JP4569212B2 - Color image forming apparatus - Google Patents

Description

  The present invention is suitable for use in a color printer having a multi-beam exposure function capable of forming a color image on a predetermined sheet at a high speed, the same facsimile machine, the same digital copying machine, and a complex machine thereof. The present invention relates to an image forming apparatus.

  In recent years, tandem type color printers, color copiers, and multi-function machines of these are often used. These color image forming apparatuses include an image writing unit for each of yellow (Y), magenta (M), cyan (C), and black (BK), a developing unit, a photosensitive drum, an intermediate transfer belt, and a fixing unit. And a device.

  For example, an image writing unit for Y color draws an electrostatic latent image on the photosensitive drum based on the image data for Y color. The developing means forms a color toner image by attaching Y color toner to the electrostatic latent image drawn on the photosensitive drum. The photosensitive drum transfers the toner image to the intermediate transfer belt. Similar processing is performed for the other M, C, and BK colors. The color toner image transferred to the intermediate transfer belt is transferred to a sheet and then fixed by a fixing device.

  According to this type of color image forming apparatus, in order to maintain the optimum color image forming quality, color misregistration between the Y, M, C, and BK colors that reproduce the R, G, and B colors of the original image. It is essential to correct the image forming means so as not to occur (hereinafter referred to as color misregistration correction mode). Color misregistration generally occurs due to assembly tolerances of the writing unit and the photosensitive drum. Further, it is considered that the exposure means and the support portion such as the photosensitive drum expand and contract due to a change in the outside air temperature due to a change in the outside air temperature or continuous use, causing a positional shift over time, which is considered to be caused by this.

  Regarding the above-described color misregistration correction mode, a registration mark formed on the intermediate transfer belt or the conveyance material transfer belt is detected by a color misregistration detection detecting means (hereinafter referred to as a resist sensor) such as a reflective sensor, and a certain reference color The shift amounts of main scanning, sub-scanning, lateral magnification, and skew related to the registration marks of other colors are calculated, and the color shift is corrected by adjusting the image formation timing and the like. As described above, in a color copying machine or the like having a plurality of image forming units, it is necessary to perform color misregistration correction in the sub-scanning direction, which is one of color misregistration amounts, with high accuracy.

  In connection with this type of image writing unit, Patent Document 1 discloses a laser printer registration apparatus. According to this laser printer registration apparatus, a PLL control means for performing PLL control on the rotational speed of the rotating polyhedron, a signal generating means for supplying a reference frequency signal to the PLL control means, a laser beam is received and a horizontal synchronization signal is generated. A plurality of synchronization sensors to output, and based on a horizontal synchronization signal output from one synchronization sensor and a reference frequency signal supplied from the signal generation means, a difference in horizontal synchronization signal output timing between other synchronization sensors is measured. The phase of the reference frequency signal is adjusted based on the horizontal synchronization signal output timing difference measured here, and the adjusted reference frequency signal is supplied to the PLL control means. By configuring the laser printer registration apparatus in this way, the phase shift due to the rotating polyhedron can be finely adjusted within the pixel unit distance, and the main scanning line shift on the photosensitive drum due to the laser beam can be set to the minimum. That's it.

  Patent Document 2 discloses a laser beam scanning device. According to this laser beam scanning device, a time difference between a light beam detection signal corresponding to a reference polygon mirror and a light beam detection signal corresponding to the remaining polygon mirror is calculated, and phase control data based on the time difference is calculated. Rotational phase control means for generating a rotational frequency by comparing with phase control data corresponding to a reference polygon mirror is provided. By providing such a rotational phase control means, the direction of the mirror surface of the polygon mirror can be easily controlled.

Japanese Patent Laid-Open No. 01-073369 (page 4, FIG. 1) Japanese Unexamined Patent Publication No. 09-230273 (5th page, FIG. 1)

  Incidentally, the color image forming apparatus according to the conventional example has the following problems.

  i. In recent years, high-speed print output is required, and the conventional polygon mirror writing system has a limitation in the rotational speed of the polygon motor, so multiple lines can be written simultaneously in one scan. Multi-beam laser sources are being considered. When trying to cope with speeding up using multi-beams, it is not possible to correct color misregistration with high accuracy by simply applying the laser printer registration apparatus of Patent Document 1 and the laser beam scanning apparatus of Patent Document 2. .

  ii. In particular, in multi-beams, variations in the gap amount between laser beams are involved in color misregistration accuracy. Therefore, when the color misregistration correction mode is executed, the laser light source in which image information for color misregistration correction is written on the line matches the laser light source in which image information for color image formation is written on the line when the normal image forming mode is executed. If not, there is a risk that variations in the gap amount between the laser beams appear as uneven colors.

  Accordingly, the present invention solves the above-described problems, and is a color that can realize color misregistration correction with high accuracy even in a tandem type color copier or the like in which a plurality of image forming units having multi-beams are arranged. An object is to provide an image forming apparatus.

In order to solve the above-mentioned problems, a color image forming apparatus according to the present invention scans a plurality of exposure beams based on color image information on an image carrier for each color, and simultaneously writes a plurality of lines in one scan. In the image forming apparatus, an image of each color including a reference color for color misregistration correction is formed on the image carrier, the image for color misregistration correction is transferred to the image transfer body, and an image passing timing on the image transfer body is determined. Scanning, calculating the amount of misregistration of another color image with respect to the reference color image, and correcting the image forming position based on the amount of misregistration is set as a color misregistration correction mode. Based on the information, each color image is formed, the image for color image formation is transferred to an image transfer body, and an operation for forming a color image in which each color is superimposed on the image transfer body is set as a normal image formation mode. when the image bearing member A plurality of image forming units that form toner images of a predetermined color and an image transfer body that transfers toner images formed on a plurality of image carriers, and based on the color misregistration correction mode or the normal image forming mode. A sub-scanning signal for each color is generated by an image forming unit that forms a color image on an image carrier, and a sub-scanning timing setting value and a sub-scanning effective period setting value set in each of the image forming units, and the sub-scanning based on the enable signal and a control means for controlling the input and output of image information, each of the image forming unit includes a polygon mirror for scanning a plurality of exposure beams emitted from the light source are scanned by the polygon mirror a beam detection means among the plurality of exposure beams by detecting a scanning light by any one light source to output a main scanning reference signal of the image forming unit that, the beam detection Based on the main scanning reference signal output from the stage it has a light source control section for controlling the output of the image information to be written to the light source, a signal obtained by the tip detection of paper to be fed to the pre-Symbol image forming means when the first image tip timing signal, the control means latches the image tip timing signal in the main scanning reference signal of the image forming units for colors as a reference among the image forming units of several create a second images tip timing signal, and sets the sub-scanning timing setting value 2 line units to be exposed by said detected positional deviation amount based on one scan in the color shift correction mode, and, The sub-scanning effective period setting value is set according to the image size to be output, and the control means performs the second image leading edge timing both when the color misregistration correction mode and the normal image forming mode are executed . The sub-scanning effective signal is generated by counting the main scanning reference signal for each color from the scanning signal as a base point, and a rising signal of the sub-scanning effective signal is generated, and the surface of the polygon mirror based on the rising signal is generated. It is characterized by correcting a color misregistration amount of one scan or less by phase control .

The color image forming apparatus according to the present invention includes control means for controlling input / output of an image forming means having an image carrier and a plurality of light sources for each color. In the case of forming a color image on the image carrier based on the color misregistration correction mode or the normal image forming mode, a plurality of exposure beams based on color image information are scanned on the image carrier for each color. When simultaneously writing a plurality of lines in one scan, the control unit generates a sub-scan signal for each color based on the sub-scan timing setting value and the sub-scan effective period setting value set in each of the image forming units. Input / output of image information is controlled based on the valid signal. In each of the image forming units, a plurality of exposure beams emitted from the light source is scanned by the polygon mirror. The beam detector detects scanning light from any one of the plurality of exposure beams scanned by the polygon mirror and outputs a main scanning reference signal of the image forming unit . The light source control unit controls the output of image information written to the light source based on the main scanning reference signal output from the beam detection unit. On the assumption of this, the control means, the second images tip timing signal latches the image tip timing signal in the main scanning reference signal of the image forming units for color as a reference of the image forming units of several Create The control unit sets the sub-scan timing setting value in units of two lines exposed in one scan based on the positional deviation amount detected in the color misregistration correction mode , and the sub-scan effective period according to the output image size Set the setting value. When color shift complement Seimo over de runtime and normal image formation mode execution, both control means, a sub-scanning effective signal by counting the main scanning reference signal for each color of the second image tip timing signals as a base point And generating a rising signal of the sub-scanning effective signal, and correcting the color misregistration amount of one scanning or less by the surface phase control of the polygon mirror based on the rising signal. With this correction, when the color misregistration correction mode based on each sub-scanning area signal is executed, a light source in which image information for color misregistration correction is written to the line, and an image for color image formation on the line when the normal image forming mode is executed. a light source for writing information becomes coincident.

  Therefore, the combination of the light sources when executing the color misregistration correction mode and the combination of the light sources when executing the normal image forming mode can be made the same. In addition, the light source for each color can be adjusted to the same line in the color misregistration correction mode and the normal image forming mode.

According to the color image forming apparatus of the present invention, when a plurality of exposure beams based on color image information are scanned on the image carrier for each color and a plurality of lines are simultaneously written in one scan, the control unit includes: When the color misregistration correction mode and the normal image forming mode are executed , the sub-scanning effective signal is generated by counting the main scanning reference signal for each color from the second image leading edge timing signal as a base point , and the sub-scanning effective signal is generated. A rising signal of the scanning effective signal is generated, and the color misregistration amount for one scanning or less is corrected by the surface phase control of the polygon mirror based on the rising signal .

With this configuration, when executing the color misregistration correction mode based on each sub-scanning region signal and when executing the normal image forming mode, both the light source in which image information for color misregistration correction is written on the line and the normal image forming mode are executed. Since each image forming unit can be controlled to match the light source for writing image information for color image formation on the line , the combination of the light source when executing the color misregistration correction mode and the time when executing the normal image formation mode The combination of light sources can be the same. Accordingly, the light source for each color can be adjusted to the same line in the color misregistration correction mode and the normal image forming mode. As a result, a highly accurate color misregistration correction mode can be executed even in a tandem type color copier having a multi-beam without being affected by gap variation between light sources.

  A color image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing a configuration example of a color copying machine 100 as an embodiment of the present invention.

  A color copying machine 100 shown in FIG. 1 is an example of a color image forming apparatus, and scans a plurality of laser beams (exposure beams) onto a photosensitive drum (image carrier) for each color based on color image information. The photosensitive drum is a device for simultaneously writing a plurality of lines in one scan. In addition to the color copying machine 100, the color image forming apparatus according to the present invention may be applied to a color printer, a facsimile machine, a complex machine of these, and the like.

  The color copying machine 100 includes a copying machine main body 101 and an image reading device 102. An image reading device 102 including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the copying machine main body 101. The document 11 placed on the document table of the automatic document feeder 201 is conveyed by a conveying unit, and an image of one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device 202 to reflect the document image. Incident light is read by the line image sensor CCD.

  The analog image signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in image processing means (not shown), and becomes digital image data Din. The image data Din is converted into image data Dy, Dm, Dc, Dk for Y, M, C, BK colors, and then image writing units (exposure means) 3Y, 3M, 3C, constituting the image forming means 60. Sent to 3K.

  The automatic document feeder 201 described above reads the contents of a large number of documents 11 fed from the document placement table all at once, and stores the document contents in a storage means (electronic RDH function). ). This electronic RDH function is conveniently used when copying the contents of a large number of originals with the copy function or when transmitting a large number of originals 11 with the facsimile function.

  The copying machine main body 101 is called a tandem type color image forming apparatus. The image forming means 60 includes a plurality of sets of image forming units (image forming systems) 10Y, 10M, 10C, and 10K each having an image forming body for each color, an endless intermediate transfer belt (image transfer body) 6, and a refeed. A sheet feeding / conveying unit including a sheet mechanism (ADU mechanism) and a fixing device 17 for fixing a toner image are provided. The paper feeding unit 20 is provided below the image forming system. The sheet feeding means 20 is composed of, for example, three sheet feeding cassettes 20A, 20B, and 20C. The paper P fed out from the paper supply unit 20 is conveyed under the image forming unit 10K.

  The image forming units 10Y, 10M, 10C, and 10K constitute an image forming unit 60, and have photosensitive drums 1Y, 1M, 1C, and 1K for each color. Each of the image forming units 10Y, 10M, 10C, and 10K is provided with a plurality of laser light sources and polygon mirrors, and irradiates the photosensitive drums 1Y, 1M, 1C, and 1K with the plurality of laser beams, and the photosensitive drum 1Y. , 1M, 1C, 1K, etc., so as to form a toner image of a predetermined color. The intermediate transfer belt 6 operates so as to transfer toner images formed on the plurality of photosensitive drums 1Y, 1M, 1C, and 1K.

  The image forming units 10Y, 10M, 10C, and 10K form color images on the photosensitive drums 1Y, 1M, 1C, and 1K based on the color misregistration correction mode and the normal image forming mode. Here, in the color misregistration correction mode, an image of each color including a reference color for color misregistration correction is formed on the photosensitive drums 1Y, 1M, 1C, and 1K, and the image for color misregistration correction is transferred to the intermediate transfer belt 6 ( Image transfer body), reading the passage timing of the image on the intermediate transfer belt 6, calculating the amount of misregistration of the other color image with respect to the reference color image, and correcting the image forming position based on the amount of misregistration. The operation to do.

  In the normal image forming mode, each color image is formed on the photosensitive drums 1Y, 1M, 1C, and 1K based on image information for color image formation, and the image for color image formation is formed on the intermediate transfer belt 6. This is an operation of transferring and forming a color image in which each color is superimposed on the intermediate transfer belt 6. For example, the image forming units 10Y, 10M, 10C, and 10K can color one side or both sides of the paper P based on a main scanning reference signal (laser index signal; hereinafter referred to as LDINDX signal) and a processing index signal (hereinafter referred to as processing INDEX signal). An image is formed.

  The image forming unit 10Y that forms a yellow (Y) image includes a photosensitive drum 1Y as an image forming body that forms a Y-color toner image, and a Y-color charging disposed around the photosensitive drum 1Y. Means 2Y, exposure means 3Y, developing means 4Y, and image forming body cleaning means 8Y. The exposure unit 3Y operates to irradiate the photosensitive drum 1Y with two laser beams Y # 1 and Y # 2 as an example of a plurality of exposure beams based on the image data Dy for Y color. This is because a Y-color electrostatic latent image for two lines is formed simultaneously.

  An image forming unit 10M that forms a magenta (M) color image includes a photosensitive drum 1M as an image forming body that forms an M toner image, an M color charging unit 2M, an exposure unit 3M, and a developing unit 4M. And an image forming member cleaning means 8M. The exposure unit 3M operates to irradiate the photosensitive drum 1M with two laser beams M # 1 and M # 2 as an example of a plurality of exposure beams based on the image data Dm for M color. This is because an electrostatic latent image for M color for two lines is formed simultaneously.

  An image forming unit 10C for forming a cyan (C) color image includes a photosensitive drum 1C as an image forming body for forming a C toner image, a charging unit 2C for C color, an exposure unit 3C, and a developing unit 4C. And an image forming member cleaning means 8C. The exposure unit 3C operates to irradiate the photosensitive drum 1C with two laser beams C # 1 and C # 2 as an example of a plurality of exposure beams based on the C color image data Dc. This is because a C-color electrostatic latent image for two lines is formed simultaneously.

  An image forming unit 10K that forms a black (BK) image includes a photosensitive drum 1K as an image forming body that forms a BK color toner image, a charging unit 2K, an exposure unit 3K, and a developing unit 4K for BK color. And an image forming member cleaning means 8K. The exposure unit 3K operates to irradiate the photosensitive drum 1K with two laser beams K # 1 and K # 2 as an example of a plurality of exposure beams based on the BK color image data Dk. This is because an electrostatic latent image for BK color for two lines is formed simultaneously.

  The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute a latent image forming unit. Development by the developing means 4Y, 4M, 4C, and 4K is performed by reversal development in which a developing bias in which an AC voltage is superimposed on a DC voltage having the same polarity (negative polarity in this embodiment) as the polarity of the toner used is applied . The intermediate transfer belt 6 is wound by a plurality of rollers and is rotatably supported. Each of the Y, M, C, and BK colors formed on each of the photosensitive drums 1Y, 1M, 1C, and 1K. A toner image is transferred.

  Here, an outline of the image forming process will be described below. Each color image formed by the image forming units 10 </ b> Y, 10 </ b> M, 10 </ b> C, and 10 </ b> K is subjected to primary transfer bias (not shown) having a polarity (positive polarity in this embodiment) opposite to the toner to be used. The rollers 7Y, 7M, 7C, and 7K are sequentially transferred (primary transfer) onto the rotating intermediate transfer belt 6 to form a synthesized color image (color image: color toner image). The color image is transferred from the intermediate transfer belt 6 to the paper P.

  The paper P accommodated in the paper cassettes 20A, 20B, and 20C is fed by the feed roller 21 and the paper feed roller 22A provided in the paper cassettes 20A, 20B, and 20C, respectively, and the transport rollers 22B, 22C, 22D, After passing through the registration roller 23 and the like, the sheet is conveyed to the secondary transfer roller 7A, and the color image is collectively transferred to one surface (front surface) on the paper P (secondary transfer). In this example, a paper leading edge detection sensor 80 is disposed near the registration roller 23 so as to detect the leading edge of the paper P.

  The paper P on which the color image has been transferred is fixed by the fixing device 17, is sandwiched between the paper discharge rollers 24, and is placed on a paper discharge tray 25 outside the apparatus. The transfer residual toner remaining on the peripheral surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K after the transfer is cleaned by the image forming body cleaning units 8Y, 8M, 8C, and 8K, and enters the next image forming cycle.

  At the time of double-sided image formation, the paper P formed on one side (front surface) and discharged from the fixing device 17 is branched off from the sheet discharge path by the branching unit 26, and constitutes a sheet feeding and conveying unit. After passing through the circulation sheet passing path 27A, the front and back are reversed by a reversing conveyance path 27B which is a refeed mechanism (ADU mechanism), passes through the refeed conveyance section 27C, and merges at the sheet feeding roller 22D.

  The reversely conveyed sheet P is conveyed again to the secondary transfer roller 7A through the registration roller 23, and a color image (color toner image) is collectively transferred onto the other side (back side) of the sheet P. The paper P on which the color image has been transferred is fixed by the fixing device 17, is sandwiched between the paper discharge rollers 24, and is placed on a paper discharge tray 25 outside the apparatus.

  On the other hand, after the color image is transferred to the paper P by the secondary transfer roller 7A, the residual toner is removed by the intermediate transfer belt cleaning means 8A from the intermediate transfer belt 6 that has separated the curvature of the paper P.

The time of forming these images, 52.3~63.9kg / m ² (1000 sheets) as the paper P about thin and 64.0~81.4kg / m ² (1000 sheets) of approximately plain paper, 83 .0~130.0kg / m ² (1000 sheets) about cardboard and 150.0kg / m ² (1000 sheets) about super thick paper is used. The thickness of the paper P (paper thickness) is about 0.05 to 0.15 mm. The above-described copying machine main body 101 is provided with a registration sensor 12 as an example of an image detection unit, and detects images of each color including a reference color for color misregistration correction transferred to the intermediate transfer belt 6 and detects the reference. It operates to detect the amount of color deviation from the color. For example, the resist sensor 12 is provided in front of the cleaning unit 8A.

  Further, the copying machine main body 101 is provided with a control means 15 for controlling input / output of the image forming means 60. The control unit 15 includes a laser light source that writes image information for color misregistration correction on the line when the color misregistration correction mode is executed, and a laser light source that writes image information for color image forming on the line when the normal image forming mode is executed. The image forming means 60 is controlled so as to match.

  FIG. 2 is a block diagram illustrating a configuration example of an image forming system of the color copying machine 100. A color copying machine 100 shown in FIG. 2 is obtained by extracting the image forming units 10Y, 10M, 10C, and 10K shown in FIG.

  In FIG. 2, the color copying machine 100 includes four photosensitive drums 1Y, 1M, 1C, 1K, four image writing units (exposure means) 3Y, 3M, 3C, 3K, and four control units 15Y, 15M. , 15C, 15K, and four image processing units 70Y, 70M, 70C, and 70K constitute an image forming system.

  The Y color image processing unit 70Y inputs, for example, one page of Y color image data Dy and divides the image data into two lines of image data. A page memory (not shown) is provided in the image processing unit 70Y. The Y-color image data Dy for one page is developed, and the image data Dy divided for every two lines is sequentially read out.

  The control unit 15Y is connected to the Y color image processing unit 70Y, and executes control for writing the image data Dy to a memory provided in the image processing unit 70Y and reading the image data Dy from the memory. An image writing unit 3Y for Y color is connected to the image processing unit 70Y and the control unit 15Y. The image writing unit 3Y includes, for example, a latch unit 43Y, a laser control unit (hereinafter referred to as an LD control unit 46Y), a laser writing scanning system 9Y0 for Y color, laser driving units 9Y1, 9Y2, and PWM modulation units 9Y3 and 9Y4. Configured. The laser writing scanning system 9Y0 includes two laser light sources 31Y1 and 31Y2. Semiconductor laser diodes are used for the laser light sources 31Y1 and 31Y2.

  Similarly, the M color image processing unit 70M inputs, for example, one page of M color image data Dm and divides the image data into two lines of image data. A page memory (not shown) is provided in the image processing unit 70M, and the M color image data Dm for one page is developed, and the image data Dm divided every two lines is sequentially read out.

  The control unit 15M is connected to the M color image processing unit 70M, and executes control for writing the image data Dm to a memory provided in the image processing unit 70M and reading the image data Dm from the memory. An image writing unit 3M for M color is connected to the image processing unit 70M and the control unit 15M.

  The C color image processing unit 70C receives, for example, one page of C color image data Dc and divides the image data into two lines of image data. A page memory (not shown) is provided in the image processing unit 70C, and the C-color image data Dc for one page is developed, and the image data Dc divided every two lines is sequentially read out.

  The control unit 15C is connected to the C color image processing unit 70C, and executes control for writing the image data Dc to a memory provided in the image processing unit 70C and reading the image data Dc from the memory. An image writing unit 3C for C color is connected to the image processing unit 70C and the control unit 15C.

  The BK color image processing unit 7K inputs, for example, BK color image data Dk for one page and divides it into image data for two lines. A page memory (not shown) is provided in the image processing unit 70K, and the BK color image data Dk for one page is developed, and the image data Dk divided every two lines is sequentially read out.

  The control unit 15K is connected to the image processing unit 70K for BK color, and executes control for writing the image data Dk to a memory provided in the image processing unit 70K and reading the image data Dk from the memory. The image processing unit 70K and the control unit 15K are connected to an image writing unit 3K for BK color.

  FIG. 3 is a diagram illustrating an internal configuration example of the Y color image writing unit 3Y. The image writing unit 3Y for Y color shown in FIG. 3 is obtained by extracting the main part from FIG. 2, and includes, for example, a latch unit 43Y, an LD control unit 46Y, laser drive units 9Y1, 9Y2, and PWM modulation units 9Y3 and 9Y4. have.

  The latch unit 43Y is connected to the control unit 15Y, receives a reference index signal (hereinafter referred to as MST-IDX signal) from the control unit 15Y, latches the VTOP signal, and outputs the VTOP 'signal to the LD control unit 46Y. As the MST-IDX signal, a reference index signal generated by a reference unit, for example, the BK color image forming unit 10K is used. For example, in the case of a two-beam light source, the MST-IDX signal is composed of a pulse signal having a two-line cycle.

  A selector 44Y is provided in the LD control unit 46Y. An INDEX detector 41Y is connected to the selector 44Y. The selector 44Y receives the index selection signal Scy from the control unit 15Y, and turns on one of the two laser light sources 31Y1 and 31Y2 when scanning the INDEX detection unit 41Y based on the index selection signal Scy. To generate an INDEX signal. The INDEX detection unit 41Y is provided at a predetermined scanning position other than the normal image forming area of the Y color laser light sources 31Y1 and 31Y2, and outputs an LDINDEX signal to the LD control unit 46Y. A photodiode (light receiving element: PD) is used for the INDEX detection unit 41Y.

  The LD control unit 46Y is connected to the latch unit 43Y and the INDEX detection unit 41Y, and outputs, for example, image data Dy1 for odd line writing and image data Dy2 for even line writing based on the VTOP ′ signal and the LDINDEX signal. To work. In addition to reading control of the LD controller 46Y and the image data Dy1 and Dy2, a sub-scanning area signal (hereinafter referred to as SVV signal) and a main scanning area signal (hereinafter referred to as SHV signal) are generated based on the VTOP 'signal. The SVV signal and the SHV signal are supplied to a page memory or the like of the image processing unit 70Y.

  The PWM controller 9Y3 and the PWM modulator 9Y4 are connected to the LD controller 46Y. The PWM modulation unit 9Y3 receives the odd line writing image data Dy1 and performs pulse width modulation processing on the image data Dy1 to output a modulation signal Sy1. Similarly, the PWM modulation unit 9Y4 receives image data Dy2 for even line writing, performs pulse width modulation processing on the image data Dy2, and outputs a modulation signal Sy2.

  A laser drive unit 9Y1 is connected to the PWM modulation unit 9Y3. The laser drive unit 9Y1 receives the modulation signal Sy1 assigned to the odd lines, and generates a first laser drive signal S11 based on the modulation signal Sy1. A laser drive unit 9Y2 is connected to the PWM modulation unit 9Y4. The laser drive unit 9Y2 receives the modulation signal Sy2 assigned to the even lines, and generates a second laser drive signal S12 based on the modulation signal Sy2.

  A laser light source 31Y1 for Y # 1 is connected to the laser drive unit 9Y1, and a laser beam Y # 1 having a predetermined intensity is radiated based on a laser drive signal S11 having a predetermined pulse width after PWM modulation. The laser beam Y # 1 is scanned toward the photosensitive drum 1Y to write odd lines. A laser light source 31Y2 for Y # 2 is connected to the laser drive unit 9Y2, and a laser beam Y # 2 having a predetermined intensity is radiated based on the similarly processed laser drive signal S12. The laser beam Y # 2 is scanned toward the photosensitive drum 1Y to write even lines.

  FIG. 4 is a block diagram illustrating an internal configuration example of the LD control unit 46. The LD control unit 46 shown in FIG. 4 includes a memory FIFO # 1, a FIFO # 2, a processing INDEX generation unit 61, an SHV signal generation unit 62, a selector 63, a FIFO read control unit 64, and an SVV signal generation unit 65. Is done.

  The processing INDEX generator 61 is connected to the selector 44Y shown in FIG. 3, and generates a processing INDEX signal based on the LDINDEX signal. The processing INDEX generator 61 constitutes a main scanning counter, counts the LDINDEX signal, and outputs the processing INDEX signal when one line cycle is counted.

  The selector 44Y shown in FIG. 3 is connected to a FIFO read control unit 65 in addition to the processing INDEX generation unit 61, and generates a read permission signal (FIFO REN) based on the LDINDEX signal. This read permission signal is supplied to the memory FIFO # 1 and FIFO # 2. Each of FIFO # 1 and FIFO # 2 is provided with terminals for inputting data (Din), write reset (WRST), and write permission (WEN). Also, data (Dout), read reset (RRST), A read permission (REN) output terminal is provided.

  The processing INDEX generation unit 61 is connected to an SHV signal generation unit 62, and generates an SHV signal and a selector control signal (hereinafter referred to as a SELECT signal) based on the processing INDEX signal. A selector 63 is connected to the SHV signal generator 62, and the SHV signal is selected in units of one line based on the SELECT signal.

  Two memories FIFO # 1 and FIFO # 2 are connected to the selector 63. The FIFO # 1 operates to input the image data Dy based on the processing INDEX signal and the SHV signal, and to output the odd-numbered line image data Dy1 based on the LDINDEX signal and the read permission signal. The processing INDEX signal is supplied as a write reset signal in the memory FIFO # 1. The SHV signal is supplied as an odd line write permission signal. The LDINDEX signal is supplied as an odd line read reset signal in the memory FIFO # 1.

  The memory FIFO # 2 operates to input the image data Dy based on the processing INDEX signal and the SHV signal, and to output the even line image data Dy2 based on the LDINDEX signal and the read permission signal. The image data Dy is input to the Din terminal, the processing INDEX signal is input to the WRST terminal, and the SHV signal is input to the WEN terminal. The image data Dy2 is output from the Dout terminal, the LDINDEX signal is input to the RRST terminal, and the read permission signal is input to the REN terminal.

  The processing INDEX signal is supplied as a write reset signal in the memory FIFO # 2. The SHV signal is supplied as an even line write enable signal. The LDINDEX signal is supplied as an even line read reset signal in the memory FIFO # 2. A First In-First Out memory is used for the memories FIFO # 1 and FIFO # 2.

  The SVV signal generation unit 65 is connected to the selector 44Y and the latch unit 43Y shown in FIG. 3, respectively, and is based on the preset VV start timing setting value SS1 and VV period setting value SS2, the VTOP ′ signal, and the LDINDEX signal. To generate an SVV signal. A control unit 15Y is connected to the SVV signal generator 65, and the setting values SS1 and SS2 are set in units of two lines.

  An example of the internal configuration of each of the image writing units 3M, 3C, and 3K for M, C, and BK colors will be described with reference to FIGS. The control units 15M, 15C, and 15K, and the image processing units 70M, 70C, and 70K have the same configurations and functions as the Y-color image writing unit 3Y, the control unit 15Y, and the image processing unit 70Y. Is omitted.

  FIG. 5 is a block diagram illustrating a configuration example of the image writing unit 3Y for Y color. An image writing unit 3Y shown in FIG. 5 includes laser light sources 31Y1 and 31Y2, a collimator lens 32, an auxiliary lens 33, a polygon mirror 34, a polygon motor 35, an f (θ) lens 36, a CY1 lens 37 for mirror surface imaging, and a drum. It has a CY2 lens 38 for surface imaging, an INDEX detection unit 41Y, a polygon motor drive substrate 45, and laser drive units 9Y1 and 9Y2.

  The laser light source 31Y1 is connected to the Y color laser driving unit 9Y1. The modulation signal Sy from the PWM modulation unit 9Y3 is supplied to the laser drive unit 9Y1. The laser driver 9Y1 outputs a laser drive signal S11 having a predetermined pulse width after PWM modulation to the laser light source 31Y1. In the laser light source 31Y1, laser light is generated based on the laser drive signal S11. The laser light emitted from the laser light source 31Y1 is shaped into a predetermined laser beam Y # 1 by the collimator lens 32, the auxiliary lens 33, and the CY1 lens 37.

  In the laser light source 31Y2, laser light is generated based on the laser drive signal S12. The laser light emitted from the laser light source 31Y2 is shaped into a predetermined laser beam Y # 2 by the collimator lens 32, the auxiliary lens 33, and the CY1 lens 37.

  The INDEX detector 41Y is optically coupled by a polarization beam splitter (not shown) provided on the optical axis, detects the laser beam Y # 1 or Y # 2, and outputs an LDINDEX signal to the selector 44Y.

  These laser beams Y # 1, Y # 2 are deflected by the polygon mirror 34 in the main scanning direction. For example, a polygon motor 35 is attached to the polygon mirror 34. A polygon driving substrate 45 is connected to the polygon motor 35. Y polygon CLK is supplied to the polygon drive board 45 from the control means 15 shown in FIG. The polygon drive board 45 rotates the polygon motor 35 at a predetermined rotation speed based on the Y polygon CLK. The laser beams Y # 1 and Y # 2 deflected by the polygon mirror 34 are imaged toward the photosensitive drum 1Y by the f (θ) lens 36 and the CY2 lens 38. By this operation, an electrostatic latent image for Y color is formed on the photosensitive drum 1Y.

  The INDEX detection unit 41Y is an example of a beam detection unit, and detects an LDINDEX signal (reference signal) by detecting scanning light by the laser beam Y # 1 or Y # 2 scanned by the polygon mirror 34 provided for each color. Works to output. When one of these multi-beams Y # 1 or Y # 2 is scanned by the INDEX detection unit 41Y, either one of the laser light sources 31Y1 or 31Y2 is forcibly lit to generate an INDEX signal. The INDEX signal generated by lighting is used as the main scanning reference timing signal (LDINDX signal) of the image writing unit 3Y. The selection is performed by an index selection signal Scy supplied from the control unit 15Y.

6A to 6C are block diagrams supplementing a configuration example of the image writing units 3M, 3C, and 3K for M, C, and BK colors.
The image writing unit 3M illustrated in FIG. 6A includes, for example, a latch unit 43M, an LD control unit 46M, an M color laser writing scanning system 9M0, laser driving units 9M1, 9M2, and PWM modulation units 9M3 and 9M4. The Each laser writing scanning system 9M0 includes two laser light sources 31M1 and 3M2. Semiconductor laser diodes are used for the laser light sources 31M1 and 3M2.

  The latch unit 43M is connected to the control unit 15M, receives a reference index signal (hereinafter referred to as MST-IDX signal) from the control unit 15M, latches the VTOP signal, and outputs a VTOP ′ signal to the LD control unit 46M. As the MST-IDX signal, a reference index signal generated by a reference unit, for example, the BK color image forming unit 10K is used. For example, in the case of a two-beam light source, the MST-IDX signal is composed of a pulse signal having a two-line cycle.

  A selector 44M is provided inside the LD control unit 46M. An INDEX detector 41M is connected to the selector 44M. The selector 44M receives the index selection signal Scm from the control unit 15M, and turns on one of the two laser light sources 31M1 and 31M2 when scanning the INDEX detection unit 41M based on the index selection signal Scm. To generate an INDEX signal. The INDEX detection unit 41M is provided at a predetermined scanning position other than the normal image forming area of the M color laser light sources 31M1 and 31M2, and outputs an LDINDEX signal to the LD control unit 46M. A photodiode (light receiving element: PD) is used for the INDEX detection unit 41M.

  The LD control unit 46M is connected to the latch unit 43M and the INDEX detection unit 41M of the image writing unit 3M. Based on the VTOP ′ signal and the LDINDEX signal, for example, the image data Dm1 for odd line writing and the even line writing It operates to output the image data Dm2. The LD control unit 46M generates an SVV signal (sub-scanning area signal) and an SHV signal (main scanning area signal) based on the VTOP ′ signal in addition to the reading control of the image data Dm1 and Dm2. The SVV signal and the SHV signal are supplied to a page memory or the like of the image processing unit 70M.

  The PWM controller 9M3 and the PWM modulator 9M4 are connected to the LD controller 46M. The PWM modulation unit 9M3 inputs image data Dm1 for writing odd lines, performs pulse width modulation processing on the image data Dm1, and outputs a modulation signal Sm1. Similarly, the PWM modulation unit 9M4 receives the even line writing image data Dm2, and performs pulse width modulation processing on the image data Dm2 to output a modulation signal Sm2.

  A laser drive unit 9M1 is connected to the PWM modulation unit 9M3. The laser drive unit 9M1 receives the modulation signal Sm1 assigned to the odd number lines, and generates a laser drive signal S21 based on the modulation signal Sm1. A laser drive unit 9M2 is connected to the PWM modulation unit 9M4. The laser drive unit 9M2 receives the modulation signal Sm2 assigned to the even lines, and generates a laser drive signal S22 based on the modulation signal Sm2.

  The laser drive unit 9M1 is connected to a laser light source 31M1 for M # 1, and radiates a laser beam M # 1 having a predetermined intensity based on a laser drive signal S21 having a predetermined pulse width after PWM modulation. The laser beam M # 1 is scanned toward the photosensitive drum 1M to write odd lines. A laser light source 31M2 for M # 2 is connected to the laser driving unit 9M2, and a laser beam M # 2 having a predetermined intensity is radiated based on the similarly processed laser driving signal S22. The laser beam M # 2 is scanned toward the photosensitive drum 1M to write even lines.

  The image writing unit 3C shown in FIG. 6B includes, for example, a latch unit 43C, an LD control unit 46C, a laser writing scanning system 9C0 for C color, laser driving units 9C1 and 9C2, and PWM modulation units 9C3 and 9C4. The Each laser writing scanning system 9C0 includes two laser light sources 31C1 and 3C2. Semiconductor laser diodes are used for the laser light sources 31C1 and 3C2.

  The latch unit 43C is connected to the control unit 15C, receives a reference index signal (hereinafter referred to as an MST-IDX signal) from the control unit 15C, latches the VTOP signal, and outputs a VTOP ′ signal to the LD control unit 46C. For the MST-IDX signal, a reference index signal generated by the BK color image forming unit 10K is used.

  A selector 44C is provided in the LD controller 46C. An INDEX detection unit 41C is connected to the selector 44C. The selector 44C receives the index selection signal Scc from the control unit 15C, and turns on one of the two laser light sources 31C1 and 31C2 when scanning the INDEX detection unit 41C based on the index selection signal Scc. To generate an INDEX signal. The INDEX detection unit 41C is provided at a predetermined scanning position other than the normal image formation area of the C color laser light sources 31C1 and 31C2, and outputs an LDINDEX signal to the LD control unit 46C. A photodiode is used for the INDEX detection unit 41C.

  An LD control unit 46C is connected to the latch unit 43C and the INDEX detection unit 41C, and outputs, for example, image data Dc1 for odd line writing and image data Dc2 for even line writing based on the VTOP ′ signal and the LDINDEX signal. To work. The LD control unit 46C generates an SVV signal (sub-scanning region signal) and an SHV signal (main scanning region signal) based on the VTOP ′ signal in addition to the reading control of the image data Dc1 and Dc2. The SVV signal and the SHV signal are supplied to a page memory or the like of the image processing unit 70C.

  The PWM controller 9C3 and the PWM modulator 9C4 are connected to the LD controller 46C. The PWM modulation unit 9C3 receives the odd line writing image data Dc1, and applies pulse width modulation processing to the image data Dc1 to output a modulation signal Sc1. Similarly, the PWM modulation unit 9C4 receives even line writing image data Dc2, and performs pulse width modulation processing on the image data Dc2 to output a modulation signal Sc2.

  A laser drive unit 9C1 is connected to the PWM modulation unit 9C3. The laser drive unit 9C1 receives the modulation signal Sc1 assigned to the odd lines, and generates a laser drive signal S31 based on the modulation signal Sc1. A laser drive unit 9C2 is connected to the PWM modulation unit 9C4. The laser drive unit 9C2 receives the modulation signal Sc2 assigned to the even lines, and generates a laser drive signal S32 based on the modulation signal Sc2.

  A laser light source 31C1 for C # 1 is connected to the laser driver 9C1, and a laser beam C # 1 having a predetermined intensity is radiated based on a laser drive signal S31 having a predetermined pulse width after PWM modulation. The laser beam C # 1 is scanned toward the photosensitive drum 1C to write odd lines. A laser light source 31C2 for C # 2 is connected to the laser drive unit 9C2, and a laser beam C # 2 having a predetermined intensity is radiated based on the similarly processed laser drive signal S32. The laser beam C # 2 is scanned toward the photosensitive drum 1C to write even lines.

  The image writing unit 3K illustrated in FIG. 6C includes, for example, a latch unit 43K, an LD control unit 46K, a laser writing scanning system 9K0 for BK color, laser driving units 9K1 and 9K2, and PWM modulation units 9K3 and 9K4. The Each laser writing scanning system 9K0 includes two laser light sources 31K1 and 3K2. Semiconductor laser diodes are used for the laser light sources 31K1 and 3K2. The latch unit 43K is connected to the control unit 15K, receives a reference index signal (hereinafter referred to as MST-IDX signal) from the control unit 15K, latches the VTOP signal, and outputs the VTOP ′ signal to the LD control unit 46K.

  A selector 44K is provided in the LD controller 46K. The selector 44K is connected to the INDEX detection unit 41K. The selector 44K receives the index selection signal Sck from the control unit 15K, and turns on one of the two laser light sources 31K1 and 31K2 when scanning the INDEX detection unit 41K based on the index selection signal Sck. To generate an INDEX signal. The INDEX detection unit 41K is provided at a predetermined scanning position other than the normal image formation region of the BK color laser light sources 31K1 and 31K2, and outputs an LDINDEX signal to the LD control unit 46K. A photodiode is used for the INDEX detection unit 41K.

  An LD control unit 46K is connected to the latch unit 43K and the INDEX detection unit 41K, and outputs, for example, image data DK1 for odd line writing and image data DK2 for even line writing based on the VTOP ′ signal and the LDINDEX signal. To work. The LD control unit 46K generates an SVV signal (sub-scanning region signal) and an SHV signal (main scanning region signal) based on the VTOP ′ signal in addition to the reading control of the image data DK1 and DK2. The SVV signal and the SHV signal are supplied to a page memory or the like of the image processing unit 70K.

  The PWM controller 9K3 and the PWM modulator 9K4 are connected to the LD controller 46K. The PWM modulation unit 9K3 receives image data Dk1 for writing odd lines, performs pulse width modulation processing on the image data Dk1, and outputs a modulation signal Sk1. Similarly, image data Dk2 for even-numbered line writing is input to PWM modulation section 9K4, and image data Dk2 is subjected to pulse width modulation processing to output modulation signal SK2.

  A laser drive unit 9K1 is connected to the PWM modulation unit 9K3. The laser drive unit 9K1 receives the modulation signal Sk1 assigned to the odd number lines, and generates a laser drive signal S41 based on the modulation signal Sk1. A laser drive unit 9K2 is connected to the PWM modulation unit 9K4. The laser drive unit 9K2 receives the modulation signal Sk2 assigned to the even lines, and generates a laser drive signal S42 based on the modulation signal Sk2.

  A laser light source 31K1 for K # 1 is connected to the laser driver 9K1, and radiates a laser beam K # 1 having a predetermined intensity based on a laser drive signal S21 having a predetermined pulse width after PWM modulation. The laser beam K # 1 is scanned toward the photosensitive drum 1K to write odd lines. A laser light source 31K2 for K # 2 is connected to the laser drive unit 9K2, and a laser beam K # 2 having a predetermined intensity is radiated based on the similarly processed laser drive signal S22. The laser beam K # 2 is scanned toward the photosensitive drum 1K to write even lines.

  FIG. 7 is a block diagram illustrating a configuration example of a control system in the color copying machine 100. The color copying machine 100 shown in FIG. 7 includes a control unit 15, which includes a registration sensor 12, an image memory 16, a sheet feeding unit 20, an image forming unit 60, an image processing unit 70, and a paper front The detection sensor 80 and the image reading apparatus 102 are connected.

  In addition to the Y, M, C, and BK color control units 15Y, 15M, 15C, and 15K shown in FIG. 2, the control means 15 includes a CPU (Central Processing Unit) 55, ROM (Read Only memory (RAM) 56 and random access memory (RAM) 57 are included. The ROM 56 stores system program data for controlling the entire copying machine. The RAM 57 is used as a work memory, and for example, temporarily stores control commands and the like. When the power is turned on, the CPU 55 reads the system program data from the ROM 56 and starts the system, and controls the entire copying machine based on the operation data D31 from the operation means 14.

  For example, a GUI (Graphic User Interface) type operation panel 48 is connected to the control means 15. The operation panel 48 includes, for example, an operation unit 14 configured from a touch panel and a display unit 18 configured from a liquid crystal display panel. The operation means 14 is connected to the CPU 55 and is operated when selecting image forming conditions and the paper feed cassettes 20A to 20C. The display unit 18 is connected to the control unit 15 which is output to the CPU 55 as the operation data D31 in addition to the operation unit 14, and the image forming conditions set by the operation unit 14 and the paper cassette selection information are displayed. Based on D21, it operates to display a menu selection screen (not shown), image forming conditions, and the like.

  The image reading apparatus 102 stores image data R, G, B relating to R, G, B color components obtained by reading the document 11 in the image memory 16. The image processing unit 70 includes the image processing units 70Y, 70M, 70C, and 70K for the Y, M, C, and BK colors described in FIG. In addition to the image data R, G, and B read from the image memory 16, the image processing means 70 includes image data Dy, Dm, and Dc related to Y, M, C, and BK colors output from an external printer or the like. , Dk are input. Image data Dy, Dm, Dc, Dk are also temporarily stored in the image memory 16. The image forming unit 60 includes the image writing units 3Y, 3M, 3C, and 3K for the Y, M, C, and BK colors described in FIG.

  The image writing unit 3Y is connected to the image processing unit 70Y and the control unit 15, receives the odd line image data Dy1 and the even line image data Dy2 from the image processing unit 70Y, and receives the MST-IDX signal, VTOP from the control unit 15. A signal and an index selection signal Scy are input. The unit 3Y writes the odd-numbered line image data Dy1 and the even-numbered line image data Dy2 simultaneously based on the MST-IDX signal, the VTOP signal, and the index selection signal Scy.

  Similarly, the image writing unit 3M is connected to the image processing unit 70M and the control unit 15, and receives the odd line image data Dm1 and the even line image data Dm2 from the image processing unit 70M. An IDX signal, a VTOP signal, and an index selection signal Scm are input. The unit 3M is configured to simultaneously write the odd line image data Dm1 and the even line image data Dm2 based on the MST-IDX signal, the VTOP signal, and the index selection signal Scm.

  The image writing unit 3C is connected to the image processing unit 70C and the control unit 15, receives the odd line image data Dc1 and the even line image data Dc2 from the image processing unit 70C, and receives the MST-IDX signal, VTOP from the control unit 15. A signal and an index selection signal Scc are input. The unit 3C is configured to simultaneously write the odd line image data Dc1 and the even line image data Dc2 based on the MST-IDX signal, the VTOP signal, and the index selection signal Scc.

  The image writing unit 3K is connected to the image processing unit 70K and the control unit 15. The image writing unit 3K receives the odd line image data Dk1 and the even line image data Dk2 from the image processing unit 70K, and receives the MST-IDX signal, VTOP from the control unit 15. A signal and an index selection signal Sck are input. The unit 3K is configured to simultaneously write the odd line image data Dk1 and the even line image data Dk2 based on the MST-IDX signal, the VTOP signal, and the index selection signal Sck.

  A paper leading edge detection sensor 80 is connected to the control means 15 described above. The paper leading edge detection sensor 80 is disposed in the vicinity of the attachment of the registration roller 23 shown in FIG. 1, and detects the leading edge of the paper P to identify the arrival of the paper. The paper leading edge detection sensor 80 outputs a paper leading edge detection signal Stp to the control means 15. The control means 15 outputs a VTOP signal obtained by binarizing the paper leading edge detection signal Stp to each of the image writing units 3Y, 3M, 3C and 3K.

  Further, a registration sensor 12 is connected to the control unit 15 and formed on the photosensitive drums 1Y, 1M, 1C, and 1K in the image forming units 10Y, 10M, 10C, and 10K, and transferred to the intermediate transfer belt 6. Each color image (color misregistration detection mark) including a reference color for color misregistration correction is detected, and an operation is performed to detect a color misregistration amount from the reference color. The registration sensor 12 outputs a color misregistration position detection signal S2 to the control means 15. The control means 15 calculates a color misregistration amount from the color misregistration position detection signal S2 detected by the registration sensor 12, and the phase is shifted from the MAST-IDX signal (reference signal) by an amount based on the calculated amount. Thus, the phase of the drive clock signal of the polygon mirror 34 of the image writing units 3Y, 3M, 3C, 3K is controlled based on the LDINDEX signal.

  In this example, the control means 15 controls the input / output of the image writing units 3Y, 3M, 3C, 3K through the control units 15Y, 15M, 15C, 15K. For example, in the control unit 15Y, when the color misregistration correction mode is executed, the laser light source 31Y1 in which the image data Dy for color misregistration correction is written on the line, and image data Dy for color image formation on the line when the normal image forming mode is executed The image writing unit 3Y is controlled so as to coincide with the laser light source 31Y1 for writing. The same applies to the image writing units 3M, 3C, and 3K for other colors.

  For example, an INDEX signal generated by forcibly lighting one laser light source 31Y1 or 31Y2 of the two laser beams Y # 1 and Y # 2 during the scanning of the INDEX detection unit 41Y is used as the image writing unit. When the 3Y LDINDEX signal (main scanning reference signal) is used, the control means 15 receives the LDINDEX signal from the INDEX detection unit 41Y and becomes the reference of the four image writing units 3Y, 3M, 3C, 3K. For example, the VTOP signal (image leading edge timing signal) is latched by the LDINDEX signal of the image writing unit 3K for BK color, and VTOP ′ of the image writing units 3Y, 3M, 3C, 3K for Y, M, C, BK colors. A signal is generated, and the image writing unit 3Y is generated based on the VTOP ′ signal and the LDINDEX signal of each color. 3M, 3C, is made to 3K SVV signals create (sub-scanning area signal) (determination).

  The control unit 15 creates SVV signals of the image writing units 3Y, 3M, 3C, and 3K based on the LDINDEX signal of each color, and corrects the color shift amount of one scanning pitch or less by the surface phase control of the polygon mirror 34. In this phase control, a color misregistration amount equal to or less than one scanning pitch among the color misregistration detection amounts is calculated and corrected so as to eliminate this color misregistration amount.

  In addition to the image writing units 3Y, 3M, 3C, 3K, a communication means 19 is connected to the control means 15. The communication means 19 is connected to a communication line such as a LAN, and is used when communicating with an external computer or the like. When the color copying machine 100 is used as a printer, the communication means 19 is used to receive print data Din 'from an external computer in the print mode. The control unit 15 controls the image forming unit 60 so as to form an image based on the contents set by the operation panel 48 in the normal operation mode, or the print data Din ′ input from the outside is used as the image forming unit 60. To control image formation.

  Paper feed means 20 is connected to the control means 15 and controls the paper feed cassettes 20A, 20B and 20C based on the paper feed control signal Sf in the print mode. The paper feed control signal Sf is supplied from the control means 15 to the paper feed means 20. For example, the paper feeding unit 20 feeds the paper P from the paper feeding cassette 20A, 20B or 20C selected by the operation panel 48 and feeds it to the image forming unit 60. As the sheet feeding means 20, a feed roller (not shown), a motor for driving the sheet feeding roller, and the like, and a drive control IC for driving the motor are used.

  8A to 8J are time charts showing an operation example (part 1) of the Y color image writing unit 3Y shown in FIG. In this embodiment, an image forming unit 10Y for laser beams Y # 1 and Y # 2, an image forming unit 10M for laser beams M # 1 and M # 2, an image forming unit 10C for laser beams C # 1 and C # 2, and Even in the color tandem type copying machine 100 in which the image forming units 10K of the laser beams K # 1 and K # 2 are arranged, color misregistration correction can be realized with high accuracy.

  Therefore, when the color misregistration correction mode and the normal image forming mode are executed, for example, in the Y color image writing unit 3Y, the MST-IDX signal shown in FIG. 8A is output from the control unit 15Y to the latch unit 43Y. For the MST-IDX signal, a reference index signal generated by a reference unit, for example, the BK color image forming unit 10Y is used. The MST-IDX signal is composed of, for example, a pulse signal having a two-line cycle.

  The LDINDEX signal shown in FIG. 8B is generated by forcibly lighting one of the two selected laser light sources 31Y1 and 31Y2 when scanning the INDEX detector 41Y based on an index selection signal Scy (not shown). Is done. The LDINDEX signal is output to the LD control unit 46Y.

  The processing INDEX signal shown in FIG. 8C is a signal generated in the LD control unit shown in FIG. The VTOP signal shown in FIG. 8G is a signal obtained by binarizing the paper leading edge detection signal obtained from the paper leading edge detection sensor 80. The VTOP ′ signal shown in FIG. 8H is a signal obtained by latching the VTOP signal based on the MST-IDX signal shown in FIG. 8A. The SVV signal (sub-scanning area signal) shown in FIG. 8J is a signal that rises in synchronization with the LDINDEX signal shown in FIG. 8B and the processing INDEX signal shown in FIG. 8C. That is, the SVV signal is generated based on the VTOP ′ signal by the LD control unit 46Y.

  The SVV signal is generated by the SVV signal generation unit 65 based on the preset VV start timing setting value SS1 and VV valid period setting value SS2, the VTOP 'signal, and the LDINDEX signal. The setting values SS1 and SS2 are set in units of two lines from the control unit 15Y to the SVV signal generation unit 65, respectively. The SVV signal is supplied to the page memory of the image processing unit 70Y. The read data shown in FIG. 8D is image data Dy of the first line, the second line, the third line, the fourth line, etc., and is read from the image memory 16 or the image processing unit 70Y to the LD control unit 46Y. .

  The VTOP ′ signal described above is output from the latch unit 43Y to the LD control unit 46Y. Based on the VTOP ′ signal and the LDINDEX signal shown in FIG. 8H, the LD control unit 46Y outputs the image data Dy1 for odd line writing to the PWM modulation unit 9Y3, and PWM modulates the image data Dy2 for even line writing. It outputs to each part 9Y4. In the PWM modulation unit 9Y3, the image data Dy1 for writing odd lines is subjected to pulse width modulation processing to become a modulation signal Sy1. The modulation signal Sy1 is output from the PWM modulation unit 9Y3 to the laser driving unit 9Y1. In the PWM modulation section 9Y4, the even-line writing image data Dy2 is subjected to pulse width modulation processing to become a modulation signal Sy2. The modulation signal Sy2 is output from the PWM modulation unit 9Y4 to the laser driving unit 9Y2.

  In the laser drive unit 9Y1, a laser drive signal S11 is generated based on the modulation signal Sy1 assigned to the odd lines. The laser drive unit 9Y2 generates a laser drive signal S12 based on the modulation signal Sy2 assigned to the even lines. The laser light source 31Y1 for Y1 radiates a laser beam Y # 1 having a predetermined intensity based on a laser drive signal S11 having a predetermined pulse width after PWM modulation. LD1 shown in FIG. 8E is a laser light source 31Y1 of the image writing unit 3Y, and generates a laser beam Y # 1 based on image data Dy1 of odd lines, that is, the first line, the third line,. The laser beam Y # 1 is scanned toward the photosensitive drum 1Y to write odd lines.

  The laser light source 31Y2 for Y2 radiates a laser beam Y # 2 having a predetermined intensity based on the similarly processed laser drive signal S12. LD2 shown in FIG. 8F is a laser light source 31Y2 of the image writing unit 3Y, and generates a laser beam Y # 2 based on image data Dy2 of even lines, that is, the second line, the fourth line,. The laser beam Y # 2 is scanned toward the photosensitive drum 1Y to write even lines.

  Note that the V counter shown in FIG. 8I is a signal for monitoring the sub-scanning area. In addition to determining the generation timing of the SVV signal (sub-scanning area signal), this signal detects whether or not one page of the document has been written, for example. Further, one main scan is performed by the surface phase control of the polygon mirror 34 using the period (interval) between the rising time t1 of the VTOP ′ signal shown in FIG. 8H and the pulse output time t2 of the processing INDEX signal shown in FIG. 8C. The amount of color misregistration below the pitch is corrected.

  9A to 9N are time charts showing an operation example in the LD control unit 46 shown in FIG. 10A to 10G are operation examples (No. 2) of the image writing unit 3Y for Y color, and are operation examples in which the operation timing shown in FIG. 8 is shifted by one line.

  In this example, the SHV signal is selected in units of one line based on the SELECT signal, supplied to the memory FIFOs # 1 and # 2, and the odd-line image data Dy1 from the memory FIFO # 1 is PWM-modulated by the image writing unit 3Y. It is assumed that the data is output to the unit 9Y3, and the even-line image data Dy2 is output from the memory FIFO # 2 to the PWM modulation unit 9Y4.

  Under these operating conditions, the LDINDEX signal shown in FIG. 9A is a main scanning reference signal selected by the selector 44Y shown in FIG. 3, and is input to the processing INDEX generator 61. The main scanning counter shown in FIG. 9B functions as the processing INDEX generation unit 61, and is reset with the count value N. When the count value N / 2 is counted (one line period is reached), the processing INDEX signal shown in FIG. Is generated.

  The SHV signal (main scanning area signal) shown in FIG. 9D is generated by the SHV signal generation unit 62 based on the processing INDEX signal. The SHV signal is supplied to a page memory or the like of the image processing unit 70Y. The SHV signal generation unit 62 generates a SELECT signal shown in FIG. 9E based on the processing INDEX signal in addition to the SHV signal. The selector 63 selects the SHV signal for each line based on the SELECT signal. The SELECT signal selects the laser light source 31Y1 that writes the odd line image data Dy1 at a low level (hereinafter referred to as “L” level), and the even line image data Dy2 at a high level (hereinafter referred to as “H” level). The laser light source 31Y2 for writing is selected.

  The odd line write reset signal (FIFO # 1WREST) shown in FIG. 9F is a processing INDEX signal and is input to the WRST terminal of the memory FIFO # 1. The write enable signal (FIFO # 1WEN) for odd lines shown in FIG. 9G is a signal obtained by processing the SHV signal, and is input to the WEN terminal of the memory FIFO # 1 via the selector 63. The SHV signal indicates that the odd line writing is permitted at the “H” level, and write refusal is indicated at the “L” level.

  The even line write reset signal (FIFO # 2WREST) shown in FIG. 9H is a processing INDEX signal and is input to the WRST terminal of the memory FIFO # 2. The even line write enable signal (FIFO # 2WEN) shown in FIG. 9I is a signal obtained by processing the SHV signal, and is input to the WEN terminal of the memory FIFO # 2 via the selector 63. The SHV signal indicates that even line writing is permitted at the “H” level and write rejection is indicated at the “L” level.

  The read reset signal (FIFO RRSET) shown in FIG. 9J is an LDINDEX signal and is supplied to the memory FIFO # 1 and the FIFO # 2. The read permission signal (FIFO REN) illustrated in FIG. 9K is generated by the FIFO read control unit 65 based on the LDINDEX signal, and is supplied to the memory FIFO # 1 and the FIFO # 2.

  The read data shown in FIG. 9L is image data Dy of the first line, the second line, the third line, the fourth line, etc., and is read from the image memory 16 or the image processing unit 70Y to the LD control unit 46Y. . In the memory FIFO # 1 of the LD control unit 46Y, the image data Dy is input based on the processing INDEX signal and the SHV signal. The image data Dy is input to the Din terminal of the memory FIFO # 1. The odd-line image data Dy1 is output based on the LDINDEX signal and the read permission signal. The image data Dy1 is output from the Dout terminal of FIFO # 1. The LDINDEX signal is input to the RRST terminal of the memory FIFO # 1, and the read permission signal is input to the REN terminal.

  In the memory FIFO # 2, the image data Dy is input based on the processing INDEX signal and the SHV signal. The image data Dy is input to the Din terminal of the memory FIFO # 2. The even-line image data Dy2 is output based on the LDINDEX signal and the read permission signal. The image data Dy2 is output from the Dout terminal of the FIFO # 2, the LDINDEX signal is input to the RRST terminal of the memory FIFO # 2, and the read permission signal is input to the REN terminal.

  LD1 shown in FIG. 9M is a laser light source 31Y1 of the image writing unit 3Y, and generates a laser beam Y # 1 based on the image data Dy1 of odd lines, that is, the first line, the third line, etc. . 9N is a laser light source 31Y2 of the image writing unit 3Y, and generates a laser beam Y # 2 based on the image data Dy2 of even lines, that is, the second line, the fourth line,. .

  As described above, when the SVV signal rises in synchronization with the LDINDEX signal and the processing INDEX signal, the laser light sources 31Y1 and 31Y2 in which the image data Dy for color misregistration correction is written to the line when the color misregistration correction mode is executed. The image writing unit 3Y can be controlled so that the laser light sources 31Y1 and 31Y2 that write color image forming image data Dy on the line coincide with each other when the normal image forming mode is executed. Then, the combination of the laser light sources 31Y1 and 31Y2 when executing the color misregistration correction mode can be matched with the combination of the laser light sources 31Y1 and 31Y2 when executing the normal image forming mode. At the same time, the laser light sources 31Y1 and 31Y2 for each color can be matched with the same line in the color misregistration correction mode and the normal image forming mode.

  For example, with respect to the operation time chart shown in FIG. 8, in the operation time chart shifted by one line as shown in FIG. 10, the laser light sources 31Y1, 31Y2 that shared the writing of the image data of odd lines as in the conventional method. However, it does not share the writing of the image data of even lines. That is, in the operation time chart shown in FIG. 8, the laser of the image writing unit 3Y that has generated the laser beam Y # 1 based on the image data Dy1 of the odd-numbered first line, the third line, etc. Even in the operation time chart in which the light source 31Y1 is shifted by one line as shown in FIG. 10, the laser beam Y # 1 is generated based on the image data Dy1 of odd lines such as the first line, the third line, etc. To come.

  As a result, even if the gap amount between the beams in the multi-beam light source varies with respect to the scanning pitch, the conditions before and after shifting by one line are equal, so that color misregistration and color unevenness due to gap amount variation do not appear. Thereby, the image formation quality can be maintained higher than that of the conventional method. Note that the image writing units 3M, 3C, and 3K for the M, C, and BK colors, the control units 15M, 15C, and 15K, and the image processing units 70M, 70C, and 70K are also used for the Y color image writing unit 3Y. The same operation is performed by controlling in the same manner as the control unit 15Y and the image processing unit 70Y, but the description thereof is omitted.

  FIG. 11 is a perspective view showing an example of registration mark CR detection by the two registration sensors 12A and 12B. The registration sensors 12A and 12B shown in FIG. 11 are in front of the image forming body cleaning means 8A shown in FIG. 1 and are images of respective colors including reference colors for color misregistration correction formed on the left and right sides of the intermediate transfer belt 6. (Hereinafter referred to as registration marks CR) are arranged at positions where they can be detected. The registration sensors 12A and 12B detect the registration mark CR and output a color registration position detection signal (hereinafter simply referred to as a position detection signal) S2 in the color registration correction mode. This position detection signal S2 is used, for example, to detect a color shift amount from the BK color.

  FIG. 12 is a diagram showing an example of forming a registration mark CR for color misregistration correction. The registration mark CR shown in FIG. 12 is formed when the color misregistration correction mode is executed. The image forming units 10Y, 10M, 10C, and 10K are controlled by the CPU 55 shown in FIG. 7 so that the registration mark CR for color misregistration correction is formed on the intermediate transfer belt 6.

  In this example, four “B” -shaped BK registration marks CR for color misregistration correction are formed in succession on the left and right ends in the sub-scanning direction, which is the moving direction of the intermediate transfer belt 6. The BK registration mark CR is simultaneously written on the photosensitive drum 1K by the laser beams K # 1 and K # 2. Subsequently, four C-color registration marks CR are continuously formed on the left and right ends. The C-color registration mark CR is simultaneously written on the photosensitive drum 1C by the laser beams C # 1 and C # 2.

  Further, four M-color registration marks CR are continuously formed on the left and right ends. The M-color registration mark CR is simultaneously written on the photosensitive drum 1M by the laser beams M # 1 and M # 2. Subsequently, four Y-color registration marks CR are successively formed on the left and right ends. The Y-color registration mark CR is simultaneously written on the photosensitive drum 1Y by the laser beams Y # 1 and Y # 2.

  The reason why the four registration marks CR of each color are formed at the left and right ends is to detect the image forming position of the registration mark CR of each color and correct it accurately. These registration marks CR for color misregistration correction are detected by the registration sensor 12A and the like, the color misregistration amount with respect to the image forming position of each color registration mark CR is calculated, and the Y, M, and C color image forming positions are corrected. This correction is for accurately superimposing color images based on desired image data Dy, Dm, Dc, Dk in the image forming system after execution of the color misregistration correction mode.

13A and 13B are diagrams illustrating an example of binarization of the position detection signal S2 by the registration sensor 12A or the like.
In FIG. 13A, the position detection signal S2 obtained by the registration sensor 12A or the like is binarized based on a preset threshold value Lth. In this example, the passing timing pulse signal Sp rises at the time ta when the point a at which the position detection signal S2 falls crosses the threshold value Lth, and the passing timing pulse at the time tb when the point b at which the position detection signal S2 rises crosses the threshold value Lth. The signal Sp falls. The passage timing pulse signal Sp is binarized and becomes position detection data Dp. The position detection data Dp is used to calculate the shift amount of the Y, M, and C color write positions with respect to the write position of the BK registration mark CR.

FIG. 14 is a diagram showing an example of the relationship between the registration mark CR for color misregistration correction and the registration sensor 12A.
The registration mark CR for color misregistration correction shown in FIG. 14 includes a line segment parallel to the main scanning direction and a line segment having an angle of θ = 45 ° with respect to the main scanning direction. In this example, an auxiliary line parallel to the sub-scanning direction is drawn from the center point c of the line segment parallel to the main scanning direction, and a point where this auxiliary line intersects with this 45 ° angle line segment. When d, the length of the line segment between the points cd is defined as Lb. In this example, the registration sensor CR of the registration mark CR for color misregistration correction is calculated by calculating the length Lb of the line segment between the points cd from the detection time difference between the points c and d of the registration mark CR. It is possible to detect the positional relationship in the main scanning direction with respect to these detection points.

  FIG. 15 is a diagram illustrating a calculation example of the color misregistration correction amount in the color misregistration correction mode. In this example, the color misregistration correction amount is calculated on the basis of the BK color registration mark CR in order to adjust the writing position of the Y, M, and C color registration marks CR to match the BK color registration mark CR. The For example, for the C color writing position adjustment, the writing position of the BK color registration mark CR and the writing position of the C color registration mark CR are detected, and the deviation amount of the C color writing position from the Bk color is calculated. The correction amount is obtained.

Here, the time when the registration sensor 12A shown in FIG. 15 detects the linear portion of the leftmost BK registration mark CR in the main scanning direction is T11, and the time when the sensor 12A detects the inclined portion of the registration mark CR. Let T12 be the jumping distance between the detection locus line Lo of the sensor 12A and one end of the BK registration mark CR at the left end, and A1 and one end of the detection locus line Lo of the sensor 12A and the C registration mark CR at the left end. Is set to A2, the main scanning coarse adjustment value [1]
[1] = A2-A1 = T12-T11 (1)
Is calculated by

Further, the time when the registration sensor 12A detects the linear portion of the left C registration mark CR in the main scanning direction is T13, and the left BK registration mark CR and the left C registration mark CR in the sub-scanning direction. The sub-scanning fine adjustment value [2] is expressed by Equation (2), that is, when the separation distance (reference value) B1 between
[2] = 2240−B1 = 2240 (T13−T11) (2)
Is calculated by However, the numerical value “2240” is a design value of the separation distance between the Bk color and the C color. The actual distance varies depending on how to shift.

Also, the time when the left side C-colored registration mark CR is detected by the registration sensor 12A is T14, and the registration sensor 12B shown in FIG. 15 is a straight line in the main scanning direction of the right-side BK registration mark CR. The time when the sensor 12B is detected is T21, the time when the sensor 12B detects the inclined portion of the registration mark CR is T22, and the sensor 12B detects the straight portion of the right C registration mark CR in the main scanning direction. Let T23 be the time, and T24 be the time when the sensor 12B has detected the inclined portion of the registration mark CR, and the jumping distance from the detection locus line Lo of the registration sensor 12B to one end of the right BK registration mark CR is A3. And the jumping distance from the detection locus line Lo of the sensor 12B to the one end of the C-color registration mark CR on the right side is A4. The separation distance (reference value) between the detection locus line Lo of the registration sensor 12A and the detection locus line Lo of the registration sensor 12B is C1, and the detection locus line Lo of the registration sensor 12A and the detection locus line Lo of the registration sensor 12B When the separation distance (reference value) between is set to C2, the overall lateral magnification adjustment value [3] in the main scanning direction is expressed by equation (3), that is,
[3] = C2-C1
= (2360-A3 + A1)-(2360-A4 + A2)
= (A1-A3)-(A2-A4)
= [(T12-T11)-(T22-T21)]-[(T14-T13)-
(T24-T23)] (3)
Is calculated by However, the design value of the separation distance between the left and right BK registration marks CR is, for example, 2360 dots.

Further, the amount of misregistration (unknown) between the left BK registration mark CR and the right BK registration mark CR in the sub-scanning direction is D1, and the left C-color registration mark CR in the sub-scanning direction is When the amount of misalignment (unknown) between the C-color registration mark CR on the right side is D2, the skew adjustment value [4] is expressed by equation (4), that is,
[4] = D2-D1
= (T13-T23)-(T11-T21) (4)
Is calculated by

  Similarly, regarding the other M and Y color writing position adjustments, the amount of deviation between the writing position of the BK color registration mark CR and the writing position of the M or Y color registration mark CR is detected. Each correction amount is calculated from the amount. Thereafter, the C, M, and Y color image forming positions other than the BK color image forming unit 10K are adjusted.

  Next, an operation example of the color copying machine 100 will be described. FIG. 16 is a flowchart showing an example of image formation (main routine) in the color copying machine 100 as an embodiment, and FIG. 17 is a flowchart showing an example of image processing (subroutine).

  In this embodiment, the image writing unit 3Y having the photosensitive drums 1Y, 1M, 1C, and 1K and the two laser light sources 31Y1 and 31Y2 for each color, and the image writing having the laser light sources 31M1 and 31M2 in the same manner. A unit 3M, an image writing unit 3C having laser light sources 31C1 and 31C2, and an image writing unit 3K having laser light sources 31K1 and 31K2 are provided with control means 15 for input / output control. Laser light sources 31Y1, 31Y2, etc. in which image data Dy for color misregistration correction is written in the line, and laser light sources 31Y1, 31Y2, etc. in which image data Dy for color image formation are written in the line when the normal image forming mode is executed. The image writing unit 3Y is controlled so as to match. The other image writing units 3M, 3C, 3K are similarly controlled.

  In this example, two laser beams Y # 1 and Y # 2 are scanned on the photosensitive drum 1Y based on the Y-color image data Dy1 and Dy2, and the two laser beams M # 1 and M # 2 are scanned. Is scanned on the photoconductor drum 1M based on the image data Dm1 and Dm2 for M color, and the two laser beams C # 1 and C # 2 are scanned on the photoconductor drum 1C for C color. Two laser beams K # 1 and K # 2 are scanned onto the photosensitive drum 1K for BK color. In the normal image forming mode, it is assumed that a color image in which colors are superimposed on the intermediate transfer belt 6 is formed. As for image information, a case where the image reading apparatus 102 reads and acquires a document will be described as an example.

  With this as an image forming condition, a color image forming request is waited at step A1 of the flowchart shown in FIG. If there is a color image formation request, the process proceeds to step A2, and the control unit 15 branches the control depending on the selection of the color misregistration correction mode or the normal image forming mode. When the color misregistration correction mode is selected, the process proceeds to step A3.

  In step A <b> 3, the CPU 55 controls the image forming units 10 </ b> Y, 10 </ b> M, 10 </ b> C, and 10 </ b> K so as to create a registration mark CR for color misregistration correction on the intermediate transfer belt 6. At this time, in the BK color image writing unit 3K, the laser beams K # 1 and K # 2 shown in FIG. 2 simultaneously write the BK color registration marks CR on the photosensitive drum 1K.

  In the C color image writing unit 3C, the C color registration mark CR is simultaneously written on the photosensitive drum 1C by the laser beams C # 1 and C # 2. In the M color image writing unit 3M, the M color registration mark CR is simultaneously written on the photosensitive drum 1M by the laser beams M # 1 and M # 2. The Y-color registration mark CR is simultaneously written on the photosensitive drum 1Y by the laser beams Y # 1 and Y # 2.

  Due to these writings, “F” -shaped BK registration marks CR for color misregistration correction as shown in FIG. 12 are continuously provided on the left and right ends in the sub-scanning direction, which is the moving direction of the intermediate transfer belt 6. Four pieces are formed. Subsequently, four C-color registration marks CR are formed on the intermediate transfer belt 6 in succession at the left and right ends. Further, four M-color registration marks CR are continuously formed on the left and right ends. Subsequently, four Y-color registration marks CR are successively formed on the left and right ends.

  In step A4, the registration sensors 12A and 12B detect registration marks CR for color misregistration correction. At this time, the registration sensor 12A and the like detect the registration mark CR and output a position detection signal S2 to the control means 15. The control means 15 binarizes the position detection signal S2 obtained by the registration sensor 12A or the like based on a preset threshold value Lth.

  In this example, the passing timing pulse signal Sp rises at the time ta when the point a at which the position detection signal S2 falls crosses the threshold Lth, and the passing timing pulse at the time tb when the point b at which the position detection signal S2 rises crosses the threshold Lth. The signal Sp falls. The passage timing pulse signal Sp is binarized and becomes position detection data Dp (see FIG. 13).

  In step A5, the control unit 15 calculates a color misregistration amount with respect to the image forming position of each color registration mark CR based on the position detection data Dp. In this example, the color misregistration correction amount is calculated on the basis of the BK color registration mark CR in order to adjust the writing position of the Y, M, and C color registration marks CR to match the BK color registration mark CR. The For example, for the C color writing position adjustment, the writing position of the BK registration mark CR and the writing position of the C registration mark CR are detected, and the deviation amount of the C color writing position with respect to the BK color is calculated. .

  According to the example shown in FIG. 15, the main scanning coarse adjustment value [1] is calculated from equation (1), the sub-scanning fine adjustment value [2] is calculated from equation (2), and the main scanning adjustment value [2] is calculated from equation (3). An overall lateral magnification adjustment value [3] in the scanning direction is calculated, and a skew adjustment value [4] is calculated from equation (4). Similarly, regarding the other M and Y color writing position adjustments, the amount of deviation between the writing position of the BK color registration mark CR and the writing position of the M or Y color registration mark CR is detected. Each correction amount is calculated from the amount.

  Thereafter, in step A6, the timing for writing out the image data Dy, Dm, Dc, etc. is corrected based on the color misregistration correction amount so as to adjust the C, M, Y color image forming positions other than the BK color image forming unit 10K. To do. This correction is for accurately superimposing color images based on desired image data Dy, Dm, Dc, Dk in the image forming system after execution of the color misregistration correction mode.

  Then, the process proceeds to step A11 to determine whether or not to end the image forming process. At this time, the control means 15 detects the power-off information or the like and determines the end. If the power-off information is not detected, the process returns to step A1 to wait for a color image formation request. If there is a color image formation request, the process proceeds to step A2.

  When the normal image forming mode is selected in the above step A2, the process proceeds to step A7 to input image forming conditions. The image forming conditions are input to the control unit 15 by the user using the operation panel 48. For example, a menu selection screen (not shown), image formation conditions, and the like are displayed on the display unit 18, and the user operates to instruct selection of the paper cassettes 20 </ b> A to 20 </ b> C and the like on this display screen. The image forming conditions, paper cassette selection information, and the like set by the operation unit 14 are output to the control unit 15 as operation data D31. Here, for example, the user sets the document 11 on the automatic document feeder 201.

  In step A8, the image reading apparatus 102 reads the document 11 automatically fed by the automatic document feeder 201 and outputs the image data Din to the image processing means 70. The image data Din is composed of RGB color image data obtained by reading the document 11. Note that the image data Din may be print data Din ′ captured from an external computer through the communication unit 19.

  Thereafter, in step A9, the control unit 15 controls the image processing unit 70 and the image forming units 10Y, 10M, 10C, and 10K so as to execute the image forming process. For example, the subroutine shown in FIG. 17 is called, and the image processing means 70 reads the image data Din relating to the RGB color of the document 11 from the image memory 16 in units of one page, for example, in step B1 of the flowchart. In step B2, the image processing unit 70 converts the image data Din relating to RGB color into the image data Dy relating to Y color, the image data Dm relating to M color, the image data Dc relating to C color, and the image data Dk relating to BK color. Respectively.

  Thereafter, in step B3, the control unit 15Y determines whether the image data Dy has been set in the image processing unit 70Y. At this time, the control unit 15Y detects, for example, an end flag (EOF) added to one page unit. When this end flag is detected, it is recognized that the image data Dy is set in the image processing unit 70Y. Accordingly, when the image data Dy is not set in the image processing unit 70Y, the process proceeds to step B4, and the control unit 15Y sets the image data Dy in the image processing unit 70Y.

  In step B5, the control unit 15M determines whether the image data Dm is set in the image processing unit 70M. At this time, the control unit 15M detects the end flag added to the page. When this end flag is detected, it is recognized that the image data Dm is set in the image processing unit 70M. Therefore, when the image data Dm is not set in the image processing unit 70M, the process proceeds to step B6, and the control unit 15M sets the image data Dm in the image processing unit 70M.

  Thereafter, the process proceeds to step B7, and the control unit 15C determines whether the image data Dc is set in the image processing unit 70C. At this time, the control unit 15C detects the end flag added to the page. When this end flag is detected, it is recognized that the image data Dc is set in the image processing unit 70C. Therefore, when the image data Dc is not set in the image processing unit 70C, the process proceeds to step B8, and the control unit 15C sets the image data Dc in the image processing unit 70C.

  In step B9, the control unit 15K determines whether the image data Dk is set in the image processing unit 70K. At this time, the control unit 15K detects the end flag added to the page. When this end flag is detected, it is recognized that the image data Dk is set in the image processing unit 70K. Therefore, when the image data Dk is not set in the image processing unit 70K, the process proceeds to step B10, and the control unit 15K sets the image data Dk in the image processing unit 70K.

  Thereafter, the process proceeds to step B11, and each control unit 15Y, 15M, 15C, 15K executes a laser writing process. For example, in the image writing unit 3Y for Y color, the MST-IDX signal shown in FIG. 8A is output from the control unit 15Y to the latch unit 43. For the MST-IDX signal, a reference index signal generated in the image forming unit 10Y for BK color is used.

  At this time, the INDEX detection unit 41Y outputs an LDINDEX signal obtained by detecting the Y color laser beam Y # 1 or Y # 2. The selector 44Y selects one laser light source 31Y1 or 31Y2 used for generating the LDINDEX signal based on the index selection signal Scy. The LDINDEX signal generated by the laser light source 31Y1 or 31Y2 selected here is output to the LD control unit 46Y shown in FIG. The LD control unit 46Y generates the processing INDEX signal shown in FIG. 8C based on the LDINDEX signal.

  Further, the paper leading edge detection signal Stp output from the paper leading edge detection sensor 80 is binarized by the control means 15 and becomes the VTOP signal shown in FIG. 8G. This VTOP signal is latched based on the MST-IDX signal shown in FIG. 8A, and becomes the VTOP ′ signal shown in FIG. 8H. The LD controller 46 described above generates the SVV signal (sub-scanning region signal) shown in FIG. 8J based on the VTOP ′ signal. The timing of the SVV signal is controlled so as to rise in synchronization with the LDINDEX signal shown in FIG. 8B and the processing INDEX signal shown in FIG. 8C.

  For example, the SVV signal is generated by the SVV signal generation unit 65 based on the preset VV start timing setting value SS1 and VV valid period setting value SS2, the VTOP 'signal, and the LDINDEX signal. The setting values SS1 and SS2 are set in units of two lines from the control unit 15Y to the SVV signal generation unit 65, respectively. The SVV signal is supplied to the page memory of the image processing unit 70Y.

  Then, read data (image data Dy) such as the first line, the second line, the third line, the fourth line,... Shown in FIG. 8D is read from the image processing unit 70Y to the LD control unit 46Y. At this time, the above VTOP ′ signal is output from the latch unit 43Y to the LD control unit 46Y. Based on the VTOP ′ signal and the LDINDEX signal shown in FIG. 8H, the LD control unit 46Y outputs the image data Dy1 for odd line writing to the PWM modulation unit 9Y3, and PWM modulates the image data Dy2 for even line writing. It outputs to each part 9Y4. In the PWM modulation unit 9Y3, the image data Dy1 for writing odd lines is subjected to pulse width modulation processing to become a modulation signal Sy1. The modulation signal Sy1 is output from the PWM modulation unit 9Y3 to the laser driving unit 9Y1. In the PWM modulation section 9Y4, the even-line writing image data Dy2 is subjected to pulse width modulation processing to become a modulation signal Sy2. The modulation signal Sy2 is output from the PWM modulation unit 9Y4 to the laser driving unit 9Y2.

  In the laser drive unit 9Y1, a laser drive signal S11 is generated based on the modulation signal Sy1 assigned to the odd lines. The laser drive unit 9Y2 generates a laser drive signal S12 based on the modulation signal Sy2 assigned to the even lines. The laser light source 31Y1 for Y # 1 radiates a laser beam Y # 1 having a predetermined intensity based on a laser drive signal S11 having a predetermined pulse width after PWM modulation. LD1 shown in FIG. 8E is a laser light source 31Y1 of the image writing unit 3Y, and generates a laser beam Y # 1 based on image data Dy1 of odd lines, that is, the first line, the third line,. . The laser beam Y # 1 is scanned toward the photosensitive drum 1Y to write odd lines.

  The laser light source 31Y2 for Y # 2 radiates a laser beam Y # 2 having a predetermined intensity based on the similarly processed laser drive signal S12. LD2 shown in FIG. 8F is a laser light source 31Y2 of the image writing unit 3Y, and generates a laser beam Y # 2 based on image data Dy2 of even lines, that is, the second line, the fourth line,. . The laser beam Y # 2 is scanned toward the photosensitive drum 1Y to write even lines.

  A laser beam Y # 1 emitted from the laser light source 31Y1 of the image writing unit 3Y is scanned in the main scanning direction on the photosensitive drum 1Y shown in FIG. 2, and image forming dots by this main scanning are applied to the photosensitive drum 1Y. As a result, an electrostatic latent image of odd-numbered lines for Y color is formed. Below this odd number of electrostatic latent images, the laser beam Y # 2 emitted from the laser light source 31Y2 is simultaneously scanned in the main scanning direction, and image forming dots by this main scanning are formed on the photosensitive drum 1Y. , An electrostatic latent image of even lines for Y color is formed. In this manner, two Y-color lines composed of image forming dots formed in the sub-scanning direction by the laser beams Y # 1 and Y # 2 are provided on the photosensitive drum 1Y in the main scanning direction. Formed simultaneously.

  The writing of the image data Dy in the sub-scanning area is monitored by the V counter shown in FIG. 8I. For example, it is detected whether one page of the document 11 has been written. Further, one main scan is performed by the surface phase control of the polygon mirror 34 using the period (interval) between the rising time t1 of the VTOP ′ signal shown in FIG. 8H and the pulse output time t2 of the processing INDEX signal shown in FIG. 8C. The amount of color misregistration below the pitch is corrected.

  A similar writing process is performed in the M, C, and BK color image forming units 10M, 10CM, and 10K other than the Y color image forming unit 10Y. As a result, for example, the image writing unit 3M simultaneously scans the photosensitive drum 1M with laser beams M # 1 and M # 2 in the main scanning direction, and image forming dots by this main scanning are applied to the photosensitive drum 1M. As a result, odd and even lines of electrostatic latent images for M color are formed. In this manner, two M-color lines composed of image forming dots formed in the sub-scanning direction by the laser beams M # 1 and M # 2 are provided on the photosensitive drum 1M in the main scanning direction. Formed simultaneously.

  Further, the laser beam C # 1 and C # 2 are simultaneously scanned in the main scanning direction by the image writing unit 3C on the photosensitive drum 1C for C color, and image forming dots by this main scanning are applied to the photosensitive drum 1C. As a result, an electrostatic latent image of odd and even lines for C color is formed. In this manner, two C-color lines composed of image forming dots formed in the sub-scanning direction by the laser beams C # 1 and C # 2 are provided on the photosensitive drum 1C in the main scanning direction. Formed simultaneously.

  Further, the laser beam K # 1 and K # 2 are simultaneously scanned in the main scanning direction by the image writing unit 3K on the photosensitive drum 1K for BK color, and image forming dots by this main scanning are applied to the photosensitive drum 1K. As a result, an electrostatic latent image of odd and even lines for BK color is formed. In this way, two BK color lines formed of image forming dots formed in the sub-scanning direction by the laser beams K # 1 and K # 2 are provided on the photosensitive drum 1K in the main scanning direction. Formed simultaneously.

  The image forming dots formed on the photosensitive drums 1Y to 4Y are developed by the developing units 4Y, 4M, 4C, and 4K. By this development, a YMCK toner image is obtained. Further, on the intermediate transfer belt 6 shown in FIG. 1, YMCK toner images formed side by side in the main scanning direction by the four photosensitive drums 1Y to 4Y are transferred to the intermediate transfer belt 6 (primary transfer). ).

  Then, the process returns to step A9 of the main routine. In step A10, the control unit 15 determines whether or not the page related to the color image formation is the last page. A final flag (EOF) added to the last page is detected. When this final flag is detected, the process proceeds to step A11. When the final flag is not detected, the process returns to step A9 to continue the above-described processing.

  When the color image related to the last page is formed, the process proceeds to step A11 to determine whether or not to end the image forming process. At this time, the control means 15 detects the power-off information or the like and determines the end. When the power-off information is not detected, the process returns to step A1 to continue the above-described processing. If the power-off information is detected, the image forming process is terminated.

  As described above, according to the color copying machine 100 as the embodiment, the control unit 15 forms a color image on the photosensitive drums 1Y, 1M, 1C, and 1K based on the color misregistration correction mode or the normal image forming mode. The photosensitive drum 1Y is scanned with two laser beams Y # 1 and Y # 2 based on the color image data Dy1 and Dy2, and the two laser beams M # based on the image data Dm1 and Dm2 are scanned. 1 and M # 2 are scanned on the photosensitive drum 1M, and two laser beams C # 1 and C # 2 based on the image data Dc1 and Dc2 are scanned on the photosensitive drum 1C, and the image data Dk1 and Dk2 are obtained. Control is performed so that the two laser beams K # 1 and K # 2 are scanned on the photosensitive drum 1K.

  When writing two lines for each color at the same time in such a scan, the control means 15 uses the laser light source 31Y1 that has written the image data Dy1 for color misregistration correction on the odd lines when the color misregistration correction mode is executed. When the normal image forming mode is executed, the image forming unit 10Y is controlled so as to coincide with the laser light source 31Y1 that writes the image data Dy1 for color image formation on the odd lines. The image forming units 10M, 10C, and 10K are similarly controlled for the other M, C, and BK colors.

  Therefore, a combination of the laser light sources 31Y1, 31Y2, 31M1, 31M2, 31C1, 31C2, 31K1, and 31K2 that share the odd and even lines in each of the image forming units 10Y, 10M, 10C, and 10K when the color misregistration correction mode is executed. The combinations of the laser light sources 31Y1, 31Y2, 31M1, 31M2, 31C1, 31C2, 31K1, and 31K2 when the normal image forming mode is executed can be made the same. Thereby, the laser light sources 31Y1, 31Y2, 31M1, 31M2, 31C1, 31C2, 31K1, and 31K2 for each color can be adjusted to the same line in the color misregistration correction mode and the normal image forming mode. In addition, compared to the conventional method, it is now possible to execute a highly accurate color misregistration correction mode even in color copiers equipped with a multi-beam exposure function without being affected by gap variations between laser light sources. .

  18A to 18J are operation examples (part 1) in the image writing unit 3Y as a comparative example, and FIGS. 19A to 19G are times showing operation examples (part 2) in which the operation timing shown in FIG. 18 is shifted by one line. It is a chart.

  According to this comparative example, the laser light source LD1 shown in FIG. 18E is responsible for writing even-numbered image data Dy2, and the laser light source LD2 shown in FIG. 18F is initialized so that writing of odd-numbered line image data Dy1 is shared. This is the case of a color copier. In the comparative example, the V counter shown in FIG. 18I that monitors the sub-scanning area counts the processing INDEX signal. The SVV signal (sub-scanning area signal) shown in FIG. 18J is raised based only on the processing INDEX signal. Surface phase control of the polygon mirror 34 is performed in a period (interval) between the rise time t1 of the MST-IDX signal and the rise time t2 'of the processing INDEX signal.

  With the image writing unit 3Y of the comparative example initialized as described above, when the operation is shifted by one line as shown in FIGS. 19A to 19G with respect to the operation time charts shown in FIGS. The laser light source LD2 that shares the writing of the image data of the odd lines shown in FIG. 18F is changed to the sharing of the image data of the even lines as shown in FIG. 19E. Conversely, a phenomenon occurs in which the laser light source LD1 that shares writing of even-numbered image data shown in FIG. 18E changes to sharing of writing odd-numbered image data as shown in FIG. 19D.

  On the other hand, in the method of the present invention, the laser light source LD1 shown in FIG. 8E shares writing of the odd-numbered line image data Dy1, and the laser light source LD2 shown in FIG. 8F shares writing of the even-numbered line image data Dy2. This is the case of the color copying machine 100 that is initialized as described above. In the method of the present invention, the V counter shown in FIG. 8I that monitors the sub-scanning area counts the LDINDEX signal. The SVV signal shown in FIG. 8J is raised in synchronization with both the LDINDEX signal and the processing INDEX signal. The surface phase of the polygon mirror 34 is controlled during a period (interval) between the rise time t1 of the MST-IDX signal and the rise time t2 of the processing INDEX signal.

  In the image writing unit 3Y according to the present invention initialized as described above, when the operation is shifted by one line as shown in FIG. 10 with respect to the operation time chart shown in FIG. As shown in FIG. 10D, the laser light source LD1 sharing the writing of the odd line image data shown in FIG. 10 maintains the sharing of writing the odd line image data as it is. Further, the laser light source LD2 that shares writing of even-numbered image data shown in FIG. 8F also maintains sharing of writing even-numbered image data as shown in FIG. 10E.

  FIGS. 20A and 20B are conceptual diagrams showing examples of influence (no deviation) on the gap between beams and the registration mark in the image writing unit 3Y, and FIGS. 21A and 21B are conceptual diagrams showing examples of such influence (with deviation).

  In FIGS. 20A and 20B, white circles are, for example, image formation dots in which image data is written by the laser light source LD1 at a resolution of 600 dpi and one line at an interval of 42 μm, and a registration mark CR as shown in FIG. 14 is formed. To do. Black (hatched) circles are image forming dots in which image data is written by the laser light source LD2 under similar image forming conditions. When the gaps between the laser light sources LD1 and LD2 are aligned as shown in FIG. 20A, the laser light sources LD1 and LD2 that share the writing of image data of odd lines are exchanged as shown in FIG. 20B. However, it has no effect on the registration mark.

  On the other hand, when the gap between the laser light sources LD1 and LD2 is slightly shifted as shown in FIG. 21A, as shown in FIG. 21B, the laser light sources LD1 and LD2 that share the writing of the image data of the odd lines, Is switched, the registration mark CR is shifted by an amount corresponding to the gap amount deviating from the ideal value (gε = 0). As a result, color unevenness proportional to the gap amount gε is generated. This gap amount gε becomes a finite value due to manufacturing variations.

  That is, according to the method of the present invention, as shown in FIGS. 8B and 8C, the VV signal shown in FIG. 8J is raised in synchronization with both the LDINDEX signal and the processing INDEX signal. The laser light source LD1 that has shared writing does not share writing of image data for even lines. Further, the laser light source LD2 that has shared the writing of the image data of the even lines is not shared with the writing of the image data of the odd lines. Therefore, there is a variation in the gap amount between the laser light sources, and even if there is a shift of one line, the front and rear conditions are the same, so color unevenness due to the gap amount variation shown in FIG. 21B does not appear. As a result, the image forming quality can be maintained higher than that of the conventional method.

  The present invention is suitable for application to a color printer having a multi-beam exposure function capable of forming a color image of a predetermined sheet at high speed, the same facsimile machine, the same digital copying machine, and a complex machine thereof. .

1 is a conceptual diagram illustrating a configuration example of a color copying machine 100 as an embodiment of the present invention. 2 is a block diagram illustrating a configuration example of an image forming system of the color copying machine 100. FIG. It is a figure which shows the internal structural example of the image writing unit 3Y for Y color. It is a block diagram which shows the internal structural example of LD control part 46Y. It is a block diagram which shows the structural example of the scanning system of the image writing unit 3Y for Y color. (A)-(C) is a block diagram which supplements the structural example of the image writing unit 3M, 3C, 3K for M, C, and BK colors. 2 is a block diagram illustrating a configuration example of a control system in the color copying machine 100. FIG. (A)-(J) are time charts which show the operation example (the 1) in the image writing unit 3Y for Y color shown in FIG. (A)-(N) are time charts which show the operation example in LD control part 46Y shown in FIG. (A)-(G) is a time chart which shows the operation example (the 2) in the image writing unit 3Y for Y color. It is a perspective view showing an example of detection of registration mark CR by two registration sensors 12A and 12B. It is a figure which shows the example of formation of the registration mark CR for color misregistration correction. (A) And (B) is a figure which shows the binarization example of position detection signal S2 by 12 A of registration sensors. It is a figure which shows the example of a relationship between the registration mark CR for color misregistration correction, and the registration sensor 12A. It is a figure which shows the example of calculation of the color shift correction amount in the color shift correction mode. 3 is a flowchart showing an example of image formation (main routine) in the color copying machine 100 as an embodiment. 3 is a flowchart showing an example of image processing (subroutine) in the color copying machine 100. (A)-(J) is a time chart which shows the operation example (the 1) in the image writing unit 3Y as a comparative example. (A)-(G) are time charts which show the operation example (the 2) in the image writing unit 3Y. (A) and (B) are conceptual diagrams showing an example of influence (no deviation) on the gap between beams and the registration mark in the image writing unit 3Y. (A) and (B) are conceptual diagrams showing an example of an influence (with deviation) on the gap between beams and the registration mark in the image writing unit 3Y.

Explanation of symbols

1Y, 1M, 1C, 1K Photosensitive drum (image carrier)
3Y, 3M, 3C, 3K Image writing unit (image forming means)
4Y, 4M, 4C, 4K Developing means 6 Intermediate transfer belt 10Y, 10M, 10C, 10K Image forming unit (image forming means)
12, 12A, 12B Registration sensor (image detection means)
14 Operation means 15 Control means 15Y, 15M, 15C, 15K Control unit 16 Image memory 18 Display means
19 Communication means 31Y1, 31Y2, 31M1, 31M2, 31C1, 31C2, 31K1, 31K2 Laser light source 48 Operation panel (display means + operation means)
55 CPU (control means)
60 Image forming means 70 Image processing means 80 Paper leading edge detection sensor (beam detection means)
DESCRIPTION OF SYMBOLS 100 Color copier 101 Copier main body 102 Image reading apparatus 201 Automatic document feeder 202 Document image scanning exposure apparatus

Claims (2)

In a color image forming apparatus in which a plurality of exposure beams based on color image information are scanned on an image carrier for each color, and a plurality of lines are simultaneously written on the image carrier in one scan.
An image of each color including a reference color for color misregistration correction is formed on the image carrier, the image for color misregistration correction is transferred to the image transfer member, and the passage timing of the image on the image transfer member is read to An operation for calculating the position shift amount of another color image with respect to the color image and correcting the image forming position based on the position shift amount is set as a color shift correction mode.
A color image in which an image of each color is formed on the image carrier based on image information for color imaging, the image for color imaging is transferred to an image transfer body, and the respective colors are superimposed on the image transfer body When the normal image forming mode is set to
A plurality of image forming units that form toner images of a predetermined color on the image carrier, and an image transfer body that transfers toner images formed on the plurality of image carriers; Image forming means for forming a color image on the image carrier based on the image mode;
A sub-scanning effective signal for each color is generated based on a sub-scanning timing setting value and a sub-scanning effective period setting value set in each of the image forming units, and input / output of image information is controlled based on the sub-scanning effective signal. Control means,
Each of the image forming units includes:
A polygon mirror for scanning a plurality of exposure beams emitted from the light source,
Beam detecting means for detecting scanning light from any one of the plurality of exposure beams scanned by the polygon mirror and outputting a main scanning reference signal of the image forming unit ;
Have a light source control section for controlling the output of the image information to be written to the light source based on the main scanning reference signal output from the beam detecting means,
When a signal obtained by the tip detection of paper to be fed to the pre-Symbol image forming means to the first image tip timing signal,
The control means includes
Create a second images tip timing signal by latching the image tip timing signal in the main scanning reference signal of the image forming units for colors as a reference among the image forming units of multiple,
The sub-scan timing setting value is set in units of two lines that are exposed in one scan based on the positional deviation amount detected in the color misregistration correction mode, and the sub-scan effective period is set according to the output image size. Set the setting value,
When the color shift correction mode execution and normal image formation mode execution, both
The control means includes
Generating the sub-scanning effective signal by counting the main scanning reference signal for each color with the second image leading edge timing signal as a base point, and generating a rising signal of the sub-scanning effective signal;
A color image forming apparatus, wherein a color shift amount of one scan or less is corrected by surface phase control of the polygon mirror based on the rising signal . In the surface phase control of the previous SL polygon mirror,
2. The color image forming apparatus according to claim 1, wherein a phase of a driving clock signal of the polygon mirror is controlled .

Images