| 摘要 |
The zoom lens comprises, in order from an object side: a first lens group having a negative refractive power, the first lens group including a first lens having a negative refractive power, and a second lens having a positive refractive power; a second lens group having a positive refractive power, the second lens group including a third lens having a positive refractive power, and a fourth lens having a negative refractive power; and a third lens group having a positive refractive power, the third lens group including a fifth lens having a positive refractive power, the zoom lens satisfying the following conditional expression: <math-cwu id="MATH-US-00001"> <NUMBER>1</NUMBER> <MATH> <MROW> <MROW> <MO>-</MO> <MN>3.0</MN> </MROW> <MO><</MO> <MFRAC> <MSUB> <MI>f</MI> <MN>1</MN> </MSUB> <MSUB> <MI>f</MI> <MI>w</MI> </MSUB> </MFRAC> <MO><</MO> <MROW> <MO>-</MO> <MN>2.0</MN> </MROW> </MROW> </MATH> <mathematica-file id="MATHEMATICA-00001" file="US20040257671A1-20041223-M00001.NB"/> <image id="EMI-M00001" wi="216.027" he="18.96615" file="US20040257671A1-20041223-M00001.TIF" imf="TIFF" ti="MF"/> </MATH-CWU> where f1 denotes the focal length of the first lens group; and fw denotes the total focal length at a wide-angle position.
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