Imaging lens

An imaging lens comprising:

• a first lens having positive refractive power;
• a second lens having positive refractive power;
• and
• a third lens having negative refractive power, arranged in this order from an object side to an image plane side,
• wherein said first lens is formed in a shape so that both a surface thereof on the object side and a surface thereof on the image plane side have positive curvature radii,
• said second lens is formed in a shape so that a surface thereof on the image plane side has a negative curvature radius,
• said third lens is formed in a shape so that both a surface thereof on the object side and a surface thereof on the image plane side have positive curvature radii,
• said first lens has the refractive power P1, said second lens has the refractive power P2, said third lens has the refractive power P3, said second lens has the surface on the image plane side having the curvature radius R2r, and said third lens has the surface on the object side having the curvature radius R3f so that the following conditional expressions are satisfied,
• 35<(P1+P2)/|P3|<55
• −8<R2r/R3f<−3.