JP2009157154A - Optical scanner and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner and image forming device which can correct the start position errors or horizontal scanning line magnification errors after adjusting the inclination without forming a check mark image. <P>SOLUTION: This optical scanner has a laser diode to emit a light beam, a deflector composed of a polygon motor and a polygon mirror to deflect the writing light which is the light beam emitted from the laser diode in the main scanning direction, a reflecting mirror to reflect the writing light, and an inclination adjuster to adjust the inclination of the horizontal scanning line on the surface of a photoreceptor to scan by changing the attitude of the reflection mirror. Further, it has a controller functioning as a compensator to correct at least either the write start position errors or the horizontal scanning line magnification errors based on the reflecting mirror attitude changed by the inclination adjuster. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical scanning apparatus and an image forming apparatus that correct inclination of a main scanning line of an optical scanning apparatus that optically scans a scanning object.

  Conventionally, a so-called tandem type color image forming apparatus that forms images of different colors (visible images) on a plurality of latent image carriers and overlays these images to form a color image is known. Yes. The tandem image forming apparatus has a plurality of latent image carriers such as photoconductors, and forms a latent image by optical scanning on each latent image carrier that is a scanning object. Then, the latent images are developed with different color toners to obtain visible images of different colors on the respective latent image carriers. Next, a visible image on each latent image carrier is transferred onto the transfer body so as to obtain a multicolor image by superimposing single-color visible images.

  In such a configuration, when the visible images are formed on the plurality of latent image carriers so as to be displaced relative to each other, they are transferred to the transfer member in a state of being displaced so that a color image is formed on the multicolor image. Cause a gap. One cause of this color misregistration is the inclination of scanning lines in the main scanning direction (hereinafter referred to as main scanning lines) on the surface of the latent image carrier. Specifically, the housing of the optical scanning device that optically scans the latent image carrier, the thermal deformation of various components constituting the optical scanning device due to the heat generated by the polygon motor, the twist when the latent image carrier is attached, etc. As a result, the main scanning line on the surface of the latent image carrier is inclined.

  Patent Document 1 discloses a scanning optical device that can adjust the inclination of a scanning line. This scanning optical device adjusts the inclination of the main scanning line by changing the posture of the reflecting mirror provided on the beam path between the laser light source and the latent image carrier.

JP 2001-100135 A

  However, in the scanning optical device that adjusts the inclination of the main scanning line by changing the posture of the reflecting mirror, there are problems that the writing start position is shifted or a magnification error occurs after the inclination adjustment.

  For this reason, after adjusting the inclination, the writing start position on the surface of the conveyance belt for conveying the transfer material or the intermediate transfer belt on which the image on the photosensitive member is intermediately transferred, and detection for detecting a magnification error deviation are detected. It may be possible to solve the above problem by forming a mark image and correcting the writing start position and the magnification error deviation based on the detection result of the detected mark image. However, since the detection mark image is formed and detected, the time for adjusting the inclination of the scanning line becomes long, and the so-called apparatus down time in which the image forming operation cannot be performed becomes long.

  The present invention has been made in view of the above problems, and an object of the present invention is to correct a writing start position shift or main scanning line magnification error after tilt adjustment without forming a detection mark image. An optical scanning device and an image forming apparatus are provided.

To achieve the above object, the invention of claim 1 is directed to a light beam emitting means, a deflecting means for deflecting the light beam emitted from the light beam emitting means in a main scanning direction, and a reflection for reflecting the light beam. In an optical scanning device comprising: a mirror; and an inclination adjusting unit that adjusts an inclination of a main scanning line on a surface of the scanning object by changing an attitude of the reflecting mirror, and optically scans the scanning object with the light beam And a correction unit that corrects at least one of the writing position and the main scanning line magnification error based on the amount of change in the posture of the reflecting mirror by the tilt adjusting unit.
According to a second aspect of the present invention, in the optical scanning device according to the first aspect, the inclination adjusting means has one end of the reflecting mirror with respect to the mirror surface of the reflecting mirror with the central portion in the longitudinal direction of the reflecting mirror as a center. It is characterized in that the tilt is adjusted by swinging in an orthogonal direction.
According to a third aspect of the present invention, in the optical scanning device according to the first or second aspect, the tilt adjusting unit includes a motor capable of controlling a rotation angle, and the rotation angle of the motor is controlled. An optical scanning device configured to adjust the inclination of the main scanning line.
According to a fourth aspect of the present invention, in the optical scanning device according to any one of the first to third aspects, an angle formed by the light beam incident on the reflecting mirror and the light beam reflected by the reflecting mirror is an obtuse angle. It is characterized by comprising.
According to a fifth aspect of the present invention, in the optical scanning device according to any one of the first to fourth aspects, the light beam emitting means includes a plurality of light beam emitting means, and the light beams emitted from the light beam emitting means are individually used by the deflecting means. It is configured to deflect, reflect on different reflecting mirrors and optically scan different scanning objects, and provide the tilt adjusting means on the reflecting mirror corresponding to each light beam.
According to a sixth aspect of the present invention, in the optical scanning device according to the fifth aspect, each of the scanning objects has a latent image carrier that carries a Y-color toner image, and a latent image carrier that carries a M-color toner image. , A latent image carrier that carries a C-color toner image, and a latent image carrier that carries a K-color latent image.
Further, the invention of claim 7 includes a plurality of photoconductors, optical scanning means for individually scanning each of these photoconductors to form a latent image, and latent images formed on each photoconductor. In an image forming apparatus comprising a plurality of developing means for developing individually and a transfer means for transferring a visible image obtained on each photosensitive member by superimposing onto a transfer body, the optical scanning means is claimed as the optical scanning means. The optical scanning device according to Item 5 or 6 is used.

  As a result of diligent research, the present inventor has found that the writing start position deviation and the main scanning line magnification error after tilt adjustment have a predetermined relationship with the amount of change in the attitude of the reflecting mirror. Therefore, the writing start position deviation and the main scanning line magnification error can be obtained from the change in the attitude of the reflecting mirror, and the writing start position deviation and the main scanning line magnification error after adjusting the tilt without forming a detection mark image. Can be corrected.

  According to the first to seventh aspects of the present invention, at least one of the deviation of the writing start position after the main scanning line tilt correction and the main scanning line magnification error is corrected based on the amount of change in the attitude of the reflecting mirror. Without forming an image, it is possible to correct a writing start position shift or main scanning line magnification error after tilt adjustment. Therefore, the tilt adjustment time can be shortened and downtime of the apparatus can be reduced as compared with the case where the detection mark image is formed and at least one of the deviation of the start position and the main scanning line magnification error is corrected.

Hereinafter, a first embodiment in which the present invention is applied to an electrophotographic color laser printer (hereinafter simply referred to as a printer) will be described.
FIG. 1 is a schematic configuration diagram illustrating a printer according to the first embodiment. The printer includes a housing 1 and a paper feed cassette 2 that can be pulled out from the housing 1. Image forming stations 3Y, 3C, and 3C for forming toner images (visible images) of each color of yellow (Y), cyan (C), magenta (M), and black (K) are provided at the center of the housing 1. 3M, 3K. Hereinafter, the subscripts Y, C, M, and K of the respective symbols indicate members for yellow, cyan, magenta, and black, respectively.

FIG. 2 is a schematic configuration diagram showing an image forming station for yellow (Y). The other image forming stations have the same configuration.
As shown in FIGS. 1 and 2, the image forming stations 3Y, 3C, 3M, and 3K include drum-shaped photoconductors 10Y, 10C, 10M, and 10K as latent image carriers that rotate in the direction of arrow A in the drawing. ing. Each of the photoreceptors 10Y, 10C, 10M, and 10K includes an aluminum cylindrical substrate having a diameter of 40 [mm] and an OPC (organic photo semiconductor) photosensitive layer that covers the surface of the photoreceptor. Each of the image forming stations 3Y, 3C, 3M, and 3K includes charging devices 11Y, 11C, 11M, and 11K that charge the photoconductors around the photoconductors 10Y, 10C, 10M, and 10K, respectively. Further, developing devices 12Y, 12C, 12M, and 12K as developing means for developing the latent image formed on the photosensitive member, and cleaning devices 13Y, 13C, 13M, and 13K for cleaning residual toner on the photosensitive member are also provided around the photosensitive member. In preparation.

  Below each of the image forming stations 3Y, 3C, 3M, and 3K, there is provided an optical writing unit 4 as an optical scanning device that performs optical scanning with the writing light L on the photoreceptors 10Y, 10C, 10M, and 10K. Yes. Further, an intermediate transfer unit 5 including an intermediate transfer belt 20 to which toner images formed by the image forming stations 3Y, 3C, 3M, and 3K are transferred above the image forming stations 3Y, 3C, 3M, and 3K. It has. Further, a fixing unit 6 is provided for fixing the toner image transferred to the intermediate transfer belt 20 onto a recording paper P as a transfer member. In addition, toner bottles 7Y, 7C, 7M, and 7K that contain toner of each color of yellow (Y), cyan (C), magenta (M), and black (K) are loaded on the top of the casing 1. . The toner bottles 7 </ b> Y, 7 </ b> C, 7 </ b> M, and 7 </ b> K can be detached from the housing 1 by opening a paper discharge tray 8 formed on the top of the housing 1.

  The optical writing unit 4 as an optical scanning device has a laser diode which is a light beam emitting means, and writing from the laser diode toward a polygon mirror having a regular polygonal column structure which is driven to rotate is performed as a light beam. Incident light L is emitted. The emitted writing light L is reflected while being deflected in the main scanning direction by the mirror surface of the rotating polygon mirror. Then, after being folded by a plurality of reflecting mirrors, the peripheral surfaces of the photoreceptors 10Y, 10C, 10M, and 10K that are uniformly charged by the charging devices 11Y, 11C, 11M, and 11K are scanned. Thereby, electrostatic latent images for Y, C, M, and K are formed on the peripheral surfaces of the photoreceptors 10Y, 10C, 10M, and 10K as latent image carriers. The detailed description of the optical writing unit 4 will be described later.

  The intermediate transfer belt 20 of the intermediate transfer unit 5 serving as transfer means is driven to rotate counterclockwise in the figure at a predetermined timing while being wound around a drive roller 21, a tension roller 22 and a driven roller 23. In addition, the intermediate transfer unit 5 includes primary transfer rollers 24Y, 24C, 24M, and 24K that primarily transfer the toner images formed on the photoreceptors 10Y, 10C, 10M, and 10K to the intermediate transfer belt 20. Further, a secondary transfer roller 25 that transfers the toner image primarily transferred onto the intermediate transfer belt 20 to the recording paper P, and a belt that cleans residual toner on the intermediate transfer belt 20 that has not been transferred onto the recording paper P. A cleaning device 26 is also provided.

Next, a process for obtaining a color image in this printer will be described.
First, in the image forming stations 3Y, 3C, 3M, and 3K, the photoreceptors 10Y, 10C, 10M, and 10K are uniformly charged by the charging devices 11Y, 11C, 11M, and 11K. Thereafter, scanning exposure is performed with the writing light L generated based on the image information, and electrostatic latent images are formed on the surfaces of the photoreceptors 10Y, 10C, 10M, and 10K. These electrostatic latent images are developed with toners of the respective colors carried on the developing rollers 15Y, 15C, 15M, and 15K of the developing devices 12Y, 12C, 12M, and 12K, and are converted into Y, C, M, and K toner images. Become. The Y, C, M, and K toner images on the photoreceptors 10Y, 10C, 10M, and 10K are formed on the intermediate transfer belt 20 that is rotated counterclockwise by the action of the primary transfer rollers 24Y, 24C, 24M, and 24K. The primary transfer is carried out in order. The image forming operation of each color at this time is shifted in timing from the upstream side in the moving direction of the intermediate transfer belt 20 toward the downstream side so that the toner image is transferred to the same position on the intermediate transfer belt 20. Executed.

  The surfaces of the photoconductors 10Y, 10C, 10M, and 10K after the completion of the primary transfer are cleaned by the cleaning blades 13a of the cleaning devices 13Y, 13C, 13M, and 13K to prepare for the next image formation.

  The toner filled in the toner bottles 7Y, 7C, 7M, and 7K is placed in the developing devices 12Y, 12C, 12M, and 12K of the image forming stations 3Y, 3C, 3M, and 3K by a conveyance path (not shown) as necessary. A fixed amount is supplied.

  On the other hand, the recording paper P in the paper feed cassette 2 is transported into the housing 1 by a paper feed roller 27 disposed in the vicinity of the paper feed cassette 2 and is secondary by a registration roller pair 28 at a predetermined timing. It is conveyed to the transfer unit. Then, the toner image formed on the intermediate transfer belt 20 is transferred to the recording paper P in the secondary transfer portion. The recording paper P onto which the toner image has been transferred passes through the fixing unit 6 to fix the toner image, and is then discharged to the paper discharge tray 8 by the discharge roller 29. Similar to the photoconductor 10, the transfer residual toner remaining on the intermediate transfer belt 20 is cleaned by a belt cleaning device 26 that contacts the intermediate transfer belt 20.

Next, the configuration of the optical writing unit 4 will be described.
FIG. 3 is a schematic configuration diagram showing the optical writing unit 4 in the printer according to the first embodiment together with four photoconductors. The optical writing unit 4 includes two polygon mirrors 41a and 41b having a regular polygonal column structure. These polygon mirrors 41a and 41b have reflecting mirrors on their six side surfaces, and are connected in the vertical direction so that the centers of the regular polygonal columns overlap each other. And it rotates at high speed on the same axis of rotation by a polygon motor (not shown). Thereby, when the writing light (laser light) from the laser diode (light source) is incident on the side surface, the writing light is deflected and scanned. The polygon mirror 41a deflects the C and M writing lights Lc and Lm traveling from opposite directions to the main scanning direction. The polygon mirror 41b deflects Y and K writing lights Ly and Lk traveling in opposite directions to the main scanning direction.

  In the illustrated optical writing unit 4, deflecting means for deflecting the writing light L as a light beam is configured by polygon mirrors 41 a and 41 b, a polygon motor (not shown), and the like. The optical writing unit 4 has four deflecting optical systems, soundproof glasses 42a and 42b, scanning lenses 43a and 43b, dustproof glasses 48a, 48b, 48c, and 48d in addition to the deflecting means.

  The polygon motor and the polygon mirrors 41a and 41b are covered with a polygon cover member for soundproofing. For the purpose of allowing the writing light to pass inside and outside the polygon cover member, the polygon cover is provided with soundproof glasses 42a and 42b. Writing light as a light beam passes through the soundproof glasses 42a and 42b, so that it can go back and forth inside the polygon cover. The soundproof glass 42a is for transmitting the Y and C writing lights Ly and Lc. The soundproof glass 42b is for transmitting the M and K writing lights Lm and Lk.

  The Y and C writing lights Ly and Lc transmitted through the soundproof glass 42a while being deflected in the main scanning direction by the polygon mirror pass through the scanning lens 43a while being aligned in the vertical direction. The scanning lens 43a condenses the writing lights Ly and Lc in the main scanning line direction and the sub-scanning line direction, thereby changing the equiangular motion in the main scanning direction by the polygon mirror to constant velocity linear motion, and the polygon mirror It plays a role of correcting the trouble of falling. The M and K writing lights Lm and Lk that have passed through the soundproof glass 42b pass through the scanning lens 43b located on the opposite side of the scanning lens 43a through the polygon cover.

  The four reflecting optical systems in the optical writing unit 4 are each composed of the above-described laser diode, reflecting mirror, and the like. More specifically, of the colors Y, C, M, and K, taking a Y reflecting optical system as an example, this includes a Y laser diode (not shown), a first reflecting mirror 44Y, and a second reflecting mirror 45Y. And a third reflecting mirror 46Y. None of these reflecting mirrors has a lens function. Similarly, the reflection optical system for C, M, and K includes a laser diode, a first reflecting mirror (44C to K), a second reflecting mirror (45C to K), and a third reflecting mirror 46 (C to K). Have.

  The Y, C, M, and K writing lights Ly, Lc, Lm, and Lk that have passed through the scanning lenses 43a and 43b travel to the reflecting mirrors of the Y, C, M, and K reflecting optical systems. For example, the Y writing light Ly that has passed through the scanning lens 43a is reflected three times by sequentially reflecting the mirror surfaces of the first reflecting mirror 44Y, the second reflecting mirror 45Y, and the third reflecting mirror 46Y. Is guided to the surface of the photosensitive member 10Y. Similarly, the laser beams Lc, Lm, and Lk for C, M, and K are folded back by three dedicated reflecting mirrors, respectively, so that they are guided to the surfaces of the C, M, and K photoconductors 10C, M, and K. To go. The Y, C, M, and K writing lights Ly, Lc, Lm, and Lk reflected by the mirror surfaces of the third reflecting mirrors 46 Y, C, M, and K are provided on the upper surface of the optical writing unit 4. After passing through the dustproof glasses 48Y, 48C, 48M, and 48K, the light reaches the surfaces of the photoconductors 10Y, 10M, 10C, and 10K.

Next, a characteristic configuration of the printer will be described.
The optical writing unit 4 of this printer includes an inclination adjusting means for adjusting the inclination of the main scanning line by adjusting the posture of any one of the reflecting mirrors in the Y, C, M, and K reflecting optical systems. Is provided. Hereinafter, the tilt adjusting means will be described by taking the Y reflecting optical system as an example.

  FIG. 4 is a perspective view showing the third reflecting mirror 46Y for Y and the surrounding configuration from the back surface side (non-mirror surface side) of the third reflecting mirror 46Y. In the drawing, the third reflecting mirror 46Y is held by a holder 52Y having a U-shaped cross-sectional shape existing on the back side thereof. And the both ends of a longitudinal direction are made to protrude from the longitudinal direction both ends of the holder 52Y, respectively.

  The tilt adjusting means is in contact with one end of the third reflecting mirror 46Y in the longitudinal direction. The tilt adjusting means includes a tilt adjusting pulse motor 56Y, a motor holder 57Y, a tilt adjusting adjuster 58Y, and the like.

  FIG. 5 is a side view showing the tilt adjusting pulse motor 56Y and the tilt adjusting adjuster 58Y of the tilt adjusting means from the side. FIG. 6 is a plan view showing the motor holder 57Y and the tilt adjustment adjuster 58Y of the tilt adjusting means. As shown in FIG. 5, a male screw portion 56bY is provided on the rotation shaft 56aY of the inclination adjusting pulse motor 56Y. The inclination adjustment adjuster 58 is fixed to the rotation shaft 56aY by screwing a female screw portion provided on the tilt adjustment adjuster 58 to the male screw portion 56bY. As shown in FIG. 6, the inclination adjustment adjuster 58 </ b> Y has a D-shaped cross section, and is inserted into a D-shaped adjuster insertion port 57 a </ i> Y provided in the motor holder 57. Even if the rotation shaft 56aY of the tilt adjustment pulse motor 56Y rotates, the tilt adjustment adjuster 58Y does not rotate because it is locked to the adjuster insertion port 57aY. And it raises / lowers in the arrow D direction of FIG. 5 by the screw feed accompanying rotation of the rotating shaft 56aY.

  In FIG. 4 shown above, the motor holder 57Y holding the tilt adjustment pulse motor 56Y is fixed to the housing of the printer main body (not shown). The top of the tilt adjustment adjuster 58Y screwed to the screw portion of the rotation shaft of the tilt adjustment pulse motor 56Y is in contact with the mirror surface of the end of the third reflecting mirror 46Y.

  On the other hand, the end of the third reflecting mirror 46Y opposite to the tilt adjusting pulse motor 56Y (hereinafter referred to as “fulcrum side end”) is on a support 66Y fixed to the housing of the printer main body (not shown). It is on. In this state, the leaf spring 69 fixed to the housing (not shown) is pressed against the back surface, so that it is sandwiched between the support base 66Y and the leaf spring 69Y.

  When the tilt adjustment adjuster (58Y in FIG. 5) screwed to the rotation shaft of the tilt adjustment pulse motor 56Y moves up and down with the rotation of the rotation shaft, the pushing amount of the tilt adjustment adjuster with respect to one end of the third reflecting mirror 46Y. Changes. As a result, the motor-side end of the third reflecting mirror 46Y swings in the adjuster ascending / descending direction with the fulcrum-side end sandwiched between the support base 66Y and the leaf spring 69 as a fulcrum. Then, the tilt of the third reflecting mirror 46Y changes due to this swing. That is, the tilt of the third reflecting mirror 46Y shown in the drawing is adjusted by adjusting the rotation amount of the tilt adjusting pulse motor 56Y.

FIG. 7 is a diagram for explaining main scanning lines on the photoreceptor 10Y when the third reflecting mirror 46Y is tilted.
As shown in the figure, when the third reflecting mirror 46Y is tilted for tilt adjustment, the direction in which the third reflecting mirror 46Y reflects the writing light Ly is shifted in the main scanning line direction and formed on the photoconductor. The written main scanning line is shifted in the main scanning line direction, and the writing start position is shifted. Further, since the optical path length of the writing light Ly changes in the longitudinal direction of the third reflecting mirror 46Y, a magnification error occurs in the main scanning direction. As a result, color deviation may occur in the main scanning line direction after inclination correction. Therefore, after the tilt adjustment, a mark image for detecting the deviation of the writing start position and the magnification error is formed on the intermediate transfer belt 20 and detected by an optical sensor (not shown). Based on the detection result, the mark starting position is determined. Although it is conceivable to correct the misalignment and magnification error, there arises a problem that the time for color misregistration adjustment becomes longer and the downtime of the apparatus becomes longer.
Therefore, in the present embodiment, the writing start position and the magnification error are corrected based on the tilt amount of the third reflecting mirror 46Y. This will be specifically described below.

FIG. 8 is a control block diagram of the printer.
In the figure, the control unit 200 includes a CPU 200a (Central Processing Unit) as a calculation means, a RAM 200c (Random Access Memory) as a nonvolatile memory, a ROM 200b (Read Only Memory) as a temporary storage means, and the like. The control unit 200 controls the entire apparatus, and various devices and sensors are connected. In the figure, only the devices and sensors related to the feature points of the printer are shown. The control unit 200 realizes the function of each unit based on a control program stored in the RAM 200c or the ROM 200b. Specifically, the control unit 200 calculates a writing start position shift and a magnification error from the tilt amount of the third reflecting mirror, and functions as a correction unit that corrects the writing start position shift and the magnification error after the tilt adjustment. To do.

FIG. 9 is a diagram for explaining the calculation of the magnification error and the writing start position deviation when the reflecting mirror is tilted.
As shown in the figure, when the inclination angle of the third reflecting mirror 46Y is θ, and the distance from the fulcrum of the third reflecting mirror 46Y to the irradiation position of the writing light incident last on the third reflecting mirror 46Y is L. The magnification error Δb can be expressed by L (1−COSθ). The irradiation position of the writing light finally incident on the third reflecting mirror 46Y is almost the end opposite to the fulcrum of the third reflecting mirror 46, and finally the third reflecting mirror 46Y from the fulcrum to the third reflecting mirror 46Y. The distance L to the irradiation position of the incident writing light may be considered as the distance from the fulcrum of the third reflecting mirror 46Y to the end opposite to the fulcrum of the third reflecting mirror. Moreover, since the position of the fulcrum is almost the end of the third reflecting mirror, the position of the fulcrum may be considered as the end of the third reflecting mirror. Therefore, the distance L from the fulcrum of the third reflecting mirror 46Y to the irradiation position of the writing light that finally enters the third reflecting mirror 46Y may be approximated by the length in the longitudinal direction of the third reflecting mirror.
L is known in advance at the time of design, and the inclination angle θ is obtained from the rotation angle of the inclination adjustment pulse motor 56Y. Therefore, L is stored in a nonvolatile memory such as a RAM, the inclination angle θ is obtained from the rotation amount of the inclination adjustment pulse motor 56Y, and based on the obtained inclination angle θ and L stored in the nonvolatile memory, Magnification error is calculated.

  The control unit 200 corrects the magnification error by correcting the pixel clock frequency based on the calculated magnification error.

  Further, when the distance L ′ from the fulcrum of the third reflecting mirror 46Y to the irradiation position of the writing light first incident on the third reflecting mirror 46Y is set, the writing start position deviation Δc is L ′ (1-COSθ). Can be expressed as The distance L ′ from the fulcrum of the third reflecting mirror 46Y to the irradiation position of the writing light first incident on the third reflecting mirror 46Y is also known at the time of design, and the inclination angle θ is determined from the rotation angle of the inclination adjusting pulse motor 56Y. I understand. Therefore, L ′ is stored in a nonvolatile memory such as a RAM, the inclination angle θ is obtained from the rotation amount of the inclination adjustment pulse motor 56Y, and based on the obtained inclination angle θ and L ′ stored in the nonvolatile memory. Thus, the writing start position deviation is calculated.

  The control unit 200 corrects the writing start position deviation by correcting the irradiation start timing based on the image data of the laser diode based on the calculated writing start position deviation. As shown in FIG. 9, when the third reflecting mirror 46Y is tilted to the holder side, correction is made to accelerate the irradiation start timing based on the image data of the laser diode, and the third reflecting mirror 46Y is tilted to the mirror surface side. In some cases, the irradiation start timing based on the image data of the laser diode is corrected so as to be delayed.

  Although the tilt adjusting means in the Y reflecting optical system has been described, the C, M, and K reflecting optical systems have the same configuration.

FIG. 10 is an execution flowchart for adjusting the inclination of the main scanning line.
The inclination of the main scanning line on the photosensitive member is adjusted at the time of shipment of the printer, and at the time of operation of the printer, for example, a predetermined timing such as a timing when the number of prints reaches a predetermined number or a timing when a user instruction is received. But it is done. In the tilt adjustment, first, a misalignment detection pattern image is formed (S1). Specifically, a predetermined electrostatic latent image for detecting misregistration is formed on the photoconductors 10Y, 10C, 10M, and 10K of each color shown in FIG. 3 by the same operation as in the normal image forming operation. The Then, the electrostatic latent image for detecting the misregistration of each color is developed by the same operation as that in the normal image forming operation, and becomes a toner image for detecting misregistration of each color. When these toner images are primarily transferred at positions shifted from each other on the intermediate transfer belt, the toner images of the respective colors become the position shift detection pattern images arranged in a predetermined pattern. Thereafter, along with the endless movement of the intermediate transfer belt, each toner image of the misregistration detection pattern image on the belt is detected by an optical sensor (not shown) (S2). Based on the detection timing of each toner image by the optical sensor 201, the control unit 200 of the printer grasps the relative positional deviation of each toner image. Based on the grasped result, the inclination amount of the main scanning line for other colors (Y, C, M) with respect to the main scanning line for black (K) that can minimize the amount of positional deviation of each toner image is calculated. (S3). Next, based on the calculation result, the tilt adjustment pulse motor (for example, 56Y) is rotated forward or reverse by a predetermined rotation angle (S4). When the tilt of the reflecting mirror is changed by this, the incident position of the writing light L with respect to the mirror surface is changed, so that the tilt of the main scanning line on the photosensitive member is changed. As a result, it is possible to correct the inclination of the scanning line generated before the adjustment.
Next, the rotation angle of the tilt adjusting pulse motor and the distance L from the fulcrum of the third reflecting mirror stored in the nonvolatile memory such as the RAM to the irradiation position of the writing light that is finally incident on the third reflecting mirror 46Y. Are used to calculate the magnification error in the main scanning line direction (S5), and the pixel clock frequency is corrected based on the calculated magnification error (S6). Further, the rotation angle of the tilt adjusting pulse motor and the distance L ′ from the fulcrum of the third reflecting mirror stored in the nonvolatile memory such as RAM to the irradiation position of the light beam first incident on the reflecting mirror are used. Then, the writing start position deviation is calculated (S7), and the irradiation start timing is corrected based on the calculation result (S8).

  Thus, in the present embodiment, after the tilt adjustment, the deviation of the writing start position caused by the tilt of the third reflecting mirror and the magnification error are calculated from the tilt amount of the third reflecting mirror and corrected. After the tilt adjustment, the tilt adjustment time can be shortened compared to the case where the detection mark is formed again to detect the magnification error and the deviation of the writing start position.

Further, it is preferable that the angle formed between the writing light to the third reflecting mirror 46Y and the writing light reflected by the third reflecting mirror 46Y is an obtuse angle.
In FIG. 11A, the third reflecting mirror 46Y is tilted by a predetermined angle when the angle between the writing light to the third reflecting mirror 46Y and the writing light reflected by the third reflecting mirror 46Y is an acute angle. It is a figure which shows the amount of inclination at the time. FIG. 12B shows a state where the third reflecting mirror is tilted by a predetermined angle when the angle formed between the writing light to the third reflecting mirror and the writing light reflected by the third reflecting mirror 46Y is an obtuse angle. It is a figure which shows the amount of inclination.
As can be seen from FIGS. 11A and 11B, when the same angle reflector is tilted, the inclination of the main scanning line on the photoconductor 10Y is larger when the obtuse angle is made than when the obtuse angle is made. I understand that. Therefore, when the third reflecting mirror is tilted to correct the tilt of the main scanning line on the photoconductor, the tilting angle of the third reflecting mirror 46Y is smaller when the obtuse angle is set than when the third reflecting mirror is tilted. . Therefore, after the inclination adjustment, it is possible to suppress the optical path length on the side opposite to the fulcrum (motor side) from being greatly different, and to suppress deterioration of the beam spot characteristics.

FIG. 12 is a diagram illustrating a tilt adjustment mechanism according to a modification.
As shown in the figure, in this modification, a fulcrum for tilting the third reflecting mirror 46Y is provided at the center in the longitudinal direction of the third reflecting mirror 46Y. As shown in the figure, the magnification error can be eliminated by setting the fulcrum of the third reflecting mirror 46Y at the center. This is because the optical path length is shortened from the center to the left side in the figure and the magnification in the main scanning line direction is reduced, whereas the right side in the figure is lengthened and the magnification in the main scanning direction is increased. As a result, the left and right magnification errors are offset across the center, and as a result, no magnification error occurs in the main scanning line.
Even if the central portion is used as a fulcrum, a deviation of the writing start position occurs. Therefore, as described above, the tilt angle and the fulcrum of the third reflecting mirror to the irradiation position of the light beam first incident on the third reflecting mirror. A deviation of the writing position is calculated from the distance L ′, and the writing start position is corrected based on the calculation result. At the center fulcrum, since the irradiation position of the light beam first incident on the third reflecting mirror is almost the end of the third reflecting mirror, L ′ is half of the longitudinal length l of the reflecting mirror ( It may be approximated to l / 2).

As described above, the optical scanning device according to the present embodiment includes a laser diode that is a light beam emitting unit, and a deflecting unit that includes a polygon motor and a polygon mirror that deflect writing light that is a light beam emitted from the laser diode in the main scanning direction. And a reflecting mirror for reflecting the writing light, and an inclination adjusting means for adjusting the inclination of the main scanning line on the surface of the photosensitive member as the scanning object by changing the posture of the reflecting mirror. Further, the control unit functions as a correction unit that corrects at least one of the writing start position and the main scanning line magnification error based on the amount of change in the posture of the reflecting mirror by the tilt adjustment unit.
With such a configuration, it is possible to correct the writing start position shift or the main scanning line magnification error after the inclination adjustment without forming a detection mark image. Therefore, the downtime of the apparatus at the time of tilt adjustment can be reduced.

  In addition, as shown in the modification, the tilt is adjusted by swinging one end of the third reflecting mirror in a direction perpendicular to the mirror surface of the third reflecting mirror, centering on the longitudinal center of the third reflecting mirror. With this configuration, a magnification error does not occur after the tilt adjustment, and only the writing start position deviation needs to be corrected after the tilt adjustment.

  In addition, accurate tilt adjustment can be performed by performing tilt adjustment using the tilt adjustment pulse motor 56 that is a motor capable of controlling the rotation angle.

  Further, the inclination of the main scanning line on the photosensitive member is adjusted by configuring the angle formed by the writing light incident on the third reflecting mirror and the light beam reflected by the third reflecting mirror to be an obtuse angle. Therefore, the amount by which the third reflecting mirror is tilted should be reduced as compared with the case where the angle formed between the writing light incident on the third reflecting mirror and the light beam reflected by the third reflecting mirror is an acute angle. Can do. Thereby, it is possible to suppress an increase in the optical path length after the tilt adjustment, and it is possible to suppress problems such as an increase in the beam spot diameter.

  Also equipped with multiple laser diodes, each light beam emitted from these laser diodes is individually deflected and reflected by different reflecting mirrors to scan different photoconductors, corresponding to each light beam A tilt adjusting means is provided on the reflecting mirror. As a result, the inclination of the main scanning line on each photoconductor can be corrected, and image misalignment when images formed on each photoconductor are superimposed can be suppressed.

  The optical writing unit, which is the optical scanning device of the present embodiment, includes a photoconductor that carries a Y-color toner image, a photoconductor that carries an M-color toner image, a photoconductor that carries a C-color toner image, K Write light is applied to each of the photoconductors carrying the color latent image. As a result, the optical writing unit can be used in a full-color image forming apparatus.

  In addition, the printer that is the image forming apparatus of the present embodiment can form a full-color image without color misregistration by including the above-described optical writing unit.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating an image forming station for Y in the printer. FIG. 2 is a schematic configuration diagram showing an optical writing unit in the printer together with four photosensitive members. The perspective view which shows the 3rd reflective mirror and its surrounding structure in the reflective optical system for Y of the same optical writing unit from the back surface side (non-mirror surface side) of a 3rd reflective mirror. The side view which shows the inclination adjustment pulse motor and inclination adjustment adjuster of the inclination adjustment means of the reflection optical system from the side. The top view which shows the motor holder and inclination adjustment adjuster of the inclination adjustment means. It is a figure explaining the main scanning line on a photoconductor when a 3rd reflective mirror is tilted. FIG. 3 is a control block diagram in the printer. The figure explaining calculation of a magnification error and calculation of a writing start position shift when a reflecting mirror is tilted. The control flow figure of inclination adjustment. (A) shows the amount of inclination when the third reflecting mirror is tilted by a predetermined angle when the angle formed between the writing light to the third reflecting mirror and the writing light reflected by the third reflecting mirror is an acute angle. FIG. (B) shows the amount of inclination when the third reflecting mirror is tilted by a predetermined angle when the angle formed between the writing light to the third reflecting mirror and the writing light reflected by the third reflecting mirror is an obtuse angle. FIG. The figure which shows the inclination adjustment mechanism of a modification.

Explanation of symbols

4: Optical writing unit 5: Intermediate transfer unit 10Y, C, M, K: Photoconductor 12Y, C, M, K: Developing device 20: Intermediate transfer belt 41a, b: Polygon mirror 44Y, C, M, K: First reflecting mirror 45Y, C, M, K: Second reflecting mirror 46Y, C, M, K: Third reflecting mirror 52Y: Holder 54Y: Bundling hardware 56Y: Tilt adjusting pulse motor 57Y: Motor holder 58Y: Tilt adjusting adjuster

Claims (7)

Light beam launching means;
Deflecting means for deflecting the light beam emitted from the light beam emitting means in the main scanning direction;
A reflecting mirror for reflecting the light beam;
In an optical scanning device comprising: an inclination adjusting means for adjusting an inclination of a main scanning line on a surface of a scanning object by changing an attitude of the reflecting mirror, and optically scanning the scanning object with the light beam;
An optical scanning apparatus comprising: a correcting unit that corrects at least one of a writing start position and a main scanning line magnification error based on a change amount of the posture of the reflecting mirror by the tilt adjusting unit. The optical scanning device according to claim 1.
The tilt adjusting means is configured to adjust the tilt by swinging one end of the reflecting mirror in a direction orthogonal to the mirror surface of the reflecting mirror with the central portion in the longitudinal direction of the reflecting mirror as a center. An optical scanning device. The optical scanning device according to claim 1 or 2,
An optical scanning device characterized in that the tilt adjusting means has a motor capable of controlling a rotation angle, and is configured to adjust the tilt of the main scanning line by controlling the rotation angle of the motor. The optical scanning device according to any one of claims 1 to 3,
An optical scanning device characterized in that an angle formed by a light beam incident on the reflecting mirror and a light beam reflected by the reflecting mirror is an obtuse angle. In the optical scanning device in any one of Claims 1 thru | or 4,
A plurality of the light beam emitting means are provided, and the light beams emitted from these light beam emitting means are individually deflected by the deflecting means and reflected by different reflecting mirrors so as to optically scan different scanning objects. Configure
An optical scanning device characterized in that the tilt adjusting means is provided in a reflecting mirror corresponding to each light beam. The optical scanning device according to claim 5.
Each scanning object includes a latent image carrier that carries a Y-color toner image, a latent image carrier that carries a M-color toner image, a latent image carrier that carries a C-color toner image, and a K-color latent image. An optical scanning device characterized by being a latent image carrier that carries an image. A plurality of photoconductors, an optical scanning unit that individually scans the photoconductors to form a latent image on the surface thereof, and a plurality of development units that individually develop the latent images formed on the photoconductors. In the image forming apparatus, the image forming apparatus includes a transfer unit that transfers the visible image obtained on each photosensitive member by development on the transfer member.
An image forming apparatus using the optical scanning device according to claim 5 or 6 as the optical scanning means.

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