Kantatsu Co., Ltd.

Kazuo Matsuoka

Hisanori Suzuki

Shingo Watanabe

Ichiro Kurihara

Kenichi Kamada

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.

Imaging lens

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.

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.

Growing community of inventors

Saitama, Japan

Kazuo Matsuoka