Imaging lens

1. An imaging lens comprising:

a first lens having positive refractive power;

a second lens having negative refractive power;

a third lens having negative refractive power;

a fourth lens having negative refractive power;

a fifth lens;

a sixth lens;

a seventh lens;

an eighth lens; and

a ninth lens having negative refractive power, arranged in this order from an object side to an image plane side,

wherein said second lens has a shape of a meniscus lens directing a convex surface thereof to the object side near an optical axis,

said ninth lens is formed in a shape so that a surface thereof on the image plane side has an aspherical shape having an inflection point, and

said imaging lens has a total of nine lenses.

2. The imaging lens according to claim 1 , wherein said first lens has a focal length f1 and said second lens has a focal length f2 so that the following conditional expression is satisfied:

−6< f 2/ f 1<−1.

3. The imaging lens according to claim 1 , wherein said second lens has a focal length f2 and said third lens has a focal length f3 so that the following conditional expression is satisfied:

4< f 3/ f 2<12.

4. The imaging lens according to claim 1 , wherein said ninth lens is formed in a shape so that a surface thereof on the image plane side has a paraxial curvature radius R9r so that the following conditional expression is satisfied:

0.2 <R 9 r/f <0.8,

where f is a focal length of a whole lens system.

5. The imaging lens according to claim 1 , wherein said ninth lens has a focal length f9 so that the following conditional expression is satisfied:

−3.5 <f 9/ f<− 0.2,

where f is a focal length of a whole lens system.