| 摘要 |
PROBLEM TO BE SOLVED: To provide a large-aperture medium telephoto lens where an actuator for focusing is arranged in a lens barrel, which has a high performance even in focusing, and its aberrations are satisfactorily corrected. SOLUTION: The large-aperture medium telephoto lens comprises: in order from an object side; a first lens group L1 having positive refractive power as a whole; and a second lens group L2 having positive refractive power as a whole. The first lens group L1 comprises, in order from the object side, at least two positive lenses, and a lens component whose lens surface nearest to an image side is concave on the image side and which has negative refractive power. The second lens group L2 comprises, in order from the object side; a second-a lens group L2a which has at least a positive lens component, a negative meniscus lens having a convex surface on the object side, and a negative lens component having a concave surface on the image side; a diaphragm; and a second-b lens group L2b which has positive refractive power. When focusing from an infinity object to a short-distance object, the second lens group L2 moves in an optical axis direction toward the object side, and the large-aperture medium telephoto lens satisfies a predetermined conditional expression. COPYRIGHT: (C)2011,JPO&INPIT
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