| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact zoom lens system where the number of lenses to be moved is restrained to the minimum without changing its entire length in the case of variable power, and whose aberration is satisfactorily corrected while making the lens to be moved small in size. SOLUTION: The zoom lens system is constituted of lenses of four groups having negative, positive, negative and positive power from an object side, and the lens of the 2nd group is a biconvex single lens having at least one aspherical surface, the lens of the 3rd group is a single lens having a concave surface on an image surface side, and the lens of the 4th group is a single lens. The lens system varies power by moving the lenses of the 2nd group and the 3rd group, and the difference of Abbe number between the 2nd group and the 3rd group is≥25. Furthermore, the lens system satisfies a following condition, 0.5≤¾F2/F3¾≤1.5, where F2 and F3 are the focal distances of the single lenses of the 2nd group and the 3rd group respectively. COPYRIGHT: (C)2006,JPO&NCIPI
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