JP2010204610A - Optical scanning device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanning device attaining stable and high-accuracy optical scanning. <P>SOLUTION: An actuator 52 is provided near an end part on the side of -M of a toroidal lens 2107, and a fulcrum 50 for rotating the toroidal lens 2107 about an axis parallel to an R-direction is provided at the bottom surface of an optical housing 2300. The fulcrum 50 is provided at a position corresponding to the center of the toroidal lens 2107 and an end part on the side of +M of the toroidal lens 2107 with respect to the M direction. With respect to the M direction, the distance between the fulcrum 50 and the center of the toroidal lens 2107 is 0.25L, where L is the length in the M direction in an optical surface at an exit side of the toroidal lens 2107. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  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 scans the photosensitive drum in the sub-scanning direction while scanning the laser beam using a deflector (for example, a polygon mirror) in the axial direction (main scanning direction) of the photosensitive drum. In general, a method of forming a latent image by rotating the image to the right is used.

  In recent years, plastics are often used as materials for optical elements in optical scanning devices. Plastic optical elements are excellent in mass productivity, but the shape is ideal because of non-uniform temperature inside the mold during molding and cooling after removal from the mold. There are many cases where it comes off.

  In particular, in a scanning optical system, an optical element (long lens) having a long shape in the main scanning direction is often used, and the optical element may be bent in the sub scanning direction.

  If there is a shape error in the optical element of the scanning optical system, a light spot formed on the surface to be scanned causes a positional deviation in the sub-scanning direction (hereinafter also referred to as “sub-scanning deviation” for convenience), and the inclination of the scanning line Or the scanning line may be bent.

  Further, an error in attaching the optical element to the optical housing also causes a sub-scanning shift.

  Further, in an image forming apparatus having a plurality of image stations in one optical housing, a temperature difference occurs between the scanning optical systems of each image station due to temperature variations in the optical housing, and the sub-scanning deviation amount for each image station. May have been different. For example, this is a cause of color misregistration in a tandem type full-color copying machine.

  Accordingly, it has been devised to rotate the long lens of the scanning optical system to correct the inclination of the scanning line and the bending of the scanning line (see, for example, Patent Document 1 and Patent Document 2).

  From a first aspect, the present invention is an optical scanning device that scans a surface to be scanned with a light beam in a main scanning direction, a light source; a deflector that deflects the light beam from the light source; A scanning optical system that includes a scanning optical element having a direction and condenses the light beam deflected by the deflector on the surface to be scanned; an optical housing that houses the deflector and the scanning optical system; Provided in the vicinity of one end of the optical element in the main scanning direction, and the scanning optical element is parallel to the optical axis direction with a fulcrum between the center of the scanning optical element in the main scanning direction and the other end. And a drive mechanism that rotates about an axis.

  According to this, it is possible to perform optical scanning stably and with high accuracy.

  According to a second aspect of the present invention, there is provided at least one image carrier; and at least one optical scanning device according to the present invention that scans the at least one image carrier with a light beam modulated according to image information. And an image forming apparatus.

  According to this, since the optical scanning device of the present invention is provided, it is possible to stably form a high-quality image as a result.

1 is a diagram for describing a schematic configuration of a color printer according to an embodiment of the present invention. FIG. It is FIG. (1) for demonstrating schematic structure of an optical scanning device. FIG. 3 is a second diagram for explaining a schematic configuration of the optical scanning device; FIG. 3 is a third diagram for explaining a schematic configuration of the optical scanning device; FIG. 4 is a diagram (part 4) for explaining a schematic configuration of the optical scanning device; It is a figure for demonstrating the two-dimensional array contained in a light source. It is FIG. (1) for demonstrating a toroidal lens. It is FIG. (2) for demonstrating a toroidal lens. It is a figure (the 1) for demonstrating the bracket for holding | maintenance. It is FIG. (2) for demonstrating a holding bracket. It is FIG. (3) for demonstrating the bracket for holding | maintenance. It is FIG. (1) for demonstrating attachment to the optical housing of an integrated module. It is FIG. (2) for demonstrating attachment to the optical housing of an integrated module. It is FIG. (3) for demonstrating attachment to the optical housing of an integrated module. FIG. 6 is a diagram (part 1) for explaining a comparative example A; FIG. 10 is a second diagram for explaining the comparative example A; FIG. 6 is a diagram (part 1) for explaining a comparative example B; FIG. 10 is a second diagram for explaining the comparative example B; 10 is a diagram for explaining a measurement result of a scanning line shape in Comparative Example A. FIG. 10 is a diagram for explaining a measurement result of a scanning line shape in Comparative Example B. FIG. It is a figure for demonstrating the measurement result of the scanning line shape in this embodiment. It is a figure for demonstrating the variation | change_quantity of the beam spot diameter regarding the main scanning direction in the comparative example A, the comparative example B, and this embodiment. It is a figure for demonstrating the modification 1 of this embodiment. It is a figure for demonstrating the modification 2 of this embodiment. It is a figure for demonstrating the measurement result of the scanning line shape in the modification 1. FIG. It is a figure for demonstrating the measurement result of the scanning line shape in the modification 2. FIG. It is a figure for comparing the measurement result of a scanning line shape. It is a figure for comparing the variation | change_quantity of the beam spot diameter regarding a main scanning direction. It is a figure for demonstrating the modification 3 of this embodiment.

  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 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), 4 cleaning units (2031a, 2031b, 2031c, 2031d), 4 charging chargers (2032a, 2032b, 2032c, 2032d), 4 developing rollers (2033a, 2033b, 2033c, 2033d), 4 Toner cartridges (2034a, 2034b, 2034c, 2034d), transfer belt 2040, fixing roller 2050, paper feed roller 2054, registration roller pair 2056, paper discharge roller 2058, paper feed tray 2060, paper discharge Ray 2070, and includes a communication controller 2080, and a printer controller 2090 for totally controlling the above elements.

  In this specification, 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.

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

  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).

  The photosensitive drum 2030a, the charging charger 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 charger 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 charger 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 charger 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 charging charger 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 (hereinafter referred to as “toner image” for convenience) 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 sends the recording paper toward the transfer belt 2040 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 charger again.

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

  2 to 5 as an example, the optical scanning device 2010 includes two light sources (2200a, 2200b), two coupling lenses (2201a, 2201b), two aperture plates (2202a, 2202b), 2 Two beam splitting prisms (2203a, 2203b), four cylindrical lenses (2204a, 2204b, 2204c, 2204d), polygon mirror 2104, four fθ lenses (2105a, 2105b, 2105c, 2105d), and eight folding mirrors (2106a, 2106b) 2106c, 2106d, 2108a, 2108b, 2108c, 2108d), 4 toroidal lenses (2107a, 2107b, 2107c, 2107d), 4 light detection sensors (2205a, 2205b, 2205c, 220). d), 4 single light detection mirror (2207a, includes 2207b, 2207c, 2207d), and the like scanning control device (not shown). These are assembled at predetermined positions of the optical housing 2300 (not shown in FIGS. 2 to 4, see FIG. 5).

  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”.

  For convenience, the direction along the optical axis of the coupling lens 2201a is referred to as “w1 direction”, and the main scanning corresponding direction in the light source 2200a is referred to as “m1 direction”. Further, the direction along the optical axis of the coupling lens 2201b is referred to as “w2 direction”, and the main scanning corresponding direction in the light source 2200b is referred to as “m2 direction”. Note that the sub-scanning corresponding directions in the light source 2200a and the light source 2200b are both the same as the Z-axis direction.

  The light source 2200a and the light source 2200b are arranged at positions separated from each other in the X-axis direction.

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

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

  The aperture plate 2202a has an aperture and shapes the light beam that has passed through the coupling lens 2201a.

  The aperture plate 2202b has an aperture and shapes the light beam that has passed through the coupling lens 2201b.

  Each light beam splitting prism has a half mirror surface that transmits half of the incident light beam and reflects the remaining light beam, and a mirror surface that is arranged in parallel with the half mirror surface on the optical path of the light beam reflected by the half mirror surface. is doing. That is, each light beam splitting prism splits an incident light beam into two parallel light beams. Here, the light beam from the light source unit 2200a enters the light beam splitting prism 2203a, and the light beam from the light source unit 2200b enters the light beam splitting prism 2203b.

  The cylindrical lens 2204 a is arranged on the optical path of the −Z side light beam out of the two light beams from the light beam splitting prism 2203 a, and forms an image in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction.

  The cylindrical lens 2204b is disposed on the optical path of the + Z side light beam out of the two light beams from the light beam splitting prism 2203a, and forms an image in the vicinity of the deflecting reflection surface of the polygon mirror 2104 in the Z-axis direction.

  The cylindrical lens 2204c is arranged on the optical path of the + Z side light beam out of the two light beams from the light beam splitting prism 2203b, and forms an image in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction.

  The cylindrical lens 2204d is disposed on the optical path of the −Z side light beam out of the two light beams from the light beam splitting prism 2203b, and forms an image in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction.

  The polygon mirror 2104 has a four-stage mirror having a two-stage structure that rotates about an axis parallel to the Z axis, and each mirror serves as a deflecting reflection surface. The light beam from the cylindrical lens 2204a and the light beam from the cylindrical lens 2204d are deflected by the first-stage (lower) tetrahedral mirror, respectively, and the light beam from the cylindrical lens 2204b and the cylindrical light are deflected by the second-stage (upper) tetrahedral mirror. It arrange | positions so that the light beam from the lens 2204c may be deflected, respectively. Note that the first-stage tetrahedral mirror and the second-stage tetrahedral mirror rotate with a phase shift of 45 °, and writing scanning is alternately performed in the first and second stages.

  Here, the light beams from the cylindrical lens 2204 a and the cylindrical lens 2204 b are deflected to the −X side of the polygon mirror 2104, and the light beams from the cylindrical lens 2204 c and the cylindrical lens 2204 d are deflected to the + X side of the polygon mirror 2104.

  Each fθ lens has a non-arc surface shape having such a power that the light spot moves at a constant speed in the main scanning direction on the surface of the corresponding photosensitive drum as the polygon mirror 2104 rotates.

  The fθ lens 2105a and the fθ lens 2105b are disposed on the −X side of the polygon mirror 2104, and the fθ lens 2105c and the fθ lens 2105d are disposed on the + X side of the polygon mirror 2104.

  The fθ lens 2105a and the fθ lens 2105b are stacked in the Z-axis direction, the fθ lens 2105a is opposed to the first-stage tetrahedral mirror, and the fθ lens 2105b is opposed to the second-stage tetrahedral mirror. Further, the fθ lens 2105c and the fθ lens 2105d are stacked in the Z-axis direction, the fθ lens 2105c is opposed to the second-stage tetrahedral mirror, and the fθ lens 2105d is opposed to the first-stage tetrahedral mirror.

  Therefore, the light beam from the cylindrical lens 2204a deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030a through the fθ lens 2105a, the folding mirror 2106a, the toroidal lens 2107a, and the folding mirror 2108a, thereby forming a light spot. The 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.

  The light beam from the cylindrical lens 2204b deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030b through the fθ lens 2105b, the folding mirror 2106b, the toroidal lens 2107b, and the folding mirror 2108b, and a light spot is formed. The 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.

  The light beam from the cylindrical lens 2204c deflected by the polygon mirror 2104 is irradiated to the photosensitive drum 2030c through the fθ lens 2105c, the folding mirror 2106c, the toroidal lens 2107c, and the folding mirror 2108c, and a light spot is formed. The 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.

  The light beam from the cylindrical lens 2204d deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030d through the fθ lens 2105d, the folding mirror 2106d, the toroidal lens 2107d, and the folding mirror 2108d, and a light spot is formed. The 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.

  Each folding mirror is arranged so that the optical path lengths from the polygon mirror 2104 to each photosensitive drum coincide with each other, and the incident position and the incident angle of the light flux on each photosensitive drum are equal to each other. ing. Each folding mirror is held by a mirror holding member (not shown) and fixed to the optical housing 2300.

  Further, the cylindrical lens and the corresponding toroidal lens constitute a surface tilt correction optical system in which the deflection point and the corresponding photosensitive drum surface are conjugated in the sub-scanning direction.

  An optical system disposed on the optical path between the polygon mirror 2104 and each photosensitive drum is also called a scanning optical system. In this embodiment, a scanning optical system of the K station is configured by the fθ lens 2105a, the toroidal lens 2107a, and the folding mirrors (2106a and 2108a). Further, the scanning optical system of the C station is composed of the fθ lens 2105b, the toroidal lens 2107b, and the folding mirrors (2106b, 2108b). The f-theta lens 2105c, the toroidal lens 2107c, and the folding mirrors (2106c, 2108c) constitute the M station scanning optical system. Further, a scanning optical system of the Y station is configured by the fθ lens 2105d, the toroidal lens 2107d, and the folding mirrors (2106d and 2108d).

  A part of the light beam before the start of writing out of the light beam deflected by the polygon mirror 2104 and passed through the scanning optical system of the K station enters the light detection sensor 2205a via the light detection mirror 2207a.

  The light detection sensor 2205b is deflected by the polygon mirror 2104, and a part of the light beam before starting writing out of the light beam via the scanning optical system of the C station enters through the light detection mirror 2207b.

  The light detection sensor 2205c is deflected by the polygon mirror 2104, and a part of the light beam before starting writing out of the light beam via the scanning optical system of the M station enters through the light detection mirror 2207c.

  A part of the light beam before the start of writing out of the light beam deflected by the polygon mirror 2104 and passed through the scanning optical system of the Y station enters the light detection sensor 2205d via the light detection mirror 2207d.

  Each of the light detection sensors outputs a signal (photoelectric conversion signal) corresponding to the amount of received light.

  The scanning control device detects the scanning start timing on the corresponding photosensitive drum based on the output signal of each light detection sensor.

  As shown in FIG. 6 as an example, each light source has a two-dimensional array 100 in which 40 light emitting units (v1 to v40) arranged two-dimensionally are formed on one substrate. The 40 light emitting units are arranged at regular intervals when all the light emitting units are orthogonally projected onto a virtual line extending in the sub-scanning corresponding direction. In this specification, the “light emitting portion interval” refers to the distance between the centers of two light emitting portions.

  Each light emitting unit is a vertical cavity surface emitting laser (VCSEL) having an oscillation wavelength of 780 nm band. That is, the two-dimensional array 100 is a so-called surface emitting laser array.

  Here, the toroidal lens will be described with reference to FIGS. Since each toroidal lens has the same shape, when it is not necessary to distinguish each toroidal lens, they are collectively referred to as a toroidal lens 2107. For convenience, the incident direction of the light beam in each toroidal lens is referred to as “R direction”, the main scanning corresponding direction is referred to as “M direction”, and the direction orthogonal to both the R direction and the M direction is referred to as “S direction”.

  The toroidal lens 2107 has a rib portion 62 so as to surround the optical surface (incident surface and outgoing surface) from above and below (direction corresponding to the sub-scanning). A concave portion 37a is formed in the central portion on the emission surface side (+ R side) of the rib portion 62 (+ S side).

  Abutting portions (56-1, 56-2) serving as attachment references are provided on the surfaces on the −R side of both end portions in the M direction of the toroidal lens 2107, respectively.

  As an example, the toroidal lens 2107 is held by a holding bracket 35 as shown in FIGS. Here, the toroidal lens 2107 is held on the −S side of the holding bracket 35.

  The holding bracket 35 is manufactured, for example, by pressing a steel plate or the like. Support portions 38 for supporting the toroidal lens 2107 are provided in the vicinity of both ends in the longitudinal direction (M direction) of the bottom plate 35 a of the holding bracket 35.

  The leaf springs 34 are fastened and fixed by fastening screws 40 at positions on the −S side of the support portions 38 in the bottom plate 35a. Each leaf spring 34 applies an elastic force in the + S direction to the rib portion 62 on the −S side of the toroidal lens 2107. As a result, the relative positional relationship between the holding bracket 35 and the toroidal lens 2107 in the S direction is regulated (determined).

  The support portion 38 is a protruding portion that is formed by bead processing, has a U-shaped groove extending in the R direction, and protrudes toward the −S side. Therefore, the contact between the support portion 38 and the toroidal lens 2107 is a line contact extending substantially in the R direction, and the toroidal lens 2107 can be bent in the S direction without being restrained by the support portion 38.

  The + R side end 47 and the −R side end 48 of the bottom plate 35a are bent to the −S side. The bending portions 47 and 48 improve the bending rigidity in the S direction of the holding bracket 35. In order to secure the bending rigidity of the holding bracket 35, it is important to provide such a bent portion and increase the sectional moment of inertia.

  At the center tip of the + R side bent portion 47 in the M direction, a cut bent portion 36 that is further bent to the −R side is formed. The cut and bent portion 36 is engaged with a concave portion 37 a provided in the central portion of the toroidal lens 2107. With respect to the M direction, a difference of several μm to several tens of μm is provided between the width of the concave portion 37a and the width of the cut and bent portion 36, and positioning in the M direction is performed with this clearance.

  In the bent portion 48 on the −R side, two contact portions 41 are formed by half punching. Each contact portion 41 is in contact with the -R side surface of the toroidal lens 2107, and positioning in the R direction is performed.

  An adjustment mechanism 39 including an adjustment screw 31 and two leaf springs (32, 33) is attached to the center of the bottom plate 35a. The direction in which the pressing by the leaf spring 32 and the leaf spring 33 acts is opposite to the pushing / pulling direction of the adjusting screw 31. By adjusting the pushing amount / pulling amount of the adjusting screw 31, the bending shape of the toroidal lens 2107 can be adjusted. As a result, it is possible to correct scanning line bending on the surface to be scanned.

  Next, a method of attaching the holding bracket 35 holding the toroidal lens 2107 (hereinafter also referred to as “integrated module” for convenience) to the optical housing 2300 will be described with reference to FIGS.

  The −M side contact portion 56-1 is pressed and held by the leaf spring 53-1 to the contacted portion 51-1 protruding from the position near the −M side side wall on the bottom surface of the optical housing 2300. .

  The + M side contact portion 56-2 is pressed and held by a leaf spring 53-2 on a contacted portion 51-2 protruding from a position near the side wall on the + M side on the bottom surface of the optical housing 2300.

  Thereby, positioning in the R direction is performed. In the following, the pressing force by the leaf spring 53-1 is F1, and the pressing force by the leaf spring 53-2 is F2.

  An actuator 52 including a stepping motor and a gear train is attached to the side wall on the −M side of the optical housing 2300. In the actuator 52, a gear arranged coaxially with the rotation axis of the stepping motor can move in the direction of the rotation axis (see Japanese Patent Application Laid-Open Nos. 2005-88445 and 2005-189791).

  Step bent portions (58-1, 58-2) are formed at both ends in the M direction of the holding bracket 35, respectively. The step bent portion 58-1 on the −M side protrudes to the outside of the side wall via the square hole 55 on the side wall on the −M side, and is in contact with the actuator 52. The integrated module can be rotated about an axis parallel to the R direction by driving the stepping motor and moving the stepped bending portion 58-1 up and down in the S direction. Turning the integrated module about an axis parallel to the R direction in this way is called “γ rotation”. Thus, by rotating the integrated module by γ, the inclination of the scanning line on the surface to be scanned can be corrected.

  The step bending portion 58-1 on the −M side is provided with a through hole 59-1, and a fixing member 57-1 composed of a stepped screw, a coil spring, and the like is interposed through the through hole 59-1. The optical housing 2300 is screwed onto the bottom surface. Thereby, the pressing force G1 by a coil spring acts on the step bending part 58-1.

  On the bottom surface of the optical housing 2300, a fulcrum 50 for rotating the toroidal lens 2107 around an axis parallel to the R direction is provided. The fulcrum 50 is provided at a position corresponding to between the center of the toroidal lens 2107 and the + M side end of the toroidal lens 2107 in the M direction. Here, with respect to the M direction, the distance between the fulcrum 50 and the center of the toroidal lens 2107 is 0.25 L when the length in the M direction on the optical surface on the exit side of the toroidal lens 2107 is L. . The fulcrum 50 is in contact with the back surface (the surface on the −S side) of the toroidal lens 2107 so as to be rotatable about an axis substantially parallel to the R direction. Thereby, positioning in the S direction is performed. Further, the concave portion 37b provided on the rib portion 62 (-S side) of the toroidal lens 2107 is engaged with the cylindrical portion 50a protruding from the bottom surface of the optical housing 2300, thereby positioning in the M direction. .

  A through hole 59-2 is provided in the step bent portion 58-2 on the + M side. A fixing member 57-2 similar to the fixing member 57-1 is screwed into the bottom surface of the optical housing 2300 through the through hole 59-2. Thereby, the pressing force G2 by a coil spring acts on the step bending part 58-2.

  The integrated module is stably fixed to the optical housing 2300 by the pressing force G1 and the pressing force G2.

  This prevents the position and orientation of the integrated module from changing when the color printer 2000 is transported to the user, and prevents the integrated module from vibrating due to the influence of the polygon mirror 2104 and the like when used at the user. be able to.

  15 and 16 show a case where a fulcrum 50 is provided at the same position as the center of the optical surface on the exit side of the toroidal lens 2107 in the M direction as Comparative Example A.

  17 and 18, as Comparative Example B, shows a case where the fulcrum 50 is provided at the same position as the center of the + M-side step bent portion 58-2 in the M direction.

  Here, for Comparative Example A, Comparative Example B, and this embodiment, the positions of the light spots at each image height on the surface to be scanned were measured at 25 ° C. (reference temperature) and 50 ° C.

  FIG. 19 shows the light spot position at 50 ° C. relative to the light spot position at 25 ° C. (that is, the amount of change in the light spot position when the temperature is changed from 25 ° C. to 50 ° C.) for Comparative Example A. Has been. In this case, the scanning line inclination of about 120 μm upward is generated, which is an undesirable result. Here, “scanning line inclination” refers to the difference between the scanning position when the image height is −150 [mm] and the scanning position when the image height is +150 [mm].

  FIG. 20 shows the light spot position at 50 ° C. with respect to the light spot position at 25 ° C. for Comparative Example B. In this case, the scanning line was bent in a downwardly convex shape with a PV value of about 40 μm, but the scanning position deviation was small near an image height of ± 150 [mm]. That is, the scan line tilt does not occur, and this is a desirable result. Here, “scanning line bending” refers to the scanning line shape when the scanning position at an image height of ± 150 [mm] is zero.

  FIG. 21 shows the light spot position at 50 ° C. with respect to the light spot position at 25 ° C. for this embodiment. In this case, a scanning line inclination that tends to rise to the right was generated, but the amount generated was about 50 μm. This is about 40% of Comparative Example A.

  Next, for Comparative Example A, Comparative Example B, and the present embodiment, when the toroidal lens 2107 is rotated by γ in order to correct the scan line inclination of about 0.8 [mm] on the surface to be scanned, The amount of change in beam spot diameter in the main scanning direction on the surface to be scanned was measured. The measurement results are shown in FIG.

  In the case of Comparative Example A, the image height was −50 mm and the change amount of the beam spot diameter was the maximum (about 4 μm), but the change amount was small as a whole, which was a preferable result.

  In the case of Comparative Example B, the amount of change in the beam spot diameter increases as the image height increases toward the + side, and the maximum value reaches +10 μm, which is an undesirable result.

  In the case of the present embodiment, the amount of change in the beam spot diameter tends to increase on the + side compared to the − side, but the change amount is small as a whole, which is a preferable result.

  That is, in the case of the present embodiment, it is possible to reduce the generation amount of the scanning line tilt at the time of temperature change and to reduce the deterioration of the beam spot shape accompanying the correction of the scanning line tilt.

  As is clear from the above description, in the optical scanning device 2010 according to this embodiment, the pressing member is configured by the plate spring 53-1 and the plate spring 53-2, and the drive mechanism is configured by the actuator 52. The holding bracket 35 constitutes an element holding member, the fixing member 57-1 constitutes a first elastic member, and the fixing member 57-2 constitutes a second elastic member.

  As described above, according to the optical scanning device 2010 according to the present embodiment, the two light sources (2200a, 2200b), the polygon mirror 2104 for deflecting the light flux from each light source, and the toroidal lens 2107 having the main scanning direction as the longitudinal direction. A scanning optical system for condensing a plurality of light beams deflected by the polygon mirror 2104 on the surface of the corresponding photosensitive drum, an optical housing 2300 in which the polygon mirror 2104 and the scanning optical system are accommodated, and a toroidal lens 2107 as light. An actuator 52 that rotates about an axis parallel to the axial direction is provided.

  The actuator 52 is provided in the vicinity of the end of the toroidal lens 2107 on the −M side, and a fulcrum 50 for rotating the toroidal lens 2107 around an axis parallel to the R direction is provided on the bottom surface of the optical housing 2300. Yes. The fulcrum 50 is provided at a position corresponding to between the center of the toroidal lens 2107 and the + M side end of the toroidal lens 2107 in the M direction. With respect to the M direction, the distance between the fulcrum 50 and the center of the toroidal lens 2107 is 0.25 L when the length in the M direction on the optical surface on the exit side of the toroidal lens 2107 is L.

  In this case, it is possible to reduce the generation amount of the scanning line tilt when the temperature changes and to reduce the deterioration of the beam spot shape accompanying the correction of the scanning line tilt. As a result, stable and highly accurate optical scanning can be performed.

  Further, two leaf springs (53-1, 53-2) are applied to the vicinity of both ends in the M direction of the toroidal lens 2107 in a direction parallel to the optical axis direction and press the vicinity of both ends against the optical housing 2300. It has. In this case, it is possible to further reduce the bending of the scanning line accompanying the temperature change inside the optical housing 2300.

  In addition, the holding bracket 35 has an adjustment mechanism 39 that adjusts the shape of the toroidal lens 2107 in the sub-scanning direction by pressing the toroidal lens 2107 in directions opposite to each other in the sub-scanning direction. In this case, the scanning line bending can be corrected in the assembly process or the adjustment process.

  In addition, since the color printer 2000 according to the present embodiment includes the optical scanning device 2010, it is possible to stably form a high-quality image.

  In addition, the frequency with which the actuator 52 is actuated to reduce color misregistration can be reduced, and the frequency with which the image output operation is interrupted can be reduced when a plurality of images are output continuously.

  In addition, although the said embodiment demonstrated the case where the adjustment mechanism 39 was provided only in one center part of the baseplate 35a, it is not limited to this. For example, considering the molding error and assembly error of the toroidal lens 2107, the molding error and assembly error of the corresponding fθ lens, the shape error and assembly error of other optical components, the shape error of the optical housing, etc. It may be provided. This makes it possible to correct scanning line bending with higher accuracy.

  Moreover, although the said embodiment demonstrated the case where a scanning line curve was correct | amended by adjusting the shape of the toroidal lens 2107, it is not limited to this. For example, the bending of the scanning line may be corrected by deforming the folding mirror in a direction perpendicular to the reflecting surface. In this case, the mirror holding member that holds the folding mirror may have a mirror adjusting mechanism that adjusts the shape of the folding mirror by applying a pressure in a direction perpendicular to the reflecting surface of the folding mirror.

  In the above embodiment, with respect to the M direction, the distance between the fulcrum 50 and the center of the toroidal lens 2107 is 0.25 L when the length in the M direction on the optical surface on the exit side of the toroidal lens 2107 is L. However, the present invention is not limited to this, and the fulcrum 50 is provided at a position corresponding to the center between the toroidal lens 2107 and the + M side end of the toroidal lens 2107 with respect to the M direction. It only has to be done.

  A case where the distance between the fulcrum 50 and the center of the toroidal lens 2107 is 0.15 L is shown in FIG. A case where the distance between the fulcrum 50 and the center of the toroidal lens 2107 is 0.35 L is shown in FIG.

  FIG. 25 shows the light spot position at 50 ° C. with respect to the light spot position at 25 ° C. in Modification 1. In this case, a scanning line inclination that tends to rise to the right occurred, but the amount generated was about 70 μm. This is about 60% of Comparative Example A.

  FIG. 26 shows the light spot position at 50 ° C. with respect to the light spot position at 25 ° C. in Modification 2. In this case, the scanning line curve having a downwardly convex shape occurred, but the scanning position deviation was small when the image height was around ± 150 [mm].

  FIG. 27 collectively shows the light spot position at 50 ° C. with respect to the light spot position at 25 ° C. for Comparative Example A, Comparative Example B, Embodiment, Modification 1 and Modification 2.

  In FIG. 28, in order to correct the scanning line inclination of about 0.8 [mm] on the surface to be scanned for Comparative Example A, Comparative Example B, the above embodiment, Modification 1 and Modification 2, A change amount (measurement result) of the beam spot diameter in the main scanning direction on the surface to be scanned when the toroidal lens 2107 is rotated by γ is shown.

  When comprehensively judging from FIGS. 27 and 28, even in the case of the first modification and the second modification, the amount of occurrence of the scanning line tilt at the time of the temperature change is reduced, and the beam accompanying the correction of the scanning line tilt. Deterioration of the spot shape can be reduced. However, the above embodiment is more preferable.

  Further, in the above embodiment, as shown in FIG. 29 as an example, the position of the fixing member 57-2 is the position on the + S side of the fulcrum 50 so that the toroidal lens 2107 is pressed against the fulcrum 50 by the pressing force G2. You may change to Furthermore, the position of the fixing member 57-1 may be changed to the position on the + S side of the actuator 52 so that the stepped bending portion 58-1 is pressed against the actuator 52 by the pressing force G1. According to this, it is possible to suppress a change in the pressing force (external force) acting on the holding bracket 35 when the toroidal lens 2107 is rotated by γ for correcting the scanning line inclination. Therefore, it is possible to avoid changes in the shapes of the holding bracket 35 and the toroidal lens 2107, and it is possible to further reduce the scanning line bending at the time of correcting the scanning line inclination. Moreover, vibration resistance can be improved.

  In the above embodiment, the case of the color printer 2000 as the image forming apparatus has been described. However, the present invention is not limited to this. In short, an image forming apparatus including the optical scanning device 2010 can stably form a high-quality image as a result. For example, an image forming apparatus that directly irradiates laser light onto a medium (for example, paper) that develops color with laser light may be used.

  In the above embodiment, the case where the optical scanning device 2010 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 performing stable and highly accurate optical scanning. The image forming apparatus of the present invention is suitable for stably forming a high-quality image.

  35 ... Bracket for holding (element holding member), 39 ... Adjusting mechanism (element adjusting mechanism), 52 ... Actuator (driving mechanism), 53-1 ... Leaf spring (pressing member), 53-2 ... Plate spring (pressing member) 57-1, fixing member (first elastic member), 57-2, fixing member (second elastic member), 2000 ... color printer (image forming apparatus), 2030a to 2030d, photoconductor drum (image carrier). 2100 ... Optical scanning device, 2104 ... Polygon mirror (deflector), 2105a to 2105d ... fθ lens (part of scanning optical system), 2106a to 2106d ... Folding mirror, 2107a to 2107d ... Toroidal lens (scanning optical element) 2108a to 2108d ... folding mirrors, 2200a ... light source, 2200b ... light source, 2300 ... optical housing.

JP 2006-84978 A Japanese Patent No. 3844165

Claims (8)

An optical scanning device that scans a surface to be scanned with a light beam in a main scanning direction,
With a light source;
A deflector for deflecting a light beam from the light source;
A scanning optical system including a scanning optical element having a main scanning direction as a longitudinal direction, and condensing the light beam deflected by the deflector on the surface to be scanned;
An optical housing that houses the deflector and the scanning optical system;
The scanning optical element is provided in the vicinity of one end of the scanning optical element in the main scanning direction, and the scanning optical element is arranged in the optical axis direction with a fulcrum between the center of the scanning optical element in the main scanning direction and the other end. An optical scanning device comprising: a drive mechanism that rotates about a parallel axis;   2. The distance between the fulcrum and the center of the scanning optical element in the main scanning direction is 0.25 times the length of the optical surface on the exit side of the scanning optical element in the main scanning direction. The optical scanning device according to 1.   The apparatus further comprises a pressing member that applies pressure in the direction parallel to the optical axis direction to both ends near the main scanning direction of the scanning optical element, and presses the vicinity of both ends against the optical housing. Item 3. The optical scanning device according to Item 1 or 2. An element holding member for holding the scanning optical element;
The element holding member applies pressures opposite to each other in the sub-scanning direction perpendicular to both the main scanning direction and the optical axis direction to the scanning optical element, so that the sub-scanning direction of the scanning optical element 4. The optical scanning device according to claim 1, further comprising an element adjustment mechanism that adjusts a shape relating to the optical scanning device. The scanning optical system includes a folding mirror having a reflecting surface,
A mirror holding member for holding the folding mirror;
The said mirror holding member has a mirror adjustment mechanism in which a pressure is made to act in the direction perpendicular | vertical to the said reflective surface, and adjusts the shape of the said folding | returning mirror. Optical scanning device. An element holding member that holds the scanning optical element and that is supported by the drive mechanism in the vicinity of one end in the main scanning direction;
A first elastic member for pressing the vicinity of the one side end portion against the drive mechanism by an elastic force;
The optical scanning device according to claim 1, further comprising: a second elastic member for pressing the scanning optical element against the fulcrum by elastic force. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to any one of claims 1 to 6 that scans the at least one image carrier with a light beam modulated according to image information.   The image forming apparatus according to claim 7, wherein the image information is multicolor image information.