| 摘要 |
<p>There is provided a zoom optical system having lens elements produced with less difficulty i.e. with substantially the same skill level as the conventional arrangement, with sufficient miniaturization. The zoom optical system includes a first lens group having a negative optical power, and a second lens group having a positive optical power in the order from the object side, the distance between the first lens group and the second lens group being decreased in zooming from a wide angle end to a telephoto end. The first lens group is constituted of a negative lens element and a positive meniscus lens element. The second lens group is constituted of a biconvex positive lens element and a negative meniscus lens element. Assuming that D1 represents a thickness of the first lens group on the optical axis AX from a forwardmost lens surface to a rearmost lens surface, fw represents a composite focal length of the entirety of the optical system at the wide angle end, and f2 represents a composite focal length of the second lens group, the zoom optical system satisfies the following relation: 0.5 < D �¢ 1 / fw < 0.8 0.7 < f �¢ 2 / fw < 2.0</p> |
