Patent ID: 7193793

Claim:
An imaging lens comprising, in sequence from an object side to an image plane side: a first lens with a convex surface facing said object side and an overall positive refractive power; an aperture stop forming an opening with a predetermined diameter; a second lens with a convex surface facing said object side and an overall positive refractive power; and a third lens with a concave surface facing said object side and an overall negative refractive power; wherein: said first lens having at least one of said object side surface and an image plane side surface formed as an aspherical surface; said third lens having both an object side and an image plane side surface are formed as aspherical surfaces, and an inflection point at which curvature orientation changes is positioned within an effective diameter range of said image plane side surface condition (1) below is met: 0.5< |R 1/ R 2|<2 (1) where R 1 is a curvature radius of said object side of said first lens and R 2 is a curvature radius of said image plane side of said first lens; and condition (2) below is met: D 23/ f< 0.1, D 5/ f< 0.2 (2) where f is a focal length of said lens system, D 23 is a distance along an optical axis between said first lens and said second lens, D 5 is a distance along said optical axis between said second lens and said third lens.