| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical system having a wide viewing angle, satisfactorily correcting aberration all over the image plane and easily obtaining high optical performance, and an imaging apparatus having the same. SOLUTION: The optical system is constituted of a first lens group immovable for focusing and a second lens group having an aperture diaphragm, moving for focusing and having positive refractive power in order from an object side to an image side. The first lens group includes a first-A lens group comprising only negative lenses, and a first-B lens group comprising a plurality of lenses, wherein a positive lens is positioned nearest to the object side, and having positive refractive power. The first-A lens group has three or more negative meniscus lenses turning concave surfaces to the image side, and at least one surface Ra1 out of the lens surfaces of the three or more negative lenses has aspherical shape. The Abbe numberνd and the partial dispersion ratioθgF of the material of at least one positive lens L1Bp out of the positive lenses included in the first-B lens group are properly set. COPYRIGHT: (C)2008,JPO&INPIT |
