| 摘要 |
An imaging optical system which is a small-sized and wide angle of view a zoom lens, and whose aberration is finely corrected, is provided. In the imaging optical system, it has the first lens group of negative power, the second lens group of positive power, the third lens group of negative power, the fourth lens group of the positive and the following lens group, and the first lens group is fixed with respect to the image plane during zooming and focusing, and during zooming at least the lens group constituting the following lens group is moved within an adequate range, and the distance between the most image side surface of the following lens group and the image plane is set in an adequate range.
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