An image forming apparatus comprises a first temperature detector to detect a temperature of a first portion of an optical scanning device in a printer. The first portion is proximate to a heat generating element in the optical scanning device. A second temperature detector is provided to detect a temperature of a second portion of the optical scanning device, which is farther from the heat generating element than the first portion. A controller is configured to perform alignment control for correcting a color positional shift of the printer when either a detected temperature change of the first portion is greater than or equal to a first threshold value or a detected temperature change of the second portion is greater than or equal to a second threshold value.

An imaging optical mechanism includes a first concave mirror and a second concave mirror at a position shifted from the first concave mirror in a sub-scanning direction. A plurality of aperture members in which slits are formed is disposed between the first concave mirror and the second concave mirror. The first concave mirror reflects light incident from an original document so as not to be imaged at a position between the first concave mirror and the second concave mirror in the sub-scanning direction, and reflects light incident from the original document so as to be imaged at the position between the first concave mirror and the second concave mirror in a main scanning direction. The second concave mirror reflects light which is reflected by the first concave mirror and incident thereto, so as to be imaged at a position of a sensor.

An image forming apparatus comprises a first temperature detector to detect a temperature of a first portion of an optical scanning device in a printer. The first portion is proximate to a heat generating element in the optical scanning device. A second temperature detector is provided to detect a temperature of a second portion of the optical scanning device, which is farther from the heat generating element than the first portion. A controller is configured to perform alignment control for correcting a color positional shift of the printer when either a detected temperature change of the first portion is greater than or equal to a first threshold value or a detected temperature change of the second portion is greater than or equal to a second threshold value.

Provided is a reading module including a light source, an optical system, and a sensor. The optical system images reflected light of light emitted from the light source to the document, as image light. The sensor converts the imaged image light into an electric signal. The optical system includes a mirror array in which a plurality of reflection mirrors are connected, and a plurality of aperture stops. Neighboring reflection mirrors reflect light at different angles viewed from the main scanning direction.

An imaging optical mechanism includes a first concave mirror and a second concave mirror at a position shifted from the first concave mirror in a sub-scanning direction. A plurality of aperture members in which slits are formed is disposed between the first concave mirror and the second concave mirror. The first concave mirror reflects light incident from an original document so as not to be imaged at a position between the first concave mirror and the second concave mirror in the sub-scanning direction, and reflects light incident from the original document so as to be imaged at the position between the first concave mirror and the second concave mirror in a main scanning direction. The second concave mirror reflects light which is reflected by the first concave mirror and incident thereto, so as to be imaged at a position of a sensor.

Provided is a reading module including a light source, an optical system, and a sensor. The optical system images reflected light of light emitted from the light source to the document, as image light. The sensor converts the imaged image light into an electric signal. The optical system includes a mirror array in which a plurality of reflection mirrors are connected, and a plurality of aperture stops. Neighboring reflection mirrors reflect light at different angles viewed from the main scanning direction.

A scanner reads a document using a sensor group and includes an optical member. When a scanning resolution in a main scanning direction is D, and a resolution of the sensor group is S, the optical member causes the sensor group to image light from the document magnified by a magnification ratio n, where n is greater than or equal to D/S and is greater than 1. The sensor group includes a plurality of sensor portions that are arrayed in L rows in a sub-scanning direction, and L is greater than or equal to n and is an integer of 3 or more. Each of the sensor portions reads a magnified image that is magnified by the magnification ratio n at each corresponding position in the main scanning direction of the document and that is guided by the optical member.