Wide-angle lens
AssigneeNidec Copal Corporation
InventorYasuhiko Abe
Life of this patent
Estimating the term…
Abstract
The present invention provides a high-performance, thin wide-angle lens suitable for imaging elements with high pixel counts. The wide-angle lens includes, from an object side to an image plane side: a first lens group including a first lens having a negative refractive power and a second lens having a positive refractive power; and a second lens group including a third lens having a negative refractive power, a fourth lens having a positive refractive power, and a fifth lens having a positive refractive power. The fourth lens is bonded to the third lens. The fifth lens is formed with at least one of its convex surfaces being an aspherical surface.
Claims19
A wide-angle lens comprising, from an object side to an image plane side:
- a first lens group comprising:
- a first lens having a negative refractive power, and
- a second lens having a positive refractive power;
- and
- a second lens group comprising:
- a third lens having a negative refractive power,
- a fourth lens having a positive refractive power, said fourth lens being bonded to said third lens, and
- a fifth lens having a positive refractive power, said fifth lens comprising a first convex surface oriented to said object side and a second convex surface oriented to said image plane side, at least one of said convex surfaces being an aspherical surface;
- wherein:
- (1) 0.7|R6|<|R8|<1.3|R6|
- (2) v1>v2, v3<v4, v5>50
- (3) |f1|>2 f2
- (4) 2.5 f22>f21>f22,
- where R6 is a curvature radius of an object-side surface of said third lens;
- R8 is a curvature radius of an image plane-side surface of said fourth lens;
- vi is an Abbe number of an i-th lens (i=1-5);
- f1 is a composite focal length of said first lens group;
- f2 is a composite focal length of said second lens group;
- f21 is a composite focal length of said third and said fourth lenses in said second lens group;
- f22 is a focal length of said fifth lens in said second lens group.
A wide-angle lens comprising, from an object side to an image plane side:
- a first lens group comprising:
- a first lens having a negative refractive power, and
- a second lens having a positive refractive power;
- and
- a second lens group comprising:
- a third lens having a negative refractive power,
- a fourth lens having a positive refractive power, said fourth lens being bonded to said third lens, and
- a fifth lens having a positive refractive power, said fifth lens comprising a first convex surface oriented to said object side and a second convex surface oriented to said image plane side, both of said convex surfaces being aspherical surfaces;
- wherein:
- (1) 0.7|R6|<|R8|<1.3|R6|
- (2) v1>v2, v3<v4, v5>50
- (3) f1>4 f2
- (4) 2.5 f22>f21>f22,
- where R6 is a curvature radius of an object-side surface of said third lens;
- R8 is a curvature radius of an image plane-side surface of said fourth lens;
- vi is an Abbe number of an i-th lens (i=1-5);
- f1 is a composite focal length of said first lens group;
- f2 is a composite focal length of said second lens group;
- f21 is a composite focal length of said third and said fourth lenses in said second lens group;
- f22 is a focal length of said fifth lens in said second lens group.
A method of producing a wide-angle lens, comprising the following steps:
- providing a first lens having a negative refractive power;
- providing a second lens having a positive refractive power;
- providing a third lens having a negative refractive power;
- providing an aperture stop between said second lens and said third lens;
- providing a fourth lens having a positive refractive power;
- bonding said third lens to said fourth lens;
- providing a fifth lens having a positive refractive power and at least one aspherical convex surface;
- providing a glass filter on an image plane side of said fifth lens;
- providing 0.7|R6|<|R8|<1.3|R6|;
- providing v1>v2, v3<v4, v5>50;
- providing |f1|>2 f2;
- providing 2.5 f22>f21>f22;
- and
- providing v6>v5;
- where R6 is a curvature radius of an object-side surface of said third lens;
- R8 is a curvature radius of an image plane-side surface of said fourth lens;
- vi is an Abbe number of an i-th lens (i=1-5);
- v6 is an Abbe number of said glass filter;
- f1 is a composite focal length of said first lens group;
- f2 is a composite focal length of said second lens group;
- f21 is a composite focal length of said third and said fourth lenses in said second lens group;
- f22 is a focal length of said fifth lens in said second lens group.
Dependencies are inferred from the claim text.