| 摘要 |
In five constituent lens groups, the fourth lens group from the object side is made as a negative lens. This fourth lens group is moved in order to correct zooming and focusing, while predetermined conditional expressions are satisfied, thereby yielding a zoom lens which can attain a wide angle, a large zoom ratio, and favorable aberrations. This zoom lens has five groups respectively composed of positive, negative, positive, negative, and positive lens groups. At the time of zooming, the first, third, and fifth lens groups G1, G3, and G5 are fixed, while the second and fourth lens groups G2 and G4 are made movable. As the second lens group G2 is moved in the optical axis direction, the focal length of the whole system is changed. As the fourth lens group G4 is moved in the optical axis direction, fluctuation in imaging position is corrected while change in the imaging position due to change in object distance is corrected. This zoom lens is further configured so as to satisfy the following conditional expressions (1) to (3): 0.9<fw(3+4)/(fwxft)+E,fra 1/2+EE <1.3 (1) 0.9<f5/(fwxft)+E,fra 1/2+EE <1.1 (2) 0.3<|f2|/(fwxft)+E,fra 1/2+EE <0.4 (3) wherein fw(3+4) is combined focal length of the third and fourth lens groups at a wide angle end thereof, fw is focal length of said zoom lens as a whole system at the wide angle end, ft is focal length of said zoom lens as a whole at a telephotographic end thereof, f5 is focal length of the fifth lens group, and f2 is focal length of the second lens group.
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