JP2012145719A - Image forming apparatus, color shift correction method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus, a color shift correction method and a program that maintain color shift correction accuracy to execute a color shift correction, even when an entire pattern length region cannot be secured on an image carrier due to the existence of a noise source on the image carrier.SOLUTION: The image forming apparatus includes: an intermediate transfer belt 16 to be conveyed; a noise position specification section 509 for specifying the position of the noise source on the intermediate transfer belt 16; a pattern formation section 501 which is means for forming a pattern for a color shift correction for every color in the intermediate transfer belt 16 and for forming the pattern to cover the specified noise source; a reflection type sensor 24 for detecting the pattern formed in the intermediate transfer belt 16; and a color shift correction section 503 for performing the color shift correction based on the detected patterns of each color.

Description

  The present invention relates to an image forming apparatus, a color misregistration correction method, and a program.

  In a technology that draws a correction pattern for each color on an image carrier such as an intermediate transfer belt to correct color misregistration, the correction pattern is drawn avoiding noise sources such as scratches and dirt existing on the image carrier. A technique for obtaining correction pattern read data that is not affected by noise is conventionally known.

  For example, in Patent Document 1, in the image forming apparatus, in order to avoid noise when a noise source such as a scratch or a stain exists on the intermediate transfer member, a home position mark and a home position mark are provided on the intermediate transfer member. Has been disclosed that obtains pattern reading data that is not affected by noise by providing a home position detection sensor for reading the image, storing the position of the noise source on the intermediate transfer member, and drawing a correction pattern while avoiding the noise source. Yes.

  However, in such a conventional technique, there is a problem that when the area of the entire correction pattern cannot be secured due to noise on the image carrier, the color misregistration correction cannot be executed or the accuracy of the color misregistration correction is reduced. is there.

  The present invention has been made in view of the above, and maintains the accuracy of color misregistration correction even when the area of the entire pattern length cannot be secured on the image carrier due to the presence of a noise source on the image carrier. An object of the present invention is to provide an image forming apparatus, a color misregistration correction method, and a program capable of executing color misregistration correction.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention includes a conveyed image carrier, a noise position specifying unit that specifies a position of a noise source on the image carrier, A means for forming a color misregistration correction pattern for each color on the image carrier, the pattern forming means for forming the pattern covering the specified noise source, and the pattern formed on the image carrier. It is characterized by comprising detecting means for detecting and correcting means for correcting color misregistration based on the detected pattern of each color.

  The color misregistration correction method according to the present invention is a color misregistration correction method executed in an image forming apparatus, and includes a noise position specifying step for specifying a position of a noise source on the image carrier, and each color on the image carrier. Forming a pattern for correcting color misregistration for each pattern, the pattern forming step for forming the pattern covering the noise source whose position is specified, and the detecting step for detecting the pattern formed on the image carrier And a correction step of performing color misregistration correction based on the detected pattern of each color.

  The program according to the present invention includes a noise position specifying step for specifying a position of a noise source on the image carrier, and a step for forming a color misregistration correction pattern for each color on the image carrier, wherein the position is specified. A pattern forming step for forming the pattern covering the noise source, a detection step for detecting the pattern formed on the image carrier, and a correction step for correcting color misregistration based on the detected pattern of each color. And make the computer execute.

  According to the present invention, it is possible to perform color misregistration correction while maintaining the accuracy of color misregistration correction even when the entire area of the pattern cannot be secured on the image bearing member due to the presence of a noise source on the image bearing member. There is an effect.

FIG. 1 is a configuration diagram illustrating an example of an image forming unit of an electrophotographic color image forming apparatus. FIG. 2 is a configuration diagram illustrating an example of an image forming unit of an image forming apparatus that directly transfers to a transfer sheet. FIG. 3 is a schematic diagram illustrating an example of the configuration of the reflective sensor. FIG. 4 is a hardware configuration diagram of the color image forming apparatus according to the present embodiment. FIG. 5 is a block diagram showing a functional configuration related to color misregistration correction according to the present embodiment. FIG. 6 is an explanatory diagram of a toner pattern in color misregistration correction control. FIG. 7 is an explanatory diagram when a noise source such as a flaw is detected when the toner pattern is detected. FIG. 8 is an explanatory diagram showing the relationship between the toner pattern and the noise source in the present embodiment. FIG. 9 is an explanatory diagram illustrating an example of the first background detection data. FIG. 10 is an explanatory diagram illustrating an example of second background detection data. FIG. 11 is an explanatory diagram illustrating an example of data obtained by correlation from the first background detection data and the second background detection data. FIG. 12 is a flowchart illustrating a sequence of color misregistration correction processing according to the present embodiment. FIG. 13 is an explanatory diagram of a toner pattern when there are a plurality of noise sources on the intermediate transfer belt.

  Exemplary embodiments of an image forming apparatus, a color misregistration correction method, and a program according to the present invention will be described below in detail with reference to the accompanying drawings.

  The color image forming apparatus according to the present embodiment is generally called a multifunction machine having at least two functions among a copy function, a printer function, a scanner function, and a facsimile function, and converts a document into read image data. An image reading unit that performs image processing on image data obtained by reading an original with the image reading unit, and an image forming unit that forms an image on a paper surface based on the image processed image data Have.

  FIG. 1 is a configuration diagram illustrating an example of an image forming unit of an electrophotographic color image forming apparatus. FIG. 1 shows an example of a tandem color image forming apparatus employing an intermediate transfer member.

  First, the image forming unit includes four photosensitive drums 10Y, 10M, 10C, and 10K and a plurality of developing devices 11Y and 11M that develop the latent images formed on the photosensitive drums into toner images of different colors, respectively. , 11C, 11K, and an intermediate transfer belt 16 as an image carrier that rotates in the direction of arrow A to which toner images of different colors are respectively primary-transferred in an overlapped state.

  The intermediate transfer belt 16 is an endless belt. In this embodiment, black, cyan, magenta, and black are disposed on the upper side of the intermediate transfer belt 16 along the rotation direction A of the intermediate transfer belt 16. The four photosensitive drums 10 for each color of yellow are arranged in parallel. A charging device 12, the developing device 11, the primary transfer roller 14 constituting the primary transfer device, and the cleaning device 13 are disposed around the photosensitive drum 10, respectively.

  The photosensitive drum 10 is rotationally driven in the rotation direction B. At this time, the charging device 12 charges the surface of the photosensitive drum 10 to a predetermined polarity. Next, the charged surface is irradiated with laser light emitted from the exposure device 15, thereby forming an electrostatic latent image on the photosensitive drum 10, and the electrostatic latent image is converted into a toner image of each color by the developing device 11. Visualized.

  A primary transfer roller 14 is disposed opposite to each photoconductor drum 10, and rotates with the intermediate transfer belt 16 sandwiched between each primary transfer roller 14 and the photoconductor drum 10. It has become.

  The intermediate transfer belt 16 is supported by two axes of a driving roller 17 and a tension roller 19. Although it may be stretched by a plurality of rollers, in order to make it as small as possible, in this embodiment, it is stretched by two axes to suppress the height of this unit.

  Next, a toner image visualized on each photosensitive drum 10 is transferred onto the surface of the intermediate transfer belt 16 by the action of the primary transfer roller 14. In this manner, the black, cyan, magenta, and yellow toner images are transferred on the intermediate transfer belt 16 in a state of being sequentially and accurately superimposed, and a full-color composite color image is formed.

  On the other hand, a secondary transfer roller 18 is disposed opposite to the driving roller 17 (secondary transfer counter roller) with the intermediate transfer belt 16 interposed therebetween, and transfer paper P as a recording medium is fed from the paper feed unit 21. Then, it is fed between the driving roller 17 and the secondary transfer roller 18 at a predetermined timing by the rotation of the registration roller pair 22. Then, the composite color image carried on the intermediate transfer belt 16 is collectively transferred onto the transfer paper P by the action of the secondary transfer roller 18.

  The toner image on the transfer paper P is fixed by heat and pressure by the fixing device 23 and is discharged onto a paper discharge tray (not shown). Transfer residual toner adhering to the surface of the intermediate transfer belt 16 after the toner image secondary transfer is removed by the cleaning device 20.

  Although FIG. 1 shows an example of a method of transferring to a transfer paper via a secondary transfer roller, an image forming apparatus of a method of directly transferring to a transfer paper as shown in FIG. 2 may be used.

  Further, in the color image forming apparatus according to the present embodiment, the reflection type sensor 24 as a detection unit is disposed at a certain fixed distance toward the intermediate transfer belt 16. In a tandem color image forming apparatus, in order to obtain a high-quality full-color image, the image density of each color is required to be appropriately stable. For this reason, a toner pattern serving as a density reference is formed on an image carrier such as the intermediate transfer belt 16 (or the conveyance belt), and the density of the toner patch is detected by the optical reflection sensor 24. Based on the density, the image forming conditions such as charging potential, exposure intensity, developing bias voltage, transfer voltage, and toner replenishment amount are fed back.

  In a tandem color image forming apparatus, each mounting error of the image forming unit, adjustment error / distortion / environment and change with time of the exposure apparatus, rotation irregularity of the photosensitive drum, conveyance irregularity of the image carrier / transfer paper A color shift occurs in the formed image due to fluctuations caused by disturbances such as the above. For this reason, in the present embodiment, a toner pattern to be a mark of each color is formed on the image carrier, the position of each color of the toner pattern is detected by the optical reflective sensor 24, and each color is detected from the detection result. The amount of color misregistration is calculated and the adjustment of the exposure timing is fed back.

  FIG. 3 is a schematic diagram illustrating an example of the configuration of the reflective sensor 24. The reflection type sensor 24 is disposed opposite to the intermediate transfer belt 16 as an image carrier, and detects the density of the toner pattern 25 formed on the surface of the intermediate transfer belt 16 and the position of each color.

  The reflective sensor 24 according to the present embodiment includes a light emitting element 241 such as an infrared light emitting diode, phototransistor / photodiode light receiving elements 242 and 243, and a holder 244 that accommodates these elements. Measure the toner density and position.

  The light receiving element 242 detects regular reflection light from the toner pattern 25, and the light receiving element 243 detects diffuse reflection light from the toner pattern 25. Thus, by detecting both regular reflection light and diffuse reflection light, it becomes possible to detect high density from low density of black (K) and color (C, M, Y). On the other hand, in the position detection of each color, detection is performed only by the light receiving element 242 that detects regular reflection light. Here, the detected value of the specularly reflected light varies extremely due to deformation of the image carrier such as the intermediate transfer belt 16.

  FIG. 4 is a hardware configuration diagram of the color image forming apparatus according to the present embodiment. As shown in FIG. 4, the color image forming apparatus according to the present embodiment includes a CPU (Central Processor Unit) 26, an I / O unit 32, an I / F unit 29, a RAM (Random Access Memory) 28, and the like. ROM (Read Only Memory) 27, a counter 31, a flash memory 35 as a storage unit, and a writing unit 30.

  The ROM 27 is a storage medium that stores various control programs. The CPU 26 controls the entire color image forming apparatus according to the present embodiment in accordance with various control programs stored in the ROM 27.

  The flash memory 35 is a storage medium that stores toner density and color misregistration parameters, a toner pattern table, and parameters necessary for various controls. The RAM 28 is a storage medium in which a work area area for overall control of the color image forming apparatus of the present embodiment is secured.

  The I / F unit 29 is an interface such as a wired LAN, a wireless LAN, and a USB, and is connected to an external device by the I / F unit 29. When the I / F unit 29 receives image data from an external device, the writing unit 30 converts the received image data into image signals of Y (yellow), M (magenta), C (cyan), and K (black) colors. And the separated image digital signal is sent to the exposure device 15 in accordance with the toner density and color misregistration parameters stored in the flash memory 35.

  The counter 31 is a counter for counting the toner density formed on the intermediate transfer belt 16, the number of color misregistration detection toner patterns, and the time between color misregistration detection toner patterns.

  In the toner density control and color misregistration control, first, the toner pattern 25 for detecting toner density and color misregistration is transferred to the flash memory 35 via the writing unit 30 and the exposure device 15 while moving the intermediate transfer belt 16 at a constant speed. The toner density and color misregistration information formed on the intermediate transfer belt 16 at the stored timing and detected by the reflection type sensor 24 are input to the I / O unit 32, calculated by the CPU 26 based on the information, and the correction parameters thereof. Is stored in the flash memory 35 and is passed on to the next image forming operation.

  Next, a functional configuration relating to color misregistration correction in the color image forming apparatus of the present embodiment will be described. FIG. 5 is a block diagram showing a functional configuration related to color misregistration correction according to the present embodiment.

  As shown in FIG. 5, the color image forming apparatus according to the present embodiment includes a pattern forming unit 501, a color misregistration correcting unit 503, a background data acquiring unit 505, a reference position calculating unit 507, and a noise position specifying unit 509. And mainly.

  The pattern forming unit 501 forms toner patterns for color misregistration correction for each color of Y, M, C, and K on the intermediate transfer belt 16 in a predetermined order. The pattern forming unit 501 sends a command to form a toner pattern for each color of Y, M, C, and K to the writing unit 30, and the writing unit 30 receives the command and sends the toner to the intermediate transfer belt 16. Write the pattern.

  The color misregistration correction unit 503 performs color misregistration correction based on the toner pattern of each color detected by the reflective sensor 24.

  Hereinafter, toner pattern formation and color misregistration correction according to the present exemplary embodiment will be described in detail. FIG. 6 is an explanatory diagram of a toner pattern in color misregistration correction control. The pattern forming unit 501 draws eight sets of toner patterns in C (cyan), M (magenta), Y (yellow), and K (black) colors at three positions on the intermediate transfer belt 16, thereby causing color misregistration. The correction unit 503 obtains a position shift (color shift) of the color color (C, M, Y) with respect to K. As a specific method of color misregistration correction by the color misregistration correction unit 503, a method disclosed in Japanese Patent Laid-Open No. 2003-98793 is used.

  FIG. 7 is an explanatory diagram when a noise source such as a flaw is detected when the toner pattern is detected. When a noise source 701 such as a scratch exists on the intermediate transfer belt 16, the reflective sensor 24 erroneously recognizes the noise source 701 as a toner pattern, and the color misregistration correction unit 503 differs from the original color misregistration amount. In some cases, the color misregistration amount is calculated, and as a result, an incorrect correction amount is calculated.

  Therefore, in this embodiment, the pattern forming unit 501 specifies the position of the noise source 701 on the intermediate transfer belt 16 and forms a toner pattern so as to cover the noise source 701. FIG. 8 is an explanatory diagram showing the relationship between the toner pattern and the noise source in the present embodiment.

  As shown in FIG. 8, when a noise source 701 such as a scratch exists on the intermediate transfer belt 16, the pattern forming unit 501 draws a toner pattern so as to cover the noise source 701 of the intermediate transfer belt 16. Thus, erroneous detection due to the noise source 701 by the reflective sensor 24 is prevented, and the color misregistration correction unit 503 can execute color misregistration correction without affecting the accuracy.

  In the present embodiment, the pattern forming unit 501 forms a toner pattern that covers the noise source in a direction parallel to the main scanning direction. For example, in the example shown in FIG. 8, when an oblique toner pattern is to be drawn on the noise source 701 of the intermediate transfer belt 16, the position where the reflective sensor 24 reads the oblique toner pattern is the main scan of the oblique toner pattern. This has an effect on deviations in both the direction and the sub-scanning direction. On the other hand, only the color shift in the sub-scanning direction affects the toner pattern parallel to the main scanning direction. In consideration of this point, when covering a noise source such as a scratch, the pattern forming unit 501 is preferably covered with a toner pattern parallel to the main scanning direction.

  In the present embodiment, as described above, since the pattern forming unit 501 forms the toner pattern on the intermediate transfer belt 16 so as to cover the noise source 701, the position of the noise source 701 on the intermediate transfer belt 16 needs to be obtained. There is. In this embodiment, the background data acquisition unit 505, the reference position calculation unit 507, and the noise position specification unit 509 specify the position of the noise source on the intermediate transfer belt 16.

  Returning to FIG. 5, the flash memory 35 stores first background detection data that is background data on the intermediate transfer belt 16 including a noise source in advance. The first background detection data is data obtained in advance by the background data acquisition unit 505 scanning the intermediate transfer belt 16 and measuring the background of the intermediate transfer belt 16 for one turn by the reflective sensor 24. FIG. 9 is an explanatory diagram illustrating an example of the first background detection data. In FIG. 9, the vertical axis represents the output from the reflective sensor 24, and the horizontal axis represents time. In this example, the time required for one rotation of the intermediate transfer belt 16 is 10 [sec]. In the first background detection data shown in FIG. 9, the peak value of the sensor output of the reflective sensor 24 is confirmed around 7.1 [sec] and around 9.0 [sec]. This indicates that noise sources such as scratches exist at a position where 7.1 [sec] has elapsed since the start of detection of the background on the intermediate transfer belt 16 and at a position where 9.0 [sec] has elapsed. Yes.

  The background data acquisition unit 505 is connected to the reflective sensor 24, and scans the intermediate transfer belt 16 from an arbitrary position when the reference position (home position) of the intermediate transfer belt 16 is obtained. Second background detection data, which is data obtained by measuring the background for one rotation of the intermediate transfer belt 16, is acquired. FIG. 10 is an explanatory diagram illustrating an example of second background detection data. In the example of FIG. 10, the peak value of the sensor output of the reflective sensor 24 is confirmed around 4.6 [sec] and around 7.2 [sec]. This indicates that noise sources such as scratches exist at a position where 4.6 [sec] has elapsed since the start of detection of the background on the intermediate transfer belt 16 and a position after 7.2 [sec] has elapsed. Yes.

  The reference position calculation unit 507 calculates the phase difference between the first background detection data and the second background detection data, and calculates the reference position (home position) of the intermediate transfer belt 16 based on the phase difference. Here, the reference position is a reference point for grasping the position of the noise source existing on the intermediate transfer belt 16.

  The reference position calculation unit 507 inputs the cross correlation function to obtain the product of the first background detection data and the convolution data of the second background detection data, and the function value of the cross correlation function becomes the maximum value (correlation peak value). The input value is calculated as a phase difference. Here, the cross-correlation function is a function represented by the equation (1), and is used for examining the similarity between two signals.

（１）式では、一つ目の信号ｆと二つ目の信号ｇの畳み込みを行う。この関数の結果として得られる（ｆ＊ｇ）（ｍ）の相関ピーク値が、２つの信号の重なりが最も大きい箇所となるため、（ｆ＊ｇ）（ｍ）の相関ピーク値に対応するｍの値が２つの信号の位相のずれ量となる。

In the equation (1), the first signal f and the second signal g are convolved. Since the correlation peak value of (f * g) (m) obtained as a result of this function is the place where the overlap of the two signals is the largest, m corresponding to the correlation peak value of (f * g) (m) Is the amount of phase shift between the two signals.

  FIG. 11 shows the data obtained by inputting the first background detection data obtained in advance shown in FIG. 9 and the second background detection data, which is the measurement value shown in FIG. It is explanatory drawing which shows an example. In the example of FIG. 11, a correlation peak value is confirmed around 2.5 [sec]. This indicates that there is a phase difference of 2.5 [sec] between the first background detection data found in advance in FIG. 9 and the second background detection data shown in FIG. ing.

  That is, when it is assumed that the time 0 [sec] in the first background detection data shown in FIG. 9 is the reference position (home position), the reference position calculation unit 507 uses the second background detection data shown in FIG. Since the phase of the intermediate transfer belt 16 is −2.5 [sec] or the time taken for one rotation of the intermediate transfer belt 16 is 10 [sec], it is 10 −2 from the phase of the intermediate transfer belt 16 at the start of measurement. .5 = 7.5 [sec] is determined as the reference position (home position) of the intermediate transfer belt 16.

  Therefore, since the reference position is known as described above, the noise position specifying unit 509 specifies the position of the noise source from the reference position on the intermediate transfer belt 16 obtained by the reference position calculating unit 507 from the background detection data of FIG. can do.

  In this embodiment, the pattern forming unit 501 described above forms a toner pattern so as to cover the noise source at the position of the noise source specified by the noise position specifying unit 509.

  Specifically, the color misregistration correction unit 503 performs color misregistration correction as follows. The color misregistration correction unit 503 obtains a color misregistration amount by comparing data obtained by toner pattern detection and data obtained from an ideal layout, and determines a color misregistration correction correction amount for the color misregistration amount. In this case, the color misregistration correction unit 503 needs to determine the color misregistration amount in accordance with the layout change because the ideal layout is changed.

  For example, the interval between the K patch and the Y patch in FIG. Assuming that an ideal interval between the K patch and the Y patch before the layout change is L_ib and an interval between the K patch and the Y patch as a result of the color misalignment pattern detection before the layout change is L_mb, the color misregistration correction unit 503 The shift amount L_gb is obtained by the following equation (2).

L_gb = L_ib−L_mb (2)
Here, it is assumed that the layout is changed and the interval between the K patch and the Y patch is changed to L_ia = L_ib + ΔL. Assuming that the interval between the K patch and the Y patch as a result of detecting the toner pattern after the layout change is L_ma, the color misregistration correction unit 503 obtains the color misregistration amount L_ga by the following equation (3).

L_ga = L_ia−L_ma = L_ib + ΔL−L_ma (3)
Since L_ib and ΔL are known and L_ma is a result obtained by measurement, the color misregistration correction unit 503 can also determine the color misregistration amount L_ga after the layout change.

  Next, a series of color misregistration correction processing by the image forming apparatus of the present embodiment configured as described above will be described. FIG. 12 is a flowchart illustrating a sequence of color misregistration correction processing according to the present embodiment.

  First, the background data acquisition unit 505 performs background measurement for one turn of the intermediate transfer belt 16 from an arbitrary position on the intermediate transfer belt 16 (step S11), and acquires second background detection data.

  Next, the reference position calculation unit 507 reads the first background detection data stored in advance from the flash memory 35 (step S13). Then, the first background detection data and the measured second background detection data are input to the cross-correlation function of equation (1) to calculate a function value (step S15). Next, the reference position calculation unit 507 obtains a correlation peak value of the calculated function value, and obtains a reference position by using the obtained correlation peak value as a phase difference (step S17).

  Next, the noise position specifying unit 509 specifies the position of the noise source from the reference position of the intermediate transfer belt 16 (step S19).

  Then, the pattern forming unit 501 forms a toner pattern at the position of the noise source (step S21). Thereby, a toner pattern is formed so as to cover the noise source.

  Then, the reflective sensor 24 detects the toner pattern (step S23), and the color misregistration correction unit 503 obtains the color misregistration amount based on the detected toner pattern, and performs the color misregistration correction based on the color misregistration amount ( Step S25).

  As described above, in this embodiment, in the color misregistration correction control, the toner pattern is formed so as to cover the noise source of the intermediate transfer belt 16 and the color misregistration correction is performed. Even when the entire area of the toner pattern cannot be ensured on the image 16, the color misregistration correction can be executed while maintaining the accuracy of the color misregistration correction.

  The examples shown in FIGS. 9, 10, and 11 are examples in which there is a single noise source, but the first background detected in advance even when there are a plurality of noise sources on the intermediate transfer belt 16. By obtaining the correlation between the detection data and the second background detection data obtained by the background measurement, the reference position of the intermediate transfer belt 16 can be obtained by the same method without being complicated.

  FIG. 13 is an explanatory diagram of a toner pattern when a plurality of noise sources are present on the intermediate transfer belt 16. In this manner, when there are a plurality of noise sources 701 and 702 such as scratches on the intermediate transfer belt 16, as shown in the upper part of FIG. The noise source 702 may not be covered with the toner pattern. In this case, since the position of the noise source on the intermediate transfer belt 16 can be determined by the method described with reference to FIGS. 9, 10, and 11, the toner pattern is matched with the noise sources 701 and 702 as shown in the lower part of FIG. By changing the layout, it is possible to cover the plurality of noise sources 701 and 702 with a toner pattern and prevent the noise sources 701 and 702 from being detected.

  Note that the color misregistration correction program executed by the image forming apparatus of the present embodiment is provided by being incorporated in advance in the ROM 27 or the like.

  The color misregistration correction program executed in the image forming apparatus according to the present embodiment is a file in an installable format or an executable format, and is a CD-ROM, flexible disk (FD), CD-R, DVD (Digital Versatile Disk). For example, the program may be recorded on a computer-readable recording medium.

  Furthermore, the color misregistration correction program executed by the image forming apparatus according to the present embodiment may be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. . The color misregistration correction program executed by the image forming apparatus according to the present embodiment may be provided or distributed via a network such as the Internet.

  The color misregistration correction program executed by the image forming apparatus according to the present embodiment includes the above-described units (background data acquisition unit 505, reference position calculation unit 507, noise position specifying unit 509, pattern formation unit 501, and color misregistration correction unit 503. ), And the actual hardware is such that the CPU (processor) reads out the color misregistration correction program from the ROM 27 and executes it, so that the above-described units are loaded onto the main storage device such as the RAM 28, A data acquisition unit 505, a reference position calculation unit 507, a noise position specification unit 509, a pattern formation unit 501, and a color misregistration correction unit 503 are generated on the main storage device.

  In the above embodiment, the image forming apparatus of the present invention has been described by taking an example in which the image forming apparatus is applied to a multifunction machine having at least two functions among a copy function, a printer function, a scanner function, and a facsimile function. Any image forming apparatus having a printing function, such as a printer or a facsimile machine, can be applied.

24 reflective sensor 26 CPU
32 I / O section 29 I / F section 27 ROM
28 RAM
30 Writing unit 35 Flash memory 501 Pattern forming unit 503 Color misregistration correcting unit 505 Background data obtaining unit 507 Reference position calculating unit 509 Noise position specifying unit 701, 702 Noise source

JP 2007-156281 A

Claims (7)

An image carrier to be conveyed;
Noise position specifying means for specifying the position of a noise source on the image carrier;
A means for forming a color misregistration correction pattern for each color on the image carrier, the pattern forming means for forming the pattern covering a specified noise source;
Detecting means for detecting the pattern formed on the image carrier;
Correction means for performing color misregistration correction based on the detected pattern of each color;
An image forming apparatus comprising: Storage means for storing first background detection data which is data on the image carrier including the noise source in advance;
Further comprising background data acquisition means for scanning the image carrier by the detection means and acquiring second background detection data which is data of the image carrier;
The image forming apparatus according to claim 1, wherein the noise position specifying unit specifies the position of the noise source based on the first background detection data and the second background detection data. A reference position calculating means for obtaining a phase difference between the first background detection data and the second background detection data and calculating a reference position of the image carrier based on the phase difference;
The image forming apparatus according to claim 2, wherein the noise position specifying unit specifies a position of the noise source from the reference position.   The reference position calculation means inputs a cross-correlation function for obtaining a product of the first background detection data and the convolution data of the second background detection data, and inputs an input value that maximizes the function value of the cross-correlation function. The image forming apparatus according to claim 3, wherein the image forming apparatus calculates the phase difference. The pattern forming means, when there are a plurality of the noise source in the image carrier, the pattern is formed by changing according to the interval of the noise source,
The image forming apparatus according to claim 1, wherein the correction unit performs the color misregistration correction according to a change amount. A color misregistration correction method executed in an image forming apparatus,
A noise position specifying step for specifying a position of a noise source on the image carrier;
Forming a pattern for color misregistration correction for each color on the image carrier, the pattern forming step forming the pattern covering the noise source whose position is specified;
A detection step of detecting the pattern formed on the image carrier;
A correction step of performing color misregistration correction based on the detected pattern of each color;
A color misregistration correction method comprising: A noise location step for identifying the location of the noise source on the image carrier;
Forming a pattern for color misregistration correction for each color on the image carrier, the pattern forming step forming the pattern covering the noise source whose position is specified;
A detection step of detecting the pattern formed on the image carrier;
A correction step of performing color misregistration correction based on the detected pattern of each color;
A program that causes a computer to execute.

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