Relay optical system and microscope apparatus
A relay optics includes a positive first lens group, a positive second lens group, and a positive third lens group. The second lens group includes, closest to the object, a lens having the concave surface facing toward the object. The relay optics is configured in such a manner that a light flux passing between the second and third lens groups is a substantially-parallel light flux, and satisfies condition expressions below, where f 1 represents the focal length of the first lens group, d 1 represents the length from the primary image to a surface closest to the object in the first lens group, f 12 represents the combined focal length of the first and second lens groups, and exp 12 represents the length from an exit pupil position of an optics consisting of the first and second lens groups to a surface closest to the object in the second lens group: 1≦ f 1 /d 1 ≦4.3 0.16≦exp 12 /f 12 ≦1.2.
1. A relay optical system for a microscope apparatus that relays a primary image of an object formed by an objective and a tube lens and that forms a secondary image, the relay optical system comprising in an order from an object side:
a first lens group with positive power;
a second lens group with positive power; and
a third lens group with positive power, wherein
the second lens group includes, closest to the object, a lens having a concave surface facing toward the object, and
the relay optical system
is configured in such a manner that a light flux passing between the second lens group and the third lens group is a substantially-parallel light flux, and
satisfies condition expressions below, where f 1 represents a focal length of the first lens group, d 1 represents a length from the primary image to a surface closest to the object in the first lens group, f 12 represents a combined focal length of the first lens group and the second lens group, and exp 12 represents a length from an exit pupil position of an optical system consisting of the first lens group and the second lens group to a surface closest to the object in the second lens group, the exit pupil position being calculated by a paraxial ray tracing:
1≦ f 1 /d 1 ≦4.3
0.16≦exp 12 /f 12 ≦1.2.
2. The relay optical system according to claim 1 , wherein
the second lens group
consists of at least three lenses, and
includes a meniscus lens with negative power that consists of a single lens or a cemented lens and that has a concave surface facing toward the object, and
the relay optical system
satisfies a condition expression below, where M represents thickness of the meniscus lens, nd G2 represents a refractive index of the lens closest to the object in the second lens group with respect to d-line, and R 2 represents a curvature radius of a concave surface closest to the object in the second lens group:
0.5≦ M×nd G2 /|R 2 |≦2.
3. The relay optical system according to claim 1 , wherein
the relay optical system satisfies condition expressions below, where ν G1 represents Abbe number of a lens with smallest Abbe number among lenses with positive power that constitute the first lens group and ν G2 represents Abbe number of a lens with smallest Abbe number among lenses with positive power that constitute the second lens group:
60≦ν G1
60≦ν G2 .
4. The relay optical system according to claim 1 , wherein
the third lens group includes in an order from an object side:
a 3-1st lens group that is a lens group with positive power; and
a 3-2nd lens group that is a lens group with negative power and that consists of one cemented lens or a single lens,
the relay optical system satisfies a condition expression below, where f 3 represents a combined focal length of the 3-1st lens group and the 3-2nd lens group and exp 123 represents a length from the exit pupil position of an optical system consisting of the first lens group and the second lens group to a surface closest to the object in the third lens group:
−0.5≦exp 123 /f 3 ≦0.7, and
exp 123 has a positive value when the exit pupil position is on an object side with respect to the surface closest to the object and has a negative value when the exit pupil position is on an image side with respect to the surface.
5. The relay optical system according to claim 4 , wherein
the relay optical system satisfies condition expressions below, where f 3-1 represents a focal length of the 3-1st lens group and f 3-2 represents a focal length of the 3-2nd lens group, R a represents a curvature radius of a surface closest to the object in the 3-1st lens group, R b represents a curvature radius of a surface closest to an image in the 3-1st lens group, and R c represents a curvature radius of a surface closest to the object in the 3-2nd lens group:
−0.8≦ f 3-1 /f 3-2 ≦−0.1
2≦ R b /R c ≦13
1.5≦ R b /R a ≦12, and
R a , R b and R c have positive values when the surface is a convex surface and have negative values when the surface is a concave surface.
6. The relay optical system according to claim 4 , wherein
the third lens group
consists of at least four lenses, and
includes a cemented lens.
7. The relay optical system according to claim 4 , wherein
the 3-1st lens group consists of in an order from an object side:
a lens with positive power that has Abbe number ν Ga , and
a lens with negative power that has Abbe number ν Gb , and
the relay optical system satisfies a condition expression below:
ν Ga −ν Gb ≧30.
8. The relay optical system according to claim 1 , wherein
a condition expression below is satisfied, where L 23 represents a length between the second lens group and the third lens group:
0.2≦ L 23 /f 12 ≦1.
9. The relay optical system according to claim 1 , wherein
a condition expression below is satisfied:
0.4≦ f 1 /f 12 ≦1.5.
10. A microscope apparatus comprising the relay optical system according to claim 1 .