An image reading apparatus includes an illumination unit that illuminates light on an image surface of a sheet, and a photoelectric conversion element that converts reflected light from the sheet illuminated by the illumination unit into an electric signal. The illumination unit includes a circuit board including a light emitting element, and a light guide that guides light, emitted from the light emitting element, to a sheet read surface. In the image reading apparatus, the light guide includes a positioning surface that abuts against a first surface of the circuit board and that performs positioning of the light guide and the circuit board, and a pressing portion that abuts against a second surface of the circuit board on an opposite side of the first surface and that presses the circuit board against the positioning surface.

A light irradiation device includes a light source, a light guide member, and a holding member. The light guide member includes an incident surface, an exit surface, and a held surface. The incident surface has an elongated shape in a main scanning direction and faces a light emitting surface of the light source. The light guide member includes a securing structure in each of both end portions in the main scanning direction, which are out of a light guide area of the light guide member. The securing structure in one end portion is an engagement lug structure protruding to penetrate into a through-hole of the holding member, including a lug on a leading end, and engaging the holding member. The securing structure on another end portion is a fastening structure having a fastening hole penetrated with a fastening member and being secured to the holding member with the fastening member.

Provided is an optical head that includes a base substrate and a line head. The line head includes a plurality of sub-line heads electrically independent of one another and arranged on the base substrate in parallel with a first direction. Each of the plurality of sub-line heads includes a circuit substrate unit that constitutes a portion of the base substrate, and an optical-element array that includes a plurality of optical elements each arranged on the circuit substrate unit at least in parallel with a second direction that is a direction of a length of each of the plurality of sub-line heads.

An image reading apparatus includes an illumination unit that illuminates light on an image surface of a sheet, and a photoelectric conversion element that converts reflected light from the sheet illuminated by the illumination unit into an electric signal. The illumination unit includes a circuit board including a light emitting element, and a light guide that guides light, emitted from the light emitting element, to a sheet read surface. In the image reading apparatus, the light guide includes a positioning surface that abuts against a first surface of the circuit board and that performs positioning of the light guide and the circuit board, and a pressing portion that abuts against a second surface of the circuit board on an opposite side of the first surface and that presses the circuit board against the positioning surface.

An illuminating device capable of stably illuminating an irradiated object such as a document while suppressing light loss with a simply structure is provided. An LED array and a reflective plate are disposed sandwiching a slit (St) through which light reflected by a document MS passes and a light-guiding member is disposed on the side of the LED array. The light-guiding member includes a direct emission unit disposed between an illumination range y centered on a document reading position and the LED array and an indirect emission unit disposed between the reflective plate and the LED array, a light incidence face of the direct emission unit and a light incidence face of the indirect emission unit are disposed at mutually different position around the LED array, and the LED array is disposed on a side of an interior angle formed by the light incidence faces.

[Solving Means] An optical head includes a base substrate and a line head. The line head includes a plurality of sub-line heads electrically independent of one another and arranged on the base substrate in parallel with a first direction. Each of the plurality of sub-line heads includes a circuit substrate unit that constitutes a portion of the base substrate, and an optical-element array that includes a plurality of optical elements each arranged on the circuit substrate unit at least in parallel with a second direction that is a direction of a length of each of the plurality of sub-line heads.

An image reading apparatus includes an illumination unit that illuminates light on an image surface of a sheet, and a photoelectric conversion element that converts reflected light from the sheet illuminated by the illumination unit into an electric signal. The illumination unit includes a circuit board including a light emitting element, and a light guide that guides light, emitted from the light emitting element, to a sheet read surface. In the image reading apparatus, the light guide includes a positioning surface that abuts against a first surface of the circuit board and that performs positioning of the light guide and the circuit board, and a pressing portion that abuts against a second surface of the circuit board on an opposite side of the first surface and that presses the circuit board against the positioning surface.

An image reading apparatus includes an illumination unit that illuminates light on an image surface of a sheet, and a photoelectric conversion element that converts reflected light from the sheet illuminated by the illumination unit into an electric signal. The illumination unit includes a circuit board including a light emitting element, and a light guide that guides light, emitted from the light emitting element, to a sheet read surface. In the image reading apparatus, the light guide includes a positioning surface that abuts against a first surface of the circuit board and that performs positioning of the light guide and the circuit board, and a pressing portion that abuts against a second surface of the circuit board on an opposite side of the first surface and that presses the circuit board against the positioning surface.

An illuminating device according to an embodiment included in an image reading apparatus and an image forming apparatus includes light source portions, light-guiding members for illuminating an illumination target from an elongated light emitting face that extends in a longitudinal direction, by guiding light from the light source portions, and holding members for holding the light-guiding members. The holding members include holding portions for removably holding the light-guiding members, and tilted portions that reflect light emitted from the light emitting face, the tilted portions extending from a front end on the light emitting face side of the holding portions, obliquely widening with increasing distance from the light-guiding members.

An illuminating device according to an embodiment included in an image reading apparatus and an image forming apparatus includes light source portions, light-guiding members for illuminating an illumination target from an elongated light emitting face that extends in a longitudinal direction, by guiding light from the light source portions, and holding members for holding the light-guiding members. The holding members include holding portions for removably holding the light-guiding members, and tilted portions that reflect light emitted from the light emitting face, the tilted portions extending from a front end on the light emitting face side of the holding portions, obliquely widening with increasing distance from the light-guiding members.