US 7,321,469 B2
Zoom lens
Kazunori Ohno, Saitama (Japan)
Assigned to Fujinon Corporation, Tokyo (Japan)
Filed on Nov. 14, 2006, as Appl. No. 11/598,695.
Claims priority of application No. P2005-328566 (JP), filed on Nov. 14, 2005; and application No. P2005-364891 (JP), filed on Dec. 19, 2005.
Prior Publication US 2007/0109662 A1, May 17, 2007
Int. Cl. G02B 15/14 (2006.01)
U.S. Cl. 359—682  [359/686; 359/753; 359/781] 10 Claims
OG exemplary drawing
 
1. A zoom lens comprising: a first lens of a negative lens; a second lens of a positive lens; an aperture stop; a third lens of a negative lens; and a fourth lens of a positive lens in this order from an object side of the zoom lens,
wherein a zooming operation of the zoom lens is performed by varying mutual distances among the first to fourth lenses, and
the zoom lens satisfies conditional expressions (1) to (4):
0.35<f2/f4<0.70  (1)
0.04<(dt−dw)/fw<0.40  (2)
1.65<f4/fw<2.20  (3)
50<νd1  (4)
wherein
f2 designates a focal length of the second lens;
f4 designates a focal length of the fourth lens;
dt designates a distance along an optical axis between the second lens and the third lens in a wide-angle end of the zoom lens;
dw designates a distance along the optical axis between the second lens and the third lens in a telephoto end of the zoom lens;
fw designates a focal length of a total system of the zoom lens in the telephoto end; and
νd1 designates an Abbe number of the first lens at the d-line.