JP5218095B2 - Optical writing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical writing device (optical scanning device) in an image forming apparatus such as a copying machine, a printer, and a facsimile machine.

  Currently, market demand for image forming apparatuses includes small size, light weight, and low cost. In particular, since a color image forming apparatus has a large number of components, it is much larger than a conventional monochrome apparatus, and there is a high demand for downsizing.

  An optical writing device (optical scanning device) that uses a plurality of light beams used in an image forming apparatus that has been commercially available in the past, refracts the light beam by a plurality of reflection mirrors, thereby supporting each image. Although the surface to be scanned is irradiated, the optical writing device tends to become larger in the thickness direction because the optical path is folded three-dimensionally using a plurality of mirrors. In particular, in a color image forming apparatus using a plurality of photoconductors, it is necessary to prevent an optical path of a light beam corresponding to each photoconductor or interference of an optical element, so that the thickness is very large in the thickness direction.

  By the way, the housing of the optical writing apparatus for positioning and holding the optical element is generally a box type because the light beam is scanned by the deflector. The rigidity of the box-type housing greatly depends on the side surface portion (wall portion) of the box, and the rigidity decreases from the side surface portion (wall portion) toward the center portion (center portion of the plane). In particular, in the case of a tandem type that has been widely adopted in recent years in color image forming apparatuses, for example, as shown in FIG. 11 of Patent Document 1, a plurality of photosensitive members are arranged side by side. Since the size in the scanning direction (the width direction of the image forming apparatus) is inevitably increased, the housing of the optical writing apparatus is also increased in size. The box-type housing of the optical writing device that is large in the sub-scanning direction has difficulty in securing rigidity, and an attempt to obtain the required rigidity causes an increase in weight and cost.

  A technique for increasing the rigidity of the housing of the optical writing device is proposed by, for example, Patent Document 2 or Patent Document 3. However, the one described in Patent Document 2 uses the shaft of the rotating deflector as a reinforcing member of the housing, and reinforces the central portion of the housing where the rotating deflector is disposed. Further, the one described in Patent Document 3 is intended to reinforce the central portion of the housing where the scanner motor, the light source, and the like are disposed, and similarly, a reinforcing member is disposed in the central portion of the housing. These optical writing apparatuses described in Patent Documents 2 and 3 are for a monochrome image forming apparatus for writing on a single photosensitive member and are relatively small optical writing apparatuses. In the proposed reinforcing method, In the case of a housing that is large in the sub-scanning direction, such as a housing for an optical writing device that supports a tandem type, it is difficult to obtain the required rigidity.

  It is an object of the present invention to provide an optical writing device that solves the above-described problems in the conventional optical writing device, realizes a reduction in thickness, and can uniformly improve the rigidity of the entire housing.

According to the present invention, there is provided an optical writing apparatus that scans a surface to be scanned of an image carrier by deflecting a light beam emitted from a light source by a deflector and reflecting the deflected light beam by a reflecting mirror. A fixing member for connecting and fixing the housing and the upper lid of the optical case including the housing and the upper lid, and the fixing member is positioned at an intermediate position between the end of the housing and the deflector in the sub-scanning direction. The fixed member has a beam passage opening for allowing the light beam deflected by the deflector to pass therethrough, and the fixed member is provided so as to hold at least one optical element disposed in the optical case. It is solved by being.

The light source includes a plurality of light sources that emit light beams having the same polarization direction and different wavelengths, and the light beams emitted from the plurality of light sources are combined on the same axis in the sub-scanning direction and deflected by the deflector. And a first beam separating means arranged so that each of the light beams deflected by the deflector enters, and transmitting or reflecting the light beam according to the polarization direction of the beam, and after passing through the first beam separating means The light beam is arranged between a second beam separation unit that transmits or reflects each light beam depending on its wavelength, and between the first beam separation unit and the second beam separation unit, and the polarization direction of the light beam is π / 4 and a quarter-wave plate for rotating the the second light beam transmitted through the beam splitting means to scan one image carrier, light Bee reflected by the second beam separating means The is reflected on the first beam separating means preferably scanning the other one of the image bearing member.

The fixing member is preferably provided so as to be able to hold the first beam separation means or the second beam separation means.
According to the present invention, the above problem is solved by an image forming apparatus including the optical writing device according to any one of claims 1 to 3 .

  Further, it is preferable that the tandem type full-color device is provided with four image carriers as scanning objects scanned by the optical writing device.

  According to the optical writing device of the present invention, the fixing member that connects and fixes the housing of the optical case and the upper lid is disposed at an intermediate position between the end of the housing and the deflector in the sub-scanning direction. Even in the writing apparatus, the optical case can be reinforced in a balanced manner in the sub-scanning direction, and the rigidity of the optical case can be improved efficiently and evenly.

In addition , since the fixing member has a beam passage opening that allows the light beam deflected by the deflector to pass therethrough, the fixing member can be arranged without blocking the light beam, and the optical case can be reinforced widely in the main scanning direction. It becomes.

Furthermore , since the fixing member is provided so as to hold at least one optical element, the holding member of the optical element and the fixing member can be used together, and the number of parts and the cost can be reduced.

With the configuration of the second aspect, the writing device that scans the plurality of image carriers can be thinned.

According to the configuration of the third aspect, the number of parts and the cost can be reduced by holding the beam separating means on the fixing member.
According to the image forming apparatus of the fourth aspect , by providing the thin optical writing device, it is possible to reduce the size of the image forming device in the vertical direction and to reduce the size of the device. Since the optical case of the writing device has high rigidity, high-quality writing can be performed.

According to the configuration of the fifth aspect , a tandem type image forming apparatus capable of forming a full-color image in a short time can be realized by reducing the vertical size of the image forming apparatus with a thin optical writing device. Further, even a thin and wide tandem type optical writing apparatus can perform high-quality writing due to the high rigidity of the optical case.

1 is a cross-sectional view schematically showing a main part configuration in an example of an optical writing device according to the present invention. It is a top view of the optical writing device. It is a front view which shows a mode that the optical element was hold | maintained with the fixing member. 3A and 3B are three views of the fixing member, in which FIG. 3A is a perspective view, FIG. 3B is a front view, and FIG. It is a perspective view which shows a mode that a fixing member is screwed and fixed. It is sectional drawing which shows a mode that the fixing member holding the dichroic mirror was fixed to the optical case. It is sectional drawing which shows a mode that the fixing member holding a polarizing beam splitter and a quarter wavelength plate was fixed to the optical case. It is sectional drawing which shows a mode that the fixing member holding a quarter wavelength plate was fixed to the optical case. It is sectional drawing which shows typically the principal part structure of an optical writing device provided with two rotating polygon mirrors. 1 is a schematic configuration diagram of a direct transfer tandem full-color printer that is an example of an image forming apparatus including an optical writing device according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing a main configuration of an example of an optical writing device according to the present invention. FIG. 2 is a plan view thereof. The optical writing apparatus 10 of this example shown in these drawings includes a semiconductor laser 1, a collimating lens 2, an aperture 3, a cylindrical lens 4, a polygon mirror 5 which is a rotating polygon mirror (deflector), an fθ lens 6, and a polarizing beam splitter. 7 (first beam separating means), a quarter wavelength plate 8, a dichroic mirror 9 (second beam separating means), a reflecting mirror 11, and the like. These components are a housing 21 and an upper lid (upper housing). It is arranged in an optical case 20 composed of 22. As can be seen from FIG. 1, in the optical writing device 10 of the present embodiment, the light beam deflected by the polygon mirror 5 is a single reflecting mirror (reflecting mirror 11) arranged on one side of the polygon mirror 5 in the sub-scanning direction. Therefore, the optical writing apparatus is thin and has a small size in the thickness direction.

  As shown in FIG. 3, the dichroic mirror 9 as the second beam separating means is pressed against and held by the fixing member 30 by biasing members 31 and 32 attached to the fixing member 30. The urging members 31 and 32 use leaf springs in this example. The fixing member 30 is a member having an “L” -shaped cross section, and a beam passage opening 30 a for allowing the light beam transmitted through the dichroic mirror 9 to pass through is provided in the vertical side portion.

  4A and 4B are three views of the fixing member 30, wherein FIG. 4A is a perspective view, FIG. 4B is a front view, and FIG. 4C is a side view. Screw holes 30b for screwing the fixing member 30 to the housing 21 and the upper lid 22 are provided on both sides in the main scanning direction on the upper surface of the fixing member 30 and the upper surface of the bottom side. FIG. 5 is a perspective view showing how the fixing member 30 is fixed by the screw 33. In FIG. 5, the housing 21 and the upper lid 22 are not shown. Also, the urging members 31 and 32 for holding the dichroic mirror 9 are not shown.

  FIG. 6 is a cross-sectional view showing a state in which the fixing member 30 holding the dichroic mirror 9 is fixed to the housing 21 and the upper lid 22. In this figure, the other optical elements are not shown. As shown in FIG. 6, the fixing member 30 is screwed and fixed to the housing 21 and the upper lid 22, so that the fixing member 30 is connected and fixed to the housing 21 and the upper lid 22. ). As can be seen from the figure, the fixing member 30 is arranged at an intermediate position (sub-scanning direction) between the end of the housing 21 and the polygon mirror 5. In the optical writing device 10 of the present embodiment, one dichroic mirror 9 is arranged on each side of the polygon mirror 5, and two fixing members 30, 30 are screwed to the housing 21 and the upper lid 22, respectively. Since it is fastened and fixed, the wide optical case 20 can be reinforced with good balance at two locations in the sub-scanning direction, and the rigidity of the optical case 20 can be improved efficiently and evenly. The fixing member 30 can be made of any suitable material as long as it is a member formed of a rigid body such as metal, and the shape thereof is also the holding of the optical element (here, the dichroic mirror 9), the housing 21, An appropriate shape suitable for fixing to the upper lid 22 can be obtained.

  FIG. 7 is a cross-sectional view showing an embodiment in which a fixing member 30 </ b> B that holds the polarizing beam splitter 7 and the quarter-wave plate 8 is screwed and fixed to the housing 21 and the upper lid 22. In this figure, the other optical elements are not shown. Also in the present embodiment, the fixing member 30B acts as a reinforcing member that improves the strength (rigidity) of the optical case 20, and the optical case 20 is reinforced in a well-balanced manner at two locations in the sub-scanning direction. Can be improved efficiently and evenly.

  FIG. 8 is a cross-sectional view showing an embodiment in which the polarizing beam splitter 7 and the quarter-wave plate 8 are independent from each other, and a fixing member 30C that holds the quarter-wave plate 8 is screwed and fixed to the housing 21 and the upper lid 22. It is. Also in the present embodiment, the fixing member 30C acts as a reinforcing member that improves the strength (rigidity) of the optical case 20, and the optical case 20 is reinforced in a well-balanced manner at two locations in the sub-scanning direction. Can be improved efficiently and evenly.

  In the configuration of FIG. 8, a convex portion 22a that protrudes downward and contacts the upper surface of the fixing member 30C is provided at a position corresponding to the fixing member 30C of the upper lid 22. With this configuration, when the upper lid 22 is fixed to the fixing member 30C, the rigidity of the upper lid 22 is improved, and the strength of the optical case 20 is further improved. In another embodiment, the upper cover 22 may be provided with a convex portion 22a.

  In each of the above embodiments, the dichroic mirror 9, the polarization beam splitter 7, the quarter wavelength plate 8, and the quarter wavelength plate 8 are held by the fixing member 30, but other configurations such as an fθ lens are used. A configuration in which the optical element is held by a fixing member is also possible. Even in that case, the rigidity of the optical case 20 can be improved by the fixing member.

Next, a writing operation in the optical writing device of this embodiment will be described. In addition, although demonstrated in the Example of FIGS. 1-6 here, it is the same also in the case of each Example of FIG.
In the optical writing apparatus of the present embodiment, semiconductor lasers 1a and 1b that emit light beams having different wavelengths are used, and those having a wavelength band corresponding to the dichroic mirror 9 as the light separating means are used. It is done. Similarly, semiconductor lasers 1c and 1d that emit light beams having different wavelengths are used, and those having a wavelength band corresponding to the dichroic mirror 9 as the light separating means are used.

  Since the operation of the components arranged on each side of the polygon mirror 5 is the same, the description will be made mainly based on the left part here, but scanning is performed by the semiconductor lasers 1c and 1d shown on the right side of the polygon mirror 5. The same applies to the parts to be performed.

  Light beams having the same polarization direction and different wavelengths emitted from two different light sources, the semiconductor lasers 1a and 1b, pass through the collimating lenses 2a and 2b, the apertures 3a and 3b, and the cylindrical lenses 4a and 4b in the same sub-scanning direction. It is combined with the shaft and reflected by the polygon mirror 5 as the deflecting means, passes through the fθ lens 6 and passes through the polarization beam splitter 7 as the beam separating means. The polarization beam splitter 7 separates light according to the polarization direction due to the difference in the rotation angle of the light beam by π / 2, and has a characteristic of transmitting or reflecting depending on the beam entrance direction.

  Two beams (light beams having the same polarization direction and different wavelengths) that have exited the fθ lens 6 and passed through the polarization beam splitter 7 pass through the quarter-wave plate 8. The quarter-wave plate 8 rotates the polarization direction of the light beam by π / 4, and the two light beams pass through the quarter-wave plate 8 so that they are π / 4 at the time of emission. In a state where the light beam is rotated only by one beam, one beam is transmitted and the other one beam is reflected by the dichroic mirror 9 which is a multilayer dielectric mirror placed perpendicular to the beam. The dichroic mirror 9 transmits a light beam in a certain wavelength band and reflects a light beam in a certain wavelength band. That is, the two light beams are separated into reflected light and transmitted light by the dichroic mirror 9.

  Now, the light beam transmitted through the dichroic mirror 9 is reflected by the reflecting mirror 11 and irradiated onto the surface to be scanned of the photosensitive member 101a. On the other hand, the light beam reflected by the dichroic mirror 9 returns the same optical path and passes through the quarter-wave plate 8 again, so that the polarization direction is rotated again by π / 4. The light beam enters the polarization beam splitter 7 in a state where the light beam is rotated. The light beam rotated by π / 2 from that at the time of emission is reflected by the polarization beam splitter 7 and applied to the surface to be scanned of the photosensitive member 101b. In this manner, the light beams emitted from the semiconductor lasers 1a and 1b are respectively guided to the photosensitive member 101a and the photosensitive member 101b, and scan the respective photosensitive members.

  In this example, the two light beams emitted from the semiconductor lasers 1 a and 1 b are both linearly polarized P waves, for example, and one light beam is rotated by π / 4 by the quarter-wave plate 8. In the state of circularly polarized light, the light passes through the dichroic mirror 9 and is irradiated onto the photosensitive member 101a. The other light beam is rotated by π / 4 by the quarter-wave plate 8 to become circularly polarized light, then reflected by the dichroic mirror 9 and again passes through the quarter-wave plate 8 to change the polarization direction again to π. The photosensitive member 101b is irradiated in a state of being rotated by / 4 to be a linearly polarized S wave.

  Similarly, also on the right side portion of the polygon mirror 5, the light beams emitted from the semiconductor lasers 1c and 1d are respectively guided to the photoconductor 101c and the photoconductor 101d to scan each photoconductor. In this example, the optical path lengths from the respective semiconductor lasers 1a, 1b, 1c, and 1d, which are light sources, to the respective photoreceptors 101a, 101b, 101c, and 101d are provided to be equal. In this example, the incident angles of the respective light beams to the surface of the photosensitive member are configured to be equal. Further, in this example, the scanning plane by the polygon mirror 5 and the plane connecting the centers of the plurality of photosensitive drums (in this example, the photosensitive bodies 101a, 101b, 101c, and 101d) are configured to be parallel.

  Now, in order to separate the two light beams by the dichroic mirror 9 which is a multilayer dielectric mirror, the wavelengths of the two light beams need to be different. Although the boundary between reflection and transmission differs depending on the added multilayer film, for example, a dichroic mirror having a boundary near the wavelength of 750 nm can be preferably used. In that case, it is necessary to select a wavelength band before and after the boundary for the light beam to be used. When using a dichroic mirror having a boundary near the wavelength of 750 nm, as an example, visible light having a wavelength of about 650 nm and infrared light having a wavelength of about 780 nm can be selected (visible light having a wavelength of about 650 nm is selected. A semiconductor laser that emits light and a semiconductor laser that emits infrared light having a wavelength of about 780 nm can be used as the semiconductor lasers 1a and 1b). The same applies to the semiconductor lasers 1c and 1d. The dichroic mirror, which is a multilayer dielectric mirror, includes a hot mirror (heat ray reflective type) and a cold mirror (heat ray transmissive type), and either type can be employed in the present invention.

Next, a second embodiment of the optical writing device will be described with reference to FIG. This optical writing apparatus is provided with two polygon mirrors 5 as rotary polygon mirrors.
As shown in FIG. 9, the optical case 20B has partition walls 21c and 22c formed at the center in the sub-scanning direction of the housing 21 and the upper lid 22, and the upper surface of the partition wall 21c of the housing when the upper lid 22 is closed. And the lower surface of the partition wall 22c of the upper lid 22 come into contact with each other. Accordingly, the inside of the optical case 20B is divided into two parts on the left and right in the drawing by the partition walls 21c and 22c. In the figure, an optical element that performs scanning by the polygon mirror 5A is disposed in the left optical case, and an optical element that performs scanning by the polygon mirror 5B is disposed in the right optical case in the figure. Light beams from the semiconductor lasers 1a and 1b (not shown) arranged in the left case are scanned by the polygon mirror 5A, and light beams from the semiconductor lasers 1c and 1d (not shown) are scanned by the polygon mirror 5B. Since the write operation is the same as that of the previous embodiment, the description thereof will be omitted and will be omitted.

  In the example shown in FIG. 9, the dichroic mirror 9 is held by the fixing member 30D, and the fixing member 30D is fixed by screwing the housing 21 and the upper lid 22, thereby reinforcing the optical case 20B in a well-balanced manner and increasing the rigidity of the optical case. Can be improved. As described in each example of the previous embodiment, another optical element can be held by a fixing member. Even in that case, the rigidity of the optical case can be improved by the fixing member.

  The optical writing apparatus of the above two embodiments has a configuration in which light beams having different wavelengths emitted from a pair of light sources are separated by the first and second separation means and guided to the respective photoreceptors. The height of the device (optical scanning device) is not increased, and a thin optical writing device can be realized. Further, it can be suitably used for a tandem type full-color image forming apparatus. Even in the case of an optical writing device for a full-color image forming apparatus that distributes four light beams to four photosensitive members (an optical writing device that is large in the sub-scanning direction), the optical member is optically fixed by a fixing member 30 that holds an optical element. Since the case can be effectively reinforced with a good balance, the rigidity of the optical case can be improved.

  Finally, an example of an image forming apparatus including the optical writing device according to the present invention will be described. The image forming apparatus shown in FIG. 10 is a direct transfer type tandem type full-color printer, and four image forming units 100 (Y, C, M, K) are arranged at substantially the center of the apparatus main body. The image forming units 100 (Y, C, M, K) corresponding to the respective colors of yellow, cyan, magenta, and black are arranged in parallel along the upper running side of the transfer conveyance belt 108. The transfer conveyance belt 108 wound around the support rollers 106 and 107 and the like is driven to run counterclockwise in the drawing. A registration roller 109 is disposed on the side of the right support roller 107, and a fixing device 110 is disposed on the side of the left support roller 106.

  Each image forming unit 100 has the same configuration except for the color of the toner to be handled, and includes a photosensitive drum 101 as an image carrier. Around the photosensitive drum 101, a charging unit 102, a developing device 103, and the like are arranged, and a transfer roller 105 as a transfer unit is provided inside the transfer conveyance belt 108 so as to face each photosensitive drum 101. ing. The developing device 103 is provided with a toner storage container 104. In the figure, among the four image forming units, only the black image forming unit 100K is representatively given a reference numeral for each device constituting the image forming unit.

  An optical writing device 10 is provided at the top of the device above the four image forming units 100. The optical writing device 10 corresponds to a four-color full-color image forming device and has been described above. The optical writing device 10 irradiates the surface of the photosensitive drum 101 of each color image forming unit with a laser beam L that is optically modulated based on image information.

  A sheet feeding tray 130 for loading sheets is disposed at the lower part of the apparatus, and a sheet feeding apparatus 131 for feeding sheets from the sheet feeding tray is provided. Details of the separation mechanism and the like are omitted.

An image forming operation in the color printer configured as described above will be briefly described.
The photosensitive drum 101 of the image forming unit 100 is rotated in the clockwise direction in the drawing by a driving unit (not shown), and the surface of the photosensitive drum 101 is uniformly charged to a predetermined polarity by the charging unit 102. The charged photoconductor surface is irradiated with laser light from the optical writing device 10, whereby an electrostatic latent image is formed on the photoconductor drum 101 surface. At this time, the image information exposed on each photosensitive drum 101 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. Each color toner is applied from the developing device 103 to the electrostatic latent image formed in this way, and visualized as a toner image.

  On the other hand, paper is fed from the paper feed tray 130 and the fed paper is once abutted against the registration roller pair 109. The paper is sent out in synchronism with the visible image, and is sucked and conveyed by the belt 108. Each time the paper reaches the transfer position facing each photoconductor drum 101, the toner images of the respective colors are sequentially transferred onto the paper by the action of the transfer means 105. In this way, a full-color toner image is carried on the paper.

  Note that any one of the image forming units 100 can be used to form a single-color image or a two-color or three-color image. In the case of monochrome printing, image formation is performed using the rightmost black (K) unit in the drawing among the four image forming units.

  The residual toner adhering to the surface of the photosensitive drum 101 after the toner image is transferred is removed from the surface of the photosensitive drum by a cleaning unit (not shown), and then the surface is subjected to the action of a static eliminator (not shown) so that the surface potential is Initialized to prepare for the next image formation.

  The sheet on which the toner image has been transferred is separated from the transfer conveyance belt 108 and sent to the fixing device 110, where the toner image is fused and fixed on the sheet by heat and pressure. The fixed paper is discharged out of the apparatus and stacked on a paper discharge tray (not shown).

  Since the optical writing device 10 is thin and thin as described above, the optical writing device 10 can be arranged in a limited space inside the image forming apparatus. The effect of reducing the thickness in the direction is great. In addition, the optical housing of the optical writing device is configured in a simple square box shape, so it is not a complicated shape like the conventional optical housing, making it easier to manufacture the housing and reducing costs by reducing manufacturing procedures. In addition, manufacturing time can be shortened. Therefore, it is possible to contribute to cost reduction of the image forming apparatus.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. For example, the optical element held by the fixing member is arbitrary, and a plurality of optical elements may be held using a plurality of fixing members. The shape and material of the fixing member are arbitrary. The size and shape of the light beam passage opening provided in the fixing member can be appropriately set.

  Further, as each light source and the second beam separating means (dichroic mirror), those capable of separating a plurality of light beams in a combination of both can be appropriately employed. Also, the first beam separating means can be of an appropriate configuration. In addition, the incident angle of the light beam to the scanning target can be set as appropriate. The photosensitive member to be scanned is not limited to a drum shape, and a belt-like photosensitive member is also possible.

  The image forming apparatus is not limited to the direct transfer method, but may be an intermediate transfer method. The order of colors in the tandem type is also arbitrary. In addition, the present invention can be applied not only to a full-color machine of four colors but also to a multi-color machine using a plurality of colors, for example, two colors of toner. The configuration of each part of the image forming apparatus is also arbitrary. Of course, the image forming apparatus is not limited to a printer, and may be a copier, a facsimile machine, or a multifunction machine having a plurality of functions.

  The present invention can be suitably used for image forming apparatuses such as copying machines, printers, and facsimiles.

1a, 1b, 1c, 1d Semiconductor laser 5 Polygon mirror (rotary deflector)
6 fθ lens 7 polarizing beam splitter 8 quarter wave plate 9 dichroic mirror 10 optical writing device (optical scanning device)
11 Reflector (reflecting means)
20 Optical case 21 Housing 22 Upper lid (upper housing)
30 Fixing member (reinforcing member)
31, 32 Energizing member 100 Image forming unit 101 Photoconductor

JP 2008-145939 A JP 2001-255487 A Japanese Patent Laid-Open No. 2001-117039

Claims (5)

An optical writing device that deflects a light beam emitted from a light source by a deflector, reflects the deflected light beam by a reflection mirror, and scans a scanned surface of an image carrier,
A fixing member for connecting and fixing the housing and the upper lid of the optical case comprising a housing and an upper lid, the fixing member being disposed at an intermediate position between the end of the housing and the deflector in the sub-scanning direction ;
The fixing member has a beam passage opening through which the light beam deflected by the deflector passes,
The optical writing apparatus , wherein the fixing member is provided so as to hold at least one optical element disposed in the optical case . The light source includes a plurality of light sources that emit light beams having the same polarization direction and different wavelengths, and the light beams emitted from the plurality of light sources are combined on the same axis in the sub-scanning direction and deflected by the deflector. ,
A first beam separating unit arranged so that each of the light beams deflected by the deflector enters, and transmitting or reflecting the light beam according to a polarization direction of the beam; and each of the lights after passing through the first beam separating unit A second beam separating means for transmitting or reflecting the beam according to its wavelength ; and disposed between the first beam separating means and the second beam separating means for rotating the polarization direction of the light beam by π / 4. A quarter wave plate ,
One image carrier is scanned with the light beam that has passed through the second beam separating means, and the light beam reflected by the second beam separating means is reflected on the first beam separating means to cause another one to be scanned. The optical writing apparatus according to claim 1, wherein the image carrier is scanned. 3. The optical writing device according to claim 2 , wherein the fixing member is provided so as to be able to hold the first beam separation unit or the second beam separation unit. An image forming apparatus comprising the optical writing device according to any one of claims 1-3. 5. The image forming apparatus according to claim 4 , wherein the image forming apparatus is a tandem type full-color apparatus including four image carriers as scanning objects to be scanned by the optical writing apparatus.

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