| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens which has an F-number of about 2.0 at a variable magnification ratio of about 8 times, is well corrected of various aberrations and is excellent in manufacturability. SOLUTION: The zoom lens is a lens system consisting, successively from an object side, of a first group which has positive refractive power and is fixed at the time of variable magnification, a second group which has negative refractive power and moves back and forth on the optical axis for the purpose of variable magnification, a third group which has positive refractive power and is fixed at the time of variable magnification, a fourth group which has positive refractive power and moves back and forth on the optical axis for the purpose of correcting the movement of a focal position, and a fifth group which has negative refractive power and is fixed at the time of the variable magnification. In the above lens system, the third group or the fifth group which is fixed at the time of the variable magnification is provided with at least one aspherical surface and all the lenses of the fourth group consist of spherical surfaces. COPYRIGHT: (C)2005,JPO&NCIPI
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