Importance

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Abstract

An apochromat-class immersion microscope objective having a magnification of about 40, a NA of about 1.0, and a satisfactorily flattened image field. The microscope objective includes a first lens unit G1 of positive refractive power which has a cemented lens composed of a plano-convex lens and a meniscus lens having a strong concave surface directed toward the object side, a second lens unit G2 having a cemented lens composed of three lens elements, that is, negative, positive and negative lenses, a third lens unit G3 having a cemented lens, a fourth lens unit G4 including a cemented meniscus lens having a strong concave surface directed toward the image side, and a fifth lens unit G5 including a cemented meniscus lens composed of a negative lens and a positive lens and having a strong concave surface directed toward the object side. The microscope objective satisfies conditions concerning the refractive index difference between the first and fifth lens units, the focal lengths of the first and fourth lens units, and the back focus of the entire system.

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First Claim