| 摘要 |
PROBLEM TO BE SOLVED: To provide a wide-angle zoom lens able to achieve a wide angle (e.g., an angle of field at the wide angle end is 70°or greater) while preventing an increase in the size of the first and the second groups. SOLUTION: The zoom lens includes, in order from the object side, a first group 10 of positive refractive power, a second group 20 of negative refractive power, stop St, a third group 30, and a fourth group 40 of positive refractive power. To zoom from the wide angle end to the telephoto end, the first and the third groups 10 and 30 are fixed, and the second group 20 is moved to the image side along an optical axis. Also, an image plane correction and focusing due to the zooming operation are carried out by moving the fourth group 40 along the optical axis. The second group 20 has, in order from the object side, at least a negative twenty-first lens L21 having a concave face whose curvature radius on the image side is smaller than that on the object side, and a positive twenty-second lens L22. At least one face of the twenty-first lens L21 is aspherical. COPYRIGHT: (C)2009,JPO&INPIT
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