Imaging lens
AssigneeTokyo Visionary Optics Co., Ltd.
InventorsYoji Kubota, Kenichi Kubota, Hitoshi Hirano, Hisao Fukaya
Life of this patent
Estimating the term…
Abstract
An imaging lens includes a first lens having negative refractive power; an aperture stop; a second lens; a third lens; a fourth lens; a fifth lens; and a sixth lens having negative refractive power, arranged in this order from an object side to an image plane side. The fourth lens is formed in a shape so that a surface thereof on the image plane side is convex at a paraxial region thereof and has an aspheric shape having an inflection point. The fifth lens is formed in a shape so that a surface thereof on the image plane side is concave at a paraxial region thereof.
Claims17
An imaging lens comprising:
- a first lens having negative refractive power;
- an aperture stop;
- a second lens;
- a third lens;
- a fourth lens;
- a fifth lens;
- and
- a sixth lens having negative refractive power, arranged in this order from an object side to an image plane side,
- wherein said fourth lens is formed in a shape so that a surface thereof on the image plane side is convex at a paraxial region thereof,
- said fourth lens is formed in the shape so that the surface thereof on the image plane side has an aspheric shape having an inflection point, and
- said fifth lens is formed in a shape so that a surface thereof on the image plane side is concave at a paraxial region thereof, wherein said second lens has a focal length f2 and said third lens have a focal length f3 so that the following conditional expression is satisfied:
- 0.5<f2/f3<3.
An imaging lens comprising:
- a first lens having negative refractive power;
- an aperture stop;
- a second lens;
- a third lens;
- a fourth lens;
- a fifth lens;
- and
- a sixth lens, arranged in this order from an object side to an image plane side,
- wherein said fourth lens is formed in a shape so that a surface thereof on the image plane side is convex at a paraxial region thereof,
- said fourth lens is formed in the shape so that the surface thereof on the image plane side has an aspheric shape having an inflection point,
- said fifth lens is formed in a shape so that a surface thereof on the image plane side is concave at a paraxial region thereof, and
- said first lens is disposed away from the second lens by a distance D12 on an optical axis thereof and said fifth lens is disposed away from the sixth lens by a distance D56 on an optical axis thereof, and said second lens has a focal length f2 and said third lens has a focal length f3 so that the following conditional expressions are satisfied:
- D56<D12,
- 0.5<f2/f3<3.
Dependencies are inferred from the claim text.