| 摘要 |
PROBLEM TO BE SOLVED: To miniaturize and ensure a space around a diaphragm by applying a step zoom lens to a zoom lens for drawing such a zooming foundation locus which reduces the distance from the diaphragm, then expands the same again at the zooming of a first lens group from a wide angle end to a telephoto end. SOLUTION: This step zoom lens has, successively from an object side, the movable first lens group 11 having negative refracting power, the diaphragm 12 fixed in its position and a movable second lens group 13 having positive refracting power. The step zooming to stop the first lens group 11 and the second lens group 13 apart intervals on the zooming foundation locus is adopted and the focal length at which the spacing between the first lens group 11 and the diaphragm 12 is minimized on the zooming foundation locus and the point near the same are precluded from the stop focal length steps to prevent the stoppage thereof. It is practicable to dispose at least one each or more of the stop focal length steps before and behind the vertex of the zooming foundation locus at which the spacing between the first lens group 11 and the diaphragm 12 is minimized.
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