JP2012013731A - Optical scanner and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner which can be downsized without deteriorating scanning accuracy.SOLUTION: Polarization separation element 2110has light beam LBa permeate and reflects light beam LBb in direction -Z. Then, a turning back mirror 2106b for turning back an optical path of the light beam LBb reflected by the polarization separation element 2110in the direction +X is arranged on the -Z side of the polarization separation element 2110. A holder 10 integrally retains the polarization separation element 2110and the turning back mirror 2106b on its roof surface without running over to the polarization separation element 2110and the turning back mirror 2106b regarding the direction of Z axis. Thus, oscillation resistance in the polarization separation element 2110and the turning back mirror 2106b are improved compared to when they are respectively alone. Furthermore, a deflector side scanning lens, image surface side scanning lens and the polarization separation element 2110are shared by two image forming stations.

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 rotates the drum while scanning the laser beam using an optical deflector (for example, a polygon mirror) in the axial direction of the photosensitive drum so that the surface of the drum is rotated. A method of forming a latent 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 optical 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 light beams separated by the polarization separation means are emitted with different time-series signals in order to write image information on each scanned surface. Therefore, if the polarization separation characteristic of the polarization separation means is not sufficient, image information to be written on other scanned surfaces will be 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.

  Further, when the optical scanning device is thinned using the polarization separating means, it is necessary to thin all the optical elements including the polarization separating means. Further, it is essential to reduce the thickness of all structural parts including the optical housing. As the thickness of the optical element is reduced, the optical element becomes thin and long, so that the rigidity and the natural frequency are reduced. Therefore, the optical element vibrates due to vibrations from the outside of the optical scanning device, and there is a risk of image quality degradation such as so-called banding and vertical line fluctuation.

  Further, the shapes of the scanning lines of the light beam reflected by the polarization separation unit and the light beam transmitted through the polarization separation unit are different from each other, and there is a possibility that color deviation occurs in the output image.

  As described above, it is difficult to reduce the thickness of the conventional optical scanning device using the polarization separating unit 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.

  From a first viewpoint, the present invention is an optical scanning device that individually scans at least two scanned surfaces in the main scanning direction, and includes a plurality of first and second light beams having different polarization directions. An illumination system that emits a luminous flux; an optical deflector that deflects a plurality of luminous fluxes from the illumination system; and transmits one of the first luminous flux and the second luminous flux deflected by the optical deflector and reflects the other A scanning optical system including a polarization separation element and a folding mirror on which a light beam reflected by the polarization separation element is incident; and protruding from the polarization separation element and the folding mirror in a direction from the polarization separation element to the folding mirror And a holding member that integrally holds the polarization separation element and the folding mirror.

  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 at least two image carriers; and at least one optical scanning device according to the present invention that scans the at least two image carriers with light modulated according to image information. And an image forming apparatus.

  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. FIG. 2 is a diagram (part 1) for describing the optical scanning device in FIG. 1; It is a figure for demonstrating the optical system before a polarizer in FIG. FIG. 3 is a second diagram for explaining the optical scanning device in FIG. 1; It is a figure for demonstrating the beam separation surface in a polarization separation element. It is a figure for demonstrating the antireflection film in a polarization separation element. It is FIG. (1) for demonstrating the effect | action of a polarization splitting element. It is FIG. (2) for demonstrating the effect | action of a polarization splitting element. It is a diagram for explaining a holder 10 for holding the polarized beam splitter 2110 ₁ and the folding mirror 2106 b. FIG. 10 is a longitudinal sectional view of FIG. 9. It is a figure for demonstrating the simulation result which calculated | required the natural frequency of the folding | return mirror single-piece | unit. It is a figure for demonstrating the simulation result which calculated | required the natural frequency when a return | turnback mirror and a polarization separation element are integrally hold | maintained with the holder. Is a diagram for explaining a holder 10 for holding the mirror 2106c folded a polarization separating element 2110 _2. It is a figure for demonstrating the holder 20 holding two folding mirrors (2106a, 2108a). It is a longitudinal cross-sectional view of FIG. It is a figure for demonstrating the simulation result which calculated | required the natural frequency when two folding mirrors are integrally hold | maintained with the holder. It is a figure for demonstrating the holder 20 holding two folding mirrors (2106d, 2108d). It is a figure for demonstrating the prior art example 1 holding an optical element. It is a figure for demonstrating the prior art example 2 holding an optical element. It is a diagram for explaining a modification of the holder for holding the polarization separation element 2110 ₁ and the folding mirror 2106 b. It is a figure for demonstrating a polarization separation device.

  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. Constitute.

  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. Constitute.

  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. Constitute.

  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. Constitute.

  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 the recording paper one by one from the paper feed tray 2060 and conveys it to the registration roller pair 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 FIGS. 2 to 4 as an example, the optical scanning device 2010 includes four light sources (2200a, 2200b, 2200c, 2200d), four coupling lenses (2201a, 2201b, 2201c, 2201d), four Half-wave plates (2202a, 2202b, 2202c, 2202d), two polarization beam splitters (2205 ₁ , 2205 ₂ ), two aperture plates (2203 ₁ , 2203 ₂ ), and two cylindrical lenses (2204 ₁ , 2204 ₂₎ ), Polygon mirror 2104, two deflector side scanning lenses (2105 ₁ , 2105 ₂ ), two image plane side scanning lenses (2107 ₁ , 2107 ₂ ), two polarization separation elements (2110 ₁ , 2110 ₂ ), 10 Sheet folding mirror (2106a, 2106b, 2106c 2106 d, and has 2108a, 2108b, 2108c, 2108d, 2109a, 2109d), 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”.

  Each light source includes a semiconductor laser (LD). Here, the light source 2200b and the light source 2200c are arranged apart from each other in the X-axis direction, and both emit light beams in the −Y direction. The light source 2200a and the light source 2200d are disposed to face each other with respect to the X-axis direction. The light source 2200a emits a light beam in the + X direction, and the light source 2200d emits a light beam in the -X direction.

  In the following, for the sake of convenience, the light beam emitted from the light source 2200a is “light beam LBa”, the light beam emitted from the light source 2200b is “light beam LBb”, the light beam emitted from the light source 2200c is “light beam LBc”, and is emitted from the light source 2200d. The light beam is also referred to as “light beam LBd”.

  The coupling lens 2201a is disposed on the optical path of the light beam LBa emitted from the light source 2200a, and makes the light beam substantially parallel light.

  The coupling lens 2201b is disposed on the optical path of the light beam LBb emitted from the light source 2200b, and makes the light beam substantially parallel light.

  The coupling lens 2201c is disposed on the optical path of the light beam LBc emitted from the light source 2200c, and makes the light beam substantially parallel light.

  The coupling lens 2201d is disposed on the optical path of the light beam LBd emitted from the light source 2200d, and makes the light beam substantially parallel light.

Half-wave plate 2202a is disposed on an optical path of the light beam LBa that has passed through the coupling lens 2201a, and s-polarized light light beam LBa with respect to the plane of incidence of the polarization beam splitter 2205 _1.

Half-wave plate 2202b is disposed on an optical path of the light beam LBb through the coupling lens 2201 b, and p-polarized light the light beam LBb to the plane of incidence of the polarization beam splitter 2205 _1.

Half-wave plate 2202c is disposed on an optical path of the light beam LBc that has passed through the coupling lens 2201 c, the p-polarized light the light beam LBc to the plane of incidence of the polarization beam splitter 2205 _2.

Half-wave plate 2202d is disposed on the optical path of the light beam LBd through the coupling lens 2201 d, and s-polarized light light beam LBd with respect to the plane of incidence of the polarization beam splitter 2205 _2.

Polarization beam splitter 2205 ₁ is a + X side of the 1/2-wavelength plate 2202a, and is disposed on the -Y side of the half-wave plate 2202 b. This polarization beam splitter 2205 ₁ has a characteristic of transmitting p-polarized light and reflecting s-polarized light. Therefore, the polarization beam splitter 2205 _1, the light beam LBa passing through the 1/2-wavelength plate 2202a is reflected in the -Y direction, and transmits the light beam LBb passing through the 1/2-wavelength plate 2202 b. Accordingly, the optical path of the light beams LBa and the light beam LBb emitted from the polarization beam splitter 2205 ₁ are nearly identical.

Polarization beam splitter 2205 ₂ is a -X side of the 1/2-wavelength plate 2202 d, and is disposed on the -Y side of the half-wave plate 2202 c. The polarizing beam splitter 2205 ₂ is transmitted through the p-polarized light has a property of reflecting s-polarized light. Therefore, the polarization beam splitter 2205 ₂ a light beam LBd through the 1/2-wavelength plate 2202d reflected in the -Y direction, and transmits the light beam LBc through the 1/2-wavelength plate 2202 c. Accordingly, the optical path of the light beam LBc and the light beam LBd emitted from the polarization beam splitter 2205 ₂ are nearly identical.

Aperture plate 2203 _1, has an aperture and shapes the light beams LBa and flux LBb from the polarization beam splitter 2205 _1.

The aperture plate 2203 ₂ has an aperture for shaping the light beam LBc and flux LBd from the polarization beam splitter 2205 _2.

The cylindrical lens 2204 _1, the light beam LBa and flux LBb passing through the aperture of the aperture plate 2203 _1, it forms an image with respect to the Z-axis direction on the deflecting reflection surface near the polygon mirror 2104.

The cylindrical lens 2204 ₂ a light beam LBc and flux LBd having passed through the aperture of the aperture plate 2203 _2, it forms an image with respect to the Z-axis direction on the deflecting reflection surface near the polygon mirror 2104.

Thus, four coupling lenses (2201a, 2201b, 2201c, 2201d), four half-wave plates (2202a, 2202b, 2202c, 2202d), and two polarization beam splitters (2205 ₁ , 2205 ₂ ). The two aperture plates (2203 ₁ , 2203 ₂ ) and the two cylindrical lenses (2204 ₁ , 2204 ₂ ) constitute a pre-deflector optical system.

  The polygon mirror 2104 has a four-sided mirror as an example, and each mirror serves as a deflection reflection surface. The polygon mirror 2104 rotates at a constant speed around an axis parallel to the Z-axis direction, and deflects the light flux from each cylindrical lens.

Here, the light beam from the cylindrical lens 2204 ₁ (light beam LBa, the light beam LBb) is deflected in the -X side of the polygon mirror 2104, the light flux (light flux LBc, light beam LBd) from the cylindrical lens 2204 ₂ + X side of the polygon mirror 2104 To be biased. The light beam surface formed by the light beam deflected by the deflecting / reflecting surface of the polygon mirror 2104 with time is called a “deflecting surface” (see Japanese Patent Application Laid-Open No. 11-202252). Here, the deflection surface is parallel to the XY plane.

The deflector-side scanning lens 2105 ₁ is disposed on the −X side of the polygon mirror 2104 and on the optical path of the light beam (light beam LBa, light beam LBb) from the cylindrical lens 2204 ₁ deflected by the polygon mirror 2104.

Deflector-side scanning lens 2105 ₂ is a + X side of the polygon mirror 2104 is disposed on the optical path of the light beam from the cylindrical lens 2204 ₂ deflected by the polygon mirror 2104 (light beam LBc, light beam LBd).

Image-side scanning lens 2107 _1, a deflector-side scanning lens 2105 ₁ -X side, the deflector-side scanning lens 2105 ₁ the light beam through (light beam LBa, light beam LBb) is disposed on the optical path of the .

Image-side scanning lens 2107 ₂ is a deflector-side scanning lens 2105 ₂ + X side, the deflector-side scanning lens 2105 ₂ the light beam through (light beam LBc, light beam LBd) is disposed on the optical path of the.

Polarization separation element 2110 ₁ is an image-side scanning lens 2107 ₁ -X side, the light beam through the image surface side scanning lens 2107 ₁ (light beam LBa, light beam LBb) is disposed on the optical path of the.

Polarization separating element 2110 ₂ is an image-side scanning lens 2107 ₂ + X side, is disposed on the optical path of the light beam through the image surface side scanning lens 2107 ₂ (light beam LBc, light beam LBd).

  Each polarization separation element has a beam separation surface. The beam separation surface can be composed of a wire grid, a dielectric multilayer film, or the like, but is preferably a dielectric multilayer film because of its excellent wavefront aberration characteristics.

  The substrate that supports the beam separation surface can be made of glass or transparent resin. Each polarization separation element may have a cubic structure in which the beam separation surface is sandwiched between two triangular prisms each having a right-angled isosceles triangle, but the structure in which the beam separation surface is formed on one side of a plate-like transparent body is simpler. This is advantageous in that it can be manufactured by a typical process.

  Each polarization separation element is arranged in a state where the beam separation surface is inclined by 45 ° with respect to the deflection surface (see FIG. 5).

  As shown in FIG. 6, an antireflection film is preferably formed on the surface opposite to the beam separation surface in each polarization separation element. 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.

The polarization separation element 2110 ₁ transmits the light beam LBa (see FIG. 7) and reflects the light beam LBb in the −Z direction (see FIG. 8). The polarization separating element 2110 ₂ transmits light beam LBd, which reflects the light beam LBc in the -Z direction.

The light beam LBa transmitted through the polarization separation element 2110 ₁ is irradiated onto the surface of the photosensitive drum 2030a through three folding mirrors (2106a, 2108a, 2109a), and a light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 2030a as the polygon mirror 2104 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.

As described above, the deflector side scanning lens 2105 ₁ , the image plane side scanning lens 2107 ₁ , the polarization separation element 2110 ₁ , and the three folding mirrors (2106a, 2108a, 2109a) are the scanning optical system of the “K station”. .

The light beam LBb reflected by the polarization separation element 2110 ₁ is irradiated onto the surface of the photosensitive drum 2030b through two folding mirrors (2106b, 2108b), and a light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 2030b as the polygon mirror 2104 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 deflector side scanning lens 2105 ₁ , the image plane side scanning lens 2107 ₁ , the polarization separation element 2110 ₁ , and the two folding mirrors (2106b and 2108b) are the scanning optical system of the “C station”.

That is, the deflector side scanning lens 2105 ₁ , the image plane side scanning lens 2107 ₁ , and the polarization separation element 2110 ₁ are shared by the two image forming stations.

Light beam LBc that has been reflected by the polarization separating element 2110 ₂ via two reflecting mirrors (2106 c, 2108 c), is irradiated on the surface of the photosensitive drum 2030 c, the light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 2030c as the polygon mirror 2104 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.

As described above, the deflector side scanning lens 2105 ₂ , the image plane side scanning lens 2107 ₂ , the polarization separation element 2110 ₂ , and the two folding mirrors (2106c and 2108c) are the scanning optical system of the “M station”.

Light beam LBd transmitted through the polarization separating element 2110 _2, three reflecting mirrors (2106d, 2108d, 2109d) through, is irradiated on the surface of the photosensitive drum 2030 d, the light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 2030d as the polygon mirror 2104 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, the deflector side scanning lens 2105 ₂ , the image plane side scanning lens 2107 ₂ , the polarization separation element 2110 ₂ , and the three folding mirrors (2106d, 2108d, 2109d) are the scanning optical system of the “Y station”. .

That is, the deflector side scanning lens 2105 ₂ , the image plane side scanning lens 2107 ₂ , and the polarization separation element 2110 ₂ are shared by the two image forming stations.

Here, the folding mirror 2106b is disposed on the -Z side of the polarization separation element 2110 _1. Then, the mirror 2106b folded and the polarization beam splitter 2110 _1, as shown in FIG. 9 as an example, are integrally held by the holder 10.

Holder 10, as shown in FIG. 10 is a longitudinal sectional view of FIG. 9, the Z-axis direction, a polarization separating element 2110 ₁ without protruding to the polarization separating element 2110 ₁ and the folding mirror 2106b folding mirror 2106b and Are held together.

The holder 10 is an aluminum die-cast member having a roof surface (for example, see JP-A-6-50739) in which two surfaces having a longitudinal direction in the Y-axis direction are combined substantially vertically. The polarization separation element 2110 ₁ is held at the + Z side surface of the roof surface, the folding mirror 2106b is retained on the surface on the -Z side. Further, the holder 10, a rectangular clearance hole as the optical path of the light beam LBa passing through the polarization separating element 2110 ₁ is formed.

Polarization separation element 2110 ₁ and the folding mirror 2106b is at a plurality of locations in the longitudinal direction (Y axis direction) are bonded by being pressed by the plate spring roof surface, or an adhesive. Thus, the polarization separation element 2110 ₁ and the folding mirror 2106b is than when each is unitary, the rigidity increases, the natural frequency is shifted to the high frequency side. As a result, it is possible to suppress resonance due to external vibration. That is, the vibration resistance is improved.

  FIG. 11 shows a simulation result of obtaining the natural frequency of the folding mirror 2106b alone. Here, the dimensions of the folding mirror 2106b are 10 mm in width, 5 mm in thickness, and 220 mm in length. The primary mode at this time was 250.31 Hz. In this case, it tends to resonate with respect to vibrations of several hundred Hz from the drive system and others.

FIG. 12 shows a simulation result of obtaining the natural frequency when the folding mirror 2106 b and the polarization separation element 21110 ₁ are integrally held by the holder 10. Here, the polarization separation element 2110 ₁ dimension width 10 mm, thickness 5 mm, and a length 220 mm. Moreover, the dimension of the longitudinal direction of the holder 10 is 220 mm. The primary mode at this time was 523.595 Hz. In this case, the natural frequency is about twice that of the case of the folding mirror 2106b alone and the case of the polarization separation element 2110 ₁ alone (not shown).

Meanwhile, since the polarization separating element 2110 ₁ and the folding mirror 2106b is held in roof surface, even if the included angle is deviated from 90 ° by a manufacturing error or the like, the traveling direction of the light beam turned back by the return mirror 2106b (here Then, the + X direction) does not change. If the folding mirror is arranged independently as in the prior art, when the angle of the mirror surface changes by θ with respect to the design value, the traveling direction of the light beam reflected by the mirror surface changes by 2θ with respect to the planned direction. To do.

Furthermore, the folding mirror 2106c is arranged on the -Z side of the polarization separation element 2110 _2. The mirror 2106c folded a polarization separating element 2110 ₂ also, as shown in FIG. 13 as an example, it is integrally held by the holder 10. Thereby, the polarization separation element 2110 ₂ and folding mirror 2106c is than when each is unitary, the rigidity increases, the natural frequency increases. As a result, it is possible to suppress resonance due to external vibration. That is, the vibration resistance is improved.

  The folding mirror 2108a is disposed on the −Z side of the folding mirror 2106a. The folding mirror 2106a and the folding mirror 2108a are integrally held by the holder 20 as shown in FIG. 14 as an example.

  As shown in FIG. 15, which is a longitudinal sectional view of FIG. 14, the holder 20 integrally connects the folding mirror 2106a and the folding mirror 2108a without protruding from the folding mirror 2106a and the folding mirror 2108a in the Z-axis direction. keeping.

  The holder 20 is an aluminum die-cast member whose longitudinal direction is the Y-axis direction and whose cross-sectional shape orthogonal to the Y-axis direction is a so-called roof shape. The folding mirror 2106a is held on the + Z side roof surface, and the folding mirror 2108a is held on the −Z side roof surface.

  The folding mirror 2106a and the folding mirror 2108a are pressed against the roof surface by a leaf spring or bonded by an adhesive at a plurality of locations in the longitudinal direction (Y-axis direction). Thereby, each of the folding mirror 2106a and the folding mirror 2108a has higher rigidity than that of the single mirror, and the natural frequency is shifted to the high frequency side. As a result, it is possible to suppress resonance due to external vibration. That is, the vibration resistance is improved.

  FIG. 16 shows a simulation result in which the natural frequency when the folding mirror 2106a and the folding mirror 2108a are integrally held by the holder 20 is obtained. Here, the dimensions of each folding mirror are 10 mm in width, 5 mm in thickness, and 220 mm in length. Moreover, the dimension of the longitudinal direction of the holder 20 is 220 mm. The primary mode at this time was 786.84 Hz. In this case, the natural frequency is about three times that when each folding mirror is a single unit.

  The folding mirror 2108d is arranged on the −Z side of the folding mirror 2106d. The folding mirror 2106d and the folding mirror 2108d are also integrally held by the holder 20, as shown in FIG. 17 as an example. Thereby, each of the folding mirror 2106d and the folding mirror 2108d has higher rigidity than that of the single mirror, and the natural frequency is shifted to the high frequency side. As a result, it is possible to suppress resonance due to external vibration. That is, the vibration resistance is improved.

  By the way, conventionally, as shown in FIG. 18 as an example, a sheet metal member is placed along the upper surface or the lower surface of the optical element, or as shown in FIG. 19 as an example, a glass plate is attached to the back surface of the optical element, The rigidity was improved. However, in the method of aligning the sheet metal member, the sheet metal member has a shape protruding from the optical element, and the protruding portion hinders thinning. Further, in the method of attaching the glass plate, when the optical element is a polarization separation element, it is necessary to use an expensive glass that can transmit the light beam that has passed through the polarization separation element as it is.

As described above, according to the optical scanning device 2010 according to the present embodiment, the four light sources (2200a, 2200b, 2200c, 2200d), the pre-polarizer optical system, the polygon mirror 2104, the two deflector side scanning lenses (2105). ₁ , 2105 ₂ ), two image plane side scanning lenses (2107 ₁ , 2107 ₂ ), two polarization separation elements (2110 ₁ , 2110 ₂ ), ten folding mirrors (2106a, 2106b, 2106c, 2106d, 2108a, 2108b, 2108c, 2108d, 2109a, 2109d).

The deflector side scanning lens 2105 ₁ , the image plane side scanning lens 2107 ₁ , and the polarization separation element 2110 ₁ are shared by the K station and the C station. The deflector side scanning lens 2105 ₂ , the image plane side scanning lens 2107 ₂ , and the polarization separation element 2110 ₂ are shared by the M station and the Y station.

The polarization separation element 2110 ₁ transmits the light beam LBa and reflects the light beam LBb in the −Z direction. _On the −Z side of the polarization separation element 2110 ₁ , a folding mirror 2106 b that folds the light beam LBb reflected by the polarization separation element 2110 ₁ in the + X direction is disposed. The polarization separation element 2110 ₁ and the folding mirror 2106 b are arranged in the holder 10. It is integrally held on the roof surface. Thus, the polarization separation element 2110 ₁ and the folding mirror 2106b are vibration resistance is improved.

Polarization separating element 2110 ₂ transmits light beam LBd, which reflects the light beam LBc in the -Z direction. Then, the -Z side of the polarization separation element 2110 _2, folding mirror 2106c folding the light beam LBc that has been reflected by the polarization separating element 2110 ₂ in the -X direction is arranged, the mirror 2106c folded a polarization separating element 2110 _2, holder It is integrally held on 10 roof surfaces. Thus, the polarization separation element 2110 ₂ and folding mirror 2106c is vibration resistance is improved.

  The holder 10 integrally holds the polarization separation element and the folding mirror without protruding from the polarization separation element and the folding mirror in the Z-axis direction.

  Of the three folding mirrors that guide the light beams that have passed through the polarization separation elements to the corresponding photosensitive drums, two folding mirrors adjacent in the Z-axis direction are integrally held on the roof surface of the holder 20. Has been. Thereby, the vibration resistance of the two folding mirrors is improved.

  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 the holder 10 and the holder 20 were aluminum die-cast components, it is not limited to this. For example, the holder 10 and the holder 20 may be members formed by cutting, or may be members formed by sheet metal processing. Moreover, the material of the holder 10 and the holder 20 may be a metal other than aluminum, or may be a resin. For example, the holder 10 and the holder 20 may be resin members formed by injection molding.

  Moreover, the shape of the cross section (vertical cross section) orthogonal to the Y-axis direction of the holder 10 and the holder 20 is not limited to the said embodiment. Moreover, the dimension of the holder 10 and the holder 20 is not limited to the said embodiment. In short, the holder 10 may hold the polarization separation element and the folding mirror integrally without protruding from the polarization separation element and the folding mirror in the Z-axis direction. In addition, the holder 20 may hold the two folding mirrors integrally without protruding from the two folding mirrors in the Z-axis direction.

  Further, in the above embodiment, instead of the holder 10, as shown in FIG. 20 as an example, the Y axis direction is the longitudinal direction, and the end surface close to the folding mirror in the polarization separation element is fixed, and the folding mirror A holder 10 ′ having a surface to which an end face close to the polarization separation element is fixed may be used. In addition, the shape of the cross section (longitudinal cross section) orthogonal to the Y-axis direction of the holder 10 'is not limited to the L shape. Also in this case, the vibration resistance of the polarization separation element and the folding mirror can be improved.

  Similarly, the holder 10 ′ may be used in place of the holder 20. Also in this case, the vibration resistance of each folding mirror can be improved.

In the above embodiments, the place of the polarizing beam splitter 2110 _1, as shown in FIG. 21 as an example, may be used the polarization separation device 16 _1. The polarization splitting device 16 ₁ has a beam splitter _{16 10,} and two polarizers ₍₁₆ 11, _{16 12).}

Beam splitter _{16 10,} a image-side scanning lens 2107 ₁ -X side, is disposed on the optical path of the light beam through the image-side scanning lens 2107 ₁ (light beam LBa and the light beam LBb). The beam splitter 16 _10, while saving the polarization direction of the incident light beam, is transmitted through a portion of the incident light beam, a beam splitter for reflecting the remainder.

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,} and is disposed on the optical path of the light beam reflected by the beam splitter _{16 10.} As each polarizer, a general polarizing film obtained by uniaxially stretching a film dyed with iodine or a dichroic dye can be used.

Then, only the light beam LBa is transmitted through the polarizer _{16 11,} only the light beam LBb is transmitted through the polarizer _{16 12.}

Further, the same polarization separating device may be used in place of the polarization separating element 2110 _2.

  Moreover, 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.

DESCRIPTION OF SYMBOLS 10 ... Holder (holding member), 10 '... Holder (holding member), 20 ... Holder (mirror holding member), 16 ₁ ... Polarization separation device (polarization separation element), 2000 ... Color printer (image forming apparatus), 2010 ... Optical scanning devices, 2030a to 2030d ... photosensitive drum (image carrier), 2104 ... polygon mirror (optical deflector), 2105 ₁ , 2105 ₂ ... deflector side scanning lens (part of scanning optical system), 2107 ₁ , 2107 ₂ ... Image plane side scanning lens (part of scanning optical system) 2106a, 2106b, 2106c, 2106d, 2108a, 2108b, 2108c, 2108d, 2109a, 2109d .. Folding mirror (part of scanning optical system) 2110 ₁ , 2110 ₂ ... polarization separation element, 2200a to 2200d ... light source.

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

Claims (7)

An optical scanning device that optically scans at least two scanned surfaces individually in the main scanning direction,
An illumination system that emits a plurality of light beams including a first light beam and a second light beam having different polarization directions;
An optical deflector for deflecting a plurality of light beams from the illumination system;
A scanning optical system including a polarization separation element that transmits one of the first light beam and the second light beam deflected by the optical deflector and reflects the other, and a folding mirror on which the light beam reflected by the polarization separation element is incident; ;
And a holding member that integrally holds the polarization separation element and the folding mirror without protruding from the polarization separation element and the folding mirror with respect to a direction from the polarization separation element to the folding mirror. apparatus. The holding member has a roof surface in which two surfaces are combined substantially vertically,
The optical scanning device according to claim 1, wherein the polarization separation element is held on one surface of the roof surface, and the folding mirror is held on the other surface.   The optical scanning device according to claim 2, wherein the holding member has an opening serving as an optical path of a light beam transmitted through the polarization separation element.   2. The holding member has a surface to which an end surface near the folding mirror in the polarization separation element is fixed, and a surface to which an end surface near the polarization separation element in the folding mirror is fixed. The optical scanning device according to 1. The scanning optical system includes, apart from the folding mirror, two folding mirrors adjacent in the sub-scanning direction,
The optical scanning device according to claim 1, further comprising a mirror holding member that integrally holds the two folding mirrors. The mirror holding member has a roof surface in which two surfaces are combined substantially vertically,
6. The optical scanning device according to claim 5, wherein the two folding mirrors are individually held on each surface of the roof surface. At least two image carriers;
An image forming apparatus comprising: at least one optical scanning device according to claim 1 that scans the at least two image carriers with light modulated in accordance with image information.