| 摘要 |
PROBLEM TO BE SOLVED: To provide a macro lens having excellent aberration performance in all the photographing range to infinity from a short distance where photographing magnification is almost unmagnified, and an optical device and a focusing method for the macro lens. SOLUTION: The macro lens comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power in order from an object side, and performs focusing by moving the respective lens groups G1, G2 and G3 in an optical axis direction so that space between the first lens group G1 and the second lens group G2 may be increased. The first lens group G1 includes at least two positive lenses turning their convex surfaces to the object side and a negative lens succeeding to at least two positive lenses in order from the object side, and the third lens group G3 includes at least one positive lens arranged nearest to the object side and a negative lens in order from the object side. COPYRIGHT: (C)2008,JPO&INPIT
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