Dry objective
A dry objective including the first lens group having a positive refractive power that converts a divergent pencil of light from an object point into a convergent pencil of light and the second lens group having a negative refractive power. The objective includes a moving lens component that moves along an optical axis and satisfies the following conditional expressions of: 0.85≤NA ob <1.0 (1); and 9 mm≤ Y reso ×|β|≤20 mm (3), where NA ob is a numerical aperture, Y reso is a maximum object height in a region in which a value obtained by dividing RMS wavefront aberration at the e-line by a wavelength of the e-line is 0.2 or smaller, the region being on a plane that is orthogonal to the optical axis and intersects with an on-axis position at which the RMS wavefront aberration at the e-line is minimized, and β is a magnification of the objective.
1. A dry objective comprising:
a first lens group having a positive refractive power that converts a divergent pencil of light from an object point into a convergent pencil of light; and
a second lens group having a negative refractive power and being arranged closer to an image than the first lens group being,
wherein the dry objective includes a moving lens component that moves along an optical axis, and satisfies conditional expressions of:
0.85≤NA ob <1.0 (1); and
9 mm≤ Y reso ×|β|≤20 mm (3),
where NA ob is a numerical aperture of the dry objective, Y reso is a maximum object height in a region in which a value obtained by dividing RMS wavefront aberration at e-line by a wavelength of the e-line is 0.2 or smaller, the region being on a plane that is orthogonal to the optical axis and intersects with an on-axis position at which the RMS wavefront aberration at the e-line is minimized, and β is a magnification of the dry objective.
2. The dry objective according to claim 1 , wherein
the dry objective includes a first negative lens, and satisfies conditional expressions of:
30≤ν d 1 =43 (4); and
0.55≤θ gF 1 ≤0.57 (5)
where νd 1 is an Abbe number of the first negative lens, and θgF 1 is a partial dispersion ratio of the first negative lens.
3. The dry objective according to claim 2 , wherein
the dry objective includes a second negative lens that is different from the first negative lens and satisfies conditional expressions of:
30≤ν d 2 ≤43 (6); and
0.55≤θ gF 2 ≤0.57 (7)
where νd 2 is an Abbe number of the second negative lens and θgF 2 is a partial dispersion ratio of the second negative lens.
4. The dry objective according to claim 1 , wherein
the second lens group
includes a first Gauss lens component that is a meniscus lens component with a concave surface facing an image side and a second Gauss lens component that is arranged closer to the image than the first Gauss lens component is and is a meniscus lens component with a concave surface facing an object side, or
includes the first Gauss lens component, a third Gauss lens component that is arranged closer to the image than the first Gauss lens component is and is a lens component with a convex surface facing the image side, and a fourth Gauss lens component that is arranged between the first Gauss lens component and the third Gauss lens component and is a lens component with a concave surface facing the object side, and
the dry objective further includes a cemented triplet lens.
5. The dry objective according to claim 4 , wherein
the cemented triplet lens includes
a negative lens; and
two positive lenses arranged on either side of the negative lens.
6. The dry objective according to claim 5 , wherein
the dry objective satisfies a conditional expression of
1.4≤ n eo ≤1.55 (8)
where n eo is a refractive index at the e-line of the negative lens included in the cemented triplet lens.
7. The dry objective according to claim 5 , wherein
the dry objective satisfies a conditional expression of
60≤ν d 0 ≤80 (9)
where νd o is an Abbe number of the negative lens included in the cemented triplet lens.
8. The dry objective according to claim 4 , wherein
the third Gauss lens component and the fourth Gauss lens component are arranged adjacent to each other with an air gap therebetween.
9. The dry objective according to claim 8 , wherein
the dry objective satisfies a conditional expression of
0.005≤ D GM1 /D GM2 ≤0.5 (10)
where D GM1 is a distance on the optical axis between a lens surface on the object side of the third Gauss lens component and a lens surface on the image side of the fourth Gauss lens component, and D GM2 is a distance on the optical axis between a lens surface on the image side of the third Gauss lens component and a lens surface on the object side of the fourth Gauss lens component.
10. The dry objective according to claim 4 , wherein
the first Gauss lens component is a cemented doublet lens, and
the dry objective satisfies a conditional expression of
−3≤ R cem /D Go ≤−0.5 (11)
where R cem is a radius of curvature of a cemented surface of the cemented doublet lens and D Go is a thickness of the cemented doublet lens on the optical axis.
11. The dry objective according to claim 1 , wherein
the dry objective includes a first lens component that is arranged closest to the object and has a meniscus lens shape with a concave surface facing an object side and satisfies a conditional expression of
−3≤ D 1 /R 12 ≤−0.75 (12)
where D 1 is a thickness of the first lens component on the optical axis, and R 12 is a radius of curvature of a lens surface closest to the image in the first lens component.
12. The dry objective according to claim 11 , wherein
the dry objective includes a second lens component that is arranged on an image side of the first lens component and has a positive refractive power and a meniscus shape with a concave face facing the object side.
13. The dry objective according to claim 1 , wherein
the dry objective satisfies a conditional expression of
0.5≤ M UC ≤2 (13)
where M UC is a magnification of the moving lens component.
14. The dry objective according to claim 1 , wherein
the moving lens component has a meniscus lens shape with a concave surface facing an object side.
15. The dry objective according to claim 1 , wherein
The moving lens component satisfies a conditional expression of
−0.3≤ f/f UC ≤0.3 (14)
where f is a focal length of the dry objective and f UC is a focal length of the moving lens component.
16. A dry objective comprising:
a first lens group having a positive refractive power that converts a divergent pencil of light from an object point into a convergent pencil of light; and
a second lens group having a negative refractive power and being arranged closer to an image than the first lens group being,
wherein the dry objective includes a moving lens component that moves along an optical axis, and satisfies conditional expressions of:
0.85≤NA ob <1.0 (1); and
−2≤Δ z 1 /DOF e ≤2 (2),
where NA ob is a numerical aperture of the dry objective, Δz 1 is a difference between an on-axis position at which RMS wavefront aberration at a h-line is minimized and an on-axis position at which RMS wavefront aberration at an e-line is minimized, and DOF e is a depth of focus at the e-line.
17. The dry objective according to claim 16 , wherein
the dry objective satisfies a conditional expression of
9 mm≤ Y reso ×|β|≤20 mm (3),
where Y reso is a maximum object height in a region in which a value obtained by dividing RMS wavefront aberration at the e-line by a wavelength of the e-line is 0.2 or smaller, the region being on a plane that is orthogonal to the optical axis and intersects with the on-axis position at which the RMS wavefront aberration at the e-line is minimized, and β is a magnification of the dry objective.
18. The dry objective according to claim 16 , wherein
the dry objective includes a first negative lens, and satisfies conditional expressions of:
30≤ν d 1 =43 (4); and
0.55≤θ gF 1 ≤0.57 (5)
where νd 1 is an Abbe number of the first negative lens, and θgF 1 is a partial dispersion ratio of the first negative lens.
19. The dry objective according to claim 18 , wherein
the dry objective includes a second negative lens that is different from the first negative lens and satisfies conditional expressions of:
30≤ν d 2 ≤43 (6); and
0.55≤θ gF 2 ≤0.57 (7)
where νd 2 is an Abbe number of the second negative lens and θgF 2 is a partial dispersion ratio of the second negative lens.
20. The dry objective according to claim 16 , wherein
the second lens group
includes a first Gauss lens component that is a meniscus lens component with a concave surface facing an image side and a second Gauss lens component that is arranged closer to the image than the first Gauss lens component is and is a meniscus lens component with a concave surface facing an object side, or
includes the first Gauss lens component, a third Gauss lens component that is arranged closer to the image than the first Gauss lens component is and is a lens component with a convex surface facing the image side, and a fourth Gauss lens component that is arranged between the first Gauss lens component and the third Gauss lens component and is a lens component with a concave surface facing the object side, and
the dry objective further includes a cemented triplet lens.