JP5455155B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning device and an image forming apparatus, and more particularly to an optical scanning device that scans a surface to be scanned with light, and an image forming apparatus including the optical scanning device.

  In electrophotographic image recording, an image forming apparatus using a laser is widely used. In this case, the image forming apparatus includes an optical scanning device, and the drum is rotated while scanning the laser beam in the axial direction of the photosensitive drum using a deflector (for example, a polygon mirror), and the latent image is formed on the surface of the drum. A method for forming an image is common.

  2. Description of the Related Art In recent years, tandem image forming apparatuses having a plurality of photosensitive drums (usually four) have become widespread as image forming apparatuses have become more colorized and faster.

  In the tandem system, the image forming apparatus tends to increase in size as the number of drums increases, and downsizing is required including the optical scanning apparatus. To reduce the size of the optical scanning device, it is effective to superimpose a plurality of optical paths of scanning light from the deflector toward each drum.

  For example, Patent Document 1 discloses two laser light sources that emit laser beams that are linearly polarized in directions perpendicular to each other and that are modulated by a signal to be recorded, and two laser beams that are emitted from these laser light sources. Polarized light combining means for combining, deflecting means for deflecting the combined laser light in the main scanning direction, and polarized light separating means for separating the combined laser light deflected by the deflecting means into separate spots on the scanning recording surface; A recording device is disclosed.

  Patent Document 2 discloses a single laser light source, information control means for giving different information to two polarized lights of laser light from the light source, and the amount of polarization based on information from the information control means. Light from the polarization control means, scanning means for scanning and irradiating the polarization-controlled light onto a predetermined irradiation surface, separation means for splitting the scanned light into two lights according to the polarization state, and light from the scanning means An optical scanning device having optical rotation control means for optically controlling laser light according to an incident angle incident on the separating means is disclosed.

  Patent Document 3 discloses a light source, an optical deflector having a plurality of deflection reflection surfaces in the sub-scanning direction, and a light beam that divides a light beam from the light source into a plurality of light beams incident on each of the plurality of deflection reflection surfaces. An optical scanning device is disclosed that includes a dividing diffractive optical element and a scanning optical system that condenses a light beam deflected by an optical deflector onto a surface to be scanned.

  By the way, when the thickness of the optical scanning device is reduced by using the polarization separation means, it is necessary to improve the separation characteristics of the polarization separation means. For example, if the light beam incident on the polarization separating means is slightly elliptically polarized or the polarization direction is inclined, the light beams that should be separated from each other are mixed into the other scanning optical system.

  The separated light beams are emitted with different time-series signals in order to write image information on each scanned surface. Therefore, if the polarization separation characteristic is not sufficient, image information that should be written on another surface to be scanned is mixed. In a multicolor image forming apparatus, information that should be developed with cyan, for example, is written on the surface to be scanned for magenta, and is observed as crosstalk between colors on the image.

  In addition, the light beam reflected by the polarization separation means does not cause the bending of the scanning line due to the polarization separation means on the surface to be scanned, but the light beam transmitted through the polarization separation means has a scanning line that increases as the field angle increases. The phenomenon of turning occurs. In the tandem type image forming apparatus, there arises a disadvantage that color misregistration occurs between a station arranged inside and a station arranged outside. Furthermore, it is necessary to adjust the inclination of the scanning line at each station to prevent color misregistration.

  However, it is difficult to reduce the size of the conventional optical scanning device using the polarization separating means without reducing the scanning accuracy.

  The present invention has been made under such circumstances, and a first object of the invention is to provide an optical scanning device that can be reduced in size without degrading scanning accuracy.

  A second object of the present invention is to provide an image forming apparatus that can be reduced in size without degrading image quality.

According to a first aspect of the present invention, a light source unit that emits a plurality of light beams including a first light beam and a second light beam having different polarization directions; a deflector that deflects the plurality of light beams from the light source unit ; A polarization separation device having an optical element that transmits one of the first light flux and the second light flux deflected by the deflector and reflects the other, and each of the first light flux and the second light flux are respectively corresponding to a scanning optical system that focuses individually on the scanning surface; an axis parallel around the rotational axis of the deflector, wherein the polarization rotating mechanism of a separation device for rotating; wherein the polarization separating device A shaft portion for rotating about the axis parallel to the rotation axis on the opposite side to the side where the other of the first light flux and the second light flux is reflected by the optical element with respect to the optical element. is the optical scanning device having

  According to this, it is possible to reduce the size without reducing the scanning accuracy.

  According to a second aspect of the present invention, there is provided an image forming apparatus comprising: a plurality of image carriers; and at least one optical scanning device of the present invention that scans the plurality of image carriers with a light beam.

  According to this, it is possible to reduce the size without degrading the image quality.

1 is a diagram illustrating a schematic configuration of a color printer according to an embodiment of the present invention. It is FIG. (1) for demonstrating an optical scanning device. It is FIG. (2) for demonstrating an optical scanning device. It is a figure for demonstrating light source unit LU1. It is a figure for demonstrating the light source in light source unit LU1. It is a figure for demonstrating light source unit LU2. It is a figure for demonstrating the light source in light source unit LU2. It is a diagram for explaining a polarization separation device 16 ₁ configured. It is a diagram for explaining the structure of the beam splitter 16 _10. It is a figure for demonstrating the incident surface formed with an incident light beam and a beam separation surface. FIG. ₁₁ is a diagram for explaining the structure of a polarizer 1611. It is a diagram for explaining a polarization splitting device 16 ₁ of the structure. Diagram for explaining a polarization splitting device 16 ₁ of the rotation mechanism; FIG. FIG. 10 is a diagram ( _No. 2) for explaining a rotation mechanism of the polarization separation device 161; It is FIG. (1) for demonstrating the adjustment mechanism of the folding mirror 18a. It is FIG. (2) for demonstrating the adjustment mechanism of the folding mirror 18a.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a color printer 2000 as an image forming apparatus according to an embodiment.

  The color printer 2000 is a tandem multi-color printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow), and includes an optical scanning device 2010, four photosensitive drums (2030a, 2030b, 2030c, 2030d), four cleaning units (2031a, 2031b, 2031c, 2031d), four charging devices (2032a, 2032b, 2032c, 2032d), four developing rollers (2033a, 2033b, 2033c, 2033d), 4 Toner cartridges (2034a, 2034b, 2034c, 2034d), transfer belt 2040, transfer roller 2042, fixing roller 2050, paper feed roller 2054, registration roller pair 2056, paper discharge roller 2058, paper feed tray 060, paper ejection tray 2070, a communication control device 2080, and a like position shift detector 2245 and the printer controller 2090 for totally controlling the above elements.

  The communication control device 2080 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The photosensitive drum 2030a, the charging device 2032a, the developing roller 2033a, the toner cartridge 2034a, and the cleaning unit 2031a are used as a set, and form an image forming station (hereinafter also referred to as “K station” for convenience) that forms a black image. Configure.

  The photosensitive drum 2030b, the charging device 2032b, the developing roller 2033b, the toner cartridge 2034b, and the cleaning unit 2031b are used as a set and form an image forming station (hereinafter also referred to as “C station” for convenience) that forms a cyan image. Configure.

  The photosensitive drum 2030c, the charging device 2032c, the developing roller 2033c, the toner cartridge 2034c, and the cleaning unit 2031c are used as a set, and form an image forming station (hereinafter also referred to as “M station” for convenience) that forms a magenta image. Configure.

  The photosensitive drum 2030d, the charging device 2032d, the developing roller 2033d, the toner cartridge 2034d, and the cleaning unit 2031d are used as a set, and form an image forming station (hereinafter also referred to as “Y station” for convenience) that forms a yellow image. Configure.

  Each photosensitive drum has a photosensitive layer formed on the surface thereof. That is, the surface of each photoconductive drum is a surface to be scanned. Each photosensitive drum is rotated in the direction of the arrow in the plane of FIG. 1 by a rotation mechanism (not shown). Here, in the XYZ three-dimensional orthogonal coordinate system, the direction along the longitudinal direction of each photosensitive drum is described as the Y-axis direction, and the direction along the arrangement direction of the four photosensitive drums is described as the X-axis direction.

  Each charging device uniformly charges the surface of the corresponding photosensitive drum.

  Based on the multicolor image information (black image information, cyan image information, magenta image information, yellow image information) from the higher-level device, the optical scanning device 2010 charges the light flux modulated for each color correspondingly. Irradiate each surface of the photosensitive drum. As a result, on the surface of each photoconductive drum, the charge disappears only in the portion irradiated with light, and a latent image corresponding to the image information is formed on the surface of each photoconductive drum. The latent image formed here moves in the direction of the corresponding developing roller as the photosensitive drum rotates. The configuration of the optical scanning device 2010 will be described later.

  The toner cartridge 2034a stores black toner, and the toner is supplied to the developing roller 2033a. The toner cartridge 2034b stores cyan toner, and the toner is supplied to the developing roller 2033b. The toner cartridge 2034c stores magenta toner, and the toner is supplied to the developing roller 2033c. The toner cartridge 2034d stores yellow toner, and the toner is supplied to the developing roller 2033d.

  As each developing roller rotates, the toner from the corresponding toner cartridge is thinly and uniformly applied to the surface thereof. Then, when the toner on the surface of each developing roller comes into contact with the surface of the corresponding photosensitive drum, the toner moves only to a portion irradiated with light on the surface and adheres to the surface. In other words, each developing roller causes toner to adhere to the latent image formed on the surface of the corresponding photosensitive drum so as to be visualized. Here, the toner-attached image (toner image) moves in the direction of the transfer belt 2040 as the photosensitive drum rotates.

  The yellow, magenta, cyan, and black toner images are sequentially transferred onto the transfer belt 2040 at a predetermined timing, and are superimposed to form a color image.

  Recording paper is stored in the paper feed tray 2060. A paper feed roller 2054 is disposed in the vicinity of the paper feed tray 2060, and the paper feed roller 2054 takes out recording sheets one by one from the paper feed tray 2060 and conveys them to a pair of registration rollers 2056. The registration roller pair 2056 feeds the recording paper toward the gap between the transfer belt 2040 and the transfer roller 2042 at a predetermined timing. As a result, the color image on the transfer belt 2040 is transferred to the recording paper. The recording sheet transferred here is sent to the fixing roller 2050.

  In the fixing roller 2050, heat and pressure are applied to the recording paper, whereby the toner is fixed on the recording paper. The recording paper fixed here is sent to a paper discharge tray 2070 via a paper discharge roller 2058 and is sequentially stacked on the paper discharge tray 2070.

  Each cleaning unit removes toner (residual toner) remaining on the surface of the corresponding photosensitive drum. The surface of the photosensitive drum from which the residual toner has been removed returns to the position facing the corresponding charging device again.

  The misregistration detector 2245 is disposed on the −X side of the transfer belt 2040. This misalignment detector 2245 has three or more position detection sensors arranged at equal intervals in the Y-axis direction.

  Each position detection sensor outputs a signal including position information of a position detection toner patch created at each station and transferred onto the transfer belt 2040 to the printer controller 2090.

  The printer control device 2090 detects the inclination of the scanning line and the bending of the scanning line for each station based on the output signal of each position detection sensor (for example, Japanese Patent No. 4107578, Japanese Patent Application Laid-Open No. 2008-276010). Gazette and JP-A-2005-238484).

  Next, the configuration of the optical scanning device 2010 will be described.

As shown in FIG. 2 and FIG. 3 as an example, the optical scanning device 2010 includes two light source units (LU1, LU2), two cylindrical lenses (12 ₁ , 12 ₂ ), a polygon mirror 14, and two fθ lenses. (15 ₁ , 15 ₂ ), two polarization separation devices (16 ₁ , 16 ₂ ), two reflection mirrors (17 ₁ , 17 ₂ ), a plurality of folding mirrors (18a, 18b ₁ , 18b ₂ , 18c ₁ , 18c ₂ , 18d), four anamorphic lenses (19a, 19b, 19c, 19d), four exit windows (21a, 21b, 21c, 21d) and a scanning control device (not shown). These are attached to an optical housing (not shown). In the following, for convenience, the direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and the direction corresponding to the sub scanning direction is abbreviated as “sub scanning corresponding direction”.

  The light source unit LU1 and the light source unit LU2 are arranged at positions separated from each other in the X-axis direction. The main scanning corresponding direction in the light source unit LU1 is referred to as “m1 direction”, and the main scanning corresponding direction in the light source unit LU2 is referred to as “m2 direction”.

Further, "w1 direction" optical axis direction of the cylindrical lenses 12 _1, the optical axis direction of the cylindrical lens 12 _2, "w2 direction".

  The light source unit LU1 has two light sources (10a, 10b) and two collimating lenses (11a, 11b) as shown in FIG. 4 as an example.

  Both the light source 10a and the light source 10b are light sources having equivalent semiconductor lasers. As shown in FIG. 5 as an example, the light source 10a and the light source 10b are arranged on the circuit board so that the polarization directions of the light beams emitted from these semiconductor lasers are orthogonal to each other. That is, one of the two light sources is arranged in a posture orthogonal to the other light source.

  Here, it is assumed that polarized light whose electric field vector is directed in the Z-axis direction is emitted from the light source 10a, and polarized light orthogonal to the polarized light from the light source 10a is emitted from the light source 10b.

  Instead of providing two orthogonal light sources, the polarization direction of one light source can be switched over in time. In this case, an optical element made of liquid crystal or the like that actively generates a phase of λ / 2 may be provided on the optical path from the light source to the polygon mirror 14. Thereby, the number of light sources can be reduced, and size reduction and cost reduction can be promoted.

  Returning to FIG. 4, the collimator lens 11 a is disposed on the optical path of the light beam emitted from the light source 10 a, and makes the light beam substantially parallel light. Hereinafter, the light beam emitted from the light source 10a is also referred to as a light beam LBa. Therefore, LBa is linearly polarized light whose electric field vector is oriented in the Z-axis direction.

  The collimating lens 11b is disposed on the optical path of the light beam emitted from the light source 10b, and makes the light beam substantially parallel light. Hereinafter, the light beam emitted from the light source 10b is also referred to as a light beam LBb. Therefore, LBb is linearly polarized light having a polarization direction orthogonal to the polarization direction of LBa.

  As shown in FIG. 6 as an example, the light source unit LU2 includes two light sources (10c, 10d) and two collimating lenses (11c, 11d).

  Both the light source 10c and the light source 10d are light sources having an equivalent semiconductor laser. As shown in FIG. 7 as an example, the light source 10c and the light source 10d are arranged on the circuit board so that the polarization directions of the light beams emitted from these semiconductor lasers are orthogonal to each other. That is, one of the two light sources is arranged in a posture orthogonal to the other light source. Here, it is assumed that polarized light whose electric field vector is directed in the Z-axis direction is emitted from the light source 10d, and polarized light orthogonal to the polarized light from the light source 10d is emitted from the light source 10c.

  Returning to FIG. 6, the collimating lens 11 c is disposed on the optical path of the light beam emitted from the light source 10 c and makes the light beam substantially parallel light. Hereinafter, the light beam emitted from the light source 10c is also referred to as a light beam LBc. Therefore, LBc is linearly polarized light whose electric field vector is oriented in the Z-axis direction.

  The collimating lens 11d is disposed on the optical path of the light beam emitted from the light source 10d, and makes the light beam substantially parallel light. Hereinafter, the light beam emitted from the light source 10d is also referred to as a light beam LBd. Therefore, LBd is linearly polarized light having a polarization direction orthogonal to the polarization direction of LBc.

Returning to Figure 2, the cylindrical lens 12 _1, each of the light beams from the light source unit LU1 (LBa, LBb) and forms an image with respect to the Z-axis direction on the deflecting reflection surface near the polygon mirror 14.

The cylindrical lens 12 _2, each of the light beams from the light source unit LU2 (LBc, LBd) and forms an image with respect to the Z-axis direction on the deflecting reflection surface near the polygon mirror 14.

  The polygon mirror 14 has a four-sided mirror as an example, and each mirror serves as a deflection reflection surface. The polygon mirror 14 rotates at a constant speed around an axis parallel to the Z-axis direction, and deflects the light beam from each cylindrical lens at a constant angular velocity in a plane parallel to the XY plane.

Here, the light beam from the cylindrical lens 12 ₁ is deflected to the -X side of the polygon mirror 14, the light beam from the cylindrical lens 12 ₂ are deflected in the + X side of the polygon mirror 14. The beam bundle surface formed with time by the light beam deflected by the deflecting / reflecting surface of the polygon mirror 14 is called a “deflecting surface” (see JP-A-11-202252). Here, the deflection surface is parallel to the XY plane.

fθ lens 15 ₁ is a -X side of the polygon mirror 14 is disposed on the optical path of the light beam from the cylindrical lens 12 ₁ deflected by the polygon mirror 14.

Polarization splitting device 16 _1, as shown in FIG. 8, and a beam splitter _{16 10,} and two polarizers ₍₁₆ 11, _{16 12).}

Beam splitter _{16 10,} a fθ lens 15 ₁ on the -X side, is disposed on the optical path of the light beam through the fθ lens 15 ₁ (light beam LBa and the light beam LBb). Then, the polarizer _{16 11} is a -X side of the beam splitter _{16 10,} is disposed on the optical path of the light beam transmitted through the beam splitter _{16 10.} Polarizer _{16 12} is a -Z side of the beam splitter _{16 10,} is disposed on the optical path of the light beam reflected by the beam splitter _{16 10.}

Beam splitter 16 ₁₀ is a beam splitter for transmitting and reflecting in a saved state the polarization direction of incident. The beam separation surface can be composed of a wire grid, a dielectric multilayer film, or the like, but a dielectric multilayer film is preferable because of its excellent wavefront aberration characteristics.

The substrate that supports the beam separation surface can be made of glass or transparent resin. Beam splitter 16 _10, also good as a cubic structure sandwiching the beam splitting surface in two triangular prisms section is formed of right-angled isosceles triangle, the direction of the structure forming the beam splitting surface on one side of the plate-shaped transparent body, the simple This is advantageous in that it can be manufactured by a typical process. Beam splitter 16 ₁₀ is arranged in a state in which the beam splitting surface is inclined by 45 ° with respect to the deflection plane.

The surface of the beam splitting surface and opposite side of the beam splitter 16 _10, as shown in FIG. 9, preferably anti-reflection film is formed. By providing the antireflection film, it is possible to prevent the light transmitted through the substrate after separation from being reflected on the back surface of the substrate and generating unnecessary light.

  FIG. 10 shows the relationship between the beam separation surface, the light flux, and the incident surface.

As each polarizer, a general polarizing film obtained by uniaxially stretching a film dyed with iodine or a dichroic dye can be used. In this case, as shown in FIG. 11 as an example, the wavefront aberration characteristic is remarkably improved by adopting a configuration in which the polarizing film 16 ₁₁ a is sandwiched from both sides by transparent substrates 16 ₁₁ b and 16 ₁₁ c such as glass plates. . When a higher extinction ratio is required, a wire grid polarizer, a metal-dispersed polarizing film, or the like can be used.

Polarization splitting device 16 _1, as shown in FIG. 12 as an example, the Y-axis direction in the longitudinal direction and to the bottom plate 101A and the bottom plate interposed therebetween Y-axis direction is opposed to the two side plates (101B, 101C) and A holding member 101, a first plate member 102, a second plate member 103, two Mylar (registered trademark) (104A, 104B), two elastic members (105A, 105B), and an α adjusting screw 106. Yes.

Beam splitter _{16 10} is held by a holding member 101. The holding member 101 is set so that the polarization splitting surface of the beam splitter 16 ₁₀ is held inclined at 45 ° to the plane of the bottom plate 101A.

  At the center of the surface on the −Z side of the bottom plate 101A, a protrusion is provided that serves as an axis for rotating the bottom plate 101A around the Z axis. This protrusion is fitted into a bearing (not shown) of the optical housing. Further, the bottom plate 101A is supported by the optical housing so as to be rotatable in the XY plane.

The first plate member 102 is an L-shaped sheet metal member having a flat plate portion (referred to as a first flat plate portion) parallel to the YZ plane and a flat plate portion (referred to as a second flat plate portion) parallel to the XY plane. The first plate member 102 is attached such that the first flat plate portion covers the −X side of the holding member 101 and the second flat plate portion covers the −Z side of the holding member 101. The first plate portion has an opening for the light beam transmitted through the beam splitter 16 ₁₀ passes, the second flat plate portion has an opening through which the light beam reflected by the beam splitter 16 ₁₀ passes .

A polarizer 16 ₁₁ , Mylar (registered trademark) 104A, and an elastic member 105A are attached to the −X side of the first flat plate portion. A polarizer 16 ₁₂ , Mylar (registered trademark) 104B, and an elastic member 105B are attached to the −Z side of the second flat plate portion. Here, each Mylar (registered trademark) has a bent portion at the tip. Each Mylar (registered trademark) and each elastic member have an opening through which a light beam passes.

  Each elastic member is made of rubber or foam material.

Similar to the first plate member 102, the second plate member 103 has an L-shape having a flat plate portion (referred to as a third flat plate portion) parallel to the YZ plane and a flat plate portion (referred to as a fourth flat plate portion) parallel to the XY plane. This is a sheet metal member. The second plate member 103 has a third flat plate portion fixed to the first flat plate portion with the polarizer 16 ₁₁ , Mylar (registered trademark) 104 A, and the elastic member 105 A interposed therebetween, and the fourth flat plate portion has the polarizer 16. ₁₂ , Mylar (registered trademark) 104B and the elastic member 105B are sandwiched between and fixed to the second flat plate portion. The third plate portion has an opening for the light beam transmitted through the beam splitter 16 ₁₀ passes, the fourth flat plate portion has an opening through which the light beam reflected by the beam splitter 16 ₁₀ passes .

Specifically, Mylar (registered trademark) 104A and elastic member 105A are laminated and adhered to the third flat plate portion with a double-sided tape or the like, and Mylar (registered trademark) 104B and elastic member 105B are laminated and double-coated with a double-sided tape or the like. 4 Adhere to the flat plate. Then, the temporary stop state of the second plate member 103 with screws, and insert the polarizer _{16 11} between the first flat plate portion and the Mylar (R) 104A, the polarizer _{16 12} a second flat plate portion and Mylar (Registered trademark) 104B.

  At this time, each polarizer is guided by Mylar (registered trademark) whose tip is bent. Since Mylar (registered trademark) has a low coefficient of friction, a polarizer can be easily inserted without being caught or bent in the middle. Then, the second plate member is finally tightened. Thereby, each polarizer can be adhered to the first plate member.

  If there is no Mylar (registered trademark) and the polarizer and the elastic member are in direct contact, the elastic member has a large coefficient of friction, so that the polarizer may be caught or bent in the middle.

  Here, since each film-like polarizer is pressed with an appropriate pressure against the first plate member 102 whose plane is maintained over the entire surface in the Y-axis direction, optical errors such as warping and bending are generated. I will not let you. In addition, deformations such as warping, bending, and waves caused by environmental fluctuations can be prevented.

  The α adjusting screw 106 is attached to one of the two side plates (here, the −Y side plate 101C) against a pressing spring (not shown), and is rotated by a stepping motor (not shown). ing. Therefore, by holding and controlling the stepping motor, the holding member 101 can be rotated around the Z axis (see FIGS. 13 and 14). That is, a rotation mechanism is configured by the protrusion of the bottom plate 101A, the α adjusting screw 106, and a stepping motor (not shown). Note that the drive control of the stepping motor is performed by the printer control device 2090 or the scanning control device.

  By the way, it is important whether or not the photoconductor drum is correctly scanned in the longitudinal direction. In an optical scanning apparatus compatible with the tandem method, the occurrence of color misregistration can be suppressed by aligning the inclinations of the scanning lines between the stations.

  The inclination of the scanning line occurs due to complex factors such as the processing accuracy of the optical housing and the shape error of the optical element, excluding the photosensitive drum drive system.

  Here, the inclination of the scanning line is adjusted by rotating the polarization separation device around the Z axis. In this case, the inclination of the scanning line due to the light beam reflected by the polarization separation device changes, but the inclination of the scanning line due to the light beam transmitted through the polarization separation device does not change. This makes it possible to incline the scanning lines of the stations arranged on the inside with reference to the scanning lines of the stations arranged on the outside of the optical housing so that the scanning lines coincide with each other.

  In addition, since the center of rotation is provided at the center of the polarization separation device, the position of the scanning line is not changed even if the inclination of the scanning line is corrected. If the rotation center is provided at the end of the polarization separation device, the position of the scanning line also changes in conjunction with the α adjustment, so the vertical registration adjustment amount (writing timing adjustment) is increased. Will have to. This leads to an increase in power consumption. Also, optically, since the position (height) of the optical axis changes, it becomes a cause of deterioration of optical performance.

Incidentally, a polarization splitting device 16 ₂ is also similar to the polarization splitting device 16 ₁ configured.

In the present embodiment, the polarization separation device 16 ₁ and the polarization splitting device 16 ₂ is rotated around the Z-axis, the tilt adjustment of the scanning line is performed. More specifically, the printer control device 2090 or the scanning control device detects the inclination of the scanning line at the C station relative to the K station from the inclination of the scanning line detected by the printer control device 2090 based on the output signal of each position detection sensor. determine the amount, it controls the driving of the stepping motor corresponding to the polarization separating device 16 ₁ to inclination shift amount of the scanning line is substantially zero. Further, the printer control device 2090 or the scanning control device obtains the amount of deviation of the scanning line inclination at the M station relative to the Y station from the inclination of the scanning line detected by the printer control device 2090 based on the output signal of each position detection sensor. , inclination shift amount of the scan line controls the driving of the stepping motor corresponding to the polarization separating device 16 ₂ to be substantially 0.

  By the way, the light beam passing through the polarization separation device is refracted on the surface of the substrate of the beam splitter, and is refracted again when it is transmitted through the substrate and emitted into the air. And the amount of bending increases as the image height on the photosensitive drum increases.

  That is, in a scanning optical system using a polarization separation device, scanning with a light beam that has passed through the polarization separation device causes bending in the scanning line. This is a phenomenon peculiar to the scanning optical system using the polarization separation device, and in this embodiment, scanning line bending occurs at the K station and the Y station.

  In the present embodiment, an adjustment mechanism 150 for adjusting the bending of the scanning line is provided on the folding mirror (here, 18a and 18d) disposed on the optical path of the light beam that has passed through the polarization separation device ( 15 and 16).

  The adjustment mechanism 150 includes a holding member 151 that holds the folding mirror and an adjustment screw 152.

  The holding member 151 is a sheet metal member that is bent in a long channel in the Y-axis direction (the cross section is a U-shape), and is provided with receiving surfaces inside both ends in the Y-axis direction. Further, the holding member 151 is provided with a screw hole at the center in the Y-axis direction, and an adjustment screw 152 is screwed into the screw hole.

  Then, when the adjusting screw 152 is screwed in, the folding mirror is pressed from the back surface and curved. In this way, the bending of the scanning line is adjusted by bending the folding mirror. The adjusting screw 152 is rotated by a stepping motor (not shown). Therefore, by driving and controlling the stepping motor, the folding mirror can be bent to adjust the bending of the scanning line. Note that the drive control of the stepping motor is performed by the printer control device 2090 or the scanning control device.

  Specifically, the printer control apparatus 2090 or the scanning control apparatus obtains the amount of bending of the scanning line at the K station from the bending of the scanning line detected by the printer control apparatus 2090 based on the output signal of each position detection sensor. The stepping motor corresponding to the folding mirror 18a is driven and controlled so that the amount of bending of the scanning line becomes substantially zero. The printer control device 2090 or the scanning control device obtains the amount of bending of the scanning line at the Y station from the bending of the scanning line detected by the printer control device 2090 based on the output signal of each position detection sensor. The stepping motor corresponding to the folding mirror 18d is driven and controlled so that the amount of bending becomes substantially zero.

Returning to FIG. 3, the light beam transmitted through the polarization splitting device 16 ₁ (here, the light beam LBa) is irradiated on the surface of the photosensitive drum 2030a via the folding mirror 18a and the anamorphic lens 19a and the exit window 21a, the light spot It is formed. This light spot moves in the longitudinal direction of the photosensitive drum 2030a as the polygon mirror 14 rotates. That is, the photosensitive drum 2030a is scanned. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030a, and the rotational direction of the photosensitive drum 2030a is the “sub-scanning direction” on the photosensitive drum 2030a.

Thus, the mirror 18a and the anamorphic lens 19a folded fθ lens 15 ₁ and the polarization splitting device 16 ₁ is a scanning optical system of the "K station".

On the other hand, (in this case, the light beam LBb) the light beam reflected in the -Z direction by the polarization splitting device 16 ₁ is reflected in the -X direction by the reflection mirror 17 _1, and the mirror 18b ₂ folding the folding mirror 18b ₁ anamorphic The surface of the photosensitive drum 2030b is irradiated through the lens 19b and the emission window 21b, and a light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 2030b as the polygon mirror 14 rotates. That is, the photosensitive drum 2030b is scanned. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030b, and the rotational direction of the photosensitive drum 2030b is the “sub-scanning direction” on the photosensitive drum 2030b.

Thus, the mirror 18b ₂ and the anamorphic lens 19b folding mirror 18b ₁ folded fθ lens 15 ₁ and the polarization splitting device 16 ₁ and the reflection mirror 17 ₁ is a scanning optical system of the "C station".

That, f [theta] lens 15 ₁ and the polarization separating device 16 ₁ we are shared by two image forming stations.

Returning to Figure 2, f [theta] lens 15 _2, a + X side of the polygon mirror 14 is disposed on the optical path of the light beam from the cylindrical lens 12 ₂ deflected by the polygon mirror 14.

Polarization splitting device 16 ₂ includes a beam splitter _{16 20,} two polarizers ₁₆ 21, _{16 22.}

Beam splitter _{16 20,} a fθ lens 15 ₂ + X side, is disposed on the optical path of the light beam through the fθ lens 15 ₂ (light beam LBc and the light beam LBd). The polarizer _{16 21} is a + X side of the beam splitter _{16 20,} it is disposed on the optical path of the light beam transmitted through the beam splitter _{16 20.} Polarizer _{16 22} is a -Z side of the beam splitter _{16 20,} is disposed on the optical path of the light beam reflected by the beam splitter _{16 20.}

Beam splitter _{16 20} is a view similar to element as the beam splitter _{16 10.}

The polarizer 16 ₂₁ is a polarizer similar to the polarizer 16 ₁₁ , and the polarizer 16 ₂₂ is a polarizer similar to the polarizer 16 ₁₂ .

Therefore, the light beam transmitted through the polarization splitting device 16 _2, the are mostly LBd, light flux reflected by the polarization separation device 16 _2, most of the LBc.

Figure 3 back to, light beams (in this case, the light beam LBc) reflected in the -Z direction by the polarization beam splitter 42 ₂ is reflected in the + X direction by the reflection mirror 17 _2, the mirror 18c ₂ folding the folding mirror 18c ₁ And the surface of the photosensitive drum 2030c is irradiated through the anamorphic lens 19c and the emission window 21c to form a light spot. This light spot moves in the longitudinal direction of the photosensitive drum 2030c as the polygon mirror 14 rotates. That is, the photosensitive drum 2030c is scanned. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030c, and the rotational direction of the photosensitive drum 2030c is the “sub-scanning direction” on the photosensitive drum 2030c.

Thus, the mirror 18c ₂ and the anamorphic lens 19c folding mirror 18c ₁ folded and fθ lens 15 ₂ and the polarization separating device 16 ₂ and the reflecting mirror 17 ₂ is a scanning optical system of the "M station".

On the other hand, (in this case, the light beam LBd) light beam transmitted through the polarization beam splitter 42 ₂ is irradiated on the surface of the photosensitive drum 2030d via a folding mirror 18d and the anamorphic lens 19d and the exit window 21d, the light spot is formed . This light spot moves in the longitudinal direction of the photosensitive drum 2030d as the polygon mirror 14 rotates. That is, the photosensitive drum 2030d is scanned. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030d, and the rotational direction of the photosensitive drum 2030d is the “sub-scanning direction” on the photosensitive drum 2030d.

Thus, mirror 18d and the anamorphic lens 19d folded and fθ lens 15 ₂ and the polarization separating device 16 ₂ is a scanning optical system of the "Y station".

That, f [theta] lens 15 ₂ and the polarization separating device 16 ₂ is shared by the two image forming stations. Each folding mirror is provided so that the optical path lengths at the respective image forming stations are equal to each other.

  In this embodiment, the fθ lens is provided between the polygon mirror and the polarization separation device. Since the two optical paths almost overlap with each other in the Z-axis direction, the fθ lens can be shared.

  The scanning control device has a light source control circuit corresponding to each light source. The light source control circuit corresponding to the light source 10a and the light source 10b is mounted on the circuit board of the light source unit LU1. The light source control circuit corresponding to the light source 10c and the light source 10d is mounted on the circuit board of the light source unit LU2.

As described above, according to the optical scanning device 2010 according to the present embodiment, the light source unit LU1 that emits two light beams having different polarization directions (light beam LBa and light beam LBb) and two light beams having different polarization directions ( Including a light source unit LU2 that emits a light beam LBc and a light beam LBd), a polygon mirror 14 that deflects each light beam from each light source unit at a constant angular velocity in a deflection plane, and a polarization separation device (16 ₁ , 16 ₂ ). A scanning optical system for individually condensing each light beam deflected by the mirror 14 on the surface of the corresponding photosensitive drum.

Polarization splitting device 16 _1, the beam splitter 16 ₁₀ having a beam splitting surface where the light beam LBa and flux LBb is incident while changing the angle of incidence, respectively, are disposed on the optical path of the light beam transmitted through the beam splitter 16 _10, the light beam LBa a polarizer 16 ₁₁ for transmitting is arranged on an optical path of the light beam reflected by the beam splitter 16 _10, and a polarizer 16 ₁₂ for transmitting a light beam LBb.

Polarization splitting device 16 _2, the beam splitter 16 ₂₀ having a beam splitting surface where the light beam LBc and flux LBd is incident while changing the angle of incidence, respectively, are disposed on the optical path of the light beam transmitted through the beam splitter 16 _20, the light beam LBd a polarizer 16 ₂₁ for transmitting is arranged on an optical path of the light beam reflected by the beam splitter 16 _20, and a polarizer 16 ₂₂ that transmits a light beam LBc.

  Each polarization separation device is rotatable about an axis passing through the center thereof and parallel to the Z axis.

The printer control unit 2090 or the scan control apparatus, the inclination shift amount of the scanning line in the C station for K station rotates the polarization separation device 16 ₁ so as to be substantially 0, in the M station for Y Station inclination shift amount of the scanning line rotates the polarization separation device 16 ₂ to be substantially 0.

  The folding mirrors (18a and 18d) disposed on the optical path of the light beam that has passed through each polarization separation device are provided with an adjustment mechanism for adjusting the bending of the scanning line.

  Then, the printer control device 2090 or the scanning control device bends the folding mirror 18a so that the bending amount of the scanning line at the K station becomes substantially zero, and the bending amount of the scanning line at the Y station becomes substantially zero. Thus, the folding mirror 18d is curved.

  In this case, the size can be reduced without reducing the scanning accuracy.

  Since the color printer 2000 according to the present embodiment includes the optical scanning device 2010, it is possible to reduce the size without deteriorating the image quality.

  In addition, although the said embodiment demonstrated the case where each light source had one light emission part, it is not limited to this. For example, each light source may have a plurality of semiconductor lasers. Each light source may have a semiconductor laser array having a plurality of light emitting portions.

  In the above embodiment, the color printer 2000 having four photosensitive drums as the image forming apparatus has been described. However, the present invention is not limited to this. For example, a printer having two photosensitive drums may be used. In this case, two image forming stations are provided.

  In the above embodiment, the case where the optical scanning device is used in a printer has been described. However, the present invention is also suitable for an image forming apparatus other than a printer, for example, a copier, a facsimile, or a multifunction machine in which these are integrated.

  As described above, the optical scanning device of the present invention is suitable for downsizing without reducing the scanning accuracy. The image forming apparatus according to the present invention is suitable for downsizing without deteriorating the image quality.

10 a to 10 d ... light source, 14 ... a polygon mirror _(deflector), 15 1, 15 ₂ ... (part of the scanning optical system) f [theta] lens, ₁₆ 1, 16 2 _... polarization separating _{device, 16} 10, 16 _{20 ...} beam splitter , 16 ₁₁ , 16 ₂₁ ... Polarizer (first polarizer), 16 ₁₂ , 16 ₂₂ ... Polarizer (second polarizer), 17 ₁ , 17 ₂ ... Reflection mirror (part of scanning optical system) 18 a, 18 b ₁ , 18 b ₂ , 18 c ₁ , 18 c ₂ , 18 d... Folding mirror (part of scanning optical system), 19 a to 19 d... Anamorphic lens (part of scanning optical system), 101 A. (Part), 102 ... first plate member (plate member), 104A ... mylar (registered trademark) (film), 104B ... mylar (registered trademark) (film), 105A ... elastic member, 105B ... elastic Members 106... Α adjusting screw (part of the rotation mechanism) 150... Adjusting mechanism 2000 color printer (image forming apparatus) 2030 a to 2030 d photosensitive drum (image carrier) 2010 optical scanning device 2090: Printer control device (correction device), LU1: Light source unit, LU2: Light source unit.

JP-A-60-32019 JP-A-7-144434 JP 2007-279670 A

Claims (10)

A light source unit that emits a plurality of light beams including a first light beam and a second light beam having different polarization directions;
A deflector for deflecting a plurality of light beams from the light source unit ;
A polarization separation device having an optical element that transmits one of the first light flux and the second light flux deflected by the deflector and reflects the other, and each of the first light flux and the second light flux are respectively corresponding to A scanning optical system that individually collects light on the scanning surface;
About an axis parallel to the rotational axis of the deflector, a rotating mechanism for rotating the polarization separating device; equipped with,
The polarization separation device rotates about an axis parallel to the rotation axis on the opposite side of the optical element from the side where the other of the first light beam and the second light beam is reflected by the optical element. An optical scanning device having a shaft portion for the purpose .   The optical scanning apparatus according to claim 1, wherein the rotation mechanism rotates the polarization separation device about an axis passing through a center of the polarization separation device. The optical scanning apparatus according to claim 1, wherein the shaft portion is provided in a central portion of the polarization separation device in a main scanning direction. The optical scanning device according to any one of claims 1 to 3, further comprising a correction device that drives the rotation mechanism to correct the inclination of the scanning line. According to any one of claims 1 to 4, it characterized in that the light beam transmitted through the polarization separating device further comprises an adjusting mechanism for adjusting the bending of the scanning line at the time of scanning the corresponding surface to be scanned Optical scanning device. The scanning optical system includes a folding mirror disposed on an optical path of a light beam transmitted through the polarization separation device,
The optical scanning device according to claim 5 , wherein the adjustment mechanism includes a mechanism for bending the folding mirror. The optical element is a beam splitter having a beam separation surface on which the first light beam and the second light beam are incident while changing an incident angle,
The polarization separating device, wherein arranged on an optical path of the light flux transmitted through the bi chromatography beam splitter, a first polarizer to transmit the light beam is arranged on an optical path of the light beam reflected by the beam splitter, the light flux A second polarizer to transmit,
Wherein both the first polarizer and the second polarizer, according to claim 1-6, characterized in that it is sandwiched between the plate member and the elastic member having an opening each light flux passes The optical scanning device according to any one of claims. Between the first polarizer and the corresponding elastic member, and between the second polarizer and the corresponding elastic member, each has an opening through which a light beam passes, and a part thereof The optical scanning device according to claim 7 , further comprising a bent film member. The optical scanning device according to claim 7 , wherein the elastic member is rubber or foamed material. A plurality of image carriers;
An image forming apparatus comprising: at least one optical scanning device according to any one of claims 1 to 9 that scans the plurality of image carriers with a light beam.