An exposure unit comprises a polygon mirror configured to include a plurality of reflection surfaces; first to fourth light sources arranged at different angle positions along a rotation direction of the polygon mirror; two photo detectors configured to selectively detect first laser light and fourth laser light respectively at a scanning start end side of a main scanning direction among first to fourth laser light which are emitted from the respective light sources and reflected by the polygon mirror to be scanned in the main scanning direction; and a control section configured to control light emitting timing of the first to the fourth light sources on the basis of detection results of these photo detectors.

An exposure unit comprises a polygon mirror configured to include a plurality of reflection surfaces; first to fourth light sources arranged at different angle positions along a rotation direction of the polygon mirror; two photo detectors configured to selectively detect first laser light and fourth laser light respectively at a scanning start end side of a main scanning direction among first to fourth laser light which are emitted from the respective light sources and reflected by the polygon mirror to be scanned in the main scanning direction; and a control section configured to control light emitting timing of the first to the fourth light sources on the basis of detection results of these photo detectors.

A reading module includes a light source, an optical system for forming an image of reflection light from a document illuminated by the light source, and a sensor including a plurality of sensor chips to convert the image light formed by the optical system into an electric signal. The optical system includes a mirror array including a plurality of reflecting mirrors connected in the main scanning direction, first aperture stops each of which adjusts light amount of the image light reflected from each of the reflecting mirrors, second aperture stops each extending from the opening edge of the first aperture stop toward the mirror array, first light shielding walls each of which extends from a boundary between the sensor chips toward the first aperture stops, and second light shielding walls extending from both sides in the main scanning direction of the first aperture stop toward the sensor chips.

A light-guide member includes a light-incident surface formed at an end portion of the light-guide member in a first direction, a light-emitting surface that is elongated in the first direction and that includes first and second light-emitting regions, which cause light to be emitted in different directions in a first cross section that is perpendicular to the first direction, a common deflecting portion that deflects light from the light-incident surface and causes the light to be emitted from the first and second light-emitting regions to the outside, and first and second protruding portions each of which is located on one of two sides of the deflecting portion in the first cross section, the first and second protruding portions protruding in a direction away from the light-emitting surface with respect to the deflecting portion.

A prism block is provided at least one notch to propagate in the light flux in air, on an optical path from entrance of a light flux via a first portion of the prism block to exit of the light flux via a second portion of the prism block. The notch is configured such that the light flux exiting from inside of the prism block via a first interface of the notch between the prism block and the air re-enters the prism block via a second interface between the air and the prism block, the second interface facing the first interface.

An image reading device includes a contact glass, a first lamp, an image sensor, a first lamp, a light absorbing member, and a second lamp. When reading a document, in a first period, the first lamp is turned on while the second lamp is turned off. In a second period, the second lamp is turned on while the first lamp is turned off. On the basis of first image data obtained by reading in the first period and second image data obtained by reading in the second period, the control unit determines whether each pixel in the first image data is a pixel having read document data or not.

An image reading device has a reading module including a light source, an optical system having a mirror array where reflection mirrors are coupled together in the main scanning direction and an aperture stop portion, a sensor where imaging regions for converting the image light imaged by the optical system into an electrical signal are arranged, and a housing, and has a reference drawing pattern determining connection positions between the imaging regions. The reference drawing pattern is composed of a plurality of pixel cut lines arranged to correspond to boundary lines between the reflection mirrors. The optical system is fixed on the housing at one point in the main scanning direction, and the pixel cut lines are arranged such that their distances from the boundary lines in the main scanning direction increase the farther away from the fixed position of the optical system in the main scanning direction.

A reading module includes: a light source for applying light to a document; an optical system for forming an image as image light from reflected light of the light applied from the light source to the document; and a sensor in which a plurality of sensor chips for converting the image light formed by the optical system to electric signals are disposed in adjacency to one another in a main scanning direction. The optical system includes: a mirror array in which a plurality of reflecting mirrors whose reflecting surfaces are aspheric surfaces are coupled in array in the main scanning direction; and apertures provided between the reflecting mirrors and the sensor chips, respectively, to regulate light quantity of the image light reflected by the individual reflecting mirrors. The specular-surface number of the reflecting mirrors is set to an integral multiple of the number of the sensor chips.

A reading module includes a light source, an optical system for forming an image of reflection light from a document illuminated by the light source, and a sensor including a plurality of sensor chips to convert the image light formed by the optical system into an electric signal. The optical system includes a mirror array including a plurality of reflecting mirrors connected in the main scanning direction, first aperture stops each of which adjusts light amount of the image light reflected from each of the reflecting mirrors, second aperture stops each extending from the opening edge of the first aperture stop toward the mirror array, first light shielding walls each of which extends from a boundary between the sensor chips toward the first aperture stops, and second light shielding walls extending from both sides in the main scanning direction of the first aperture stop toward the sensor chips.

Provided is an optical apparatus including a line sensor that includes plural detection portions arranged in a lateral direction, the detection portions including plural light-receiving elements arranged in a line shape in a longitudinal direction, a direction corresponding to the and lateral direction being set as a first direction and a direction corresponding to the longitudinal direction being set as a second direction in a surface perpendicular to an optical axis of light which forms an image on the line sensor, and a reduction optical system that reflects light from an original document and guides the reflected light to the detection portion, and includes plural curved-surface mirrors that have curvatures in the first direction and the second direction as a whole.