Imaging lens and imaging device

An imaging lens comprising:

• a first lens having positive refractive power;
• a second lens having positive refractive power;
• and
• a third lens having positive refractive power, arranged in an order from an object side to an image plane side,
• wherein said first lens is formed in a shape so that a surface thereof on the object side is convex,
• said second lens is formed in a shape so that a surface thereof on the object side is concave and a surface thereof on the image plane side is convex,
• said third lens is formed in a shape so that a surface thereof on the object side is convex and a surface thereof on the image plane side is concave,
• said third lens is formed in the shape so that the surface thereof on the object side and the surface thereof on the image plane side are respectively formed as aspheric surfaces having inflexion points,
• said first lens has a focal length f1, said second lens has a focal length f2, and said third lens has a focal length f3 so that the following conditional expressions are satisfied:
• f1<f2
• 1.0<f1/f<1.5
• 0.7<f2/f3<1.2
• where f is a focal length of a whole lens system, and
• said first lens has the surface on the image plane side situated away from the surface of the second lens on the object side by a distance D12, and said second lens has the surface on the image plane side situated away from the surface of the third lens on the object side by a distance D23 so that the following conditional expression is satisfied:
• 0.2<D23/D12<1.2.