| 摘要 |
PURPOSE:To reduce a collapse of an aberration at the time of proximity photographing by moving along an optical axis a lens group of an object side from a diaphragm, of plural lens groups for constituting an objective lens. CONSTITUTION:By feeding out the whole lens group along the optical axis, a camera lens for executing a focusing is divided into lens groups d1-d7 before a diaphragm, and lens groups d9-d12 behind the diaphragm, along the optical axis. When it is tried to correct a distortion of an image at the time of proximity photographing by moving the front group or both groups, the feed-out quantity becomes large, therefore, the rear group is moved. In case of a Gauss type lens system, a power of a cemented lens just behind the diaphragm is small, therefore, even if this lens is moved, a focal distance and a principal paint position are scarcely varied, and an increase of the feed-out quantity is small. As for this lens, it is desirable from the viewpoint of a comatic aberration to have a convex surface. |
