| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain a zoom lens having a wide field angle, a high zoom ratio and high optical performance over the entire zoom range, and an imaging device having this zoom lens. <P>SOLUTION: A zoom lens comprises four lens groups of positive, negative, positive, and positive refractive powers in this order from an object side to an image side. In the zoom lens, the second and fourth lens groups are moved in zooming. The first lens group is composed of a 1a-th lens group of negative refractive power and a 1b-th lens group of positive refractive power in this order from an object side to an image side. The 1a-th lens group is composed of two or more negative lenses that are concave on the image side, and one or more positive lenses. The 1b-th lens group is composed of three or more positive lenses, one or more negative lenses or two or more positive lenses, and a cemented lens consisting of a negative lens and a positive lens. The focal distances f1a, f1 of the 1a-th lens group and the first lens group, and the radius of curvature R1bF of the object side of the negative lens of the 1b-th lens group are appropriately set. <P>COPYRIGHT: (C)2012,JPO&INPIT |
