Patent ID: 7663807

Claim:
A microscope dry objective comprising, in order from an object side: a first lens unit with positive refracting power, having two meniscus lenses, each with a concave surface facing the object side, and at least one positive lens; a second lens unit with positive refracting power; and a third lens unit having concave surfaces adjacent and opposite to each other configured as air contact surfaces, wherein the following conditions are satisfied: 7≦ f 0.5<NA where f is a focal length, in millimeters, of the microscope dry objective and NA is a numerical aperture of the microscope dry objective on an entrance side, and wherein the second lens unit is movable along an optical axis so that a fluctuation of aberration produced in accordance with variation of a thickness of a nearly plane-parallel plate interposed between an observation object and the first lens unit is corrected.