Imaging lens including seven lenses of +--+0+, +--+-+-, +---+- or +--++- refractive powers

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

• a first lens with positive refractive power having a convex object-side surface in a paraxial region,
• a second lens with negative refractive power in a paraxial region,
• a third lens with negative refractive power in a paraxial region,
• a fourth lens with positive or negative refractive power in a paraxial region,
• a fifth lens,
• a sixth lens with positive refractive power in a paraxial region, and
• a seventh lens with negative refractive power having a concave image-side surface in a paraxial region, wherein the following conditional expressions (1), (2), (3), and (4) are satisfied:
• 0.55<vd2/vd3<1.50 (1)
• 0.30<r2/f<2.70 (2)
• 1.85<|r13|/f (3)
• 0.65<T2/T4<3.00 (4)
• where
• vd2:
• an abbe number at d-ray of the second lens,
• vd3:
• an abbe number at d-ray of the third lens,
• r2:
• a paraxial curvature radius of an image-side surface of the first lens,
• f:
• a focal length of the overall optical system of the imaging lens,
• r13:
• a paraxial curvature radius of an object-side surface of the seventh lens,
• T2:
• a distance along an optical axis from an image-side surface of the second lens to an object-side surface of the third lens, and
• T4:
• a distance along an optical axis from an image-side surface of the fourth lens to an object-side surface of the fifth lens.