US Patent 7688523 Image pickup lens

An image pickup lens is provided for forming an image of an object on a photoelectrical converter of a solid-state image pickup element. The image pickup lens includes, in order from an object side thereof: an aperture stop; a first lens having a positive refractive power; a second lens having a negative refractive power and including a concave surface facing an image side of the image pickup lens; a third lens including an aspheric surface; and a fourth lens including an aspheric surface. The image pickup lens satisfies predetermined conditions relating to a curvature radius of the surface of the second lens facing the image side and a refractive power of the third lens.