Immersion objective
View Patent ↗An immersion objective includes a first lens group, with a positive refractive power, that converts divergent light from an object point into convergent light and a second lens group, with a negative refractive power, that is arranged closer to the image than is the first lens group. The immersion objective satisfies the conditional expression below where WD is a working distance of the immersion objective and D is a distance on an optical axis of the immersion objective from the observation target plane to the lens surface closest to the image in the immersion objective. 0.11≤WD/ D ≤0.7
1. An immersion objective comprising:
a first lens group, with a positive refractive power, that converts divergent light from an object point into convergent light; and
a second lens group, with a negative refractive power, that is arranged closer to an image than is the first lens group, wherein
the immersion objective satisfies
0.11≤WD/ D≤ 0.7 (1)
where WD is a working distance of the immersion objective and D is a distance on an optical axis of the immersion objective from an observation target plane to a lens surface closest to the image in the immersion objective.
2. The immersion objective according to claim 1 , wherein
the immersion objective satisfies
0.7≤ D G2 /WD≤5 (2)
wherein D G2 is a distance on the optical axis from a lens surface closest to an object in the second lens group to a lens surface closest to the image in the second lens group.
3. The immersion objective according to claim 1 , wherein
the second lens group includes:
a first meniscus lens component having a concave surface on an image side; and
a second meniscus lens component arranged closer to the image than is the first meniscus lens component and having a concave surface on an object side.
4. The immersion objective according to claim 3 , wherein
the immersion objective satisfies
0.46≤ D GL /f≤ 3 (3)
where D GL is a distance on the optical axis from a lens surface closest to an object in the second meniscus lens component to a lens surface closest to the image in the second meniscus lens component and f is a focal length of the immersion objective.
5. The immersion objective according to claim 3 , wherein
the second lens group further includes a third lens component, with a negative refractive power, that is arranged between the first and second meniscus lens components.
6. The immersion objective according to claim 5 , wherein
the immersion objective satisfies
2≤ D GL /D GM ≤40 (4)
where D GL is a distance on the optical axis from a lens surface closest to an object in the second meniscus lens component to a lens surface closest to the image in the second meniscus lens component and D GM is a distance on the optical axis from a lens surface closest to the object in the third lens component to a lens surface closest to the image in the third lens component.
7. The immersion objective according to claim 5 , wherein
the immersion objective satisfies
−0.15≤ D GM /f GM ≤−0.01 (5)
where D GM is a distance on the optical axis from a lens surface closest to an object in the third lens component to a lens surface closest to the image in the third lens component and f GM is a focal length of the third lens component.
8. The immersion objective according to claim 1 , comprising
a movable lens component that moves along the optical axis.
9. The immersion objective according to claim 8 , wherein
the movable lens component has a negative refractive power.
10. The immersion objective according to claim 8 , wherein
the movable lens component is a cemented lens.
11. The immersion objective according to claim 1 , wherein
the first lens group includes a plano-convex lens component having a planar surface on an object side and having a plano-convex shape, and
the plano-convex lens component is a front-end lens component arranged closest to an object in the first lens group.
12. The immersion objective according to claim 11 , wherein
the immersion objective satisfies
0.3≤ f U1 /WD≤4 (6)
where f U1 is a focal length of the front-end lens component.
13. The immersion objective according to claim 2 , wherein
the second lens group includes:
a first meniscus lens component having a concave surface on an image side; and
a second meniscus lens component arranged closer to the image than is the first meniscus lens component and having a concave surface on an object side.
14. The immersion objective according to claim 13 , wherein
the immersion objective satisfies
0.46≤ D GL /f≤ 3 (3)
where D GL is a distance on the optical axis from a lens surface closest to an object in the second meniscus lens component to a lens surface closest to the image in the second meniscus lens component and f is a focal length of the immersion objective.
15. The immersion objective according to claim 13 , wherein
the second lens group further includes a third lens component, with a negative refractive power, that is arranged between the first and second meniscus lens components.
16. The immersion objective according to claim 15 , wherein
the immersion objective satisfies
2≤ D GL /D GM ≤40 (4)
where D GL is a distance on the optical axis from a lens surface closest to an object in the second meniscus lens component to a lens surface closest to the image in the second meniscus lens component and D GM is a distance on the optical axis from a lens surface closest to the object in the third lens component to a lens surface closest to the image in the third lens component.
17. The immersion objective according to claim 2 , comprising
a movable lens component that moves along the optical axis.
18. The immersion objective according to claim 17 , wherein
the movable lens component has a negative refractive power.
19. The immersion objective according to claim 18 , wherein
the second lens group includes:
a first meniscus lens component having a concave surface on an image side; and
a second meniscus lens component arranged closer to the image than is the first meniscus lens component and having a concave surface on an object side.
20. The immersion objective according to claim 19 , wherein
the second lens group further includes a third lens component, with a negative refractive power, that is arranged between the first and second meniscus lens components.