| 摘要 |
A two-unit zoom lens system having a front lens unit of positive refractive power, and a rear lens unit of negative refractive power. The zoom lens system has a reduced number of constituent lens elements, and yet provides a zoom ratio of nearly 3 and favorable performance at reduced cost. The zoom lens system has a front lens unit (GF) of positive refractive power, and a rear lens unit (GR) of negative refractive power. Zooming is effected by varying the spacing between the two lens units. The front lens unit has a first lens component (GF1) of negative refractive power, and a second lens component (GF2) of positive refractive power. The first lens component includes no positive lens element, but has at least one aspherical surface. The second lens component includes a negative lens element and a positive lens element, which are disposed in the mentioned order. The zoom lens system satisfies at least the condition related to the focal length of the front lens unit, which must be satisfied to maintain a practical size of the lens system, and the condition related to the center thickness ratio between the negative and positive lens elements of the second lens component, which is concerned with the correction of axial chromatic aberration.
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