JP2007279238A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always output image data temporarily stored in a storage in a latest corrected state after displacement of registration is taken into account and corrected. <P>SOLUTION: An actual main scanning line and an amount of displacement of an ideal main scanning line in a sub-scanning direction are stored in color shift amount storage sections 303C to 303K as information indicating the inclination and curve of the main scanning line. A controller 302 performs a printing process after correcting image data so as to offset the amount of displacement of the main scanning line stored in the color shift amount storage sections. The controller 302 includes determining sections and re-correcting sections. Each of the color shift correction amount calculating sections 307C to 307K calculates an amount of correction of color shift based on information about the amount of displacement of the main scanning line stored in the color shift amount storage section. The amount of correction of a color shift in the sub-scanning direction corresponding to coordinate information in the main scanning direction specified by each of color shift amount correcting sections 308C to 308K is calculated for each dot, and the result of the calculation is output to the corresponding color shift amount correcting section. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method, and more specifically, a so-called tandem including a plurality of color developing devices and a transfer member that sequentially transfers a plurality of color images formed by the developing devices. The present invention relates to a color image forming apparatus and a color image forming method.

  In recent years, in order to increase the image forming speed in an electrophotographic color image forming apparatus, the same number of developing devices and photosensitive drums as the number of color materials are provided, and images of different colors are sequentially placed on an image conveying belt or a recording medium. The number of tandem color image forming apparatuses that transfer images is increasing. In this tandem color image forming apparatus, it is already known that there are a plurality of factors that cause registration deviation, and various countermeasures have been proposed for each factor.

  One of the factors that cause registration deviation is non-uniformity and attachment position deviation of the lens of the deflection scanning apparatus, and deviation of the assembly position of the deflection scanning apparatus to the color image forming apparatus main body. In that case, the scan line is inclined or bent, and the degree of the change varies for each color, resulting in registration shift.

  As a method for coping with this registration deviation, for example, there are coping methods disclosed in Patent Documents 1, 2, and 3. In Patent Document 1, in the assembling process of the deflection scanning device, the amount of bending of the scanning line is measured using an optical sensor, and the bending of the scanning line is adjusted by mechanically rotating the lens. A method of fixing is disclosed.

  In Patent Document 2, in the step of assembling the deflection scanning device into the color image forming apparatus main body, the inclination of the scanning line is measured using an optical sensor, and the deflection scanning device is mechanically tilted to tilt the scanning line. A method of assembling to a color image forming apparatus main body after adjusting is disclosed.

  Patent Document 3 discloses a method of measuring the inclination of a scanning line and the amount of bending using an optical sensor, correcting bitmap image data so as to cancel them, and forming the corrected image. Yes. This method is described in Patent Documents 1 and 2 described above in that a mechanical adjustment member and an adjustment process at the time of assembly are not required because the registration deviation is electrically corrected by processing image data. It is possible to deal with registration deviation at a lower cost than existing methods. This electrical registration error correction is divided into correction for each pixel and correction for less than one pixel. In the correction in units of one pixel, the pixels are offset in the sub-scanning direction in units of one pixel in accordance with the correction amount of inclination and curvature. For correction of less than one pixel, the gradation value of the bitmap image data is adjusted by the pixels before and after the sub-scanning direction. By performing the correction of less than one pixel, it is possible to eliminate an unnatural step at the offset boundary caused by the correction in units of one pixel and smooth the image.

JP 2002-116394 A JP 2003-241131 A JP 2004-170755 A

  However, a device having a large-capacity storage device such as an HDD may be configured to temporarily store image data subjected to electrical registration deviation correction in the large-capacity storage device. In this case, when the correction means (correction value) changes with time, if the image data corrected by the previous correction means is stored in the large-capacity storage device, the subsequent print request In contrast, print output by the wrong correction means is performed. In addition, there is a problem that variation occurs in the print quality of the output image.

  In addition, with the reduction in cost and size of the scanner unit, it is necessary for the controller to correct the magnification and registration of each color of the engine. The present invention is a system configuration having a so-called BOX function that stores image data subjected to correction processing in a BOX (storage device). This is because, when the correction method (correction value) is changed and the image data already corrected by the previous correction method is stored in the BOX, an image with an incorrect correction is printed in response to a subsequent print request. Resulting in. As a result, there is a problem that the image quality varies.

  In the above-described patent document 3, after print image generation (including halftone processing) is performed, color misregistration correction processing is performed immediately before PWM processing in the output unit to the printer engine. The correction processing is performed only at the time of output to the. On the other hand, the image forming apparatus of the present invention realizes re-correction according to environmental changes for image data stored in a state where correction processing is performed in a system having a BOX function.

  An object of the present invention is to temporarily store the corrected image in a mass storage device in an image formation in which electrical registration error correction needs to be performed before printing in consideration of the occurrence of registration error. The image data is always output in the latest correct correction state.

  The present invention has been made to achieve such an object. The invention according to claim 1 is an image forming apparatus that forms an image based on at least print data supplied from a data processing apparatus. Image development means for interpreting print data supplied from a data processing apparatus and developing the image data into bitmap image data, and color misregistration or distortion of an image generated in image formation with respect to the image data developed by the image development means The correction means for correcting the correction data using correction data, the correction data storage means for storing the correction data used in the correction means, the image data developed by the image development means or the image data corrected by the correction means Image data storage means for storing in a storage device in a predetermined format, and the image stored by the image data storage means Correction data management means for storing and managing in the storage device in association with the correction data used when the data is corrected by the correction means, and necessity of changing the correction data used in the correction means The correction data updating means for updating the contents of the correction data stored in the correction data storage means, and the image data stored in the storage device by the image data storage means When there is a print instruction from the user, it is determined whether the correction data managed in association with the image data by the correction data management unit has the same content as the correction data updated by the correction data update unit And determining whether the image data is different from the latest correction data. And having a re-correction means for re-corrected according to the correction data updated by the correction data and the correction data updating means are managed with.

  According to a second aspect of the present invention, there is provided an image forming apparatus that forms an image based on at least print data supplied from a data processing apparatus, interprets the print data supplied from the data processing apparatus, and generates a bitmap image. Image developing means for developing data, correction means for correcting color misalignment or distortion of an image generated in image formation with correction data for the image data developed by the image developing means, and the correction means used Correction data storage means for storing the correction data; image data storage means for storing the image data developed by the image development means or the image data corrected by the correction means in a storage device in a predetermined format; Used when the image data stored by the image data storage means is corrected by the correction means Stored in the storage device in association with the correction data, and stored in the correction data storage means when the correction data used in the correction means needs to be changed. Correction data updating means for updating the contents of the correction data, and the latest correction data updated by the correction data updating means, and stored in the storage device by the image data storage means at a predetermined timing. The correction data managed in association with the image data and recorrection means for correcting again according to the latest correction data.

  According to a third aspect of the present invention, there is provided an image forming apparatus that forms an image based on at least print data supplied from a data processing apparatus, and interprets the print data supplied from the data processing apparatus to generate a bitmap image. Image developing means for developing data, correction means for correcting color misalignment or distortion of an image generated in image formation with correction data for the image data developed by the image developing means, and the correction means used Correction data storage means for storing the correction data; image data storage means for storing the image data developed by the image development means or the image data corrected by the correction means in a storage device in a predetermined format; Used when the image data stored by the image data storage means is corrected by the correction means. When there is a need to change the correction data used in the correction means and stored in the storage device in association with the correction data, the correction data storage means stores the correction data. Correction data updating means for updating the content of the correction data, and the latest correction data updated by the correction data updating means, and stored in the storage device by the image data storage means at a predetermined timing. The image data stored in the storage device by the image data storage unit, the first recorrection unit correcting the image data again in accordance with the correction data managed in association with the image data and the latest correction data. When the user gives a print instruction to the image data, the correction data management means Determination means for determining whether the correction data managed in association with data is the same as the latest correction data stored in the correction data storage means; and the latest correction data by the determination means And a second re-correction unit that corrects the correction data again in accordance with the latest correction data when it is determined that they are different from each other.

  According to a fourth aspect of the present invention, in the invention according to the first, second, or third aspect, the image forming apparatus irradiates the photoconductor with a light beam modulated by each color signal. An exposure unit that forms an electrostatic latent image, a developing unit that visualizes the electrostatic latent image formed on the photosensitive member by the exposure unit, and each color image that is visualized by the developing unit An image forming apparatus that forms a plurality of image stations each having a transfer means for transferring to a transfer material and sequentially transfers the color image formed at each image station onto a transfer material conveyed by the conveyance means. The correction unit stores a color shift amount storage unit that stores a color shift amount for each image station, and a color shift correction that calculates a color shift correction amount based on the color shift amount obtained from the color shift amount storage unit. Amount calculation means and color misregistration correction amount calculation And having a color shift correcting means for correcting the color shift amount on the basis of the calculation result of means.

  According to a fifth aspect of the invention, in the invention of the fourth aspect, the color misregistration amount correcting unit corrects a color misregistration less than a pixel unit, and a coordinate conversion unit that corrects a color misregistration in pixel units. Gradation correction means.

  According to a sixth aspect of the present invention, there is provided an image forming method for forming an image based on at least print data supplied from a data processing device, and interpreting the print data supplied from the data processing device to generate a bitmap image. An image development step for developing data, a correction step for correcting color misalignment or distortion of an image generated in image formation with correction data for the image data developed by the image development step, and a correction step used A correction data storage step for storing the correction data; an image data storage step for storing the image data expanded by the image expansion step or the image data corrected by the correction step in a storage device in a predetermined format; The image data stored by the image data storage step is A correction data management step that is stored and managed in the storage device in association with the correction data that was used when the correction was performed in the correction step, and the correction data that is used in the correction step needs to be changed. A correction data update step for updating the content of the correction data stored in the correction data storage step, and a print instruction from the user for the image data stored in the storage device by the image data storage step A determination step for determining whether the correction data managed in association with the image data in the correction data management step has the same content as the correction data updated in the correction data update step; It is determined by the determination step that the correction data is different from the updated correction data. Case, and having a re-correction step of re-corrected according to the correction data the update and the correction data is managed in association with the image data.

  According to a seventh aspect of the invention, in the sixth aspect of the invention, the latest correction is performed by the correction data updating step instead of the determination step and the recorrection step after the correction data updating step. As the data is updated, the correction data managed in association with the image data stored in the storage device by the image data storage step at a predetermined timing and the latest correction It has a re-correction step which corrects again according to data.

  According to an eighth aspect of the present invention, in the sixth aspect of the present invention, the latest correction data is updated by the correction data update step after the correction data update step. A first recorrection in which the image data stored in the storage device at the timing of the image data is corrected again according to the correction data managed in association with the image data and the latest correction data. It has a step.

  The present invention relates to image data temporarily stored in a mass storage device in a corrected state in image formation in which it is necessary to perform electrical registration deviation correction before printing in consideration of occurrence of registration deviation. Is always output in the latest correct correction state.

  When the correction value is changed, all images in the BOX corrected with the previous correction value are corrected again with the changed correction value. When the correction value is changed, a subsequent print request is issued. If there is, it is corrected again based on the comparison between the previous correction value and the latest correction value, and is output. When printing the image data stored in the BOX, it is always determined whether the image data has been corrected with the latest correction value. If the image data is not in the latest correction state, it is corrected again and output. As a result, when printing image data stored in the BOX function, it is possible to print with an image that has been correctly corrected in accordance with the state of the latest engine.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view for explaining an embodiment of a color image forming apparatus according to the present invention, and corresponds to, for example, a four-drum type color laser beam printer. In this color image forming apparatus, a transfer material cassette 53 is mounted at the lower right side of the main body apparatus. The transfer material set in the transfer material cassette 53 is taken out one by one by the paper feed roller 54 and fed to the image forming unit by the pair of transport rollers 55a and 55b.

  In the image forming unit, the transfer conveyance belt 10 that conveys the transfer material is stretched flat in the transfer material conveyance direction by a plurality of rotating rollers, and electrostatically adsorbed to the transfer conveyance belt 10 at the most upstream portion. It is configured. The photosensitive drums 14C (C; CYAN), 14M (M; MAGENTA), 14Y (Y; YELLOW), 14K (K; BLACK) as four drum-shaped image bearing members facing the belt conveying surface. ) Are linearly arranged to constitute an image forming unit.

  The developing units 52C, 52M, 52Y, and 52K constituting the image forming unit include the respective color toners, chargers, and developing units of the photosensitive drums 14C to 14K. A predetermined gap is provided between the charger and the developing unit in the housing of each of the developing units 52C to 52K described above, and the exposure unit 51C, 51M, 51Y, 51K including the laser scanner is connected to the photosensitive drum 14C via the gap. The peripheral surface of ˜14K is uniformly charged with a predetermined charge. The exposure units 51C to 51K expose the peripheral surfaces of the charged photosensitive drums 14C to 14K according to the image information to form an electrostatic latent image, and the developing unit performs the above-described blackout position of the electrostatic latent image. The toner is transferred to the portion to form (develop) a toner image. Further, transfer members 57C, 57M, 57Y, and 57K are arranged across the conveyance surface of the transfer conveyance belt 10.

  The toner images formed (developed) on the peripheral surfaces of the photosensitive drums 14C to 14K are converted into charges generated on the transfer material conveyed by the transfer electric field formed by the transfer members 57C to 57K corresponding to the toner images. It is absorbed and transferred to the transfer material surface. The transfer material onto which the toner image has been transferred is discharged out of the apparatus by a pair of discharge rollers 59a and 59b. The transfer / conveying belt 10 may be an intermediate transfer belt having a configuration in which C (CYAN), Y (YELLOW), M (MAGENTA), and K (BLACK) toners are once transferred and then secondarily transferred to a transfer material. Absent.

  FIG. 2 is an image diagram for explaining a shift of a main scanning line scanned on a photosensitive drum as an image carrier. Reference numeral 201 denotes an image of an ideal main scanning line, and scanning is performed perpendicular to the rotation direction of the photosensitive drum 14. Reference numeral 202 denotes an image of an actual main scanning line in which a rightward tilt or curvature is generated due to a positional accuracy or diameter shift of the photosensitive drum 14 and a positional accuracy shift of the optical system in the exposure unit 51 of each color. Show. When such an inclination or curvature of the main scanning line exists in any color image station, color misregistration occurs when a plurality of color toner images are collectively transferred to the transfer medium.

  In the present embodiment, in the main scanning direction (X direction), an ideal main scanning line at a plurality of points (point B, point C, point D) with the point A serving as the scanning start position of the print area as a reference point. The amount of deviation between 201 and the actual main scanning line 202 in the sub-scanning direction is measured. Then, each point where the amount of deviation is measured is divided into a plurality of regions (region Pa-Pb is region 1, region Pb-Pc is region 2, and region Pc-Pd is region 3). The slope of the main scanning line in each region is approximated by straight lines (Lab, Lbc, Lcd) connecting the points. Accordingly, when the difference in the amount of deviation between points (m1 for area 1, m2-m1 for area 2, m3-m2 for area 3) is a positive value, the main scanning line of the corresponding area has an upward slope. It is shown that. Moreover, when it is a negative value, it has having the downward slope.

  FIG. 3 is a block diagram for explaining the operation of the color misregistration correction process for correcting the color misregistration caused by the inclination or curvature of the scanning line performed in the present embodiment. The printer engine 301 actually performs a printing process based on the image bitmap information generated by the controller 302. The color misregistration amount storage units 303C, 303M, 303Y, and 303K store the main scan line misregistration amount for each region described above for each color.

  In this embodiment, the information indicating the inclination or curvature of the main scanning line 201 is the amount of deviation of the actual main scanning line 202 measured at a plurality of points and the ideal main scanning line in the sub-scanning direction described in FIG. As color misregistration amount storage units 303C to 303K. FIG. 4 is a table showing an example of information stored in the color misregistration amount storage units 303C to 303K. In this embodiment, the color misregistration amount storage unit stores the deviation amount between the ideal main scan line and the actual main scan line. However, the actual main scan line has an inclination and curvature characteristic. The information is not limited to this as long as it is identifiable information.

  Further, the information stored in the color misregistration amount storage units 303C to 303K may be configured to measure the misregistration amount in the manufacturing process of the apparatus and store it in advance as information unique to the apparatus. Alternatively, a detection mechanism for detecting the shift amount is prepared in the apparatus itself, a predetermined pattern for measuring the shift is formed for each color image carrier, and the shift amount detected by the detection mechanism is stored. Any configuration may be used.

  Next, an operation of the controller 302 performing the printing process by correcting the image data so as to cancel out the main scanning line shift amounts stored in the color shift amount storage units 303C to 303K will be described. The image generation unit 304 generates raster image data that can be printed from print data received from a computer device (not shown), and outputs the raster image data for each dot as RGB data. The color conversion unit 305 converts RGB data into CMYK space data that can be processed by the engine 301 and stores the data in a bitmap memory 306 described later for each color.

  The bitmap memory 306 temporarily stores raster image data to be printed, and is a page memory that stores image data for one page or a band memory that stores data for a plurality of lines. The halftone processing units 309C, 309M, 309Y, and 309K reduce the number of bits of pixel data to be input using a predetermined halftone screen pattern, and perform gradation in halftone screen area units from gradation representation in pixel units. To convert it into an expression. Then, it is stored for each color in a bitmap memory 306 to be described later. The color misregistration correction amount calculation units 307C to 307K calculate the color misregistration correction amount based on the information on the main scanning line misregistration amount accumulated in the color misregistration amount storage units 303C to 303K. Then, for each dot, the color misregistration correction amount in the sub-scanning direction corresponding to the coordinate information in the main scanning direction specified from the color misregistration amount correcting units 308C to 308K described later is calculated. Further, the color misregistration amount correction units 308C to 308K are output.

When the coordinate data in the main scanning direction is x (dots) and the color misregistration correction amount in the sub-scanning direction is Δy (dots), the calculation formula of each area based on FIG. 2 is shown below (print density is 600 dpi). ).
Region 1: Δy1 = x * (m1 / L1)
Region 2: Δy2 = m1 * 23.622 + (x−L1 * 23.622) * ((m2−m1) / (L2−L1))
Region 3: Δy3 = m2 * 23.622 + (x−L2 * 23.622) * ((m3−m2) / (L3−L2))
L1, L2, and L3 are distances (unit: mm) in the main scanning direction from the printing start position to the left ends of the areas 1, 2, and 3. m 1, m 2, and m 3 are deviation amounts of the ideal main scanning line 201 and the actual main scanning line 202 at the left ends of the regions 1, 2, and 3.

  The color misregistration amount correction units 308C to 308K each adjust the toner image based on the color misregistration correction amount calculated for each dot by the color misregistration correction amount calculation unit in order to correct the color misregistration due to the inclination and distortion of the main scanning line. Prevents color misregistration (registration misalignment) when the image is transferred to a transfer medium. That is, adjustment of the output timing of bitmap data stored in the bitmap memory 306 and adjustment of the exposure amount for each pixel in the exposure units 310C, 310M, 310Y, and 310K are performed. Then, color misregistration (registration misalignment) when the toner images of the respective colors on the photosensitive drums 311C, 311M, 311Y, and 311K are transferred to a transfer medium can be prevented.

  As described above, the image forming apparatus of the present invention interprets print data supplied from the data processing apparatus 101 (FIG. 7 described later) in the controller 302 and develops it into bitmap image data. 306 is provided. Further, correction units 303, 307, and 308 are provided for correcting image color misalignment or distortion caused in image formation with the correction data for the image data developed by the image development units 304, 305, and 306. Further, a correction data storage unit 705 (FIG. 8 to be described later) that stores correction data used in the correction units 303, 307, and 308 is provided. An image data storage unit 711 (see FIG. 8 to be described later) stores the image data developed by the image development units 304, 305, and 306 or the image data corrected by the correction units 303, 307, and 308 in a predetermined format in a storage device. ).

  Furthermore, the controller 302 includes a correction data management unit, a correction data update unit, a determination unit, and a re-correction unit, and correction data is updated and determined by a CPU (not shown) in the controller 302. The re-correction is performed by the color misregistration correction unit. These functions are described in FIG. 10, FIG. 12, and FIG. The correction data management unit stores and manages the image data stored in the image data storage unit in the storage device (bitmap memory 306) in association with the correction data used when the correction is performed by the correction unit. . The correction data updating unit updates the content of the correction data stored in the correction data storage unit when the correction data used in the correction unit needs to be changed.

  A case will be described in which the determination unit receives a print instruction from the user for the image data stored in the storage device by the image data storage unit. In this case, it is determined whether or not the correction data managed in association with the image data by the correction data management unit has the same content as the latest correction data stored in the correction data storage unit. Further, the re-correction unit corrects again according to the correction data managed in association with the image data and the latest correction data when the determination unit determines that the difference is different from the latest correction data.

  Further, the re-correction unit corrects again as the latest correction data is updated by the correction data update unit. That is, the image data stored in the storage device by the image data storage unit at a predetermined timing is corrected again according to the correction data managed in association with the image data and the latest correction data.

  The re-correction unit includes a first re-correction unit. The first re-correction unit corrects again as the latest correction data is updated by the correction data update unit. That is, the image data stored in the storage device by the image data storage unit at a predetermined timing is corrected again according to the correction data managed in association with the image data and the latest correction data.

  The re-correction unit includes a second re-correction unit. The second re-correction unit corrects again according to the correction data managed in association with the image data and the latest correction data when the determination unit determines that the difference is different from the latest correction data.

  Further, the correction unit includes color misregistration amount storage units 303C to 303K that store the color misregistration amount for each image station. In addition, color misregistration correction amount calculation units 307C to 307K that calculate color misregistration correction amounts based on the color misregistration amounts obtained from the color misregistration amount storage units 303C to 303K are provided. In addition, color misregistration amount correction units 308C to 308K that correct the color misregistration amount based on the calculation results of the color misregistration correction amount calculation units 307C to 307K are provided.

  Furthermore, the color misregistration amount correction units 308C to 308K include coordinate conversion units 600C to 600K that correct color misregistration in units of pixels and gradation correction units 604C to 604K that correct color misregistration in units of pixels. Further, the coordinate conversion units 600C to 600K include first DMACs 602C to 602K and second DMACs 603C to 603K.

  5A to 5C are image diagrams for explaining an operation in which the coordinate conversion unit corrects the shift amount of the integer part of the color shift correction amount Δy and the color shift in line units. As shown in FIG. 5A, the coordinate conversion units 600C to 600K perform bitmap memory according to the value of the integer part of the color misregistration correction amount Δy obtained from the color misregistration information of the main scanning line approximated by a straight line. The coordinates in the sub-scanning direction (Y direction) of the image data stored in 306 are offset.

  For example, as shown in FIG. 5B, when the coordinate position in the sub-scanning direction from the coordinate counter is n, if the coordinate position in the main scanning direction is X, the I region in the X coordinate in the main scanning direction Then, the color misregistration correction amount Δy is 0 or more and less than 1. When reconstructing the nth line data, the nth line data is read from the bitmap memory. In the region II, the color misregistration correction amount Δy is 1 or more and less than 2. When the n-th line data is reconfigured, a coordinate conversion process is performed to read the image bit map at the position offset from the number of one sub-scan line, that is, the n + 1-th line data from the bitmap memory. Similarly, coordinate conversion processing is performed in order to read data in the n + 2 line in the region III, the n + 3 line in the IV region, and the n + 4 line in the V region. With the above method, reconstruction processing in the sub-scanning direction is performed in units of pixels.

  FIG. 5C is a diagram illustrating an exposure image obtained by exposing the image carrier to image data that has been subjected to color shift correction in pixel units by the coordinate conversion unit.

  FIGS. 6A to 6F are image diagrams for explaining the color misregistration correction performed by the gradation correction unit for less than a pixel unit, that is, the operation for correcting the misregistration amount after the decimal point of the color misregistration correction amount Δy. . Correction of the shift amount after the decimal point is performed by adjusting the exposure ratio of dots before and after in the sub-scanning direction.

  FIG. 6A is an image diagram of a main scanning line having an upward slope. 6B is a bitmap image diagram of a horizontal straight line before gradation correction, and FIG. 6C is a diagram for canceling the color shift due to the inclination of the main scanning line in FIG. It is a correction image figure of (b). In order to realize the correction image of FIG. 6C, the exposure amount adjustment of dots before and after in the sub-scanning direction is performed.

FIG. 6D is a table showing the relationship between the color misregistration correction amount Δy and the correction coefficient for performing gradation correction. k is an integer part of the color misregistration correction amount Δy (the fractional part is rounded down), and represents the correction amount in the sub-scanning direction in units of pixels. β and α are correction coefficients for performing correction in the sub-scanning direction less than a pixel unit, and represent the distribution ratio of the exposure amount of dots before and after the sub-scanning direction based on information below the decimal point of the color misregistration correction amount Δy. Yes.
α = Δy−k
β = 1−α
Is calculated by α represents the distribution rate of preceding dots, and β represents the distribution rate of subsequent dots.

  FIG. 6E is a bitmap image diagram in which gradation correction is performed to adjust the exposure ratio of dots before and after the sub-scanning direction in accordance with the correction coefficient of FIG. FIG. 6F is an exposure image diagram of an image carrier of a bitmap image whose gradation has been corrected, and the inclination of the main scanning line is canceled and a horizontal straight line is formed.

  The coordinate conversion units 600 </ b> C to 600 </ b> K perform coordinate conversion on the image bitmap data reconfigured so as to correct the color shift amount in units of pixels from the bitmap memory 306. Coordinate conversion can be realized by setting the transfer address and transfer size obtained from the coordinate counter and the address generation unit to DMACs 602C to 602K and 603C to 603K and performing transfer.

  For example, in FIGS. 6A to 6F, when the amount of deviation of the inclination is indicated by a broken line in FIG. 6A, the coordinate conversion should be transferred in the order of the n line in FIG. 6B. It ’s fine. At this time, the DMACs 603C to 603K can perform gradation correction of less than a pixel unit by transferring the (n-1) th line to the gradation correction unit for gradation correction.

The gradation correction units 604C to 604K obtain the pixel position in the main scanning direction from the coordinate counter in order to generate correction data. The gradation correction units 604C to 604K obtain correction coefficients α and β from the value of the coordinate counter, generate correction data by performing the following calculation with the pixel values Pn and Pn−1 transferred from the DMAC.
P′n (x) = Pn (x) * β (x) + Pn−1 (x) * α (x)

  By the above-described calculation, an image bitmap in which the color misregistration amount less than the pixel unit in the sub-scanning direction is corrected is output.

  The image data that has been subjected to the color misregistration correction by the above processing is output to the printer engine 1 as a color signal that has undergone pulse width modulation processing in the PWMs 410C, 410M, 410Y, and 410K. Then, exposure processing for the image carrier is performed by the exposure units 310C, 310M, 310Y, and 310K.

  As described above, if the amount of correction for correcting the amount of deviation in the sub-scanning direction at each main scanning position is calculated from the image bitmap information and reconstructed as corrected image bitmap information, An image in which the color shift due to the inclination or distortion of the scanning line is corrected can be created.

  FIG. 7 is a system configuration diagram of the image forming apparatus of the present invention. The data processing apparatus 101 is a computer, for example, and functions as a supply source of image information or a printer control apparatus. In this embodiment, a laser beam printer (printer) is used as the image forming apparatus 102. Needless to say, the image forming apparatus applied in the present embodiment is not limited to a laser beam printer, but may be a printer of another printing system such as an ink jet printer.

  A printer controller (controller) 302 generates raster data for each page based on image information (for example, ESC code, page description language, etc.) supplied from the data processing apparatus 101, and sends it to the printer engine 105.

  The printer engine 301 forms a latent image on a photosensitive drum based on raster data supplied from the controller 302, and records the image by transferring and fixing the latent image on a recording medium (electrophotographic method). .

  The panel unit 104 is used as a user interface. The user can instruct a desired operation by operating the panel unit 104. The panel unit 104 displays processing contents of the printer 102 and warning contents to the user.

  FIG. 8 is a block diagram illustrating a configuration example of the controller in FIG. The panel interface unit 701 performs data communication with the panel unit 104. The CPU 709 can confirm the contents set / instructed by the user on the panel unit 104 via the panel interface unit 701.

  The host interface unit 702 is for two-way communication connection with the data processing apparatus 101 such as a host computer via a network. The intermediate data creation unit 703 performs processing for converting print data into intermediate data in a form that is easy to handle inside the printer 102.

  The ROM 704 holds processing described in the present invention and other control program codes executed by the printer 102. Reference numeral 705 denotes a RAM used in the present invention. Holds intermediate data derived from the print data received by the host interface unit 702, holds bitmap information as a result of rendering the intermediate data, and other temporary buffer areas necessary for other processing and various processing statuses Or hold.

  The engine interface unit 706 is for communication connection with the printer engine 301. The CPU 709 can recognize the state of the printer engine 301 via the engine interface unit 706.

  The DMA control unit 707 transfers the bitmap data in the RAM 705 to the engine interface unit 306 according to an instruction from the CPU 709. The rendering unit 708 creates a print image that is actually printed out according to the contents of the intermediate data stored in the RAM 705.

  The CPU 709 controls devices connected to the CPU bus 711 based on the control program code stored in the ROM 704. The nonvolatile memory 710 is, for example, for holding control information such as a density correction table.

  The HDD 711 temporarily stores print data as image data after image expansion. It is possible to implement electronic sorting by reading specified image data a plurality of times, or to implement secure printing that reads out image data stored after user authentication using a preset password, etc., and prints it out. it can.

  The CPU bus 712 includes an address, data, and a control bus. The panel interface unit 701, the host interface unit 702, the image data generation unit 703, the ROM 704, and the RAM 705 are accessible to all devices connected to the CPU bus 712, respectively. The engine interface unit 706, the DMA control unit 707, the rendering unit 708, the CPU 709, and the EEPROM 710 can also access all devices connected to the CPU bus 712, respectively.

  FIG. 9 is a diagram for explaining a data flow when a controller that configures a printer that does not require color misregistration correction performs print output. Upon receiving the PDL data 805, the controller 302 first generates image data 806 by image expansion processing 801, further performs compression 802, and stores the compressed image data 807 in the HDD or RAM 800. The compressed image data 807 is transferred to the printer engine 301 for printing 804 while being expanded into image data 808 at a predetermined timing.

  FIG. 10 is a diagram for explaining a data flow when a controller that configures a printer that needs color misregistration correction processing performs print output. 9 differs from FIG. 9 in that the uncorrected image data 907 obtained by image development 901 of the PDL data 906 is compressed 903 after the correction processing 902 based on the correction data 911 and stored as compressed and corrected image data 909 in the HDD or RAM 900. Is a point. Therefore, even in the image transfer in the printing 905 after the decompression 904, the image data is transferred in the corrected image data 910 format.

  The correction process 902 is a correction process for preventing the color shift described with reference to FIGS. 3 to 6A to 6F. When the printer engine 301 receives the corrected image data transferred from the controller 302 at the time of printing, the correction is canceled at the time of image formation, and a desired image can be output.

  Next, a description will be given of a case where print output is performed in the controller 302 that constitutes a printer that requires color misregistration correction processing. For the image data to be stored in the HDD or RAM 900, it is optimal that the corrected image data is in a compressed state in that it is read out and printed out a plurality of times such as electronic sorting.

  When the corrected image data is stored in the HDD or RAM in the storage destination, the correction data 911 used in the correction process is also managed in association with the image before correction according to the subsequent use. It can be returned.

  FIG. 11 is a flowchart for explaining a procedure for updating the correction state of the image data stored in the HDD or RAM when the controller that constitutes the printer that needs the color misregistration correction process updates the correction value. FIG.

  First, the controller 302 determines whether or not the correction value has been updated (S101), and does not perform any particular processing until the correction value is updated. On the other hand, when the correction value is updated, first, the image that has been corrected in the HDD or RAM with the previous correction data and stored in a compressed state is decompressed (S102). Next, as a process for updating (recorrecting) the correction image with the latest correction data, reverse correction is performed to return the image corrected with the previous correction data to the state before correction (S103). Further, the state image before correction is corrected again based on the latest correction data (S104). Finally, the recorrected image is compressed and stored in the HDD or RAM (S105), and the correction state update process is terminated.

  Note that these correction state update processes may be performed on all image data stored in the HDD or RAM, or may be performed on only some preferential images. Further, the correction state update process may be performed immediately after the correction parameter is changed. This is performed in the background without stopping other print or image saving job processing at a specified timing (every time set, set time, when there are no more jobs to be executed, etc.) There may be.

  FIG. 12 shows data for explaining processing for updating the correction state of image data stored in the HDD or RAM when a controller constituting a printer that requires color misregistration correction processing updates the correction value. FIG.

  As described with reference to FIG. 11, the previous correction state image data 1006 stored in the HDD or RAM 1000 is recorrected 1005 after decompression 1001 according to the previous correction data 1008 and the latest correction data 1010. After the compression 1004, the image data 1012 in the latest correction state is stored again in the HDD or RAM 1000.

  FIG. 13 is a flowchart illustrating a procedure for printing out a stored job stored in the HDD or RAM by a controller that configures a printer that requires color misregistration correction processing.

  First, the controller 302 expands an image that has been corrected in the HDD or RAM with the previous correction data and stored in a compressed state (S201). Next, it is determined whether the correction state of the target image data is a correction state according to the latest correction data (S202). If the correction state is according to the latest correction data, the process of S205 is performed.

  On the other hand, if the correction state is not in accordance with the latest correction data, the image corrected with the previous correction data is returned to the state before correction as a process for updating (recorrecting) the correction image with the latest correction data. The reverse correction is performed (S203). Further, the state image before correction is corrected again based on the latest correction data (S204).

  Finally, in S205, the corrected image data is transferred to the printer engine 301, and the print output process of the saved job is completed.

  FIG. 14 is a data flow diagram for explaining print output processing of a saved job stored in the HDD or RAM by the controller that constitutes the printer that needs color misregistration correction processing. As described with reference to FIG. 13, the previous correction state image data 1106 stored in the HDD or RAM 1100 is recorrected 1105 according to the previous correction data 1108 and the latest correction data 1110 after decompression 1101. Then, printing 1104 is performed according to the latest corrected image data 1111.

[Other embodiments]
Note that the present invention can be applied to a system constituted by a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), but an apparatus (for example, a copying machine, a facsimile machine, etc.) comprising a single device. ).

  Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or apparatus, and to perform a computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read out by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

  When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above.

1 is a schematic cross-sectional view for explaining an embodiment of a color image forming apparatus according to the present invention. FIG. 4 is an image diagram for explaining a shift of a main scanning line scanned on a photosensitive drum which is an image carrier. FIG. 6 is a block diagram for explaining an operation of a color misregistration correction process for correcting color misregistration caused by the inclination or curvature of a scanning line performed in the present embodiment. It is the figure which showed the example of the information memorize | stored in a color shift amount memory | storage part in the table | surface. (A) thru | or (c) is an image figure for demonstrating the operation | movement content in which a coordinate conversion part correct | amends the shift | offset | difference amount of the integer part of color shift correction amount (DELTA) y, and the color shift of a line unit. (A) thru | or (f) is an image figure for demonstrating the operation | movement content which corrects the color shift correction below a pixel unit which the gradation correction part performs, ie, correct | amends the shift amount below the decimal point of color shift correction amount (DELTA) y. 1 is a system configuration diagram of an image forming apparatus of the present invention. It is a block diagram which shows the structural example of the controller in FIG. FIG. 6 is a diagram for explaining a data flow when a controller that configures a printer that does not need color misregistration correction performs print output. FIG. 6 is a diagram for explaining a data flow when a controller that configures a printer that needs color misregistration correction processing performs print output. FIG. 5 is a flowchart for explaining a procedure for updating a correction state of image data stored in an HDD or a RAM when a controller that configures a printer that requires color misregistration correction processing updates a correction value; is there. FIG. 7 is a data flow diagram for explaining processing for updating a correction state of image data stored in an HDD or a RAM when a controller that configures a printer that requires color misregistration correction processing updates a correction value; . FIG. 6 is a flowchart illustrating a procedure for printing out a stored job stored in an HDD or a RAM by a controller that configures a printer that requires color misregistration correction processing. FIG. 6 is a data flow diagram for explaining print output processing of a stored job stored in an HDD or a RAM by a controller that configures a printer that requires color misregistration correction processing.

Explanation of symbols

101 Data processing apparatus 102 Image forming apparatus (laser beam printer)
104 Panel section 301 Printer engine 302 Printer controller 303C, 303M, 303Y, 303K Color shift amount storage section 304 Image generation section 305 Color conversion section 306 Bitmap memories 307C, 307M, 307Y, 307K Color shift correction amount calculation sections 308C, 308M, 308Y, 308K Color misregistration correction units 309C, 309M, 309Y, 309K Halftone processing units 310C, 310M, 310Y, 310K Exposure units 311C, 311M, 311Y, 311K Photosensitive drums 410C, 410M, 410Y, 410K PWM
600C, 600M, 600Y, 600K Coordinate converters 602C, 602M, 602Y, 602K First DMAC
603C, 603M, 603Y, 603K Second DMAC
604C, 604M, 604Y, 604K Gradation correction unit 701 Panel interface unit 702 Host interface unit 703 Intermediate data creation unit 704 ROM
705 RAM
706 Engine interface unit 707 DMA control unit 708 Rendering unit 709 CPU
710 Non-volatile memory 711 HDD
712 CPU bus

Claims (8)

In an image forming apparatus that forms an image based on at least print data supplied from a data processing apparatus,
Image development means for interpreting the print data supplied from the data processing device and developing it into bitmap image data;
Correction means for correcting color misalignment or distortion of an image generated in image formation with correction data for the image data developed by the image development means;
Correction data storage means for storing the correction data used in the correction means;
Image data storage means for storing the image data developed by the image development means or the image data corrected by the correction means in a storage device in a predetermined format;
Correction data management means for storing and managing in the storage device the image data stored by the image data storage means in association with the correction data used when corrected by the correction means;
Correction data updating means for updating the contents of the correction data stored in the correction data storage means when the correction data used in the correction means needs to be changed;
The correction data managed in association with the image data by the correction data management means when there is a print instruction from the user for the image data saved in the storage device by the image data saving means Determining means for determining whether or not the same content as the correction data updated by the correction data update means;
Re-correction means for correcting again according to the correction data managed in association with the image data and the correction data updated by the correction data update means when the determination means determines that the difference is different from the latest correction data. An image forming apparatus comprising: In an image forming apparatus that forms an image based on at least print data supplied from a data processing apparatus,
Image development means for interpreting the print data supplied from the data processing device and developing it into bitmap image data;
Correction means for correcting color misalignment or distortion of an image generated in image formation with correction data for the image data developed by the image development means;
Correction data storage means for storing the correction data used in the correction means;
Image data storage means for storing the image data developed by the image development means or the image data corrected by the correction means in a storage device in a predetermined format;
Correction data management means for storing and managing in the storage device in association with the correction data used when the image data stored by the image data storage means is corrected by the correction means;
Correction data updating means for updating the contents of the correction data stored in the correction data storage means when the correction data used in the correction means needs to be changed;
As the latest correction data is updated by the correction data update unit, the image data stored in the storage device is managed in association with the image data by the image data storage unit at a predetermined timing. An image forming apparatus comprising: the correction data that has been corrected; and recorrection means that corrects the correction data again according to the latest correction data. In an image forming apparatus that forms an image based on at least print data supplied from a data processing apparatus,
Image development means for interpreting the print data supplied from the data processing device and developing it into bitmap image data;
Correction means for correcting color misalignment or distortion of an image generated in image formation with correction data for the image data developed by the image development means;
Correction data storage means for storing the correction data used in the correction means;
Image data storage means for storing the image data developed by the image development means or the image data corrected by the correction means in a storage device in a predetermined format;
Correction data management means for storing and managing in the storage device the image data stored by the image data storage means in association with the correction data used when corrected by the correction means;
Correction data updating means for updating the contents of the correction data stored in the correction data storage means when the correction data used in the correction means needs to be changed;
As the latest correction data is updated by the correction data update unit, the image data stored in the storage device is managed in association with the image data by the image data storage unit at a predetermined timing. First correction means for correcting again according to the correction data and the latest correction data,
The correction data managed in association with the image data by the correction data management means when there is a print instruction from the user for the image data saved in the storage device by the image data saving means Determining means for determining whether or not the same content as the latest correction data stored in the correction data storage means;
And a second re-correction unit that corrects again in accordance with the latest correction data when the determination unit determines that the difference is different from the latest correction data. An image forming apparatus. The image forming apparatus includes:
A photosensitive member, exposure means for irradiating the photosensitive member with a light beam modulated by each color signal to form an electrostatic latent image, and developing the electrostatic latent image formed on the photosensitive member by the exposing means; A plurality of image stations each having a developing means for converting the image forming means and a transfer means for transferring each color image visualized by the developing means to transfer paper, and sequentially conveying the color images formed by the image stations. An image forming apparatus that forms an image by transferring to a transfer material conveyed by means,
The correction means includes
Color misregistration amount storage means for storing the color misregistration amount for each image station;
Color misregistration correction amount computing means for computing a color misregistration correction amount based on the color misregistration amount obtained from the color misregistration amount storage means;
The image forming apparatus according to claim 1, further comprising: a color misregistration amount correcting unit that corrects the color misregistration amount based on a calculation result of the color misregistration correction amount calculating unit.   5. The image forming apparatus according to claim 4, wherein the color misregistration amount correcting unit includes a coordinate conversion unit that corrects a color misregistration in units of pixels and a gradation correction unit that corrects a color misregistration in units of pixels. apparatus. In an image forming method for forming an image based on at least print data supplied from a data processing device,
An image expansion step of interpreting the print data supplied from the data processing device and expanding it into bitmap image data;
A correction step of correcting color misregistration or distortion of an image generated in image formation with correction data with respect to the image data developed in the image development step;
A correction data storage step for storing the correction data used in the correction step;
An image data storage step of storing the image data expanded by the image expansion step or the image data corrected by the correction step in a storage device in a predetermined format;
A correction data management step for storing and managing in the storage device in association with the correction data used when the image data stored by the image data storage step is corrected by the correction step;
A correction data update step for updating the content of the correction data stored in the correction data storage step when a need to change the correction data used in the correction step occurs;
The correction data managed in association with the image data by the correction data management step when there is a print instruction from the user for the image data stored in the storage device by the image data storage step Is a determination step of determining whether or not the same content as the correction data updated by the correction data update step;
The correction data managed in association with the image data and the re-correction step of correcting again according to the updated correction data when the determination step determines that the difference is different from the updated correction data. An image forming method.   After the correction data update step, instead of the determination step and the recorrection step, the latest correction data is updated by the correction data update step, and the image data storage step is performed at a predetermined timing. 7. The method according to claim 6, further comprising a re-correction step of correcting the image data stored in the storage device again according to the correction data managed in association with the image data and the latest correction data. The image forming method described. The image data stored in the storage device by the image data storage step at a predetermined timing as the latest correction data is updated by the correction data update step after the correction data update step. The image forming method according to claim 6, further comprising a first re-correction step of correcting again according to the correction data managed in association with the image data and the latest correction data.

Images