Abstract: An imaging optical system includes an aperture stop, a first lens group disposed on an object side of the aperture stop, a second lens group disposed on an image side of the aperture stop and a plate-like ND filter disposed close to a position of the aperture stop in an optical axis direction of the first and second lens groups, and the second lens group includes positive refracting power as a whole, the ND filter is configured to be retractable from the optical axis, and to attenuate a passing light amount.

Abstract: An image forming lens including an aperture stop, a first lens group arranged on the object side relative to the aperture stop, and a second lens group having a positive power arranged on an image side relative to the aperture stop, the first lens group including a first F lens group having a negative power and a first R lens group having a positive power arranged in this sequence from the object side with the widest air space between the first F lens group and the first R lens group, the first F lens group including at least two negative lenses, the first R lens group including at least one positive lens, the second lens group including a second F lens group having a positive power and a second R lens group arranged in this sequence from the object side, the second F lens group including a first positive lens, a first negative lens, a second negative lens, and a second positive lens arranged in this sequence from the object side, and the second R lens group including at least one lens.

Abstract: An optical imaging system includes a first lens group having a positive or negative optical power, an aperture diaphragm, and a second lens group having a positive optical power arranged in order from an object side. The first lens group includes a first front lens group having at least two negative lenses and a first rear lens group having at least one positive lens with an airspace in-between the first front and rear lens groups. The second lens group includes a second front lens group having first positive and negative lenses, second negative and positive lenses arranged in order from the object side, and a second rear lens group including at least one aspherical lens. When focusing on an object in a close range from infinity, the second lens group moves to the object side while an interval between the second front and rear lens groups are shortened.

Abstract: An image reader feeds a document to read document information at a still position from below a glass platen. The image reader is configured to include a document feeder unit feeding a document in a predetermined direction, a glass platen provided below the document feeder unit, an illumination unit provided on or above the glass platen and including a surface light source which is long in a direction orthogonal to the predetermined direction and illuminates the document, and a document reader unit reading document information at a still position from below the glass platen. Such an image reader can illuminate documents efficiently with less electric power and achieve thinning of the illumination unit.

Abstract: A zoom lens includes a first lens group having a positive refractive power, and a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power arranged in order from an object side, the third lens group having a first positive lens, a second positive lens, and a negative lens, and a third positive lens in order from the object side. When zooming from short to long focal end, the zoom lens is moved so that the interval between the first and second lens groups increases, that between the second and third lens groups decreases, that between the third and fourth lens groups increases, and the first and third lens groups are positioned closer to the object at the long focal end than the short focal end.

Abstract: An imaging optical system, including a first lens group; an aperture stop; a second lens group having a positive power, the first lens group, the aperture stop and the second lens group being arranged from a side of an object sequentially, wherein the second lens group includes a second front lens group having a positive power and a second rear lens group having a positive power, the second front lens group and the second rear lens group being arranged sequentially from the object side, wherein, when focusing from an infinity-distance object to a short-distance object, the first lens group and the aperture stop are fixed, and the second front lens group and the second rear lens group are moved with a mutually different movement amount.

Abstract: An illumination unit for use in an image read apparatus is provided which illuminates a surface of an original document with illumination light, reads an image of the original document by a light receiving element, and adjusts an amount of specular light reflection from the surface of the original document on a light receiving plane of the light receiving element by adjusting at least one of an incident angle of the illumination light and a divergence thereof. It includes a plurality of light source units emitting the illumination light and arranged in a direction so that a direction in which intensity of light emitted from at least one of the light source units closest to a center of the arrangement thereof is to be highest makes a non-perpendicular angle with the direction of arrangement.

Abstract: A zoom lens includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, which are disposed in order from an object side to an image side and an aperture stop disposed between the second and third lens groups. When changing the magnification of the zoom lens from a short focal end to a long focal end, an interval between the first and second lens groups increases, an interval between the second and third lens groups decreases, and an interval between the third and fourth lens groups increases. The first and third lens groups are moved so as to be positioned at object side positions at the long focal end relative to positions at the short focal end. The third lens group has two positive lenses. Predetermined conditions of the positive lenses of the third lens group are satisfied.

Abstract: A zoom lens includes, in order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, the second lens group including, in order from the object side, a first negative lens and a cemented lens including a second negative lens having a convex shape on the object side and a positive lens, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and an aperture stop arranged between the second lens group and the third lens group, wherein when changing a magnification from a short focal end to a telephoto end, an interval between the first lens group and the second lens group is increased, an interval between the second lens group and the third lens group is decreased, an interval between the third lens group and the fourth lens group is increased, and the first lens group and the third lens group are moved to be located closer to the object side at the long focal end than the short fo

Abstract: An image forming lens includes: a first optical system positioned in an object side, a second optical system positioned in an image side, and an aperture stop interposed between the first optical system and the second optical system, wherein the first lens system includes a first F lens group which is positioned in the object side and has at least two negative lenses, and a first R lens group which is positioned in the aperture stop side and has at least one lens, wherein a distance between the first F lens group and the first R lens group is set to be largest, and wherein the second optical system includes a second F lens group in which, in the order from the aperture stop side, a first positive lens, a first negative lens, a second negative lens, and a second positive lens are arranged, and a second R lens group positioned in the aperture stop side and having at least one positive lens.

Abstract: An image reading apparatus includes: a light source which irradiates illumination light to a document; an imaging element which images reflected light of the illumination light from the document; a color separator which performs color separation of the illumination light or the reflected light into at least three wavelength ranges including a first wavelength range, a second wavelength ranges and a third wavelength range; a light-receiving element which converts the reflected light imaged by the imaging element into an electrical signal as a document image of the document, for each of the at least three wavelength ranges; and an image processor which classifies the document image on the basis of the electrical signal in the first wavelength range and in the second wavelength range.

Abstract: An imaging optical system, including a first lens group; an aperture stop; a second lens group having a positive power, the first lens group, the aperture stop and the second lens group being arranged from a side of an object sequentially, wherein the second lens group includes a second front lens group having a positive power and a second rear lens group having a positive power, the second front lens group and the second rear lens group being arranged sequentially from the object side, wherein, when focusing from an infinity-distance object to a short-distance object, the first lens group and the aperture stop are fixed, and the second front lens group and the second rear lens group are moved with a mutually different movement amount.

Abstract: An imaging optical system includes an aperture stop, a first lens group disposed on an object side of the aperture stop, a second lens group disposed on an image side of the aperture stop and a plate-like ND filter disposed close to a position of the aperture stop in an optical axis direction of the first and second lens groups, and the second lens group includes positive refracting power as a whole, the ND filter is configured to be retractable from the optical axis, and to attenuate a passing light amount.

Abstract: An optical imaging system includes a first lens group having a positive or negative optical power, an aperture diaphragm, and a second lens group having a positive optical power arranged in order from an object side. The first lens group includes a first front lens group having at least two negative lenses and a first rear lens group having at least one positive lens with an airspace in-between the first front and rear lens groups. The second lens group includes a second front lens group having first positive and negative lenses, second negative and positive lenses arranged in order from the object side, and a second rear lens group including at least one aspherical lens. When focusing on an object in a close range from infinity, the second lens group moves to the object side while an interval between the second front and rear lens groups are shortened.

Abstract: An imaging optical system, including a first lens group; an aperture stop; a second lens group having a positive power, the first lens group, the aperture stop and the second lens group being arranged from a side of an object sequentially, wherein the second lens group includes a second front lens group having a positive power and a second rear lens group having a positive power, the second front lens group and the second rear lens group being arranged sequentially from the object side, wherein, when focusing from an infinity-distance object to a short-distance object, the first lens group and the aperture stop are fixed, and the second front lens group and the second rear lens group are moved with a mutually different movement amount.

Abstract: A zoom lens includes a first optical system having a positive focal length, the first optical system, a second optical system having a negative focal length, a third optical system having a positive focal length, a fourth optical system having a negative focal length, and a fifth optical system having a positive focal length, which are arranged in order from an object side to an image side and an aperture stop provided at an object side of the third optical system. The following condition is satisfied: 0.5<(T23w/Y?)/(ft/fw)<1.0 where T23w is an interval between the second optical system and the third optical system at the short focus end, Y? is a maximum image height of the zoom lens, ft is a focal length of the zoom lens at the long focus end, and fw is a focal length of the zoom lens at the short focus end.

Abstract: An image forming lens including an aperture stop, a first lens group arranged on the object side relative to the aperture stop, and a second lens group having a positive power arranged on an image side relative to the aperture stop, the first lens group including a first F lens group having a negative power and a first R lens group having a positive power arranged in this sequence from the object side with the widest air space between the first F lens group and the first R lens group, the first F lens group including at least two negative lenses, the first R lens group including at least one positive lens, the second lens group including a second F lens group having a positive power and a second R lens group arranged in this sequence from the object side, the second F lens group including a first positive lens, a first negative lens, a second negative lens, and a second positive lens arranged in this sequence from the object side, and the second R lens group including at least one lens.

Abstract: A zoom lens unit includes, in order from an object side to an image side: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; a fourth lens group having a negative refracting power; a fifth lens group having a positive refracting power; and a sixth lens group having a negative refracting power, an aperture stop is disposed between the second lens group and the third lens group, and when changing magnification from a wide-angle end to a telephoto end, at least the second lens group, the third lens group and the fifth lens group are moved, and the first lens group includes a reflecting optical element which bends a light path in the first lens group to obtain a predetermined light path length.

Abstract: An image forming lens includes: a first optical system positioned in an object side, a second optical system positioned in an image side, and an aperture stop interposed between the first optical system and the second optical system, wherein the first lens system includes a first F lens group which is positioned in the object side and has at least two negative lenses, and a first R lens group which is positioned in the aperture stop side and has at least one lens, wherein a distance between the first F lens group and the first R lens group is set to be largest, and wherein the second optical system includes a second F lens group in which, in the order from the aperture stop side, a first positive lens, a first negative lens, a second negative lens, and a second positive lens are arranged, and a second R lens group positioned in the aperture stop side and having at least one positive lens.

Abstract: An imaging optical system, including a first lens group; an aperture stop; a second lens group having a positive power, the first lens group, the aperture stop and the second lens group being arranged from a side of an object sequentially, wherein the second lens group includes a second front lens group having a positive power and a second rear lens group having a positive power, the second front lens group and the second rear lens group being arranged sequentially from the object side, wherein, when focusing from an infinity-distance object to a short-distance object, the first lens group and the aperture stop are fixed, and the second front lens group and the second rear lens group are moved with a mutually different movement amount.