Gradient index lens component and image pickup apparatus using the gradient index lens component

Claim 2

A gradient index lens component composed of a single radial type gradient index lens element which has planar surfaces on both sides and a refractive index distribution expressed by the formula shown below and satisfying the following condition (1): n(r)=N.sub.0 +N.sub.1 r.sup.2 +N.sub.2 r.sup.4 + . . . and satisfying the following conditions (1) and (2): (1) -0.015<1/V 1 <0.015 (2) 1<t/f<3.5 wherein the reference symbol n(r) represents a refractive index of a portion of the gradient index lens element located at a distance r in a direction perpendicular to an optical axis, the reference symbol N 0 designates a refractive index of a portion of the gradient index lens element located on the optical axis, the reference symbols N 1 , N 2 , . . . denote refractive index distribution coefficients of the second, fourth, . . . orders respectively, and the reference symbol V 1 represents a coefficient expressing an Abbe's number of a medium which is given by the following formula: V.sub.1 =N.sub.1d /(N.sub.1F -N.sub.1C) wherein the reference symbols N 1d , N 1F and N 1C represent values of the refractive index distribution coefficient of the second order for the d-line, F-line and C-line respectively, and wherein the reference symbol f represents a focal length of said lens element, and the reference symbol t designates a thickness of said lens element.

Claim 3

A gradient-index lens component composed of a single radial type gradient index lens element which has planar surfaces on both sides and a refractive index distribution expressed by the formula n(r)=N.sub.0 +N.sub.1 r.sup.2 +N.sub.2 r.sup.4 + . . . and satisfying the condition -0.015<1/V 1 <0.15, and including an aperture stop which is disposed on or in the vicinity of an object side surface of said gradient lens element for restricting a light bundle, further satisfying the conditions 1<t/f<3.5 -0.2<f 4 ·N 2 <0.2 -2<d/t<0.5 wherein the reference symbol n(r) represents a refractive index of a portion of the gradient index lens element located at a distance r in a direction perpendicular to an optical axis, the reference symbol N 0 designates a refractive index of a portion of the gradient index lens element located on the optical axis, the reference symbols N 1 , N 2 , . . . denote refractive index distribution coefficients of the second, fourth, . . . orders respectively, and the reference symbol V 1 represents a coefficient expressing an Abbe's number of a medium which is given by the following formula: V.sub.1 =N.sub.1d /(N.sub.1F -N.sub.1C) wherein the reference symbols N 1d , N 1F and N 1C represent values of the refractive index distribution coefficient of the second order for the d-line, F-line, and C-line respectively, and the reference symbol f represents a focal length of said lens element, the reference symbol t designates thickness of said lens element and the reference symbol d denotes a distance as measured from the object side surface of said lens element to the aperture stop in a direction along the optical axis.

Claim 4

A gradient-index lens component composed of a single radial type gradient index lens element which has planar surfaces on both sides and a refractive index distribution expressed by the formula n(r)=N.sub.0 +N.sub.1 r.sup.2 +N.sub.2 r.sup.4 + . . . and satisfying the condition -0.015<1/V 1 <0.15, and including an aperture stop which is disposed on or in the vicinity of an object side surface of said gradient lens element for restricting a light bundle, further satisfying the conditions 1<t/f<3.5 -0.2<f 4 ·N 2 <0.2 -2<d/t<0.5 wherein the reference symbol n(r) represents a refractive index of a portion of the gradient index lens element located at a distance r in a direction perpendicular to an optical axis, the reference symbol N 0 designates a refractive index of a portion of the gradient index lens element located on the optical axis, the reference symbols N 1 , N 2 , . . . denote refractive index distribution coefficients of the second, fourth, . . . orders respectively, and the reference symbol V 1 represents a coefficient expressing an Abbe's number of a medium which is given by the following formula: V.sub.1 =N.sub.1d /(N.sub.1F -N.sub.1C) wherein the reference symbols N 1d , N 1F and N 1C represent values of the refractive index distribution coefficient of the second order for the d-line, F-line, and C-line respectively, and the reference symbol f represents a focal length of said lens element, the reference symbol t designates thickness of said lens element and the reference symbol d denotes a distance as measured from the object side surface of said lens element to the aperture stop in a direction along the optical axis.

Claim 5

A gradient index lens component composed of a single radial type gradient index element which has planar surfaces on both sides and a refractive index distribution expressed by the formula n(r)=N.sub.0 +N.sub.1 r.sup.2 +N.sub.2 r.sup.4 + . . . and including an aperture stop which is located on an object side of said radial type gradient index lens element and satisfying the following condition (1): (1) -0.015<1/V 1 <0.015 wherein the reference symbol n(r) represents a refractive index of a portion of the gradient index lens element located at a distance r in a direction perpendicular to an optical axis, the reference symbol N 0 designates a refractive index of a portion of the gradient index lens element located on the optical axis, the reference symbols N 1 , N 2 , . . . denote refractive index distribution coefficients of the second, fourth, . . . orders respectively, and the reference symbol V 1 represents a coefficient expressing an Abbe's number of a medium which is given by the following formula: V.sub.1 =N.sub.1d /(N.sub.1F -N.sub.1C) wherein the reference symbols N 1d , N 3F and N 1c represent values of the refractive index distribution coefficient of the second order for the d-line, F-line and C-line respectively.

Claim 6

A gradient index lens component composed of a single radial type gradient index element which has planar surfaces on both sides and a refractive index distribution expressed by the formula n(r)=N.sub.0 +N.sub.1 r.sup.2 +N.sub.2 r.sup.4 + . . . and including an aperture stop which is located on an object side of said radial type gradient index lens element and satisfying the following condition (1): (1) -0.015<1/V 1 <0.015 wherein the reference symbol n(r) represents a refractive index of a portion of the gradient index lens element located at a distance r in a direction perpendicular to an optical axis, the reference symbol N 0 designates a refractive index of a portion of the gradient index lens element located on the optical axis, the reference symbols N 1 , N 2 , . . . denote refractive index distribution coefficients of the second, fourth, . . . orders respectively, and the reference symbol V 1 represents a coefficient expressing an Abbe's number of a medium which is given by the following formula: V.sub.1 =N.sub.1d /(N.sub.1F -N.sub.1C) wherein the reference symbols N 1d , N 3F and N 1c represent values of the refractive index distribution coefficient of the second order for the d-line, F-line and C-line respectively.

Claim 7

A gradient index lens component composed of a single radial type gradient index element which has planar surfaces on both sides and a refractive index distribution expressed by the formula n(r)=N.sub.0 +N.sub.1 r.sup.2 +N.sub.2 r.sup.4 + . . . and including an aperture stop which is located inside of said radial type gradient index lens element and satisfying the following condition (1): 0.015<1/V.sub.1 <0.015 (1) wherein the reference symbol n(r) represents a refractive index of a potion of the gradient index lens element located at a distance r in a direction perpendicular to an optical axis, the reference symbol N 0 designates a refractive index of a portion of the gradient index lens element located on the optical axis, the reference symbols N 1 , N 2 , . . . denote refractive index distribution coefficients of the second, fourth, . . . orders respectively, and the reference symbol V 1 represents a coefficient expressing an Abbe's number of a medium which is given by the following formula: V.sub.1 =N.sub.1d /(N.sub.1F -N.sub.1C) wherein the reference symbols N 1d , N 1F and N 1C represent values of the refractive index distribution coefficient of the second order for the d-line, F-line and C-line respectively.

Claim 8

A gradient index lens component composed of a single radial type gradient index element which has planar surfaces on both sides and a refractive index distribution expressed by the formula n(r)=N.sub.0 +N.sub.1 r.sup.2 +N.sub.2 r.sup.4 + . . . and including an aperture stop which is located inside of said radial type gradient index lens element and satisfying the following condition (1): 0.015<1/V.sub.1 <0.015 (1) wherein the reference symbol n(r) represents a refractive index of a potion of the gradient index lens element located at a distance r in a direction perpendicular to an optical axis, the reference symbol N 0 designates a refractive index of a portion of the gradient index lens element located on the optical axis, the reference symbols N 1 , N 2 , . . . denote refractive index distribution coefficients of the second, fourth, . . . orders respectively, and the reference symbol V 1 represents a coefficient expressing an Abbe's number of a medium which is given by the following formula: V.sub.1 =N.sub.1d /(N.sub.1F -N.sub.1C) wherein the reference symbols N 1d , N 1F and N 1C represent values of the refractive index distribution coefficient of the second order for the d-line, F-line and C-line respectively.