Patent ID: 8400718

Claim:
An image pickup lens comprising: an aperture stop; a first lens; and a second lens, the aperture stop, the first lens, and the second lens being sequentially arranged along a direction from a subject to an image surface with no intervening optical elements, the first lens having a convex surface facing the subject, the second lens having a surface facing the subject, the surface including a central portion sticking out toward the subject and a peripheral portion surrounding the central portion and sinking in toward the image surface, said image pickup lens satisfying mathematical expression (1): 0.340< d 1/ d< 0.45 (1), where d 1 is the length of a segment between the center of that surface of the first lens which faces the subject and the center of that surface of the first lens which faces the image surface and d is the whole optical length of the image pickup lens, the whole optical length d of the image pickup lens being a direct distance along an optical axis of the image pickup lens from the image surface to that portion of a place (A) or (B) which is closest to the subject, (A) indicating a place along the optical axis that corresponds to the location of the aperture stop, (B) indicating a place in the first lens where light enters, said image pickup lens further satisfying mathematical expression (2): 1.30< f 1/ f< 3.00 (2), where f is the focal length of the image pickup lens as a whole and f 1 is the focal length of the first lens.