| 摘要 |
The present invention is directed to a photographing lens containing, in order from an object side: a first lens having a positive refractive power and a convex surface facing the object side; a second lens having a negative refractive power; a third lens having a positive refractive power; and a fourth lens having a negative refractive power and at least one aspheric surface, the photographing lens satisfying the following conditional expressions: <math-cwu id="MATH-US-00001"> <NUMBER>1</NUMBER> <MATH> <MTABLE> <MTR> <MTD> <MROW> <MFRAC> <MSUB> <MI>L</MI> <MI>T</MI> </MSUB> <MI>f</MI> </MFRAC> <MO>≤</MO> <MN>1.2</MN> </MROW> </MTD> </MTR> <MTR> <MTD> <MROW> <MN>0.5</MN> <MO>≤</MO> <MFRAC> <MSUB> <MI>f</MI> <MN>3</MN> </MSUB> <MI>f</MI> </MFRAC> <MO>≤</MO> <MN>1.0</MN> </MROW> </MTD> </MTR> </MTABLE> </MATH> <mathematica-file id="MATHEMATICA-00001" file="US20040136097A1-20040715-M00001.NB"/> <image id="EMI-M00001" wi="216.027" he="40.0869" file="US20040136097A1-20040715-M00001.TIF" imf="TIFF" ti="MF"/> </MATH-CWU> where LT denotes the distance on the optical axis between the object side of the first lens and the image side of the fourth lens; f denotes the total focal length of the photographing lens; and f3 denotes the focal length of the third lens.
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