| 摘要 |
<p>A zoom lens comprises first and fourth units which don't move for zooming, and second and third units moved during zooming. The first unit includes a front side partial unit which don't move for focusing, a movable partial unit moved for focusing, and a rear side partial unit which don't move for focusing, the rear side partial unit includes positive lenses and one or more negative lenses, and the following conditions are satisfied: -1.2 × 10-3 < (¸pa - ¸n)/(½pa - ½n), and ½n < 30, where ½n is the smallest Abbe number of the material of the negative lenses, ¸n is the partial dispersion ratio of the material of the negative lens of the smallest Abbe number, ½pa is the average of the Abbe numbers ½ of the materials of positive lenses, and ¸pa is the average of the partial dispersion ratio ¸ of the materials of the positive lenses.</p> |
