Patent ID: 9134506
Filing Date: 2015-09-15
Classification: G02B

Abstract:
1. An imaging lens comprising: a first lens having positive refractive power; a second lens having negative refractive power; a third lens having negative refractive power; a fourth lens having positive refractive power; and a fifth lens having negative refractive power, arranged in this order from an object side to an image plane side, wherein said first lens is formed in a shape so that a surface thereof on the object side has a positive curvature radius and a surface thereof on the image plane side has a negative curvature radius, said second lens is formed in a shape so that a surface thereof on the object side has a negative curvature radius, said third lens is formed in a shape so that a surface thereof on the object side and a surface thereof on the image plane side have positive curvature radii, and the surface thereof on the image plane side is formed in an aspheric shape having an inflexion point, said fourth lens is formed in a shape so that a surface thereof on the object side and a surface thereof on the image plane side have negative curvature radii, said fifth lens is formed in a shape so that a surface thereof on the object side has a negative curvature radius and a surface thereof on the image plane side has a positive curvature radius, and said first lens has an Abbe's number νd1, said second lens has an Abbe's number νd2, said third lens has an Abbe's number νd3, and said fourth lens and said fifth lens have a composite focal length f45 so that the following conditional expressions are satisfied: where f is a focal length of a whole lens system.