| 摘要 |
PROBLEM TO BE SOLVED: To miniaturize a zoom lens with almost a triple variable power ratio, to be used for a miniaturized image pickup device such as video camera or digital still camera. SOLUTION: This zoom lens is composed of a first lens group G1 having positive refraction power, a second lens group G2 to move its position at the time of magnification while having negative refraction power and a third lens group G3 to move its position at the time of magnification while having positive refraction power successively from the side of an object to the side of an image surface. When the refraction factor of a lens composing of the first lens group G1 to the (d) ray (wavelength for 587.6 nm) is defined as nd(G1) and the Abbe number of the lens composing of the first lens group G1 to the (d) ray is defined asνd(G1), while turning the convex side of the first lens group G1 toward the object side, this zoom lens is composed of one lens having positive refraction power while satisfying the respective conditions of 1.62<nd(G1) and 45.0<νd(G1).
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