Optical scanner and electrophotographic image forming apparatus are provided. The optical scanner includes a light source, configured to emit a light beam; an optical deflector, configured to deflect the light beam emitted from the light source; a first optical unit, arranged there-between and including a refraction unit and a diffraction unit; and a second optical unit, arranged in a light exit direction of the optical deflector and configured to make the light beam deflected by the optical deflector form an image on a scanning target surface. A range of a ratio of a refractive power Φ.sub.r to a diffractive power Φ.sub.d of the first optical unit in a main scanning direction is 0.3<Φ.sub.r/Φ.sub.d<0.5; and a range of a ratio of a refractive power Φ.sub.s to a diffractive power Φ.sub.n of the first optical unit in a sub scanning direction is 0.7<Φ.sub.s/Φ.sub.n<1.0.

An image forming apparatus, including a photosensitive member, a scanning optical unit configured to scan the photosensitive member by laser light according to image information, a detection unit arranged in a position facing the photosensitive member and configured to output positional information on the laser light. The detection unit includes a detection portion into which the laser light reflected by the photosensitive member is incident, and a control unit configured to calculate a positional deviation amount of an irradiation position on the photosensitive member which is irradiated by the laser light based on the positional information output by the detection unit, and control the scanning optical unit to correct the positional deviation of the irradiation position of the laser light.

An image forming apparatus includes an image forming device and a control device. The image forming device forms an image on a recording medium. The control device controls an image forming process. The control device includes circuitry. The circuitry changes a plurality of partial images in a target image into a certain state. The target image is to be formed on the recording medium. The plurality of partial images are to be formed peripheral to a plurality of pattern images. Each of the plurality of pattern images is to be formed at a certain position on the recording medium. The circuitry further controls the image forming device to form the target image including the changed plurality of partial images and the plurality of pattern images on the recording medium, and corrects a position of the target image based on a detection result of the formed plurality of pattern images.

An optical device includes a lens mirror array, in which transparent optical elements are connected to each other along a first direction, and a case, in which the lens mirror array is contained and fixed. The case includes at least three holes through which a manufacturing jig can pass. The jig can be used to press the lens mirror array in a direction intersecting the first direction at three or more positions on the lens mirror array to deform the lens mirror array to correct for possible distortions in the optical device prior to the fixing of the lens mirror array to the case.

An optical scanning device of an electrophotographic printer is provided. The optical scanning device includes an optical source portion to emit an optical beam inclined in a sub-scanning direction with respect to a reference plane, an optical deflector to deflect and scan the optical beam in a main scanning direction, and an imaging lens to image the deflected optical beam onto a light-exposed object and having an optical axis which is parallel to the reference plane. In order to correct a scanning line curvature, a location of a vertex of a curved surface of the imaging lens in the sub-scanning direction is varied based on a location in the main scanning direction.

Provided is a light source device including a plurality of light emitting points arranged in matrix within a first cross section parallel to a first direction and a second direction. When light emitting points are projected within a second cross section parallel to first direction and a third direction perpendicular to first cross section, light emitting points have equal intervals between projections adjacent to each other. When light emitting points are projected within a third cross section parallel to second and third directions, light emitting points have equal intervals between projections adjacent to each other. An interval between light emitting points adjacent to each other in a row of matrix, an interval between light emitting points adjacent to each other in a column of matrix, an angle between row and column, an angle between column and first direction, and an angle between row and second direction are appropriately set.

An image forming apparatus includes a plurality of photosensitive members; a scanner unit including light sources, a rotatable polygonal mirror, and reflecting members; and a fixing portion. Parts of the laser beams emitted from the light sources are reflected by the rotatable polygonal mirror toward the fixing device side, and rest parts of the laser beams are reflected by the rotatable polygonal mirror toward a side opposite from the fixing device side. Of the parts of the laser beams reflected by the rotatable polygonal mirror toward the fixing device side, the laser beam reflected toward the reflecting member provided at a position remotest from the rotatable polygonal mirror travels downward relative to a horizontal direction. A rotational axis of the rotatable polygonal mirror is inclined relative to a vertical direction.

To provide a shading correction signal generation device including a correction amount setting signal generator that generates a correction amount setting signal, a modulator that modulates the correction amount setting signal by a predetermined modulation scheme and outputs the modulation signal, and a filter circuit that filters the modulation signal to generate a shading correction signal. During a transition period, the correction amount setting signal generator generates the correction amount setting signal in which a difference between a level at an end of a predetermined period and an average level during the transition period is larger than a difference between the level at the end of the predetermined period and a level at a start of a shading correction period.

An optical scanning device for an electrophotographic printer includes a light source that radiates a light beam and a light deflector that deflects the light beam radiated by the light source in a main scanning direction. The optical scanning device also includes a synchronization detection sensor having a sensing region that receives a portion of the light beam deflected by the light deflector. The sensing region has a greater length in the main scanning direction than in a sub-scanning direction.

An optical scanning device of an electrophotographic printer is provided. The optical scanning device includes an optical source portion to emit an optical beam inclined in a sub-scanning direction with respect to a reference plane, an optical deflector to deflect and scan the optical beam in a main scanning direction, and an imaging lens to image the deflected optical beam onto a light-exposed object and having an optical axis which is parallel to the reference plane. In order to correct a scanning line curvature, a location of a vertex of a curved surface of the imaging lens in the sub-scanning direction is varied based on a location in the main scanning direction.