Kantatsu Co., Ltd.

Hisanori Suzuki

Kazuo Matsuoka

Yukio Sekine

Shingo Watanabe

Ichiro Kurihara

Kenichi Kamada

An imaging lens includes, from an object side to an image side: a first positive lens having a convex object-side surface; an aperture stop; a second negative lens as a meniscus double-sided aspheric lens having a concave object-side surface; and a third positive lens as a meniscus double-sided aspheric lens having a concave image-side surface, wherein the second lens has a diffractive optical surface on the object side, the aspheric object-side and image-side surfaces of the third lens have pole-change points off an optical axis, and conditional expressions (1) to (4) below are satisfied:8.0&#x3c;&#x3c;26.0&#x2003;&#x2003;(1)20&#x3c;1&#x2212;2&#x3c;40&#x2003;&#x2003;(2)20&#x3c;3&#x2212;2&#x3c;40&#x2003;&#x2003;(3)0.8&#x3c;&#x3c;0.95&#x2003;&#x2003;(4).

Imaging lens

A compact imaging lens suitable for a high pixel density image pickup device which properly corrects chromatic aberration and other types of aberrations and ensures high image quality, low f-number, and low cost. A first lens, second lens, third lens, fourth lens, and fifth lens are arranged in order from the object side and both sides of all the lenses are aspheric surfaces and a diffractive optical surface with a chromatic aberration correction function is formed on one of the surfaces from the object side surface of the first lens to the object side surface of the second lens and on one of the surfaces from the object side surface of the third lens to the object side surface of the fifth lens. All the lenses are made of a plastic material.

Designed for a solid-state image sensor, it includes, in order from an object side to an image side: a first positive lens having a convex object-side surface; a second negative lens having a concave image-side surface; a third positive meniscus lens having a convex image-side surface; and a fourth negative lens having concave object-side and image-side surfaces near an optical axis. A first diffraction optical surface is formed on one lens surface of the first to third lenses, and a second one is formed on the fourth lens object-side surface. The imaging lens satisfies a conditional expression below,0.0&#x3c;6/7&#x3c;0.1,

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&#x3c;Ndi where Ndi is the refractive index of the i-th positive lens at the d-ray.

Imaging lens comprising a diffractive optical surface

To provide a high image-quality, low cost, and small sized imaging lens suitable for an imaging lens which is compact and which has high density pixels, and with aberrations corrected satisfactorily. An imaging lens is configured from a first lens, a second lens, a third lens, and a fourth lens arranged in the named order from an object side, wherein both surfaces of each lens are formed from aspheric surface, and a diffraction optics surface exerting chromatic aberration correction function is arranged on any one surface from a surface of the first lens on an object side to a surface of the third lens on the object side, and each lens is configured from plastic material.

An imaging lens which can be very compact and thin, corrects various aberrations properly and provides a small F-value and a wide view angle at low cost. In the imaging lens, designed for a solid-state image sensor, arranged in the following order from an object side to an image side are: a first positive (refractive power) lens with a convex object-side surface; a second positive lens; a third positive lens; a fourth positive lens; and a fifth negative lens with a concave image-side surface. None of these lenses is joined to each other and all the lens surfaces are aspheric. The object-side and image-side aspheric surfaces of the fifth lens have a pole-change point in a position other than a point of intersection with an optical axis. A diffractive optical surface is formed on one of three surfaces from the first lens image-side surface to the second lens image-side surface.

An imaging lens includes four lenses arranged in order from the object side to the image side: an aperture stop, positive (refractive power) first lens having a convex object-side surface near the optical axis, second lens having a positive meniscus shape near the axis, positive third lens having a convex image-side surface near the axis, and negative fourth lens having a concave image-side surface near the axis. All lens surfaces are aspheric. The image-side aspheric surface of the fourth lens has a pole-change point off the optical axis and conditional expressions (1) and (2) are satisfied:0.75&#x3c;/(2)&#x3c;0.90&#x2003;&#x2003;(1)0.90&#x3c;&#x3c;1.30&#x2003;&#x2003;(2)

A concave surface is formed on an object side of a plastic lens of a one-piece construction, and a convex surface is formed on an image-point side thereof. The concave and convex surfaces are aspherical. A diffractive optical surface that exerts a chromatic dispersion ability is formed on the convex surface, and conditional expressions (1) 0.45&#x3c;L/R&#x3c;0.95 and (2) &#x2212;0.065&#x3c;L'(1&#x2212;n)/R&#x2032;&#x3c;0.035n are met, where assuming that a position at which a chief ray and an optical axis intersect is regarded as an apparent stop, L denotes a distance to the apparent stop seen from the apex of the convex surface, L&#x2032; denotes a distance to the apparent stop seen from the apex of the concave surface, R denotes a curvature radius of the convex surface, R&#x2032; denotes a curvature radius of the concave surface, and n denotes a refractive index of a lens material.

An imaging lens with large aperture ratio, high-performance and low-cost is provided, which is applied to an imaging element of a small-size and high resolution, in which aberration is corrected satisfactorily and sufficient diffraction resolution is achieved. An imaging lens includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence from an object side, wherein both surfaces of each lens are formed from aspheric surface, a diffraction optics surface exerting chromatic dispersion function is arranged on a surface on an image side of the second lens, each lens is configured from plastic material, and an aperture ratio is equal to or smaller than F/2.4.

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Sukagawa, Japan

Hisanori Suzuki