| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens that obtains a wide angle of view and high variable power ratio while ensuring a long back focus. 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, a stop St, a third group 30 of negative refractive power, 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 toward the image side along its optical axis. The correction of an image plane and focus due to the zooming operation are made by moving the fourth group 40 along the optical axis. The third group 30 has two positive lenses L31 and L32, and two negative lenses L33 and 34. COPYRIGHT: (C)2009,JPO&INPIT
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