Immersion objective

1. An immersion objective comprising, in order from an object side:

a first lens group that has a positive refractive power;

a second lens group that has a positive refractive power; and

a third lens group that has a negative refractive power, wherein

the immersion objective has a numerical aperture of 1.42 or higher on the object side,

the first lens group includes a first cemented lens that includes a plano-convex lens and a first meniscus lens that has a concave surface facing the object side, and at least one positive lens,

the second lens group includes a plurality of cemented lenses,

the third lens group includes, in order from the object side, a second cemented lens that has a concave surface facing an image side and includes a positive lens and a negative lens, a negative lens that has a concave surface facing the object side, and a positive lens, and

a conditional expression below

3.5≤( H/f )×NA ob ≤5.2  (1)

is satisfied when H is a maximum value of a height of an axial marginal ray in the immersion objective, f is a focal length of the immersion objective, and NA ob is a numerical aperture of the immersion objective.

2. The immersion objective according to claim 1 , wherein

a conditional expression below

1.8≤(( H−L )/ f )λNA ob ≤3.2  (2)

is satisfied when L is a minimum value of a height of an axial marginal ray in the third lens group.

3. The immersion objective according to claim 2 , wherein

a conditional expression below

1≤( f 1 /f )×NA ob ≤1.4  (3)

is satisfied when f 1 is a focal length of the first cemented lens.

4. The immersion objective according to claim 3 , wherein

a conditional expression below

1.75≤ n 1 ≤1.9  (4)

is satisfied when n 1 is a refractive index of the first meniscus lens.

5. The immersion objective according to claim 3 , wherein

a conditional expression below

9≤ f p /f≤ 17  (5)

is satisfied when f p is a parfocalizing distance of the immersion objective.

6. The immersion objective according to claim 3 , wherein

the immersion objective includes a first negative lens, and

a conditional expression below

0.005≤ d/h 1 ≤0.1  (6)

is satisfied when d is a thickness of the first negative lens on an optical axis, and h 1 is a height of an axial marginal ray on a lens surface on the object side of the first negative lens.

7. The immersion objective according to claim 4 , wherein

a conditional expression below

9≤ f p /f≤ 17  (5)

is satisfied when f p is a parfocalizing distance of the immersion objective.

8. The immersion objective according to claim 2 , wherein

a conditional expression below

1.75≤ n 1 ≤1.9  (4)

is satisfied when n 1 is a refractive index of the first meniscus lens.

9. The immersion objective according to claim 8 , wherein

a conditional expression below

9≤ f p /f≤ 17  (5)

is satisfied when f p is a parfocalizing distance of the immersion objective.

10. The immersion objective according to claim 2 , wherein

a conditional expression below

9≤ f p /f≤ 17  (5)

is satisfied when f p is a parfocalizing distance of the immersion objective.

11. The immersion objective according to claim 2 , wherein

the immersion objective includes a first negative lens, and

a conditional expression below

0.005≤ d/h 1 ≤0.1  (6)

is satisfied when d is a thickness of the first negative lens on an optical axis, and h 1 is a height of an axial marginal ray on a lens surface on the object side of the first negative lens.

12. The immersion objective according to claim 1 , wherein

a conditional expression below

1≤( f 1 /f )×NA ob ≤1.4  (3)

is satisfied when f 1 is a focal length of the first cemented lens.

13. The immersion objective according to claim 12 , wherein

a conditional expression below

1.75≤ n 1 ≤1.9  (4)

is satisfied when n 1 is a refractive index of the first meniscus lens.

14. The immersion objective according to claim 12 , wherein

a conditional expression below

9≤ f p /f≤ 17  (5)

is satisfied when f p is a parfocalizing distance of the immersion objective.

15. The immersion objective according to claim 12 , wherein

the immersion objective includes a first negative lens, and

a conditional expression below

0.005≤ d/h 1 ≤0.1  (6)

is satisfied when d is a thickness of the first negative lens on an optical axis, and h 1 is a height of an axial marginal ray on a lens surface on the object side of the first negative lens.

16. The immersion objective according to claim 13 , wherein

a conditional expression below

9≤ f p /f≤ 17  (5)

is satisfied when f p is a parfocalizing distance of the immersion objective.

17. The immersion objective according to claim 1 , wherein

a conditional expression below

1.75≤ n 1 ≤1.9  (4)

is satisfied when n 1 is a refractive index of the first meniscus lens.

18. The immersion objective according to claim 17 , wherein

a conditional expression below

9≤ f p /f≤ 17  (5)

is satisfied when f p is a parfocalizing distance of the immersion objective.

19. The immersion objective according to claim 1 , wherein

a conditional expression below

9≤ f p /f≤ 17  (5)

is satisfied when f p is a parfocalizing distance of the immersion objective.

20. The immersion objective according to claim 1 , wherein

the immersion objective includes a first negative lens, and

a conditional expression below

0.005≤ d/h 1 ≤0.1  (6)

is satisfied when d is a thickness of the first negative lens on an optical axis, and h 1 is a height of an axial marginal ray on a lens surface on the object side of the first negative lens.