46.62 1.81600
18 9.666 6.8
19 -9.415 1.6 49.62 1.77250
20 -50.262 5.0 37.16 1.83400
21 -12.800

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 12.064
Second lens group 9 63.419
Third lens group 16 -131.837

[Conditional expression values]
(1) | (n21−n0) / r1 | / (1 / f) = 0.820
(2) n21−n0 = 0.773
(3) f12 / f = 0.98
(4) | r2 / d2 | = 0.872
(5) D3 / f = 1.270
(6) NA × f / TL = 0.142
(7) NA × d0 / TL = 0.0220
(8) | (Φ1 + Φ2-d × Φ1 × Φ2) / (1 / f) | = 2.136
(9) (n12 + n21) /2=1.794

  Thus, it can be seen that all the conditional expressions (1) to (9) are satisfied in the seventh embodiment.

  FIG. 14 shows respective aberration diagrams of spherical aberration, astigmatism, lateral chromatic aberration, meridional coma aberration, sagittal coma aberration, and field curvature for the d-line, C-line, F-line and g-line light in the seventh embodiment. Show. As is apparent from the respective aberration diagrams shown in FIG. 14, it is understood that various aberrations are corrected satisfactorily and excellent imaging performance is secured in the seventh embodiment.

[Eighth embodiment]
FIG. 15 shows a microscope objective lens OL8 according to the eighth example. This microscope objective lens OL8 is placed under the cover glass C (in the case of an upright microscope) or above (in the case of an inverted microscope), the observation object (object) is placed, and this observation is performed with the tip immersed in immersion liquid. An immersion type objective lens used in a microscope for observing an object, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative And a third lens group G3 having a refractive power of 5. The first lens group G1 includes, in order from the object side, a cemented lens CL11 formed by cementing a planoconvex lens L11 having a flat surface toward the object side and a negative meniscus lens L12 having a concave surface toward the object side, and a positive surface having a concave surface directed toward the object side. It is composed of a meniscus lens L13 and a cemented lens in which a biconvex lens L14 and a negative meniscus lens L15 having a concave surface facing the object side are cemented. The second lens group G2 includes, in order from the object side, a cemented lens in which the biconvex lens L21 and the biconcave lens L22 are cemented, and a cemented lens in which the negative meniscus lens L23 having a convex surface facing the object side and the biconvex lens L24 are cemented. And it is comprised with the cemented lens which cemented the negative meniscus lens L25 and the biconvex lens L26 which orient | assigned the convex surface to the object side. In the third lens group G3, in order from the object side, a positive meniscus lens L31 having a convex surface directed toward the object side and a negative meniscus lens L32 having a convex surface directed toward the object side are cemented, and as a whole have a negative refractive power. Then, the first meniscus lens-shaped first cemented lens CL31 with the concave surface facing the image surface side, the negative meniscus lens L33 with the concave surface facing the object side, and the positive meniscus lens L34 with the concave surface facing the object side are cemented. As a whole, it is composed of a second cemented lens CL32 having a meniscus lens shape with a concave surface facing the object side.

  Table 9 shows the specifications of the microscope objective lens OL8 according to the eighth example.

(Table 9) Eighth Example [Overall Specifications]
f = 10
NA = 0.95
β = 20x
d0 = 1.09
TL = 63.15
f12 = 9.62

[Lens data]
m r d νd nd
1 0.000 1.0 70.31 1.48749
2 -1.950 7.0 42.72 1.83481
3 -8.446 0.1
4 -32.369 3.5 65.44 1.60300
5 -11.170 0.2
6 41.174 5.5 95.25 1.43385
7 -14.400 1.4 46.62 1.81600
8 -20.994 1.3
9 22.088 3.5 95.02 1.43425
10 -334.697 1.2 53.97 1.61720
11 113.025 1.7
12 160.956 1.0 44.27 1.61340
13 15.700 5.9 95.02 1.43425
14 -36.164 0.7
15 34.108 1.0 46.62 1.81600
16 11.500 5.9 95.02 1.43425
17 -34.351 0.1
18 10.000 4.9 95.25 1.43385
19 639.880 1.0 53.21 1.69350
20 9.508 6.9
21 -9.400 4.3 55.52 1.69680
22 -99.025 3.8 39.61 1.80440
23 -14.100

[Lens focal length]
Lens group Start surface Focal length First lens group 1 11.301
Second lens group 9 48.824
Third lens group 18 -92.141

[Conditional expression values]
(1) | (n21−n0) / r1 | / (1 / f) = 0.744
(2) n21−n0 = 0.697
(3) f12 / f = 0.96
(4) | r2 / d2 | = 0.929
(5) D3 / f = 1.400
(6) NA × f / TL = 0.150
(7) NA × d0 / TL = 0.0164
(8) | (Φ1 + Φ2-d × Φ1 × Φ2) / (1 / f) | = 1.844
(9) (n12 + n21) /2=1.695

  Thus, it can be seen that all the conditional expressions (1) to (9) are satisfied in the eighth embodiment.

  FIG. 16 is a diagram showing spherical aberration, astigmatism, lateral chromatic aberration, meridional coma aberration, sagittal coma aberration, and field curvature for d-line, C-line, F-line and g-line in this eighth embodiment. Show. As is apparent from the respective aberration diagrams shown in FIG. 16, it is understood that various aberrations are satisfactorily corrected and excellent imaging performance is ensured in the eighth embodiment.

OL (OL1 to OL8) microscope objective lens G1 first lens group CL11 cemented lens G2 second lens group G3 third lens group CL31 first cemented lens CL32 second cemented lens

Claims (10)

From the object side,
Have a positive refractive power, a first lens group closer divergent light beam from the object into a parallel light beam,
Have a positive refractive power, a second lens group to a convergent light beam from a divergent light beam by surface closest to the object side,
Consists of substantially three lens groups with the third lens group,
The first lens group includes a cemented lens in which a first lens having a radius of curvature of a lens surface on the object side larger than that of a lens surface on the image side and a meniscus lens having a concave surface on the object side are cemented on the most object side. Have
The third lens group, in order from the most object side,
A first cemented lens in the shape of a meniscus lens with a concave surface facing the image surface side;
A meniscus lens-shaped second cemented lens with a concave surface facing the object side,
A microscope objective lens characterized by satisfying the following condition:
0.60 ≦ | (n21−n0) / r1 | / (1 / f) ≦ 0.85
0.66 ≦ n21−n0 ≦ 0.85
0.010 ≦ NA × d0 / TL ≦ 0.024
However,
n21: Refractive index of the lens closest to the object side of the second cemented lens n0: Refractive index of the medium contacting the object side of the lens closest to the object side of the second cemented lens r1: Most object of the second cemented lens Radius of curvature of the lens surface on the object side of the lens on the side f: focal length of the entire system
NA: Numerical aperture
d0: Distance on the optical axis from the object to the lens surface closest to the object in the first lens group
TL: Overall length From the object side,
Have a positive refractive power, a first lens group closer divergent light beam from the object into a parallel light beam,
Have a positive refractive power, a second lens group to a convergent light beam from a divergent light beam by surface closest to the object side,
Consists of substantially three lens groups with the third lens group,
The first lens group includes a cemented lens in which a first lens having a radius of curvature of a lens surface on the object side larger than that of a lens surface on the image side and a meniscus lens having a concave surface on the object side are cemented on the most object side. Have
The third lens group, in order from the most object side,
A first cemented lens in the shape of a meniscus lens with a concave surface facing the image surface side;
A meniscus lens-shaped second cemented lens with a concave surface facing the object side,
A microscope objective lens characterized by satisfying the following condition:
0.60 ≦ | (n21−n0) / r1 | / (1 / f) ≦ 0.85
0.66 ≦ n21−n0 ≦ 0.85
0.9 ≦ f12 / f <1.1
However,
n21: Refractive index of the lens closest to the object side of the second cemented lens n0: Refractive index of the medium contacting the object side of the lens closest to the object side of the second cemented lens r1: Most object of the second cemented lens Radius of curvature of the lens surface on the object side of the lens on the side f: focal length of the entire system
f12: Composite focal length of the first lens group and the second lens group From the object side,
Have a positive refractive power, a first lens group closer divergent light beam from the object into a parallel light beam,
Have a positive refractive power, a second lens group to a convergent light beam from a divergent light beam by surface closest to the object side,
Consists of substantially three lens groups with the third lens group,
The first lens group includes a cemented lens in which a first lens having a radius of curvature of a lens surface on the object side larger than that of a lens surface on the image side and a meniscus lens having a concave surface on the object side are cemented on the most object side. Have
The third lens group, in order from the most object side,
A first cemented lens in the shape of a meniscus lens with a concave surface facing the image surface side;
A meniscus lens-shaped second cemented lens with a concave surface facing the object side,
A microscope objective lens characterized by satisfying the following condition:
0.60 ≦ | (n21−n0) / r1 | / (1 / f) ≦ 0.85
0.66 ≦ n21−n0 ≦ 0.85
0.83 ≦ | r2 / d2 | ≦ 0.95
However,
n21: Refractive index of the lens closest to the object side of the second cemented lens n0: Refractive index of the medium contacting the object side of the lens closest to the object side of the second cemented lens r1: Most object of the second cemented lens Radius of curvature of the lens surface on the object side of the lens on the side f: focal length of the entire system
r2: radius of curvature of the lens surface closest to the image plane of the cemented lens of the first lens group
d2: distance on the optical axis from the object plane to the lens surface closest to the image plane of the cemented lens of the first lens group From the object side,
Have a positive refractive power, a first lens group closer divergent light beam from the object into a parallel light beam,
Have a positive refractive power, a second lens group to a convergent light beam from a divergent light beam by surface closest to the object side,
Consists of substantially three lens groups with the third lens group,
The first lens group includes a cemented lens in which a first lens having a radius of curvature of a lens surface on the object side larger than that of a lens surface on the image side and a meniscus lens having a concave surface on the object side are cemented on the most object side. Have
The third lens group, in order from the most object side,
A first cemented lens in the shape of a meniscus lens with a concave surface facing the image surface side;
A meniscus lens-shaped second cemented lens with a concave surface facing the object side,
A microscope objective lens characterized by satisfying the following condition:
0.60 ≦ | (n21−n0) / r1 | / (1 / f) ≦ 0.85
0.66 ≦ n21−n0 ≦ 0.85
1.20 ≦ D3 / f ≦ 1.65
However,
n21: Refractive index of the lens closest to the object side of the second cemented lens n0: Refractive index of the medium contacting the object side of the lens closest to the object side of the second cemented lens r1: Most object of the second cemented lens Radius of curvature of the lens surface on the object side of the lens on the side f: focal length of the entire system
D3: Sum of lens thicknesses of the first cemented lens and the second cemented lens of the third lens group The microscope objective lens according to any one of claims 2 to 4, wherein a condition of the following formula is satisfied.
0.010 ≦ NA × d0 / TL ≦ 0.024
However,
NA: Numerical aperture d0: Distance on the optical axis from the object to the lens surface closest to the object in the first lens group TL: Total length The microscope objective lens according to claim 1, wherein a condition of the following formula is satisfied.
0.9 ≦ f12 / f <1.1
However,
f12: combined focal length of the first lens group and the second lens group f: focal length of the entire system Microscope objective according to any one of claims 1, 2, 4, characterized in that the following conditional expression is satisfied:.
0.80 ≦ | r2 / d2 | ≦ 0.95
However,
r2: radius of curvature of the lens surface closest to the image plane of the cemented lens of the first lens group d2: on the optical axis from the object plane to the lens surface closest to the image plane of the cemented lens of the first lens group distance The microscope objective lens according to any one of claims 1 to 3, wherein a condition of the following formula is satisfied.
1.20 ≦ D3 / f ≦ 1.65
However,
D3: Total lens thickness of the first and second cemented lenses of the third lens group f: Focal length of the entire system The microscope objective lens according to claim 1, wherein a condition of the following formula is satisfied.
0.14 ≦ NA × f / TL ≦ 0.16
However,
NA: numerical aperture TL: total length f: focal length of the entire system The microscope objective lens according to any one of claims 1 to 9 ,
A stage for arranging an observation object arranged on the object side of the microscope objective lens;
And a lighting unit disposed on the opposite side of the stage on which the microscope objective lens is provided with the stage interposed therebetween.

Images