Imaging lens comprising a diffractive optical surface
First Claim
1. An imaging lens for a solid-state image sensor in which lenses are arranged in order from an object side to an image side, comprising:
- an aperture stop;
a first lens as a meniscus lens with positive refractive power having a convex surface on the object side near an optical axis;
a second lens as a meniscus lens with positive refractive power having a convex surface on the image side near the optical axis;
a third lens as a meniscus lens with positive refractive power having a convex surface on the image side near the optical axis; and
a fourth lens as a meniscus lens with negative refractive power having a concave surface on the image side near the optical axis,wherein all lens surfaces are aspheric;
wherein all the lenses are made of plastic material;
wherein a diffractive optical surface is formed on at least one of lens surfaces from an image-side surface of the first lens to an image-side surface of the second lens;
wherein at least one of the three lenses with positive refractive power satisfies a conditional expression (1) below;
1.58<
Ndi
(1)whereNdi;
refractive index of the at least one of the three positive lenses at d-ray;
wherein a conditional expression (2) below is satisfied;
0.7<
TTL/(2IH)<
0.9
(2)whereTTL;
distance on the optical axis from the object-side surface of the first lens to an image plane (a total track length), andIH;
maximum image height;
wherein a conditional expression (3) below is satisfied;
0.7<
f1/f<
1.1
(3)wheref1;
focal length of the first lens, andf;
focal length of an overall optical system andwherein an F-value of the imaging lens falls in the range from 2.31 to 2.41.
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Accused Products
Abstract
An imaging lens includes, from the object side to the image side, an aperture stop, a first lens with positive refractive power having a convex object-side surface near an optical axis, a second lens with positive refractive power having a convex image-side surface near the axis, a third lens with positive refractive power having a convex image-side surface near the axis, and a fourth lens with negative refractive power having a concave image-side surface near the axis, wherein all lens surfaces are aspheric, all lenses are made of plastic material, a diffractive optical surface is formed on at least one of the lens surfaces from the first lens image-side surface to the second lens image-side surface, and at least one of the three positive lenses satisfies 1.58<Ndi where Ndi is the refractive index of the i-th positive lens at the d-ray.
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Citations
8 Claims
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1. An imaging lens for a solid-state image sensor in which lenses are arranged in order from an object side to an image side, comprising:
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an aperture stop; a first lens as a meniscus lens with positive refractive power having a convex surface on the object side near an optical axis; a second lens as a meniscus lens with positive refractive power having a convex surface on the image side near the optical axis; a third lens as a meniscus lens with positive refractive power having a convex surface on the image side near the optical axis; and a fourth lens as a meniscus lens with negative refractive power having a concave surface on the image side near the optical axis, wherein all lens surfaces are aspheric; wherein all the lenses are made of plastic material; wherein a diffractive optical surface is formed on at least one of lens surfaces from an image-side surface of the first lens to an image-side surface of the second lens; wherein at least one of the three lenses with positive refractive power satisfies a conditional expression (1) below;
1.58<
Ndi
(1)where Ndi;
refractive index of the at least one of the three positive lenses at d-ray;wherein a conditional expression (2) below is satisfied;
0.7<
TTL/(2IH)<
0.9
(2)where TTL;
distance on the optical axis from the object-side surface of the first lens to an image plane (a total track length), andIH;
maximum image height;wherein a conditional expression (3) below is satisfied;
0.7<
f1/f<
1.1
(3)where f1;
focal length of the first lens, andf;
focal length of an overall optical system andwherein an F-value of the imaging lens falls in the range from 2.31 to 2.41. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification