| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a zoom lens system with four lens groups of positive, negative, positive, and positive refractive power, having a variable-power ratio of approximately ten times, a field angle of 70 degrees or more at a short focal distance end, a front lens with a small diameter, and a short total lens length at the short focal distance end, and achieving excellent optical performance optimal for a collapsible camera. <P>SOLUTION: The zoom lens system comprises: in order from an object side, a first lens group G1 having a positive refractive power; a second lens group G2 having a negative refractive power; a third lens group G3 having a positive refractive power; and a fourth lens group G4 having a positive refractive power. During zooming from a wide angle end to a telephoto end, a distance between the first lens group and the second lens group increases, a distance between the second lens group and the third lens group decreases, and a distance between the third lens group and the fourth lens group changes. In the zoom lens system, the second lens group comprises three lenses which are, in order from the object side, a negative lens 21 concave toward the image side, a negative lens 22 concave toward the image side, and a plastic positive lens 23 convex toward the object side in which at least one lens surface is aspherical. <P>COPYRIGHT: (C)2013,JPO&INPIT |
