| 摘要 |
PROBLEM TO BE SOLVED: To obtain a zoom lens in which an optical system as a whole is small-sized, has a wide field angle and a high zoom ratio, and which can obtain high optical performance over the entire zoom range. SOLUTION: The zoom lens includes, in the order from an object side to an image plane side, a first lens group of positive refractive power, a second lens group of negative refractive power, a diaphragm, a third lens group of positive refractive power, a fourth lens group of negative refractive power, and a fifth lens group of positive refractive power. When zooming from a wide-angle end to a telephoto end is carried out, the first lens group moves toward an image plane side, while drawing a projecting locus so that the interval between the first and second lens groups becomes larger and the interval between the second and third lens groups becomes smaller at the telephoto end than that at the wide-angle end. The second lens group moves toward the image plane side. The diaphragm moves so that the interval between the diaphragm and the third lens group more decreases at the telephoto end than that at the wide-angle end. The zoom lens respectively and appropriately sets the focal distance f4 of the fourth lens group, the focal distance ft of the system as a whole at the telephoto end, a moving amount m1 of the first lens group in a direction of the optical axis at the telephoto end relative to the wide angle end, and a moving amount m1mid of the first lens group in the direction of an optical axis from the wide-angle end to the zooming position, in which the first lens group is located to a side closest to the image plane. COPYRIGHT: (C)2011,JPO&INPIT
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