JP2007121338A - Immersion objective lens system for microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apochromat immersion objective lens system for microscope which has a large numerical aperture NA exceeding 1.46 without using special oil or a special cover glass plate as well as favorably corrected spherical aberration and chromatic aberration. <P>SOLUTION: The apochromat immersion objective lens system for microscope which consists, in order from the object side, of a first lens unit composed of a cemented lens component consisting of a plano-convex lens element having a planar surface on the object side and a meniscus lens element having a concave surface on the object side, a second lens unit composed of a lens component or two lens components, a third lens unit comprising at least two cemented lens components, a fourth lens unit composed of a negative lens component having a strongly concave surface on the image side and a fifth lens unit comprising a meniscus lens component having a concave surface on the object side, and satisfies a condition (1) of 0.9≤¾f12/f¾≤1.3, where f12 is the composite focal length of the first lens unit and second lens unit and (f) is the focal length of the whole objective lens system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

    The present invention relates to a microscope objective lens, and more particularly to an immersion microscope objective lens having a high numerical aperture such that NA exceeds 1.46 and having apochromatic performance.

    In recent years, in the field of biology, movement and activity in living cells have been observed using total internal reflection fluorescence microscopy (hereinafter referred to as TIRFM). In the case of observation with this TIRFM, since it is necessary to totally reflect the illumination light at the boundary surface between the cover glass and the sample, an objective lens having a large numerical aperture (NA) that can be totally reflected on the biological sample surface Need to use.

    Furthermore, in order to perform observation with little background noise by the observation method, there is a demand for reducing the depth of evanescent light penetration.

    In order to satisfy such a requirement, it is desired to increase the NA of the objective lens, and an objective lens having an NA exceeding 1.4 is desired.

An objective lens described in the following document is known as a conventional example of such an objective lens having a numerical aperture NA exceeding 1.4.
Japanese Patent No. 3457992 (Japanese Patent Laid-Open No. 7-281097) JP 2002-098903 A JP 2002-350734 A JP 2003-021786 A JP 2003-233012 A JP-T-2004-522185 (priority claim number DE10108796) Among the objective lenses described in these documents, the objective lenses described in Patent Documents 1 and 5 are oil having a refractive index nd of 1.78035 and a refractive index nd of 1. A 7865 cover glass is used, the magnification is 100 ×, and the numerical aperture NA is 1.65.

    The objective lens described in Patent Document 2 uses oil having a refractive index nd of 1.80711 and a cover glass having a refractive index nd of 1.804, a magnification of 100 ×, and a numerical aperture NA of 1. It is an objective lens of 65 to 0.67.

    The objective lens described in Patent Document 3 has an objective lens with a magnification of 60 × and a numerical aperture NA of 1.45 and an objective lens with a magnification of 100 × and a numerical aperture NA of 1.45 to 1.46.

    The objective lenses described in Patent Documents 4 and 6 have a magnification of 100 × and a numerical aperture NA of 1.45.

    Furthermore, the objective lens described in Patent Document 7 is an objective lens having a magnification of 55.9 × or 59.6 × and a numerical aperture NA of 1.4.

    As described above, all of the conventional objective lenses described in Patent Documents 1, 2, and 5 use special oil or cover glass having a high refractive index.

    Such special oils and cover glasses have problems in terms of availability, price, and usability.

    Further, the conventional objective lens described in Patent Document 3.4.6 has a numerical aperture NA of 1.46 at the maximum, and cannot be said to be sufficiently large.

    Furthermore, the objective lens described in Patent Document 7 has an observation NA of 1.4, and even an NA that can be used for illumination light is 1.46, which is not a sufficiently large NA.

    Thus, none of the conventional examples of the above documents satisfy the above requirements.

    The present invention has been made to solve the above problems, and has a high numerical aperture NA exceeding 1.46 without using special oil or cover glass, and has good spherical aberration and chromatic aberration. A corrected apochromat immersion microscope objective lens is provided.

    The microscope objective lens according to the present invention includes, in order from the object side, a first lens group including a cemented lens in which a plano-convex lens having a plane facing the object side and a meniscus lens having a concave surface facing the object side are joined, and one or two lenses A second lens group including a single lens, a third lens group including at least two cemented lenses, a fourth lens group including a negative lens having a strong concave surface facing the image side, and a meniscus having a concave surface facing the object side The fifth lens group including the lens satisfies the following condition (1).

(1) 0.9 ≦ | f12 / f | ≦ 1.3
Here, f12 is a combined focal length of the first lens group and the second lens group, and f is a focal length of the entire objective lens system.

    The objective lens of the present invention has the lens configuration as described above, and further satisfies the conditions (2) and (3) in addition to the condition (1).

(2) 0.7 ≦ | R12 / R13 | ≦ 1.4
(3) 0.7 ≦ | R12 / f | ≦ 1.3
Here, R12 is the radius of curvature of the cemented surface of the first lens group, and R13 is the radius of curvature of the image side surface of the first lens group.

    In the objective lens of the present invention, the first lens group is constituted by a cemented lens in which a plano-convex lens and a meniscus lens having a concave surface facing the object side are cemented, and the cemented surface is a surface with the concave surface facing the object side. The Betzbar sum was corrected by the negative refractive power of.

    In addition, since the objective lens of the present invention has a high NA, the convex surface on the image side of the first lens group is a hemisphere or a spherical surface that slightly exceeds the hemisphere, so that the curvature of the convex surface is a floating condition (aplanatic condition). Thus, the occurrence of spherical aberration and coma is suppressed.

    The second lens group has a positive refractive power and guides the light beam to the third lens group with a small divergence. Therefore, this second lens group needs to have one or two positive single lenses. These single lenses are desirably meniscus lenses having a concave surface facing the object side, planoconvex lenses having a plane on the object side, or biconvex lenses.

    The third lens group includes at least two cemented lenses so as to correct spherical aberration and chromatic aberration. As in the objective lens of the present invention, an apochromatic objective lens having a high NA is more preferable if a three-piece cemented lens is used for the third lens group.

    The fourth lens group is composed of a negative lens component with a strong concave surface facing the image side. This negative lens component has a strong negative refractive power, and thereby corrects Petzval sum and can also correct spherical aberration and coma well. The negative lens component is desirably a cemented lens in which a positive lens and a negative lens are cemented in order to further correct chromatic aberration.

    Further, the fifth lens group includes a meniscus lens component having a concave surface facing the object side.

    This fifth lens group is based on the negative refractive power of the concave surface on the object side. The Petzval sum is corrected well, and various aberrations are corrected well. The meniscus lens component included in the fifth lens group has a function of adjusting the height and angle of the light beam emitted from the objective lens. Furthermore, it is desirable to use a meniscus lens component as a cemented lens in which a positive lens and a negative lens are cemented, because chromatic aberration of magnification can be corrected.

    Further, the microscope objective lens of the present invention satisfies the above condition (1) in order to obtain a high numerical aperture with NA exceeding 1.46.

    This condition (1) defines the combined focal length f12 of the first lens group and the second lens group. This condition (1) is satisfied in order to make the positive refractive power of the first lens group and the second lens group stronger than those of the conventional objective lens. As the beam height increases, spherical aberration and axial chromatic aberration increase. For this reason, the objective lens of the present invention is a light beam that increases the refractive power of the first lens group and the second lens group, suppresses the height of the light beam incident on the third lens group, and has an NA exceeding 1.46. Even so, spherical aberration and axial chromatic aberration can be corrected well.

    When the value of | f12 / f | is smaller than the lower limit value 0.9 of the condition (1), the power of the first lens group and the second lens group becomes too strong, and the height of the light rays incident on the third lens group Becomes lower. In this case, there is no room for raising and lowering the light beam for the purpose of correcting the curvature of field after the third lens group, and it becomes difficult to correct the curvature of field to a substantially preferable range.

    On the other hand, when the value of | f12 / f | exceeds the upper limit of 1.3 of the condition (1), the height of the light incident on the third lens group increases. In that case, it becomes impossible to satisfactorily correct the spherical aberration and the on-axis aberration of a light beam having an NA exceeding 1.46.

    The objective lenses described in Documents 1 to 7 all have a value of | f12 / f | exceeding 1.4.

    Next, in the microscope objective lens of the present invention, it is desirable to satisfy the conditions (2) and (3) in addition to the condition (1) for the following reason.

    Condition (2) defines the ratio between the radius of curvature of the cemented surface of the cemented lens of the first lens group and the radius of curvature of the image-side surface, which is necessary for capturing light having a large NA. This is a necessary condition for obtaining a practical working distance.

    When the value of | R12 / R13 | is smaller than the lower limit of 0.7 of the condition (2), the curvature of the joint surface becomes tight, and as a result, the effective diameter of the first surface cannot be secured, and NA Large rays cannot be captured.

    If the value of | R12 / R13 | exceeds the upper limit of 1.4, the curvature of the convex surface on the image side of the cemented lens becomes tight. As a result, in order to satisfy the floating condition, the working distance of the objective lens has to be extremely shortened, and it becomes difficult to obtain a practical working distance.

    Condition (3) defines a ratio | R12 / f | between the curvature radius R12 of the cemented surface of the first lens group and the focal length f of the entire objective lens system, and corrects various aberrations in a well-balanced manner. It is a condition for.

    In this condition (3), if the value of | R12 / f | is smaller than the lower limit of 0.7, the curvature of the joint surface becomes tight and the spherical aberration and coma aberration deteriorate. On the other hand, if the value of | R12 / f | exceeds the upper limit of 1.3, the curvature of the joint surface becomes loose, the Petzval sum correction amount is insufficient, and the curvature of field deteriorates.

    In the present invention, even if standard oil or cover glass is used without using special oil or cover glass, various aberrations such as spherical aberration and chromatic aberration are excellent with NA having a high numerical aperture exceeding 1.46. This has the effect of realizing a corrected high numerical aperture apochromatic immersion microscope objective lens.

    Next, an embodiment of the present invention will be described based on each example.

The immersion microscope objective lens according to Example 1 of the present invention is configured as shown in FIG. 1 and is a lens system having the following data.

Magnification 60x, NA 1.48, 22 fields of view, WD 0.15
R12 = r ₂ = -2.6547
R13 = r ₃ = -2.5373
f = 3
f12 = 3.03
f1 = 3.65
f2 = 17.27
f3 = 15.39
f4 = −32.62
f5 = −49.87
| F12 / f | = 1.01 Condition (1)
| R12 / R13 | = | r 2 / r 3 | = 1.05 Condition (2)
| R12 / f | = | r 2 /f|=0.88 conditions (3)

Number r d nd νd
1 INF 0.8000 1.51633 64.14 L1
2 -2.6547 2.4984 1.88300 40.76 L2
3 -2.5373 0.1000
4 47.6732 1.8000 1.88300 40.76 L3
5 -22.0319 0.2000
6 12.2714 5.9531 1.49700 81.54 L4
7 -7.0761 1.0000 1.73800 32.26 L5
8 21.2676 5.4885 1.43875 94.93 L6
9 -8.8207 0.2000
10 21.2722 1.0000 1.61336 44.49 L7
11 12.9696 5.7718 1.43875 94.93 L8
12 -7.3922 1.0000 1.77250 49.60 L9
13 -29.9163 0.2000
14 15.5341 3.1803 1.43875 94.93 L10
15 -28.1567 0.6000
16 9.2626 4.7832 1.60300 65.44 L11
17 -9.5374 1.0000 1.67300 38.15 L12
18 5.7707 4.6044
19 -5.2804 5.1425 1.60300 65.44 L13
20 14.9668 3.2178 1.71736 29.52 L14
21 -13.3762

Note that “number” in the data is a number assigned in order from the object side (sample side) in the lens system, and r, d, nd, and νd are curvature radii, surface spacing (lens thickness and air spacing), d. The refractive index of the line and the Abbe number in the d line are all described in order from the object side.

Therefore, numbers 1, 2, ... of r, d, ... the surface r ₁ in each Figure, r _2, stations radii at ..., d _1, d _2, the surface separation in ... Nd and νd denote the refractive indexes of the corresponding lenses.

As shown in FIG. 1, the first embodiment of the present invention includes 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. The lens group G1 includes cemented lenses L1 and L2 (r _{1 to} r ₃ ) having a cemented surface r ₂ with a concave surface facing the object side, and the second lens group G2 includes one positive lens L3 (r _{4 to} r ₅₎ consists, have a positive refractive power as a third lens group G3 whole, convex irregularities of cemented triplet _{L4, L5, L6 (r 6} ~r 9) and uneven concave cemented triplet L7, L8, L9 consists (r ₁₀ ~r ₁₃₎ two three-element cemented lens and the positive lens L10 (r ₁₄ ~r ₁₅₎ of the fourth lens group G4 has a positive refractive power as a whole, the image side a cemented meniscus lens L11 with a concave surface facing, L12 made (r ₁₆ ~r _18), the fifth lens group as a whole Has a negative power, cemented meniscus lens L13 having a concave surface on the object side, consisting of L14 (r ₁₉ ~r _21).

    The objective lens of Example 1 satisfies the conditions (1), (2), and (3) as shown in the data.

The second embodiment of the present invention has a configuration as shown in FIG. 2 and has the following data.

Magnification 60x, NA 1.48, 22 fields of view, WD 0.15
R12 = r ₂ = -3.0948
R13 = r ₃ = -2.6321
f = 3
f12 = 3.24
f1 = 3.92
f2 = 15.7
f3 = 15.15
f4 = −27.7
f5 = −63.69
| F12 / f | = 1.08 Condition (1)
| R12 / R13 | = | r 2 / r 3 | = 1.18 Condition (2)
| R12 / f | = | r 2 /f|=1.03 conditions (3)

Number r d nd νd
1 INF 0.8000 1.51633 64.14 L1
2 -3.0948 2.6875 1.80400 46.57 L2
3 -2.6321 0.1000
4 INF 1.8000 1.75500 52.32 L3
5 -11.8564 0.2000
6 14.6612 5.8013 1.49700 81.54 L4
7 -6.8647 1.0000 1.67300 38.15 L5
8 63.6424 5.4381 1.43875 94.93 L6
9 -9.5708 0.2000
10 20.1407 1.0000 1.61336 44.49 L7
11 10.7554 6.5836 1.43875 94.93 L8
12 -6.9608 1.0000 1.63775 42.41 L9
13 -38.7752 0.2000
14 16.7280 1.6894 1.43875 94.93 L10
15 -120.5347 0.6000
16 9.7467 4.6630 1.60300 65.44 L11
17 -8.0837 1.0000 1.67300 38.15 L12
18 5.8307 4.6577
19 -5.2834 5.8611 1.60300 65.44 L13
20 16.6902 2.9042 1.73800 32.26 L14
21 -13.4830

As shown in FIG. 2, the objective lens according to Example 2 of the present invention, in order from the object side, includes a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4. And five lens groups of the fifth lens group G5.

The first lens group G1 has plano-convex cemented lenses L1 and L2 (r _{1 to} r ₃ ) having a positive refractive power as a whole and having a cemented surface r ₂ with a concave surface facing the object side. The lens group G2 is composed of one positive lens L3 (r _{4 to} r ₅ ), and the third lens group G3 has a positive power as a whole, and has three convex cemented lenses L4, L5, L6 (r _{6 to} r ₉ ), a concave-convex three-piece cemented lens L 7, L 8, L 9 (r _{10 to} r ₁₃ ) and a positive lens L 10 (r _{14 to} r ₁₅ ). The fourth lens group G 4 is negative as a whole. of having a refractive power, a cemented meniscus lens L11 with a concave surface facing the image _{side, L12 (r 16 ~r 18)} , the fifth lens group G5 has a negative power as a whole, a concave surface on the object side towards the cemented meniscus lens L13, made of L14 (r ₁₉ ~r _21).

This Example 2 also satisfies the conditions (1), (2), and (3) as shown in the data.

The objective lens of Example 3 of the present invention has a lens configuration as shown in FIG. 3 and is a lens system having the following data.

Magnification 60x, NA 1.48, 22 fields of view, WD 0.15
R12 = r ₂ = -3.0558
R13 = r ₃ = -2.8215
f = 3
f12 = 3.72
f1 = 4.34
f2 = 13.45
f3 = 25.95
f4 = −128.53
f5 = -44.9
| F12 / f | = 1.24 Condition (1)
| R12 / R13 | = | r 2 / r 3 | = 1.08 Condition (2)
| R12 / f | = | r 2 /f|=1.02 conditions (3)

Number r d nd νd
1 INF 0.7000 1.51633 64.14 L1
2 -3.0558 3.1300 1.77250 49.60 L2
3 -2.8215 0.1400
4 -14.6318 1.9000 1.56907 71.30 L3
5 -7.3349 0.2000
6 31.2166 4.2475 1.43875 94.93 L4
7 -21.9219 0.1000
8 10.8530 6.3968 1.43875 94.93 L5
9 -14.8866 1.0000 1.67300 38.15 L6
10 12.3589 3.1351 1.43875 94.99 L7
11 -46.6847 0.3000
12 18.3790 1.0000 1.63775 42.41 L8
13 7.1356 5.9316 1.43875 94.99 L9
14 -24.7148 0.2000
15 INF 1.1000 1.67300 38.15 L10
16 12.6163 3.2446 1.43875 94.99 L11
17 -18.7213 0.2000
18 9.0969 5.1442 1.43875 94.99 L12
19 -101.6701 1.0000 1.61336 44.49 L13
20 8.9722 4.0950
21 -4.7658 2.7900 1.60300 65.44 L14
22 13.7835 2.8326 1.73800 32.26 L15
23 -11.2491

In other words, the third exemplary embodiment includes, in order from the object side, the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5. Yes.

The first lens group G1 includes plano-convex cemented lenses L1 and L2 (r _{1 to} r ₃ ) having cemented surfaces (r ₂ ) with a concave surface facing the object side, and the second lens group G2 includes two lenses. the positive lens _{L3, L4 (r 4 ~r 5} , r 6 ~r 7) consists, third lens group G3 has a positive refractive power as a whole, three convex irregularities cemented lens L5, L6 consists of L7 (r ₈ ~r ₁₁₎ and unevenness of the cemented lens _{L8, L9 (r 12 ~r 14} ) and unevenness of the cemented lens _{L10, L11 (r 15 ~r 17} ), the fourth lens group G4, whole as has negative refractive power, a cemented meniscus lens L12 with a concave surface facing the image _{side, L13 (r 18 ~r 20)} , the fifth lens group G5 has a negative refractive power as a whole, the object side And cemented meniscus lenses L14 and L15 (r _{21 to} r ₂₃ ) having a concave surface directed to each other.

    This Example 3 also satisfies the conditions (1), (2), and (3) as shown in the data.

The objective lens of Example 4 of the present invention has the lens configuration as shown in FIG. 4 and has the following data.

Magnification 60x, NA 1.48, 22 fields of view, WD 0.15
R12 = r ₂ = -2.3456
R13 = r ₃ = -2.407
f = 3
f12 = 2.8
f1 = 3.5
f2 = 14.33
f3 = 15.73
f4 = −39.64
f5 = −36.9
| F12 / f | = 0.93 Condition (1)
| R12 / R13 | = | r 2 / r 3 | = 0.97 Condition (2)
| R12 / f | = | r 2 /f|=0.78 conditions (3)

Number r d nd νd
1 INF 0.6800 1.51633 64.14 L1
2 -2.3456 2.4611 1.88300 40.76 L2
3 -2.4070 0.1000
4 26.7849 1.8000 1.88300 40.76 L3
5 -23.2348 0.2000
6 18.8405 5.7745 1.49700 81.54 L4
7 -5.7635 1.0000 1.73800 32.26 L5
8 44.2904 5.4936 1.43875 94.93 L6
9 -8.1486 0.2000
10 33.5309 1.0000 1.61336 44.49 L7
11 13.6060 5.7494 1.43875 94.93 L8
12 -7.6815 1.0000 1.77250 49.60 L9
13 -24.1850 0.2000
14 14.7280 3.1664 1.43875 94.93 L10
15 -30.1450 0.6000
16 8.2907 4.7445 1.60300 65.44 L11
17 -12.0370 1.0000 1.67300 38.15 L12
18 5.3610 4.3186
19 -4.8977 5.8879 1.60300 65.44 L13
20 16.9759 3.1640 1.72825 28.46 L14
21 -14.1543

As shown in the drawing, the objective lens of Example 4 includes 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. It is configured.

The first lens group G1 includes plano-convex cemented lenses L1 and L2 (r _{1 to} r ₃ ) having a cemented surface (r ₂ ) with a concave surface facing the object side, and the second lens group G2 includes one positive lens. The third lens group G3 is composed of lenses L3 (r _{4 to} r ₅ ), and has a positive refracting power as a whole, and has three convex cemented lenses L4, L5, and L6 (r _{6 to} r ₉ ). uneven concave cemented triplet _{L7, L8, L9 (r 10} ~r 13) and becomes a positive lens L10 (r ₁₄ ~r _15), the fourth lens group G4 is a lens group having a negative refractive power as a whole in, a cemented meniscus lens L11, L12 having a concave surface facing the image side (r ₁₆ ~r _18), the fifth lens group G5 is a lens group having negative refractive power as a whole, a concave surface on the object side cemented meniscus lens L13 having a becomes more and L14 (r ₁₉ ~r _21).
The objective lens of Example 4 also satisfies the conditions (1), (2), and (3) as shown in the above data.

The objective lens of Example 5 of the present invention has a lens configuration as shown in FIG. 5 and is a lens system having the following data.

Magnification 60x, NA 1.48, 22 fields of view, WD 0.15
R12 = r ₂ = -3.5871
R13 = r ₃ = -2.6944
f = 3
f12 = 3.02
f1 = 3.68
f2 = 17.08
f3 = 13.97
f4 = −22.99
f5 = −45.58
| F12 / f | = 1.01 Condition (1)
| R12 / R13 | = | r 2 / r 3 | = 1.33 Condition (2)
| R12 / f | = | r 2 /f|=1.2 conditions (3)

Number r d nd νd

1 INF 0.8000 1.51633 64.14 L1
2 -3.5871 2.5787 1.88300 40.76 L2
3 -2.6944 0.1000
4 21.7926 1.8000 1.88300 40.76 L3
5 -47.1096 0.2000
6 15.9174 5.8105 1.49700 81.54 L4
7 -7.0662 1.0000 1.73800 32.26 L5
8 21.9651 5.5975 1.43875 94.93 L6
9 -9.0082 0.2000
10 17.1629 1.0000 1.61336 44.49 L7
11 14.1749 6.3342 1.43875 94.93 L8
12 -7.7450 1.0000 1.77250 49.60 L9
13 -24.4287 0.2000
14 13.0557 3.7780 1.43875 94.93 L10
15 -57.8878 0.6000
16 8.7883 4.4483 1.60300 65.44 L11
17 -12.4876 1.0000 1.67300 38.15 L12
18 4.8256 3.4411
19 -5.3141 5.1244 1.60300 65.44 L13
20 18.2004 1.8273 1.76182 26.52 L14
21 -32.7452 0.2000
22 68.0322 2.0000 1.71736 29.52 L15
23 -37.0389

As shown in FIG. 5, the objective lens of Example 5 includes the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the first lens group in order from the object side. 5 lens group G5.

The first lens group G1 includes plano-convex cemented lenses L1 and L2 (r _{1 to} r ₃ ) having cemented surfaces (r ₂ ) with a concave surface facing the object side, and the second lens group G2 is a single lens. The third lens group G3 includes a positive lens L3 (r _{4 to} r ₅ ), and has a positive refractive power as a whole. The third lens group G3 includes convex and concave three-piece cemented lenses L4, L5, and L6 (r _{6 to} r ₉₎ an irregular concave cemented triplet L7, L8, L9 and more becomes (r ₁₀ ~r ₁₃₎ and the positive lens L10 (r ₁₄ ~r _15), the fourth lens group G4 is negative refractive power as a whole a lens group having made a cemented meniscus lens L11 having a concave surface facing the image _{side, L2 (r 16 ~r 18)} , the fifth lens group G5 has a negative refractive power as a whole, on the object side cemented meniscus lens L13 with a concave surface facing, L14 (r ₁₉ ~r ₂₁₎ and a positive lens L15 r ₂₂ ~r ₂₃₎ consisting of.
The objective lens of Example 5 satisfies the conditions (1), (2), and (3) as shown in the data.

    In each of Examples 1 to 5 described above, the following cover glass and oil are used.

Cover glass d = 0.17 mm, nd = 1.521, νd = 56
Oil nd = 1.515548, νd = 43.1
The above-described embodiments are all objective lenses with an infinite design in which the light emitted from the objective lens is a parallel light flux. Therefore, no image is formed by the objective lens itself. Therefore, the objective lens of the above embodiment is used in combination with an imaging lens having the following data, for example, in the lens configuration shown in FIG.

Number r d nd νd
1 68.7541 7.7321 1.48749 70.23
2 -37.5679 3.4742 1.80610 40.92
3 -102.8477 0.6973
4 84.3099 6.0238 1.83400 37.16
5 -50.7100 3.0298 1.64450 40.82
6 40.6619

In the above data, r, d, nd, and νd are the radius of curvature, the surface spacing, the refractive index of the d-line, and the Abbe number with respect to the d-line, which are described in order from the objective lens side.

    The focal length of this imaging lens is F = 180, and the distance between both lens systems when combined with the objective lens (each example) may be any one between 50 mm and 170 mm.

    Incidentally, the unit of length in the data of the embodiment, the imaging lens and the like is mm.

    The aberration states when combined with the imaging lens of each of the embodiments described above (the distance between the two is 120 mm) are as shown in FIGS. 6, 7, 8, 9, and 10, respectively.

    As shown in FIGS. 6 to 10, spherical aberration, chromatic aberration, and the like are satisfactorily corrected in all the examples.

    The immersion microscope objective lens of the present invention has a high numerical aperture of NA exceeding 1.46 and spherical aberration even when standard oil or cover glass is used without using special oil or cover glass. The chromatic aberration is corrected well.

Sectional drawing of Example 1 of the objective lens of this invention Sectional drawing of Example 2 of the objective lens of this invention Sectional drawing of Example 3 of the objective lens of this invention Sectional drawing of Example 4 of the objective lens of this invention Sectional drawing of Example 5 of the objective lens of this invention Aberration diagram of Example 1 of the objective lens of the present invention Aberration diagram of Example 2 of the objective lens of the present invention Aberration diagram of Embodiment 3 of the objective lens according to the present invention Aberration diagram of Embodiment 4 of the objective lens according to the present invention Aberration diagram of Embodiment 5 of the objective lens according to the present invention Sectional drawing which shows an example of the imaging lens used in combination with the said Example

Claims (2)

In order from the object side, a first lens group composed of a cemented lens in which a plano-convex lens having a plane facing the object side and a meniscus lens having a concave surface facing the object side are joined, and a second lens composed of one or two lenses A third lens group including a group, at least two cemented lenses, a fourth lens group including a negative lens having a strong concave surface facing the image side, and a fifth lens group including a meniscus lens having a concave surface facing the object side An immersion microscope objective lens that satisfies the following condition (1).
(1) 0.9 ≦ | f12 / f | ≦ 1.3
Here, f12 is a combined focal length of the first lens group and the second lens group, and f is a focal length of the entire objective lens system. The immersion microscope objective lens according to claim 1, wherein the following conditions (2) and (3) are satisfied.
(2) 0.7 ≦ | R12 / R13 | ≦ 1.4
(3) 0.7 ≦ | R12 / f | ≦ 1.3
Where R12 is the radius of curvature of the cemented surface of the first lens group, R13 is the radius of curvature of the image side surface of the first lens group, and f is the focal length of the entire objective lens system.

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