A scanning optical device includes a deflector, a reflecting mirror, a housing to accommodate the deflector and the mirror; and an elastic member to urge the mirror toward the housing. The mirror includes a first surface urged by the elastic member, a second surface opposite to the first surface, a third surface and a fourth surface perpendicular to the first and second surfaces. The housing includes a bearing surface to support the second surface and a regulating portion to regulate movement of the mirror to a mirror widthwise direction, perpendicular to a mirror longitudinal direction and parallel with the second surface, and toward an opening of the housing. The regulating portion is provided opposite to only a part of the third surface so that a ridge line of the mirror between the second surface and the third surface does not contact the regulating member even an attitude of the mirror changes in a direction away from the bearing surface.

An optical scanning device includes a light source, a deflector, a random number generator, a selection part, a random number assignment part and an exposure control part. The light source includes a plurality of light emitting parts arranged in a predetermined direction at fixed intervals in a sub-scanning direction. The random number assignment part is configured to assign a random number sequence to each light emitting part constituting a set of target light emitting parts as an index for specifying a timing at which a light emitting time of the set of target light emitting parts is set to a correction value different from a reference value and to update the assignment of the random number sequence at a random number update period. The random number update period coincides with a scanning period of each light emitting part constituting the set of target light emitting parts.

An optical scanning device includes a light source, a deflector, a random number generator, a selection part, a random number assignment part and an exposure control part. The light source includes a plurality of light emitting parts arranged in a predetermined direction at fixed intervals in a sub-scanning direction. The random number assignment part is configured to assign a random number sequence to each light emitting part constituting a set of target light emitting parts as an index for specifying a timing at which a light emitting time of the set of target light emitting parts is set to a correction value different from a reference value and to update the assignment of the random number sequence at a random number update period. The random number update period coincides with a scanning period of each light emitting part constituting the set of target light emitting parts.

According to aspects of the embodiments, there is provided process and architecture for enabling multiple digital micromirror devices (DMDs) that include optical modulation elements configured to modulate light outputting from a light source, and a projection unit configured to project light modulated by the optical modulation elements on a printing plate. Image defects due to misalignment in the cross-process direction of the output from the DMDs are discovered by using a single test pattern image and combined with knowledge of how individual pixels are rendered to register printing elements which can render a variable number of pixels. Misalignment errors can be corrected by selecting a different set of mirrors for a given DMD.

An image forming apparatus includes a first temperature sensor inside the image forming apparatus and configured to detect a temperature. A controller is configured to execute a first position shift correction for each of a plurality of toner images used in printing an image when the first temperature sensor detects a change in temperature from a previously detected temperature exceeds a first threshold value set for a first temperature range. After the first position shift correction, the controller executes a second position shift correction if the detected change exceeds a second threshold value set for a second temperature range higher than the first temperature range and the temperature is outside a prescribed temperature range, and skips the second position shift correction otherwise.