| 摘要 |
PROBLEM TO BE SOLVED: To provide a photographic optical system having extremely high power variation ratio, moreover which is small-sized and of high performance, and which can be easily manufactured. SOLUTION: The photographing optical system includes, in order from the side of an object to be photographed, a 1st lens group (G1) having positive power, a 2nd lens group (G2) having negative power, a 3rd lens group (G3) having positive power and a 4th lens group (G4) having positive power. Zooming is performed by using the 1st lens group (G1) to the 4th lens group (G4), and focusing is performed by using the 4th lens group (G4). If the focal distances of the photographing optical system as a whole at a wide-angle end and at a telephoto end are expressed as fw and ft, respectively, the focal distance of the 1st lens group (G1) is expressed as f1, the magnification of the 2nd lens group (G2) at the wide-angle end and at the telephoto end are expressed asβ2w andβ2t, respectively, the magnification of the 3rd lens group (G3) at the wide-angle end and at the telephoto end are expressed asβ3w andβ3t, respectively, the relations; 7.0≤f1/fw≤20.0, 0.38≤(β2t/β2w)/(ft/fw)≤0.8 and 1.1≤β3t/β3w≤4.0 are satisfied. COPYRIGHT: (C)2006,JPO&NCIPI
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