Abstract: A light source part has a light source unit in which the plurality of light sources respectively emitting the light beams at angles different in a sub-scanning direction with respect to an optical standard plane, parallel to a main scanning direction and passing through a standard axis of a surface shape of a lens of the imaging part, which lens is closest to the deflecting part, and applied to the deflecting part at angles different in the sub-scanning direction, are integrally provided; and the plurality of light sources are inclined so that the plurality of light sources thus respectively emit the light beams at the angles different in the sub-scanning direction with respect to the optical standard plane.

Abstract: An optical scanning apparatus includes light source units; a deflecting unit, incident optical systems provided so as to correspond to the light source units, and at least one synchronous detection optical system that controls a timing at which the light beams form images on the surfaces to be scanned. The synchronous detection optical system includes a synchronous detection element, at least one optical path changing unit, and at least one synchronous detection optical element. The synchronous detection element is attached to a circuit substrate of the light source unit arranged to oppose the light source unit that emits a light beam used for synchronous detection, with the deflecting unit therebetween. The synchronous detection optical element and the synchronous detection element are arranged to oppose each other with respect to a line perpendicular to lines connecting a deflection axis of the deflecting unit and optical axes of the imaging optical systems.

Abstract: At least one exemplary embodiment is directed to an image forming apparatus, which includes: a first to fourth image bearing members on which toner images of four colors of yellow, magenta, cyan, and black are formed respectively; a first rotatable polygon mirror for deflecting and scanning laser beams on the first to fourth image bearing members so as to form electrostatic latent images on the first to fourth image bearing members; a detachable fifth image bearing member on which a toner image of a color different from the four colors is formed; and a detachable optical unit including a second rotatable polygon mirror that deflects and scans a laser beam on the fifth image bearing member so as to form an electrostatic latent image on the fifth image bearing member.

Abstract: An optical scanning apparatus and a color image forming apparatus using the same, in which streak-shaped density unevenness is reduced to prevent image deterioration: each of scanning surfaces is simultaneously scanned with light beams emitted from light source units and scanning lines are simultaneously drawn on the scanning surfaces; the light beams emitted from at least four light emitting portions of the corresponding light source unit are simultaneously deflected for scanning by a deflecting unit; and image data corresponding to a first scanning line, i.e. a scanning line located on an uppermost stream side in a direction in which the scanning surfaces move among scanning lines, on at least one of the scanning surfaces in a k-th scanning by the deflecting unit is displaced by at least one line space from image data corresponding to a first scanning line on another scanning surface in the k-th scanning.

Abstract: A scanning optical system leads the light fluxes deflected by the polygon mirror to a photosensitive drum. An absolute value of a lateral magnification in a main scanning direction is larger than an absolute value of a lateral magnification in a sub-scanning direction. Moreover, a beam diameter in the sub-scanning direction on a surface of the photosensitive drum is equal to or smaller than a beam diameter in the main scanning direction and larger than a scan line interval.

Abstract: An optical scanning device includes a rotary polygonal mirror for scanningly deflecting light beams emitted from a light source device having light emitting members disposed spaced apart from each other in a main-scan direction. The optical scanning device further includes an input optical system by which, in a sub-scan section, light beams are incident on a deflecting surface of the rotary polygonal mirror in an oblique direction with respect to a normal to the deflecting surface, and an imaging optical system by which the light beams scanningly deflected by the rotary polygonal mirror are imaged on a surface to be scanned.

Abstract: An object of the present invention is to provide a scanning optical system capable of reducing the number of its components and its size with a simple construction, and an image forming apparatus using the scanning optical system. In a specific scanning optical system, a plurality of light beams emitted from a plurality of light source units are deflected and scanned by a plurality of different deflecting facets of a common optical deflecting unit, and a plurality of scanned surfaces are scanned with the light beams deflected and scanned by the different deflecting facets, respectively.

Abstract: An optical scanning device in which an optical deflector scanningly deflects a light beam emitted from a light source and in which an imaging optical system images the scanningly deflected light beam onto a scan surface. The imaging optical system includes a transmission type imaging optical element and a reflection type optical element, which are disposed in this order from the optical deflector. The reflection type optical element reflects the scanningly deflected light beam in an off-normal light path towards the scan surface. To avoid interference with the off-normal path, a contour central line of the transmission type imaging optical element is positioned at one side of a principal ray of the light beam incident on the transmission type imaging optical element, which side is remote from the off-normal light path reflected by the reflection type optical element.

Abstract: An optical scanning device is configured in such a manner that, of four light beams for colors corresponding to black, cyan, magenta, and yellow, the angle of the reflection surface of the last folding mirror disposed in the optical path of a light beam corresponding to an image in black having the lowest brightness and the highest visibility is closest to vertical, and further, the angle of the reflection surface of the last folding mirror disposed in the optical path of a light beam corresponding to an image in yellow having the highest brightness and the lowest visibility is closest to horizontal. It is thus possible to reduce a color shift in the color image caused by reflecting a light beam having passed through the correction lens on the last folding mirror.

Abstract: An image forming apparatus, includes: a latent image carrier whose surface includes an effective image region spanning across a predetermined width in a main scanning direction and is driven in a sub scanning direction approximately orthogonal to the main scanning direction; a latent image former which has a light source and a deflection mirror oscillating, and deflects a light beam from the light source using the deflection mirror so as to scan the effective image region with the deflected light beam; and a scanning mode controller which switches selectively between a single-side scanning mode and a double-side scanning mode, the single-side scanning mode being a mode in which the light beam is scanned only in a first direction included in the main scanning direction, the double-side scanning mode being a mode in which the light beam is scanned in both the first direction and a second direction opposite to the first direction, wherein a condition to form latent images on the latent image carrier in the singl

Abstract: An optical scanning device includes plural light source devices, a deflecting device having deflecting surfaces, an input optical system and a plurality of imaging optical systems, wherein a plurality of scan surfaces are simultaneously scanned by the deflecting device, wherein each of the plurality of imaging optical systems includes at least one transmission type imaging optical element and at least one reflection optical element, wherein each of at least two light beams scanningly deflected by the different deflecting surfaces of the deflecting device passes through the at least one transmission type imaging optical element constituting the imaging optical system and is thereafter reflected by the at least one reflection optical element and, subsequently, it passes again through the transmission type imaging optical element, and wherein, after passing again through the transmission type imaging optical element, the at least two light beams scanningly deflected by the different deflection surfaces of the de

Abstract: According to the present invention, highly accurate adjustment of the angles and positions of optical elements constituting an optical scanning unit can be easily performed. The optical scanning unit comprises: a first mirror that reflects the light beams emitted from Y, C and M laser diodes; a second mirror that reflects the light beam emitted from a K laser diode and the light beams reflected by the first mirror; a cylindrical lens that acts on the light beams reflected by the second mirror; and a third mirror that reflects the light beams emitted from the cylindrical lens toward a polygon mirror. The second mirror is provided with an adjusting mechanism that can adjust the light beams in the main scanning direction, and the third mirror is provided with an adjusting mechanism that can adjust the light beams in the sub-scanning direction.

Abstract: An optical writing device includes a dichroic mirror and a deflection beam splitter. The dichroic mirror causes a light beam to pass therethrough or reflect depending on the wavelengths of the light beam. The deflection beam splitter causes a light beam to pass therethrough or reflect depending on a direction from which the light beam is received.

Abstract: A multi-beam optical scanning device which enables uniform scan line pitch and high precision image, includes a light source having plural light emitting members, a rotary polygonal mirror having a deflecting surface, a first optical system for imaging a light beam on the deflecting surface and a second optical system for imaging the light beam on a scan surface to be scanned, wherein the optical axis of the first optical system is disposed at a particular angle in a sub-scan section with respect to a plane perpendicular to the deflection axis of the deflecting surface, and wherein, with respect to the imaging magnification in the sub-scan section of the second optical system on the optical axis and between the deflecting surface and the scan surface, the imaging magnification at a scan start side is made large while the imaging magnification at the scan end side is made small or, alternatively, the imaging magnification at a scan start side is made small while the imaging magnification at the scan end side i

Abstract: An electrophotographic image forming apparatus senses amounts of color misregistration of toner images, which are formed using n-number (where n is a natural number and n=2 holds) of photosensitive bodies, when light beams from a plurality of light sources are made to deflect and scan across the n-number of photosensitive bodies by a single rotating polygonal mirror. The timing of light emission from the light sources is controlled in such a manner that light beams from the light sources will be deflected and scanned by mirror surfaces of the polygonal mirror, from among the plurality of mirror surfaces that form the polygonal mirror, such that the amount of color misregistration of every toner image will be less than (n?1)/n pixels.

Abstract: A common photodetecting unit detects a plurality of beams scanned by a plurality of polyhedral reflection mirrors provided in a multiple stages with a common rotation axis, and generates a synchronization detection signal based on detected beams. The reflection mirrors make a predetermined angle ?1 in a direction of rotation of the reflection mirrors. When time between two consecutive synchronization detection signals on a time line generated by the common photodetecting unit is ti, where i is a positive integer equal to or smaller than number of split beams, at least one of ti is different from others.

Abstract: Apparatus comprising a two-dimensional array of light sources (40) and a scanning device (26) arranged to scan light (14) emitted from the light sources (40) onto a medium (10) to generate a plurality of scan lines (52) on the medium (10), the light sources (24 and scanning device (26) being arranged such that a plurality of light sources (24) can be used to generate each scan line (52) of the plurality of scan lines (52).

Abstract: An optical recording apparatus includes a plurality of laser modules, an optical fiber array unit, a photosensitive member, and an optical system. Each laser module includes a light source and an optical fiber. The optical fiber array unit bundles a plurality of optical fibers to form an optical fiber array. The photosensitive member has a photosensitive surface. The optical system scans laser beams outputted from the array of the optical fiber array in a first direction on the photosensitive surface, the laser beams forming dots aligned in a second direction to form an angle with respect to the first direction.

Abstract: An optical scanning device includes a light source that emits a light beam, an optical deflector at which a light beam emitted from the light source is incident, the optical deflector deflecting the incident light beam, an optical system that guides the deflected light beam to surface to be scanned by the deflected light beam, a driving device that drives at least a portion of the optical deflector, a thermal storage member mounted on the driving device, the thermal storage member absorbing and storing heat generated by the driving device, thereby controlling a temperature gradient of the driving device, and a casing body that accommodates the light source, the optical deflector, the optical system, the driving device, and the thermal storage member.

Abstract: An optical scanning device including a light beam emission unit configured to emit a light beam, a main scanning line deflection unit configured to deflect the light beam in a main scanning direction to emit a scanning beam, a scanning lens configured to focus the scanning beam in the main scanning direction and a sub-scanning direction, a reflective optical element configured to deflect the scanning beam, a tilt adjustment unit configured to change a position of the reflective optical element to adjust a tilt of a scanning line of the scanning beam irradiating a target to be irradiated, and a curve adjustment unit configured to bend the reflective optical element to adjust a curve in the scanning line of the scanning beam irradiating the target to be irradiated.

Abstract: There is provided an image forming apparatus which is capable of reducing a period of time required for obtaining an image output, in the case of changing the image forming operation from a monochromatic image formation to a color image formation during execution of the image forming operation. A plurality of image forming units form images and overlap images the formed images onto a transfer material. A preparation for image formation is started in a first mode in which image formation is carried out by the plurality of image forming units while image formation is being carried out in a second mode in which image formation is carried out by at least one of the image forming units. The image formation is carried out in the first mode after the image formation in the second mode is completed.

Abstract: An optical scanning device includes a light source, a deflector, and an image-forming optical system. The deflector includes a deflecting surface for deflecting light beams in a main scanning direction. The image-forming optical system includes two relay lenses having a positive power in the main scanning direction. The relay lenses cause main light beams of light beams emitted from the light source to cross near the deflecting surface in the main scanning direction.

Abstract: An image forming apparatus including: a speed information detection unit detecting speed information corresponding to a rotational speed of a scanner motor; a first judgment unit judging if the scanner motor has arrived at a first reference speed being lower than a rotational speed in scanning within a first term; a second judgment unit judging if the scanner motor has arrived at a second reference speed being not lower than the first reference speed after the first term, when the first judgment unit judges that the scanner motor has not arrived at the first reference speed within the first term; and an image formation unit initiating an image formation process when the first judgment unit judges that the scanner motor has arrived at the first reference speed within the first term and when the second judgment unit judges that the scanner motor has arrived at the second reference speed.

Abstract: An optical scanning device includes a coupling optical system, a light source including a plurality of light emitting units for emitting light beams, and a deflector including a deflecting surface for deflecting the light beams. The coupling optical system is arranged on an optical path between the light source and the deflector so that the light beams enter the deflector at an angle with respect to a normal direction of the deflecting surface in a sub-scanning direction. The light emitting units are arranged two-dimensionally, and a distance between two light emitting units at opposite ends in a main scanning direction is smaller than a distance between two light emitting units at opposite ends in the sub-scanning direction.

Abstract: An optical scanning system includes a light source, a polygon mirror, a first optical system, a second optical system, and a monitoring device. The light source includes a plurality of light-emitting units. The first optical system is arranged on an optical path of light beams, and guides the light beams from the light source to the polygon mirror. The second optical system guides the light beams deflected by the polygon mirror to a photosensitive drum. The monitoring device monitors light amount of light beams emitted from the light-emitting units. An optical axis of a coupling lens and a cylindrical lens is inclined from a normal of a deflection-reflection surface of the polygon mirror with respect to a sub-scanning direction.

Abstract: An image forming apparatus including: an optical scanning unit for deflecting and scanning a light on a photosensitive body, the optical scanning unit having: a light source for emitting the light; a deflection section that deflects the emitted light; a driving section that drives the deflection section; and a temperature detecting section that detects the temperature of the driving section or the temperature in vicinity of the driving section; a developing section that develops an electrostatic latent image by depositing a developer on the electrostatic latent image formed on a surface of the photosensitive body by the optical scanning unit; a transfer section that transfers the developer deposited on the surface of the photosensitive body to a recording medium; and a controller for changing a drive speed of the driving section based on the temperature detected by the temperature detecting section.

Abstract: A light scanning unit to scan light beams to a plurality of photoconductive bodies. The light scanning unit includes: a light source to emit a plurality of beams; a beam-deflecting unit to form scanning beams from the beams emitted by the light source; a plurality of reflecting mirrors to reflect the scanning beams; and an optical imaging system to focus the reflected scanning beams onto each of the photoconductive bodies. The scanning beams can be reflected by the reflecting mirrors at a first angle that is between about 60° and about 90° or at a second angle that is supplementary to the first angle.

Abstract: A multi-beam scanner includes light sources, a deflector deflecting the beams emitted from the light sources at an equiangular velocity, a scanning image-forming optical system guiding the deflected beams to a surface so as to be formed into light spots on the scanned surface, a light receiving device receiving the beams deflected toward optical write-in starting portions on the scanned surface as synchronizing beams, and a synchronizing beam optical system guiding the beams deflected toward the optical write-in starting portions on the scanned surface to the light receiving device. The scanning image-forming optical system includes two or more scanning positive lenses, with a region having a positive power in a main scanning direction on an optical write-in starting side, and each deflected beam received by the light receiving device passes through one or more but not all of the scanning positive lenses to be guided to the light receiving device.

Abstract: A printer has a laser emitter for emitting a laser beam to irradiate a surface of a photosensitive member; a reflector, disposed at a position on a laser beam path defined by the laser emitter and the photosensitive member, for reflecting the laser beam emitted by the laser emitter to direct the reflected laser beam to a target position on the surface of the photosensitive member; a reflective mirror driver for reciprocating the reflector in such a manner that the laser beam travels along a scanning line on the surface of the photosensitive member in a direction for scanning; and an emission controller for controlling the laser emitter to selectively emit the laser beam along the scanning line in the forward direction or the backward direction defined by the movement of the reflector driven by the reflective mirror driver.

Abstract: An optical scanning device includes a light-source unit that emits a plurality of light beams, a deflector that deflects the light beams, and an image-forming optical system that receives the light beam deflected by the deflector and forms a spot image on photoconductors. The image-forming optical system includes a first scanning lens that allows only a corresponding light beam to pass and is arranged to form, upon receiving a virtual light beam, the spot image on the photoconductor with a not-curved line. The virtual line lies between a pair of light beams that travels in one of areas separated by a reference plane that is parallel to a sub-scanning direction and on which a normal line to a deflection plane of the deflector falls.

Abstract: In a bi-directionally scanning electrophotographic (EP) device, methods and apparatus include storing alignment information. In one aspect, pre-characterization parameters of the EP device are stored in memory, such as NVRAM, resistant to the removal of power. In another, actual parameters of the EP device are learned during calibration and stored in the same memory. A controller has local or remote access to the memory and makes comparisons of the pre-characterized and learned parameters to implement corrections. Especially, scan alignment corrections are implemented to alter future scanning of scan lines of latent images on a photoconductor whereby the scan lines are formed in alternating directions. Certain contemplated parameters include, but are not limited to, a scan detect to print distance from a sensor to the start of imaging, temperature, pressure, a scanning mechanism drive signal parameter, such as pulse width, or sensor delay information.

Abstract: An optical component bowing device is configured to include a bending moment generating structure that generates a bending moment in a supported portion of an optical component that reflects or shapes a light beam.

Abstract: Methods and apparatus include improving print quality of a bi-directionally scanning electrophotographic (EP) device, such as a laser printer or copy machine, according to ambient pressure in which operated. A moving galvanometer or oscillator reflects a laser beam to create scan lines of a latent image in opposite directions. A damping of the motion occurs per air density implicated by temperature and pressure, where the pressure changes occurring especially from altitude changes. During use, a drive signal, such as a pulse train, moves the galvanometer or oscillator at or near its resonant frequency. Based on a parameter of the drive signal, such as pulse width, the ambient pressure can be made known. In general, a high-pressure environment requires a relatively longer pulse width to resonate the galvanometer or oscillator in comparison to a shorter pulse width for a low-pressure environment. Corrections to print quality stem from the determined ambient pressure.

Abstract: A laser scanning unit includes a housing; an optical system disposed in the housing and including an optical source which emits a laser beam, a polygonal mirror which scans the laser beam, and a plurality of optical elements which image the laser beam on an image surface; a motor disposed in the housing and which rotates the polygonal mirror; and a motor drive chip disposed outside of the housing and which uses a sensorless algorithm to control a rotation speed of the motor.

Abstract: Multiple light beams are reflected by a resonant oscillator through an optical system onto light sensitive drums of a printing system. Information is encoded onto the beams, and an image is printed based on the encoded information. Preferably four beams and four drums are used to print four colors. The oscillator includes an oscillating plate mounted on the torsion springs for resonant oscillation. A magnet is mounted on the oscillating plate and an oscillating magnetic field oscillates the magnet and the plate. Sensors detect the position of at least one of light beam to synchronize the operation and speed of the encoder, drums and oscillator. The oscillator may include multiple reflective surfaces on one or more sides of an oscillating plate, and one or more beams may be reflected from each surface.

Abstract: An image forming apparatus includes an image bearing member having a photosensitive surface and an optical writing apparatus generating a laser beam modulated according to image data. The optical writing apparatus includes a housing, an optical deflector, an f-theta lens and a separator. The optical deflector is configured to rotate to deflect the laser beam. The f-theta lens is configured to correct the laser beam deflected by the optical deflector and to transmit a corrected laser beam towards the image bearing member. The separator is configured to separate an inside space of the housing into at least two sections including a first section in which the optical deflector is mounted and a second section in which the f-theta lens is mounted. The separator includes a heat resistant transparent plate disposed at a position of crossing passage of the laser beam between the optical deflector and the f-theta lens.

Abstract: A light scanning apparatus comprising a photosynthesis device having a first light source unit and a second light source unit with a plurality of light sources spaced at equal intervals side by side in one direction, respectively for emitting rays in parallel from the plurality of light sources, a photosynthesis device for synthesizing transmitted rays from the first light source unit and reflected rays from the second light source unit on a single light path, and a light receiving device for focusing first synthesized rays synthesized by the photosynthesis device through an imaging lens, and an optical deflecting device for deflecting and scanning second synthesized rays synthesized by the photosynthesis device, and the second synthesized rays passed through the optical deflecting device is being externally emitted, wherein the photosynthesis device and the light receiving device are displaced relative to the optic axis of the first synthesized rays so as to position focused spots of the first synthesized ra

Abstract: Electrical interference between resonant, drive and line frequencies in a drive is reduced by selecting the resonant frequency to be non-harmonically related to the drive and line frequencies. The drive is of beneficial use in a lightweight, compact image projection module operative for causing selected pixels in a raster pattern to be illuminated to produce a non-distorted image of high resolution of VGA quality in color.

Abstract: An image forming apparatus is configured, in performing changing of a rotation speed of a scanner motor and forming of an image density adjustment patch in the same page interval, to change the rotation speed of the scanner motor before forming the image density adjustment patch.

Abstract: A laser beam source that emits a laser beam includes a reflecting unit that has a plurality of reflecting members and reflects the laser beam emitted from the laser beam source, a deflecting and scanning unit that deflects and scans with the laser beam reflected by the reflecting means, and an adjusting unit that moves at least part of the reflecting members, and adjusts the size of the laser beam entering the deflecting and scanning unit.

Abstract: A light beam scanner irradiates surfaces of respective of different image carriers with respective of plural light beams having been subjected to constant angular velocity deflection by a deflecting member and constant velocity deflection by a transformation member. Any one of the plural light beams except a light beam incident on the deflecting member at a widest incident angle corresponds with an image formed of a color material which is lowest in lightness.

Abstract: A laser scanning unit includes a light source for emitting a plurality of laser beams, a rotating polygon mirror for deflecting the plurality of laser beams in a predetermined direction, an f? lens for transmitting the deflected laser beams to be scanned onto the surfaces of a plurality of photosensitive drums, and a beam splitter disposed at a rear end of the f? lens for splitting the laser beams. The laser scanning unit may be used for a tandem image forming apparatus.

Abstract: The invention aims at provision of an optical scanner in which an optics required for equalizing an optical magnification in a scanning range is produced with high accuracy, so that intervals among a plurality of scanning lines on a to-be-scanned surface are even in the scanning range. The scanning optics includes a refraction surface and a reflection surface whose sub-scanning-direction curvature radii vary continuously. The reflection surface is disposed on the to-be-scanned surface side of the refraction surface. The curvature radius of the reflection surface varies symmetrically with respect to the optical axis, and the curvature radius of the refraction surface varies asymmetrically with respect to the optical axis.

Abstract: An object of the present invention is to prevent deterioration of image quality caused by ghost light generated from components of a scanning optical apparatus. In the present invention, an image writing light flux is related with a position at which ghost light appears and the exposure amount of the ghost light and a ghost light exposure amount on a surface to be scanned is calculated on comparison with an actual image signal, and the light quantity or the pulse width of a light flux emitted from a light source is controlled based on the calculated ghost light exposure amount.

Abstract: An optical scanner has a deflector, a coupling lens, a cylindrical lens, a plate through which light to and from the deflector pass, and an optical system which condenses the light deflected on a surface to be scanned. Bundles of light beams incident on the deflector have an angle between the bundles in a rotating plane of the deflector, and expressions 0.6<(?1max??)/(?2+?)<1.4, and 0.6<(?1min??)/(?2+?)<1.4, are satisfied, where ?1max and ?1min are maximum and minimum average angles of incidence on the deflecting surface, ?2 is a half-view angle, and ? is an angle of inclination of the plate in the rotating plane with respect to a main scanning direction.

Abstract: An optical writing unit includes a housing, at least one light source, and/or at least one aperture member. In at least one embodiment, the at least one light source emits a light beam, and the at least one aperture member passes the light beam emitted from the at least one light source. In at least one embodiment, the at least one aperture member is integrally formed with the housing and/or the at least one light source is directly fixed to the housing by applying pressure.

Abstract: The present invention uses a pattern that enables image quality maintaining control to be performed at a resolution lower than that used for a normal image forming process. Thus, during an initial operation upon power-on, the image quality maintaining control is performed at the resolution lower than that used for the normal image forming process.

Abstract: An optical scanner includes a light source that emits a light beam, a deflection unit that deflects the light beam, an optical unit that introduces the light beam to a target surface, a housing unit that stores these components, and a member that contacts the light source and/or the optical unit. The light source and/or the optical unit changes in attitude due to a temperature change while the optical scanner is operating. The member extends or contracts according to the temperature change so as to reduce the change of the attitude.

Abstract: An optical scanning device is configured in such a manner that, of four light beams for colors corresponding to cyan, magenta, yellow, and black, the number of folding mirrors disposed in the optical path of a light beam corresponding to an mage in yellow having the highest brightness and the lowest visibility is the greatest number, and further, the number of the folding mirrors disposed in the optical path of a light beam corresponding to an image in black having the lowest brightness and the highest visibility is the least number. It is thus possible to reduce unevenness in color in the color image resulting from the folding of light beams by the folding mirrors.

Abstract: An even number of reflection mirrors reflecting a light beam in the sub-scanning direction are disposed on an optical path from a deflecting reflection surface of an optical deflector to a corresponding surface to be scanned, for a light beam that is incident on the deflecting reflection surface from one side of a line normal to the deflecting reflection surface in the sub-scanning direction. An odd number of reflection mirrors reflecting the light beam in the sub-scanning direction is disposed on the optical path, for a light beam that is incident on the deflecting reflection surface from the other side of the line normal to the deflecting reflection surface in the sub-scanning direction.