Imaging lens

An imaging lens comprising:

• a first lens;
• a second lens;
• a third lens;
• a fourth lens;
• a fifth lens;
• a sixth lens;
• and
• a seventh lens, arranged in this order from an object side to an image plane side,
• wherein said sixth lens is formed in a shape so that a surface thereof on the image plane side and a surface thereof on the object side have positive curvature radii near an optical axis thereof,
• said seventh lens is formed in a shape so that a surface thereof on the image plane side has a positive curvature radius near an optical axis thereof,
• said seventh lens is formed in the shape so that the surface thereof on the image plane side is aspheric, and
• said fourth lens has a focal length f4 so that the following conditional expression is satisfied:
• 2<f4/f<15,
• where f is a focal length of a whole lens system.