Microscope objective lens

Claim 2

A microscope objective lens having a great numerical aperture and a high magnification and yet being capable of always maintaining an excellent imaging performance even if the thickness of a parallel flat plate such as a cover glass disposed between the object surface and the objective lens is varied greatly, said objective lens comprising, in succession from the object side, a first lens group having a positive refractive power and converting a light flux from an object into a convergent light flux, a second lens group of small refractive power creating positive spherical aberration and being movable along the optical axis in said convergent light flux, and a third lens group having a negative refractive power, said second lens group being movable relative to said first and third lens groups in accordance with a variation in the thickness of the parallel flat plate disposed between said object and said first lens group, whereby any fluctuation of aberrations may be corrected.

Claim 3

A microscope objective lens according to claim 1, wherein said second lens group is moved toward said third lens group when the thickness of said parallel flat plate is greater than a predetermined reference value, and is moved toward said first lens group when the thickness of said parallel flat plate is smaller than the predetermined reference value.

Claim 4

A microscope objective lens according to claim 2, wherein said first lens group has the function of creating negative spherical aberration, and said third lens group has the function of correcting the Petzval sum of the entire system and maintaining the planarity of the image plane.

Claim 5

A microscope objective lens according to claim 3, satisfying the following condition: h.sub.1 >h.sub.2 >h.sub.3 where h 1 and h 2 are the maximum values of the heights at which the paraxial ray from the on-axis object point cuts said first lens group and said second lens group respectively and h 3 is the height of the paraxial ray from the on-axis object point which emerges from said third lens group.

Claim 6

A microscope objective lens according to claim 4, further satisfying the following condition: 6h.sub.3 >h.sub.1 >2h.sub.3.

Claim 7

A microscope objective lens according to claim 5, wherein the gradient of a light ray passing through said first lens group is five to ten times the gradient of a light ray passing through the entire system.

Claim 8

A microscope objective lens according to claim 3, wherein said third lens group comprises a meniscus lens component which has its convex surface facing the object side and has a cemented convex surface facing the image side, and comprises a negative lens component which has a concave surface facing the object side.

Claim 9

A microscope objective lens according to claim 7, wherein said second lens group has a cemented component comprising a negative meniscus lens convex toward the object side, a biconvex position lens and a negative lens.

Claim 10

A microscope objective lens according to claim 8, wherein numerical data are as follows: Focal length f=1.0 N.A.=0.7 Magnification β=61 __________________________________________________________________________ Center thickness Radius of and air space of Refractive Abbe No. curvature r each lens d index n number ν __________________________________________________________________________ ∞ (0.4548) 1.52216 58.8 Cover ∞ (d.sub.0 = 1.3859) 1.0 glass P 1 -2.8310 0.9475 1.713 54.0 L.sub.1 2 -1.9995 0.00758 1.0 3 +24.7522 0.8527 1.49782 82.3 L.sub.2 4 -4.5072 0.0379 1.0 G1 5 +5.6203 0.5685 1.75692 31.7 L.sub.3 6 +3.6523 2.0465 1.43388 95.6 7 -6.4804 (d.sub.7 = variable) 1.0 8 +6.5565 0.2842 1.6968 55.6 L.sub.4 9 +2.8716 1.8191 1.43388 95.6 L.sub.5 G2 10 -2.8716 0.3411 1.62041 60.3 L.sub.6 11 -15.9184 (d.sub.11 = variable) 1.0 12 +2.5017 0.9664 1.49782 82.3 L.sub.7 13 -142.5109 0.2274 1.71736 29.5 L.sub.8 G31 14 +1.5694 0.9475 1.713 54.0 L.sub.9 15 +3.0702 2.9750 1.0 G3 16 -1.4057 1.0820 1.713 54.0 L.sub.10 G32 17 +1.7331 0.7580 1.72825 28.3 L.sub.11 18 -3.8671 1.0 __________________________________________________________________________ Thickness of cover glass d.sub.0 d.sub.7 d.sub.11 __________________________________________________________________________ 0.2653f 1.5130 1.2128 1.7812 0.4548f 1.3859 1.8570 1.1370 0.6443f 1.2584 2.6529 0.3411 __________________________________________________________________________ where the left-hand numbers represent the order from the object side, and d 0 represents the distance from the vertex of the foremost lens surface of the objective lens to the surface of the cover glass.

Claim 11

A microscope objective lens having a great numerical aperture and a high magnification and yet being capable of always maintaining an excellent imaging performance even if the thickness of a parallel flat plate such as a cover glass disposed between the object surface and the objective lens is varied greatly, said objective lens comprising, in succession from the object side, a first lens group having a positive refractive power and converting a light flux from an object into a convergent light flux, a second lens group of negative refractive power creating positive spherical aberration and being movable along the optical axis in said convergent light flux, and a third lens group having a negative refractive power, said second lens group being movable relative to said first and third lens groups in accordance with a variation in the thickness of the parallel flat plate disposed between said object and said first lens group, whereby any fluctuation of aberrations may be corrected.

Claim 12

A microscope objective lens having a great numerical aperture and a high magnification and yet being capable of always maintaining an excellent imaging performance even if the thickness of a parallel flat plate such as a cover glass disposed between the object surface and the objective lens is varied greatly, said objective lens comprising, in succession from the object side, a first lens group having a positive refractive power and converting a light flux from an object into a convergent light flux, a second lens group of negative refractive power creating positive spherical aberration and being movable along the optical axis in said convergent light flux, and a third lens group having a negative refractive power, said second lens group being movable relative to said first and third lens groups in accordance with a variation in the thickness of the parallel flat plate disposed between said object and said first lens group, whereby any fluctuation of aberrations may be corrected.

Claim 13

A microscope objective lens according to claim 10, satisfying the following condition: -50f<f.sub.2 <-10f where f 2 is a focal length of said second lens group and f is a focal length of the entire system.

Claim 14

A microscope objective lens according to claim 11, wherein said second lens group is moved toward said third lens group when the thickness of said parallel flat plate is greater than a predetermined reference value, and is moved toward said first lens group when the thickness of said parallel flat plate is smaller than the predetermined reference value.

Claim 15

A microscope objective lens according to claim 12, wherein said first lens group has the function of creating negative spherical aberration, and said third lens group has the function of correcting the Petzval sum of the entire system and maintaining the planarity of the image plane.

Claim 16

A microscope objective lens according to claim 13, satisfying the following condition: h.sub.1 >h.sub.2 >h.sub.3 where h 1 and h 2 are the maximum values of the heights at which the paraxial ray from the on-axis object point cuts said first lens group and said second lens group respectively and h 3 is the height of the paraxial ray from the on-axis object point which emerges from said third lens group.

Claim 17

A microscope objective lens according to claim 14, further satisfying the following condition: 6h.sub.3 >h.sub.1 >2h.sub.3.

Claim 18

A microscope objective lens according to claim 15, wherein the gradient of a light ray passing through said first lens group is five to ten times the gradient of a light ray passing through the entire system.

Claim 19

A microscope objective lens according to claim 16, wherein said second lens group has a biconvex positive lens, a negative meniscus lens cemented to the object side of the biconvex positive lens and having its convex surface facing the object side and a negative meniscus lens cemented to the image side of the biconvex positive lens and having its convex surface facing the image side.

Claim 20

A microscope objective lens according to claim 16, wherein said third lens group has a meniscus-form front group having weak positive refractive power and having its convex surface facing the object side and a meniscus-form rear group having weak negative refractive power and having its concave surface facing the object side.

Claim 21

A microscope objective lens according to claim 16, wherein numerical data are as follows: Focal length f=1.000 N.A=0.7 Back focal length Bf=45.4613, Magnification 50 ______________________________________ Re- Radius of Center thickness fractive Abbe curvature and air space of index number No. r each lens d n ν ______________________________________ 1 -1.9140 0.6379 1.65160 58.52 G1 2 -1.2772 0.0463 3 45.7324 0.4639 1.49782 82.28 4 -2.8114 0.2320 5 3.2217 0.3364 1.75520 27.54 6 2.2501 1.1830 1.43388 95.57 7 -4.7993 (variable) 8 4.2865 0.1738 1.69680 55.61 G2 9 1.8096 1.2062 1.43388 95.57 10 -1.9434 0.2320 1.69680 55.61 11 -9.2691 (variable) 12 1.4498 0.5915 1.49782 82.28 G31 13 6.2412 0.1508 1.74000 28.27 14 1.3200 0.6263 1.49782 82.28 15 1.8223 1.5774 16 -0.8604 0.2552 1.61266 44.40 G32 17 1.1462 0.8583 1.16150 30.98 18 -1.6587 45.4613 ______________________________________ Thickness of cover glass d0 d7 d11 ______________________________________ 0.0 1.1023 0.3978 1.2143 0.2320 0.9386 0.9487 0.66342 0.3480 0.8559 1.3036 0.3085 ______________________________________ where the left-hand numbers represent the order from the object side, and do represents the distance from the vertex of the foremost lens surface of the objective lens to the surface of the cover glass.

Claim 22

A microscope objective lens according to claim 16, wherein numerical data are as follows: Focal length f=1.000 N.A=0.7 Back focal length Bf=45.2844, Magnification 50 ______________________________________ Re- Radius of Center thickness fractive Abbe curvature and air space of index number No. r each lens d n ν ______________________________________ 1 -1.9379 0.6337 1.67003 47.05 G1 2 -1.2687 0.0461 3 50.2135 0.6913 1.49782 82.56 4 -3.0050 0.0230 5 3.6834 0.2304 1.72825 28.34 6 2.6195 1.0369 1.43388 95.57 7 -4.9157 (variable) 8 4.8493 0.1728 1.75692 31.70 G2 9 2.2043 1.1982 1.43388 95.57 10 -1.9013 0.2535 1.74810 52.28 11 -7.3956 (variable) 12 1.2687 0.9908 1.49782 82.56 G31 13 -6.8225 0.2650 1.75692 31.70 14 1.6699 1.4747 15 -0.6686 1.2420 1.61266 44.40 G32 16 1.5001 1.0024 1.61650 30.98 17 -1.4705 ______________________________________ Thickness of cover glass d0 d7 d11 ______________________________________ 0.0 1.1761 0.3860 1.2155 0.2304 1.0192 0.9355 0.6659 0.3456 0.9395 1.2881 0.3134 ______________________________________ where the left-hand numbers represent the order from the object side, and do represents the distance from the vertex of the foremost lens surface of the objective lens to the surface of the cover glass.

Claim 23

A microscope objective lens according to claim 16, wherein numerical data are as follows: Focal length f=1.000 N.A=0.7 Back focal length Bf=45.3073, Magnification 50 ______________________________________ Re- Radius of Center thickness fractive Abbe curvature and air space of index number No. r each lens d n ν ______________________________________ 1 -2.0272 0.6363 1.67003 47.05 G1 2 -1.2844 0.0463 3 798.2851 0.6942 1.49782 82.56 4 -3.0543 0.0231 5 3.5388 0.2777 1.72825 28.34 6 2.5399 1.1569 1.43388 95.57 7 -4.8577 (variable) 8 4.6745 0.1735 1.74950 35.19 G2 9 4.6745 1.2032 1.43388 95.57 10 -1.9137 0.2314 1.74810 52.28 11 -8.0914 (variable) 12 1.3167 1.0644 1.49782 82.56 G31 13 -5.6216 0.2545 1.75520 27.64 14 1.7484 1.5804 15 -0.6759 0.1851 1.61266 44.40 G32 16 1.0022 1.0181 1.61650 30.98 17 -1.4347 ______________________________________ Thickness of cover glass d0 d7 d11 ______________________________________ 0.0 1.1795 0.4049 1.2032 0.2314 1.0218 0.9533 0.6548 0.3471 0.9418 1.3062 0.3020 ______________________________________ where the left-hand numbers represent the order from the object side, and do represents the distance from the vertex of the foremost lens surface of the objective lens to the surface of the cover glass.

Claim 24

A microscope objective lens having a great numerical aperture and a high magnification and yet being capable of always maintaining an excellent imaging performance even if the thickness of a parallel flat plate such as a cover glass disposed between the object surface and the objective lens is varied greatly, said objective lens comprising: a first lens group having a positive refractive power and converting a light flux from an object into a convergent light flux, said first lens group creating negative spherical aberration; a second lens group disposed in the convergent light flux from the first lens group and being movable along the optical axis thereof, said second lens group creating positive spherical aberration; and a third lens group having a negative refractive power and receiving the light flux from the second lens group; wherein when the thickness of said parallel flat plate is greater than a predetermined reference value, said second lens group is moved toward said third lens group in the convergent light flux emerging from the first lens group so as to compensate the positive spherical aberration created by said greater thickness parallel flat plate, and when the thickness of said parallel flat plate is smaller than said predetermined reference value, said second lens group is moved toward said first lens group in the convergent light flux emerging from the first lens group so as to compensate the negative spherical aberration created by said smaller thickness parallel flat plate.

Claim 25

A microscope objective lens having a great numerical aperture and a high magnification and yet being capable of always maintaining an excellent imaging performance even if the thickness of a parallel flat plate such as a cover glass disposed between the object surface and the objective lens is varied greatly, said objective lens comprising: a first lens group having a positive refractive power and converting a light flux from an object into a convergent light flux, said first lens group creating negative spherical aberration; a second lens group disposed in the convergent light flux from the first lens group and being movable along the optical axis thereof, said second lens group creating positive spherical aberration; and a third lens group having a negative refractive power and receiving the light flux from the second lens group; wherein when the thickness of said parallel flat plate is greater than a predetermined reference value, said second lens group is moved toward said third lens group in the convergent light flux emerging from the first lens group so as to compensate the positive spherical aberration created by said greater thickness parallel flat plate, and when the thickness of said parallel flat plate is smaller than said predetermined reference value, said second lens group is moved toward said first lens group in the convergent light flux emerging from the first lens group so as to compensate the negative spherical aberration created by said smaller thickness parallel flat plate.

Claim 26

A microscope objective lens according to claim 22, wherein said movable second lens group has a negative refractive power.

Claim 27

A microscope objective lens according to claim 22, wherein said movable second lens group includes a biconvex positive lens, a negative meniscus lens cemented to the object side of the biconvex positive lens and a negative meniscus lens cemented to the image side of the biconvex positive lens.