| 摘要 |
A small-sized zoom lens is disclosed comprising, from front to rear, a first lens unit of positive refractive power and a second lens unit of negative refractive power, zooming being performed by varying the separation between the first and second lens units, wherein the first lens unit has a negative lens and at least two positive lens, the second lens unit has a first lens and a negative second lens having a concave surface facing the object side, and the second lens unit has at least one aspheric surface, and wherein proper rules of lens design are set forth for the focal lengths f1 and f2 of the first and second lens units, the shortest focal length fw of the entire system, the refractive index N2F and Abbe number nu 2F of the material of the first lens, and the focal lengths f2F and f2R of the first and second lenses.
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