| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens made compact, having a variable power ratio of about two, having high optical performance all over the variable power area and constituted of two lens groups of negative preceding type. SOLUTION: A 2nd lens group G2 has a lens constituted of lenses 2a and 2b whose synthetic refractive power is positive, a lens 2c whose surface on an object side is concave and which has 2nd negative refractive power, and a lens 2d whose surface on the object side is convex and which has 2nd positive refractive power. Then, both surfaces of a lens 1b, both surfaces of the lens 2c and the surface on the object side of the lens 2d are constituted of aspherical surfaces. Assuming that the focal distance of the 1st lens group G1 is f1, the focal distance of the 2nd lens group G2 is f2, the focal distance at a wide angle end is (fw) and the focal distance at a telephoto end is (ft), the zoom lens satisfies conditions, 2.5<¾f1/fw¾<4 and 0.6<¾f2/ft¾<1.2. COPYRIGHT: (C)2005,JPO&NCIPI
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