JP2004347999A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove the adverse effects of displacement between image reference positions specified in advance and color image information writing positions for detecting corresponding image reference positions, and to accurately form register marks CR based upon a color shift correction mode in the image reference positions. <P>SOLUTION: The image forming apparatus includes: image forming units 10Y, 10M, 10C, and 10K in which the image reference positions for writing pieces of image information on photoreceptor drums 1Y, 1M, 1C, and 1K and forming color images on an intermediate transfer belt 6 are specified in advance; a register mark sensor 12 that detects color images formed on the intermediate transfer belt 6 by the image forming units 10Y, 10M, 10C, and 10K; and a control means 15 that detects the positions of the color images for detecting the image reference positions with the register mark sensor 12, and corrects the image reference positions on the basis of the pieces of positional information of the color images for detecting the image reference positions detected by the register mark sensor 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and an image forming method suitable for use in a tandem type color printer or copying machine having an intermediate transfer belt or a transfer material conveying belt, or a composite machine thereof.
[0002]
[Prior art]
In recent years, image forming apparatuses such as color digital copiers and color printers have been often installed in companies, schools, convenience stores, various medical institutions and public institutions. In this color digital copying machine, a color image is formed based on image data of red (R), green (G), and blue (B) colors obtained from a colored original image. Image data is received from an external device such as a computer (hereinafter simply referred to as a personal computer), and a color image is formed based on the image data.
[0003]
According to this type of image forming apparatus, in order to maintain optimum color image forming quality, yellow (Y), magenta (M), and cyan (C) for reproducing R, G, and B colors of a document image are used. ), It is essential to correct the image forming means so as not to cause a color shift between black (Bk) colors (hereinafter referred to as a color shift correction mode). Regarding the color misregistration correction mode at this time, a registration mark formed on the intermediate transfer belt or the transfer material transfer belt is detected by a color misregistration detecting means (hereinafter, referred to as a “registration sensor”) such as a reflection-type sensor. The shift amount of each of the main scan, the sub-scan, the lateral magnification, and the skew of the other color with respect to the color is calculated, and the color shift is corrected by adjusting the image forming timing and the like.
[0004]
Patent Document 1 discloses an electrophotographic image forming apparatus applicable to a laser beam copying machine and a facsimile machine. According to this image forming apparatus, a correction unit is provided for exposing the image carrier to form a high-quality image. In the correction means, among the registration mark images transferred from each image carrier to the carrier, detection timing of the registration mark image transferred to the carrier from the image carrier located at the most downstream side in the carrier transport direction, A relative difference from the detection timing of each of the remaining registration mark images is detected.
[0005]
Based on the relative difference, the correction unit individually corrects the irradiation start position of the light beam to each of the remaining image carriers, the irradiation angle of the light beam to the image carriers, and the optical path length of the light beam. Is made. In other words, according to Patent Document 1, registration marks of each color are formed on a carrier, a registration sensor detects the passage timing of the registration marks, and calculates a misregistration amount of another color with respect to a reference color to correct an image forming position. It is made to do.
[0006]
[Patent Document 1]
JP-A-01-142681 (page 13, FIG. 4)
[0007]
[Problems to be solved by the invention]
By the way, according to the color misregistration correction mode according to the conventional example, there are the following problems.
{Circle around (1)} In the manufacturing process of the apparatus main body including the image forming apparatus according to Patent Document 1, when the image forming unit and the registration sensor are assembled for the first time, or after the apparatus main body is sold, the writing unit, the registration sensor, the intermediate transfer, and the like. In the initial color misregistration correction mode in a case where the belt, the transfer material conveyance belt, and the like are replaced, a registration mark image is created on a conveyance body or the like with the correction amount being “0”. However, there is a possibility that the image forming position including the reference color is shifted due to an assembly tolerance at the time of mounting the image writing unit, the registration sensor, and the like.
[0008]
{Circle around (2)} Therefore, the mark detection area of the registration sensor for detecting color misregistration is reduced, and there is a possibility that a registration mark image may deviate from the sensor detection area.
[0009]
{Circle around (3)} Because of this, it is difficult to accurately detect the registration mark image, so that it is impossible to accurately form a reference mark registration mark image or the like based on the color misregistration correction mode at a predetermined image forming position. As a result, it becomes a cause of hindering improvement in image formation quality in color superimposition processing based on arbitrary image data.
[0010]
In view of the above, the present invention has been made to solve the above-described problem of the conventional example, and has an image forming apparatus capable of accurately forming a reference mark image of a reference color based on a color misregistration correction mode at a predetermined image forming position. And an image forming method.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problem, an image forming apparatus according to the present invention forms a reference color image for color misregistration correction on an image forming body, reads a passage timing of the reference color image, and performs another processing for the reference color image. In an image forming apparatus that calculates a position shift amount of a color image and corrects an image forming position, the image forming apparatus includes an image forming body, and an image reference position for writing image information to the image forming body to form a color image is determined. A predetermined image forming means, an image detecting means for detecting a color image formed on the image forming body by the image forming means, and writing of color image information for detecting an image reference position on the image forming body, An image is formed, the position of the color image for detecting the image reference position formed on the image forming body is detected, and the image reference position is corrected based on the detected position information of the color image for detecting the image reference position. Control means It is characterized in.
[0012]
According to the image forming apparatus of the present invention, when a color image based on image information for an arbitrary color is formed on an image forming body, an image reference position is defined in advance in the image forming unit, A color image is formed by writing image information at the image reference position. In the image detecting means, a color image formed on the image forming body by the image forming means is detected. Based on this premise, the control means writes all color image information for image reference position detection on the image forming body by the image forming means to form all color images, and detects the image reference position formed on the image forming body. The position of the color image for image detection is detected by the image detecting means, and the image reference position is corrected based on the position information of the color image for image reference position detection detected by the image detecting means.
[0013]
Therefore, an operation for removing the influence of a positional shift between a predetermined image reference position in the image forming unit and a writing position of image information of each color for detecting the image reference position formed by the image forming unit is performed. Therefore, it is possible to execute the accurate color misregistration correction mode in the image forming system after executing the image reference position correction mode. Accordingly, in the manufacturing process of the apparatus main body, when the image forming means and the image detecting means are assembled for the first time, or when the image forming body is replaced after the sale of the apparatus main body, the image reference position of the image forming means is changed. Thus, a reference color image for color misregistration correction can be formed with high accuracy.
[0014]
An image forming method according to the present invention is a method of forming a color image based on image information for an arbitrary color on an image forming body, forming a reference color image for color misregistration correction on the image forming body, and An operation of reading the passage timing of the color image, calculating the amount of misregistration of the other color image with respect to the reference color image, and correcting the image forming position is referred to as a color misregistration correction mode. The color image information is written to form all the color images, the position of the color image for detecting the image reference position formed on the image forming body is detected, and the detected position of the color image for detecting the image reference position is detected. When the operation of correcting the image reference position based on the information is the image reference position correction mode, the image reference position correction mode is executed before the color misregistration correction mode is executed.
[0015]
According to the image forming method of the present invention, when a color image based on image information for an arbitrary color is formed on an image forming body, a predetermined image reference position in the image forming unit and a predetermined image forming position are formed by the image forming unit. It is possible to remove the positional deviation from the written position of the image information of each color for detecting the image reference position.
[0016]
Therefore, the accurate color misregistration correction mode can be executed in the image forming system after the execution of the image reference position correction mode. As a result, a color image based on image information for an arbitrary color can be formed in an image forming system in which color misregistration has been accurately corrected.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of an image forming apparatus and an image forming method according to the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing a configuration example of a color image forming apparatus 100 as an embodiment according to the present invention.
In this embodiment, all the color images are formed by writing the image information of all colors for image reference position detection on the image forming body, and the positions of the color images for image reference position detection formed on this image forming body are determined. Control means for detecting and correcting the image reference position based on the position information of the color image for detecting the image reference position detected here. The present invention can remove the influence of a positional deviation from a writing position of image information, and can accurately form a reference color image based on a color deviation correction mode at an image reference position.
[0018]
A color image forming apparatus 100 shown in FIG. 1 is an example of an image forming apparatus, and is an apparatus that forms a color image on an image forming body by superimposing colors based on arbitrary image information. The color image forming apparatus 100 forms a reference color image for color misregistration correction on the image forming body, reads a passage timing of the reference color image, calculates a positional displacement amount of another color image with respect to the reference color image, and The operation is performed so as to correct the image forming position based on the displacement amount.
[0019]
The color image forming apparatus 100 includes an image forming apparatus main body 101 and an image reading apparatus 102. An image reading device 102 including an automatic document feeder 201 and a document image scanning exposure device 202 is provided above the image forming apparatus main body 101. The document d placed on the document table of the automatic document feeder 201 is transported by a transport unit, and one or both sides of the document are scanned and exposed by the optical system of the document image scanning and exposing device 202 to reflect the document image. The incident light is read by the line image sensor CCD.
[0020]
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 an image processing unit (not shown) to become digital image information. The image information is sent to image writing units (exposure units) 3Y, 3M, 3C, and 3K constituting the image forming unit.
[0021]
The above-described automatic document feeder 201 includes an automatic double-sided document transport unit. The automatic document feeder 201 reads the contents of a large number of documents d fed from a document mounting table at a time, and accumulates the contents of the documents in a storage means (electronic RDH function). This electronic RDH function is conveniently used when copying the contents of a large number of documents by the copying function, or when transmitting a large number of documents d by the facsimile function.
[0022]
The image forming apparatus main body 101 is called a tandem type color image forming apparatus. The image forming means 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, and an endless intermediate transfer as an example of the image transferring means (image transferring system). The image forming apparatus includes a belt 6, a sheet feeding / conveying unit including a sheet re-feeding mechanism (ADU mechanism), and a fixing device 17 for fixing a toner image.
[0023]
The image forming unit 10Y that forms a yellow (Y) color image includes a photoconductor drum 1Y as an image forming body that forms a Y toner image, and a Y-color charging member arranged around the photoconductor drum 1Y. There is a unit 2Y, an exposure unit 3Y, a developing device 4Y, and a cleaning unit 8Y for an image forming body. An image forming unit 10M for forming a magenta (M) color image includes a photosensitive drum 1M as an image forming body for forming an M color toner image, a charging unit 2M for M color, an exposure unit 3M, and a developing device 4M. And a cleaning unit 8M for the image forming body.
[0024]
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 color toner image, a charging device 2C for C color, an exposing device 3C, and a developing device 4C. And a cleaning unit 8C for the image forming body. The image forming unit 10K for forming a black (BK) color image includes a photosensitive drum 1K as an image forming body for forming a BK toner image, a BK color charging unit 2K, an exposure unit 3K, and a developing device 4K. And a cleaning unit 8K for the image forming body.
[0025]
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. The development by the developing devices 4Y, 4M, 4C, and 4K is performed by reversal development in which a development bias in which an AC voltage is superimposed on a DC voltage having the same polarity (negative polarity in the present embodiment) as the polarity of the toner to be used is applied. . The intermediate transfer belt 6 is wound around a plurality of rollers, is rotatably supported, and has a Y color, a M color, a C color, and a BK color formed on each of the photosensitive drums 1Y, 1M, 1C, and 1K. The toner image is transferred.
[0026]
Here, an outline of the image forming process will be described below. The image of each color formed by the image forming units 10Y, 10M, 10C, and 10K is subjected to a primary transfer (not shown) of a primary transfer bias (not shown) having the opposite polarity (positive in this embodiment) to the toner used. The rollers 7Y, 7M, 7C, and 7K sequentially transfer (primary transfer) onto the rotating intermediate transfer belt 6 to form a combined color image (color image: color toner image). The color image is transferred from the intermediate transfer belt 6 to the sheet P.
[0027]
The paper P stored in the paper feed cassettes 20A, 20B, 20C is fed by a feed roller 21 and a paper feed roller 22A provided in the paper feed cassettes 20A, 20B, 20C, respectively, and is transported by transport rollers 22B, 22C, 22D, The sheet is conveyed to the secondary transfer roller 7A via the registration roller 23 and the like, and the color image is collectively transferred onto one surface (front surface) of the sheet P (secondary transfer).
[0028]
The sheet P to which the color image has been transferred is subjected to a fixing process by the fixing device 17, is sandwiched by sheet discharge rollers 24, and is placed on a sheet discharge tray 25 outside the apparatus. The untransferred 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 means 8Y, 8M, 8C, and 8K and enters the next image forming cycle.
[0029]
At the time of double-sided image formation, an image is formed on one surface (front side) and the sheet P discharged from the fixing device 17 is branched from a sheet discharge path by a branching unit 26, and each of the sheets P constitutes a sheet feeding and conveying unit. After passing through the circulating paper path 27A, the sheet is turned upside down by a reversing conveyance path 27B, which is a re-feeding mechanism (ADU mechanism), passes through a re-feeding conveyance section 27C, and joins at a sheet feeding roller 22D.
[0030]
The sheet P that has been reversely conveyed is again conveyed to the secondary transfer roller 7A via the registration roller 23, and a color image (color toner image) is collectively transferred onto the other surface (back surface) of the sheet P. The sheet P to which the color image has been transferred is subjected to a fixing process by the fixing device 17, is sandwiched by sheet discharge rollers 24, and is placed on a sheet discharge tray 25 outside the apparatus.
[0031]
On the other hand, after the color image is transferred to the sheet P by the secondary transfer roller 7A, the intermediate transfer belt 6 from which the sheet P is separated by the curvature is removed by a cleaning unit 8A for the intermediate transfer belt. At the time of forming these images, the paper P is 52.3-63.9 kg / m ² (1000 sheets) of thin paper or 64.0-81.4 kg / m ² (1,000 sheets) plain paper, 83.0 to 130.0 kg / m ² (1000 sheets) or 150.0kg / m ² (Thousands) super thick paper is used. The thickness (paper thickness) of the paper P is about 0.05 to 0.15 mm.
[0032]
On the upstream side of the above-described cleaning unit 8A and on the left side of the intermediate transfer belt 6, there is provided a registration sensor 12, which is an example of an image detecting unit, and is provided by the above-described image forming units 10Y, 10M, 10C, and 10K. The position of a color image for color misregistration correction (hereinafter referred to as a registration mark CR) formed on the intermediate transfer belt 6 is detected to generate a position detection signal S2.
[0033]
A control unit 15 is provided in the image forming apparatus main body 101, and executes a color misregistration correction mode and an image reference position correction mode based on a position detection signal S2 obtained from the registration sensor 12. In the color misregistration correction mode, a registration mark CR for color misregistration correction is formed at the image reference position of the intermediate transfer belt 6, the passage timing of the registration mark CR is read, and the position (edge, This is an operation of calculating the amount of displacement of the registration mark CR of another color with respect to the center of gravity and correcting the image forming position at the time of color superposition.
[0034]
Here, the image reference position is a position where the registration sensor 12 can accurately read the registration mark CR on the intermediate transfer belt 6. This image reference position is set at a predetermined distance to the left, for example, from the substantially center position of the photosensitive drums 1Y, 1M, 1C, 1B in the main scanning direction in which the laser beam scans the photosensitive drum 1Y and the like. Design reference position. This image reference position is in the same position as the mark reference position for color registration correction.
[0035]
In this example, the image reference position is a position where the center of the registration mark CR, which is the mark reference position, and the center (optical axis) of the light receiving section of the registration sensor 12 match. That is, assuming that the moving direction of the intermediate transfer belt 6 is the sub-scanning direction, in the intermediate transfer belt 6 moving in the sub-scanning direction, the optical axis of the registration sensor 12 traces the detection locus line at the center of the registration mark CR. It is done as follows.
[0036]
Further, the image forming position at the time of color superposition means that when an arbitrary color image based on the color image data is reproduced by the intermediate transfer belt 6, each toner image of Y, M, C, BK, etc. Refers to the position where they are overlapped. The image reference position, the image forming position, and the like are corrected by adjusting the image writing start position for the photosensitive drums 1Y, 1M, 1C, and 1K.
[0037]
Further, the color image forming apparatus 100 is provided with an image reference position compensation mode in addition to the color misregistration correction mode. In the image reference position correction mode, all color image information for detecting the image reference position is written on the photosensitive drum, all the color images are formed on the intermediate transfer belt 6, and the image formed on the intermediate transfer belt 6 is formed. This refers to an operation of detecting the position of the color image for detecting the reference position, and correcting the image reference position based on the detected position information of the color image for detecting the image reference position.
[0038]
In this example, when the width direction of the intermediate transfer belt 6 is the main scanning direction, the color image for detecting the image reference position includes a line segment parallel to the main scanning direction and a predetermined angle (for example, , 45 °). For example, the color image for detecting the image reference position forms a “F” character. For the color image for detecting the image reference position, a registration mark CR having a larger size than the registration mark CR for correcting color misregistration is used. The reason why the size of the color image for detecting the image reference position is made larger than the registration mark CR for correcting color misregistration is that the color image for detecting the image reference position can be sufficiently captured (reflected) in the detection range of the registration sensor 12. This is because
[0039]
The image reference position correction mode is used when the image forming units 10Y, 10M, 10C, and 10K are first assembled with the registration sensor 12 in the manufacturing process of the device main body, or when the writing units 3Y and 3M are sold after the device main body is sold. , 3C, 3K, the registration sensor 12 and the like are required to accurately form the registration mark CR for correcting color misregistration at the image reference position of the intermediate transfer belt 6. The registration sensor 12 and the writing units 3Y, 3M, 3C, 3K, etc. are usually mounted at design positions, but in practice there are machine assembly tolerances.
[0040]
In this image reference position correction mode, the image reference positions based on the image forming units 10Y, 10M, 10C, 10K, etc. match the image detection reference positions based on the registration sensor 12 without the influence of assembly tolerance. It is executed to make it.
[0041]
FIG. 2 is a block diagram illustrating a configuration example of an image transfer and image forming system of the color image forming apparatus 100. The color image forming apparatus 100 shown in FIG. 2 is obtained by extracting the intermediate transfer belt 6 shown in FIG. 1 as an image transfer system I and extracting the image forming units 10Y, 10M, 10C, and 10K as an image forming system II.
[0042]
In FIG. 2, the color image forming apparatus 100 has a control unit 15. The registration sensor 12 is connected to the control unit 15, detects the position of the toner image (color image) formed on the intermediate transfer belt 6, and outputs a position detection signal S 2 to the control unit 15. The control unit 15 controls the image forming units 10Y, 10M, 10C, and 10K based on the position detection data Dp obtained by converting the position detection signal S2 obtained from the registration sensor 12 from analog to digital. The control unit 15 is connected to the nonvolatile memory 14 and stores position detection data Dp and data relating to the amount of positional deviation and the amount of color deviation.
[0043]
The image forming units 10Y, 10M, 10C, and 10K are connected to the control unit 15, and the image forming unit 10Y attaches Y to the intermediate transfer belt 6 based on Y-color image information Dy that constitutes arbitrary image information Din. A color toner image is formed, the image forming unit 10M forms an M color toner image on the intermediate transfer belt 6 based on the M color image information Dm, and the image forming unit 10C generates a C color image information Dc. Then, a C color toner image is formed on the intermediate transfer belt 6 based on the image information, and the BK color toner image is formed on the intermediate transfer belt 6 based on the BK color image information Dk.
[0044]
In this example, a correction unit 5Y is attached to the Y-color image writing unit (exposure unit) 3Y, and based on the optical system position adjustment Sy for the Y color from the control unit 15 in the color misregistration correction mode. The geometric position of the optical system such as the f (θ) lens of the unit 3Y is adjusted (partial lateral magnification, skew adjustment, and the like). Similarly, a correction unit 5M is attached to the M-color image writing unit 3M, and based on the M-color optical system position adjustment Sm from the control unit 15, such as an f (θ) lens of the unit 3M. The geometric position of the optical system is adjusted.
[0045]
The correction unit 5C is attached to the image writing unit 3C for C color, and based on the optical system position adjustment Sc for C color from the control unit 15, the correction of the optical system such as the f (θ) lens of the unit 3C is performed. An adjustment is made to the geometric position. The correction unit 5K is attached to the image writing unit 3K for BK color, and based on the optical system position adjustment Sk for BK color from the control unit 15, the correction of the optical system such as the f (θ) lens of the unit 3K is performed. An adjustment is made to the geometric position.
[0046]
FIG. 3 is an image diagram showing a configuration example of the image writing unit 3Y for Y color and its correcting means 5Y. The image writing unit 3Y for Y color shown in FIG. 3 has a semiconductor laser light source 31, optical systems 32 and 33, a polygon mirror 34, a polygon motor 35, and an f (θ) lens. In the semiconductor laser light source 31, a laser beam is generated by a laser drive signal Dy 'that has been subjected to a PWM modulation process or the like based on the Y-color image information Dy. The laser light emitted from the semiconductor laser light source 31 is shaped into a predetermined light beam by an optical system.
[0047]
This light beam is deflected by the polygon mirror 34 in the main scanning direction. The polygon mirror 34 is rotated by a polygon motor 35 based on the Y polygon CLK from the control means 15. The light beam deflected by the polygon mirror 34 is imaged by the f (θ) lens 36 toward the photosensitive drum 1Y. With this operation, an electrostatic latent image such as the registration mark CR is formed on the photosensitive drum 1Y.
[0048]
The image writing unit 3Y is provided with a correction unit 5Y. The correction unit 5Y includes a lens holding mechanism 41, an f (θ) adjustment mechanism 42, an optical axis adjustment mechanism 43, and the like.
[0049]
In this example, the calculation of the color misregistration amount is based on the BK color registration mark CR. This is to adjust the writing position of the Y, M, and C color images to match the BK color. The contents of the correction processing are, for example, the following five (1) to (5). Among the contents of the correction processing, (1) to (3) are realized by correcting the image data, (4) and (5) drive the motors, and actually write the write units 3Y, 3M, 3C, and 3K. It is made to adjust by driving.
[0050]
(1) Main scanning correction processing
This process is a correction for aligning the writing positions of the Y, M, C, and BK color images in the main scanning direction. For example, with respect to the Y color writing position correction, the main scanning writing timing of the BK registration mark CR and the main scanning writing timing of the Y registration mark CR are detected, and the writing timing of the Y registration mark CR is determined. The correction amount is calculated from the shift amount when converted to the writing position of the BK color registration mark CR. Based on this correction amount, the writing position of the BK color registration mark CR in the main scanning direction and the writing position of the Y, M, and C color images are aligned.
[0051]
(2) Sub-scan correction processing
This process is a correction for aligning the writing positions in the sub-scanning direction of the Y, M, C, and BK color images. For example, with respect to the writing position adjustment of the Y color, the sub-scanning writing timing of the BK registration mark CR and the sub-scanning writing timing of the Y registration mark CR are detected, and the writing timing of the Y registration mark CR is detected. The correction amount is calculated from the shift amount when converted to the writing position of the BK color registration mark CR. Based on this correction amount, the writing position of the BK color registration mark CR in the sub scanning direction and the writing position of the Y, M, and C color images are aligned.
[0052]
(3) Whole horizontal magnification correction processing
This process is a correction for aligning the image forming positions in the entire color image of Y, M, C, and BK colors. For example, the cycle of the image clock signal is adjusted to adjust the laser emission timing, and the overall lateral displacement is corrected based on this adjustment.
[0053]
(4) Partial lateral magnification correction processing
This processing is a correction for adjusting the inclination of the horizontal position of each of the writing units 3Y, 3M, 3C, 3K and the like. For example, the f (θ) lens 36 is attached to the lens holding mechanism 41 of the writing unit 3Y shown in FIG. The lens holding mechanism 41 is movably attached to the f (θ) adjusting mechanism 42 and the optical axis adjusting mechanism 43. The f (θ) adjusting mechanism 42 moves and adjusts the lens holding mechanism 41 in the XY (horizontal) direction based on the position correction signal Sy including the rotation component. The optical axis adjustment mechanism 43 moves and adjusts the lens holding mechanism 41 in the Z direction (optical axis direction) based on the position correction signal Sy. These mechanisms 42 and 43 are embodied by an actuator (piezoelectric element), motor control, or the like. This is for adjusting the inclination of the horizontal position of the writing unit 3Y with respect to the photosensitive drum 1Y. Similar processing is performed in the other image forming units 10M and 10C.
[0054]
▲ 5 ▼ Skew correction processing
This processing is a correction for adjusting the inclination of the vertical position of each of the writing units 3Y, 3M, 3C, 3K and the like. For example, the f (θ) adjusting mechanism 42 shown in FIG. 3 moves and adjusts the lens holding mechanism 41 in the XZ direction or the YZ direction based on the position correction signal Sy. This is for adjusting the inclination of the vertical position of the writing unit 3Y with respect to the photosensitive drum 1Y. Similar processing is performed in the other image forming units 10M and 10C.
[0055]
FIG. 4 is a block diagram illustrating a configuration example of a control system of the color image forming apparatus 100. The color image forming apparatus 100 shown in FIG. 4 includes a registration sensor 12, a nonvolatile memory 14, and a control unit 15. The control unit 15 includes, for example, an analog / digital converter (hereinafter, referred to as an A / D converter) 13, a correction amount calculation unit 51, a main scanning start timing control unit 52, a sub-scanning start timing control unit 53, and a pixel clock cycle control unit 54. , An image forming unit driving section 55 and a CPU 57.
[0056]
The registration sensor 12 is connected to the A / D converter 13. The A / D converter 13 A / D converts the position detection signal S2 output from the registration sensor 12 through the image reference position correction mode and the color misregistration correction mode and outputs the binarized position detection data Dp. It is done as follows. The A / D converter 13 is connected to the nonvolatile memory 14. The non-volatile memory 14 stores position detection data Dp, and data relating to the amount of positional deviation ε and the amount of color deviation.
[0057]
The nonvolatile memory 14 is connected to the correction amount calculation unit 51 and the CPU 57. The correction amount calculation unit 51 includes a main scanning correction amount calculation unit 511, a sub-scanning correction amount calculation unit 512, an overall lateral magnification correction amount calculation unit 513, a partial lateral magnification correction amount calculation unit 514, and a skew correction amount calculation unit 515. You. The correction amount calculation unit 51 reads out the position detection data Dp from the non-volatile memory 14 in the color misregistration correction mode, and calculates the deviation amount of each error factor (main scanning, overall magnification, partial lateral magnification, skew) from the position detection data Dp. The correction amount is calculated, and the correction amount for each error factor is obtained from the calculated shift amount.
[0058]
For example, the main scanning correction amount calculation unit 511 reads the position detection data Dp from the nonvolatile memory 14, calculates the amount of positional deviation in the main scanning direction, and adjusts the write timing in the main scanning direction so as to eliminate the amount of positional deviation. Control data D1 is output. The timing control data D1 is used to correct a position shift in the main scanning direction.
[0059]
The sub-scanning correction amount calculation unit 512 reads out the position detection data Dp from the nonvolatile memory 14, calculates the amount of positional deviation in the sub-scanning direction, and adjusts the writing start timing in the sub-scanning direction so as to eliminate the amount of positional deviation. It outputs timing control data D2. The timing control data D2 corrects the positional deviation in the sub-scanning direction.
[0060]
The overall lateral magnification correction amount calculation unit 513 reads out the position detection data Dp from the nonvolatile memory 14, calculates the overall lateral magnification deviation amount, and adjusts the frequency of the pixel clock signal so as to eliminate the overall lateral magnification deviation amount. It outputs clock control data D3. With this clock control data D3, the overall lateral displacement can be corrected.
[0061]
The partial lateral magnification correction amount calculation unit 514 reads the position detection data Dp from the nonvolatile memory 14 to calculate the partial lateral magnification deviation amount, and eliminates the horizontal inclination of the image writing unit 3Y or the like so as to eliminate the partial lateral magnification deviation amount. Is output as write control data D4 for adjusting. With this write control data D4, the partial lateral double shift amount can be corrected.
[0062]
The skew correction amount calculation unit 515 reads the position detection data Dp from the nonvolatile memory 14 to calculate a skew deviation amount, and performs writing for adjusting a vertical inclination of the image writing unit 3Y or the like so as to eliminate the skew deviation amount. It outputs control data D5. The skew deviation amount can be corrected by the write control data D5.
[0063]
The CPU 57 controls the image forming units 10Y, 10M, 10C, and 10K for the Y, M, C, and BK colors according to the correction amounts of the respective error factors. For example, the CPU 57 outputs the timing control data D1 created by the main scanning correction amount calculation unit 511 to the main scanning start timing control unit 52. The main scanning start timing control unit 52 operates to adjust the writing start timing in the main scanning direction based on the timing control data D1 so as to eliminate the positional deviation amount in the main scanning direction. Further, the CPU 57 outputs the timing control data D2 created by the sub-scanning correction amount calculation unit 512 to the sub-scanning start timing control unit 53. The sub-scanning start timing control unit 53 operates to adjust the writing start timing in the sub-scanning direction based on the timing control data D2 so as to eliminate the positional deviation amount in the sub-scanning direction.
[0064]
Further, the CPU 57 outputs the clock control data D3 created by the overall lateral magnification correction amount calculation unit 513 to the pixel clock cycle control unit 54. The pixel clock cycle control unit 54 corrects the overall lateral double shift amount based on the clock control data D3. Further, the CPU 57 outputs the write control data D4 created by the partial lateral magnification correction amount calculation section 514 to the write unit drive section 55. The write unit drive unit 55 corrects the partial lateral double shift amount based on the write control data D4. Further, the CPU 57 outputs the write control data D4 created by the skew correction amount calculation section 515 to the image forming unit drive section 56. The image forming unit driving section 56 corrects the skew deviation amount based on the write control data D5.
[0065]
FIG. 5 is a perspective view showing an example of detecting a registration mark CR by two registration sensors 12A and 12B. FIG. 6 is a diagram illustrating an example of forming a registration mark CR for detecting an image reference position.
On the intermediate transfer belt 6 shown in FIG. 5, for example, a "F" -shaped registration mark CR for detecting an image reference position is formed. The registration marks CR are created side by side at the left and right ends along the sub-scanning direction of the intermediate transfer belt 6. The positions of the registration marks CR formed on the intermediate transfer belt 6 are detected by the registration sensors 12A and 12B. In order to detect the two rows of registration marks CR, the registration sensors 12A and 12B are arranged side by side above the intermediate transfer belt 6. For example, the registration sensors 12A and 12B are mounted at design reference positions on the apparatus main body side.
[0066]
The registration mark CR has a shape similar to that of the registration mark CR formed in the color misregistration correction mode, and is formed in a larger size. The registration mark CR for detecting the image reference position has a size of, for example, a machine writing position tolerance × about 2 so that the registration sensor 12A or the like can sufficiently detect the writing position due to a mechanical assembly tolerance. Formed.
[0067]
In this example, in the sub-scanning direction, which is the direction of movement of the intermediate transfer belt 6 shown in FIG. 6, "F" -shaped BK color registration marks CR for detecting the image reference position are formed one by one at the left and right ends. Subsequently, C-color resist marks CR are formed one by one on the left and right ends, and M-color resist marks CR are formed one by one on the left and right ends. One at each end is formed. The reason why the registration marks CR of each color are formed one by one at the left and right ends is that the number is sufficient and sufficient to detect and correct the image reference position.
[0068]
The registration mark CR for detecting the image reference position is used to detect the image forming positions of the registration marks CR of all colors separately from the registration mark CR for correcting color misregistration when the image reference position correction mode is executed. The image forming units 10Y, 10M, 10C and 10K are controlled by the CPU 57 shown in FIG. The registration mark CR for detecting the image reference position is detected by the registration sensor 12, and the CPU 57 calculates the amount of displacement of the registration mark CR of each color with respect to the image forming position, and corrects the image reference position. , 10M, 10C, and 10K.
[0069]
7A and 7B are diagrams showing an example of binarization of the position detection signal S2 by the registration sensor 12A and the like.
In FIG. 7A, the position detection signal S2 obtained by the registration sensor 12A or the like is binarized based on a preset threshold Lth. In this example, the passing timing pulse signal Sp rises at the time ta when the point a where the position detection signal S2 falls crosses the threshold Lth, and the passing timing pulse at the time tb where the point b where the position detection signal S2 crosses the threshold Lth. The signal Sp falls. The passing timing pulse signal Sp becomes the position detection data Dp after being binarized. The position detection data Dp is used as a reference for adjusting the displacement of the color image. For example, the position detection data Dp is used for calculating a shift amount of the writing position of the Y, M, and C colors with respect to the writing position of the BK registration mark CR.
[0070]
FIG. 8 is a diagram illustrating an example (part 1) of the relationship between the registration mark CR for detecting the image reference position and the registration sensor 12.
The registration mark CR for detecting the image reference position shown in FIG. 8 is an example in which the reference line Lr of the registration mark CR and the detection trajectory line Lo of the registration sensor 12 match. The detection trajectory line Lo is uniquely determined by mounting the registration sensor 12 at a design position on the apparatus main body side and moving the intermediate transfer belt 6. The registration mark CR for detecting the image reference position is composed of 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 parallel to the main scanning direction, and a point at which the line segment having an angle of 45 ° and the auxiliary line intersect is drawn. When d is set, a line segment connecting the points c and d is defined as a reference line Lr of the registration mark CR, and a length of the line segment between the points cd is set as Lb.
[0071]
In this example, the length Lb of the line segment between the points cd is calculated from the difference between the detection times of the points c and d of the registration mark CR, thereby obtaining the reference line of the registration mark CR for detecting the image reference position. Lr and the detection trajectory line Lo of the registration sensor 12 are made to coincide with each other. Thus, the center point c of the registration mark CR can be traced on the detection trajectory line Lo of the registration sensor 12.
[0072]
9A and 9B are diagrams illustrating a relationship example (part 2) between the registration mark CR for detecting the image reference position and the registration sensor 12. FIG.
The registration mark CR for detecting the image reference position shown in FIG. 9A is an example in which the reference line Lr of the registration mark CR does not match the detection trajectory line Lo of the registration sensor 12. In this example, the registration mark CR for detecting the image reference position is formed with a displacement ε to the left from the detection trajectory line Lo of the registration sensor 12. In such a case, it is necessary to correct the image reference position.
[0073]
In this example, a registration mark CR for detecting an image reference position that moves on the detection trajectory line Lo of the registration sensor 12 is detected. In FIG. 9A, a point at which a line segment parallel to the main scanning direction crosses the registration sensor 12 is denoted by c ′, and a point at which a line segment having an angle of θ = 45 ° with respect to the main scanning direction crosses the registration sensor 12. When d ′ is set, the length Lx of the line segment between the points c ′ and d ′ is detected. The length Lx is calculated from the difference between the detection times between the two lines.
[0074]
In the image reference position correction mode, the length Lb of the line segment between the two lines when the displacement amount ε = 0 is compared with the length Lx of the line segment between the two lines when the displacement amount ε = εx. Is done. The CPU 57 calculates εx = Lb−Lx. The image writing position is corrected so that the displacement amount ε = εx is preferably set to ε = 0. In the example shown in FIG. 9B, the image information is written on the photosensitive drum 1Y or the like by shifting the registration mark CR to the right by the positional shift amount ε = εx. By correcting the image writing position, the reference line Lr of the registration mark CR and the detection trajectory line Lo of the registration sensor 12 can be matched.
[0075]
The displacement ε = εx is stored in the nonvolatile memory 14 as an initial value of the color image forming apparatus 100. The displacement amount ε = εx stored in the nonvolatile memory 14 is sequentially updated. Such an image reference position correction mode is executed before the color misregistration correction mode, and the color misregistration correction operation is executed after the misregistration amount ε of the registration mark CR becomes, for example, a predetermined amount or less. You. The position shift amount ε = εx stored in the nonvolatile memory 14 is reflected on the image reference position in the color shift correction mode. That is, the image reference position of the image forming system is adjusted to the image detection reference position of the color misregistration detection system.
[0076]
FIG. 10 is a diagram showing an example of forming a registration mark CR ′ for color misregistration correction. The registration mark CR ′ shown in FIG. 10 is formed when the color misregistration correction mode is executed. The image forming units 10Y, 10M, 10C, and 10K are controlled by the CPU 57 shown in FIG. 4 to form the registration mark CR ′ for color misregistration on the intermediate transfer belt 6.
[0077]
In this example, in the sub-scanning direction, which is the direction in which the intermediate transfer belt 6 moves, four "F" -shaped BK color registration marks CR 'for color misregistration correction are continuously formed on the left and right ends. Subsequently, four C-color resist marks CR 'are continuously formed on the left and right ends, and four M-color resist marks CR' are continuously formed on the left and right ends. Four color registration marks CR 'are continuously formed on the left and right ends, respectively. 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 each color registration mark CR and to correct this accurately.
[0078]
These registration marks CR ′ for correcting color misregistration are detected by the registration sensor 12, the amount of color misregistration of the registration marks CR ′ of each color with respect to the image forming position is calculated, and the image forming units 10Y and 10Y are configured to correct the image forming position. 10M, 10C and 10K are controlled. This control is for accurately overlaying color images based on arbitrary image data in the image forming system after executing the color misregistration correction mode.
[0079]
Subsequently, an image forming method as an embodiment according to the present invention will be described. FIG. 11 is a flowchart illustrating an example of image formation in the color image forming apparatus 100.
In this embodiment, when a color image based on image information for an arbitrary color is formed on the intermediate transfer belt 6, the registration mark formation processing mode is executed in advance, irregularly, or periodically. In this example, it is assumed that the above-described image reference position correction mode and color misregistration correction mode are prepared in the registration mark formation processing mode. The image reference position correction mode is executed as necessary before the control unit 15 executes the color misregistration correction mode.
[0080]
In the image reference position correction mode, a registration mark CR for detecting an image reference position is formed to detect an image formation position of the registration mark CR of all colors separately from the registration mark CR ′ for correcting color misregistration. An example will be described in which the registration sensor CR for detecting the reference position is detected by the registration sensor 12, the amount of displacement of the registration mark CR of each color with respect to the image forming position is calculated, and the image reference position is corrected.
[0081]
Under these processing conditions, in the manufacturing process of the apparatus main body, when the image forming units 10Y, 10M, 10C, and 10K are first assembled with the registration sensor 12, or after the apparatus main body is sold, the writing unit 3Y, When the 3M, 3C, 3K, the registration sensor 12, and the like are replaced, it is necessary to accurately form the registration mark CR for correcting color misregistration at the image reference position of the intermediate transfer belt 6. Thus, first, the image reference position correction mode is executed in step A1 of the flowchart shown in FIG. In the image reference position correction mode, image information of all colors for detecting the image reference position is written on the photosensitive drum, and registration marks CR of all colors are formed on the intermediate transfer belt 6. At this time, a registration mark CR for detecting an image reference position having a shape similar to the registration mark CR formed in the color misregistration correction mode and having a larger size is created.
[0082]
For example, in the image forming unit 10K, after the photosensitive drum 1K is charged to a predetermined potential, BK color image information for detecting an image reference position is written once to the photosensitive drum 1K. By this writing, an electrostatic latent image serving as a registration mark CR for detecting an image reference position is formed on the photosensitive drum 1K. This electrostatic latent image is developed with a BK color toner. The BK color toner image for image reference position detection after the development is transferred (primary transfer) onto the intermediate transfer belt 6. Thereby, the "F" -shaped BK color registration marks CR for detecting the image reference position can be formed one by one on the left and right ends of the intermediate transfer belt 6 shown in FIG.
[0083]
In the image forming unit 10C, after the photosensitive drum 1C is charged to a predetermined potential, C-color image information for detecting an image reference position is written once to the photosensitive drum 1C. By this writing, an electrostatic latent image serving as a registration mark CR for detecting an image reference position is formed on the photosensitive drum 1C. This electrostatic latent image is developed with the C color toner. The C color toner image for detecting the image reference position after the development is transferred onto the intermediate transfer belt 6. Thereby, it is possible to form one "F" -shaped C-color registration mark CR for detecting the image reference position at each of the left and right ends of the intermediate transfer belt 6 shown in FIG.
[0084]
Similarly, in the image forming unit 10M, after the photosensitive drum 1M is charged to a predetermined potential, M color image information for detecting an image reference position is written once to the photosensitive drum 1M. By this writing, an electrostatic latent image serving as a registration mark CR for detecting an image reference position is formed on the photosensitive drum 1M. This electrostatic latent image is developed with a Y color toner. The M color toner image for detecting the image reference position after the development is transferred onto the intermediate transfer belt 6. Thereby, it is possible to form one M-shaped registration mark CR in a “F” shape for detecting the image reference position at each of the left and right ends of the intermediate transfer belt 6 shown in FIG.
[0085]
In the image forming unit 10Y, after the photosensitive drum 1Y is charged to a predetermined potential, the Y color image information for detecting the image reference position is written once to the photosensitive drum 1Y. By this writing, an electrostatic latent image serving as a registration mark CR for detecting an image reference position is formed on the photosensitive drum 1Y. This electrostatic latent image is developed with a Y color toner. The Y color toner image for image reference position detection after the development is transferred onto the intermediate transfer belt 6 to form a Y color registration mark CR. On the left and right ends of the intermediate transfer belt 6 shown in FIG. 6, “F” -shaped Y-color registration marks CR for detecting an image reference position can be formed one by one. The registration marks CR of BK, C, M, and Y for detecting the image reference position can be created.
[0086]
Then, the process proceeds to step A2, and the registration sensor 12 reads the passage timing of the registration mark CR of each color for detecting the image reference position. At this time, the registration mark CR of each color for detecting the image reference position is detected by the registration sensor 12A or the like. The position detection signal S2 obtained by the registration sensor 12A or the like is binarized based on the threshold Lth shown in FIG. 7A.
[0087]
In this example, the passing timing pulse signal Sp rises at the time ta when the point a where the position detection signal S2 falls crosses the threshold Lth, and the passing timing pulse at the time tb where the point b where the position detection signal S2 crosses the threshold Lth. The signal Sp falls. The passing timing pulse signal Sp becomes the position detection data Dp after being binarized. The position detection data Dp is used as a reference for correcting the shift amount ε of the image reference position. For example, the CPU 57 determines the amount of deviation between the image forming position of the BK, C, M, and Y registration marks CR for detecting the image reference position and the detection trajectory line Lo of the registration sensor 12 (hereinafter, the deviation amount ε of the image reference position). Is calculated.
[0088]
Thereafter, in step A3, it is determined whether or not the shift amount ε of the image reference position is equal to or less than a predetermined amount. For example, the CPU 57 determines the length Lb of the line segment between the two lines when the displacement amount ε = 0 shown in FIG. 8 and the line length between the two lines when the displacement amount ε = εx shown in FIG. 9A. Compare with the minute length Lx. The CPU 57 calculates εx = Lb−Lx.
[0089]
If the shift amount ε of the image reference position exceeds a predetermined amount, the process proceeds to step A4 to execute an image reference position correction process. At this time, the control means 15 controls the image forming units 10Y, 10M, 10C and 10K so that the writing position of the image information of each color is adjusted to the image reference position based on the shift amount ε of the image reference position. In this control, the image writing position is corrected so that the shift amount ε = εx is preferably set to ε = 0. In the image forming unit 10K, the image writing unit 3K is corrected by the correction unit 5K. In the example shown in FIG. 9B, the image information is written on the photosensitive drum 1Y or the like by shifting the registration mark CR to the right by the positional shift amount ε = εx.
[0090]
Similarly, in the image forming unit 10C, the image writing unit 3C is corrected by the correcting unit 5C, in the image forming unit 10M, the image writing unit 3M is corrected by the correcting unit 5M, and in the image forming unit 10Y, the image writing unit 3Y is corrected. Is corrected by the correction means 5Y. By correcting the image writing position, the reference line Lr of the registration mark CR and the detection trajectory line Lo of the registration sensor 12 can be matched.
[0091]
The displacement ε = εx is stored in the nonvolatile memory 14 as an initial value of the color image forming apparatus 100. The misregistration amount ε = εx stored in the non-volatile memory 14 is sequentially updated by the color misregistration correction value obtained in the color misregistration correction mode. Such an image reference position correction mode is executed before the color misregistration correction mode, and the color misregistration correction operation is executed after the misregistration amount ε of the registration mark CR becomes, for example, a predetermined amount or less. You.
[0092]
If the shift amount ε of the image reference position is equal to or smaller than the predetermined amount in step A3, the process proceeds to step A5 to execute the color shift correction mode. In the color misregistration correction mode, a registration mark CR ′ for color misregistration correction as shown in FIG. At this time, the registration mark CR ′ for color misregistration correction has a shape similar to the registration mark CR formed in the image reference position correction mode, and is formed in a smaller size.
[0093]
In this color misregistration correction mode, for example, the BK color image information for color misregistration correction is written four times on the photosensitive drum 1K in the image forming unit 10K at the image reference position defined and corrected in advance on the intermediate transfer belt 6. Then, an electrostatic latent image serving as a registration mark CR ′ for color misregistration is formed, and this electrostatic latent image is developed with a toner material for BK color. The image is transferred to the image reference position of the transfer belt 6. Thus, four “F” -shaped BK color registration marks CR ′ for color misregistration correction can be continuously formed on the left and right ends of the intermediate transfer belt 6.
[0094]
Further, in the image forming unit 10C, the C color image information for color shift correction is written to the photosensitive drum 1C four times to form an electrostatic latent image serving as a registration mark CR ′ for color shift correction. The electrostatic latent image is developed with a C color toner, and the C color toner image for color shift correction after development is transferred to the image reference position of the intermediate transfer belt 6. As a result, four “F” -shaped C-color registration marks CR ′ for color misregistration correction can be continuously formed on the left and right ends of the intermediate transfer belt 6.
[0095]
Similarly, in the image forming unit 10M, the M color image information for color shift correction is written to the photosensitive drum 1M four times to form an electrostatic latent image serving as a registration mark CR ′ for color shift correction. The electrostatic latent image is developed with the M color toner, and the developed color misregistration correction M color toner image is transferred to the image reference position of the intermediate transfer belt 6. This makes it possible to form four M-shaped registration marks CR ′ in a “F” shape for color misregistration correction on the left and right ends of the intermediate transfer belt 6 continuously.
[0096]
Further, in the image forming unit 10Y, the Y color image information for color shift correction is written four times on the photosensitive drum 1Y, and an electrostatic latent image serving as a registration mark CR ′ for color shift correction is formed. The electrostatic latent image is developed with a Y color toner agent, and the Y color toner image for color shift correction after development is transferred to an image reference position of the intermediate transfer belt 6. As a result, it is possible to continuously form four “F” -shaped Y color registration marks CR ′ at the left and right ends of the intermediate transfer belt 6 for color shift correction. A registration mark CR ′ for color misregistration correction can be created in the sub-scanning direction of the intermediate transfer belt 6.
[0097]
Then, the process proceeds to step A6 to read the passage timing of the registration mark CR 'of each color and calculate the amount of color shift of the registration mark CR' of another color with respect to the registration mark CR 'of the reference color. At this time, the registration mark CR ′ for correcting color misregistration is detected by the registration sensor 12A or the like. The position detection signal S2 obtained by the registration sensor 12A or the like is binarized based on the threshold Lth shown in FIG. 7A.
[0098]
In this example, the passing timing pulse signal Sp rises at the time ta when the point a where the position detection signal S2 falls crosses the threshold Lth, and the passing timing pulse at the time tb where the point b where the position detection signal S2 crosses the threshold Lth. The signal Sp falls. The passing timing pulse signal Sp becomes the position detection data Dp after being binarized. The position detection data Dp is used as a reference for adjusting the displacement of the color image. For example, the position detection data Dp is used to calculate the amount of shift between the writing positions of the Y, M, and C colors with respect to the writing positions of the BK registration marks CR.
[0099]
Then, in order to correct the writing position of the Y, M, and C colors with respect to the image forming position of the BK registration mark CR ', the process proceeds to step A7, and the other Y, M for the BK (reference) registration mark CR' is corrected. It is determined whether the amount of color misregistration of the M and C color registration marks CR is equal to or less than a predetermined amount. If these color misregistration amounts are equal to or smaller than the predetermined amount, the registration mark formation processing mode is ended. If the amount of color misregistration exceeds a predetermined amount, the process proceeds to step A8 to execute a color misregistration correction process. At this time, the correction amount calculation unit 51 reads the position detection data Dp from the nonvolatile memory 14 and calculates the deviation amount of each error factor (main / sub-scanning, overall magnification, partial lateral magnification, skew) from the position detection data Dp. Then, a correction amount for each error factor is obtained from the calculated shift amount.
[0100]
For example, the main scanning correction amount calculation unit 511 reads out the position detection data Dp from the nonvolatile memory 14, calculates the amount of positional deviation in the main scanning direction, creates the timing control data D1 under the control of the CPU 57, and The data D1 is output to the main scanning start timing control unit 52. The timing control data D1 is information for adjusting the writing start timing in the main scanning direction so as to eliminate the displacement amount. The main scanning start timing control unit 52 operates to adjust the writing start timing in the main scanning direction based on the timing control data D1.
[0101]
Further, the sub-scanning correction amount calculation unit 512 reads out the position detection data Dp from the nonvolatile memory 14, calculates the amount of positional deviation in the sub-scanning direction, creates timing control data D2 under the control of the CPU 57, and The data D2 is output to the sub-scanning start timing control unit 53. The timing control data D2 is information for adjusting the writing start timing in the sub-scanning direction so as to eliminate the position shift amount. The sub-scanning start timing control unit 53 operates to adjust the writing start timing in the sub-scanning direction based on the timing control data D2.
[0102]
The overall lateral magnification correction amount calculation unit 513 reads out the position detection data Dp from the nonvolatile memory 14, calculates the overall lateral magnification deviation amount, creates the clock control data D3 under the control of the CPU 57, and generates the clock control data D3. Output to the pixel clock cycle control unit 54. The clock control data D3 is information for adjusting the frequency of the pixel clock signal so as to eliminate the entire lateral double shift amount. The pixel clock cycle control unit 54 corrects the entire lateral double shift amount based on the clock control data D3.
[0103]
The partial lateral magnification correction amount calculation unit 514 reads out the position detection data Dp from the nonvolatile memory 14, calculates the partial lateral magnification deviation amount, creates the write control data D4 under the control of the CPU 57, and writes the write control data D4. Output to the writing unit drive unit 55. The write control data D4 is information for adjusting the horizontal inclination of the image writing unit 3Y or the like so as to eliminate the partial lateral double shift amount. The write unit drive unit 55 corrects the partial lateral double shift amount based on the write control data D4.
[0104]
The skew correction amount calculation unit 515 reads the position detection data Dp from the nonvolatile memory 14 to calculate a skew deviation amount, creates write control data D5 under the control of the CPU 57, and uses the write control data D5 to drive the image forming unit. Output to the unit 56. The write control data D5 is information for adjusting the vertical inclination of the image writing unit 3Y or the like so as to eliminate the skew shift amount. The image forming unit driving section 56 corrects the skew deviation amount based on the write control data D5.
[0105]
As described above, according to the color image forming apparatus and the image forming method according to the embodiment of the present invention, when a color image based on image information for an arbitrary color is formed on the intermediate transfer belt 6, the CPU 57 controls the Y color. , M, C and BK image forming units 10Y, 10M, 10C and 10K write image information of all the colors for detecting the image reference position on the intermediate transfer belt 6 to obtain Y, M and C colors. And a resist mark CR of BK color is formed. Then, the CPU 57 detects the positions of the Y, M, C, and BK registration marks CR for detecting the image reference position formed on the intermediate transfer belt 6 by the registration sensors 12A and 12B. , 12B, the image reference position is corrected based on the position detection data Dp of the registration mark CR for detecting the image reference position.
[0106]
Therefore, the image reference positions in the image forming units 10Y, 10M, 10C, and 10K for the predetermined Y, M, C, and BK colors, and the image forming units 10Y, 10M, 10C, and 10K form the image. In the image forming system after the execution of the image reference position correction mode, it is possible to perform an arithmetic process for eliminating the influence of the position shift ε between the writing position of each color registration mark CR for detecting the image reference position. The accurate color misregistration correction mode can be executed according to the correction amount of the factor.
[0107]
Thereby, in the manufacturing process of the device main body, when the image forming units 10Y, 10M, 10C, 10K and the intermediate transfer belt 6 and the registration sensors 12A, 12B are first assembled, or after the device main body is sold, When the writing units 3Y, 3M, 3C, 3K, the registration sensor 12, and the like are replaced, the registration mark CR ′ for correcting color misregistration can be accurately formed at the image reference position of the intermediate transfer belt 6.
[0108]
As a result, even if there is a mechanical attachment variation between the apparatus main body and the registration sensors 12A, 12B, etc., normal color shift detection can be performed, and mechanical restrictions for color shift correction processing are eliminated. Further, it is not necessary to increase the size of the registration mark CR in the color misregistration correction mode in consideration of the shift amount ε of the image reference position, and the size of the registration mark CR can be reduced. It leads to reduction.
[0109]
In this embodiment, the image forming units 10Y, 10M, 10C, and 10K that form Y, M, C, and BK toner images on the photosensitive drums 1Y, 1M, 1C, and 1K, respectively, relate to image forming means. And the image transfer belt 6 for transferring the toner images formed on the photoconductor drums 1Y, 1M, 1C, and 1K for each color, but the present invention is not limited to this. The present invention is also applicable to a color image forming apparatus that forms a color image by superimposing colors on one transfer material conveying belt.
[0110]
【The invention's effect】
As described above, according to the image forming apparatus and the image forming method according to the present invention, all color images are written by writing image information of all colors for detecting an image reference position, and all the color images are formed. Control means for detecting the position of the color image for detecting the image reference position, and correcting the image reference position based on the detected position information of the color image for detecting the image reference position.
[0111]
With this configuration, it is possible to remove a positional shift between a predetermined image reference position in the image forming unit and a writing position of image information of each color for detecting the image reference position formed by the image forming unit. An accurate color misregistration correction mode can be executed in the image forming system after the execution of the image reference position correction mode. Therefore, in the manufacturing process of the apparatus main body, when the image forming means and the image detecting means are assembled for the first time, or when the image forming body is replaced after the sale of the apparatus main body, the image forming means is moved to the image reference position. A reference color image for color shift correction can be formed with high accuracy.
[0112]
The present invention is very suitable when applied to a tandem-type color printer or copying machine having an intermediate transfer belt or a transfer material conveying belt, or a composite machine thereof.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram illustrating a configuration example of a color image forming apparatus 100 as an embodiment according to the invention.
FIG. 2 is a block diagram illustrating a configuration example of an image transfer and image forming system of the color image forming apparatus 100.
FIG. 3 is an image diagram showing a configuration example of an image writing unit 3Y for Y color and a correction unit 5Y thereof.
FIG. 4 is a block diagram illustrating a configuration example of a control system of the color image forming apparatus 100.
FIG. 5 is a perspective view showing an example of detection of a registration mark CR by two registration sensors 12A and 12B.
FIG. 6 is a diagram illustrating an example of forming a registration mark CR for detecting an image reference position.
FIGS. 7A and 7B are diagrams showing an example of binarization of a position detection signal S2 by a registration sensor 12A or the like.
FIG. 8 is a diagram illustrating a relationship example (part 1) between a registration mark CR for detecting an image reference position and a registration sensor 12.
FIGS. 9A and 9B are diagrams illustrating a relationship example (No. 2) between the registration mark CR for detecting an image reference position and the registration sensor 12. FIGS.
FIG. 10 is a diagram showing an example of forming a registration mark CR ′ for color misregistration correction.
FIG. 11 is a flowchart illustrating an example of image formation in the color image forming apparatus 100.
[Explanation of symbols]
1Y, 1M, 1C, 1K Photoconductor drum (image forming body)
2Y, 2M, 2C, 2K Charging means
3Y, 3M, 3C, 3K image writing unit
4Y, 4M, 4C, 4K developing means
5Y, 5M, 5C, 5K correction means
6 Intermediate transfer body (image transfer means)
10Y, 10M, 10C, 10K Image forming unit (image forming means)
12, 12A, 12B registration sensor (image detecting means)
14 Non-volatile memory (storage device)
15 control means
51 Correction calculation unit
57 CPU (control means)
100 color image forming apparatus (image forming apparatus)
101 Image Forming Apparatus Main Body
102 Image reading device
201 Automatic Document Feeder
202 Document Image Scanning Exposure Device

Claims (7)

An image for forming a reference color image for color misregistration correction on an image forming body, reading a passage timing of the reference color image, calculating a misregistration amount of another color image with respect to the reference color image, and correcting an image forming position. In the forming device,
An image forming unit having the image forming body, wherein an image reference position for forming a color image by writing image information to the image forming body is defined in advance;
Image detecting means for detecting a color image formed on the image forming body by the image forming means,
A color image is formed by writing image information of all colors for image reference position detection on the image forming body, and a position of the color image for image reference position detection formed on the image forming body is detected and detected. An image forming apparatus comprising: a control unit configured to correct the image reference position based on position information of the color image for detecting the image reference position. The image forming unit includes:
A plurality of image forming units having an image forming body for each color and forming a toner image of the color on the image forming body;
The image forming apparatus according to claim 1, further comprising: an image transfer unit configured to transfer toner images formed on the plurality of image forming bodies. The image forming unit includes:
One image forming body that forms a color image by superimposing colors;
The image forming apparatus according to claim 1, further comprising a plurality of image forming units that form a color image on the image forming body. When the width direction of the image transfer unit is the main scanning direction,
The color image for image reference position detection,
It is configured by a line segment parallel to the main scanning direction and a line segment having a predetermined angle with respect to the main scanning direction, and is larger in size than the color image for color shift correction. The image forming apparatus according to claim 2, wherein: The control means,
Calculate the amount of displacement between the image reference position and each position of the color image for image reference position detection,
2. The image forming apparatus according to claim 1, wherein the image forming apparatus corrects a writing position of the image information of each color by the image forming unit so as to match the writing position with the image reference position based on the calculated positional shift amount. Forming a reference color image for color shift correction on the image forming body, reading a passage timing of the reference color image, calculating a position shift amount of another color image with respect to the reference color image, and correcting an image forming position. Set the operation to the color misregistration correction mode,
Writing all color image information for image reference position detection on the image forming body to form all color images, detecting the position of the color image for image reference position detection formed on the image forming body, When the operation of correcting the image reference position based on the detected position information of the image reference position detection color image is set to the image reference position correction mode,
The control means,
The image forming apparatus according to claim 1, wherein the image reference position correction mode is executed before executing the color misregistration correction mode. A method of forming a color image on an image forming body based on image information for an arbitrary color,
Forming a reference color image for color shift correction on the image forming body, reading a passage timing of the reference color image, calculating a position shift amount of another color image with respect to the reference color image, and correcting an image forming position. Set the operation to the color misregistration correction mode,
Writing all color image information for image reference position correction to the image forming body to form all color images, and detecting and detecting the position of the color image for image reference position detection formed on the image forming body. When the operation of correcting the image reference position based on the position information of the color image for detecting the image reference position is an image reference position correction mode,
An image forming method comprising: executing the image reference position correction mode before executing the color misregistration correction mode.

Images