Patent ID: 8385011

Claim:
An image pickup lens comprising, in order from an object side thereof: a first lens block with a positive refractive power, comprising a first lens substrate being a parallel flat plate, and lens portions 1 a and 1 b arranged on an object side surface and an image side surface of the first lens substrate, each of the lens portions 1 a and 1 b being different from the first lens substrate in at least one of a refractive index and an Abbe number; a second lens block with a negative refractive power, comprising a second lens substrate being a parallel flat plate, and lens portions 2 a and 2 b arranged on an object side surface and an image side surface of the second lens substrate, each of the lens portions 2 a and 2 b being different from the second lens substrate in at least one of a refractive index and an Abbe number; and an aperture stop arranged on the first lens substrate, wherein the image pickup lens has in total a two-lens-block structure, the lens portion 1 a is arranged on the object side surface of the first lens substrate, an object side surface of the lens portion 1 a is a convex surface facing the object side, the lens portion 1 b is arranged on the image side surface of the first lens substrate, an image side surface of the lens portion 1 b is a concave surface facing an image side, the lens portion 2 a is arranged on the object side surface of the second lens substrate, an object side surface of the lens portion 2 a is a concave surface facing the object side, the lens portion 2 b is arranged on the image side surface of the second lens substrate, an image side surface of the lens portion 2 b is in an aspheric shape, and the image pickup lens satisfies the following expressions: 1.55<N2b<2.0, 1.74 <D[BK 2 ]/D[BK 1]<3.0, where N2b is a refractive index of the lens portion 2 b at d line, D[BK 1 ] is a composite thickness of the first lens block, and D[BK 2 ] is a composite thickness of the second lens block.