JP4949087B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method for performing control for aligning image positions when forming images of a plurality of colors.

  Conventionally, in a color image forming apparatus, a plurality of basic color images are superimposed to form a color image. For this reason, if the image position of each basic color shifts, the color of line drawings and characters changes, or image unevenness (color unevenness) occurs, leading to a decrease in image quality. Therefore, it is necessary to match the image positions of the basic colors as much as possible.

  For this reason, conventionally, in an image forming apparatus for forming a color image, a means for correcting a positional deviation between basic colors caused by various factors such as a change in environmental temperature and a change in temperature in the apparatus is disclosed. ing.

  As an example of such a prior art, there is one that forms a color misregistration detection pattern on a transfer belt and detects and corrects an inclination based on the results detected by a plurality of detection means (see Patent Document 1). . As another conventional technique, there is a technique in which a color misregistration detection pattern is formed on a transfer belt and color misregistration is corrected based on the results detected by a plurality of detection means (see Patent Document 2). As another conventional technique, there is a technique in which a color misregistration detection pattern is formed on a transfer belt and color misregistration is corrected based on the results detected by a plurality of detection means (see Patent Document 3).

In each of the techniques described in the above patent documents, a color misregistration detection pattern is formed on a transfer belt and detected by a sensor, so that a misregistration amount between basic colors (for example, magnification in the main scanning direction, main scanning) , Sub-scanning resist) is detected. Based on this deviation amount, the deviation between the basic colors is corrected by correcting the formation position of each basic color. As a result, not only environmental changes but also misregistration due to changes over time can be corrected, and a high-quality image without color misregistration can be obtained.
Japanese Patent No. 3569392 JP 2000-112205 A JP 2004-295083 A

  However, in the conventional image forming apparatus, since a pattern for correcting the image misalignment is formed on the transfer belt and detected by the sensor, the longer the number of patterns detected by one sensor, the longer the correction takes. become. Since there is a demand for the user to reduce the waiting time, it is necessary to suppress a decrease in the total printing speed.

  Further, in a conventional image forming apparatus, a pattern for correcting image misregistration is formed on a transfer belt during continuous printing, and correction is performed. For this reason, it is necessary to form an image misregistration correction pattern between the print image and the next print image (between sheets). Therefore, there is a restriction on the area where the pattern can be formed. Since it is possible to secure a large number of areas by extending the space between the sheets, it is possible to generate a large number of patterns, but on the other hand, the printing speed is reduced.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and an image forming method capable of correcting image displacement in a short time without degrading image quality.

  Further, the present invention corrects image misalignment in a short time without degrading the image quality and reducing the printing speed in continuous printing even when two or more images are continuously formed. An object of the present invention is to provide an image forming apparatus and an image forming method.

  It is another object of the present invention to provide an image forming apparatus and an image forming method capable of improving the accuracy of image displacement correction and correcting a magnification error in the main scanning direction.

The present invention is an image forming apparatus that has a plurality of image forming means for forming a single color image for each color, and forms a multicolor image by superimposing single color images formed by the plurality of image forming means. When image formation is continuously performed on two or more recording media, a forming unit that forms a predetermined image misregistration correction pattern for each color between the recording media, and the image formed by the forming unit A plurality of detection means arranged in the main scanning direction for detecting an image positional deviation correction pattern of a reference color and an image positional deviation correction pattern of a predetermined color for the positional deviation correction pattern, and the detection means on the basis of the detection result, have a, and correcting means for correcting an image positional shift between the predetermined one color of two colors with respect to the reference color, is detected by a plurality of said detecting means The image misregistration correction pattern is a group including a plurality of the image misregistration correction patterns, and the predetermined one color is included in each of a plurality of groups different from each other in the main scanning direction. When the groups are different, the predetermined one color detected by each of the detection means is different .

Further, the present invention forms a latent image by irradiating image light corresponding to image data on a rotating or moving image carrier, and visualizes the latent image with a developing unit. The transferred image is transferred onto a recording medium conveyed by a transfer means that rotates or moves, or the image transferred to the transfer means after being transferred to the transfer means is transferred onto the recording medium. A plurality of image forming units for forming a single color image on a recording medium are provided for each color, and the single color images formed by the image forming unit are superimposed on the recording medium to form a multicolor image on the recording medium. In the image forming apparatus, when image formation is continuously performed on two or more recording media, a predetermined image misregistration correction pattern for each color is provided between the images transferred to the transfer unit. And forming means for forming on, per the image position shift correction patterns formed by said forming means, for detecting the reference color image misregistration correcting patterns with a predetermined one color image misregistration correcting patterns, a plurality of detecting means arranged in the main scanning direction, based on said detection means detecting result detected by a correction means that to correct the image position shift between the predetermined one color of two colors with respect to the reference color, have a mutual the image position deviation correction pattern detected by each of a plurality of said detecting means is a group including a plurality of said image misregistration correcting patterns, said predetermined one color in the main scanning direction Are included in each of a plurality of different groups, and when the groups are different, the predetermined one color detected by each of the detection means is different .

Further, the present invention, in the above invention, further comprises a variable means for varying the formation position of the image displacement correction pattern, the detection means detects the image displacement correction pattern for each color, The correction unit corrects an image position shift between the two colors based on a detection result detected by the detection unit.

Further, the present invention is characterized in that, in the above invention, the variable means varies the formation position of the image positional deviation correction pattern every time the detecting means detects the image positional deviation between the two colors. To do.

The present invention also relates to an image forming method for forming a multicolor image by forming a plurality of single-color images for each color and superimposing the formed single-color images, and forming an image on two or more recording media. Are performed continuously, a forming step of forming a predetermined image misregistration correction pattern for each color between the recording media, and a reference color of the image misregistration correction pattern formed in the forming step. A detection step of detecting an image misregistration correction pattern and a predetermined one color image misregistration correction pattern by a plurality of detection means arranged in the main scanning direction, and based on the detection result of the detection step, There rows and correcting step, the correcting an image positional shift between two colors of the predetermined one color with respect to the reference color, the image position deviation correction path detected by each of a plurality of said detecting means Is a group including a plurality of image misregistration correction patterns, and the predetermined one color is included in each of a plurality of groups different from each other in the main scanning direction. The predetermined one color detected by each of the detecting means is different .

Further, the present invention forms a latent image by irradiating image light corresponding to image data on a rotating or moving image carrier, and visualizes the latent image with a developing unit. The transferred image is transferred onto a recording medium conveyed by a transfer means that rotates or moves, or the image transferred to the transfer means after being transferred to the transfer means is transferred onto the recording medium. An image forming method for forming a plurality of single color images for each color on a recording medium, and superimposing the formed single color images on the recording medium to form a multicolor image on the recording medium. In the case where image formation is continuously performed on a recording medium, a forming step of forming a predetermined image positional deviation correction pattern for each color between the images transferred to the transfer unit on the transfer unit, and the forming step In shape Per the image position deviation correction patterns, and the reference color image misregistration correcting patterns with a predetermined one color image misregistration correcting patterns are detected at a plurality of detecting means arranged in the main scanning direction detected a method, based on the detection result of the detecting step, have rows, and a correction step that to correct the image position shift between two colors of the predetermined one color relative to the reference color, detected by a plurality of said detecting means The image misregistration correction pattern is a group including a plurality of image misregistration correction patterns, and the predetermined one color is included in each of a plurality of groups different from each other in the main scanning direction. When the groups are different, the predetermined one color detected by each of the detection means is different .

Further, the present invention, in the above invention, further comprises a variable step of changing the formation position of the image displacement correction pattern, wherein the detection step detects the image displacement correction pattern for each color, The correcting step corrects an image position shift between the two colors based on a detection result of the detecting step.

Further, the present invention is characterized in that, in the above-mentioned invention, in the variable step, the formation position of the image misregistration correction pattern is varied each time the image misregistration between the two colors is detected in the detection step. To do.

  According to the present invention, it is possible to perform image displacement correction in a short time without degrading image quality.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  As a first embodiment of the present invention, FIG. 1 shows a four-drum type color image forming apparatus. This image forming apparatus forms a color image by superimposing four basic colors of yellow (Y), magenta (M), cyan (C), and black (Bk). For this reason, the image forming apparatus includes an image forming unit 101 and a light beam scanning device 15 for each basic color. The image forming unit 101 includes a charger 7, a transfer unit 8, a developing unit 9, and a photoreceptor 10. In addition, although not shown, a cleaning unit and a charge removal unit are also included. Since the detailed configuration of the image forming unit 101 is not an essential part of the present invention, further detailed description is omitted. In this image forming unit 101, an image may be formed and fixed on the recording paper 5 by a known electrophotographic process. The light beam scanning device 15 includes an LD unit 11, a polygon mirror 14, an FΘ lens 13, and a BTL 12.

  In this image forming apparatus, an image of the Y color is formed on the recording paper 5 conveyed in the direction of the arrow by the transfer belt 6, and then the four colors are transferred by transferring the image in the order of the M, C, and Bk colors. Is formed on the recording paper 5. Then, the image on the recording paper 5 is fixed by a fixing device (not shown).

  The image forming apparatus also includes sensors (sensor 1, sensor 2, sensor 3) for detecting an image misalignment correction pattern. Each sensor 1, 2, 3 detects an image misregistration correction pattern on the transfer belt 6.

Hereinafter, the light beam scanning device 15 will be described. The LD in the LD unit 11 is driven by the drive signal modulated based on the image data. The light beam emitted from the LD is converted into a parallel light beam by a collimating lens (not shown). The parallel light beam exits the LD unit 11, passes through a cylinder lens (not shown), and reaches the polygon mirror 14. The polygon mirror 14 is rotated by a polygon motor (not shown), and the light beam is deflected here and reaches the FΘ lens 13. The light beam that has passed through the FΘ lens 13 passes through the BTL 12 and scans the surface of the photoreceptor 10. Here, BTL is an abbreviation for barrel, toroidal lens, and is provided for position correction (for example, surface tilt correction) in the sub-scanning direction. The direction in which the light beam scans the photoconductor is the direction from sensor 1 to sensor 3 shown in FIG. Since the detailed configuration of the light beam scanning apparatus is not an essential part of the present invention, further detailed description is omitted.

  FIG. 2 shows the image formation control unit 100 and the light beam scanning device 15 in the image forming apparatus of this embodiment. A synchronization detection sensor 16 for detecting the light beam is provided at the image writing side end of the main scanning of the light beam scanning device 15. The light beam that has passed through the fθ lens 13 is reflected by the mirror 18, collected by the lens 17, and enters the synchronization detection sensor 16.

  When the light beam is incident on the synchronization detection sensor 16, the synchronization detection signal XDETP is output from the synchronization detection sensor 16. XDETP is sent to the pixel clock generation unit 28, the synchronization detection lighting control unit 22, and the writing start position control unit 20.

  The pixel clock generation unit 28 receives the synchronization detection signal XDETP and generates a pixel clock PCLK synchronized with the synchronization detection signal XDETP. The pixel clock CLK is sent to the LD control unit 21 and the synchronization detection lighting control unit 22.

  The pixel clock generator 28 includes a reference clock generator 25, a VCO (Voltage Controlled Oscillator) clock generator 24, and a phase-synchronized clock generator 23. As shown in FIG. 3, in the VCO clock generator 24 (PLL circuit: Phase Locked Loop), the reference clock signal FREF from the reference clock generator 25 and VCLK are divided by N by the 1 / N divider 32. A signal is input to the phase comparator 29. The phase comparator 29 compares the phases of the falling edges of both signals and outputs an error component at a constant current. From this error component, unnecessary high frequency components and noise are removed by an LPF (low-pass filter) 30 and sent to the VCO 31. The VCO 31 outputs an oscillation frequency that depends on the output of the LPF 30. Accordingly, the frequency of VCLK can be varied by varying the frequency of FREF and the frequency division ratio: N from the printer control unit 26 of FIG. The printer control unit 26 is connected to the polygon motor control unit 19, the writing start position control unit 20, the LD control unit 21, the synchronization detection lighting control unit 22, and the pixel clock generation unit 28. give.

  The phase-synchronized clock generator 23 generates the above-described pixel clock PCLK from VCLK set to a frequency that is eight times the pixel clock frequency. Therefore, changing the frequency of VCLK changes the frequency of PCLK.

  The synchronization detection lighting control unit 22 first turns on the LD forced lighting signal BD to forcibly light the LD in order to detect the synchronization detection signal XDETP. After the synchronization detection signal XDETP is once detected, the LD is turned on at a timing at which the synchronization detection signal XDETP can be reliably detected by the synchronization detection signal XDETP and the pixel clock PCLK without generating flare light. When the synchronization detection lighting control unit 22 detects the synchronization detection signal XDETP, the synchronization detection lighting control unit 22 generates an LD forcible lighting signal BD for turning off the LD, and sends it to the LD control unit 21.

The LD control unit 21 controls lighting of the laser diode in the LD unit 11 according to the image data synchronized with the synchronous detection forced lighting signal BD and the pixel clock PCLK. As a result, the laser beam emitted from the LD unit 11, as described above, the Rukoto to scan the photoconductor 10.

  The polygon motor control unit 19 controls the rotation of a polygon motor (not shown) at a specified number of rotations based on a control signal from the printer control unit 26.

  The writing start position control unit 20 is based on the synchronization detection signal XDETP, the pixel clock PCLK, the control signal from the printer control unit 26, etc., and the main scanning gate signal XLGATE for determining the image writing start timing and the image width, and the sub scanning. A gate signal XFGATE is generated.

  Outputs of the sensors 1, 2, and 3 for detecting the image misregistration correction pattern are sent to the printer control unit 26. The printer control unit 26 calculates the amount of positional deviation based on the outputs of these sensors, and generates correction data. The correction data is stored in the correction data storage unit 27.

  The correction data storage unit 27 stores correction data for correcting image position deviation and magnification deviation, that is, data for determining the timing of the XLGATE and XFGATE signals, and data for determining the frequency of the pixel clock PCLK. These data are given to each control unit according to an instruction from the printer control unit 26.

  FIG. 4 shows the configuration of the writing start position control unit 20. The writing start position control unit 20 includes a main scanning line synchronization signal generation unit 33, a sub scanning gate signal generation unit 34, and a main scanning gate signal generation unit 35. The main scanning line synchronization signal generation unit 33 is supplied with XDETP and PCLK, and operates the main scanning counter 39 in the main scanning gate signal generation unit 35 and the sub scanning counter 36 in the sub scanning gate signal generation unit 34. A signal XLSYNC is generated. XLSYNC is generated in synchronization with PCLK when XDETP occurs. The sub-scanning gate signal generator 34 generates a signal XFGATE that determines the image signal capture timing (image writing timing in the sub-scanning direction). The main scanning gate signal generator 35 generates a signal XLGATE that determines the image writing timing of the image signal in the main scanning direction.

  The main scanning gate signal generation unit 35 compares the main scanning counter 39 operating with XLSYNC and PCLK, the counter value of the main scanning counter 39 and the correction data (setting value 1) from the printer control unit 26, and the result And a gate signal generation unit 41 that generates XLGATE from the comparison result from the comparator 40.

  The sub-scanning gate signal generation unit 34 includes a control signal from the printer control unit 26, a sub-scanning counter 36 that operates in accordance with XLSYNC and PCLK, a counter value of the sub-scanning counter 36, and correction data (setting value) from the printer control unit 26. 2) and a comparator 37 that outputs the result, and a gate signal generator 38 that generates XFGATE from the comparison result from the comparator 37.

  The writing start position control unit 20 can correct the writing position in units of one cycle of the clock PCLK for main scanning, that is, in units of one dot, and for sub-scanning in units of one cycle of XLSYNC, that is, in units of one line. For both main scanning and sub-scanning, correction data is stored in the correction data storage unit 27.

  FIG. 5 is a timing chart for explaining the operation of the writing start position control unit 20. When the synchronization detection signal XDETP is generated, the write timing signal XLSYNC is generated at a timing synchronized with the pixel clock PCLK. The value of the main scanning counter 39 is reset by this XLSYNC. The value of the main scanning counter 39 is counted up by the pixel clock PCLK. The comparator 40 compares the value of the main scanning counter 39 with the correction data set by the printer control unit 26, that is, the set value 1. As a result of this comparison, when the value of the main scanning counter 39 becomes equal to the set value 1 (here, X), the comparator 40 changes XLGATE to the L level. Thus, XLGATE is a signal that is set to L by the image width in the main scanning direction, and is a signal that determines an image area in the main scanning direction. The write timing signal XLSYNC is also supplied to the sub-scanning gate signal generation circuit 34.

  FIG. 18 is a timing chart for explaining the operation of the writing start position control unit 20 in the sub-scanning direction. In the sub-scanning gate signal generation circuit 34, the value of the sub-scanning counter 36 is reset by a control signal (image writing start trigger signal) from the printer control unit 26. The value of the sub-scanning counter 36 is counted up by the write timing signal XLSYNC. The comparator 37 compares the value of the sub-scanning counter 36 with the correction data set by the printer control unit 26, that is, the set value 2. As a result of this comparison, when the value of the sub-scanning counter 36 becomes equal to the set value 2 (here, Y), the comparator 38 changes XFGATE to the L level. Thus, XFGATE is a signal that is L (valid) by the image width in the sub-scanning direction, and is a signal that determines an image area in the sub-scanning direction.

  With reference to FIG. 6, a configuration for creating image data given to the image formation control unit 100 will be described. That is, the line memory 30 is arranged in the preceding stage of the image formation control unit 100. The line memory 30 further stores image data provided from the preceding printer controller, frame memory, and scanner (none of which are shown). This storage (for image data) is performed in synchronization with XFGATE. The image data stored in the line memory 30 is read out in synchronization with the pixel clock PCLK while XLGATE is L. The image data read out in this way is given to the LD control unit 21 of the image formation control unit 100.

  FIG. 7 shows an image misregistration correction pattern formed on the transfer belt. As shown in FIG. 7, horizontal line and oblique line images are formed at a preset timing for each color as an image misregistration correction pattern. For the sensor 1, the horizontal line pattern Bk1, the horizontal line pattern C1, the diagonal line pattern Bk4, and finally the diagonal line pattern C2 are formed. For the sensor 2, the horizontal line pattern Bk2, the horizontal line pattern M1, the diagonal line pattern Bk5, and finally the diagonal line pattern M2 are formed. For the sensor 3, the horizontal line pattern Bk3, the horizontal line pattern Y1, the diagonal line pattern Bk6, and finally the diagonal line pattern Y2 are formed. In FIG. 7, when the transfer belt 6 moves in the direction of the arrow, horizontal lines and diagonal lines of each color are detected by the sensors 1, 2, and 3. The output of each sensor is sent to the printer control unit 26, and the printer control unit 26 calculates the shift amount (time) of each color with respect to the reference color BK. With respect to the oblique line, the detection timing is changed by shifting the image position and image magnification in the main scanning direction. With respect to the horizontal line, the detection timing is changed by shifting the image position in the sub-scanning direction.

Specifically, for the image position in the main scanning direction, the sensor 1 uses the time from the time when the pattern BK1 is detected to the time when the pattern BK4 is detected: TBK14 as a reference. This value is compared with the time TC12 when the pattern C2 is detected from the time when the pattern C1 is detected. The difference obtained from this comparison: TBK14-TC12 is the image shift of the cyan image from the black image. In order to correct this image shift, the timing of the XLGATE signal that determines the writing start timing is changed by an amount corresponding to the difference. For example, when TC12 is smaller than TBK14, the pattern C2 is formed to be shifted to the left side of the drawing. In this case, the XLGATE signal related to C2 may be delayed. On the contrary, when TC12 is larger than TBK14, the pattern C2 is formed to be shifted to the right side of the drawing. In this case, the XLGATE signal related to C2 may be advanced .

  In the sensor 2, the time from the time when the pattern BK2 is detected to the time when the pattern BK5 is detected: TBK25 is used as a reference. This value is compared with the time TM12 when the pattern M2 is detected after the pattern M1 is detected. The difference obtained from this comparison: TBK25-TM12 is the image shift of the magenta image from the black image. In order to correct this image shift, the timing of the XLGATE signal that determines the writing start timing is changed by an amount corresponding to the difference.

  In the sensor 3, the time from the time when the pattern BK3 is detected to the time when the pattern BK6 is detected: TBK36 is used as a reference. This value is compared with the time TY12 when the pattern Y2 is detected from the time when the pattern Y1 is detected. The difference obtained from this comparison: TBK36-TY12 is the image shift of the yellow image from the black image. In order to correct this image shift, the timing of the XLGATE signal that determines the writing start timing is changed by an amount corresponding to the difference.

  Hereinafter, correction in the sub-scanning direction will be described. For example, in the sensor 1, the time difference of C1 with respect to BK1 is compared with the reference value. The timing of the XFGATE signal for determining the writing start timing is changed by the amount of deviation with respect to the amount of deviation obtained as a result of this comparison.

Specifically, the sensor 1 compares the time: TBK1C1 from the time when the pattern BK1 is detected to the time when the pattern C1 is detected with the reference value: To. The difference obtained from this comparison: TBK1C1-To is the image shift of the cyan image from the black image. In order to correct this image shift, the timing of the XFGATE signal that determines the writing start timing is changed by an amount corresponding to the difference. For example, when To is smaller than TBK1C1, the pattern C1 is formed so as to be shifted to the lower side of the drawing. In this case, it is Re Ya by advancing the XFGATE signal relating C1. Conversely, when To is larger than TBK1C1, the pattern C1 is formed so as to be shifted to the upper side in the drawing. In this case, it is Re delayed XFGATE signal relating C1.

  Further, in the sensor 2, the time: TBK2M1 from the time when the pattern BK2 is detected to the time when the pattern M1 is detected is compared with the reference value: To. The difference obtained from this comparison: TBK2M1-To is the image shift of the magenta image from the black image. In order to correct this image shift, the timing of the XFGATE signal that determines the writing start timing is changed by an amount corresponding to the difference.

  The sensor 3 compares the time TBK3Y1 from the time when the pattern BK3 is detected to the time when the pattern Y1 is detected with the reference value To. The difference obtained from this comparison: TBK3Y1-To is the image shift of the yellow image from the black image. In order to correct this image shift, the timing of the XFGATE signal that determines the writing start timing is changed by an amount corresponding to the difference.

  FIG. 8 shows an image misalignment correction flow. First, in step S <b> 1, the printer control unit 26 reads out various correction data stored in the correction data storage unit 27. Then, the correction data is given to each unit of the image formation control unit 100. Next, in step S <b> 2, the printer control unit 26 instructs the image formation control unit 100 and the light beam scanning device 15 to form the image misregistration correction pattern shown in FIG. 7 on the transfer belt 6. In step S <b> 3, the sensor 1 to sensor 3 detects an image misregistration correction pattern on the transfer belt 6. The output of each sensor is given to the printer control unit 26. In step S4, the printer control unit 26 calculates the amount of misregistration of other colors with respect to the reference color (Bk in this embodiment). Next, in step S5, the printer control unit 26 determines whether or not to perform misregistration correction for each color. If the shift amount of each color is 1/2 or more of the correction resolution, it is determined that the positional shift correction is performed.

  If the printer control unit 26 determines in step S5 that correction of misalignment is to be performed, it calculates a correction amount in the next step S6, and stores this value in the correction data storage unit 27 in step S7. The correction amount in this step is a correction amount related to the XLGATE signal that determines the image position in the main scanning direction and a correction amount related to the XFGATE signal that determines the image position in the sub-scanning direction. If the printer control unit 26 determines in step S5 that no misregistration correction is to be performed, this flow ends.

  When the image forming operation is performed after the above-described image misregistration correction operation is completed, the printer control unit 26 sets the correction data stored in the correction data storage unit 27 in each control unit and sets the image. Will form.

  In the present embodiment, horizontal line and oblique line image misalignment correction patterns are used, but the patterns are not limited to these.

  As described above, according to the image forming apparatus and the image forming method of the present embodiment, each sensor detects only the reference color and another one color pattern, so that the detection time can be reduced. Therefore, it is possible to correct the image misalignment in as short a time as possible and reduce the waiting time. Further, correction control can be simplified.

  The second embodiment of the present invention will be described below. In this embodiment, the configurations of the image forming apparatus, the light beam scanning apparatus, and the image forming control unit are the same as those in the first embodiment.

 FIG. 9 shows an image misregistration correction pattern formed on the transfer belt 6 in the second embodiment. The detection of the amount of misalignment and the method of misalignment correction performed using this pattern are the same as those described in the first embodiment. In FIG. 9, three groups of patterns of group 1, group 2, and group 3 are formed on the transfer belt 6.

  In group 1, a horizontal line pattern Bk1, a horizontal line pattern C1, then a diagonal line pattern Bk4, and finally a diagonal line pattern C2 are formed for the sensor 1. A horizontal line pattern Bk2 and a horizontal line pattern M1 are formed for the sensor 2. An oblique line pattern is not formed for the sensor 2. For the sensor 3, the horizontal line pattern Bk3, the horizontal line pattern Y1, the diagonal line pattern Bk6, and finally the diagonal line pattern Y2 are formed.

  In the group 2, the horizontal line pattern Bk7, the horizontal line pattern M3, the diagonal line pattern Bk10, and finally the diagonal line pattern M4 are formed for the sensor 1. A horizontal line pattern Bk8 and a horizontal line pattern Y3 are formed for the sensor 2. For the sensor 3, a horizontal line pattern Bk9, a horizontal line pattern C3, an oblique line pattern Bk12, and finally an oblique line pattern C4 are formed.

  In group 3, a horizontal line pattern Bk13, a horizontal line pattern Y5, a diagonal line pattern Bk16, and finally a diagonal line pattern Y6 are formed for the sensor 1. A horizontal line pattern Bk 14 and a horizontal line pattern C 5 are formed for the sensor 2. For the sensor 3, a horizontal line pattern Bk15, a horizontal line pattern M5, an oblique line pattern Bk18, and finally an oblique line pattern M6 are formed.

  In group 1, the sensor 1 detects the displacement of the cyan image with respect to Bk as the reference color. The sensor 2 detects a misalignment of the magenta image. Then, the sensor 3 detects a positional shift of the yellow image. In group 2, the sensor 1 detects a positional shift of the magenta image. The sensor 2 detects the position shift of the yellow image. Then, the sensor 3 detects the displacement of the cyan image. In group 3, a yellow image misalignment is detected by sensor 1. The sensor 2 detects the displacement of the cyan image. Then, the sensor 3 detects the misalignment of the magenta image.

  As for correction in the sub-scanning direction, an XFGATE signal that calculates an average value of deviation amounts with respect to the black images detected by the sensor 1, sensor 2, and sensor 3 for each color and determines the writing start timing corresponding to the amount. Change the timing. For example, for cyan, the deviation of group 1 detected by sensor 1: TBK1C1-To, the deviation of group 3 detected by sensor 2: TBK14C5-To, and the deviation of group 2 detected by sensor 3: TBK9C3 -To average value: The timing of the XFGATE signal for determining the writing start timing is changed by an amount corresponding to ((TBK1C1-To) + (TBK14C5-To) + (TBK9C3-To)) / 3.

  For the image writing position correction in the main scanning direction, the timing of the XLGATE signal that determines the writing start timing is changed for each color by an amount corresponding to the amount of deviation from the black image detected by the sensor 1. The displacement is detected in group 1 for cyan, group 2 for magenta, and group 3 for yellow. The detection of the shift amount is the same as that in the first embodiment.

  For magnification correction in the main scanning direction, the result detected by the sensor 1 and the result detected by the sensor 3 are used for each color. For example, for cyan, the time from the time when BK1 of group 1 detected by sensor 1 is detected to the time when BK4 is detected: TBK14 and the time from when C1 is detected to the time when C2 is detected: TC12 are compared. The difference: TBK14-TC12 is obtained. Further, the time TBK912 from the time when the BK9 of the group 2 detected by the sensor 3 is detected to the time BK12 is detected is compared with the time TC34 from the time when the C4 is detected from the time C3 is detected, and the difference TBK912 is compared. -Calculate TC34. Further, the obtained TBK912-TC34 and TBK14-TC12 are compared, and the difference: (TBK9122-TC34)-(TBK14-TC12) is obtained. This difference is a magnification error of the cyan image with respect to the black image. In order to correct this magnification error, the pixel clock frequency for determining the image magnification is changed by an amount corresponding to the difference.

  Since the image position in the main scanning direction also changes due to the change of the pixel clock frequency, it is preferable to determine the correction amount of the image writing position in the main scanning direction in consideration of the change.

  FIG. 10 shows an image misalignment correction flow according to the present embodiment. The basic operation of the image misalignment correction flow according to the present embodiment is the same as that of the first embodiment, but the correction amount is calculated after the detection of all the groups (groups 1, 2, 3) is completed. Only the difference is. That is, in step S11, the printer control unit 26 provides each correction data to each unit of the image formation control unit 100 in the same manner as in step S1, and then in step S12, the image formation control unit 100 and the light beam scanning device. 15, a group 1 image misregistration correction pattern shown in FIG. 9 is formed on the transfer belt 6. In step S <b> 13, the sensor 1 to sensor 3 detects a group 1 image misregistration correction pattern on the transfer belt 6. The output of each sensor is given to the printer control unit 26. In step S14, the printer control unit 26 calculates the misregistration of other colors with respect to the reference color (Bk in this embodiment). Similarly, in step S15, the printer control unit 26 forms an image misregistration correction pattern of group 2 on the transfer belt 6 by the image formation control unit 100 and the light beam scanning device 15, and in step S16, the sensor 1 to the sensor 3 detects the image misregistration correction pattern of the group 2 and calculates the misregistration in step S17. Finally, the printer control unit 26 calculates the positional deviation due to the detection of the image positional deviation correction pattern of the group 3 by the processes in steps S18 to S20. Subsequent operations (steps S21 to S23) are the same as the operations of the first embodiment (steps S5 to S7 in FIG. 8).

  As described above, according to the image forming apparatus and the image forming method of the present embodiment, each sensor detects a positional shift with respect to a reference color of a different color for each group of group 1, group 2, and group 3. It is possible to improve the correction accuracy and correct not only the main scanning and sub-scanning position correction but also the magnification error in the main scanning direction.

  The third embodiment of the present invention will be described below. In this embodiment, the configurations of the image forming apparatus, the light beam scanning apparatus, and the image forming control unit are the same as those in the first embodiment.

  FIG. 11 shows an image misregistration correction pattern formed on the transfer belt 6 in the third embodiment. The detection of the amount of misalignment performed using this pattern and the method of misalignment correction are the same as those described in the second embodiment. In FIG. 11, two groups of patterns of group 1 and group 2 are formed on the transfer belt 6.

  In group 1, a horizontal line pattern Bk1, a horizontal line pattern C1, then a diagonal line pattern Bk4, and finally a diagonal line pattern C2 are formed for the sensor 1. For the sensor 2, a horizontal line pattern Bk2, a horizontal line pattern M1, a diagonal line pattern Bk5, and finally a diagonal line pattern M2 are formed. For the sensor 3, the horizontal line pattern Bk3, the horizontal line pattern Y1, the diagonal line pattern Bk6, and finally the diagonal line pattern Y2 are formed.

  In the group 2, the horizontal line pattern Bk7, the horizontal line pattern M3, the diagonal line pattern Bk10, and finally the diagonal line pattern M4 are formed for the sensor 1. For the sensor 2, a horizontal line pattern Bk8, a horizontal line pattern Y3, an oblique line pattern Bk11, and finally an oblique line pattern Y4 are formed. For the sensor 3, a horizontal line pattern Bk9, a horizontal line pattern C3, an oblique line pattern Bk12, and finally an oblique line pattern C4 are formed.

  In group 1, the sensor 1 detects the displacement of the cyan image with respect to Bk as the reference color. The sensor 2 detects a misalignment of the magenta image. Then, the sensor 3 detects a positional shift of the yellow image. In group 2, the sensor 1 detects a positional shift of the magenta image. The sensor 2 detects the position shift of the yellow image. Then, the sensor 3 detects the displacement of the cyan image.

The correction in the sub-scanning direction and the image writing position correction in the main scanning direction are the same as in the second embodiment. Regarding the magnification correction for main scanning, each color is corrected based on the detection results of the two sensors. However, unlike the second embodiment, detection is performed by a sensor different in each color. In the present embodiment, cyan is the same as in the second embodiment, but for example, magenta is different from the second embodiment. Specifically, the time from the time of detecting BK2 of the group 1 detected by the sensor 2 to the time of detecting BK5: TBK25 and the time from the time of detecting M1 to the time of detecting M2: TM12, The difference: TBK25-TM12 is obtained. Also, the time from the time when the BK7 of the group 2 detected by the sensor 1 is detected to the time when the BK10 is detected: TBK710 and the time from the time when the M3 is detected to the time when the M4 is detected: TM34 are compared, and the difference: Obtain TBK710-TM34. Further, the obtained TBK25-TM12 and BK710-TM34 are compared, and the difference: (TBK25-TM12)-(TBK710-TM34) is obtained. Then, the pixel clock frequency that determines the image magnification is changed by an amount corresponding to the difference. For yellow, the group 1 detected by the sensor 3 and the group 2 detected by the sensor 2 are used.

FIG. 12 shows an image misalignment correction flow according to the present embodiment. In the image misregistration correction flow according to this embodiment, the other operations are the same except that the number of groups is different from that of the second embodiment. In step S31, the printer control unit 26 supplies each correction data to each unit of the image formation control unit 100 in the same manner as in step S11 described above, and then in step S32, the printer control unit 26 sends the correction data to the image formation control unit 100 and the light beam scanning device 15. When instructed, a group 1 image misregistration correction pattern shown in FIG. 11 is formed on the transfer belt 6. In step S <b> 33, the sensor 1 to sensor 3 detects the image misalignment correction pattern of group 1 on the transfer belt 6. The output of each sensor is given to the printer control unit 26. In step S34, the printer control unit 26 calculates the misregistration of other colors with respect to the reference color (Bk in this embodiment). Similarly, in step S35, the printer control unit 26 forms an image misregistration correction pattern of group 2 on the transfer belt 6 by the image formation control unit 100 and the light beam scanning device 15, and in step S36, the sensor 1 to the sensor 3 detects the image misregistration correction pattern of the group 2 and calculates the misregistration in step S37. Subsequent operations (steps S38 to S40 ) are the same as the operations of the first embodiment (steps S5 to S7 in FIG. 8).

  As described above, according to the image forming apparatus and the image forming method of the present embodiment, the correction accuracy is improved by detecting the image misregistration correction patterns divided into a plurality of groups with different sensors. In addition to correcting the position of main scanning and sub-scanning, it is possible to improve the correction accuracy of magnification error in the main scanning direction.

  The fourth embodiment of the present invention will be described below. In this embodiment, the configurations of the image forming apparatus, the light beam scanning apparatus, and the image forming control unit are the same as those in the first embodiment.

  FIG. 13 shows an image misregistration correction pattern formed on the transfer belt 6. In this embodiment, as shown in FIG. 13, an image misalignment correction pattern is formed on the transfer belt 6 between sheets (between pages) during continuous printing, and image misalignment correction is performed while performing an image forming operation. . The detection of the amount of misalignment and the method of misalignment correction performed using this pattern are the same as those described in the first embodiment. In FIG. 13, a group 1 pattern is formed on the transfer belt 6 ahead of the recording paper 5A in the moving direction, and a group 2 pattern is formed between the recording paper 5A and the recording paper 5B.

  In group 1, a horizontal line pattern Bk1 and a horizontal line pattern C1 are formed for the sensor 1. A horizontal line pattern Bk2 and a horizontal line pattern M1 are formed for the sensor 2. For the sensor 3, a horizontal line pattern Bk3 and a horizontal line pattern Y1 are formed.

In group 2, a horizontal line pattern Bk4 and a horizontal line pattern C2 are formed for the sensor 1. A horizontal line pattern Bk5 and a horizontal line pattern M2 are formed for the sensor 2. Then, the horizontal line pattern Bk6 and the horizontal line pattern Y2 are formed for the sensor 3.

  FIG. 14 shows an image misalignment correction flow according to the present embodiment. First, in step S41, the printer control unit 26 supplies each correction data to each unit of the image formation control unit 100 in the same manner as in step S1, and then in step S42, the image formation control unit 100 and the light beam scanning device. 15 is started, and an image forming operation for forming an image on recording paper is started. After the end of the image forming operation, in step S43, the printer control unit 26 instructs the image forming control unit 100 and the light beam scanning device 15 to place the image on the recording paper outside the image area, as shown in FIG. The image misregistration correction pattern shown is formed on the transfer belt 6. In step S <b> 44, the sensor 1 to sensor 3 detects a group 1 image misregistration correction pattern on the transfer belt 6. The output of each sensor is given to the printer control unit 26. In step S45, the printer control unit 26 calculates an image shift of another color with respect to the reference color (Bk in this embodiment). Next, in step S46, the printer control unit 26 determines whether or not to perform image misregistration correction for each color. If the shift amount of each color is ½ or more of the correction resolution, it is determined that the image shift correction is performed.

  If it is determined in step S46 that image shift correction is to be performed, the printer control unit 26 calculates a correction amount in the next step S47, and stores this value in the correction data storage unit 27 in step S48. The correction amount in this step is a correction amount related to the XFGATE signal that determines the image position in the sub-scanning direction.

  When the printer control unit 26 stores the correction data in the correction data storage unit 27 in step S48 or determines that no correction is performed in step S46 (step S46 / NO), the next page is displayed in step S49. Determine if there is. If the printer control unit 26 determines that there is a next page (step S49 / YES), it returns to step S41. Thereafter, the processes of steps S42 to S49 are repeated. If it is determined in step S49 that there is no next page (step S49 / NO), the process ends.

  In this embodiment, the case where correction in the sub-scanning direction is performed has been described, but correction in the main scanning direction is also possible by forming diagonal lines. Further, although the correction data is reflected in the image of the next page, there are cases where it is not in time depending on the inter-page distance (time). In this case, the reflection of the correction data is delayed.

  As described above, according to the image forming apparatus and the image forming method of the present embodiment, an image misalignment correction pattern is formed on the transfer belt 6 between sheets (between pages) during continuous printing, thereby forming an image. When performing image misregistration correction while performing the operation, each sensor detects only the reference color and another one-color pattern. For this reason, the continuous printing speed can be prevented from being reduced, and correction control can be simplified.

  The fifth embodiment of the present invention will be described below. In this embodiment, the configurations of the image forming apparatus, the light beam scanning apparatus, and the image forming control unit are the same as those in the first embodiment.

  FIG. 15 shows an image misregistration correction pattern formed on the transfer belt 6. In FIG. 15, a group 1 pattern is formed on the transfer belt 6 in the moving direction of the recording paper 5A in the same manner as the image misalignment correction pattern according to the fourth embodiment shown in FIG. A group 2 pattern is formed between the recording paper 5A and the recording paper 5B. However, the image misregistration correction pattern according to the present embodiment is different from the fourth embodiment in that the pattern positions of the respective colors are changed between the group 1 and the group 2 and detected by different sensors.

  In group 1, a horizontal line pattern Bk1 and a horizontal line pattern C1 are formed for the sensor 1. A horizontal line pattern Bk2 and a horizontal line pattern M1 are formed for the sensor 2. For the sensor 3, a horizontal line pattern Bk3 and a horizontal line pattern Y1 are formed.

  In group 2, a horizontal line pattern Bk4 and a horizontal line pattern M2 are formed for the sensor 1. A horizontal line pattern Bk5 and a horizontal line pattern Y2 are formed for the sensor 2. Then, a horizontal line pattern Bk6 and a horizontal line pattern C2 are formed for the sensor 3.

  In group 1, a sensor 1 detects an image shift of a cyan image with respect to Bk as a reference color. An image shift of the magenta image is detected by the sensor 2. Then, the sensor 3 detects an image shift of the yellow image. In group 2, the sensor 1 detects an image shift of the magenta image. An image shift of the yellow image is detected by the sensor 2. The image shift of the cyan image is detected by the sensor 3.

FIG. 16 shows an image misalignment correction flow according to the present embodiment. The image misalignment correction flow according to this embodiment is different from the fourth embodiment in that correction data is calculated from pattern detection results in two groups, group 1 and group 2. That is, in step S51, the printer control unit 26 provides each correction data to each unit of the image formation control unit 100 in the same manner as in step S1, and then in step S52, the image formation control unit 100 and the light beam scanning device. 15 is started, and an image forming operation for forming an image on recording paper is started. After the end of the image forming operation, in step S53, the printer control unit 26 instructs the image forming control unit 100 and the light beam scanning device 15 to place the image on the recording paper outside the image area, as shown in FIG. A group 1 image misregistration correction pattern is formed on the transfer belt 6. In step S <b> 54, the sensor 1 to sensor 3 detects a group 1 image misregistration correction pattern on the transfer belt 6. The output of each sensor is given to the printer control unit 26. In step S55, the printer control unit 26 calculates an image shift of another color with respect to the reference color (Bk in this embodiment). Next, in step S56, the printer control unit 26 determines whether there is a next page. If the printer control unit 26 determines that there is a next page (step S56 / YES), the image forming operation is performed in step S57 for the next page in the same manner as in step S52. In step S58 , the image formation control unit. 100 and the light beam scanning device 15 form the group 2 misregistration correction pattern 2 shown in FIG. In step S59, when the sensor 1 to the sensor 3 detect the misregistration correction pattern 2 of the group 2, the printer control unit 26 detects image misregistration of other colors with respect to the reference color (Bk in this embodiment). Is calculated. Next, in step S61, the printer control unit 26 determines whether or not to perform misregistration correction for each color. Subsequent operations (steps S62 to S64) are the same as those in the fourth embodiment (steps S47 to S49 in FIG. 14). In the present embodiment, the correction data is calculated using an average value as in the second embodiment.

  As described above, according to the image forming apparatus and the image forming method of the present embodiment, an image misalignment correction pattern is formed on the transfer belt 6 between sheets (between pages) during continuous printing, thereby forming an image. When the image position deviation correction is performed while performing the operation, each sensor detects an image deviation with respect to a reference color of a different color for each group. For this reason, the correction accuracy can be improved.

  The sixth embodiment of the present invention will be described below. In this embodiment, the configurations of the image forming apparatus, the light beam scanning apparatus, and the image forming control unit are the same as those in the first embodiment.

  FIG. 17 shows an image misregistration correction pattern formed on the transfer belt 6. In FIG. 15, a group 1 pattern is formed on the transfer belt 6 in the moving direction of the recording paper 5A in the same manner as the image misregistration correction pattern according to the fifth embodiment shown in FIG. A group 2 pattern is formed between the recording paper 5A and the recording paper 5B. However, in the image misregistration correction pattern according to the present embodiment, an oblique line pattern is added to group 1 and group 2 so that the writing start position in the main scanning direction can be corrected and the magnification in the main scanning direction can be corrected. This is different from the fifth embodiment.

  In group 1, a horizontal line pattern Bk1, a horizontal line pattern C1, then a diagonal line pattern Bk4, and finally a diagonal line pattern C2 are formed for the sensor 1. For the sensor 2, a horizontal line pattern Bk2, a horizontal line pattern M1, a diagonal line pattern Bk5, and finally a diagonal line pattern M2 are formed. For the sensor 3, the horizontal line pattern Bk3, the horizontal line pattern Y1, the diagonal line pattern Bk6, and finally the diagonal line pattern Y2 are formed.

  In the group 2, the horizontal line pattern Bk7, the horizontal line pattern M3, the diagonal line pattern Bk10, and finally the diagonal line pattern M4 are formed for the sensor 1. For the sensor 2, a horizontal line pattern Bk8, a horizontal line pattern Y3, an oblique line pattern Bk11, and finally an oblique line pattern Y4 are formed. For the sensor 3, a horizontal line pattern Bk9, a horizontal line pattern C3, an oblique line pattern Bk12, and finally an oblique line pattern C4 are formed.

  In group 1, a sensor 1 detects an image shift of a cyan image with respect to Bk as a reference color. An image shift of the magenta image is detected by the sensor 2. Then, the sensor 3 detects an image shift of the yellow image. In group 2, the sensor 1 detects an image shift of the magenta image. An image shift of the yellow image is detected by the sensor 2. The image shift of the cyan image is detected by the sensor 3.

  An image misregistration correction method using such an image misregistration correction pattern is substantially the same as in the third embodiment, and the image misalignment correction flow according to the present embodiment is the same as in the fifth embodiment. Since it is substantially the same as an example, the description is abbreviate | omitted.

  As described above, according to the image forming apparatus and the image forming method of the present embodiment, an image misalignment correction pattern is formed on the transfer belt 6 between sheets (between pages) during continuous printing, thereby forming an image. When performing image misregistration correction while performing an operation, correction of image misregistration is performed using a diagonal line pattern to improve correction accuracy, and not only main scanning and sub-scanning position correction, but also magnification in the main scanning direction. The error can be corrected.

  As mentioned above, although each Example of this invention was described, it is not limited to description of each said Example, A various deformation | transformation is possible in the range which does not deviate from the summary.

  The present invention can be applied to an apparatus for forming a color image, such as a color copying machine, a color printer, a color FAX, and a color printing machine.

1 is a perspective view showing a main configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of a control unit of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a block diagram illustrating a configuration of a VCO clock generation unit of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a block diagram illustrating a configuration of a writing start position control unit of the image forming apparatus according to the first exemplary embodiment of the present invention. 3 is a timing chart illustrating an output signal of a writing start position control unit of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a block diagram illustrating a configuration of a previous stage of a control unit of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a diagram illustrating an image misregistration correction pattern of the image forming apparatus according to the first exemplary embodiment of the present invention. 3 is a flowchart illustrating an operation of correcting an image misalignment of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 10 is a diagram illustrating an image misalignment correction pattern of the image forming apparatus according to the second exemplary embodiment of the present invention. 6 is a flowchart illustrating an operation of correcting an image misalignment of the image forming apparatus according to the second exemplary embodiment of the present invention. It is a figure which shows the image misalignment correction pattern of the image forming apparatus of 3rd Example of this invention. 10 is a flowchart illustrating an operation of correcting an image misregistration of an image forming apparatus according to a third exemplary embodiment of the present invention. It is a figure which shows the image misalignment correction pattern of the image forming apparatus of 4th Example of this invention. 10 is a flowchart illustrating an operation of correcting an image misalignment of an image forming apparatus according to a fourth exemplary embodiment of the present invention. It is a figure which shows the image misalignment correction pattern of the image forming apparatus of 5th Example of this invention. 10 is a flowchart illustrating an operation of correcting an image misalignment of an image forming apparatus according to a fifth exemplary embodiment of the present invention. It is a figure which shows the image misalignment correction pattern of the image forming apparatus of the 6th Example of this invention. 6 is a timing chart for explaining the operation of the writing start position control unit 20 in the sub-scanning direction according to the first embodiment of the present invention.

Explanation of symbols

1, 2, 3 Sensor 4 Conveying motor 5 Recording paper 6 Transfer belt 7 Charger 8 Transfer device 9 Developing unit 10 Photoreceptor 11 LD unit 12 BTL
13 fθ lens 14 polygon mirror 15 light beam scanning device 16 synchronization sensor 17 lens 18 mirror 19 polygon motor control unit 20 writing start position control unit 21 LD control unit 22 sync detection lighting control unit 23 phase synchronization clock generation unit 24 VCO clock Generation unit 25 Reference clock generation unit 26 Printer control unit 27 Correction data storage unit 28 Pixel clock generation unit 29 Phase comparator 30 LPF
31 VCO
32 1 / N frequency divider 33 main scanning line synchronization signal generating unit 34 sub scanning gate signal generating unit 35 main scanning gate signal generating unit 36 sub scanning counter 37 comparator 38 gate signal generating unit 39 main scanning counter 40 comparator 41 gate signal generation Part 100 Image formation control part 101 Image formation part

Claims (8)

An image forming apparatus having a plurality of image forming units for forming a single color image for each color, and superimposing single color images formed by the plurality of image forming units to form a multicolor image,
When image formation is continuously performed on two or more recording media, a forming unit that forms a predetermined image positional deviation correction pattern for each color between the recording media;
A plurality of images arranged in the main scanning direction for detecting an image position deviation correction pattern of a reference color and an image position deviation correction pattern of a predetermined color for the image position deviation correction pattern formed by the forming unit . Detecting means of
Correction means for correcting an image position shift between two of the predetermined one color with respect to the reference color based on a detection result detected by the detection means;
I have a,
The image misregistration correction pattern detected by each of the plurality of detecting means is a group including a plurality of image misregistration correction patterns, and the predetermined one color is different from each other in the main scanning direction. The predetermined color detected by each of the detection means is different if the groups are included in each group and the groups are different.
An image forming apparatus. A latent image is formed by irradiating image light corresponding to image data on a rotating or moving image carrier, the latent image is visualized by a developing means, and the visualized image is rotated or rotated. A monochrome image on the recording medium is transferred onto a recording medium conveyed by a moving transfer means, or transferred onto the recording medium after being transferred to the transfer means and then transferred onto the recording medium. An image forming apparatus for forming a multicolor image on the recording medium by superimposing single color images formed by the image forming unit on the recording medium. ,
In a case where image formation is continuously performed on two or more recording media, a forming unit that forms a predetermined image displacement correction pattern for each color between the images transferred to the transfer unit on the transfer unit;
A plurality of images arranged in the main scanning direction for detecting an image position deviation correction pattern of a reference color and an image position deviation correction pattern of a predetermined color for the image position deviation correction pattern formed by the forming unit . Detecting means of
And correcting means based on a result of detection, that to correct the image position shift between two colors of the predetermined one color relative to the reference color by the detection unit,
I have a,
The image misregistration correction pattern detected by each of the plurality of detecting means is a group including a plurality of image misregistration correction patterns, and the predetermined one color is different from each other in the main scanning direction. The predetermined color detected by each of the detection means is different if the groups are included in each group and the groups are different.
An image forming apparatus. Further comprising variable means for varying the formation position of the image displacement correction pattern;
The detection means detects the image misregistration correction pattern for each color,
Said correcting means, on the basis of the detection result detected by the detecting means, the image forming apparatus according to claim 1 or 2, characterized in that to correct the image position shift between the two colors. The image forming apparatus according to claim 3 , wherein the variable unit varies the formation position of the image misregistration correction pattern every time the detecting unit detects an image misregistration between the two colors. A method for forming a multicolor image by forming a plurality of single color images for each color and superimposing the formed single color images respectively,
In the case where image formation is continuously performed on two or more recording media, a forming step of forming a predetermined image misregistration correction pattern for each color between the recording media;
For the image misregistration correction pattern formed in the forming step, a plurality of detections in which a reference color image misregistration correction pattern and a predetermined one color image misregistration correction pattern are arranged in the main scanning direction A detecting step for detecting by means ;
A correction step of correcting an image position shift between two of the predetermined one color with respect to the reference color based on a detection result of the detection step;
The stomach line,
The image misregistration correction pattern detected by each of the plurality of detecting means is a group including a plurality of image misregistration correction patterns, and the predetermined one color is different from each other in the main scanning direction. The predetermined color detected by each of the detection means is different if the groups are included in each group and the groups are different.
An image forming method. A latent image is formed by irradiating image light corresponding to image data on a rotating or moving image carrier, the latent image is visualized by a developing means, and the visualized image is rotated or rotated. A monochrome image on the recording medium is transferred onto a recording medium conveyed by a moving transfer means, or transferred onto the recording medium after being transferred to the transfer means and then transferred onto the recording medium. A plurality of images for each color, and superimposing the formed single color images on the recording medium to form a multicolor image on the recording medium,
In the case where image formation is continuously performed on two or more recording media, a forming step of forming a predetermined image misalignment correction pattern for each color between the images transferred to the transfer unit on the transfer unit;
For the image misregistration correction pattern formed in the forming step, a plurality of detections in which a reference color image misregistration correction pattern and a predetermined one color image misregistration correction pattern are arranged in the main scanning direction A detecting step for detecting by means ;
Based on the detection result of the detecting step, a correction step that to correct the image position shift between two colors of the predetermined one color relative to the reference color,
The stomach line,
The image misregistration correction pattern detected by each of the plurality of detecting means is a group including a plurality of image misregistration correction patterns, and the predetermined one color is different from each other in the main scanning direction. The predetermined color detected by each of the detection means is different if the groups are included in each group and the groups are different.
An image forming method. And further comprising a variable step of varying the formation position of the image displacement correction pattern.
The detection step detects the image misregistration correction pattern for each color,
The image forming method according to claim 5 , wherein the correcting step corrects an image position shift between the two colors based on a detection result of the detecting step. 8. The image forming method according to claim 7 , wherein in the variable step, the image position shift correction pattern forming position is changed each time the image position shift between the two colors is detected in the detection step.

Images