Objective lens system
AssigneeNikon Corporation
InventorsHiroshi Yamada, Yutaka Suenaga, Itoe Ito
Life of this patent
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Abstract
This invention relates to a microscope objective lens system a part of which is immersed in a liquid to observe a sample present in the liquid. Particularly, this invention provides an apochromat-grade microscope objective lens system which can be machined cheaply and easily by the conventional technology, which is well corrected for chromatic aberration, and which is excellent in flatness of the image plane. This objective lens system has a plane-parallel plate on the most sample side, is constructed without using an embedded lens as used in the conventional objectives, and can take a variety of lens layouts.
Claims11
An objective lens system comprising, in order from an object side to an image side:
- a first lens group having a plane-parallel plate having two surfaces substantially parallel to each other and a cemented lens with a concave surface facing said object side, said first lens group having a negative refractive power;
- a second lens group having a positive refractive power;
- and
- a third lens group having a positive refractive power;
- which satisfies the following conditions:
- .vertline.(N1a.multidot.F)/r1.vertline..ltoreq.0.13
- .vertline.(N1a.multidot.F)/r2.vertline..ltoreq.0.13
- 0.16<.vertline.r3/N1b.multidot.F).vertline.<0.2
- 2<f3/F<3.5
- where F is a composite focal length of the overall objective lens system, f3 a focal length of said third lens group, r1 a radius of curvature of the object-side surface of said plane-parallel plate, r2 a radius of curvature of the image-side surface of said plane-parallel plate, r3 a radius of curvature of the object-side concave surface of the cemented lens in said first lens group, N1a a refractive index of said plane-parallel plate, and N1b a refractive index of a most-object-side lens in the cemented lens in said first lens group.
Dependencies are inferred from the claim text.