Imaging lens
AssigneeTokyo Visionary Optics Co., Ltd.
InventorsYoji Kubota, Kenichi Kubota, Hitoshi Hirano, Hisao Fukaya
Life of this patent
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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, arranged in this order from an object side to an image plane side. The fourth lens is formed in a meniscus shape at a paraxial region thereof. The fifth lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof. The sixth lens is formed in a meniscus shape at a paraxial region thereof. The first lens and the sixth lens have specific Abbe's numbers.
Claims11
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 meniscus shape at a paraxial region thereof,
- said fifth lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof,
- said sixth lens is formed in a meniscus shape at a paraxial region thereof, and
- said first lens has an Abbe's number ν1, said sixth lens has an Abbe's number ν6, and said
- second lens and said third lens have a composite focal length f23 so that the following conditional expressions are satisfied:
- 40<ν1<75,
- 10<ν6<40,
- 0.2<f23/f<1,
- where f is a focal length of a whole lens system.
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 second lens is formed in a shape so that a surface thereof on the object side and a surface thereof on the image plane side are convex at a paraxial region thereof,
- said third lens is formed in a shape so that a surface thereof on the object side is convex at a paraxial region thereof,
- said fourth lens is formed in a meniscus shape at a paraxial region thereof,
- said fifth lens is formed in a shape so that a surface thereof on the object side is convex 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 has a thickness T5 on an optical axis thereof, said sixth lens has a thickness T6 on an optical axis thereof, and said second lens and said third lens have a composite focal length f23 so that the following conditional expressions are satisfied:
- 0.05<D12/f<0.8,
- 0.5<T5/T6<3.5,
- 0.2<f23/f<1,
- where f is a focal length of a whole lens system.
Dependencies are inferred from the claim text.