| US 7,580,202 B2 | ||
| Zoom lens system and image pickup apparatus including the same | ||
| Ken Wada, Shioya-gun (Japan) | ||
| Assigned to Canon Kabushiki Kaisha, Tokyo (Japan) | ||
| Filed on Aug. 11, 2008, as Appl. No. 12/189,275. | ||
| Claims priority of application No. 2007-230011 (JP), filed on Sep. 05, 2007. | ||
| Prior Publication US 2009/0059387 A1, Mar. 05, 2009 | ||
| Int. Cl. G02B 15/14 (2006.01) | ||
| U.S. Cl. 359—689 [359/686; 359/690] | 13 Claims |
| 1. A zoom lens system, in order from an object side to an image side, comprising:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power; and
a subsequent lens-unit set including at least one lens unit,
wherein intervals between the first lens unit, the second lens unit, and the lens units included in the subsequent lens-unit
set change during zooming,
wherein the first lens unit includes a negative lens element, an optical element, and a positive lens element, and
wherein the following conditional expressions are satisfied,
0.755<θgF−(−1.665×10−7·νn3+5.213×10−5·νn2−5.656×10−3·νn)<1.011
0.023<|f1/(f1n·ν1n)|<0.050
3.2<β3it/β3iw<6.0
where νn and θgF denote an Abbe number and a partial dispersion ratio, respectively, of a material composing the optical element;
f1n and ν1n denote a focal length of the negative lens element and an Abbe number of a material composing the negative lens element, respectively;
f1 denotes a focal length of the first lens unit; and β3iw and β3it denote lateral magnifications of the subsequent lens-unit set at a wide-angle end and at a telephoto end, respectively.
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