| US 7,508,600 B2 | ||
| Optical system and optical apparatus including the same | ||
| Hideki Ogawa, Utsunomiya (Japan) | ||
| Assigned to Canon Kabushiki Kaisha, Tokyo (Japan) | ||
| Filed on Jun. 25, 2008, as Appl. No. 12/146,278. | ||
| Claims priority of application No. 2007-178129 (JP), filed on Jul. 06, 2007. | ||
| Prior Publication US 2009/0009890 A1, Jan. 08, 2009 | ||
| Int. Cl. G02B 9/14 (2006.01); G02B 15/14 (2006.01); G02B 9/12 (2006.01); G02B 3/02 (2006.01) | ||
| U.S. Cl. 359—785 [359/684; 359/689; 359/690; 359/784; 359/786; 359/716] | 7 Claims |
| 1. An optical system, comprising:
at least one of a movable lens unit movable in an optical axis direction and a fixed lens unit that is not movable in the
optical axis direction,
wherein the at least one lens unit includes a plurality of refractive optical elements, the refractive optical elements being
made of resin and having focal lengths of the same sign,
wherein, when Ngi, NFi, Ndi, and NCi indicate refractive indices, with respect to g-line, F-line, d-line, and C-line, respectively, of a material of the ith refractive optical element from an object side, an Abbe number νi, and a partial dispersion ratio θi of the material of the
ith refractive optical element are determined as follows:
νi=(Ndi−1)/(NFi−NCi)
θi=(Ngi−NFi)/(NFi−NCi), and
wherein the lens unit including the refractive optical elements has one or more negative lenses, and when φi is a refractive
power, with respect to d-line, of the ith refractive optical element, φG is a refractive power of one of the negative lenses that is made of a material having the highest
dispersion, and φa is an average refractive power for d-line of the refractive optical elements, the following conditions
are satisfied:
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