| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens which satisfactorily corrects various aberrations accompanying zooming while making a whole lens system small-sized and has good optical performance over the whole screen, by which large screen projection can be realized at a short projection distance and further high variable magnification can be easily realized, and which has a long back-focus. SOLUTION: The zoom lens is provided with a plurality of lens groups including a 1st lens group which is arranged at a foremost side and has negative optical power and zooming is carried out by moving two or more lens groups among the plurality of lens groups in an optical axis direction. The 1st lens group is fixed during zooming and a 1st lens arranged at a foremost side among the 1st lens group has negative refractive power and satisfies conditions:νdn < 32 ... (1), 0.008 <θg, Fn-(0.644-0.00168×νdn)< 0.040 ... (2), ¾f1/bf¾ < 0.9 ... (3), wherein (vdn) denotes Abbe's number of a material of the 1st lens, (θg, Fn) denotes a partial dispersion ratio, (f1) denotes focal distance of the 1st lens group and (bf) denotes air converted back focus when being focused to an infinite object. COPYRIGHT: (C)2006,JPO&NCIPI
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