Abstract: A zoom lens includes, in order from an object side, a first lens group fixed upon zooming and wholly having a negative refractive power, a second lens group formed by an optical-path bending prism fixed upon zooming and, a third lens group allowed to move upon zooming and wholly having a positive refractive power, a fourth lens group allowed to move upon zooming and wholly having a negative refractive power, and a fifth lens group fixed upon zooming and wholly having a positive refractive power. By arranging a zooming group having the positive third and negative fourth lens groups without arranging a positive fixed lens group in back of the prism, the overall length can be easily reduced as compared to the structure arranging a fixed lens group between a prism and a zooming group.

Abstract: An imaging lens includes in order from an object side: a first lens including a positive lens having a convex surface directed to the object side; a stop; a second lens including a positive lens having a convex surface directed to an image side; a third lens including a negative meniscus lens with a concave surface directed to the object side; and a fourth lens including, near an optical axis, a positive meniscus shape with a convex surface directed to the object side. An air space between the second lens and the third lens is smaller in a periphery than near the optical axis. And f1>f2>|f3| and 1.0<f/f2<1.5 are satisfied where f1, f2 and f3 are focal lengths of the first lens, the second lens, and the third lens, respectively and f is an focal length of the whole lens system.

Abstract: An imaging lens includes in order from an object side, a stop and a first lens to a fourth lens. Both the surfaces of a third lens have surfaces including at least one inflection point, and an inclination of each surface at the terminal end part of a periphery within an effective diameter collapses toward the image side. And 0.1<D3/D4<2.0, ?d1??d2>25, 0.4<f1/f3<1.6 and 0.3<f/f3<1.5 are satisfied, where D3 is an air space on an optical axis between the first lens and the second lens, D4 is a central thickness of the second lens, ?d1 and ?d2 are Abbe numbers of the first lens and the second lens, f1 and f3 are focal lengths of the first lens and the third lens and f is a focal length of an entire system.

Abstract: An imaging lens is provided and includes: a positive first lens with a convex surface directed to the object side; a second lens having a negative meniscus shape with a concave surface directed to the image side; a third lens having a positive meniscus shape with a convex surface directed to the image side; a negative fourth lens with both surfaces being an aspheric surface and the image-side surface being concave in the proximity of the optical axis; and a positive or negative fifth lens with both surfaces being an aspheric surface, in order from the object side. The following conditional expressions are satisfied as for Abbe numbers vd1 and vd2of the first lens and the second lens and Abbe number vd4 of the fourth lens.

Abstract: An imaging device is provided and includes: an imaging element that outputs an imaging signal based on an optical image; and a diffractive optical element disposed on an image formation surface side of the imaging element.

Abstract: An imaging lens is provided and has, in order from the object side, a first lens of a positive lens having a convex surface on the object side thereof; a second lens in a meniscus shape having a concave surface on an image side thereof; a third lens in a meniscus shape having a convex surface on the image side thereof; and a fourth lens of a positive or negative lens, both surfaces of the fourth lens being aspheric and the fourth lens having a concave surface on the image side and in a vicinity of an optical axis of the fourth lens. The Abbe numbers of the first and second lenses as well as the focal distances of the first to fourth lenses satisfies specific conditions.

Abstract: An imaging lens is provided and includes: a first lens of a positive lens; a second lens of a negative lens whose concave surface faces to an image side of the second lens; a third lens of a positive lens, whose both surfaces are aspheric, having a concave surface facing to an object side of the third lens; and a fourth lens of a meniscus lens, whose both surfaces are aspheric, having a convex surface facing to the object side near the optical axis, the lenses being arranged in this order from an object side, the first imaging lens satisfying the conditional expressions specified in the specification.

Abstract: A zoom lens includes, in order from an object side, a first lens group fixed upon zooming and wholly having a negative refractive power, a second lens group formed by an optical-path bending prism fixed upon zooming and, a third lens group allowed to move upon zooming and wholly having a positive refractive power, a fourth lens group allowed to move upon zooming and wholly having a negative refractive power, and a fifth lens group fixed upon zooming and wholly having a positive refractive power. By arranging a zooming group having the positive third and negative fourth lens groups without arranging a positive fixed lens group in back of the prism, the overall length can be easily reduced as compared to the structure arranging a fixed lens group between a prism and a zooming group.

Abstract: An imaging lens is provided and includes, in order from an object side of the imaging lens: a first lens of a positive lens; a second lens of a negative lens; a third lens of a bi-aspheric lens that has an image-side surface having an extreme point at a position other than an optical axis of the imaging lens; and a fourth lens of a bi-aspheric lens that has an object-side surface having an extreme point at a position other than the optical axis. The imaging lens satisfies Conditional Expressions specified in the specification.

Abstract: An imaging optical system is provided and has a focusing section including a cemented lens (first and second lenses), which includes first and second fluid materials having different refractive indices from each other; and whose cemented surface shape can be electrically controlled. A refractive index Nd1 of the first fluid material, a refractive index Nd2 of the second fluid material, a minimum value RA of a radius of curvature of the cemented surface of the cemented lens, a focal length fa of the whole cemented lens, and a focal length f of the whole lens system satisfy the conditions specified in the specification.

Abstract: An imaging lens comprises, in order from an object side: an aperture stop; a first lens having a positive refractive power in a meniscus form having a convex surface facing toward the object; a second lens having a positive or negative refractive power in a meniscus form having a concave surface facing toward the object; and a third lens having a positive or negative refractive power in an aspheric form at both surfaces, wherein conditional expressions given below are satisfied: vd1>50 ??(1) vd3>50 ??(2) 0.7<f1/f<1.0 ??(3) ?0.9<f2/{f3·(45?vd2)}<0.4 ??(4) where vd1: Abbe number of the first lens, vd2: Abbe number of the second lens, vd3: Abbe number of the third lens, f: Focal length of an overall system, f1: focal length of the first lens, f2: focal length of the second lens, and f3: focal length of the third lens.

Abstract: An imaging lens is provided and includes: a positive first lens with a convex surface directed to the object side; a second lens having a negative meniscus shape with a concave surface directed to the image side; a third lens having a positive meniscus shape with a convex surface directed to the image side; a negative fourth lens with both surfaces being an aspheric surface and the image-side surface being concave in the proximity of the optical axis; and a positive or negative fifth lens with both surfaces being an aspheric surface, in order from the object side. The following conditional expressions are satisfied as for Abbe numbers vd1 and vd2 of the first lens and the second lens and Abbe number vd4 of the fourth lens.

Abstract: An imaging lens is provided and has, in order from the object side, a first lens of a positive lens having a convex surface on the object side thereof; a second lens in a meniscus shape having a concave surface on an image side thereof; a third lens in a meniscus shape having a convex surface on the image side thereof; and a fourth lens of a positive or negative lens, both surfaces of the fourth lens being aspheric and the fourth lens having a concave surface on the image side and in a vicinity of an optical axis of the fourth lens. The Abbe numbers of the first and second lenses as well as the focal distances of the first to fourth lenses satisfies specific conditions.

Abstract: An imaging lens is provided and includes: a first lens of a positive lens; a second lens of a negative lens whose concave surface faces to an image side of the second lens; a third lens of a positive lens, whose both surfaces are aspheric, having a concave surface facing to an object side of the third lens; and a fourth lens of a meniscus lens, whose both surfaces are aspheric, having a convex surface facing to the object side near the optical axis, the lenses being arranged in this order from an object side, the first imaging lens satisfying the conditional expressions specified in the specification.

Abstract: An imaging lens is provided and includes, in order from an object side of the imaging lens: a first lens of a positive lens; a second lens of a negative lens; a third lens of a bi-aspheric lens that has an image-side surface having an extreme point at a position other than an optical axis of the imaging lens; and a fourth lens of a bi-aspheric lens that has an object-side surface having an extreme point at a position other than the optical axis. The imaging lens satisfies Conditional Expressions specified in the specification.

Abstract: An imaging optical system is provided and has a focusing section including a cemented lens (first and second lenses), which includes first and second fluid materials having different refractive indices from each other; and whose cemented surface shape can be electrically controlled. A refractive index Nd1 of the first fluid material, a refractive index Nd2 of the second fluid material, a minimum value RA of a radius of curvature of the cemented surface of the cemented lens, a focal length fa of the whole cemented lens, and a focal length f of the whole lens system satisfy the conditions specified in the specification.

Abstract: A zoom lens includes three lens groups. The first lens group from the object side has negative refractive power and is formed of two lens components. The second lens group from the object side has positive refractive power and is formed of two lens components. The third lens group is formed of one lens component and has positive refractive power. All but one of the lens components may be lens elements. Only the first and second lens groups move along the optical axis for zooming. At least one lens surface of the second lens group has portions with curvatures of different signs. The zoom lens may include as many as five other aspheric surfaces. The aspheric lenses are made of plastic. The zoom lens may be formed of only the three lens groups and satisfies specified conditions to assure that the zoom lens is compact and favorably corrects various aberrations.

Abstract: An imaging lens includes, in order from the object side: a first lens component of negative refractive power with two aspheric surfaces including a concave surface near the optical axis on the image-side; a second lens component of positive refractive power with a convex surface on the object side; a third lens component having positive refractive power and including lens elements having positive and negative refractive powers; and a fourth lens component having an aspheric surface on the image side that is convex near the optical axis and is concave at the periphery. The imaging lens satisfies a specified condition to assure a sufficient back focus for insertion of additional optical elements, a sufficiently small imaging lens diameter, and favorable correction of aberrations. The imaging lens has a wide picture angle, consists of only 5 lens elements in the disclosed embodiments, and is particularly suited for a text imaging camera.