| 摘要 |
An apochromatic microscope objective of high NA wherein variation of aberrations, including chromatic aberration, caused by a change in the cover glass thickness, is minimized with a relatively simple arrangement. The microscope objective has a 1-st lens unit (G1) which includes a positive meniscus lens having a concave surface directed toward the object side to convert a bundle of rays from an object into a convergent bundle of rays, a 2-nd lens unit (G2) having a negative refractive power, and a 3-rd lens unit (G3) having a small refractive power. The 2-nd lens unit (G2) is movable relative to the 1-st and 3-rd lens units (G1 and G3) along the optical axis in accordance with a change in thickness of a transparent plane-parallel plate disposed between the 1-st lens unit (G1) and the object. The microscope objective satisfies conditions concerning the curvature radius of a lens surface in the 1-st lens unit (G1) that is the closest to the object side and the focal lengths of the 2-nd and 3-rd lens units (G2 and G3).
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