| 摘要 |
PURPOSE:To secure a sufficiently short minimum photographic distance at a telephoto end and realize the shortest object distance of almost 0 m at a wide-angle end by specifying the movement quantity of a focusing lens element. CONSTITUTION:The conditions when the focusing lens element moves monotonously on the optical axis are so set as to satisfy expressions I and II. Here, A is the movement quantity of the focusing lens element at the time of focusing from an infinite-distance body to the closest body with optional focal length, B the movement quantity of the focusing lens element at the time of focusing from the infinite-distance body to the closest body at the wide-angle end, C the movement quantity of the focusing lens element from optional focal length to the wide-angle end at the time of zooming with the infinite body distance, and X a coefficient (fs: focal length of the whole system at the wide-angle and) when the closest body distance at the wide-angle end is represented as XfS. Consequently, while the sufficiently short minimum object distance at the telephoto end is secured, the minimum photographic distance at the wide-angle end is shortened almost to 0 m.
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