Kantatsu Co., Ltd.

Shingo Watanabe

Hisanori Suzuki

Kazuo Matsuoka

Ichiro Kurihara

Kenichi Kamada

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.

Imaging lens

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

Shingo Watanabe