| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a zooming lens which has a large aperture ratio as well as a wide angle of view with a small light incident angle and can obtain high optical performance. <P>SOLUTION: A zoom lens comprises: in an order from an object side to an image side, a first lens group having negative refractive power; a second lens group having positive refractive power including an aperture diaphragm; and a third lens group having the positive refractive power. The first, the second and the third lens groups move during zooming and the third lens group moves during focusing. The second lens group has, from the object side to the image side, two or more positive lenses and one or more negative lens. The zoom lens also satisfies the following conditional expressions: 0.20<Fnow*fw/f3<0.43 and 0.4<BFt*Fnot/ft<0.9, where f3 is a focal distance of the third lens group, fw and fw are respectively the focal distances of an entire system at a wide angle end as well as a telephoto end, Fnow and Fnot are respectively F numbers at the wide angle end as well as the telephoto end, and BFt is an air conversion distance from a final lens surface to an image surface. <P>COPYRIGHT: (C)2013,JPO&INPIT |
