| 摘要 |
PROBLEM TO BE SOLVED: To make a zoom lens thinner and smaller while ensuring its zooming ratio of nearly three times as large as the present ratio. SOLUTION: The zoom lens includes a first lens group I having negative refractive power, a second lens group II having positive refractive power, and a third lens group III having positive refractive power, and moves all the lens groups when zooming. The first lens group has a first lens 1 of a meniscus shape, the concave face of which is orientated in the direction of an image plane and the both faces of which are aspherical, and a second lens 2 of a meniscus shape, the convex face of which is oriented in the direction of an object. The second lens group has a third lens 3, the both faces of which are convex and aspherical, and a fourth lens 4 of a meniscus shape, the concave face of which is oriented in the direction of the image plane and the both faces of which are aspherical. The third lens group has a fifth lens 5, the both faces of which are convex and the image plane side face of which is aspherical. Without decreasing resolution, this configuration ensures a zooming ratio of nearly three times as large and shortens the overall length of a lens system to such a degree as that the zoom lens is made thinner particularly in a collapsed position. Accordingly, the entire length of the lens system when photographing can be shortened. COPYRIGHT: (C)2008,JPO&INPIT
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