Microscope objective lens, microscope device, and microscope optical system

1 . A microscope objective lens comprising:

in order from an object side: a first lens group that has positive refractive power and converts light flux from an object into convergent light flux; and a second lens group that has negative refractive power and receives the convergent light flux from the first lens group,

wherein the second lens group comprises a first cemented lens and a second cemented lens which are placed next to each other,

the first cemented lens is made of a first positive lens and a first negative lens having a concave surface on an image side, the first negative lens being placed on the image side of the first positive lens and is cemented to the first positive lens,

the second cemented lens is placed on the image side of the first cemented lens, and the second cemented lens is made of a second negative lens having a concave surface on an object side and a second positive lens which is placed on the image side of the second negative lens, the second negative lens and the second positive lens being cemented with each other, and

the conditional expressions as follows are satisfied:

14.0 mm≤NA× f

1.0 <H 1 /H 0

where NA represents a numerical aperture of the microscope objective lens, and NA≥0.75,

f represents a focal length of the microscope objective lens,

H1 represents a maximum height of a marginal ray from an on-axis object point in the first lens group, and

H0 represents a height of the marginal ray at a lens surface closest to an image in the second lens group.

2 . The microscope objective lens according to claim 1 , wherein

a conditional expression as follows is satisfied:

0.45 ≤L 1 /TL≤ 0.75,

where L 1 represents a distance on an optical axis from a lens surface closest to the object in the first lens group to a lens surface at which the height of the marginal ray is largest in the first lens group, and

TL represents a distance on the optical axis from the lens surface closest to the object in the first lens group to the lens surface closest to the image in the second lens group.

3 . The microscope objective lens according to claim 1 , wherein

the second lens group converts the convergent light flux from the first lens group into parallel light flux.

4 . The microscope objective lens according to claim 1 , wherein

the second lens group comprises, in order from the object side, a first lens component with a concave lens surface on an image side and a second lens component with a concave lens surface on the object side, and

a conditional expression as is satisfied:

0.75 ≤L 2 /TL≤ 0.90,

where L 2 represents a distance on an optical axis from a lens surface closest to the object in the first lens group to one lens surface, out of the lens surface on the image side of the first lens component and the lens surface on the object side of the second lens component, the height of the marginal ray being smaller at the one lens surface than at the other, and

TL represents the distance on the optical axis from the lens surface closest to the object in the first lens group to the lens surface closest to the image in the second lens group.

5 . The microscope objective lens according to claim 4 , wherein

the first lens component is located closest to the object in the second lens group, and

the second lens component is located next to and on the image side of the first lens component.

6 . The microscope objective lens according to claim 1 , wherein

a conditional expression as follows is satisfied:

0.75 <f 1 /f< 1.20,

where f1: the focal length of the first lens group.

7 . A microscope device comprising the microscope objective lens according to claim 1 .

8 . A microscope optical system comprising the microscope objective lens according to claim 1 , and an image formation lens that forms an image from light from the microscope objective lens.

9 . The microscope objective lens according to claim 1 , wherein the second lens group has a cemented lens at a closest position to the object side.