JP2011039261A - Optical scanning apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanning apparatus that performs optical scanning stably with high accuracy. <P>SOLUTION: The optical scanning apparatus includes: two light source units; a polygon mirror 2104 which deflects luminous fluxes from each of the light source units; four scanning optical systems which individually focus the luminous fluxes deflected with the polygon mirror 2104 onto the surface of four photoreceptor drums (2030a to 2030d); four sensor arrays (2111a to 2111d) provided in association with the four photoreceptor drums; and a scanning control device or the like. Each sensor array has six light detection sensors disposed at positions different from each other with respect to a main scanning direction. Four light detection sensors receive part of the luminous flux via the polygon mirror 2104 and corresponding scanning optical system and output a signal including the information on sub scanning direction-displacement of the luminous flux condensed on the effective scanning region of the corresponding photoreceptor drum. <P>COPYRIGHT: (C)2011,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, image forming apparatuses such as printers and digital copying machines using laser light are widely used. This image forming apparatus includes an optical scanning device, and scans a laser beam using a deflector (for example, a polygon mirror) in the axial direction of a photosensitive drum (hereinafter also referred to as a “photosensitive drum”) while performing a photosensitive operation. A general method is to form a latent image on the surface (scanned surface) of the photosensitive drum by rotating the photosensitive drum.

  In the image forming apparatus, when the light beam (scanning light beam) from the optical scanning device is irradiated to the surface of the photosensitive drum, if the light beam is irradiated to a position shifted from a predetermined position, the quality of the formed image is deteriorated. There is a fear.

  Therefore, for example, Patent Document 1 discloses a detection unit that detects each registration shift including bending and inclination of a scanning line at three or more positions along the main scanning direction from a detection pattern recorded on a transfer body. And an image forming apparatus provided with scanning trajectory variable means for correcting the inclination of the scanning line and the bending of the scanning line.

  Japanese Patent Laid-Open No. 2004-228688 discloses a beam spot position detecting means for detecting a writing start position, a beam spot position detecting means for detecting a writing end position, and an optical element corrected in the sub-scanning direction of the beam to bend the scanning line by the beam. There is disclosed an optical scanning device having a scanning line bending correction unit that corrects a scanning line, and a scanning line inclination correction unit that corrects the inclination of the scanning line by tilting the entire optical element, and an image forming apparatus including the optical scanning device. . The image forming apparatus includes a photo sensor that reads a test pattern formed in a non-sheet passing area of the transfer belt as an inclination detecting unit.

  Patent Document 3 discloses an optical scanning device provided with an optical element sub-scanning position adjustment mechanism for adjusting the position of the optical element in the sub-scanning direction, a detection sensor corresponding to the toner mark on the transfer conveyance belt, and the like. An image forming apparatus is provided.

  In Patent Document 4, an adjustment light source that is different from the light source unit that emits the light beam formed on the surface to be scanned is used, and the light beam emitted from the adjustment light source is collected through the imaging optical system. By detecting the light position and adjusting the position of at least one of the light source means or the incident optical system based on the position information based on the light collection position, the light collection position of the light beam emitted from the light source means is adjusted. An optical scanning device is disclosed.

  By the way, the optical housing of the optical scanning device may be deformed due to heat from inside and outside during operation. Due to the deformation of the optical housing, the light spot in the sub-scanning direction on the surface to be scanned during operation. There was a risk of misalignment.

  However, in the devices disclosed in Patent Documents 1 to 4, it is difficult to accurately obtain the positional deviation of the light spot in real time.

  The present invention has been made under such circumstances, and a first object of the present invention is to provide an optical scanning device capable of stably performing high-precision optical scanning.

  A second object of the present invention is to provide an image forming apparatus capable of stably forming a high quality image.

  According to a first aspect of the present invention, there is provided an optical scanning device that scans a surface to be scanned in a main scanning direction with a light beam, a light source; a deflector that deflects the light beam from the light source; and deflection by the deflector. A scanning optical system including a scanning optical element for condensing the emitted light beam on the surface to be scanned; images arranged on the surface to be scanned via the deflector and the scanning optical system, which are arranged at different positions in the main scanning direction. A plurality of light detection sensors for outputting a signal including a part of the light beam directed toward the area where information is written and including positional deviation information regarding the sub-scanning direction of the light beam condensed on the surface to be scanned. This is an optical scanning device.

  According to this, it becomes possible to perform stable and highly accurate optical scanning.

  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, as a result, a high-quality image can be stably formed.

1 is a diagram for describing a schematic configuration of a color printer according to an embodiment of the present invention. FIG. It is a figure for demonstrating the position shift detector in FIG. It is a figure for demonstrating arrangement | positioning of a position detection sensor. FIG. 6 is a diagram for explaining a toner patch. It is a figure for demonstrating the locus | trajectory of the illumination light from LED. It is a timing chart for demonstrating the output signal of a position detection sensor. FIG. 2 is a diagram (part 1) for describing the optical scanning device in FIG. 1; FIG. 3 is a second diagram for explaining the optical scanning device in FIG. 1; It is a figure for demonstrating the two-dimensional array contained in each light source unit. It is FIG. (1) for demonstrating the optical system before a deflector. It is FIG. (2) for demonstrating the optical system before a deflector. 12A and 12B are diagrams for explaining the liquid crystal deflection element. It is a figure for demonstrating the positional relationship of the main optical elements in an optical scanning device. It is a figure for demonstrating the specific example in FIG. It is a figure for demonstrating the optical surface shape of a deflector side scanning lens. It is a figure for demonstrating the optical surface shape of an image surface side scanning lens. FIGS. 17A and 17B are diagrams for explaining the shape of the image-side scanning lens. It is a figure for demonstrating the sheet-metal member holding an image surface side scanning lens. It is a figure for demonstrating the state by which the image surface side scanning lens is hold | maintained at the sheet-metal member. It is a figure for demonstrating a leaf | plate spring. It is AA sectional drawing of FIG. It is a figure for demonstrating holding | maintenance to the optical housing of the sheet-metal member with which the image surface side scanning lens was mounted | worn. It is a figure for demonstrating the stepping motor for adjusting the protrusion amount of an adjustment screw. It is a figure for demonstrating the attachment position of a beam splitter. It is a figure for demonstrating the arrangement position of each photon detection sensor in a sensor array. It is a figure for demonstrating schematic structure of a photon detection sensor. FIGS. 27A and 27B are diagrams (part 1) for explaining the operation of the light detection sensor. It is a figure for demonstrating the position shift of the incident position of the light beam for a detection. FIGS. 29A and 29B are diagrams (part 2) for explaining the operation of the light detection sensor. It is a figure for demonstrating the relationship between subscanning deviation | shift amount and (DELTA) h. It is a figure for demonstrating a deformation | transformation of the sheet-metal member with which the image side scanning lens was mounted when an optical housing deform | transformed. It is a figure for demonstrating a deformation | transformation of the image surface side scanning lens when an optical housing deform | transforms. It is a figure for demonstrating the relationship between the light spot position and image height in a photoconductor drum at various temperatures. It is a block diagram for demonstrating the structure of a scanning control apparatus. It is a figure for demonstrating the modification of an optical scanning 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 chargers (2032a, 2032b, 2032c, 2032d), four 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, the communication control unit 2080, and a like position shift detector 2245 and the printer controller 2090 for totally controlling the above elements.

  In the following description, in the XYZ three-dimensional orthogonal coordinate system, the direction along the longitudinal direction of each photosensitive drum is defined as the Y-axis direction, and the direction along the arrangement direction of the four photosensitive drums is defined 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).

  A charging charger 2032a, a developing roller 2033a, and a cleaning unit 2031a are disposed in the vicinity of the surface of the photosensitive drum 2030a along the rotation direction of the photosensitive drum 2030a.

  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.

  A charging charger 2032b, a developing roller 2033b, and a cleaning unit 2031b are arranged in the vicinity of the surface of the photosensitive drum 2030b along the rotation direction of the photosensitive drum 2030b.

  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.

  A charging charger 2032c, a developing roller 2033c, and a cleaning unit 2031c are arranged in the vicinity of the surface of the photosensitive drum 2030c along the rotation direction of the photosensitive drum 2030c.

  The photosensitive drum 2030c, the charging 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.

  Near the surface of the photosensitive drum 2030d, a charging charger 2032d, a developing roller 2033d, and a cleaning unit 2031d are arranged along the rotation direction of the photosensitive drum 2030d.

  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.

  In each photosensitive drum, an area where image information is written is called an effective scanning area or an image forming area.

  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 also referred to as “toner image”) moves in the direction of the transfer belt 2040 as the photosensitive drum rotates.

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

  Recording paper is stored in the paper feed tray 2060. A paper feed roller 2054 is disposed in the vicinity of the paper feed tray 2060, and the paper feed roller 2054 takes out recording sheets one by one from the paper feed tray 2060 and conveys them to a pair of registration rollers 2056. The registration roller pair 2056 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.

  The misregistration detector 2245 is disposed on the −X side of the transfer belt 2040.

  As shown in FIG. 2 as an example, the positional deviation detector 2245 includes three position detection sensors (2245a, 2245b, 2245c).

  Each position detection sensor is arranged in a line in the order of the position detection sensor 2245a, the position detection sensor 2245b, and the position detection sensor 2245c in the -Y direction.

  The position detection sensor 2245a includes an LED 2242a that illuminates the vicinity of the + Y side end of the transfer belt 2040 (detection position 0) and a photosensor 2241a that receives the reflected light. The position detection sensor 2245b includes an LED 2242b that illuminates a central portion (referred to as detection position 1) in the Y-axis direction of the transfer belt 2040 and a photosensor 2241b that receives the reflected light. The position detection sensor 2245c includes an LED 2242c that illuminates the vicinity of the −Y side end of the transfer belt 2040 (referred to as detection position 2) and a photosensor 2241c that receives the reflected light. Each photosensor outputs a signal (photoelectric conversion signal) corresponding to the amount of received light.

  That is, as shown in FIG. 3 as an example, the position detection sensor 2245a and the position detection sensor 2245c are arranged at positions corresponding to the vicinity of both ends in the main scanning direction in the effective scanning region of each photosensitive drum, and each photosensitive drum A position detection sensor 2245b is arranged at a position corresponding to the vicinity of the central portion in the main scanning direction in the effective scanning region. In the effective scanning area of each photosensitive drum, the position corresponding to the position detection sensor 2245a is Y1, the position corresponding to the position detection sensor 2245b is Y2, and the position corresponding to the position detection sensor 2245c is Y3.

  When the misregistration detection process using the misregistration detector 2245 is performed, toner patches TP for position detection are formed at the positions Y1, Y2, and Y3 on the transfer belt 2040, respectively.

  As an example, as shown in FIG. 4, the toner patch TP includes a first line group and a second line group that are adjacent to each other in the moving direction of the transfer belt 2040. Each of the first and second line groups is composed of four line patterns (pk, pc, pm, py). The line pattern pk is a line pattern formed at the K station, and the line pattern pc is a line pattern formed at the C station. The line pattern pm is a line pattern formed at the M station, and the line pattern py is a line pattern formed at the Y station.

  In the first line group, each line pattern is inclined 45 degrees clockwise with respect to the Y-axis direction. On the other hand, in the second line group, each line pattern is inclined 45 degrees counterclockwise with respect to the Y-axis direction.

  Here, as the transfer belt 2040 rotates, the line pattern py, line pattern pm, line pattern pc, line pattern pk, line pattern pk of the second line group, line pattern pc, line pattern pm, It arrange | positions so that it may be illuminated by LED of a position detection sensor in order of the line pattern py (refer FIG. 5).

  A signal output from the position detection sensor in the position shift detection process is shown in FIG. 6 as an example. ty is the time from when the line pattern py of the first line group is detected until the line pattern py of the second line group is detected. tm is the time from when the line pattern pm of the first line group is detected until the line pattern pm of the second line group is detected. tc is the time from when the line pattern pc of the first line group is detected until the line pattern pc of the second line group is detected. tk is the time from when the line pattern pk of the first line group is detected until the line pattern pk of the second line group is detected.

  Further, tkc is the time from when the line pattern pk of the second line group is detected until the line pattern pc of the second line group is detected. tkm is the time from when the line pattern pk of the second line group is detected until the line pattern pm of the second line group is detected. tky is the time from when the line pattern pk of the second line group is detected until the line pattern py of the second line group is detected.

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

  As shown in FIG. 7 and FIG. 8 as an example, the optical scanning device 2010 includes two light source units (2200a, 2200b), two aperture plates (2201a, 2201b), two light beam splitting prisms (2202a, 2202b), Polygon mirror 2104, four liquid crystal deflecting elements (2203a, 2203b, 2203c, 2203d), four cylindrical lenses (2204a, 2204b, 2204c, 2204d), four deflector side scanning lenses (2105a, 2105b, 2105c, 2105d), 8 folding mirrors (2106a, 2106b, 2106c, 2106d, 2108a, 2108b, 2108c, 2108d), 4 image plane side scanning lenses (2107a, 2107b, 2107c, 2107d), 4 beam splitters (2 10a, 2110b, 2110c, 2110d), 4 single sensor array (2111a, 2111b, 2111c, 2111d), and a scanning control device 3022 (FIGS. 7 and 8, not shown, and a like see FIG. 34). The optical element is accommodated in an optical housing (not shown).

  In the following, for convenience, the direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and the direction corresponding to the sub scanning direction is abbreviated as “sub scanning corresponding direction”.

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

  Hereinafter, for convenience, the direction in which the light beam emitted from the light source unit 2200a is directed to the polygon mirror 2104 is referred to as “w1 direction”, and the main scanning corresponding direction in the light source unit 2200a is referred to as “m1 direction”. Further, the direction in which the light beam emitted from the light source unit 2200b is directed to the polygon mirror 2104 is referred to as “w2 direction”, and the main scanning corresponding direction in the light source unit 2200b is referred to as “m2 direction”. Note that the sub-scanning corresponding directions in the light source unit 2200a and the light source unit 2200b are the same as the Z-axis direction.

  Each light source unit has a light source and a coupling lens.

  As shown in FIG. 9 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 so that the intervals between the light emitting units are equal 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.

  Each coupling lens is disposed on the optical path of the light beam emitted from the corresponding light source, and makes the light beam a substantially parallel light beam. The light beam that has passed through the coupling lens is the output light of each light source unit.

  The aperture plate 2201a has an aperture and shapes the light beam emitted from the light source unit 2200a. The aperture plate 2201b has an aperture and shapes the light beam emitted from the light source unit 2200b.

  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 that has passed through the opening of the aperture plate 2201a enters the light beam splitting prism 2202a (see FIG. 10), and the light beam that has passed through the opening of the aperture plate 2201b enters the light beam splitting prism 2202b (see FIG. 11). .

  Each liquid crystal deflecting element can deflect incident light with respect to the Z-axis direction in accordance with an applied voltage. Each liquid crystal deflecting element has a configuration in which liquid crystal is sealed between two transparent glass plates. As shown in FIG. 12A, for example, electrodes are formed above and below the surface of one glass plate. Yes. When a potential difference is applied between the electrodes, as shown in FIG. 12B as an example, a potential gradient occurs with respect to the Z-axis direction, and the orientation of the liquid crystal changes accordingly. As a result, the Z-axis direction A refractive index gradient occurs. Thereby, like the prism, the light emission axis can be slightly tilted with respect to the Z-axis direction. As the liquid crystal, nematic liquid crystal having dielectric anisotropy is used.

  Returning to FIG. 7, here, the liquid crystal deflecting element 2203a is arranged on the optical path of the −Z side light flux among the two light fluxes from the light splitting prism 2202a, and the liquid crystal deflecting element 2203b is 2 from the light splitting prism 2202a. Among the two light beams, they are arranged on the optical path of the light beam on the + Z side. The liquid crystal deflecting element 2203c is disposed on the optical path of the + Z side light beam out of the two light beams from the light beam splitting prism 2202b, and the liquid crystal deflecting element 2203d is the −Z side of the two light beams from the light beam splitting prism 2202b. Are arranged on the optical path of the luminous flux.

  Each cylindrical lens has a strong power in the Z-axis direction, and forms a long line image in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the main scanning corresponding direction.

  Here, the cylindrical lens 2204a is disposed on the optical path of the light beam via the liquid crystal deflection element 2203a, and the cylindrical lens 2204b is disposed on the optical path of the light beam via the liquid crystal deflection element 2203b. The cylindrical lens 2204c is disposed on the optical path of the light beam via the liquid crystal deflection element 2203c, and the cylindrical lens 2204d is disposed on the optical path of the light beam via the liquid crystal deflection element 2203d.

  The optical system arranged on the optical path between the light source unit and the polygon mirror 2104 is also called a pre-deflector optical system.

  The polygon mirror 2104 has a four-stage mirror having a two-stage structure, and each mirror serves as a deflection 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. In addition, a groove is provided between the first-stage four-sided mirror and the second-stage four-sided mirror so that the windage loss is reduced. The thickness of each quadrilateral mirror is about 2 mm.

  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.

  The deflector side scanning lens 2105a and the deflector side scanning lens 2105b are arranged on the −X side of the polygon mirror 2104, and the deflector side scanning lens 2105c and the deflector side scanning lens 2105d are arranged on the + X side of the polygon mirror 2104. ing.

  The deflector-side scanning lens 2105a and the deflector-side scanning lens 2105b are stacked in the Z-axis direction, the deflector-side scanning lens 2105a is opposed to the first-stage four-sided mirror, and the deflector-side scanning lens 2105b is two-stage. It faces the four-sided mirror of the eye. The deflector side scanning lens 2105a and the deflector side scanning lens 2105b may be integrally formed.

  The deflector-side scanning lens 2105c and the deflector-side scanning lens 2105d are stacked in the Z-axis direction, the deflector-side scanning lens 2105c is opposed to the second-stage four-sided mirror, and the deflector-side scanning lens 2105d is one stage. It faces the four-sided mirror of the eye. The deflector side scanning lens 2105c and the deflector side scanning lens 2105d may be integrally formed.

  Therefore, the light beam from the cylindrical lens 2204a deflected by the polygon mirror 2104 enters the beam splitter 2110a via the deflector side scanning lens 2105a, the folding mirror 2106a, the image plane side scanning lens 2107a, and the folding mirror 2108a (FIG. 8). The light beam that has passed through the beam splitter 2110a is irradiated onto the surface of the photosensitive drum 2030a to form a light spot. 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” of the photosensitive drum 2030a. The rotation direction of the photosensitive drum 2030a is the “sub-scanning direction” of the photosensitive drum 2030a.

  The light beam from the cylindrical lens 2204b deflected by the polygon mirror 2104 is incident on the beam splitter 2110b via the deflector side scanning lens 2105b, the folding mirror 2106b, the image plane side scanning lens 2107b, and the folding mirror 2108b (FIG. 8). The light beam that has passed through the beam splitter 2110b is irradiated onto the surface of the photosensitive drum 2030b to form a light spot. 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” of the photosensitive drum 2030b. The rotation direction of the photosensitive drum 2030b is the “sub-scanning direction” of the photosensitive drum 2030b.

  The light beam from the cylindrical lens 2204c deflected by the polygon mirror 2104 is incident on the beam splitter 2110c via the deflector side scanning lens 2105c, the folding mirror 2106c, the image plane side scanning lens 2107c, and the folding mirror 2108c (FIG. 8). The light beam that has passed through the beam splitter 2110c is irradiated onto the surface of the photosensitive drum 2030c, and a 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” of the photosensitive drum 2030c. The rotation direction of the photosensitive drum 2030c is the “sub-scanning direction” of the photosensitive drum 2030c.

  The light beam from the cylindrical lens 2204d deflected by the polygon mirror 2104 enters the beam splitter 2110d via the deflector-side scanning lens 2105d, the folding mirror 2106d, the image plane-side scanning lens 2107d, and the folding mirror 2108d (FIG. 8). The light beam that has passed through the beam splitter 2110d is irradiated onto the surface of the photosensitive drum 2030d to form a light spot. 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. The rotation direction of the photosensitive drum 2030d is the “sub-scanning direction” of 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.

  In each station, a cylindrical lens and an image plane side scanning lens constitute a surface tilt correction optical system in which a corresponding photosensitive drum surface and a deflection point on the polygon mirror 2104 are conjugated in the sub scanning direction. Yes.

  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, the K station scanning optical system is configured by the deflector side scanning lens 2105a, the image plane side scanning lens 2107a, the folding mirrors (2106a, 2108a), and the beam splitter 2110a. The scanning optical system of the C station is composed of the deflector side scanning lens 2105b, the image plane side scanning lens 2107b, the folding mirrors (2106b, 2108b), and the beam splitter 2110b. The deflector side scanning lens 2105c, the image plane side scanning lens 2107c, the folding mirrors (2106c, 2108c), and the beam splitter 2110c constitute a scanning optical system of the M station. Further, the Y-station scanning optical system is composed of the deflector side scanning lens 2105d, the image plane side scanning lens 2107d, the folding mirrors (2106d, 2108d), and the beam splitter 2110d.

  FIG. 13 shows the positional relationship between the main optical elements of the pre-deflector optical system and the scanning optical system in the K station. FIG. 14 shows an example of specific values (unit: mm) of symbols d1 to d11 in FIG. The other stations have the same positional relationship.

  Further, the direction of the light beam emitted from the cylindrical lens 2204a and the light beam reflected toward the position of the image height 0 (position p0 in FIG. 13) on the surface of the photosensitive drum 2030a by the deflection reflection surface of the polygon mirror 2104. The angle formed with the traveling direction (θr in FIG. 13) is 60 degrees.

Each deflector-side scanning lens and each image plane-side scanning lens are made of resin. Each of these surfaces (incident side surface and exit side surface) is an aspherical surface expressed by the following equation (1) and the following equation (2). Here, X represents the coordinate in the X-axis direction, and Y represents the coordinate in the Y-axis direction. The center of the incident surface is Y = 0. C _m0 indicates the curvature in the main scanning corresponding direction at Y = 0, and is the reciprocal of the curvature radius R _m . a ₀₀ , a ₀₁ , a ₀₂ ,... are aspheric coefficients in the main scanning corresponding direction. Cs (Y) is the curvature in the sub-scanning corresponding direction with respect to Y, R _s0 is the radius of curvature on the optical axis in the sub-scanning corresponding direction, b ₀₀ , b ₀₁ , b ₀₂ ,. Spherical coefficient. The optical axis is an axis that passes through the center point in the sub-scanning corresponding direction when Y = 0.

FIG. 15 shows an example of values of R _m , R _s0, and each aspheric coefficient on each surface (incident side surface (first surface), exit side surface (second surface)) of each deflector side scanning lens. Has been.

FIG. 16 shows an example of values of R _m , R _s0, and each aspheric coefficient on each surface (incident side surface (third surface), exit side surface (fourth surface)) of each image surface side scanning lens. Has been. Each image plane side scanning lens has a strong power in the sub-scanning corresponding direction.

  As an example, the shape of each image plane side scanning lens is shown in FIG. 17A and FIG. 17B, which is a cross-sectional view taken along the line AA of FIG. For convenience, the incident direction of the light beam in each image plane side scanning lens is “R direction”, the main scanning corresponding direction is “M direction”, and the direction orthogonal to both the R direction and the M direction is “S direction”. . When there is no need to distinguish between the image plane side scanning lenses, they are collectively referred to as “image plane side scanning lens 2107”.

In the image plane side scanning lens 2107, a rib portion 306a is formed on the surface on the -S side, and a rib portion 306b is formed on the surface on the + S side. The rib 306a is formed with _three protrusions (307a ₁ , 307a ₂ , 307a ₃ ) protruding in the + R direction. Protrusions 307a ₂ is located in the center with respect to the M direction, the protrusion 307a ₁ is located in the -M side of the protrusion 307a _2, protrusions 307a ₂ is located on the + M side of the protruding portion 307a _2.

Three protrusions (307b ₁ , 307b ₂ , 307b ₃ ) protruding in the + R direction are formed on the rib part 306b. Projections 307b ₂ is located in the center with respect to the M direction, the protrusion 307b ₁ is located in the -M side of the protruding portion 307b _2, projections 307b ₂ is located on the + M side of the protruding portion 307b _2.

The protruding portion 307a ₁ is located on the −S side of the raised portion 307b ₁ , the protruding portion 307a ₂ is located on the −S side of the raised portion 307b ₂ , and the protruding portion 307a ₃ is located on the −S side of the raised portion 307b _3. positioned.

  The image-side scanning lens 2107 has a stable shape so that the image-side scanning lens 2107 is not deformed even when a force is locally applied during tilt adjustment, that is, when the lens is assembled. It is hold | maintained at the sheet-metal member so that shape of this may be maintained.

  A sheet metal member 301 that holds the image plane side scanning lens 2107 is shown in FIG. 18 as an example. The sheet metal member 301 is a sheet member formed by sheet metal processing, and includes a bottom plate 301a having a direction parallel to the M direction as a longitudinal direction, and two side plates (301b, 301c) facing each other with the bottom plate 301a interposed therebetween. have.

The side plate 301b is formed with _three notches (311 ₁ , 311 ₂ , 311 ₃ ) with which the projections of the image side scanning lens 2107 are engaged.

  In the bottom plate 301a, standing bent portions 310 each having an opening 313 are formed in the vicinity of both end portions in the M direction. These standing bent portions 310 and the image plane side scanning lens 2107 come into contact with each other.

  In addition, three screw holes 312 are formed in the bottom plate 301a so as to correspond to the notches of the side plate 301b. Each screw hole 312 is formed at each position corresponding to the substantially central position of the image-side scanning lens 2107 in the R direction when the image-side scanning lens 2107 is held.

  Further, with respect to the M direction, a protrusion 318 is formed at one end of the bottom plate 301a, and a notch 321 is formed at the other end.

  The side plate 301b has two slits 314 corresponding to the openings 313 of the bottom plate 301a.

  As shown in FIG. 19 as an example, the image plane side scanning lens 2107 is held on the sheet metal member 301 by three first plate springs 302 and two second plate springs 303. In FIG. 19, illustration of each side plate is omitted for easy understanding.

  The second leaf spring 303 is a clip-like leaf spring, which applies + S-direction pressing to the −S side end face of the image plane side scanning lens 2107, and −S to the + S side face of the bottom plate 301 a of the sheet metal member 301. By applying the pressing in the direction, the image plane side scanning lens 2107 and the sheet metal member 301 are sandwiched. Note that the + S side plate portion of the second leaf spring 303 passes through the opening 313 from the outside and is inserted into the slit 304.

The first leaf spring 302 is used to sandwich the rib portion 306 a of the image plane side scanning lens 2107 and the sheet metal member 301. Here, the first plate spring 302, as shown in FIG. 20, a bottom plate portion 302 _1, + side plate portion 302 ₂ of the R side, a side plate portion 302 ₃ of the -R-side end of the side plate portion 302 ₃ It has an upper plate portion 302 ₄ for extending + R direction from the parts. Further, the side plate portion _3022, an opening is formed. Further, the bottom plate portion 302 _1, a circular opening 302 ₅ the adjustment screw 308 penetrates is formed.

Then, as shown in FIG. 21 is an A-A sectional view of FIG. 19, the protrusion of the ribs 306a to the opening of the side plate portion ₃₀₂₂ is engaged, the rib of the -R-side by the upper plate portion 302 ₄ Pressing in the + S direction is applied to the portion 306a.

Furthermore, each screw hole 312 of the sheet metal member 301, adjusting screw 308 is threaded through the opening 302 ₅ of the first plate spring 302. The tip of the adjustment screw 308 on the −S side is in contact with the + S side end surface of the image plane side scanning lens 2107. Therefore, by pressing the adjusting screw 308, it is possible to apply a pressure in the −S direction to the image plane side scanning lens 2107.

  In this case, since the pressing force by the adjusting screw 308 acting on the image surface side scanning lens 2107 and the pressing force by the first leaf spring 302 act in opposite directions, the force acting on the image surface side scanning lens 2107 is small. Adjustment is possible.

  For example, when the protruding amount of the adjusting screw 308 from the bottom plate 301a of the sheet metal member 301 is made smaller than the height of the upright bending portion 310, the image plane side scanning lens 2107 can be warped so that its generatrix is convex upward. . On the contrary, when the protruding amount of the adjusting screw 308 is made larger than the height of the upright bending portion 310, the image plane side scanning lens 2107 can be warped so that its generatrix is convex downward. Therefore, by adjusting the protruding amount of the adjusting screw 308, the focal line of the image plane side scanning lens 2107 is curved in the S direction, and the bending of the scanning line can be corrected. The direction of the adjustment axis in the adjustment of the image plane side scanning lens 2107 by each adjustment screw 308 is parallel to the optical axis direction of the image plane side scanning lens 2107. The adjustment screw 308 disposed between the center portion and the upright bending portion 310 can also correct M-type and W-type bends.

  The sheet metal member 301 on which the image plane side scanning lens 2107 is mounted is positioned by fitting a projection 318 formed on the end portion with a positioning guide (not shown) provided on the holding portion of the optical housing, and is in the −S direction. The leaf spring 326 attached to the holding portion of the optical housing is bridged so as to be biased to be held by the optical housing.

  Further, as shown in FIG. 22 as an example, the image plane side scanning lens 2107 is provided with a stepping motor 315 for rotating the image plane side scanning lens 2107 around an axis parallel to the R direction. Here, since the K station is used as a reference, a stepping motor for rotating the image plane side scanning lens 2107a may not be provided.

  The stepping motor 315 is engaged with a notch 321 formed at one end of the sheet metal member 301 and a recessed portion of the movable cylinder 316 by screwing a feed screw formed at the tip of the shaft into a screw hole of the movable cylinder 316. By the rotation of the stepping motor 315, it can be displaced in the sub-scanning corresponding direction (here, the direction parallel to the S direction).

  Further, a column 322 is provided on the −S side of the image plane side scanning lens 2107. The support column 322 is placed on a support unit 320 provided in the holding unit of the optical housing, and is pressed against the support column 322 by a leaf spring (not shown). As a result, following the forward / reverse rotation of the stepping motor 315, the image plane side scanning lens 2107 can rotate in the plane orthogonal to the optical axis with the contact point with the support 320 as a fulcrum for tilt adjustment. Along with this, the bus line of the image side scanning lens 2107 is tilted, and as a result, the scanning line is tilted. In addition, it is good also as a structure which mounts the image surface side scanning lens 2107 directly on the support part provided in the optical housing, and is hold | maintained with a leaf | plate spring etc., without providing the support | pillar 322.

  Here, as shown in FIG. 23, a stepping motor 315A for adjusting the protruding amount of each adjusting screw 308 is provided.

  By the way, the optical housing has four slits through which light beams directed to the respective photosensitive drums pass, and each beam splitter is attached to a portion including the slits (see FIG. 24). That is, each beam splitter also serves as dustproof glass. Thereby, the number of parts can be reduced and the cost can be reduced.

  The sensor array 2111a is disposed on the optical path of the light beam reflected by the beam splitter 2110a.

  The sensor array 2111b is disposed on the optical path of the light beam reflected by the beam splitter 2110b.

  The sensor array 2111c is disposed on the optical path of the light beam reflected by the beam splitter 2110c.

  The sensor array 2111d is disposed on the optical path of the light beam reflected by the beam splitter 2110d.

Here, each sensor array has six light detection sensors (18 ₁ , 18 ₂ , 18 ₃ , 18 ₄ , 18 ₅ , 18 ₆ ) arranged at equal intervals along the main scanning corresponding direction. (See FIG. 25).

Therefore, the light beam reflected by the beam splitter is incident on each light detection sensor in sequence as the polygon mirror 2104 rotates as a detection light beam. Then, the incident position of the detection light beam in each light detection sensor moves in the main scanning corresponding direction (for convenience, the m direction) as the polygon mirror 2104 rotates. Incidentally, the light detecting sensor 18 ₁ is one of the incident detection beam before the start of writing in the scanning, the optical sensor 18 _6, so that the detection light beam after completion of writing in one scan is incident It has become. Then, the optical detection sensors 18 2 _to optical detection sensor 18 _5, the detection light beam separated from the light beam toward the effective scanning area are incident.

That is, the optical sensor 18 ₁ also has a function of a conventional so-called synchronous detection center.

  Further, the normal direction of the light receiving surface of each light detection sensor is inclined with respect to the incident direction of the detection light beam (see FIG. 8). Thereby, it can avoid that the reflected light in the light-receiving surface of each light detection sensor returns to a light source, and influences light quantity control.

  As shown in FIG. 26 as an example, each light detection sensor includes a light receiving element having two light receiving parts (a first light receiving part 18a and a second light receiving part 18b), and a signal corresponding to the amount of light received from the light receiving element ( An amplifier (AMP) 18c for amplifying the photoelectric conversion signal), and a comparator (CMP) 18d for comparing the output signal level of the amplifier 18c with a preset reference level Vs and outputting the comparison result. Yes. The output signal of the comparator 18d is supplied to the scanning controller 3022.

  Each light receiving portion of the light receiving element has a different distance in the m direction depending on the position in the sub-scanning corresponding direction (for convenience, the s direction).

  The first light receiving part 18a is a rectangular light receiving part as an example, and is arranged so that the longitudinal direction thereof coincides with the s direction. That is, the two sides through which the detection light beam passes are parallel to the s direction.

  The second light receiving part 18b is a parallelogram shaped light receiving part as an example, and is arranged on the + m side of the first light receiving part 18a. The longitudinal direction of the second light receiving unit 18b is inclined by an angle θ (0 <θ <90 °) with respect to the longitudinal direction of the first light receiving unit 18a in the light receiving surface. That is, the two sides through which the detection light beam passes are inclined with respect to the s direction.

  The amplifier 18c inverts and amplifies the input signal. Accordingly, the output signal level of the amplifier 18c decreases as the amount of light received by the light receiving element increases.

  The reference level Vs is set to a level slightly higher than the output signal level (minimum value) of the amplifier 18c when the detection light beam is received by the light receiving element. Therefore, when any one of the light receiving units receives the detection light beam, the determination result in the comparator 18d changes, and the output signal of the comparator 18d changes accordingly.

  Each light detection sensor is adjusted such that when the incident position of the light beam on the surface of the corresponding photosensitive drum is a designed position, the detection light beam passes through substantially the center of each light receiving unit (see FIG. 27 (A)). At this time, the time from when the detection light beam is detected by the first light receiving unit 18a until it is detected by the second light receiving unit 18b is obtained in advance as the reference time Ts (see FIG. 27B). ). For convenience, the movement path of the incident position of the detection light beam in each light detection sensor at this time, that is, the designed movement path is referred to as “path A”.

  By the way, due to an error in the mounting position when mounting each optical element to the optical housing, deformation of the optical housing, or the like, the optical path of the light beam toward the photosensitive drum is in a sub-scanning direction (here, May shift in the Z-axis direction).

  In this case, similarly to the light beam directed to the photosensitive drum, the detection light beam is also shifted in the sub-scanning corresponding direction (here, the s direction) with respect to the designed optical path (see FIG. 28).

  As an example, as shown in FIG. 29A, the movement path of the incident position of the detection light beam in each light detection sensor is also shifted from the path A in the sub-scanning corresponding direction. For convenience, the movement route at this time is referred to as a route B.

  Then, the shift amount Δh (see FIG. 29A) of the movement path at this time can be obtained from the following equation (3). Here, ΔT is the difference between the time T from the fall to the next fall in the output signal of the comparator 18d and the reference time Ts (see FIG. 29B), and V is the movement of the detection light beam. Speed (scanning speed). The amount of deviation Δh has a correlation with the amount of deviation in the sub-scanning corresponding direction with respect to the designed optical path of the optical path of the light beam toward the photosensitive drum (hereinafter, abbreviated as “sub-scanning deviation amount” for convenience) ( (See FIG. 30). Note that the coefficient k in FIG. 30 is a value unique to the apparatus and can be obtained in advance.

  Δh = (V / tan θ) × ΔT (3)

Further, the fall timing in the output signal of the comparator 18d when the first light receiving unit 18a receives the detection light beam is not affected by the incident position of the detection light beam in the s direction. Therefore, when the first light receiving portion 18a of the optical sensor 18 ₁ has received the detection light beam, it is possible to obtain the timing of write start from the falling timing of the output signal of the comparator 18d.

  Here, no optical element is disposed on the optical path between the beam splitter and the sensor array. As a result, the factor for the positional deviation of the light spot on the surface of the photosensitive drum can be made equal to the factor for the positional deviation of the light spot on the light receiving surface of the light detection sensor.

  Further, here, each light detection sensor is disposed such that its light receiving surface is optically substantially equivalent to the surface of the corresponding photosensitive drum. Thereby, the beam diameter of the detection light beam that moves on the light receiving surface of each light detection sensor can be reduced, and the detection accuracy can be improved. Further, the positional deviation amount of the light spot on the surface of the photosensitive drum can be made equal to the positional deviation amount of the light spot on the light receiving surface of the light detection sensor. If each light detection sensor cannot be arranged so that its light receiving surface is optically substantially equivalent to the surface of the corresponding photosensitive drum, the amount of positional deviation of the light spot on the surface of the photosensitive drum A correlation coefficient (proportional coefficient) obtained in advance may be applied to the positional deviation amount of the light spot on the light receiving surface of the light detection sensor so as to be equal.

  By the way, when the temperature in the optical housing changes due to heat generated from the polygon mirror 2104 or heat from the outside, both the sheet metal member 301 and the image plane side scanning lens 2107 expand and contract due to the temperature change. However, since the sheet metal member 301 is made of metal and the image plane side scanning lens 2107 is made of resin, a difference occurs in the amount of expansion / contraction due to the difference in linear expansion coefficient.

  In the sheet metal member 301 to which the image plane side scanning lens 2107 is attached, the fitting portion between the stepping motor 315 and the sheet metal member 301 and the center fulcrum (the contact point between the column 322 and the column support unit 320) serve as fixed points. Therefore, asymmetric stress is generated in the M direction. Specifically, the end portion not fitted to the stepping motor 315 is supported only by the elastic force of the leaf spring 326, so it cannot be said that it is a fixed point, and the stress caused by the difference in expansion / contraction amount. Concentrated and greatly displaced in the sub-scanning corresponding direction (see FIGS. 31 and 32). FIG. 32 is a diagram simply showing a deformed state of the image plane side scanning lens 2107 at this time.

  The code | symbol (1) in FIG. 32 has shown the state before temperature changes. Since the image plane side scanning lens 2107 has a larger expansion / contraction amount, it is deformed as indicated by symbol (2) when the temperature is increased and deformed as indicated by symbol (3) when the temperature is decreased. As a result, the position of the light spot changes on the photosensitive drum according to the warp of the lens.

  FIG. 33 shows the results of measuring the light spot positions on the photosensitive drum when the ambient temperature is 25 ° C., 50 ° C., and 10 ° C., respectively. Here, the stepping motor 315 is disposed at a position where the image height corresponds to the minus side end, and the position where the image height corresponds to the plus side end is supported only by the elastic force of the leaf spring 326. When the temperature is 50 ° C. and 10 ° C., they are displaced in directions opposite to each other with respect to the temperature at 25 ° C.

  Note that the end of the sheet metal member 301 corresponding to the negative end of the image height functions as a fixed end because it is fastened to the stepping motor 315, but the image plane side scanning lens corresponding to the negative end of the image height. 2107 is not completely fixed to the sheet metal member 301. Therefore, the light spot position is also displaced at the negative end of the image height where the stepping motor 315 is disposed. However, the displacement of the light spot position is small compared to the position where the image height supported only by the elastic force of the leaf spring 326 corresponds to the plus side end. As described above, since the displacement amount of the light spot position is different between the plus side and the minus side of the image height, the scanning line is inclined on the photosensitive drum.

  As shown in FIG. 34 as an example, the scanning control device 3022 includes a CPU 3210, flash memory 3211, RAM 3212, liquid crystal element drive circuit 3213, IF (interface) 3214, pixel clock generation circuit 3215, image processing circuit 3216, write control. A circuit 3219, a light source driving circuit 3221, a motor driving circuit 3222, an LED driving circuit 3223, and the like are included. Note that the arrows in FIG. 34 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block.

  The pixel clock generation circuit 3215 generates a pixel clock signal. The pixel clock signal can be phase-modulated with a resolution of 1/8 clock.

  The image processing circuit 3216 performs predetermined halftone processing or the like on the image data rasterized for each color by the CPU 3210, and then creates dot data for each light emitting unit of each light source.

Write control circuit 3219, for each station is monitored on the basis of the output signal of the optical sensor 18 _1, when the first light receiving portion 18a has received the detection light beam, the fall in the output signal of the comparator 18d . When the falling edge is detected, the write start timing is obtained. Then, the dot data of each light emitting unit is superimposed on the pixel clock signal from the pixel clock generating circuit 3215 in accordance with the writing start timing, and independent modulation data is generated for each light emitting unit.

  The light source driving circuit 3221 outputs a driving signal for each light emitting unit to each light source unit in accordance with each modulation data from the writing control circuit 3219.

  The motor drive circuit 3222 is driven by a stepping motor 315A for finely adjusting the shape of each image plane side scanning lens and a drive signal for the stepping motor 315 for rotating each image plane side scan lens based on an instruction from the CPU 3210. Is output.

  The LED drive circuit 3223 is instructed by the CPU 3210 when a position shift detection process using the position shift detector 2245 is performed, and outputs a drive signal for each LED of the position shift detector 2245.

  The liquid crystal element driving circuit 3213 applies the applied voltage determined by the CPU 210 to each liquid crystal deflecting element.

  An IF (interface) 3214 is a communication interface that controls bidirectional communication with the printer control apparatus 2090. Image data from the host device is supplied via an IF (interface) 3214.

  The flash memory 3211 stores various programs described in codes readable by the CPU 3210 and various data necessary for executing the programs.

  The RAM 3212 is a working memory.

  The CPU 3210 operates according to a program stored in the flash memory 3211 and controls the entire optical scanning device 2010.

  For example, the CPU 3210 performs misregistration detection processing using the misregistration detector 2245 at the timing of starting up the apparatus or between jobs (for example, JP 2008-276010 A, JP 2005-238484 A). reference). Note that when the number of prints for one job is large, in order to suppress a shift due to a temperature change during that time, a position shift detection process may be performed by interrupting in the middle.

  The positional deviation detection process performed by the CPU 3210 will be briefly described. This misregistration detection process may be performed on the printer control device 2090 side. In this case, the detection result is notified from the printer control device 2090 to the scanning control device 3022.

(A) The toner patch TP is formed via the writing control circuit 3219 and transferred onto the transfer belt 2040.

(B) When a preset time elapses, each LED of the misalignment detector 2245 is turned on via the LED drive circuit 3223.

(C) ty, tm, tc, tk, tkc, tkm, and tky are obtained for each position Y1, Y2, and Y3 based on the output signal of each photosensor of the misregistration detector 2245 and stored in the flash memory 3211. .

(D) Each LED of the misalignment detector 2245 is turned off via the LED drive circuit 3223.

(E) For each position Y1, Y2, Y3, a predetermined calculation is performed using ty, tm, tc, tk, tkc, tkm, tky stored in the flash memory 3211, and the K station is used as a reference. Scan line bending deviation, scan line inclination deviation, and registration deviation in the sub-scanning direction in the other three stations (Y station, M station, and C station) (hereinafter, abbreviated as “sub-scan registration deviation” for convenience). For example, see Japanese Patent No. 4107578.

  Further, the CPU 3210 sets the sub-scanning deviation amount of the light beam on the surface of the photosensitive drum based on the output signal of each light detection sensor of the corresponding sensor array for each station before and after the above-described position deviation detection processing. Further, from the plurality of sub-scanning deviation amounts, the scanning line bending deviation, the scanning line inclination deviation, and the sub-scanning registration deviation at the other three stations with respect to the K station are obtained.

  Then, the CPU 3210 scans the scanning line obtained from the sensor array based on the scanning line bending deviation, the scanning line inclination deviation, and the sub-scanning registration deviation obtained from the positional deviation detection process. Each correction coefficient for correcting the shift and the sub-scanning registration shift is obtained. Each correction coefficient obtained here is stored in the flash memory 3211 in combination with an elapsed time since the power was turned on.

  Next, a description will be given of correction processing of a scan line bending deviation, a scan line inclination deviation, and a sub-scanning registration deviation performed by the CPU 3210 for each scan during image formation.

(1) For each station, the sub-scanning deviation amount of the light beam on the surface of the photosensitive drum is obtained based on the output signal of each light detection sensor of the corresponding sensor array, and further, from the plurality of sub-scanning deviation amounts, Using the K station as a reference, scanning line bending deviation, scanning line inclination deviation, and sub-scanning registration deviation in the other three stations are obtained.

(2) For the other three stations, each correction coefficient at the present time is predicted from each of a plurality of sets of correction coefficients stored in the flash memory 3211 and the current elapsed time from power-on.

(3) For the other three stations, using the correction coefficients predicted in (2) above, correct the scanning line bending deviation, scanning line inclination deviation, and sub-scanning registration deviation obtained in (1) above. Then, a new scanning line bending shift, a scanning line tilt shift, and a sub-scanning registration shift are set.

  Thereby, it is possible to improve the accuracy of the scanning line bending deviation, the scanning line inclination deviation, and the sub-scanning registration deviation obtained from the output signal of the sensor array. In other words, it is possible to accurately obtain the deviation of the scanning line bending, the inclination of the scanning line, and the sub-scanning registration deviation in real time.

(4) For the other three stations, a driving signal for correcting the bending deviation of the scanning line obtained in (3) above is generated for the corresponding stepping motor 315A and output to the motor driving circuit 3222. . Note that the relationship between the magnitude of the scan line bending deviation and the driving amount of the stepping motor 315A for correcting the deviation is obtained in advance and stored in the flash memory 3211.

(5) For the other three stations, a driving signal for correcting the tilt deviation of the scanning line obtained in (3) above is generated for the corresponding stepping motor 315 and output to the motor driving circuit 3222. . Note that the relationship between the magnitude of the inclination deviation of the scanning line and the driving amount of the stepping motor 315 for correcting it is obtained in advance and stored in the flash memory 3211.

(6) For the other three stations, the applied voltage of the corresponding liquid crystal deflecting element is determined so that the sub-scanning resist deviation obtained in (3) is substantially zero. Note that the relationship between the magnitude of the sub-scanning registration deviation and the applied voltage is obtained in advance and stored in the flash memory 3211.

  When the sub-scanning registration deviation obtained in the above (3) is ½ or more of the scanning line interval on the photosensitive drum, the image data is shifted so that the sub-scanning registration deviation is reduced. That is, the image data is shifted forward by one scan or more, or shifted by one scan or more.

Further, CPU3210 is, the light flux for each station, from the corresponding output signal of the light sensor 18 ₁ of the sensor array to the output signal of the optical sensor 18 _6, between the optical sensor 18 ₁ and the optical sensor 18 ₆ The time required for scanning is obtained, and the reference frequency of the pixel clock signal is reset so that a preset number of pulses fit within that time.

  Further, a temperature sensor for measuring the temperature in the optical housing may be provided, and the CPU 3210 may predict the correction coefficient in consideration of the output signal of the temperature sensor in (3) above.

  Further, the CPU 3210 may perform drive control of each stepping motor and determination of a voltage applied to each liquid crystal deflecting element based on the detection result of the position shift detection process immediately after the position shift detection process.

  As described above, according to the optical scanning device 2010 according to the present embodiment, the two light source units (2200a, 2200b), the polygon mirror 2104 that deflects the light beam from each light source unit, and the polygon mirror 2104 are deflected. Four scanning optical systems that individually collect light beams on the surfaces of the four photosensitive drums (2030a to 2030d), four sensor arrays (2111a to 2111d) provided corresponding to the four photosensitive drums, and A scanning control device 3022 and the like are provided.

  Each sensor array has six light detection sensors arranged at different positions in the main scanning direction. Of these, four of the light detection sensors are partially misaligned in the sub-scanning direction of the light beam that is partially incident on the polygon mirror 2104 and the corresponding scanning optical system and is focused on the effective scanning region of the corresponding photosensitive drum. Output a signal containing information.

  In this case, the CPU 3210 can accurately obtain the deviation of the scanning line bending, the inclination of the scanning line, and the sub-scanning registration deviation in real time.

  The CPU 3210 controls driving of each stepping motor via the motor driving circuit 3222 so that the scanning line bending deviation and the scanning line inclination deviation are corrected. That is, it is possible to correct the deviation of the scanning line and the inclination of the scanning line with high accuracy in real time.

  Further, the CPU 3210 determines the voltage applied to the liquid crystal deflecting element so that the sub-scanning resist deviation is substantially zero, and applies it to the corresponding liquid crystal deflecting element via the liquid crystal element driving circuit 3215. That is, the sub-scanning registration deviation can be corrected with high accuracy in real time.

  Therefore, even if the temperature in the optical housing rises during operation, it is possible to suppress the bending of the scanning line, the inclination of the scanning line, and the sub-scanning resist from being different between stations.

  Therefore, stable and highly accurate optical scanning can be performed.

  In addition, since each light source unit has the two-dimensional array 100, it is possible to simultaneously perform a plurality of optical scans on one photosensitive drum.

  Since the color printer 2000 according to the present embodiment includes the optical scanning device 2010, the color misregistration can be made smaller than the conventional one. As a result, it is possible to stably form a high quality image.

  In addition, since the optical scanning device 2010 includes a light source unit having a two-dimensional array, an image can be formed at high speed. In addition, the density of the formed image can be increased.

  In addition, by connecting the color printer 2000 to an electronic arithmetic device (such as a computer) or an image information communication system (such as a facsimile) via a network, output from a plurality of devices can be performed with a single image forming apparatus. An information processing system that can be processed can be formed. In addition, if multiple image forming devices are connected to the network, the status of each image forming device (the degree of job congestion, whether the power is on, whether it is broken, etc.) can be known from each output request. The image forming apparatus having the best state (most suitable for the user's request) can be selected and image formation can be performed.

  In the above embodiment, as shown in FIG. 35 as an example, a light source unit 2200a ′ is provided in addition to the light source unit 2200a, and the light beam emitted from the light source unit 2200a ′ passes through the polygon mirror 2104 and the scanning optical system. The light may be incident on the light detection sensor. In this case, since the light beam emitted from the light source unit 2200a ′ is obliquely incident on the optical system, the amount of positional deviation of the light spot on the light receiving surface of the light detection sensor and the light beam emitted from the light source unit 2200a. Although the amount of positional deviation of the light spot on the surface of the photosensitive drum 2030a does not match, there is a correlation because the optical elements that pass through are common. Therefore, a relative comparison of the respective positional deviation amounts is performed in advance to obtain a correlation coefficient such as a proportional coefficient, and the result of detection by the light detection sensor is multiplied by the correlation coefficient, whereby the surface of the photosensitive drum 2030a is obtained. The amount of positional deviation of the light spot can be obtained. Further, in this case, the beam splitter 2100a is not necessary, and the influence of the posture change of the beam splitter 2100a is eliminated, and the positional deviation can be detected with higher accuracy.

  Further, instead of the beam splitter 2100a, a polarization beam splitter that transmits the light beam from the light source unit 2200a is used. A light source unit that emits light as a detection light beam may be provided. In this case, the detection light beam does not have to be obliquely incident on the optical system.

  In the above embodiment, a half mirror may be used instead of the beam splitter.

  Moreover, although the said embodiment demonstrated the case where the beam splitter also served as dustproof glass, it is not limited to this. However, when a dustproof glass is provided separately, it is preferable that no optical element is disposed on the optical path between the beam splitter and the photosensitive drum in order to prevent a decrease in detection accuracy.

  In the above-described embodiment, the case where the protruding amount of the adjusting screw 308 is adjusted to finely adjust the shape of the image plane side scanning lens 2107 is described, but the present invention is not limited to this. For example, the shape of the image side scanning lens 2107 may be finely adjusted using an actuator. As the actuator, for example, a piezoelectric element (piezo element) that can change the pressing force by changing the magnitude of the applied voltage can be used.

  In the above embodiment, at least a part of the processing according to the program by the CPU 3210 may be configured by hardware, or all may be configured by hardware.

  Moreover, although the said embodiment demonstrated the case where the said 1st light-receiving part 18a was a rectangular shape, it is not limited to this, If the two sides which the light beam for a detection passes are a shape parallel to s direction, it is. good.

  Moreover, although the said 2nd light-receiving part 18b demonstrated the case where the said 2nd light-receiving part 18b was a parallelogram shape in the said embodiment, it is not limited to this, Two sides through which the light beam for a detection passes incline with respect to s direction. Any shape can be used.

  Moreover, although the said embodiment demonstrated the case where each sensor array had six optical detection sensors, it is not limited to this. Each sensor array only needs to have at least two light detection sensors on which a light beam separated from a light beam traveling toward the effective scanning region is incident. Note that as the number of light detection sensors increases, the detection accuracy of scanning line bending deviation, scanning line inclination deviation, and sub-scanning registration deviation improves.

  In the above-described embodiment, a light detection sensor for synchronization detection (for front-end synchronization detection and rear-end synchronization detection) may be provided separately from the sensor array.

  Moreover, although the said embodiment demonstrated the case where the light source 14 had 40 light emission parts, it is not limited to this.

  Moreover, in the said embodiment, it may replace with the said liquid-crystal deflection | deviation element, and may use the non-parallel plate and galvanometer mirror which can be rotated around the axis | shaft parallel to a Z-axis direction.

  In the above embodiment, instead of shifting the image data, the light emitting unit to be driven may be shifted to another light emitting unit adjacent in the sub-scanning corresponding direction.

  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, any image forming apparatus including the optical scanning device 2010 may be used.

  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.

  Further, an image forming apparatus using a silver salt film as the image carrier may be used. In this case, a latent image is formed on the silver salt film by optical scanning, and this latent image can be visualized by a process equivalent to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by a process equivalent to a printing process in a normal silver salt photographic process. Such an image forming apparatus can be implemented as an optical plate making apparatus or an optical drawing apparatus that draws a CT scan image or the like.

  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. .

  In the above embodiment, the case where there are four photosensitive drums has been described. However, the present invention is not limited to this.

  The optical scanning device of the present invention is suitable for performing optical scanning stably and with high accuracy. The image forming apparatus of the present invention is suitable for stably forming a high-quality image.

18 ₁ to 18 ₆ ... Optical detection sensor, 315... Stepping motor (part of the rotation mechanism), 315 A... Stepping motor (part of the adjustment mechanism), 2000 ... color printer (image forming apparatus), 2010. , 2030a, 2030b, 2030c, 2030d ... photosensitive drum (image carrier), 2080 ... communication control device (communication device), 2104 ... polygon mirror (deflector), 2105a to 2105d ... deflector side scanning lens (scanning optical system) 2107a to 2107d ... Image plane side scanning lens (part of the scanning optical system), 2110a to 2110d ... Beam splitter (light separation element), 2111a to 2111d ... Sensor array, 2200a, 2200b ... Light source unit, 2245a To 2245c ... position detection sensor (pattern detection sensor), 3022 ... Scanning control device (position shift correction device, tilt correction device, optical path adjustment device, control device), TP ... toner patch (detection pattern).

Japanese Patent No. 4107578 JP 2004-287380 A JP 2004-258182 A JP 2008-275961 A

Claims (17)

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 the light flux from the light source;
A scanning optical system including a scanning optical element for condensing the light beam deflected by the deflector onto the surface to be scanned;
Arranged at different positions with respect to the main scanning direction, a part of a light beam directed to a region where image information is written on the scanned surface enters through the deflector and the scanning optical system, and is condensed on the scanned surface. A plurality of light detection sensors for outputting a signal including positional deviation information regarding the sub-scanning direction of the light flux to be emitted. A light separation element disposed on an optical path of a light beam from the scanning optical system toward the scanned surface, and further separating the light beam into two light beams;
The optical scanning device according to claim 1, wherein the plurality of light detection sensors are disposed on an optical path of one light beam separated by the light separation element. One light beam separated by the light separation element is directly incident on the plurality of light detection sensors,
The optical scanning apparatus according to claim 2, wherein the other light beam separated by the light separation element directly irradiates the scanned surface. The deflector, the scanning optical system, and the plurality of light detection sensors are housed in an optical housing,
The optical housing has a slit through which a light beam traveling toward the scanned surface passes through the scanning optical system,
4. The optical scanning device according to claim 2, wherein the light separation element is attached to a portion of the optical housing that includes the slit.   2. The optical scanning device according to claim 1, further comprising a light source that emits a light beam incident on the plurality of light detection sensors via the deflector and the scanning optical system, in addition to the light source. The scanning optical element has an adjustment mechanism for finely adjusting the shape of the scanning optical element in the sub-scanning direction,
The positional deviation correction apparatus which drives the said adjustment mechanism according to the positional deviation information obtained from the output signal of these several photon detection sensors is further provided, The Claim 1 characterized by the above-mentioned. Optical scanning device.   The adjustment mechanism includes a pressing member that presses the scanning optical element toward one side and an elastic member that biases the scanning optical element toward the other side in the sub-scanning direction. The optical scanning device according to claim 6. The scanning optical element has a rotation mechanism for rotating the scanning optical element about an axis orthogonal to both the main scanning direction and the sub-scanning direction,
8. The apparatus according to claim 1, further comprising an inclination correction device that drives the rotation mechanism in accordance with positional deviation information obtained from output signals of the plurality of light detection sensors. 9. Optical scanning device. A liquid crystal element for finely adjusting the optical path of the light beam emitted from the light source in the sub-scanning direction;
The optical path adjustment device which determines the applied voltage to the said liquid crystal element according to the positional offset information obtained from the output signal of these light detection sensors further, The any one of Claims 1-8 characterized by the above-mentioned. The optical scanning device according to one item.   The optical scanning device according to claim 1, wherein the light source includes a plurality of light emitting units arranged two-dimensionally. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to claim 1 that scans the at least one image carrier with a light beam modulated according to image information.   The image forming apparatus according to claim 11, wherein the image information is multicolor image information. At least one pattern detection sensor for detecting a detection pattern formed on the at least one image carrier and transferred to a medium;
13. The control device according to claim 12, further comprising: a control device that corrects a positional deviation of a light beam condensed on the at least one image carrier in accordance with an output signal of the at least one pattern detection sensor. Image forming apparatus.   The control device obtains a correction coefficient for correcting positional deviation information obtained from output signals of a plurality of light detection sensors in the optical scanning device, based on an output signal of the at least one pattern detection sensor. The image forming apparatus according to claim 13. The correction coefficient is obtained every predetermined timing,
The image forming apparatus according to claim 14, wherein the control apparatus predicts a correction coefficient at a current time based on a correction coefficient obtained previously. A temperature sensor for measuring the temperature in the optical housing of the optical scanning device;
The image forming apparatus according to claim 15, wherein the control device further predicts a correction coefficient at a current time in consideration of temperature information obtained from the temperature sensor.   The image forming apparatus according to claim 11, further comprising a communication device that communicates various information including the image information with an external device via a network.

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