Immersion microscope objective lens, imaging lens, and microscope device

Abstract

To provide an immersion microscope objective lens and an imaging lens that produce a sharp image across the entire screen from the center to the periphery, and a microscope device including said lens. [Solution] The optical system includes, from the object OBJ side, a first lens group G1 consisting of two or more lenses, a second lens group G2 consisting of seven or more lenses including a triplet lens, a third lens group G3 consisting of two or more lenses, a fourth lens group G4, 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, and the third lens group G3 is provided with a cemented surface C2 with a convex surface facing the object side, or the fifth lens group G5 is provided with a cemented surface C1 with a concave surface facing the object side, and when the maximum image height is Ih and the maximum effective radius of the lens is RDmax, the optical system satisfies the condition (0.35

Description

[Technical Field]

[0001] The present invention relates to a microscope objective lens system. In particular, it relates to an immersion microscope objective lens with a magnification of approximately 10 to 20 times, an infinite immersion microscope objective lens, and a microscope apparatus using this infinite immersion microscope objective lens. It also particularly relates to an imaging lens and a microscope apparatus using this imaging lens. [Background technology]

[0002] Generally, a microscope objective lens system is composed 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 Patent Documents 1 and 2 listed below. Among microscope objective lens systems, imaging lenses are known, for example, as described in Patent Documents 3 and 4 below. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2005-189732 [Patent Document 2] Patent Publication No. 2017-161651 [Patent Document 3] Patent Publication No. 57-195212 [Patent Document 4] Patent Publication No. 2016-75860 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional immersion microscope objective lenses and microscope objective lens systems using imaging lenses provide sharp images in and around the center of the screen, but the images become blurred from the middle to the periphery of the screen.

[0005] The present invention has been made in view of the above points, and has as its object to provide a microscope objective lens system that produces a sharp image over the entire screen from the center to the periphery. [Means for solving the problem]

[0006] In order to achieve the above object, an immersion microscope objective according to a first aspect of the present invention includes, in order from the object OBJ side, a first lens group G1 having an overall positive refractive power and consisting of two or more lenses; a second lens group G2 having an overall positive refractive power, consisting of seven or more lenses including a cemented triplet lens; a third lens group G3 consisting of two or more lenses; a fourth lens group G4 having a negative refractive power; and a fifth lens group G5 consisting of two or more lenses and emitting a parallel light beam, wherein at least one of the third lens group G3 or the fifth lens group G5 is configured with three or more lenses, and 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 satisfies the following condition (1): 0.35 <Ih / RDmax<2.2 (1)

[0007] Furthermore, in order to achieve the above object, an imaging lens according to a second aspect of the present invention includes, in order from the object OBJ side, a first lens group IG1 including at least one lens with positive refractive power and one lens with negative refractive power, a second lens group IG2 including at least one lens with positive refractive power, and a third lens group IG3 including at least one lens with positive refractive power and one lens with negative refractive power and having negative refractive power as a whole, and satisfies the following condition (2) when the distance from the lens surface of the first lens group IG1 closest to the object side to the pupil plane is denoted by Lp and the focal length of the entire system is denoted by fIm: -5.0 <Lp / fIm<-0.5 (2)

[0008] In order 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.

[0009] 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. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an immersion microscope objective lens and an imaging lens that have a high numerical aperture, yet have excellent flatness across the entire wavelength band used, and produce sharp images even in the middle and peripheral parts of the screen, as well as a microscope device that includes the immersion microscope objective lens or the imaging lens. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing an immersion microscope objective lens according to a first embodiment of the present invention. [Figure 2] 5A to 5C are diagrams showing various aberrations in the first example. [Figure 3] FIG. 2 is a diagram showing an immersion microscope objective lens according to a second embodiment of the present invention. [Figure 4] 10A to 10C are diagrams showing various aberrations in the second example. [Figure 5] FIG. 10 is a diagram showing an immersion microscope objective lens according to a third embodiment of the present invention. [Figure 6] 10A to 10C are diagrams showing various aberrations in the third example. [Figure 7] FIG. 10 is a diagram showing an imaging lens according to a fourth embodiment of the present invention. [Figure 8] 10A to 10C are diagrams showing various aberrations in the fourth example. [Figure 9] FIG. 10 is a diagram showing an imaging lens according to a fifth embodiment of the present invention. [Figure 10]10A to 10C are diagrams illustrating various aberrations in the fifth example. [Figure 11] FIG. 10 is a diagram showing an imaging lens according to a sixth embodiment of the present invention. [Figure 12] 13A to 13C are diagrams illustrating various aberrations in the sixth example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Immersion microscope objective lenses and tube lenses, as well as microscope devices having the immersion microscope objective lenses or tube lenses, according to embodiments and examples of the present invention will be described below with reference to the drawings. Note that identical parts in the drawings are designated by the same reference numerals.

[0013] First, the immersion microscope objective lens of the first embodiment will be described. The immersion microscope objective according to the first embodiment is basically an immersion microscope objective 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, at least either the third lens group G3 or the fifth lens group G5 has a lens configuration of three or more lenses, and at least the third lens group G3 has a cemented surface C2 with a convex surface facing the object side, or the fifth lens group G5 has a cemented surface C1 with a concave surface facing the object side, thereby providing excellent correction for the field curvature and chromatic aberration of the immersion microscope objective.

[0014] It should be noted that the immersion microscope objective is a microscope objective in which the space between the object OBJ and the first lens group G1 is filled with liquid.

[0015] Condition (1) particularly defines the preferred size of the objective lens. Below the lower limit of condition (1), the lens diameter becomes too large, making it difficult to fit into an actual device, which is undesirable. Above the upper limit of condition (1), the lens diameter becomes too small, making aberration correction difficult, which is also undesirable. Setting the lower limit to 0.45 provides even better results, and setting it to 0.47 provides very good results.

[0016] The maximum image height is the value obtained by multiplying the maximum object height of the object OBJ 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.

[0017] In particular, in this embodiment, the fifth lens group G5 is configured to emit a parallel light beam, which makes it possible to attach it to a variety of microscopes, increasing the versatility of the immersion microscope objective lens. Furthermore, it is preferable that the fourth lens group G4 be disposed in contact with the third lens group G3, and the fifth lens group G5 be disposed in contact with the fourth lens group G4.

[0018] In the immersion microscope objective lens according to the second embodiment, when a cemented surface provided in the fifth lens group G5 with its concave surface facing the object OBJ is defined as a first cemented surface C1, the refractive power of the first cemented surface C1 is positive, the refractive indices of the media on both sides of the first cemented surface C1 are n6 and n7, respectively, the radius of curvature of the first cemented surface C1 is R1, and the focal length of the entire microscope objective lens system is f, it is preferable that the following condition (3) is satisfied: 0.07 <|(n6-n7)×f / R1 |< 1.2 (3)

[0019] This condition is for effectively correcting chromatic coma in the meridional direction. In this specification, chromatic coma refers to the difference in coma at each wavelength in the visible light range. Exceeding the upper limit of condition (3) is undesirable because it makes the lens shape unfavorable for manufacturing. Falling below the lower limit of condition (3) is also undesirable because it makes it difficult to correct chromatic coma in the meridional direction.

[0020] 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.

[0021] Furthermore, in the immersion microscope objective lens of the fourth embodiment, it is preferable that the meniscus lens with its concave surface facing the first object OBJ side satisfies the following condition (4), where n3 is the refractive index of the meniscus lens with its concave surface facing the first object OBJ side. n3>1.7 (4)

[0022] Condition (4) satisfies the condition for satisfactory correction of spherical aberration and Petzval's sum. If condition (4) is not satisfied, spherical aberration and Petzval's sum cannot be satisfactorily corrected. Setting the lower limit to 1.75 will yield even better results. This meniscus lens element may be a cemented lens element or a single lens element.

[0023] Furthermore, in the immersion microscope objective lens according to the fifth embodiment, it is preferable that the first lens group G1 has a cemented surface with a convex surface facing the object OBJ, and when the refractive index of the medium on the object OBJ side of the cemented 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 following condition (5) is satisfied: n1-n2>0.10 (5)

[0024] Condition (5) satisfies the condition for satisfactorily correcting high-order chromatic spherical aberration. Below the lower limit of condition (5), it becomes difficult to satisfactorily correct high-order chromatic spherical aberration. Setting the lower limit to 0.15 provides even better results.

[0025] Furthermore, in the immersion microscope objective lens according to the sixth embodiment, when a cemented surface provided in the third lens group G3 and having a convex surface facing the object OBJ is defined as a second cemented surface C2, the refractive power of the second cemented surface C2 is positive, the refractive indices of the media on both sides of the second cemented surface C2 are n4 and n5, respectively, the radius of curvature of the second cemented surface C2 is R2, and the focal length of the entire microscope objective lens system is f, it is preferable that the objective lens satisfies the following condition (6): 0.07 <|(n4-n5)×f / R2 |< 1.2 (6)

[0026] Condition (6) satisfies the condition for favorable correction of chromatic coma in the meridional direction. Exceeding the upper limit of condition (6) is undesirable because the lens shape becomes unfavorable in terms of manufacturing. Conversely, falling below the lower limit of condition (6) is undesirable because it becomes difficult to correct chromatic coma in the meridional direction.

[0027] 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 be flat. A concave surface would be prone to trapping air bubbles in actual use, while a convex surface would generate a large amount of spherical aberration, which is undesirable in terms of performance.

[0028] In the immersion microscope objective according to the eighth embodiment, the second lens group G2 preferably includes at least two triplet lenses, which can reduce second-order dispersion.

[0029] Furthermore, it is preferable that the immersion microscope objective lens according to the ninth embodiment satisfies the following condition (7), where R3 is the radius of curvature of the first concave surface C3 having negative refractive power when counting from the object OBJ, and d is the distance from the object OBJ to the first concave surface C3 having negative refractive power. -0.3>d / R3>-1.5 (7)

[0030] Condition (7) is a condition for effectively correcting spherical aberration in particular. Exceeding the upper limit of condition (7) undesirably increases the overall lens length. Conversely, falling below the lower limit of condition (7) undesirably increases spherical aberration.

[0031] Furthermore, it is preferable that the immersion microscope objective according to the tenth embodiment satisfies the following condition (8), where LL is the distance from the object OBJ plane to the final lens surface of the microscope objective and θ is the angle of the chief ray corresponding to the maximum image height emerging from the microscope objective: 0.00063 < tan θ / LL <0.00105 (8)

[0032] Condition (8) satisfies the condition for optimizing the overall size of the lens while maintaining good performance. Exceeding the upper limit of condition (8) undesirably shortens the overall lens length, making it difficult to achieve good performance. Conversely, falling below the lower limit of condition (8) undesirably makes the overall lens length too long, making it impossible to mount the lens on a microscope.

[0033] In the immersion microscope objective 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 triplet of meniscus lenses, even better aberration correction becomes possible.

[0034] Furthermore, it is preferable that the immersion microscope objective lens of the twelfth embodiment satisfies the following condition (9), where R4 is the radius of curvature of the concave surface C4 of the cemented meniscus lens of the third lens group G3 with its convex surface facing the object side: 0.35 <|R4| / f <2 (9)

[0035] Condition (9) is a condition for maintaining good flatness. It is also a condition for providing concave surface C4 with large refractive power. Exceeding the upper limit of condition (9) undesirably shortens the overall lens length, making it difficult to obtain good performance. Conversely, falling below the lower limit of condition (9) undesirably makes the overall lens length too long, making it impossible to install in a microscope.

[0036] 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 its concave surface facing the object OBJ. In particular, if the cemented meniscus lens is a three-lens cemented meniscus lens, even better aberration correction becomes possible.

[0037] Furthermore, it is preferable that the immersion microscope objective lens of the 14th embodiment satisfies the following condition (10), 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. 0.4 <|R5| / f<2.5 (10)

[0038] Condition (10) satisfies the condition for maintaining good flatness of the image plane. It also satisfies the condition for providing large refractive power to concave surface C5. Exceeding the upper limit of condition (10) undesirably shortens the overall lens length, making it difficult to obtain good performance. Conversely, falling below the lower limit of condition (10) undesirably makes the overall lens length too long, making it difficult to install in a microscope.

[0039] Furthermore, it is preferable that the immersion microscope objective according to the fifteenth embodiment satisfies the following condition (11), where f4 is the focal length of the fourth lens group G4: 0.5 < |f4| / f < 2 (11)

[0040] Condition (11) sets forth the appropriate refractive power of the fourth lens group. Exceeding the upper limit of condition (11) undesirably shortens the overall lens length, making it difficult to obtain good performance. Conversely, falling below the lower limit of condition (11) undesirably lengthens the overall lens length, making it difficult to mount the lens on a microscope.

[0041] Furthermore, in the immersion microscope objective lens according to the sixteenth 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 in the third lens group G3 with its convex surface facing the object OBJ side is t3, and the thickness of the cemented meniscus lens in 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) be satisfied: d3 / t3 <0.75 (12) d4 / t5 <0.35 (13)

[0042] Conditions (12) and (13) set forth appropriate shapes for the third and fifth lens groups. Exceeding the upper limits of conditions (12) and (13) is undesirable, as it makes it difficult to correct coma.

[0043] 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, with the first lens group IG1 mainly correcting chromatic aberration, and the second lens group IG2 correcting spherical aberration, coma, astigmatism, distortion, etc., the field curvature and chromatic aberration of the imaging lens can be effectively corrected.

[0044] Condition (2) defines the appropriate positional state for the imaging lens. If the upper limit of condition (2) is exceeded, the overall dimensions of the microscope apparatus 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 becomes too close, which limits the applications of the target object that can be used, making the imaging lens less versatile, which is undesirable.

[0045] In the imaging lens according to the eighteenth embodiment, the first lens group IG1 is a cemented two-lens 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. With this configuration, it becomes possible to effectively correct chromatic aberration in particular.

[0046] Furthermore, it is preferable that the imaging lens according to the 19th embodiment satisfies the following conditions (14) and (15), when the focal length of the first lens group IG1 is f21 and the focal length of the second lens group IG2 is f22: 0.03<|fIm / f21|<0.85 (14) 0.70<|fIm / f22|<2.00 (15)

[0047] 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 strong, resulting in performance comparable to that of a conventional imaging lens, which is undesirable. Furthermore, if the upper limit of condition (14) is exceeded, the refractive power of the first lens group IG1 becomes too weak, which makes it unable to contribute to aberration correction, which is undesirable.

[0048] If the lower limit of condition (15) is exceeded, the refractive power of the second lens group IG2 becomes too strong, and the refractive power of the first lens group IG1 becomes too weak, undesirably worsening various aberrations. Also, if the upper limit of condition (15) is exceeded, the refractive power of the second lens group IG2 becomes too weak, and the refractive power of the first lens group IG1 becomes too strong, undesirably resulting in the same aberration correction state as in conventional imaging lenses.

[0049] Furthermore, it is preferable that the imaging lens according to the twentieth embodiment satisfies the following condition (16), where the focal length of the third lens group IG3 is f23: -2.0 <f23 / fIm<-0.5 (16)

[0050] Condition (16) is a condition for defining an appropriate refractive power arrangement. Exceeding the upper and lower limits of condition (16) is undesirable because it becomes impossible to perform favorable correction of each aberration.

[0051] 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.

[0052] The microscope apparatus according to the 22nd 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 17th to 20th embodiments, and an observation system for observing the image. [Example]

[0053] First, first, second and third examples will be described with reference to Figures 1 to 6. These examples are examples of immersion microscope objective lenses.

[0054] 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, vd=57.9), and the distance is 3 mm.

[0055] (First Example) 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.

[0056] 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.

[0057] 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.

[0058] 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 its concave surface facing the object side.

[0059] 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.

[0060] The immersion microscope objective lens of this embodiment has a focal length of 12.4 mm, a magnification of 16x, an object-side NA of 0.8, a maximum object height of 0.75 mm, and a maximum image height Ih of 12.00 mm.

[0061] Table 1 below shows the data for this example. Starting from the left, the table lists the surface number, radius of curvature (r), surface spacing (d), refractive index at a wavelength of 588 nm (nd), and Abbe number (νd). The unit of "mm" is generally used for the radius of curvature r, surface spacing d, and other lengths. However, because optical systems can achieve the same optical performance even when proportionally enlarged or reduced, the unit is not limited to "mm." This display method is also used for Tables 2 to 6, which will be described later. [Table 1]

[0062] The condition values ​​for 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

[0063] 2(A) to (C) are diagrams showing various aberrations of the immersion microscope objective lens of this example, with Fig. 2(A) showing spherical aberration, Fig. 2(B) showing astigmatism, and Fig. 2(C) showing distortion. An imaging lens is required to create these aberration diagrams, and Examples 1 to 3 use an ideal imaging lens with a focal length of 200 mm that is free of aberrations.

[0064] In the spherical aberration diagram in Figure 2(A), the vertical axis represents the relative incident height, and the horizontal axis represents the amount of aberration. g represents the g-line with a wavelength of 436 nm, F represents the F-line with a wavelength of 486 nm, d represents the d-line with a wavelength of 588 nm, and C represents the C-line with a wavelength of 656 nm.

[0065] 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.

[0066] In an astigmatism diagram, the vertical axis represents the object height or the 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).

[0067] In addition, 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 represents the object height, and 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 represents the incident angle.

[0068] In the distortion diagram, the vertical axis indicates the object height or the angle of incidence, and the horizontal axis indicates the amount of distortion expressed as a percentage.

[0069] The distortion diagrams are displayed in such a way that the vertical axis represents the object height in FIG. 2(C) of the present embodiment, FIG. 4(C) of the second embodiment, and FIG. 6(C) of the third embodiment, and the vertical axis represents the angle of incidence in FIG. 8(C) of the fourth embodiment, FIG. 10(C) of the fifth embodiment, and FIG. 12(C) of the sixth embodiment.

[0070] As can be seen from FIGS. 2(A) to 2(C), the immersion microscope objective of this embodiment provides good correction of chromatic aberration and good flatness of the image plane.

[0071] (Second Example) The immersion microscope objective lens of the second embodiment will be described with reference to Figure 3 and Figures 4(A) to (C) Figure 3 is a diagram showing the immersion microscope objective lens of the second embodiment according to the present invention.

[0072] 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.

[0073] 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 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 OBJ side, a biconvex lens L27 and a biconcave lens L28.

[0074] The third lens group G3 is composed of a cemented lens consisting 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.

[0075] The immersion microscope objective lens of this embodiment has a focal length f of 12.1 mm, a magnification of 16.5, an object-side NA of 0.8, a maximum object height of 0.75 mm, and a maximum image height Ih of 12.38 mm.

[0076] Table 2 below shows the data for this example. [Table 2]

[0077] The condition values ​​for 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

[0078] Figures 4(A) to 4(C) show various aberration diagrams for the immersion microscope objective lens of this Example. As can be seen from Figures 4(A) to 4(C), the immersion microscope objective lens of this Example provides good correction of chromatic aberration and good flatness of the image plane.

[0079] (Third Example) The immersion microscope objective lens of the third embodiment will be described with reference to Figure 5 and Figures 6(A) to (C). Figure 5 is a diagram showing the immersion microscope objective lens of the third embodiment according to the present invention.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] The immersion microscope objective lens of this embodiment has a focal length f of 12.5 mm, a magnification of 16x, an object-side NA of 0.8, a maximum object height of 0.75 mm, and a maximum image height Ih of 12.00 mm.

[0084] Table 3 below shows the data for this example. [Table 3]

[0085] The condition values ​​for 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

[0086] Figures 6(A) to 6(C) show various aberration diagrams for the immersion microscope objective lens of this embodiment. As can be seen from Figures 6(A) to 6(C), the immersion microscope objective lens of this embodiment provides excellent correction of chromatic aberration and also provides excellent flatness of the image plane.

[0087] Fourth, fifth and sixth examples will be described below with reference to Figures 7 to 12. These examples are examples of imaging lenses. 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.

[0088] (Fourth Example) The imaging lens of the fourth embodiment will be described with reference to Figure 7 and Figures 8(A) to (C). Figure 7 is a diagram showing the imaging lens of the fourth embodiment according to the present invention.

[0089] The first lens group IG1 is composed of a cemented lens consisting of a biconvex lens L1 and a biconcave lens L2. The second lens group IG2 is composed of a positive meniscus lens L3 with its convex surface facing the object side. The third lens group IG3 is composed of a cemented lens consisting of a biconvex lens L4 and a biconcave lens L5.

[0090] The focal length fIm of the imaging lens in this example 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 incident angle is 3 degrees.

[0091] Table 4 below shows the data for this example. [Table 4]

[0092] The condition values ​​for this embodiment are shown below. Lp / fIm=-0.5 |fIm / f21|=0.68 |fIm / f22|=0.96 f23 / fIm=-1.22 8(A) to 8(C) show various aberration diagrams of the imaging lens of this embodiment. As can be seen from Fig. 8(A) to 8(C), the imaging lens of this embodiment provides good correction of chromatic aberration and good flatness of the image plane.

[0093] (Fifth Example) The imaging lens of the fifth embodiment will be described with reference to Figure 9 and Figures 10(A) to (C). Figure 9 is a diagram showing the imaging lens of the fifth embodiment according to the present invention.

[0094] The first lens group IG1 is composed of a cemented lens consisting of a biconvex lens L1 and a biconcave lens L2. The second lens group IG2 is composed of a positive meniscus lens L3 with its convex surface facing the object side. The third lens group IG3 is composed of a cemented lens consisting of a biconvex lens L4 and a biconcave lens L5.

[0095] The focal length fIm of the imaging lens in this example 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 incident angle is 3 degrees.

[0096] Table 5 below shows the data for this example. [Table 5]

[0097] The condition values ​​for this embodiment are shown below. Lp / fIm=-0.25 |fIm / f21|=0.70 |fIm / f22|=0.88 f23 / fIm=-1.07

[0098] 10A to 10C are diagrams showing various aberrations of the imaging lens of this embodiment. As can be seen from Fig. 10A to 10C, the imaging lens of this embodiment provides good correction of chromatic aberration and good flatness of the image plane.

[0099] (Sixth Example) The imaging lens of the sixth embodiment will be described with reference to Figure 11 and Figures 12(A) to (C). Figure 11 is a diagram showing the imaging lens of the sixth embodiment according to the present invention.

[0100] 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 its convex surface facing the object side.

[0101] The third lens group IG3 is composed of a cemented lens consisting of a positive meniscus lens L4 with a convex surface facing the object side and a negative meniscus lens L5 with a convex surface facing the object side. The focal length fIm of the imaging lens of this embodiment is 180 mm. The distance Lp from the lens surface closest to the object to the pupil plane is −120 mm, the pupil diameter is 18 mm, and the maximum incident angle is 4 degrees.

[0102] Table 6 below shows the data for this example. [Table 6]

[0103] The condition values ​​for this embodiment are shown below. Lp / fIm=-0.67 |fIm / f21|=0.84 |fIm / f22|=0.87 f23 / fIm=-0.74

[0104] 12(A) to 12(C) show various aberration diagrams of the imaging lens of this embodiment. As can be seen from Fig. 12(A) to 12(C), the imaging lens of this embodiment provides good correction of chromatic aberration and good flatness of the image plane.

[0105] 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 and an imaging lens disclosed in the fourth to sixth embodiments for forming an image of the object, and an observation system for observing the image.

[0106] The illumination optical system uses a near-infrared laser as a light source, and focuses this near-infrared laser light onto the object using a lens, causing the object to undergo two-photon excitation and emit visible light of various wavelengths.

[0107] Visible light of various wavelengths from an object is imaged onto the 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.

[0108] The observation system makes the formed image visible to the observer. A simple observation system has an eyepiece, which the observer observes directly with their eyes. The observation system preferably uses 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.

[0109] 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 present invention. [Explanation of symbols]

[0110] G1 and IG1 First lens group G2 and IG2 second lens group G3 and IG3 third lens group G4 4th lens group G5 5th lens group L Lens C1 First bonding surface C2 Second bonding surface C3 First concave surface with negative refractive power C4: Concave surface of cemented meniscus lens with the convex surface facing the object side in the third lens group C5: Concave surface of cemented meniscus lens with the concave surface facing the object side in the fifth lens group OBJ object

Claims

1. 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

2. 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. 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

4. 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.

5. 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

6. 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. 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

Images