JP2012128175A - Image forming system, image forming device, and control method and program therefor - Google Patents

Abstract

In the prior art, feedback based on the difference from the originally desired color is reflected in the printing of the next page and subsequent pages, and the page itself in which the color shift has occurred cannot be dealt with. .
An image forming apparatus includes: a printing unit that prints an image on a recording medium based on print data; a printing result detection unit that detects a color of an image printed on the recording medium; and the printing result detection unit. Based on the difference detected by the color value difference detecting means and the color value difference detecting means for detecting the difference between the detected color and the color designated in the print data corresponding to the detected color, the print data A difference image generating unit that generates a difference image indicating a color difference between an image and an image printed on the recording medium; and a communication unit that transmits the generated difference image to another image forming apparatus. It is characterized by.
[Selection] Figure 3

Description

  The present invention relates to an image forming system, an image forming apparatus, a control method thereof, and a program.

  Conventionally, a technology for connecting an image forming apparatus that performs color printing and an image forming apparatus that performs clear printing, and a tandem type image forming apparatus equipped with two printer engines have been proposed (see Patent Document 1).

  In such a tandem-type image forming apparatus, a technique for detecting a color shift of a print result and feeding back the color shift result as correction information at the time of printing the next page is known (see Patent Document 2). ). This is to detect a color shift between the result of printing by the first printer engine and the originally intended print result and to give feedback of “color shift” to the second printer engine.

JP 2008-145595 A Japanese Patent Laid-Open No. 11-102091

  In the conventional technology as described above, the feedback is reflected in the printing of the next page and subsequent pages, and the page itself in which the color shift has occurred cannot be dealt with.

  An image forming apparatus according to the present invention includes a printing unit that prints an image on a recording medium using print data, a printing result detection unit that detects a color value of an image printed on the recording medium, and the printing result detection unit. A color value difference detection unit that detects a difference between the color value detected in step S3 and a color value specified in the print data corresponding to the detected color value, and a difference detected by the color value difference detection unit, Difference image generating means for generating a difference image indicating a difference in color value between the image of the print data and the image printed on the recording medium, and the image generated by the other image forming apparatus And a communication means for transmitting to print on the printed recording medium.

  According to the present invention, it is possible to obtain a printed matter having no color misregistration on all pages of print data.

1 is a diagram illustrating an example of a hardware configuration of an image forming system according to Embodiment 1. FIG. 1 is a diagram illustrating an internal configuration centering on a printer unit of an image forming apparatus constituting an image forming system. 2 is a diagram illustrating a configuration of a software module of the image forming system according to the first embodiment. FIG. 3 is a flowchart showing a flow of processing in the first image forming apparatus. It is a figure explaining the process in which a difference image is produced | generated. 6 is a flowchart showing a flow of processing in the second image forming apparatus. 6 is a diagram illustrating a configuration of a software module of an image forming system according to a second embodiment. FIG. 6 is a flowchart illustrating a flow of processing in the first image forming apparatus according to the second embodiment. FIG. 10 is a diagram illustrating a configuration of a software module of an image forming system according to a third embodiment. 14 is a flowchart illustrating a flow of processing in the second image forming apparatus according to the third embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
(Embodiment 1)
The image forming system according to the present embodiment includes a first image forming apparatus and a second image forming apparatus, and both the image forming apparatuses perform color printing using CMYK toner. Two image forming apparatuses connected to each other can perform printing processing in conjunction with each other.

  FIG. 1 is a diagram illustrating an example of a hardware configuration of an image forming system according to the present embodiment. As can be seen from this figure, there is no fundamental difference in configuration between the image forming apparatus 100 as the first image forming apparatus and the image forming apparatus 200 as the second image forming apparatus. A brief description is given below.

  Reference numerals 10 and 20 denote CPUs which control various processes for executing printing in accordance with a user's print instruction. This control is executed based on a control program stored in advance in the ROMs 11 and 21 and the like. The control program includes an OS (operating system) for performing time-sharing control in units of load modules called tasks according to a system clock. The control program includes a plurality of load modules that are executed and controlled in units of functions by the OS.

  Reference numerals 12 and 22 denote HDDs, which store various data such as print data, information, and processing results.

  Reference numerals 13 and 23 denote printer units, which form images on a recording medium (for example, paper) based on instructed print data. Details of the printer units 13 and 23 will be described later.

  Reference numerals 14 and 24 denote network interfaces for receiving print data transmitted via the network 30 and transmitting various commands to the other image forming apparatus.

  Reference numerals 15 and 25 denote operation units having a display function for displaying statuses of input information and processing results, and an input function for receiving input from the user for various settings.

  Reference numeral 30 denotes a network such as a LAN, which connects the image forming apparatus 100 and the image forming apparatus 200 to each other. Further, it is also connected to an external device such as a PC (not shown). For example, when a user instructs printing from the PC, print data is transmitted to the image forming apparatus 100 and / or the image forming apparatus 200 via the network 30. .

  FIG. 2 is a diagram showing an internal configuration centering on the printer unit of the image forming apparatuses 100 and 200, and shows how an image is formed on a sheet as a recording medium in the image forming system. Yes.

(Internal configuration of image forming apparatus 100)
An exposure control unit 101 includes a laser light source, a polygon scanner, and the like.

  Reference numeral 102 denotes a photosensitive drum irradiated with laser light from the exposure control unit 101. The exposure control unit 101 modulates laser light based on an image signal that has undergone predetermined image processing, and irradiates the photosensitive drum 102.

  Reference numeral 103 denotes a pre-exposure lamp for discharging the photosensitive drum 102.

  Reference numeral 104 denotes a primary charger that charges the photosensitive drum 102.

  An intermediate transfer member 105 temporarily holds an image developed on the photosensitive drum 102.

  A primary transfer roller 106 transfers an image to the intermediate transfer member 105.

  Reference numeral 107 denotes a cleaning device that removes residual toner on the photosensitive drum 102 and the intermediate transfer member 105.

  Reference numerals 108 to 111 denote developing units for developing an image formed on the surface of the photosensitive drum 102 by the laser beam from the exposure control unit 101 with an electrostatic latent image, and have four colors C, M, Y, and K. Each is filled with toner.

  The photosensitive drum 102 is rotated by a motor (not shown), and after being charged to a desired potential by the primary charger 104, the laser light from the exposure control unit 101 exposes the photosensitive drum 102. Thereby, an electrostatic latent image is formed on the photosensitive drum 102. Thereafter, the developing device 108 for the first color moves so as to come into contact with the photosensitive drum 102, and the toner in the developing device 108 is electrostatically attached to the electrostatic latent image, so that the first color is placed on the photosensitive drum 102. The toner image is formed. Then, the first color toner image formed on the photosensitive drum 102 is primarily transferred to the intermediate transfer member 105 by the primary transfer roller 106. Next, the developing device 109 for the second color moves so as to be in contact with the photosensitive drum 102. Subsequently, a position where the leading edge of the first color toner image primarily transferred onto the intermediate transfer member 105 and the leading edge of the second color toner image developed on the photosensitive drum 102 both face the primary transfer roller 106; At this timing, the laser beam from the exposure control unit 101 is irradiated. As a result, an electrostatic latent image of the second color is formed on the photosensitive drum 102, and the toner in the developing device 109 is electrostatically attached to the electrostatic latent image, and the second color of the electrostatic latent image is formed on the photosensitive drum 102. A toner image is formed. Thereafter, the toner image of the second color on the photosensitive drum 102 is superimposed on the toner image of the first color which is primarily transferred onto the intermediate transfer member 105. The same superposition is repeated for the third color toner image and the fourth color toner image, and the four color full color toner image is primarily transferred onto the intermediate transfer member 105.

  In addition, the image forming apparatus 100 includes a paper feed cassette 112 for stacking paper.

  The paper loaded in the paper feed cassette 112 is fed by a pickup roller 113 that feeds paper into the apparatus. Paper can also be fed from a paper feed tray (no reference sign).

  Reference numeral 114 denotes a paper feed roller that conveys the paper fed into the apparatus toward the registration roller 115. The registration roller 115 is driven so that the leading edge of the conveyed paper and the leading edge of the unfixed toner image formed on the intermediate transfer member 105 coincide with each other, and a transfer bias is applied to the secondary transfer roller 116. It is done. As a result, the image is transferred onto the paper.

  Reference numeral 117 denotes a conveyance belt that conveys the sheet onto which the image has been transferred to the fixing device 118.

  Reference numeral 118 denotes a fixing device that fixes the toner image transferred onto the paper by applying pressure and heating. The fixing device 118 includes an upper heat roller and a fixing belt that is pressure-bonded from the lower portion, and fixes the transferred toner image by passing a sheet therebetween.

  A paper discharge roller 119 discharges the paper to the outside of the image forming apparatus 100.

  Reference numeral 120 denotes a sensor that detects a printing result (color of an image formed on a sheet). The purpose of the sensor 120 is to detect a printing result in the image forming apparatus 100 for printing processing (correction) in the image forming apparatus 200. Therefore, the sensor 120 is provided at a position downstream of the fixing device 118. In this embodiment, it is provided between the fixing device 118 and the paper discharge roller 119, but is not limited thereto. Any position can be used as long as the object can be achieved.

(Internal configuration of image forming apparatus 200)
The configuration of the image forming apparatus 200 is basically the same as that of the image forming apparatus 100. That is, 201 is an exposure control unit, 202 is a photosensitive drum, 203 is a pre-exposure lamp, 204 is a primary charger, 205 is an intermediate transfer member, 206 is a primary transfer roller, 207 is a cleaning device, and 208 to 211 are developing devices. is there. Reference numeral 215 denotes a registration roller, 216 denotes a secondary transfer roller, 217 denotes a conveyance belt, 218 denotes a fixing device, and 219 denotes a paper discharge roller.

  Reference numeral 213 denotes a paper feed roller for taking the paper that has undergone the printing process in the image forming apparatus 100 into the image forming apparatus 200 and transporting it toward the registration roller 215.

  There is no paper feed cassette on the image forming apparatus 200 side, and therefore there is no roller corresponding to the pickup roller 113 for feeding paper into the apparatus.

  Note that the image forming apparatuses 100 and 200 according to the present embodiment have a structure capable of printing only on one side of a sheet for convenience of explanation. However, it is naturally possible to employ an image forming apparatus having a mechanism for reversing paper for double-sided printing, and an image forming apparatus and an image forming system having such a double-sided printing function are included in the present invention. Needless to say, it is within the scope of the above.

  Then, a buffer is provided between the image forming apparatus 100 and the image forming apparatus 200, and the paper discharged from the image forming apparatus 100 is once transported to the image forming apparatus 200, and the transported paper is the image forming apparatus 200. Two devices may be connected so that paper is fed to the printer.

  FIG. 3 is a diagram showing the configuration of the software module of the image forming system according to the present embodiment.

  Before describing each software module, reference numerals 330 to 360 in the figure will be described.

  First, reference numeral 330 denotes print data relating to a user's print instruction, which is input as bitmap format image data (hereinafter referred to as “bitmap data”) for use in print processing in the first image forming apparatus. That is, when the bitmap data 330 is scanned by a scanner (not shown), or is received as PDL data via the network 30 and is generated by being interpreted by a PDL interpretation unit (not shown). and so on. The image represented by the bitmap data is a final target image expressed in a color desired by the user, and is hereinafter referred to as a “target image”.

  Reference numeral 340 denotes a recording medium (printed material) such as paper on which an image is printed based on the bitmap data 330.

  350 is bitmap data used for the printing process in the second image forming apparatus, and the difference image data generated based on the difference between the target image of the bitmap data 330 and the actual image in the printed matter 340. It is.

  Reference numeral 360 denotes a printed material obtained by printing the difference image on the printed material 340, and is a final printed material created in the image forming system.

  Based on the above, each software module will be described.

  First, the modules 310 to 314 that are components of the image forming apparatus 100 will be described.

  A print processing unit 310 performs print processing (processing for forming an image on a sheet) based on the bitmap data 330 that is a target of a print instruction, and creates a printed matter 340.

  Reference numeral 311 denotes a print result detection unit that performs processing for detecting the color of an image formed on the printed matter 340 in units of pixels. In this embodiment, since one pixel is formed by one dot, it can also be referred to as detection in dot units.

  A color value difference detection unit 312 includes a color (color value) detected by the print result detection unit 311 and a color (color value) designated by the bitmap data 330 corresponding to the detected color (color value). The difference (color difference) is detected using the sensor 120.

  A difference image generation unit 313 generates a difference image indicating a color difference between an image on the printed matter 340 and a target image in the bitmap data 330 based on the color difference detected by the color value difference detection unit 312. I do.

  A data communication unit 314 performs processing such as transmitting the generated difference image data 350 to the image forming apparatus 200 via the network I / F 14.

  Next, the modules 320 and 321 that are components of the image forming apparatus 200 will be described.

  Reference numeral 320 denotes a data communication unit that performs a process of receiving the differential image data 350 transmitted from the image forming apparatus 100 via the network I / F 24.

  Reference numeral 321 denotes a print processing unit, which performs a process of forming (printing) an image based on the received difference image data 350 on the printed matter 340 that has been conveyed after the printing process in the image forming apparatus 100 is completed.

  FIG. 4 is a flowchart showing a flow of processing in the image forming apparatus 100 which is the first image forming apparatus. This process is realized by the CPU 10 executing a program read from the ROM 11 or HDD 12 into the RAM 11.

  In step 400, the image forming apparatus 100 receives a print instruction from the user together with print data from a not-shown PC or the like via the network 30.

  In step 410, the print processing unit 310 forms an image on a sheet (executes the print process) based on the received print data. As described above, when the print data sent together with the print instruction is PDL data, the print processing unit 310 executes print processing after the PDL interpretation unit (not shown) converts the print data into the bitmap data 330. The paper (printed material 340) that has been subjected to the printing process is conveyed to the position of the sensor 120.

  In step 420, the print result detection unit 311 detects the print result from the printed material 340, that is, the color of the image formed on the paper. The color detected by the print result detection unit 311 is measured by RGB values. Then, the measured value is converted into RGB values depending on the first image forming apparatus 100 by the ICC profile, color matching processing is performed, and converted into CMYK values by color separation processing. (Details of this color matching processing are as described in, for example, JP-A-2005-142769, which is a publicly known document).

  The method of detection depends on the capabilities of the sensor 120. For example, when the sensor 120 has the ability to detect only CMYK single color, only the color of the portion printed with the CMYK single color in the image formed on the printed material 340 is detected. In this case, it is necessary to know which pixels (dots) of the printed image are printed in a single color of CMYK prior to detection. Therefore, a part (dot) for which printing with a single color of CMYK is designated in the bitmap data 330 is specified by coordinates. And the location of the specified coordinate is detected with a pinpoint. On the other hand, when the sensor 120 has the ability to detect even mixed colors, all colors constituting the image formed on the printed material 340 are detected in dot units.

  In step 430, the color value difference detection unit 312 detects the difference between the color detected by the print result detection unit 311 and the color specified in the bitmap data 330 corresponding to the color. For example, it is assumed that the detected color value is C = M = Y = K = 250 in the dot X whose color value specified in the bitmap data 330 is C = M = Y = K = 255. In this case, for the CMYK values (Xc, Xm, Xy, Xk) of the dot X, (5 / 255Xc, 5 / 255Xm, 5 / 255Xy, 5 / 255Xk) are the difference values indicating the color misregistration. Here, when the sensor 120 has a mixed color detection capability and can detect all the colors, the color difference between the printed material 340 and the bitmap data 330 is obtained by simple comparison for each dot. On the other hand, when only the CMYK single color can be detected, the color difference is obtained by simple comparison for the CMYK single color portion, and the color difference is obtained by calculation such as linear interpolation for the other color mixture portions. For example, as a result of detecting a CMYK single color portion, it is determined that a color shift of 5% is generated for C and 10% for M. In this case, for the mixed color dot Y composed of C and M, the value obtained by multiplying the C value by 5% and the M value by 10% is the difference value indicating the color misregistration at the dot Y. Become.

  If a color difference is detected as a result of such processing, the process proceeds to step 440. If no color difference is detected, the process proceeds to step 460.

  In step 440, the difference image generation unit 313 generates a difference image indicating the color difference between the image printed on the printed material 340 and the target image in the bitmap data 330 based on the detected color difference. That is, the difference image generation unit 313 generates bitmap data of an image that compensates for the color shift (color shift from the target image) occurring in the printed material 340.

  FIGS. 5A to 5C are diagrams illustrating a process in which a difference image is generated. 5A is a target image in the bitmap data 330, FIG. 5B is an image detected from the printed material 340 as a printing result of the bitmap data 330, and FIG. 5C is a difference indicating a color shift between the two. It is an image. In this example, it is shown that the image of the printed material 340 is printed slightly thin with respect to the target image, and a difference image that compensates for the thinned portion is generated. As a matter of course, a case where color misregistration in the opposite direction to this example occurs, that is, the image of the printed matter 340 may be printed darkly with respect to the target image. As described above, when the first image forming apparatus 100 prints a dark color, the second image forming apparatus 200 cannot perform correction printing using the difference image. Therefore, in order to guarantee the execution of the correction printing in the second image forming apparatus 200, when printing with the first image forming apparatus 100, the color value is always changed to a color value smaller than the original color value, and the color is slightly diluted. You may make it print on. For example, before halftoning, all dots are uniformly reduced by 10% and printed. Thereby, the execution of the correction printing process in the second image forming apparatus 200 is ensured, and the occurrence of color misregistration in the final printed matter 360 can be more effectively suppressed.

  Further, as a result of printing with the first image forming apparatus, the sheet may contract or expand. If the difference image is printed as it is on such a deformed sheet, registration deviation occurs. In consideration of such a case, a larger or smaller difference image may be generated according to the deformed paper. For the enlargement / reduction of the difference image, a known edge extraction technique may be used. For example, graphics or character portions may be extracted and expanded / reduced to the inner / outer outline by a predetermined number of dots (several dots). . Since it is often possible to know in advance from the empirical rule when the paper is reduced / expanded, the type of paper used is detected, and at the same time, the paper is reduced / expanded at a predetermined rate. Should be set. Alternatively, the user may be able to set the enlargement ratio or reduction ratio of the difference image during printing via the operation unit 15. As a result, it is possible to prevent registration deviation from occurring when the second image forming apparatus 200 prints the difference image.

  Furthermore, in the flowchart of FIG. 4, a difference image is generated for all of the color differences detected. However, for example, it is also possible to perform a process in which a difference image is generated only for a case where the detected color difference value exceeds a predetermined threshold value set in advance.

  Here, the description returns to the flowchart.

  In step 450, the data communication unit 314 transmits the generated difference image data 350 to the image forming apparatus 200. When the difference image is not generated, a signal to that effect is transmitted to the image forming apparatus 200.

  In step 460, the image forming apparatus 100 carries out the printed paper (printed material 340) toward the image forming apparatus 200.

  FIG. 6 is a flowchart showing the flow of processing in the image forming apparatus 200 as the second image forming apparatus. This process is realized by the CPU 20 executing a program read from the ROM 21 or the HDD 22 into the RAM 21.

  In step 600, the image forming apparatus 200 loads the paper (printed material 340) unloaded from the image forming apparatus 100 into the apparatus.

  In step 610, the data communication unit 320 receives the difference image data 350 (or a signal indicating that there is no difference image data 350) from the image forming apparatus 100. If the difference image data 350 is received, the process proceeds to step 620. If a signal indicating that there is no difference image data 350 is received, the process proceeds to step 630.

  In step 620, the print processing unit 321 prints the difference image on the printed matter 340 based on the received difference image data 350. Prior to the printing process here, necessary image processing such as halftoning (halftone processing) is performed in advance in an image processing unit (not shown). In this case, it is desirable to use an error diffusion method for halftoning. This is to avoid the occurrence of moire in the final printed product 360. If the error diffusion method is not used for halftoning in the image forming apparatus 200, it is desirable that the image forming apparatus 100 and the image forming apparatus 200 have different halftoning methods. This is because when the same method of halftoning is repeatedly performed on the same image, moire tends to occur in the image.

  In step 630, the image forming apparatus 200 discharges the sheet on which the difference image is printed (or the printed material 340 conveyed from the image forming apparatus 100 as it is) to the outside of the apparatus.

  As described above, according to the image forming system according to the present embodiment, even if color misregistration occurs in the first image forming apparatus, correction is performed in the second image forming apparatus. It is possible to obtain printed matter without color misregistration.

(Embodiment 2)
Usually, an image forming apparatus often has a limit on the amount of toner. For this reason, color misregistration occurs between the base target image and the image on the printed matter due to the toner application amount limitation. Therefore, the second image forming apparatus generates differential image data that compensates for the color misregistration caused by the toner application amount limitation in the first image forming apparatus, and uses the differential image data to print the second image forming apparatus. This will be described as an embodiment. Note that description of parts common to the first embodiment is simplified or omitted, and here, differences will be mainly described.

First, the toner application amount limitation will be described. The applied amount is the weight of toner formed on 1 cm ² . The applied amount can be adjusted by changing the amount of image data that is the amount of data per pixel of image information that has been separated into C, M, Y, and K colors of the bitmap data that is the target image. The maximum image data amount of each color is 100%, and when it is 100%, the maximum density of that color is reached. Therefore, the image data can be changed in the range of 0 to 100%, and various colors can be expressed by superimposing the toners of the respective colors. Theoretically, as the color image information, the maximum image data is 400%. Amount. However, 400% color toner is never used in actual image formation. For example, using a method such as UCR (Under Color Removal), the maximum amount of color toner is usually set to 180% to 240%.

  FIG. 7 is a diagram illustrating a configuration of a software module of the image forming system according to the present embodiment.

  730 is image data in a bitmap format representing the target image, 740 is data of an image (restricted image) in which toner is restricted due to toner application amount restriction, and 750 is a record of paper or the like printed based on the restricted image data 740 It is a medium (printed material). Reference numeral 760 denotes difference image data indicating the difference in color between the target image and the restricted image, and reference numeral 770 denotes a final printed matter obtained by further printing the difference image on the printed matter 750.

  A print processing unit 710 corresponds to the print processing unit 310 of the first embodiment.

  In this embodiment, the difference image data 760 is not generated based on the color difference between the bitmap data 730 that is the target image and the printed material obtained by printing the bitmap data 730. Accordingly, there is no processing unit corresponding to the print result detection unit 311 or the color value difference detection unit 312.

  A toner application amount limiting unit 711 performs processing for generating a limited image in which the toner application amount is suppressed within a certain range so as not to exceed a set limit value. For example, when the toner application amount limit is set to 200%, a process of replacing the target image with a limited image that does not exceed 200% is performed. Specifically, when Xc + Xm + Xy + Xk = Z, which is the sum of the CMYK values (Xc, Xm, Xy, Xk) of dot X, is greater than 200 (200 / Z * Xc, 200 / Z * Xm, 200 / Z * Xy) , 200 / Z * Xk). In this way, the image forming apparatus may be shared in units of toner, instead of uniformly limiting the applied amount for each CMYK toner to a certain amount or less. For example, the toner to be used may be limited and shared, such as printing only C and M in the first image forming apparatus, and printing remaining Y and K in the second image forming apparatus.

  Reference numeral 712 denotes a difference image generation unit, and 713 denotes a data communication unit, which respectively correspond to the difference image generation unit 313 and the data communication unit 314 of the first embodiment.

  A data communication unit 720 and a print processing unit 721 correspond to the data communication unit 320 and the print processing unit 321 of the first embodiment, respectively.

  Since the basic hardware configuration is the same as that of the first embodiment, the description is omitted. However, as described above, there is no processing unit corresponding to the print result detection unit 311, and thus the sensor 120 is not necessary in this embodiment. It becomes.

  FIG. 8 is a flowchart showing the flow of processing in the image forming apparatus 100 as the first image forming apparatus according to the present embodiment. This process is realized by the CPU 10 executing a program read from the ROM 11 or HDD 12 into the RAM 11.

  In step 800, the image forming apparatus 100 receives a print instruction from the user together with print data from a PC (not shown) or the like via the network 30. As in the first embodiment, when the print data sent together with the print instruction is PDL data, it is converted into bitmap data 730 by a PDL interpretation unit (not shown).

  In step 810, the applied toner amount limiting unit 711 determines whether the applied amount of toner of each color in the bitmap data 730 exceeds the set limit value of the applied toner amount. If so, the process proceeds to step 820. If not, the process proceeds to step 860.

  In step 820, as described above, the applied toner amount limiting unit 711 generates a limited image in which the applied amount for each toner is limited so that the applied toner amount falls within the set limit value range. Thereafter, the process proceeds to a printing process using the generated restricted image data 740 and a process of generating a difference image.

    Specifically, first, in step 830, the print processing unit 710 performs print processing using the limited image data 740. In parallel with this, in step 840, the difference image generation unit 712 generates a difference image for supplementing the amount cut by the limitation of the toner application amount. In this case, it is possible to suppress fine scattering of the toner by printing only a portion exceeding a predetermined threshold value, rather than passing all the cuts due to the applied amount restriction to the difference image and printing. In some cases, the image quality is good. For example, assume that the toner application amount limit is set to 200%, and the predetermined threshold value is set to 300%. In this case, if Xc + Xm + Xy + Xk = Z, which is the sum of the CMYK values (Xc, Xm, Xy, Xk) of the dot X, is 300 or less, nothing is printed at the position of the dot X by the second image forming apparatus 200. A difference image that is not used is generated. If Z is greater than 300, the second image forming apparatus 200 generates a difference image that enables printing to compensate for the amount of toner thinned out by the toner application amount restriction at the position of the dot X. To do. In other words, when the toner application amount limit is 200%, dots having a toner amount of 201% to 300% remain as restricted images that are limited by the toner application amount, and dots having a toner application amount of 301% or more. May be printed with an image that is not subject to the toner application amount limitation. As a result, for example, when the toner application amount of the image data to be printed is 201%, the second image forming apparatus 200 does not form a differential image with the toner application amount of 1%. Can be controlled, and the image quality is improved.

  Such a difference image can be generated by changing an algorithm used to create the difference image data.

  In step 850, the data communication unit 713 transmits the generated difference image data 760 to the image forming apparatus 200.

  On the other hand, in step 860 when it is determined in step 810 that the toner application amount limit value has not been exceeded, the print processing unit 710 uses the bitmap data 730 interpreted by a PDL interpretation unit (not shown) as it is. Perform the printing process.

  In step 870, the image forming apparatus 100 carries out the paper (printed material 750) that has been subjected to the printing process in step 830 or 860 toward the image forming apparatus 200.

  The second image forming apparatus 200 performs the printing process based on the received difference image data 760 (or a signal indicating that there is no difference image data 760). Since it is the same, description is abbreviate | omitted.

  As described above, according to the image forming system according to the present embodiment, it is possible to obtain a printed matter corresponding to the original applied toner amount even when the applied toner amount is limited.

(Embodiment 3)
The first embodiment is a mode in which CMYK color printing is performed in both the first image forming apparatus and the second image forming apparatus. Next, a mode in which the first image forming apparatus performs color printing with CMYK toner and the second image forming apparatus performs printing with special color toner in addition to color printing with CMYK toner will be described as a third embodiment. To do. Note that description of parts common to the first embodiment is simplified or omitted, and here, differences will be mainly described.

  FIG. 9 is a diagram illustrating a configuration of software modules of the image forming system according to the present embodiment. Hereinafter, the difference from the first embodiment will be mainly described. In the present embodiment, the clear toner is used as the special color toner. However, the clear toner is an example of the special color toner and is not limited thereto.

  Reference numeral 930 denotes bitmap format image data representing a target image, and 940 denotes a recording medium (printed matter) such as paper on which an image is printed based on the bitmap data 930. Reference numeral 950 denotes difference image data indicating the color difference between the target image represented by the bitmap data 930 and the actual image in the printed material 940. Reference numeral 960 denotes clear image data indicating a position where the clear toner is placed, and reference numeral 970 denotes composite image data obtained by combining the difference image and the clear image.

  Reference numeral 980 denotes a final printed material obtained by further printing a composite image on the printed material 940.

  Based on the above, each software module will be described.

  Modules 910 to 914 that are components of the image forming apparatus 100 correspond to the modules 310 to 314 of the first embodiment. That is, 910 is a print processing unit, 911 is a print result detection unit, 912 is a color value difference detection unit, 913 is a difference image generation unit, and 914 is a data communication unit.

  The components of the image forming apparatus 200 include modules 920 to 922. A module 920 is a data communication unit, 921 is an image composition unit, and 922 is a print processing unit. Among these, the image composition unit 921 performs a process of generating bitmap data 970 of a composite image obtained by combining the image for the special color toner and the difference image.

  Note that the internal configuration of the image forming apparatuses 100 and 200 according to the present embodiment centering on the printer unit is substantially the same as that of the first embodiment. That is, the image forming apparatus 100 is the same, and the image forming apparatus 200 is common except that a developing device for clear toner is added. Therefore, detailed description thereof is omitted.

  FIG. 10 is a flowchart showing the flow of processing in the image forming apparatus 200 as the second image forming apparatus according to the present embodiment.

  In step 1000, the image forming apparatus 200 carries the paper (printed material 940) unloaded from the image forming apparatus 100 into the apparatus.

  In step 1010, the data communication unit 320 receives the difference image data 950 (or a signal indicating that there is no difference image data 950) from the image forming apparatus 100. If the difference image data 950 is received, the process proceeds to step 1020. If a signal indicating that there is no difference image data 950 is received, the process proceeds to step 1040.

  In step 1020, the image synthesis unit 921 synthesizes the image for the special color toner (here, a clear image) obtained by interpretation in the PDL interpretation unit (not shown) and the received difference image to generate one synthesized image. .

  In step 1030, the print processing unit 922 prints the composite image on the printed material 940 based on the composite image data 970.

  On the other hand, when the difference image data 950 is not received in step 1010, in step 1040, the print processing unit 921 prints the clear image on the printed matter 940 using the clear image data 960.

  If the print instruction from the user does not include clear toner printing, only the difference image is printed in step 1030, and no print processing is performed in step 1040.

  In step 1050, the image forming apparatus 200 discharges the sheet on which the composite image (or clear image) is printed out of the apparatus.

  Incidentally, as described in the second exemplary embodiment, the toner amount is usually limited in the image forming apparatus. Also in the image forming apparatus 200 according to the present embodiment, for example, the amount of applied toner in the composite image (the sum of the amount of applied CMYK toner in the difference image and the amount of applied clear toner in the clear image) is set. It is possible that the limit will be exceeded. Therefore, for example, emphasizing that the second image forming apparatus is an apparatus that performs printing with clear toner, and when the toner application amount limit is exceeded, the clear toner application amount is preferentially secured by default. It is conceivable to set so as to. On the other hand, since there is a possibility of giving priority to printing with clear toner and reducing the applied amount of CMYK toner, the user can select whether to give priority to clear toner or CMYK toner via the operation unit 25 during printing. You may do it.

  As described above, according to the image forming system according to the present embodiment, when printing using the special color toner is performed in the image forming apparatus 200, it is possible to obtain a printed matter with no color misregistration while considering printing with the special color toner. It becomes possible.

Claims (12)

Printing means for printing an image on a recording medium using print data;
Printing result detection means for detecting a color value of an image printed on the recording medium;
Color value difference detection means for detecting a difference between the color value detected by the print result detection means and the color value specified in the print data corresponding to the detected color value;
Using the difference detected by the color value difference detecting means, a difference image generating means for generating a difference image indicating a difference in color value between the image of the print data and the image printed on the recording medium;
An image forming apparatus comprising: a communication unit configured to transmit the generated difference image for printing on a recording medium on which the image is printed by another image forming apparatus.   The image forming apparatus according to claim 1, wherein the difference image generated by the difference image generation unit is enlarged or reduced compared to the image of the print data.   The image forming apparatus according to claim 1, wherein the printing unit prints an image of the print data in a color lighter than a color designated by the print data. Printing means for printing an image on a recording medium using print data;
A toner application amount limiting means for generating a limited image limited to a toner application amount smaller than a toner application amount specified in the print data;
Difference image generating means for generating a difference image indicating a difference in color value between the image of the print data and the restricted image using the toner applied amount limited by the toner applied amount limiting means;
An image forming apparatus comprising: a communication unit configured to transmit the generated difference image for printing on a recording medium on which the image is printed by another image forming apparatus. The printing means performs printing using a plurality of toners,
The toner application amount limiting unit generates the limited image by uniformly limiting the toner application amount specified in the print data for each toner or by limiting the toner to be used. Item 5. The image forming apparatus according to Item 4.   The difference image generated by the difference image generation means indicates a color difference of a portion exceeding a preset threshold among the portions where the toner application amount is restricted by the toner application amount restriction device. The image forming apparatus according to claim 5. An image forming apparatus connected to the image forming apparatus according to claim 1 via a network,
Means for receiving a printed recording medium in the image forming apparatus according to any one of claims 1 to 6;
A data communication unit for receiving the difference image;
Printing means for printing an image on the received recording medium using the received difference image;
An image forming apparatus comprising:   The image forming apparatus according to claim 7, wherein the image forming apparatus is a halftone processing unit that performs halftoning prior to printing in the printing unit, and performs halftoning by an error diffusion method. Image synthesis means for synthesizing the received difference image and the spot color toner image to generate a synthesized image;
The image forming apparatus according to claim 7, wherein the printing unit prints an image on the received recording medium using the composite image.   A toner applied amount limiting unit that generates a limited image limited to a toner applied amount that is smaller than a toner applied amount specified in the composite image data, wherein the applied amount of the special color toner has priority over the applied amount of other toners. The image forming apparatus according to claim 9, further comprising a toner application amount limiting unit configured to ensure the toner application amount.   An image forming system comprising: the image forming apparatus according to any one of claims 1 to 6; and the image forming apparatus according to any one of claims 7 to 10. A printing step of printing an image on a recording medium using the print data;
A print result detecting step for detecting a color value of an image printed on the recording medium;
A color value difference detection step of detecting a difference between the color value detected in the print result detection step and the color value designated in the print data corresponding to the detected color value;
A difference image generation step for generating a difference image indicating a difference in color value between the image of the print data and the image printed on the recording medium, using the difference detected in the color value difference detection step;
And a communication step of transmitting the generated difference image for printing on a recording medium on which the image is printed by another image forming apparatus.

Images