JP7616625B2 - Immersion microscope objective lens, imaging lens and microscope device - Google Patents

Description

The present invention relates to a microscope objective lens system. In particular, the present invention relates to an immersion microscope objective lens, an infinity-type immersion microscope objective lens with a magnification of about 10 to 20 times, and a microscope device using this infinity-type immersion microscope objective lens. In particular, the present invention also relates to an imaging lens and a microscope device using this imaging lens.

Generally, a microscope objective lens system consists of a microscope objective lens and an imaging lens.
Among microscope objective lens systems, microscope objective lenses, particularly immersion microscope objective lenses, are known, for example, from those described in Patent Documents 1 and 2 listed below.
Among microscope objective lens systems, imaging lenses are known, for example, as described in Japanese Patent Application Laid-Open No. 2003-233999 and Japanese Patent Application Laid-Open No. 2003-233999.

Patent Publication No. 2005-189732 Patent Publication 2017-161651 Patent Publication No. 57-195212 Patent Publication No. 2016-75860

Conventional immersion microscope objective lenses and tube lens microscope objective lens systems provide sharp images in and around the center of the screen, but the images are blurred from the middle to the periphery of the screen.

The present invention was made in consideration of these points, and aims to provide a microscope objective lens system that produces a sharp image across the entire screen, from the center to the periphery.

In order to achieve the above object, the immersion microscope objective lens according to the first aspect of the present invention includes, in order from the object OBJ side, a first lens group G1 having positive refractive power overall and consisting of two or more lenses, a second lens group G2 having positive refractive power overall, including a three-lens cemented lens and consisting of seven or more lenses, a third lens group G3 consisting of two or more lenses, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 consisting of two or more lenses and emitting a parallel light beam, at least one of the third lens group G3 and the fifth lens group G5 is configured with three or more lenses, at least a cemented surface C2 having a convex surface facing the object side is provided in the third lens group G3, or a cemented surface C1 having a concave surface facing the object side is provided in the fifth lens group G5, and when a maximum image height is Ih and a maximum effective radius of the lens is RDmax, the following condition (1) is satisfied.
0.35<Ih/RDmax<2.2 (1)

In order to achieve the above object, the imaging lens according to the second aspect of the present invention includes, in order from the object OBJ side, a first lens group IG1 including at least one lens of positive refractive power and one lens of negative refractive power, a second lens group IG2 including at least one lens of positive refractive power, and a third lens group IG3 including at least one lens of positive refractive power and one lens of negative refractive power and having negative refractive power as a whole, and when the distance from the lens surface of the first lens group IG1 closest to the object side to the pupil plane is Lp and the focal length of the entire system is fIm, the following condition (2) is satisfied:
-5.0<Lp/fIm<-0.5 (2)

To achieve the above object, a microscope apparatus according to a third aspect of the present invention includes an illumination optical system for illuminating an object, an immersion microscope objective lens and an imaging lens according to the first aspect for forming an image of the object, and an observation system for observing the image.

Furthermore, in order to achieve the above object, a microscope apparatus according to a fourth aspect of the present invention includes an illumination optical system for illuminating an object, an immersion microscope objective lens for forming an image of the object, an imaging lens according to the second aspect, and an observation system for observing the image.

The present invention makes it possible to provide an immersion microscope objective lens and imaging lens that have a high numerical aperture, yet have excellent flatness over the entire wavelength band used, and produce sharp images even in the middle and periphery of the screen, as well as a microscope device that includes the immersion microscope objective lens or imaging lens.

1 is a diagram showing a first embodiment of an immersion microscope objective lens according to the present invention; 5A to 5C are diagrams showing various aberrations in the first example. FIG. 13 is a diagram showing an immersion microscope objective lens according to a second embodiment of the present invention. 13A to 13C are diagrams showing various aberrations in the second embodiment. FIG. 13 is a diagram showing an immersion microscope objective lens according to a third embodiment of the present invention. 13A to 13C are diagrams showing various aberrations in the third embodiment. FIG. 13 is a diagram showing an imaging lens according to a fourth embodiment of the present invention. 13A to 13C are diagrams showing various aberrations in the fourth embodiment. FIG. 13 is a diagram showing an imaging lens according to a fifth embodiment of the present invention. 13A to 13C are diagrams showing various aberrations in the fifth embodiment. FIG. 13 is a diagram showing an imaging lens according to a sixth embodiment of the present invention. 13A to 13C are diagrams showing various aberrations in the sixth example.

Below, an immersion microscope objective lens and an imaging lens, as well as a microscope apparatus having the immersion microscope objective lens or imaging lens, according to embodiments and examples of the present invention will be described with reference to the drawings. Note that identical parts in the drawings are indicated by the same reference numerals.

First, the immersion microscope objective lens according to the first embodiment will be described.
The immersion microscope objective lens according to the first embodiment is basically an immersion microscope objective lens according to the first aspect described above, and in particular, the first lens group G1 has two or more lenses, the second lens group G2 has seven or more lenses, a fourth lens group G4 with negative refractive power is provided, and at least one of the third lens group G3 and the fifth lens group G5 has a lens configuration of three or more lenses, and at least the third lens group G3 has a bonding surface C2 with a convex surface facing the object side, or the fifth lens group G5 has a bonding surface C1 with a concave surface facing the object side, thereby satisfactorily correcting the field curvature and chromatic aberration of the immersion microscope objective lens.

Note that an immersion microscope objective lens is a microscope objective lens in which the space between the object OBJ and the first lens group G1 is filled with liquid.

Condition (1) is a condition that specifies the preferred size of the objective lens in particular. If the lower limit of condition (1) is exceeded, the lens diameter becomes too large, making it difficult to fit into an actual device, which is undesirable. Also, if the upper limit of condition (1) is exceeded, the lens diameter becomes too small, making it difficult to correct aberrations, which is undesirable. Furthermore, even better results can be obtained by setting the lower limit to 0.45, and very good results can be obtained by setting it to 0.47.

The maximum image height is the maximum object height of the object OBJ multiplied by the magnification of the microscope objective lens, and the maximum effective radius of the lens is the radius of the lens at which the light beam involved in image formation is most widespread.

In particular, in this embodiment, the fifth lens group G5 is configured to emit a parallel light beam, which makes it possible to mount the objective lens on various microscopes, thereby increasing the versatility of the immersion microscope objective lens.
Furthermore, it is preferable that the fourth lens group G4 is disposed in contact with the third lens group G3, and the fifth lens group G5 is disposed in contact with the fourth lens group G4.

In the immersion microscope objective lens of the second embodiment, when a bonding surface provided in the fifth lens group G5 with its concave surface facing the object OBJ is defined as a first bonding surface C1, it is preferable that the refractive power of the first bonding surface C1 is positive, the refractive indices of the media on both sides of the first bonding surface C1 are n6 and n7, respectively, the radius of curvature of the first bonding surface C1 is R1, and the focal length of the entire microscope objective lens system is f, the following condition (3) is satisfied:
0.07 <|(n6-n7)×f/R1 |< 1.2 (3)

This condition is for effectively correcting chromatic coma in the meridional direction. In this specification, chromatic coma means the difference in coma at each wavelength in the visible light range. If the upper limit of this condition (3) is exceeded, the lens shape will be disadvantageous in terms of manufacturing, which is undesirable. Also, if the lower limit of this condition (3) is exceeded, it will be difficult to correct chromatic coma in the meridional direction, which is undesirable.

In order to further improve the performance of the immersion microscope objective lens according to the third embodiment, it is preferable that the first lens group G1 is configured with four or more lenses. In particular, it is preferable that the first lens group G1 includes a negative lens, a biconvex lens, a meniscus lens with a concave surface facing the first object OBJ, and a meniscus lens with a concave surface facing the second object OBJ.

In addition, in the immersion microscope objective lens of the fourth embodiment, when the refractive index of the meniscus lens with its concave surface facing the first object OBJ is n3, it is preferable that the meniscus lens with its concave surface facing the first object OBJ satisfies the following condition (4):
n3>1.7 (4)

This condition (4) is a condition for satisfactorily correcting spherical aberration and Petzval's sum. If condition (4) is not satisfied, spherical aberration and Petzval's sum cannot be satisfactorily corrected. Even better results can be obtained by setting the lower limit at 1.75. This meniscus lens may be either a cemented lens or a single lens.

Furthermore, in the immersion microscope objective lens of the fifth embodiment, it is preferable that the first lens group G1 has a bonding surface with a convex surface facing the object OBJ, and when the refractive index of the medium on the object OBJ side of the bonding surface with the convex surface facing the object side is n1 and the refractive index of the medium on the opposite side is n2, the first lens group G1 satisfies the following condition (5):
n1-n2>0.10 (5)

This condition (5) is a condition for effectively correcting high-order chromatic spherical aberration. Below the lower limit of this condition (5), it becomes difficult to effectively correct high-order chromatic spherical aberration. Even better results can be obtained by setting the lower limit to 0.15.

Furthermore, in the immersion system microscope objective lens of the sixth embodiment, when a bonding surface provided in the third lens group G3 with a convex surface facing the object OBJ is defined as a second bonding surface C2, it is preferable that the refractive power of the second bonding surface C2 is positive, the refractive indices of the media on both sides of the second bonding surface C2 are n4 and n5, respectively, the radius of curvature of the second bonding surface C2 is R2, and the focal length of the entire microscope objective lens system is f, the following condition (6) is satisfied:
0.07 <|(n4-n5)×f/R2 |< 1.2 (6)

Condition (6) is a condition for effectively correcting chromatic coma in the meridional direction. Exceeding the upper limit of condition (6) is undesirable because it makes the lens shape unfavorable in terms of manufacturing. Also, falling below the lower limit of condition (6) is undesirable because it makes it difficult to correct chromatic coma in the meridional direction.

In addition, in the immersion microscope objective lens according to the seventh embodiment, it is preferable that the lens surface of the first lens group closest to the object OBJ is flat. A concave surface may allow air bubbles to be trapped in the lens during actual use, and a convex surface would cause a large amount of spherical aberration, which is undesirable in terms of performance.

In addition, in the immersion microscope objective lens according to the eighth embodiment, it is preferable that the second lens group G2 includes at least two triplet lenses. In this way, it is possible to reduce secondary dispersion.

Furthermore, in the immersion microscope objective lens of the ninth embodiment, when the radius of curvature of the concave surface C3 having negative refractive power that appears first when counting from the object OBJ is R3 and the distance from the object OBJ to the concave surface C3 having negative refractive power that appears first is d, it is preferable that the following condition (7) is satisfied:
-0.3>d/R3>-1.5 (7)

This condition (7) is a condition for effectively correcting spherical aberration in particular. Exceeding the upper limit of condition (7) is undesirable because the overall lens length becomes too long. Also, falling below the lower limit of condition (7) is undesirable because significant spherical aberration occurs.

Furthermore, it is preferable that the immersion microscope objective lens of the tenth embodiment satisfies the following condition (8), where LL is the distance from the object OBJ surface to the final lens surface of the microscope objective lens and θ is the angle of the chief ray corresponding to the maximum image height emerging from the microscope objective lens.
0.00063 < tan θ /LL <0.00105 (8)

This condition (8) is a condition for making the overall size of the lens optimal while maintaining good performance. If the upper limit of condition (8) is exceeded, the overall lens length will be too short, making it difficult to obtain good performance, which is undesirable. Also, if the lower limit of condition (8) is exceeded, the overall lens length will be too long, making it impossible to mount on a microscope device, which is undesirable.

In addition, in the immersion microscope objective lens according to the eleventh embodiment, it is preferable that the third lens group G3 includes a cemented meniscus lens with a convex surface facing the object OBJ. In particular, if the cemented meniscus lens is a three-piece cemented meniscus lens, even better aberration correction is possible.

Furthermore, in the immersion microscope objective lens of the twelfth embodiment, when the radius of curvature of the concave surface C4 of the cemented meniscus lens of the third lens group G3 having a convex surface facing the object side is R4, it is preferable that the following condition (9) is satisfied:
0.35 <|R4|/f <2 (9)

This condition (9) is a condition for maintaining good flatness. It is also a condition for giving concave surface C4 a large refractive power. If the upper limit of condition (9) is exceeded, the overall lens length becomes short, which is undesirable as it becomes difficult to obtain good performance. Also, if the lower limit of condition (9) is exceeded, the overall lens length becomes too long, which is undesirable as it becomes impossible to install it in a microscope device.

In addition, in the immersion microscope objective lens according to the thirteenth embodiment, it is preferable that the fifth lens group G5 includes a cemented meniscus lens with a concave surface facing the object OBJ. In particular, if the cemented meniscus lens is a three-piece cemented meniscus lens, even better aberration correction is possible.

Furthermore, in the immersion microscope objective lens of the fourteenth embodiment, when the radius of curvature of the concave surface C5 of the cemented meniscus lens of the fifth lens group G5, whose concave surface faces the object OBJ, is R5, it is preferable that the following condition (10) is satisfied:
0.4 <|R5|/f＜2.5 (10)

Condition (10) is a condition for maintaining good flatness of the image surface. It is a condition for giving large refractive power to concave surface C5. If the upper limit of condition (10) is exceeded, the overall lens length becomes short, which is undesirable as it becomes difficult to obtain good performance. Also, if the lower limit of condition (10) is exceeded, the overall lens length becomes too long, which is undesirable as it becomes difficult to install it in a microscope device.

Moreover, in the immersion microscope objective lens according to the fifteenth embodiment, when the focal length of the fourth lens group G4 is f4, it is preferable that the following condition (11) be satisfied:
0.5 <|f4|/f < 2 (11)

This condition (11) specifies the appropriate refractive power of the fourth lens group. If the upper limit of condition (11) is exceeded, the overall lens length becomes too short, making it difficult to obtain good performance, which is undesirable. Also, if the lower limit of condition (11) is exceeded, the overall lens length becomes too long, making it difficult to install in a microscope device, which is undesirable.

Furthermore, in the immersion microscope objective lens of the 16th embodiment, when the distance between the third lens group G3 and the fourth lens group G4 is d3, the distance between the fourth lens group G4 and the fifth lens group G5 is d4, the thickness of the cemented meniscus lens of the third lens group G3 with its convex surface facing the object OBJ side is t3, and the thickness of the cemented meniscus lens of the fifth lens group G5 with its concave surface facing the object OBJ side is t5, it is preferable that the following conditions (12) and (13) are satisfied.
d3/t3 <0.75 (12)
d4/t5 <0.35 (13)

These conditions (12) and (13) prescribe the appropriate shapes of the third lens group and the fifth lens group. If the upper limits of both conditions (12) and (13) are exceeded, it becomes difficult to correct coma aberration, which is not preferable.

The imaging lens of the seventeenth embodiment will be described below.
The imaging lens of the seventeenth embodiment is basically an imaging lens according to the second aspect described above, and in particular, by providing three lens groups, mainly correcting chromatic aberration in the first lens group IG1, and correcting spherical aberration, coma aberration, astigmatism, distortion aberration, etc. in the second lens group IG2, the field curvature and chromatic aberration of the imaging lens can be corrected well.

Condition (2) is a condition that specifies the appropriate position state for the imaging lens. If the upper limit of condition (2) is exceeded, the overall dimensions of the microscope apparatus will become too long, which is undesirable. Also, if the lower limit of condition (2) is exceeded, the distance between the imaging lens and the objective lens will become too close, limiting the applications for objects that can be used, and making the imaging lens less versatile, which is undesirable.

In the imaging lens according to the eighteenth embodiment, the first lens group IG1 is a two-lens cemented lens, and it is preferable that the at least one lens with positive refractive power in the first lens group IG1 has a refractive index nd of 1.61 or less and an Abbe number ν of 65 or more. This configuration makes it possible to effectively correct chromatic aberration in particular.

In addition, when the focal length of the first lens group IG1 is f21 and the focal length of the second lens group IG2 is f22, it is preferable that the imaging lens of the 19th embodiment satisfies the following conditions (14) and (15):
0.03<|fIm/f21|<0.85 (14)
0.70<|fIm/f22|<2.00 (15)

These conditions (14) and (15) are conditions for defining an appropriate refractive power arrangement. If the lower limit of condition (14) is exceeded, the refractive power of the first lens group IG1 becomes too large, and the performance becomes the same as that of a conventional imaging lens, which is not preferable. Also, if the upper limit of condition (14) is exceeded, the refractive power of the first lens group IG1 becomes too small, and it is not possible to contribute to aberration correction, which is not preferable.

Beyond the lower limit of condition (15), the refractive power of the second lens group IG2 becomes too large, and the refractive power of the first lens group IG1 becomes too small, which undesirably worsens various aberrations. Also, exceeding the upper limit of condition (15), the refractive power of the second lens group IG2 becomes too small, and the refractive power of the first lens group IG1 becomes too large, which undesirably results in the same aberration correction state as in a conventional imaging lens.

Moreover, in the imaging lens according to the twentieth embodiment, when the focal length of the third lens group IG3 is f23, it is preferable that the following condition (16) be satisfied:
-2.0<f23/fIm<-0.5 (16)

This condition (16) is a condition for determining an appropriate refractive power arrangement. If the upper and lower limits of condition (16) are exceeded, it becomes impossible to perform good correction of each aberration, which is undesirable.

The microscope apparatus according to the twenty-first embodiment includes an illumination optical system for illuminating an object, an immersion microscope objective lens and an imaging lens according to any one of the first to sixteenth embodiments for forming an image of the object, and an observation system for observing the image.

The microscope apparatus according to the twenty-second embodiment includes an illumination optical system for illuminating an object, an immersion microscope objective lens for forming an image of the object, an imaging lens according to any one of the seventeenth to twentieth embodiments, and an observation system for observing the image.

First, the first, second and third embodiments will be described with reference to Figs. 1 to 6. These embodiments are examples of immersion microscope objective lenses.

Each embodiment is composed of, in order from the object OBJ side, a first lens group G1, a second lens group G2, a third lens group G3, a fourth lens group G4, and a fifth lens group G5. In the first, second, and third embodiments, the space between the object OBJ and the first lens group G1 is filled with water (nd=1.34, νd=57.9), and the distance is 3 mm.

(First embodiment)
The immersion microscope objective lens of the first embodiment will be described with reference to Figure 1 and Figures 2(A) to (C). Figure 1 is a diagram showing the immersion microscope objective lens of the first embodiment according to the present invention.

The first lens group G1 is composed of, in order, a cemented lens of a plano-concave lens L11 and a biconvex lens L12, a positive meniscus lens L13 with its concave surface facing the object side, and a positive meniscus lens L14 with its concave surface facing the object side.

The second lens group G2 is composed of, in order, a cemented lens of a biconcave lens L21 and a biconvex lens L22, a cemented triplet of a biconvex lens L23, a biconcave lens L24 and a biconvex lens L25, and a cemented triplet of a negative meniscus lens L26 with its convex surface facing the object side, a biconvex lens L27 and a biconcave lens L28.

The third lens group G3 is composed of a triplet of a biconvex lens L31, a biconcave lens L32, and a positive meniscus lens L33 with its convex surface facing the object side.
The fourth lens group G4 is composed of a negative meniscus lens L41 with a concave surface facing the object side.

The fifth lens group G5 is composed of a triplet of lenses: a positive meniscus lens L51 with its concave surface facing the object side, a biconcave lens L52, and a biconvex lens L53.

The immersion microscope objective lens of this embodiment has a focal length of 12.4 mm, a magnification of 16x, an object side N.A. of 0.8, a maximum object height of 0.75 mm, and a maximum image height Ih of 12.00 mm.

The data for this embodiment are shown in Table 1 below. The table shows, from the left, the surface number, the radius of curvature (r), the surface spacing (d), the refractive index at a wavelength of 588 nm (nd), and the Abbe number (νd), with the radius of curvature r, the surface spacing d, and other lengths generally being measured in units of "mm". However, since the same optical performance can be obtained with proportional enlargement or reduction in an optical system, the units are not limited to "mm". This display method is the same for Tables 2 to 6, which will be described later.

The condition corresponding values in this embodiment are shown below.
RDmax=12.13
Ih/RDmax = 0.99
|(n6-n7)×f/R1 |=0.37
|(n4-n5)×f/R2 |=0.38
n1-n2=0.42
d/R3 = -0.63
(tanθ)/LL=0.000744
|R4|/f=0.69
|R5|/f=1.51
|f4|/f=1.18
d3/t3 = 0.47
d4/t5 = 0.13

Figures 2 (A) to (C) are diagrams showing various aberrations of the immersion microscope objective lens of this embodiment, with Figure 2 (A) showing spherical aberration, Figure 2 (B) showing astigmatism, and Figure 2 (C) showing distortion. An imaging lens is required to create these aberration diagrams, but the first to third embodiments use an ideal imaging lens with a focal length of 200 mm and no aberrations as the imaging lens.

In the spherical aberration diagram of Figure 2 (A), the vertical axis indicates the relative incidence height, and the horizontal axis indicates the amount of aberration. g indicates the g-line with a wavelength of 436 nm, F indicates the F-line with a wavelength of 486 nm, d indicates the d-line with a wavelength of 588 nm, and C indicates the C-line with a wavelength of 656 nm.

The spherical aberration diagrams shown in FIG. 4 for the second embodiment, FIG. 6 for the third embodiment, FIG. 8 for the fourth embodiment, FIG. 10 for the fifth embodiment, and FIG. 12 for the sixth embodiment, which will be described later, are displayed in the same manner as in FIG. 2.

In an astigmatism diagram, the vertical axis represents the object height or angle of incidence, and the horizontal axis represents the amount of aberration. In this specification, the solid line represents the meridional image plane (M) and the dotted line represents the sagittal image plane (S).

Incidentally, in Fig. 2(B) of this embodiment, Fig. 4(B) of the second embodiment, and Fig. 6(B) of the third embodiment, the vertical axis is the object height, while in Fig. 8(B) of the fourth embodiment, Fig. 10(B) of the fifth embodiment, and Fig. 12(B) of the sixth embodiment, the vertical axis is the incidence angle.

In a distortion diagram, the vertical axis shows the object height or angle of incidence, and the horizontal axis shows the amount of distortion expressed as a percentage.

The distortion diagrams are displayed as follows: Fig. 2(C) of this embodiment, Fig. 4(C) of the second embodiment, and Fig. 6(C) of the third embodiment, with the vertical axis representing the object height; and Fig. 8(C) of the fourth embodiment, Fig. 10(C) of the fifth embodiment, and Fig. 12(C) of the sixth embodiment, with the vertical axis representing the angle of incidence.

As can be seen from Figures 2(A) to (C), the immersion microscope objective lens of this embodiment provides good correction of chromatic aberration and good flatness of the image plane.

Second Example
The immersion microscope objective lens of the second embodiment will be described with reference to Fig. 3 and Figs. 4(A) to (C) Fig. 3 is a diagram showing the immersion microscope objective lens of the second embodiment according to the present invention.

The first lens group G1 is composed of, in order, a cemented lens of a plano-concave lens L11 and a biconvex lens L12, a positive meniscus lens L13 with its concave surface facing the object side, and a positive meniscus lens L14 with its concave surface facing the object OBJ side.

The second lens group G2 is composed of, in order from the object OBJ side, a cemented lens of a biconcave lens L21 and a biconvex lens L22, a triplet of a biconvex lens L23, a biconcave lens L24 and a biconvex lens L25, and a triplet of a negative meniscus lens L26 with its convex surface facing the object OBJ side, a biconvex lens L27 and a biconcave lens L28.

The third lens group G3 is composed of a cemented lens of a biconvex lens L31 and a biconcave lens L32.
The fourth lens group G4 is composed of a biconcave lens L41.
The fifth lens group G5 is composed of a triplet of a positive meniscus lens L51 with its concave surface facing the object side, a biconcave lens L52, and a biconvex lens L53.

The immersion microscope objective lens of this embodiment has a focal length f of 12.1 mm, a magnification of 16.5x, an object side N.A. of 0.8, a maximum object height of 0.75 mm, and a maximum image height Ih of 12.38 mm.

Table 2 below shows the data for this example.

The condition corresponding values in this embodiment are shown below.
RDmax=11.29
Ih/RDmax=1.10
|(n6-n7)×f/R1 |=0.36
n1-n2=0.30
d/R3 = -1.00
(tanθ)/LL=0.000767
|R4|/f=0.75
|R5|/f=1.63
|f4|/f=0.93
d3/t3 = 0.63
d4/t5 = 0.17

Figures 4(A) to (C) show various aberration diagrams for the immersion microscope objective lens of this embodiment. As can be seen from Figures 4(A) to (C), the immersion microscope objective lens of this embodiment provides good chromatic aberration correction and good flatness of the image plane.

(Third Example)
The immersion microscope objective lens of the third embodiment will be described with reference to Fig. 5 and Figs. 6(A) to (C) Fig. 5 is a diagram showing the immersion microscope objective lens of the third embodiment according to the present invention.

The first lens group G1 is composed of, in order, a triplet of a plano-concave lens L11, a biconvex lens L12, and a positive meniscus lens L13 with its concave surface facing the object side, and a positive meniscus lens L14 with its concave surface facing the object side.

The second lens group G2 is composed of, in order, a cemented lens of a biconcave lens L21 and a biconvex lens L22, a cemented triplet of a biconvex lens L23, a biconcave lens L24 and a biconvex lens L25, and a cemented triplet of a negative meniscus lens L26 with its convex surface facing the object side, a biconvex lens L27 and a biconcave lens L28.

The third lens group G3 is composed of a triplet of a biconvex lens L31, a biconcave lens L32, and a positive meniscus lens L33 with its convex surface facing the object side.
The fourth lens group G4 is composed of a biconcave lens L41.
The fifth lens group G5 is composed of a triplet of a positive meniscus lens L51 with its concave surface facing the object side, a biconcave lens L52, and a biconvex lens L53.

The immersion microscope objective lens of this embodiment has a focal length f of 12.5 mm, a magnification of 16x, an object side N.A. of 0.8, a maximum object height of 0.75 mm, and a maximum image height Ih of 12.00 mm.

Table 3 below shows the data for this example.

The condition corresponding values in this embodiment are shown below.
RDmax=11.99
Ih/RDmax=1.00
|(n6-n7)×f/R1 |=0.38
|(n4-n5)×f/R2 |=0.39
n1-n2=0.30
d/R3 = -0.64
(tanθ)/LL=0.000747
|R4|/f=0.61
|R5|/f=1.49
d3/t3＝0.45
d4/t5 = 0.13

Figures 6(A) to (C) show various aberration diagrams for the immersion microscope objective lens of this embodiment. As can be seen from Figures 6(A) to (C), the immersion microscope objective lens of this embodiment provides good chromatic aberration correction and good flatness of the image plane.

The fourth, fifth and sixth embodiments will be described below with reference to Figures 7 to 12. These embodiments are embodiments of an imaging lens.
Each embodiment is composed of, in order from the object side, a first lens group IG1, a second lens group IG2, and a third lens group IG3.

(Fourth Example)
The imaging lens of the fourth embodiment will be described with reference to Fig. 7 and Figs. 8(A) to (C). Fig. 7 is a diagram showing the imaging lens of the fourth embodiment according to the present invention.

The first lens group IG1 is composed of a cemented lens of a biconvex lens L1 and a biconcave lens L2.
The second lens group IG2 is composed of a positive meniscus lens L3 with a convex surface facing the object side.
The third lens group IG3 is composed of a cemented lens of a biconvex lens L4 and a biconcave lens L5.

The focal length fIm of the imaging lens in this embodiment is 200 mm. The distance Lp from the lens surface closest to the object to the pupil plane is -100 mm, the pupil diameter is 20 mm, and the maximum angle of incidence is 3 degrees.

Table 4 below shows the data for this example.

The condition corresponding values in this embodiment are shown below.
Lp/fIm=-0.5
|fIm/f21|=0.68
|fIm/f22|=0.96
f23/fIm=-1.22
8A to 8C show various aberration diagrams of the imaging lens of this embodiment. As can be seen from Fig. 8A to 8C, the imaging lens of this embodiment provides good correction of chromatic aberration and good flatness of the image plane.

Fifth Example
The imaging lens of the fifth embodiment will be described with reference to Fig. 9 and Figs. 10(A) to (C). Fig. 9 is a diagram showing the imaging lens of the fifth embodiment according to the present invention.

The first lens group IG1 is composed of a cemented lens of a biconvex lens L1 and a biconcave lens L2.
The second lens group IG2 is composed of a positive meniscus lens L3 with a convex surface facing the object side.
The third lens group IG3 is composed of a cemented lens of a biconvex lens L4 and a biconcave lens L5.

The focal length fIm of the imaging lens in this embodiment is 200 mm. The distance Lp from the lens surface closest to the object to the pupil plane is -50 mm, the pupil diameter is 20 mm, and the maximum angle of incidence is 3 degrees.

Table 5 below shows the data for this example.

The condition corresponding values in this embodiment are shown below.
Lp/fIm=-0.25
|fIm/f21|=0.70
|fIm/f22|=0.88
f23/fIm=-1.07

Figures 10(A) to (C) are diagrams showing various aberrations of the imaging lens of this embodiment. As can be seen from Figures 10(A) to (C), the imaging lens of this embodiment provides good correction of chromatic aberration and good flatness of the image surface.

(Sixth Example)
The imaging lens of the sixth embodiment will be described with reference to Fig. 11 and Figs. 12(A) to (C). Fig. 11 is a diagram showing the imaging lens of the sixth embodiment according to the present invention.

The first lens group IG1 is composed of a cemented lens consisting of a biconvex lens L1 and a negative meniscus lens L2 with its concave surface facing the object side.
The second lens group IG2 is composed of a positive meniscus lens L3 with a convex surface facing the object side.

The third lens group IG3 is composed of a cemented lens of a positive meniscus lens L4 having a convex surface facing the object side and a negative meniscus lens L5 having a convex surface facing the object side.
The focal length fIm of the imaging lens in this embodiment is 180 mm. The distance Lp from the lens surface closest to the object side to the pupil plane is −120 mm, the pupil diameter is 18 mm, and the maximum incident angle is 4 degrees.

Table 6 below shows the data for this example.

The condition corresponding values in this embodiment are shown below.
Lp/fIm=-0.67
|fIm/f21|=0.84
|fIm/f22|=0.87
f23/fIm=-0.74

Figures 12(A) to (C) show various aberration diagrams for the imaging lens of this embodiment. As can be seen from Figures 12(A) to (C), the imaging lens of this embodiment provides good chromatic aberration correction and good flatness of the image plane.

An embodiment of the microscope apparatus according to the present invention will be described below.
A microscope apparatus according to an embodiment of the present invention includes an illumination optical system for illuminating an object, an immersion microscope objective lens disclosed in the first to third embodiments for forming an image of the object, and an imaging lens disclosed in the fourth to sixth embodiments, and an observation system for observing the image.

The illumination optical system in particular uses a near-infrared laser as the light source, and focuses this near-infrared laser light onto the object using a lens. This causes the object to undergo two-photon excitation, emitting visible light of various wavelengths.

Visible light of various wavelengths from an object is focused on an image plane by the immersion microscope objective lens disclosed in the first to third embodiments and the imaging lens disclosed in the fourth to sixth embodiments.

The observation system makes the formed image visible to the observer. A simple observation system has an eyepiece, and the observer observes directly with his or her eyes. In particular, the observation system should use an image sensor such as a CCD, a processing device such as a computer, and a display device such as an LED display. Furthermore, the image may be recorded on a recording medium.

Although the embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various modifications and changes are possible within the scope of the gist of the invention.

G1 and IG1 First lens group G2 and IG2 Second lens group G3 and IG3 Third lens group G4 Fourth lens group G5 Fifth lens group L Lens C1 First cemented surface C2 Second cemented surface C3 First appearing concave surface having negative refractive power C4 Concave surface C5 of cemented meniscus lens in the third lens group with its convex surface facing the object side Concave surface C of cemented meniscus lens in the fifth lens group with its concave surface facing the object side OBJ Object

Claims (7)

A microscope objective lens system comprising a microscope objective lens and an imaging lens on which a parallel light beam from the microscope objective lens is incident,
The imaging lens includes, in order from the object side,
a first lens group including at least one lens having a positive refractive power and one lens having a negative refractive power, on which the parallel light beam is incident;
a second lens group including at least one lens having a positive refractive power;
a third lens group including at least one lens having a positive refractive power and one lens having a negative refractive power, and having a negative refractive power as a whole;
A microscope objective lens system characterized in that, when a distance from a lens surface of the first lens group closest to the object side to a pupil plane is Lp and a focal length of the entire system is fIm, the following condition is satisfied:
-5.0<Lp/fIm<-0.5 the first lens group is a cemented lens of two lenses,
2. The microscope objective lens system according to claim 1, wherein the at least one lens having a positive refractive power in the first lens group has a refractive index of 1.61 or less and an Abbe number of 65 or more. 3. The microscope objective lens system according to claim 1, wherein the following condition is satisfied when the focal length of the first lens group is f21 and the focal length of the second lens group is f22:
0.03<|fIm/f21|<0.85
0.70<|fIm/f22|<2.00 an illumination optical system for illuminating an object;
an immersion microscope objective lens for forming an image of the object and a microscope objective lens system according to any one of claims 1 to 3;
and an observation system for observing the image. an illumination optical system for illuminating an object;
a microscope apparatus including an immersion microscope objective lens and an imaging lens for forming an image of the object,
The imaging lens includes, in order from the object side,
a first lens group including at least one lens having a positive refractive power and one lens having a negative refractive power, and into which a parallel light beam is incident from the object side;
a second lens group including at least one lens having a positive refractive power;
a third lens group including at least one lens having a positive refractive power and one lens having a negative refractive power, and having a negative refractive power as a whole;
A microscope apparatus characterized in that the following condition is satisfied when the distance from the lens surface of the first lens group closest to the object side to the pupil plane is Lp and the focal length of the entire system is fIm:
-5.0<Lp/fIm<-0.5 the first lens group is a cemented lens of two lenses,
6. The microscope apparatus according to claim 5 , wherein the at least one lens having a positive refractive power in the first lens group has a refractive index of 1.61 or less and an Abbe number of 65 or more. 7. The microscope apparatus according to claim 5 , wherein the following condition is satisfied when the focal length of the first lens group is f21 and the focal length of the second lens group is f22:
0.03<|fIm/f21|<0.85
0.70<|fIm/f22|<2.00

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