| 摘要 |
This invention relates to a three-unit compact zoom lens system having a zoom ratio of about 2, whose telephoto ratio at the wide angle end is as short as 1.3 or lower and in which the lens diameter of the first lens unit is reduced. This zoom lens system comprises a first positive lens unit G1, a second positive lens unit G2 and a third negative lens unit G3, and in zooming from the wide angle to telephoto end, the first and third lens units are movable toward the object side and the second lens unit is movable toward the object side at a speed relatively lower than that at which the first and third lens units are moved. Furthermore, the present zoom lens system satisfies the following condition: 0.5<|f3/fW|<0.9, (1) 1.3< beta 3W<2.0, (2) 1.7<f1/fW<5.0, (3) and 0.5<f2/fW<1.3. (4) Here fW is the focal length of the total system at the wide angle end f1, f2 and f3 are the focal lengths of the first, second and third lens units, respectively, and beta 3W is the image-formation magnification of the third lens unit.
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