Microscope objective
An objective includes the first and second groups. The first group includes the first cemented lens with a concave surface facing the object side, the first and second single lenses having positive power, and the second cemented lens with a concave surface facing an image side. The second group includes the third cemented lens with a concave surface facing the object side and a third single lens having positive power. Each of the cemented lenses combines one positive lens with one negative lens. The objective satisfies the following expressions. 0.31≤NA<1 (1) 2.2≤ H/f ≤3.3 (2) 0< a/b ≤1.2 (3) Here, NA is a numerical aperture, f is a focal length at e-line, H is a distance from an object surface to a lens surface closest to an image, a is the sum of air-gap distances in the first group, and b is a thickness of a negative lens in the second cemented lens.
1. A dry microscope objective, comprising, in order from an object side:
a first lens group; and
a second lens group,
wherein the first lens group includes, in order from the object side:
a first cemented lens with a concave surface facing the object side;
a first single lens having a positive refractive power;
a second single lens having a positive refractive power; and
a second cemented lens with a concave surface facing an image side,
wherein the second lens group includes, in order from the object side:
a third cemented lens with a concave surface facing the object side; and
a third single lens having a positive refractive power,
wherein each of the first cemented lens, the second cemented lens, and the third cemented lens is a cemented doublet lens that combines one positive lens with one negative lens, and
wherein the microscope objective satisfies conditional expressions of:
0.31≤NA<1 (1);
2.2≤ H/f≤ 3.3 (2); and
0< a/b≤ 1.2 (3),
where NA is a numerical aperture of the microscope objective on the object side, f is a focal length of the microscope objective at e-line, H is a distance from an object surface to a lens surface of the second lens group closest to an image, a is a sum of air-gap distances in the first lens group, and b is a thickness of a negative lens included in the second cemented lens.
2. The microscope objective according to claim 1 ,
wherein the microscope objective satisfies a conditional expression of
0< a/c≤ 1.2 (4)
where c is a thickness of a negative lens included in the first cemented lens.
3. The microscope objective according to claim 1 ,
wherein the microscope objective satisfies a conditional expressions of:
42≤ν d (−)≤55 (5); and
0.993≤θ hF (−)≤1.036 (6),
where νd(−) is an Abbe number of a first negative lens at d-line, the first negative lens being a negative lens included in any one of the first cemented lens, the second cemented lens and the third cemented lens, and θhF(−) is a partial dispersion ratio based on h-line and F-line for the first negative lens.
4. The microscope objective according to claim 2 ,
wherein the microscope objective satisfies a conditional expressions of:
42≤ν d (−)≤55 (5); and
0.993≤θ hF (−)≤1.036 (6),
where νd(−) is an Abbe number of a first negative lens at d-line, the first negative lens being a negative lens included in any one of the first cemented lens, the second cemented lens and the third cemented lens, and θhF(−) is a partial dispersion ratio based on h-line and F-line for the first negative lens.
5. The microscope objective according to claim 3 ,
wherein the first negative lens is a negative lens included in the first cemented lens.
6. The microscope objective according to claim 4 ,
wherein the first negative lens is a negative lens included in the first cemented lens.
7. The dry microscope objective according to claim 3 ,
wherein the microscope objective satisfies a conditional expressions of:
80≤ν d (+)≤100 (7); and
0.970≤θ hF (+)≤0.985 (8),
where νd(+) is an Abbe number of a first positive lens at d-line, the first positive lens being the positive lens combined with the first negative lens, and θhF(+) is a partial dispersion ratio based on h-line and F-line for the first positive lens.
8. The dry microscope objective according to claim 4 ,
wherein the microscope objective satisfies a conditional expressions of:
80≤ν d (+)≤100 (7); and
0.970≤θ hF (+)≤0.985 (8),
where νd(+) is an Abbe number of a first positive lens at d-line, the first positive lens being the positive lens combined with the first negative lens, and θhF(+) is a partial dispersion ratio based on h-line and F-line for the first positive lens.
9. The dry microscope objective according to claim 5 ,
wherein the microscope objective satisfies a conditional expressions of:
80≤ν d (+)≤100 (7); and
0.970≤θ hF (+)≤0.985 (8),
where νd(+) is an Abbe number of a first positive lens at d-line, the first positive lens being the positive lens combined with the first negative lens, and θhF(+) is a partial dispersion ratio based on h-line and F-line for the first positive lens.
10. The dry microscope objective according to claim 6 ,
wherein the microscope objective satisfies a conditional expressions of:
80≤ν d (+)≤100 (7); and
0.970≤θ hF (+)≤0.985 (8),
where νd(+) is an Abbe number of a first positive lens at d-line, the first positive lens being the positive lens combined with the first negative lens, and θhF(+) is a partial dispersion ratio based on h-line and F-line for the first positive lens.
11. The microscope objective according to claim 1 ,
wherein the microscope objective satisfies a conditional expressions of:
0≤|Δ z |/DOF e ≤4.5 (9),
where |Δz| is a difference between an axial best position at h-line and an axial best position at e-line, and DOF e is a depth of focus at e-line.
12. The microscope objective according to claim 2 ,
wherein the microscope objective satisfies a conditional expressions of:
0≤|Δ z |/DOF e ≤4.5 (9),
where |Δz| is a difference between an axial best position at h-line and an axial best position at e-line, and DOF e is a depth of focus at e-line.
13. The microscope objective according to claim 3 ,
wherein the microscope objective satisfies a conditional expressions of:
0≤|Δ z |/DOF e ≤4.5 (9),
where |Δz| is a difference between an axial best position at h-line and an axial best position at e-line, and DOF e is a depth of focus at e-line.
14. The microscope objective according to claim 4 ,
wherein the microscope objective satisfies a conditional expressions of:
0≤|Δ z |/DOF e ≤4.5 (9),
where |Δz| is a difference between an axial best position at h-line and an axial best position at e-line, and DOF e is a depth of focus at e-line.
15. The microscope objective according to claim 5 ,
wherein the microscope objective satisfies a conditional expressions of:
0≤|Δ z |/DOF e ≤4.5 (9),
where |Δz| is a difference between an axial best position at h-line and an axial best position at e-line, and DOF e is a depth of focus at e-line.
16. A dry microscope objective, comprising in order from an object side:
a first lens group; and
a second lens group,
wherein the first lens group includes, in order from the object side:
a first cemented lens with a concave surface facing the object side;
a first single lens having a positive refractive power;
a second single lens having a positive refractive power; and
a second cemented lens with a concave surface facing an image side,
wherein the second lens group includes, in order from the object side:
a third cemented lens with a concave surface facing the object side; and
a third single lens having a positive refractive power,
wherein each of the first cemented lens, the second cemented lens, and the third cemented lens is a cemented doublet lens that combines one positive lens with one negative lens, and
wherein the microscope objective satisfies conditional expressions of:
0.31≤NA<1 (1);
2.2≤ H/f≤ 3.3 (2);
42≤ν d (−)≤55 (5); and
0.993≤θ hF (−)≤1.036 (6),
where NA is a numerical aperture of the microscope objective on the object side, f is a focal length of the microscope objective at e-line, H is a distance from an object surface to a lens surface of the second lens group closest to an image, νd(−) is an Abbe number of a first negative lens at d-line, the first negative lens being a negative lens included in any one of the first cemented lens, the second cemented lens and the third cemented lens, and θhF(−) is a partial dispersion ratio based on h-line and F-line for the first negative lens.
17. The microscope objective according to claim 16 ,
wherein the first negative lens is a negative lens included in the first cemented lens.
18. The dry microscope objective according to claim 16 ,
wherein the microscope objective satisfies a conditional expressions of:
80≤ν d (+)≤100 (7); and
0.970≤θ hF (+)≤0.985 (8),
where νd(+) is an Abbe number of a first positive lens at d-line, the first positive lens being the positive lens combined with the first negative lens, and θhF(+) is a partial dispersion ratio based on h-line and F-line for the first positive lens.
19. The microscope objective according to claim 16 ,
wherein the microscope objective satisfies a conditional expressions of:
0≤|Δ z |/DOF e ≤4.5 (9),
where |Δz| is a difference between an axial best position at h-line and an axial best position at e-line, and DOF e is a depth of focus at e-line.
20. A dry microscope objective, comprising in order from an object side:
a first lens group; and
a second lens group,
wherein the first lens group includes, in order from the object side:
a first cemented lens with a concave surface facing the object side;
a first single lens having a positive refractive power;
a second single lens having a positive refractive power; and
a second cemented lens with a concave surface facing an image side,
wherein the second lens group includes, in order from the object side:
a third cemented lens with a concave surface facing the object side; and
a third single lens having a positive refractive power,
wherein each of the first cemented lens, the second cemented lens, and the third cemented lens is a cemented doublet lens that combines one positive lens with one negative lens, and
wherein the microscope objective satisfies conditional expressions of:
0.31≤NA<1 (1);
2.2≤ H/f≤ 3.3 (2); and
0≤|Δ z |/DOF e ≤4.5 (9),
where NA is a numerical aperture of the microscope objective on the object side, f is a focal length of the microscope objective at e-line, H is a distance from an object surface to a lens surface of the second lens group closest to an image, |Δz| is a difference between an axial best position at h-line and an axial best position at e-line, and DOF e is a depth of focus at e-line.