| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom optical system with good optical performance and a vibration-proof function even at blurring correction, an optical instrument incorporating the zoom optical system, and to provide a zoom method of the zoom optical system. SOLUTION: The zoom optical system ZL incorporated in an electronic still camera 1 or the like includes a first lens group G1 having a positive refracting power, a second lens group G2 having a negative refracting power, a third lens group G3 having a positive refracting power, a fourth lens group G4 having a negative refracting power, and a fifth lens group G5 having a positive refracting power, in the order from the object side, and it is configured to implement blurring correction by moving the fourth lens group in directions orthogonal to the optical axis. The fourth lens group G4 is composed of a cemented lens of a negative lens and a positive lens with a convex surface on the object side in the order from the object side. The fourth lens group includes a zoom optical system that satisfies a condition of the following expression: vp>30.0, where vp is an Abbe number of the positive lens. COPYRIGHT: (C)2009,JPO&INPIT
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