JP2016210050A - Correction data generation method of recording device, and data processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a correction data generation method capable of setting correction parameters for each recording element in a process of recording operation for normal real image without recording any special test pattern.SOLUTION: Density unevenness data corresponding to a plurality of recording media respectively are acquired based upon image data for recording a real image in the recording media and read data obtained by reading the real image recording actually in the recording media. Then correction parameters corresponding to the individual recording elements are generated based upon the density unevenness data.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a recording apparatus that records an image using a recording head in which a plurality of recording elements are arranged. In particular, the present invention relates to a method for correcting density unevenness due to variations in individual recording elements.

  Patent Document 1 and the like disclose a head shading (HS) technique for correcting density unevenness caused by variations in ejection characteristics of individual recording elements in an ink jet recording apparatus. In head shading, the input signal of each pixel is corrected according to a correction parameter that is set in advance according to the ejection characteristics of the printing element corresponding to the pixel. For example, a correction parameter that sets an output signal higher than an input signal is set for a printing element that has a smaller discharge amount than the standard and tends to express a lower density. On the other hand, a correction parameter is set so that the output signal is lower than the input signal for a printing element that tends to express a higher density and higher density than the standard. By using such a head shading technique, it is possible to express an equivalent density in the entire area of the recording element.

Japanese Patent Laid-Open No. 10-13684

  By the way, in the ink jet recording apparatus, the ejection characteristics of the recording element may change depending on the usage frequency and environment. Therefore, it is desirable to reset the head shading correction parameter for each printing element at an appropriate timing, and many printing apparatuses having such a correction mode are provided. Normally, in such a correction mode, a test pattern having a uniform density is recorded using all the recording elements, the test pattern is read by a reading sensor, and the position of the recording element is associated with the reading density. A new correction parameter is set for each recording element. At this time, when the recording apparatus is a color inkjet recording apparatus that ejects a plurality of colors of ink, test patterns are recorded in association with individual recording heads, that is, individual ink colors. However, when such a test pattern is recorded, the time for recording the ink and the recording medium and further the test pattern is consumed because of a correction mode unrelated to the actual image, which increases the time cost and running cost. It was.

  The present invention has been made to solve the above problems. Therefore, the object is to provide a correction data generation method capable of setting correction parameters for each recording element in the course of a normal actual image recording operation without recording a special test pattern. It is.

To this end, the present invention is a correction data generation method for recording an image using a recording head in which a plurality of recording elements for recording a color material of a predetermined color are arranged, and records an actual image on a recording medium. A first acquisition step of acquiring first density data corresponding to each of the plurality of recording elements based on image data to be read, and reading the actual image recorded on the recording medium by a reading unit A second acquisition step of acquiring second density data corresponding to each of the plurality of recording elements based on the read data obtained by the step, and based on the first density data and the second density data. Density unevenness data acquisition step for acquiring density unevenness data corresponding to each of the plurality of recording elements, and density density in the plurality of recording elements based on the density unevenness data. And having a generating step of generating correction data corresponding to each of the plurality of recording elements to reduce.

  According to the present invention, it is possible to stably output an image without density unevenness without executing a special correction mode.

It is an internal block diagram of an inkjet recording device. It is a block diagram which shows the control structure of a data processing system. It is a block diagram for demonstrating the process of a recording process and a correction data generation process. It is a figure which shows the relationship between the application amount of the ink with respect to a recording medium, and optical density. It is a flowchart of a correction density acquisition process and a correction parameter generation process. It is a schematic diagram for demonstrating the conversion state of image data. It is a schematic diagram for demonstrating the conversion state of image data. It is a schematic diagram for demonstrating the conversion process of the image data in 2nd Embodiment. It is a flowchart for demonstrating the production | generation process of a correction value parameter. It is a figure for demonstrating the conversion state of image data. It is a figure which shows density unevenness distribution and the correction amount at the time of recording the image of various density | concentrations. (A) And (b) is a schematic diagram which shows the conversion state of image data. It is a schematic diagram for demonstrating the conversion state of image data.

(First embodiment)
FIG. 1 is an internal configuration diagram of a full-line type ink jet recording apparatus 104 that can be used as the recording apparatus of the present invention. When performing a recording operation or a reading operation, the recording medium P is conveyed in the Y direction at a predetermined speed while being sandwiched between a plurality of roller pairs including a conveying roller 80 and a pinch roller 81 connected to a driving source (not shown). . In each of the inkjet recording heads 11 to 14 that discharge cyan (magenta), yellow, and black inks (coloring materials), a plurality of recording elements are arranged at a predetermined pitch in the X direction that intersects the Y direction. Each recording element ejects ink in the Z direction at a frequency corresponding to the conveyance speed of the recording medium P. Each of the recording heads 11 to 14 is disposed between two pairs of rollers, and the recording medium P during recording is kept smooth with respect to the respective discharge port surfaces of the recording heads 11 to 14.

  A plurality of reading elements are arranged at a predetermined pitch in the X direction at the most downstream side in the transport direction, and a scanner 82 (reading unit) capable of reading images recorded by the recording heads 11 to 14 is provided. In the X direction, the array resolution of the reading elements in the scanner 82 is not necessarily equal to the array resolution of the recording elements in the recording heads 11 to 14. However, it is desirable that the resolution is such that the density characteristics of the individual recording elements can be grasped. In the present embodiment, the scanner 82 has RGB three-color sensors and outputs a luminance signal of each color as 8-bit data. The scanner 82 does not always need to read the images recorded by the recording heads 11 to 14 and can read images other than the images recorded by the recording heads 11 to 14.

  FIG. 2 is a block diagram showing a control configuration of a data processing system that can be used as the data processing apparatus of the present invention. The data processing system in this embodiment is mainly configured by the ink jet recording apparatus 104 described in FIG. 1 and a host apparatus 100 connected to the outside.

  In the inkjet recording apparatus 104, the controller 200 includes a CPU 210, a ROM 211, and a RAM 212. A CPU 210 in the form of a microprocessor controls the entire recording apparatus based on programs and various parameters stored in the ROM 211 and using the RAM 212 as a work area. For example, the CPU 210 controls the conveyance motor 206 to drive the conveyance roller 80 and conveys the recording medium P at a predetermined speed. Further, the head driving circuit 202 is controlled to drive the recording heads 11 to 14, and ink is ejected from the individual recording elements toward the recording medium P. Further, the scanner driving circuit 204 is controlled to drive the scanner 82, read an image on the recording medium P, and provide the obtained image data to the CPU 210.

  On the other hand, the host device 100 generates image data that can be recorded by the recording device 104 and provides the image data to the recording device 104, or receives image data read by the scanner of the recording device 104 and performs image processing. The CPU 108 of the host device operates the software of the application 101, the printer driver 103, and the monitor driver 105 via the operating system 102 according to various programs stored in the HD (hard disk) 107 and the ROM 110. At this time, the RAM 109 is used as a work area for executing various processes.

  An application 101, an OS (operating system) 102, a monitor driver 105, and a printer driver 103 are software installed on the host device 100 and executed by the CPU 108. The monitor driver 105 performs processing such as creating data to be displayed on the monitor 106. The printer driver 103 converts the image data transferred from the application 101 to the OS 102 into multi-value or binary image data that can be received by the recording apparatus 104, and transmits the image data to the recording apparatus 104.

  FIG. 3 is a block diagram for explaining the steps of recording processing and correction data generation processing in the data processing system of this embodiment. First, processing steps during the recording process will be described. The image data created by the application 101 of the host device 100 is provided to the printer driver 103 when the user inputs a print command. The image data at this time is 8-bit RGB data. The printer driver 103 sequentially performs pre-stage processing J0002, post-stage processing J0003, density unevenness correction processing J0010, γ correction J0004, binarization processing J0005, and print data creation processing J0006 on the received RGB data.

  In the pre-stage process J0002, a signal value conversion process for associating the color gamut of the image displayed on the monitor 106 with the color gamut that can be expressed by the recording apparatus 104 is performed. Specifically, 8-bit RGB data is converted into 8-bit R′G′B ′ data by referring to a three-dimensional LUT stored in the ROM 110.

  In the post-stage process J0003, the R′G′B ′ data received from the pre-stage process J0002 is converted into CMYK data corresponding to the four colors of ink used by the printing apparatus 104. Specifically, by referring to the three-dimensional LUT stored in the ROM 110, each pixel's 8-bit R′G′B ′ data is converted into 8-bit CMYK data indicating the density of each of C, M, Y, and K. Convert to

  The density unevenness correction process J0010 adjusts the gradation value indicated by the CMYK data of each pixel based on the correction parameter set in association with the recording element that records each pixel. As a result, the 8-bit C, M, Y, and K data are similarly converted into 8-bit C′M′Y′K ′ data. The density unevenness correction process J0010 is a process for reducing density unevenness between recording elements expressed on a recording medium.

  In γ correction J0004, γ correction processing is performed on each of the C ′, M ′, Y ′, and K ′ data received from the density unevenness correction processing J0010. FIG. 4 is a diagram illustrating the relationship between the amount of ink applied to the recording medium and the optical density of the applied region. The horizontal axis indicates the ink application amount for one pixel area of 600 dpi, which corresponds to the number of dots recorded in a unit area, that is, the input signal value. On the other hand, the vertical axis indicates the optical density value expressed when ink corresponding to each applied amount (input signal value) is applied to the recording medium. As can be seen from the figure, the ink application amount and the optical density are in a substantially linear relationship in the low density region where the ink application amount is small, but the linear relationship between them is broken in the region from the medium density to the high density. The γ correction process is a process for correcting the input signal so that the input signal and the optical density expressed on the recording medium have a linear relationship in the entire region. Specifically, by referring to a one-dimensional lookup table prepared for each ink color, each of 8-bit C ′ data, M ′ data, Y ′ data, and K ′ data is similarly converted to 8-bit data. Conversion to C "data, M" data, Y "data, K" data.

  In the binarization processing J0005, each of the 8-bit data C ″, M ″, Y ″, K ″ subjected to γ correction is recorded (1) or not recorded (0) by using a predetermined quantization processing method. Is converted into 1-bit recording data. Further, in the print data creation process J0006, control information related to the recording operation such as the recording medium information, the recording quality information, and the paper feeding method is added to the recording data of each ink color generated in the binarization process J0005. Print data. The print data generated as described above is provided from the host device 100 to the recording device 104.

  In the printing apparatus 104, binary print data among the received print data is rasterized for each ink color and then sent to the head drive circuit 202. The ejection operation is performed by the recording elements arranged on the corresponding recording heads 11 to 14. That is, for the pixels set as recording (1), ink dots are recorded at a predetermined timing by the corresponding recording elements, and no ink dots are recorded for pixels set as non-recording (0). The above is the image processing process in the case of recording a real image.

  Next, the correction data generation process will be described. Referring to FIG. 1 again, in the present embodiment, the actual images recorded by the recording heads 11 to 14 in accordance with the above-described image processing process are scanned by the scanner 82 arranged downstream of the recording heads 11 to 14 in the transport direction. Can be read. In the present embodiment, correction parameters used in the density unevenness correction process J0010 are generated based on image data obtained by reading an image being recorded. Hereinafter, processing steps for generating correction data will be described with reference to FIG.

  The scanner 82 reads the actual image recorded by the recording heads 11 to 14, and the obtained image data is provided to the printer driver 103 of the host device 100 via the scanner driving circuit 204. The image data at this time is 8-bit RGB data.

  In the color separation process J0007, the RGB data received from the printing apparatus 104 is converted into 8-bit density data CMYK data corresponding to the ink color used in the printing apparatus. The conversion method may be equivalent to the pre-processing J0002 and post-processing J0003 already described, or CMYK data corresponding to complementary colors may be obtained from each of the 8-bit RGB data using logarithmic conversion or the like. .

  In the density unevenness data acquisition process J0008, based on the CMYK data obtained from the color separation process J0007, density unevenness data of individual recording elements is generated to obtain a density unevenness distribution. Further, in the correction parameter generation process J0009, a correction parameter is generated based on the density unevenness distribution generated in the density unevenness data acquisition process J0008, and is stored so that it can be used in the density unevenness correction process J0010.

  FIG. 5 is a flowchart for explaining a correction parameter generation process performed by the CPU 108 of the host device in the density unevenness data acquisition process J0008 and the correction parameter generation process J0009. 6 and 7 are schematic diagrams for explaining the conversion state of the image data in the process of executing this processing. Hereinafter, the correction parameter generation process according to the present embodiment will be described with reference to FIGS. 6 and 7 according to the flowchart of FIG. This process is started at the timing when the recording device 104 records an actual image and receives read image data from the scanner 82.

  When this process is started, first, in step S30, the CPU 108 acquires image data for each ink color used when the recording apparatus 104 records an actual image. As such image data, for example, image data output from the post-processing J0003 can be used. Then, the density data corresponding to almost all the printing elements arranged in the printing head is accumulated to the extent that it can be obtained for all the ink colors, and obtained by averaging with a plurality of data arranged in the Y direction. The result is stored as an input density distribution for each ink color. At this time, if the image data is stored as it is as the two-dimensional data, the amount of information increases. Therefore, the image data may be stored with an averaging process. This will be specifically described below.

  FIG. 6 shows actual image examples 60a to 60c for three pages recorded by the recording heads 11 to 14 and a reading density distribution 702 obtained from the reading result. Here, for the sake of simplicity, a rectangular patch C recorded only with cyan ink, a triangular patch M recorded only with magenta ink, and a round patch Y recorded only with yellow ink are mutually in the X direction (recording element). An actual image recorded while shifting the position in the arrangement direction) is shown. For example, paying attention to the cyan head 12, it can be seen that almost all of the recording elements are used to record the patch C on any one of the pages 60a to 60c. The CPU 108 extracts and accumulates image data corresponding to the cyan head 12 from such a plurality of pages of image data, averages the plurality of pixel data for each printing element, and performs input as shown in FIG. A density distribution 701 is obtained. The same processing is performed for magenta, yellow, and black, and the input density distribution of each color is stored.

  In the drawing, an actual image in which cyan, magenta, and yellow are recorded in a single color (primary color) has been described as an example. However, this is for ease of explanation, and many actual images include a plurality of inks. Recorded by color superposition. Whatever the actual image (for example, even if the patch C is green or blue), the image data is extracted based on the image data output from the post-processing J0003. Can be acquired. However, when associating the density data with the read data obtained by reading by the scanner 82 in a later step, it is difficult to purely extract only the color component corresponding to cyan ink from the read data. Therefore, it is preferable that the image data to be accumulated for obtaining the input density distribution 701 is an area recorded with ink of one or two colors as much as possible, and data of an area where three or more colors are mixed is not accumulated.

  In step S30, even if the image data corresponding to all the printing elements cannot be obtained, if a certain amount of input density data is obtained by accumulating the actual image data for several pages, the next time is reached. You may move to a step. In this case, as shown in the input density distribution 701 in FIG. 6, the process proceeds to the next step while including the missing part e where image data cannot be obtained in some places.

  Returning to FIG. In subsequent step S31, CPU 108 generates reference distribution 704 based on input density distribution 701 acquired in step S30. The reference distribution 704 indicates a density distribution that is assumed when an image is recorded according to the input density distribution 701 using a recording head having no variation in ejection characteristics, and further read by the scanner 82. Referring to FIG. 7, the CPU 108 subtracts the influence of the density distribution 703 of the other color ink recorded in the same area on the reading result of the scanner from the input density distribution 701 and inputs the input image data shown in FIG. 4. In consideration of the relationship between the optical density and the optical density, the reference distribution 704 is generated.

  In step S32, the CPU 108 uses the CMYK data after the actual image 60a to 60c is read by the scanner 82 and processed in the color separation process J0007, and the areas (three locations) used to generate the input density distribution 701 in step S30. Extract data for patch C). Then, the density data of each region is connected to generate a read density distribution 702 corresponding to each recording element.

  In step S33, the CPU 108 generates a density unevenness distribution 705 from the difference between the reference distribution 704 generated in step S31 and the read density distribution 702 acquired in step S32. In the density unevenness distribution 705 obtained in this way, density unevenness due to the variation in the ejection characteristics of the individual printing elements is reflected as the density distribution. That is, the density non-uniformity distribution 705 grasps the relative density relationship (density non-uniformity distribution) such as whether each recording element tends to output a higher density or a lower density than the surroundings. I can do it.

  When the density unevenness distribution 705 is generated in step S33, the CPU proceeds to step S34, and generates a correction value distribution 706 based on the obtained density unevenness distribution 705. At this time, in the present embodiment, the correction value distribution 706 is generated independently for each of the regions A, B, and C. Specifically, the average value of the density unevenness distribution is obtained for each of the areas A, B, and C, and the density unevenness distribution is reversed with reference to each average value, and each average value is 0. Is a correction value.

  As in the present embodiment, the density unevenness distribution 705 generated by combining a plurality of areas A, B, and C recorded at different locations at different timings includes input image data of actual images and individual recording elements. In addition to variations in ejection characteristics, the influence of various factors is included. For this reason, even if the data of these plurality of regions are simply connected, it is difficult to obtain continuity between the regions. On the other hand, the gradual density unevenness included in the entire recording head is visually inconspicuous, and there are limited actual images in which a uniform pattern is recorded in the entire recording head. For this reason, in the present embodiment, the correction value distribution is independently generated in units of regions recorded in the same region almost simultaneously.

  However, if a non-ejection recording element is included in each area, the average value of that area is lower than the other areas, and the density correction of the entire area is preferable for one non-ejection. There is a risk that it will not be performed. Therefore, when non-ejection information or the like can be acquired in advance, it is desirable to invalidate the image data corresponding to such a printing element and not use it for calculating the average value. In any case, in the correction value distribution 706, a high value corresponds to a recording element that tends to record a relatively low density, and a low value corresponds to a recording element that tends to record a relatively high density. It will be.

  Returning to the flowchart of FIG. In step S35, the CPU 108 generates correction parameters corresponding to the individual printing elements based on the correction value distribution 706, and stores the correction parameters. The correction parameter is a parameter for reference in the density unevenness correction process J0010 already described with reference to FIG. As the correction parameter, for example, the correction value distribution 706 obtained in step S34 can be used as it is. In this case, the correction value parameter may be added directly to the 8-bit image data output from the post-processing J0003. That is, when the input value for the pixel of the printing element whose correction value is +5 is “128”, the density unevenness correction process J0010 converts this to “133” and outputs it. Further, when the input value for the pixel of the printing element whose correction value is −10 is “128”, the density unevenness correction process J0010 converts this to “118” and outputs it. At this time, a new correction value distribution 707 is generated by reflecting the difference between the average values of the density unevenness distributions in the respective regions used when the correction value distribution is obtained in step S34 in the correction value for each region. Based on this, the correction value parameter 707 may be generated. More specifically, for example, when the average value of the density unevenness distribution in the area A is smaller by “5” than the average value of the density unevenness distribution in the area B or C, the entire correction value of the area A is increased by “5”. It is sufficient to make such adjustments.

  For the recording element corresponding to the missing part e, the processing from step S30 to step S34 is not performed, and when the correction parameter is generated in step S35, the correction parameter already set may be maintained as it is. Such a process will forego generation of correction parameters based on the current actual image.

  In any case, the correction parameter is generated in association with each printing element, and the CPU 108 stores the generated correction parameter in association with each printing element. This process is completed.

  Thereafter, when recording an actual image, in the density unevenness correction process J0010, the input image data CMYK is corrected in accordance with the correction parameters stored in association with the individual recording elements, and the image data C′M′Y. Output as 'K'. Further, by performing the correction parameter generation process described with reference to FIG. 5 every time an actual image is recorded, or at a predetermined cycle or timing, the density unevenness of the recording element can be stabilized over time.

  According to the present embodiment described above, correction parameters for each recording element can be reset in the course of a normal actual image recording operation. Therefore, it is possible to stably output an image without density unevenness without executing a special correction mode.

(Second Embodiment)
FIG. 8 is a schematic diagram for explaining a conversion process of image data in the second embodiment. When the input density distribution 801 and the read density distribution 802 are obtained by connecting a plurality of areas (area A, area B, area C) as in the first embodiment already described, the same recording is performed in the connected area d. There may be multiple data for an element. Hereinafter, such a connection region is also referred to as an overlap region d. In the figure, there is shown a state in which a plurality of data exists in the overlap region d between the region A and the region B, and a missing portion e is present between the region B and the region C.

  The plurality of data existing in the connection area d is obtained from images recorded at different positions at different timings, and which is not correct. In the present embodiment, a process for achieving consistency between regions including each of the plurality of data (region A and region B) will be described. This will be specifically described below.

  Also in this embodiment, the correction parameter generation process is performed according to the flowchart shown in FIG. Here, as shown in FIG. 8, when there are a plurality of data in the connection region d of the input density distribution 801 and the read density distribution 802, the reference distribution 804 obtained in step S31 and the density unevenness distribution 805 obtained in step S33. A plurality of data also exist in the connection region d. As a result, also in the correction value distribution 806 obtained in step S34, a plurality of data exist in the connection region d.

  FIG. 9 is a flowchart for specifically explaining the process in which the CPU 108 generates the correction value parameter in step S35 in the present embodiment. Here, a case where the correction parameter distribution 807 is generated based on the correction value distribution 806 shown in FIG. 8 while maintaining the consistency between the area A and the area B in the connection area d will be described.

  When this process is started, first, in step S101, the CPU 108 corresponds to a correction value corresponding to a recording element included in the connection area d in the area A and a recording element included in the connection area d in the area B. An average value with the correction value is calculated for each printing element.

  In step S102, the CPU 108 obtains a difference between the correction value and the average value for each recording element included in the connection area d of the area A, and calculates an average value Av_A of the differences for the plurality of recording elements. Further, in step S103, the CPU 108 obtains a difference between the correction value and the average value for each recording element included in the connection region d of the region B, and calculates an average value Av_B of the differences for the plurality of recording elements.

  In subsequent step S104, the CPU 108 sets a new correction value for each printing element. Specifically, for the printing elements included in the connection area d, the average value calculated in step S101 is set as a new correction value. For recording elements included in regions other than the connection region included in region A, a value obtained by adding the average value Av_A obtained in step S102 to each correction value is set as a new correction value. For recording elements included in regions other than the connection region included in region B, a value obtained by adding the average value Av_B obtained in step S103 to each correction value is set as a new correction value. At this time, in the area where the missing portion e 2 exists between the area B and the area C, the average value Av_B may be added to the correction density data in accordance with the adjacent area, but the density correction data is held as it is. You may do it. As a result, a new correction value distribution 807 is obtained.

  In step S105, correction parameters corresponding to individual printing elements are generated based on the new correction value distribution. The correction parameter generation method is the same as that in the first embodiment. This process is completed.

  In the above, in the connection region d, the average value of the region A and the region B is obtained, and the correction value of each region is adjusted to the average value. However, for example, the correction value of one area may be adjusted to the other area. In this case, the averaging process as in step S101 is not necessary. Then, the difference between the correction value of the area A and the correction value of the area B is calculated for each recording element in the connection area d, and an average value Av_AB of these differences is obtained. Thereafter, for example, when the correction value of the area A is matched with the area B, the correction value of the area B is left as it is, and the average value Av_AB is added to the correction value of each printing element only for the area A to obtain a new correction value. What is necessary is just to calculate.

  Further, in order to obtain a correction value that is common to the areas A and B in the connection area d, a weighted average process according to the position of the printing element can be employed. Specifically, referring again to FIG. 8, the correction value obtained from the region A and the correction value obtained from the region B of the recording element located at the leftmost end (region A side) of the connection region d. An averaging process is performed with a weight ratio of 1: 0. On the other hand, with respect to the recording element located at the right end (region B side) in the connection region d, the weighting ratio of the correction value obtained from the region A and the correction value obtained from the region B is set to 0: 1 and averaged. Process. For the recording element located in the middle of the connection area d, the ratio of the weights of the correction value obtained from the area A and the correction value obtained from the area B is x: according to the distance x from the right end of the connection area. An averaging process is performed as (1-x). In this way, it is not necessary to correct the correction values for regions other than the connection region d, and even when there are a plurality of connection regions d, a correction distribution having continuity in the X direction can be relatively easily obtained. Can be obtained.

  According to the present embodiment described above, even when the correction value distribution 806 is generated by connecting a plurality of regions, it is possible to appropriately achieve consistency between the plurality of regions, and reliability over the entire region. It is possible to perform high correction. However, in view of the continuity of the correction values in the entire recording head, it is preferable that the number of connection regions is as small as possible. That is, in step S30, it is preferable to acquire the input density distribution 801 and the read density distribution 802 by extracting a combination of areas having a distance as large as possible in the X direction even if some connected areas are included.

  By the way, in the above, the consistency processing between the regions (region A and region B) in the connection region d is performed at the timing of generating the correction value parameter from the correction value distribution 806. Such processing is performed in the density unevenness distribution 805. This state can also be performed after step S33.

  FIG. 10 is a diagram for explaining a conversion state of image data when such processing is performed. In the figure, there is shown a state in which a plurality of data exist in the connection area d between the area A and the area B, and the area B and the area C have a missing part e. The CPU 108 examines the density unevenness distribution 1305 and averages the density value corresponding to the recording element included in the connection area d in the area A and the density value corresponding to the recording element included in the connection area d in the area B. A value is calculated for each recording element. Then, the difference between the density value and the average value is obtained for each printing element included in the connection area d of the area A, and the average value Av_C of the differences is calculated for the plurality of printing elements. On the other hand, the difference between the density value and the average value is obtained for each recording element included in the connection region d of the region B, and the average value Av_D of the differences is calculated for the plurality of recording elements.

  Thereafter, a new density value is set for each recording element. Specifically, for the recording elements included in the connection region d, the calculated average value is set as a new correction value. For recording elements included in areas other than the connection area d included in the area A, a value obtained by adding Av_C to each density value is set as a new density value. For recording elements included in areas other than the connection area d included in the area B, a value obtained by adding Av_D to each density value is set as a new density value. As a result, a new density unevenness distribution 1305a having consistency between the regions A and B can be obtained. In the case of this example as well, the density value of one region may be matched with the other, as in the case of obtaining consistency using correction values, or from the density value obtained from region A and region B. The averaging process may be performed by setting the weighting ratio of the obtained density values to x: (1-x).

  For the region C existing via the missing portion e, the density value may be managed independently of the region A and the region B as in the above embodiment, but the consistency between the region A and the region B You may make it adjust at the timing which takes. For example, in the new density unevenness distribution 1305a, the average value M of the density values of the areas A, B, and C is calculated, and adjustment is performed so that the average value of each area matches the average value M. A new density unevenness distribution 1305b can be obtained. In this case, if the recording element included in the missing portion e is uniformly associated with the average value M, a continuous density unevenness distribution 1305b is obtained for all the recording element regions, and a correction parameter is generated based on the distribution. I can do it.

(Third embodiment)
FIG. 11 is a diagram showing the density unevenness distribution and the correction amount obtained therefrom when images with various recording duties are recorded using the same recording head. The upper row shows input images with low duty for all printing elements, the middle row shows input image data with medium duty for all printing elements, and the lower row shows high duty for all printing elements. When the input image data is input, FIG.

  In either case, density unevenness corresponding to variations in the ejection characteristics of the recording elements occurs, but the amplitude (the degree of density variation) is greatest when an image with a medium duty is recorded. Therefore, the correction value generated using the medium duty image has a larger fluctuation than the correction value generated using the low duty or high duty image. For this reason, if there is a mixture of areas where correction processing is performed using a medium-duty actual image and areas where correction processing is performed using a low-duty or high-duty actual image, the level of correction is excessive or insufficient even within the same print head. May occur. In the present embodiment, in view of such a situation, the input density distribution and the read density distribution are generated by connecting data in regions as close to recording duty as possible.

  12A and 12B are schematic diagrams for explaining the conversion state of the image data in the present embodiment. FIG. 12A shows an example of an actual image for three pages. Here, patches recorded only with cyan ink are shown as squares C1 to C5. In the figure, C1 and C2 are uniform patterns recorded by the same area A of the recording head, but the recording duty of C1 is higher (darker). C4 and C5 are uniform patterns recorded by the same area C of the recording head, but the recording duty is higher (darker) for C4.

  FIG. 12B shows a conversion state of image data with respect to an actual image as shown in FIG. The input density distribution 1101, read density distribution 1102, and other color ink density distribution 1103 are managed for each patch, and a plurality of data exist for the same printing element (area). In this embodiment, a plurality of data is prepared for the same area as described above, and a combination with the smallest variation in recording duty in the recording element arrangement direction (X direction) is selected in each area. That is, when the input density data 1101 as shown in FIG. 12B is obtained, the patch C1 data is selected for the region A, the patch C3 data is selected for the region B, and the patch C4 data is selected for the region C. Then, a correction parameter is generated using this.

  Also in this embodiment, the correction parameter generation process can be performed basically in accordance with the flowchart shown in FIG. The patch selection in the same region, that is, the data extraction process corresponding to each printing element can be performed in the state of the reference distribution 1104 after step S31 or in the state of the density unevenness distribution 1105 after step S33. For example, when performing after step S31, the CPU 108 examines the entire reference distribution 1104. The patches C1, C3, and C4 are patched out of the patches C1 to C5 on condition that the average density value is as close as possible between the plurality of areas and that the amplitude of the density value is as small as possible in each area. Extract. Thereafter, the extracted patches C1, C3, and C4 are connected to create a new reference distribution 1104a. In this case, in order to generate the density unevenness distribution 1105 thereafter, the distributions C2 and C5 in the read density distribution 1102 are not used. Therefore, in step S32, the reading operation for C2 and C5 and the storage of data need not be performed.

  On the other hand, when the data extraction process is performed after step S33, the CPU 108 examines the entire density unevenness distribution 1105 and extracts C1, C3, and C4 under the above conditions. Then, at the stage of creating the correction value distribution 1106, the distribution of C2 and C5 is removed, and C1, C3, and C4 are connected to create a continuous correction value distribution 1106.

  According to the present embodiment, since correction data can be generated by extracting a real image that is as uniform as possible in the X direction, it is possible to expect correction processing equivalent to that when a test pattern is recorded. .

(Fourth embodiment)
In the third embodiment, a configuration has been described in which one of these is extracted when there are a plurality of data having different recording duties for each recording element. In contrast, in the present embodiment, a method of extracting a plurality of data having different recording duties (input density data) for the same recording element and generating a plurality of correction parameters corresponding to the individual recording duties will be described.

  FIG. 13 is a schematic diagram for explaining a conversion state of image data in the present embodiment. Here, C6 to C9 reference distributions for the region A, C10 to C13 reference distributions for the region B, and C14 to C17 reference distributions for the region C are obtained from an actual image covering a plurality of pages. Shall be. In the present embodiment, a plurality of combinations with a small variation in recording duty in the recording element arrangement direction (X direction) are extracted from such a reference distribution and connected for each combination. That is, when the reference distribution 1204 as shown in FIG. 13 is obtained, the patch C7, the patch C10, and the patch C14 are combined, and a first set of correction value distributions is generated using the combination. In addition, the patch C8, the patch C11, and the patch C15 are combined, and a second set of correction value distributions is generated using the combination. Further, the patch C9, the patch C12, and the patch C16 are combined, and a third set of correction value distributions is generated using the combination. As a result, three sets of correction value distributions having different recording duties can be generated.

  Also in this embodiment, the correction parameter generation process can be performed basically in accordance with the flowchart shown in FIG. The patch selection, that is, the process of extracting a plurality of data corresponding to each printing element can be performed after step S31 or after step S33, as in the third embodiment. For example, when the processing is performed after step S31, the CPU 108 examines the entire reference distribution 1204, and sets a plurality of combinations of patches such that the average density value is as close as possible and the density value amplitude is as small as possible in each region. Extract. Here, it is assumed that a set of patches C7, C10, and C14, a set of patches C8, C11, and C15, and a set of patches C9, C12, and C16 are extracted. In this case, the CPU 108 connects the first reference distribution connecting C7, C10, and C14, the second reference distribution connecting C8, C11, and C15, and the third reference distribution connecting C9, C12, and C16. A reference distribution is created, and the data of patches C6 and C17 are removed.

  On the other hand, when the data extraction process is performed after step S33, the CPU 108 examines the entire density unevenness distribution 1105. Under the above conditions, the first correction value distribution in which C7, C10 and C14 are connected, the second correction value distribution in which C8, C11 and C15 are connected, and C9, C12 and C16 are connected. A third correction value distribution is created.

  Thereafter, in step S35, three types of correction parameters are generated based on each of the three types of correction value distributions, and stored in association with the recording duty and the recording element. This process is completed.

  Thereafter, when recording an actual image, in the density unevenness correction process J0010, the input image data CMYK is corrected in accordance with the signal values of the input image data and the correction parameters stored in association with the individual recording elements. Output as image data C′M′Y′K ′. More specifically, the recording duty closest to the input image data is selected from the three stages of recording duty, and correction processing is performed based on the correction parameter corresponding to the recording duty and the position of the recording element. According to the present embodiment, correction processing can be performed with an appropriate correction amount corresponding to the recording duty, and correction processing without density unevenness can be performed in all gradations.

  In the embodiment described above, the correction parameter is the correction value itself for adding or subtracting the CMYK multivalued data, but the present invention is not limited to such a form. The correction parameter of the present invention may be a parameter for indicating a function or a table in which the output signal value is associated with the input signal value on a one-to-one basis in the density unevenness correction process J0010.

  In the above embodiment, the density unevenness correction process J0010 is provided between the post-stage process J0003 and the γ correction process J0004, and multi-value density data is converted into multi-value density data. It is not limited to such a form. For example, when each recording element in the recording head can adjust the amount of ink ejected in a plurality of stages, the correction parameter may be a parameter indicating the ejection amount. In this case, the binarization process J0005 is a multi-value quantization process corresponding to the number of stages of the ejection amount, and the correction parameter can be corrected for the output result of the multi-value quantization process.

  Furthermore, the parameters generated in the correction parameter generation step described above can be provided independently according to various conditions such as the type of recording medium, the recording mode, or the usage environment. In this case, the correction parameters are stored and managed for each condition such as the type of ink color and the type of recording medium.

  The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

11-14 Recording head 60a-60c Real image
82 Scanner (reading means)
100 Host device
104 Inkjet recording apparatus
704 Standard distribution
705 Density unevenness distribution
706 Correction value distribution J0007 Color separation process J0008 Density unevenness data acquisition process J0009 Correction parameter generation process J0010 Density unevenness correction process

Claims (15)

A correction data generation method for recording an image using a recording head in which a plurality of recording elements for recording a color material of a predetermined color is arranged,
A first acquisition step of acquiring first density data corresponding to each of the plurality of recording elements based on image data for recording an actual image on a recording medium;
A second acquisition step of acquiring second density data corresponding to each of the plurality of recording elements based on read data obtained by reading the actual image recorded on the recording medium by a reading unit; ,
Density unevenness data acquisition step of acquiring density unevenness data corresponding to each of the plurality of recording elements based on the first density data and the second density data;
And a generation step of generating correction data corresponding to each of the plurality of recording elements for reducing density unevenness in the plurality of recording elements based on the density unevenness data. . The first acquisition step acquires the first density data by extracting a color component corresponding to the predetermined color from the image data,
The said 2nd acquisition process acquires the said 2nd density data by extracting the color component corresponding to the said predetermined color from the result read by the said reading means, The said 2nd density data is acquired. Correction data generation method. The first acquisition step acquires the first density data corresponding to each of the plurality of recording elements based on image data corresponding to each of a plurality of different regions in the real image,
The second acquisition step acquires the second density data corresponding to each of the plurality of recording elements based on read data corresponding to each of the plurality of regions,
In the generating step, for each of the plurality of regions, the plurality of recording elements are adjusted so that the density recorded by each of the plurality of recording elements matches the average value of density unevenness data corresponding to the plurality of recording elements. The correction data generation method according to claim 1, wherein the corresponding correction data is generated.   4. The correction data is not generated for a recording element corresponding to the missing portion when a missing portion exists between the plurality of regions in the direction in which the plurality of recording elements are arranged. The correction data generation method described.   When there is an overlap area between the plurality of areas in the direction in which the plurality of recording elements are arranged, for the recording element corresponding to the overlap area, the correction data corresponding to each of the plurality of areas 5. The correction data generation method according to claim 3, wherein new correction data common to the plurality of regions is generated on the basis of the method.   Based on the difference between the correction data corresponding to each of the plurality of areas in the overlap area and the new correction data, the correction data corresponding to a recording element corresponding to an area other than the overlap area is further included. 6. The correction data generation method according to claim 5, wherein the correction data is corrected.   When there is an overlap area between the plurality of areas in the direction in which the plurality of recording elements are arranged, the density unevenness corresponding to each of the plurality of areas is determined for the recording elements corresponding to the overlap area. 5. The correction data generation method according to claim 3, wherein new density unevenness data common to the plurality of regions is generated based on the data.   Based on the difference between the density unevenness data corresponding to each of the plurality of areas in the overlap area and the new density unevenness data, the density unevenness corresponding to a recording element corresponding to an area other than the overlap area. The correction data generation method according to claim 7, wherein the data is further corrected.   In the first acquisition step, first image data corresponding to each of the plurality of recording elements is extracted by extracting image data having a close density value from image data corresponding to each of a plurality of different regions in the actual image. The correction data generation method according to claim 3, wherein density data of the correction data is acquired. The first acquisition step corresponds to each of the plurality of recording elements by extracting a plurality of combinations of image data having similar density values from image data corresponding to each of a plurality of different regions in the actual image. A plurality of first density data to be acquired,
The second acquisition step acquires a plurality of second density data corresponding to each of the plurality of recording elements based on read data corresponding to the image data extracted by the first acquisition step,
The density unevenness data acquisition step acquires a plurality of density unevenness data based on the plurality of first density data and the plurality of second density data,
The correction data generation method according to claim 1, wherein the generation step generates a plurality of correction data for each of the plurality of regions based on the plurality of density unevenness data.   The correction data generation method according to claim 1, further comprising a step of correcting image data for recording an actual image based on the correction data.   The correction data generation method according to claim 1, wherein the color material is ink, and the recording head is an ink jet recording head that discharges ink from the recording element.   The recording head is a full-line type recording head configured by arranging the plurality of recording elements by a distance corresponding to the width of the recording medium in a direction intersecting a conveyance direction of the recording medium. The correction data generation method according to any one of claims 1 to 12.   A program for causing a computer to execute the correction data generation method according to any one of claims 1 to 13. A data processing apparatus for generating correction data for recording an image using a recording head in which a plurality of recording elements for recording a color material of a predetermined color are arranged,
First acquisition means for acquiring first density data corresponding to each of the plurality of recording elements based on image data for recording an actual image on a recording medium;
Second acquisition means for acquiring second density data corresponding to each of the plurality of recording elements based on read data obtained by reading the actual image recorded on the recording medium by a reading means; ,
Density unevenness data acquisition means for acquiring density unevenness data corresponding to each of the plurality of recording elements based on the first density data and the second density data;
A data processing apparatus comprising: generating means for generating correction data corresponding to each of the plurality of recording elements for reducing density unevenness in the plurality of recording elements based on the density unevenness data.

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