An image reading apparatus includes a circuit board on which a plurality of light sources are disposed in a longitudinal direction, a light guide portion including a first holding portion configured to hold the circuit board, and a second holding portion configured to hold the circuit board, a support member configured to support the light guide portion, and an image reading unit configured to read image information by performing photoelectric conversion on reflected light reflected by a sheet which has received light emitted from the light guide portion. The support member includes a projecting portion disposed between the first holding portion and the second holding portion in the longitudinal direction, the projecting portion facing and projecting toward the circuit board held by the first holding portion and the second holding portion.

According to an embodiment, a reading device that reads an object to be read in an image forming apparatus includes a lens array and a light guide. The lens array is provided in a posture in which an optical axis follows a height direction intersecting a reading surface. The light guide is adjacent to the lens array in a sub-scanning direction intersecting both the height direction and a main scanning direction, and locates maximum illuminance of illumination light illuminating the object to be read on a side opposite to the lens array with respect to a deepest position of a depth of field of the lens array in the height direction.

A light guide configured to cause light entering from a point light source to exit as linear light. The light guide has a rod portion extending in a first direction and having a reflecting surface. A plurality of reflecting elements are provided on the reflecting surface to reflect the light entering from the point light source. A part of the reflecting elements located closer to the point light source than a center of the rod with respect to the first direction is arranged so as to sheer away from a strongly illuminated area of the reflecting surface, which is an area illuminated strongly with light entering the rod portion, in a second direction parallel to the reflecting surface and perpendicular to the first direction.

Provided is a manufacturing method of a sensor unit, the sensor unit including: a rod-shaped light condenser that condenses light from an original; a frame that houses the light condenser; and a plurality of urging members that urge the light condenser toward the frame and mount the light condenser on the frame, the manufacturing method including: a light condenser housing step of housing the light condenser in the frame; and an urging member mounting step of pressing, by an assembly machine, the plurality of urging members against the frame.

Provided is an illumination apparatus that applies light to an original, the illumination apparatus including: a light source; and a rod-shaped light guide including: an incident surface that receives the light from the light source; a reflection surface provided with a diffusion portion that diffuses the light incident on the incident surface; and an emission surface that emits, to the original, the light diffused by the diffusion portion. An area of the light guide is reduced by an inclination of the light guide from the incident surface side to a middle part in a longitudinal direction of the light guide, and the light guide is provided with the diffusion portion from the incident surface side to the middle part on the reflection surface.

An image sensor module includes an elongated light emitting unit, a photodetector, a lens unit, a substrate with the photodetector mounted on. The substrate is spaced apart from the lens unit in a thickness direction of the substrate. The image sensor module further includes a resin case provided with a light emitting unit chamber, a lens unit chamber and a substrate chamber. The lens unit chamber has a first bottom face extending in the first direction, and the substrate chamber has a second bottom face extending in the first direction and facing opposite to the first bottom face in the thickness direction of the substrate. The first or second bottom face is formed with at least one protrusion extending in the thickness direction of the substrate.

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: three or more light sources configured to each emit light; a light receiving unit including a common light receiving surface configured to detect each light emitted; and an image generation unit configured to cause the three or more light sources to be switched over in a predetermined order and emit the corresponding light, and generate an image read from a document, wherein at least one of the three or more light sources includes a white light source and an optical filter, and the optical filter is configured such that a half-value width of a wavelength with respect to a maximum intensity of a spectral characteristic of the emitted light after transmission is wider than a half-value width of a wavelength with respect to a maximum intensity of the spectral characteristic of the light emitted from at least one of the other light sources.

An image reading apparatus includes a reading module provided with reading elements arranged in a direction of arrangement intersecting a direction of transportation of an original copy, and configured to read an image on the transported original copy. The apparatus also includes a background plate provided with a white background portion for shading correction, and a black background portion for cutting out the original copy and having lower brightness than brightness of the white background portion. An area of the black background portion is larger than an area of the white background portion, and the white background portion and the black background portion are arranged in the direction of arrangement.

An image reading apparatus includes a reading module provided with reading elements arranged in a direction of arrangement intersecting a direction of transportation of an original copy, and configured to read an image on the transported original copy. The apparatus also includes a background plate provided with a white background portion for shading correction, and a black background portion for cutting out the original copy and having lower brightness than brightness of the white background portion. An area of the black background portion is larger than an area of the white background portion, and the white background portion and the black background portion are arranged in the direction of arrangement.