Imaging lens comprising seven lenses of +−+−−+− or +++−−+− refractive powers

An imaging lens comprising in order from an object side to an image side,

• a first lens with positive refractive power in a paraxial region,
• a second lens with positive refractive power in a paraxial region,
• a third lens with positive refractive power in a paraxial region having an object-side surface being convex and an image-side surface being convex in the paraxial region,
• a fourth lens,
• a fifth lens with negative refractive power in the paraxial region,
• a sixth lens with positive refractive power in the paraxial region, and
• a seventh lens with negative refractive power in the paraxial region having an object-side surface being concave in the paraxial region and an image-side surface that is concave in the paraxial region and is formed as an aspheric surface having at least one pole point in a position off the optical axis,
• wherein the first lens to the seventh lens are single lenses, respectively,
• an object-side surface of the fifth lens is convex in the paraxial region and has at least one pole point in a position off the optical axis, and
• an image-side surface of the fifth lens is concave in the paraxial region and is formed as an aspheric surface having at least one pole point in a position off the optical axis, an object-side surface of the sixth lens is convex and is formed as an aspheric surface having at least one pole point in a position off the optical axis, and an image-side surface of the sixth lens is convex in the paraxial region, and the following conditional expression (1) is satisfied:
• 1.8<νd3/νd4<4.0 (1)
• where
• νd3:
• an abbe number at d-ray of the third lens, and
• νd4:
• an abbe number at d-ray of the fourth lens.