Density unevenness correction data creation method, density unevenness correction data creation device, printing system, program, test chart and test chart data creation device

Abstract

To provide a density unevenness correction data creation method, a density unevenness correction data creation device, a printing system, a program, a test chart, and a test chart data creation device, which achieve highly accurate density unevenness correction.SOLUTION: A density unevenness correction data creation method acquires a photographic image of a test chart including a density step pattern, an alignment mark and a line mark, acquires rough correspondence using positional information of the alignment mark when acquiring correspondence information between a theoretical position and an imaging position from the photographic image, acquires detailed correspondence using positional information of the line mark estimated using the rough correspondence, and estimates a density value for each density step pattern position using the detailed correspondence and creates density unevenness correction data.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a density unevenness correction data creating method, a density unevenness correction data creating device, a printing system, a program, a test chart, and a test chart data creating device. [Background technology]

[0002] Patent Document 1 describes a method for correcting density unevenness in an inkjet printing device. The device described in this document prints a test pattern including a color density pattern having a pattern corresponding to a plurality of density values, scans the test pattern to obtain a scanned image of the test pattern, and creates density unevenness correction data based on the scanned image of the test pattern. The density unevenness correction data is applied to printing when producing a printed matter.

[0003] In the creation of density unevenness correction data described in the document, the scanned image of the test pattern is subjected to image deformation processing in advance and then used, thereby improving the accuracy of density unevenness correction.

[0004] Figure 5 of the document illustrates a test pattern including a color density pattern and alignment marks, with multiple alignment marks arranged on the periphery of the color density pattern. The multiple alignment marks are used to detect the position of the test pattern, the printing resolution, the inclination of the image, etc. The multiple alignment marks each have a different shape, making them easy to distinguish from one another.

[0005] The image deformation process applied to creating density unevenness correction data detects the central coordinates of the alignment mark portion from the scanned image of the test pattern, calculates deformation parameters that represent the relationship between the theoretical coordinates in a plane Cartesian coordinate system and the detected actual coordinates for multiple alignment mark portions, and performs two-dimensional deformation processing on the color density pattern portion using the deformation parameters.

[0006] In the device described in Patent Document 1, when the medium to be printed is wide and the entire width of the medium cannot be scanned at once by performing a single scan, multiple scan images with different scan positions in the width of the medium are acquired, and the multiple scan images are synthesized to obtain a scan image of the entire width of the medium. In this case, scanning is performed so that the alignment marks are shared in the divided parts of the medium for each scan, and the synthesis position between the multiple scan images is grasped. The multiple scan images are synthesized based on the position information of the shared alignment mark part. The term alignment mark refers to the alignment mark itself that is printed on the medium and visually recognized. The term alignment mark part refers to a signal that represents the alignment mark in the scanned image. In this specification, the term image may be used to mean image data and an electrical signal that represent an image.

[0007] Patent Document 2 describes an inkjet type droplet ejection device. FIG. 3 of the document illustrates a test pattern used for detecting density unevenness. The test pattern includes three density patterns, a first mark indicating the division position of the recording head, a second mark serving as a reference when calculating the position of each ejection nozzle, and an angle detection mark used for detecting angle errors when printing and reading the test pattern. The device described in the document detects density unevenness and calculates a correction value for each ejection nozzle that requires correction of density unevenness. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6897992 [Patent Document 2] JP 2010-36452 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, the device described in Patent Document 1 has the following problems.

[0010] [Problem 1] The deformation accuracy of the color density pattern depends on the detection accuracy of the central coordinate of the alignment mark portion. If the deformation accuracy of the color density pattern is low, it may cause a shift in the correction position of the density unevenness correction, and the correction accuracy of the density unevenness correction may decrease due to the shift in the correction position.

[0011] For example, when single-pass printing is performed using a line head that corresponds to the page width, the detection accuracy of the center coordinates of the alignment mark portion in the first direction, which is the nozzle row direction of the line head, is particularly likely to affect the correction accuracy of density unevenness correction. In addition, the following problems can be raised in relation to the detection accuracy of the center coordinates of the alignment mark portion.

[0012] [Problem 1-A] For printing devices with a relatively high print resolution, such as 1200 dots per inch, scanners that can apply a scan resolution equal to or higher than the print resolution are expensive and are difficult to adopt as test pattern scanning devices. In many cases, the scan resolution of the test pattern must be relatively low compared to the print resolution of the test pattern. However, if the reading resolution of the test pattern is relatively low compared to the print resolution of the test pattern, the detection accuracy of the center coordinates of the alignment mark portion is likely to decrease.

[0013] [Problem 1-B] Since the alignment marks are different in shape, the detection accuracy of the center coordinates varies depending on the shape of each alignment mark portion, making it difficult to control the deformation accuracy.

[0014] [Problem 1-C] If dirt adheres to the printed alignment mark, or if printing defects such as streaks occur due to poor nozzle ejection, either a decrease in the detection rate of the alignment mark portion or a decrease in the detection accuracy of the center coordinates of the alignment mark portion, or both, may occur.

[0015] [Problem 1-D] It is difficult to improve both the detection rate of the alignment mark portion and the detection accuracy of the center coordinate of the alignment mark portion. For example, if additional processing such as filtering is performed on the scanned image of the alignment mark with the intention of improving the detection rate of the alignment mark portion, the detection accuracy of the center coordinate of the alignment mark portion may decrease.

[0016] [Problem 2] The process of two-dimensionally transforming the scanned image of the alignment mark imposes a relatively heavy computational load, which may result in inconveniences such as increased consumption of resources applied to the computational process and time-consuming computational process.

[0017] [Problem 3] The amount of ink ejected varies depending on the pattern portions for each density that constitutes the color density pattern. When the medium used for printing shrinks due to ink absorption, the shrinkage of the medium differs for each density pattern.

[0018] On the medium, the amount of ink ejected differs between the portion where the alignment mark is printed and the portion where the color density pattern is printed, and when the color density pattern portion is deformed two-dimensionally using deformation parameters calculated based on a scanned image of the alignment mark, the accuracy of the deformation process decreases, which can result in a decrease in the accuracy of detection of the center coordinates of the alignment mark portion.

[0019] The amount of shrinkage of a medium depends on the type of medium. For example, a relatively thin medium is more likely to shrink than a relatively thick medium. Also, paper is more likely to shrink than metal.

[0020] The amount of shrinkage of the medium also depends on the scanning position of the scanned image. For example, consider a case where an ink droplet ejection step, a first position scanning step, a drying step, and a second position scanning step are performed in that order. The drying step is likely to accelerate shrinkage of the medium, and the shrinkage rate of the medium in the second position scanning step is likely to be greater than the amount of shrinkage of the medium in the first position scanning step. Furthermore, the device described in Patent Document 2 has the following problems.

[0021] [Problem 4] Neither the first mark nor the second mark has a unique shape, and it is difficult to specify the absolute position based on the first mark and the second mark. That is, each of the multiple mark portions reflected in the scanned image of the test pattern has the same shape, and it is difficult to specify which mark portion represents which position. Note that the multiple marks are a collective term for the components of the first mark and the components of the second mark.

[0022] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a density unevenness correction data creation method, a density unevenness correction data creation device, a printing system, a program, a test chart, and a test chart data creation device that solves at least any of the above-mentioned problems and realizes high-precision density unevenness correction. [Means for solving the problem]

[0023] A density unevenness correction data creation method according to a first aspect is a density unevenness correction data creation method for creating density unevenness correction data applicable to single-pass printing using a line head in which a plurality of recording elements are arranged along a first direction, the method including a test chart photographing image acquisition step of acquiring a test chart photographed image obtained by photographing a first test chart that includes a density step pattern including one or more density patterns corresponding to one or more density values, a plurality of alignment marks having mutually different shapes, and a plurality of line marks having a shape extending in a second direction perpendicular to the first direction and that is printed on a printing medium; a correspondence relationship information acquisition step of acquiring correspondence relationship information representing a correspondence relationship between a theoretical position in the first test chart and a photographing position in the test chart photographed image for the first direction and the second direction; and a density unevenness correction data creating step of creating density unevenness correction data using density information of a density step pattern in the photographed image, wherein the correspondence information acquiring step acquires a rough correspondence indicating the correspondence between a theoretical position in the first direction and a photographed position using information on the position of each alignment mark in the first direction specified based on the shape of each alignment mark, and acquires a detailed correspondence between a theoretical position in the first direction and a photographed position using information on the positions of each of a plurality of line marks estimated using the acquired rough correspondence relationship, which indicates a more detailed correspondence than the rough correspondence relationship, and the density unevenness correction data creating step estimates a density value for each position in the first direction of the density step pattern using the detailed correspondence relationship for the first direction to create density unevenness correction data.

[0024] According to the density unevenness correction data generating method of the first aspect, alignment marks are detected from the captured image of the first test chart, and the detection result of the alignment marks is used to obtain a rough correspondence relationship between the theoretical positions and the captured positions.

[0025] The center position of the line mark is estimated using the rough correspondence relationship, and a detailed correspondence relationship between the theoretical position and the photographing position is obtained. For a first direction corresponding to the arrangement direction of the recording elements of the line head, the density value of each recording element in the first direction is grasped using the detailed correspondence relationship, and density unevenness correction data is created based on the density value of each recording element in the first direction.

[0026] As a result, density unevenness correction data that can perform density unevenness correction with high accuracy is created.

[0027] A line head is a type of print head in which a plurality of recording elements are arranged over a length corresponding to the overall length of the print medium in the first direction.

[0028] The single pass method is a printing method in which the print medium and the print head are moved relative to each other only once to print over the entire printable area of ​​the print medium.

[0029] An example of the printing method is an inkjet method that employs an inkjet head that is provided with a plurality of nozzles and ejects ink from the plurality of nozzles.

[0030] A density unevenness correction data creation method according to a second aspect is the density unevenness correction data creation method according to the first aspect, wherein the density unevenness correction data creation process includes an alignment mark detection process for detecting a plurality of alignment marks from a captured test chart image, and the alignment mark detection process may include a detection improvement processing process for applying a detection improvement process to the captured test chart image to improve the probability of detecting the alignment marks.

[0031] According to this aspect, the probability of detecting the alignment mark can be improved.

[0032] A density unevenness correction data creation method according to a third aspect may be the density unevenness correction data creation method according to the second aspect, in which the correspondence information acquisition process acquires detailed correspondence in the first direction for a test chart captured image that has not been subjected to detection improvement processing.

[0033] According to this aspect, the accuracy of detecting the alignment mark can be improved.

[0034] A density unevenness correction data creation method according to a fourth aspect is the density unevenness correction data creation method according to the second or third aspect, and the detection improvement processing step may determine a luminance contrast enhancement amount for the test chart captured image from luminance information of alignment marks not subjected to the detection improvement processing, and perform contrast enhancement processing on the test chart captured image using the determined luminance contrast enhancement amount.

[0035] According to this aspect, an appropriate emphasis process is applied to the alignment mark, which can improve the probability of detecting the alignment mark.

[0036] A density unevenness correction data creation method according to a fifth aspect is a density unevenness correction data creation method according to any one of the second to fourth aspects, in which the detection improvement processing step applies at least one of blurring filter processing, median filter processing, and morphological processing to the test chart captured image.

[0037] According to this aspect, the probability of detecting the alignment mark can be improved.

[0038] A density unevenness correction data creating method according to a sixth aspect is the density unevenness correction data creating method according to any one of the first to fifth aspects, wherein the plurality of line marks may have the same shape.

[0039] According to this aspect, the probability of detecting the line marks can be improved.

[0040] A density unevenness correction data creation method according to a seventh aspect is a density unevenness correction data creation method according to any one of the first to sixth aspects, wherein the correspondence information acquisition process acquires the correspondence in the second direction based on information on the positions of a plurality of alignment marks in the second direction.

[0041] According to this aspect, it is possible to acquire a correspondence relationship in the second direction according to the accuracy of the alignment marks.

[0042] A density unevenness correction data creation method according to an eighth aspect is a density unevenness correction data creation method according to any one of the first to seventh aspects, in which the correspondence information acquisition process, when creating the detailed correspondence in the first direction, may apply image processing to the line marks in the captured image of the test chart to estimate the positions of the line marks in the first direction.

[0043] According to this aspect, the accuracy of estimating the line marks can be improved.

[0044] A density unevenness correction data creation method according to a ninth aspect is the density unevenness correction data creation method of the eighth aspect, wherein the line mark position estimation process may be such that, for the estimated positions of a plurality of line marks, any line mark whose difference between the position of each line mark estimated using the rough correspondence relationship and the position of each line mark estimated using the detailed correspondence relationship exceeds a specified range is excluded from the line marks used to obtain the detailed correspondence relationship.

[0045] According to this aspect, the accuracy of estimating the line marks can be improved.

[0046] A density unevenness correction data creation method according to a tenth aspect is a density unevenness correction data creation method according to any one of the first to ninth aspects, wherein the density unevenness correction data creation process may use the correspondence relationship to determine at least one theoretical position for each recording element for each density pattern included in the density step pattern from the test chart photographed image, and may estimate the density for each density pattern for each recording element by averaging or accumulating the test chart photographed image within the range of the density pattern in the second direction for the theoretical position for each recording element determined from the test chart photographed image.

[0047] According to this aspect, the accuracy of the density estimation for each recording element can be improved.

[0048] A density unevenness correction data creation method according to an eleventh aspect, in the density unevenness correction data creation method according to any one of the first to tenth aspects, includes a mode switching process for selectively switching between a first mode in which density unevenness correction data is created based on a captured image of a first test chart, and a second mode which is performed separately from the first mode, in which density unevenness correction data is created based on a second test chart in which a line pattern extending in a second direction is superimposed on a density step pattern included in the first test chart, and in the second mode, for the captured test chart image of the second test chart, a position of the line pattern in the first direction is estimated, information on the estimated position of the line pattern in the first direction is used to obtain a detailed correspondence relationship in the first direction, and the detailed correspondence relationship for the first direction is used to estimate a density value for each position in the first direction of the density step pattern, thereby creating density unevenness correction data.

[0049] According to this aspect, highly accurate density unevenness correction data is generated according to the expansion and contraction characteristics of the printing medium, thereby implementing density unevenness correction that suppresses the effects of the expansion and contraction characteristics of the printing medium.

[0050] A density unevenness correction data creation method according to a 12th aspect may be the density unevenness correction data creation method of the 11th aspect, in which, in a second mode, a deviation in the correspondence between the first sequence and the second sequence is corrected by utilizing common information common to a first sequence for generating density unevenness correction data to be applied to the first mode and a second sequence for generating density unevenness correction data to be applied to the second mode.

[0051] According to this aspect, it is possible to avoid a discrepancy between the density unevenness correction data generated in the first mode and the density unevenness correction data generated in the second mode.

[0052] A density unevenness correction data creating method according to a thirteenth aspect is the density unevenness correction data creating method of the twelfth aspect, wherein the common information may include information on an edge of the density pattern in the first direction.

[0053] According to this aspect, the deviation in the correspondence relationship between the first sequence and the second sequence is corrected with high accuracy.

[0054] A density unevenness correction data creating method according to a fourteenth aspect is the density unevenness correction data creating method of the twelfth aspect, wherein the common information may include information on positions of the plurality of line marks in the first direction.

[0055] According to this aspect, the deviation in the correspondence relationship between the first sequence and the second sequence is corrected with high accuracy.

[0056] A density unevenness correction data creation method according to a 15th aspect may be a density unevenness correction data creation method according to any one of the 12th to 14th aspects, and when the test chart shooting image is generated using multiple image sensors, may include an overlap area correction process for correcting a deviation in the correspondence between the first sequence and the second sequence in the first direction by using information of line marks included in an overlap area where the shooting areas of the image sensors overlap.

[0057] According to this aspect, the deviation in the correspondence relationship between the first sequence and the second sequence caused by the overlapping region is corrected with high accuracy.

[0058] A density unevenness correction data creation method according to a 16th aspect is the density unevenness correction data creation method of the 15th aspect, in which the overlap area correction process may correct a deviation in the correspondence between the first sequence and the second sequence using information obtained by statistically processing the positions of a plurality of line marks arranged in the overlap area.

[0059] According to this aspect, the deviation in the correspondence relationship between the first sequence and the second sequence caused by the overlapping region is corrected with high accuracy.

[0060] A density unevenness correction data creation device according to a seventeenth aspect is a density unevenness correction data creation device that creates density unevenness correction data applicable to single-pass printing using a line head in which a plurality of recording elements are arranged along a first direction, and includes one or more processors and one or more memories that store programs to be executed by the one or more processors, and the one or more processors execute instructions of the programs to obtain a test chart captured image obtained by photographing a first test chart that includes a density step pattern including one or more density patterns corresponding to one or more density values, a plurality of alignment marks having mutually different shapes, and a plurality of line marks having a shape extending in a second direction perpendicular to the first direction, and that is printed on a printing medium, and compares theoretical positions in the first test chart with the test chart captured image in the first direction and the second direction. and creates density unevenness correction data using density information of the density step pattern in the captured image of the test chart. When acquiring the correspondence information, a coarse correspondence indicating the correspondence between the theoretical position in the first direction and the shooting position is acquired using information on the position of each alignment mark in the first direction specified based on the shape of each alignment mark, and a detailed correspondence between the theoretical position in the first direction and the shooting position is acquired using information on the positions of each of a plurality of line marks estimated using the acquired coarse correspondence, which indicates a more detailed correspondence than the coarse correspondence. When creating the density unevenness correction data, the detailed correspondence for the first direction is used to estimate a density value for each position in the first direction of the density step pattern, to create the density unevenness correction data.

[0061] The density unevenness correction data creating device according to the 17th aspect can provide the same advantageous effects as the density unevenness correction data creating method according to the 1st aspect. The constituent elements of the density unevenness correction data creating methods according to the 2nd to 16th aspects can be applied to the constituent elements of the density unevenness correction data creating device according to the other aspects.

[0062] A printing system according to an eighteenth aspect includes a line head in which a plurality of recording elements are arranged along a first direction, and a density unevenness correction data creation device that creates density unevenness correction data to be applied to single-pass printing in which the line head is used. The density unevenness correction data creation device includes one or more processors and one or more memories in which a program to be executed by the one or more processors is stored. The one or more processors execute instructions of the program to obtain a test chart photographed image obtained by photographing a first test chart that includes a density step pattern including one or more density patterns corresponding to one or more density values, a plurality of alignment marks having shapes different from each other, and a plurality of line marks having a shape extending in a second direction perpendicular to the first direction, and that is printed on a printing medium, and the density unevenness correction data creation device calculates a density unevenness correction data corresponding to a theoretical position in the first test chart in the first direction and a theoretical position in the second direction. A printing system which acquires correspondence information indicating the correspondence with the shooting position in the captured image of the test chart, and creates density unevenness correction data using density information of the density step pattern in the captured image of the test chart; when acquiring the correspondence information, acquires a coarse correspondence indicating the correspondence between the theoretical position in the first direction and the shooting position using information on the position of each alignment mark in a first direction specified based on the shape of each alignment mark, and acquires a detailed correspondence between the theoretical position in the first direction and the shooting position, which indicates a more detailed correspondence than the coarse correspondence, using information on the positions of each of a plurality of line marks estimated using the acquired coarse correspondence; and when creating the density unevenness correction data, estimates the density value for each position in the first direction of the density step pattern using the detailed correspondence for the first direction, to create the density unevenness correction data.

[0063] The printing system according to the 18th aspect can achieve the same effects as the density unevenness correction data creation method according to the 1st aspect. The constituent elements of the density unevenness correction data creation methods according to the 2nd to 16th aspects can be applied to the constituent elements of the printing systems according to the other aspects.

[0064] A program according to a 19th aspect is a program for creating density unevenness correction data to be applied to single-pass printing using a line head in which a plurality of recording elements are arranged along a first direction, the program comprising: a computer acquiring a test chart photographed image obtained by photographing a first test chart that includes a density step pattern including one or more density patterns corresponding to one or more density values, a plurality of alignment marks having mutually different shapes, and a plurality of line marks having a shape extending in a second direction perpendicular to the first direction and that is printed on a printing medium; acquiring correspondence relationship information that indicates a correspondence relationship between theoretical positions in the first test chart and photographing positions in the test chart photographed image for the first and second directions; a density step pattern in a first direction to obtain a density unevenness correction data; and when obtaining the correspondence information, a coarse correspondence indicating the correspondence between the theoretical position in the first direction and the shooting position is obtained using information on the position of each alignment mark in the first direction specified based on the shape of each alignment mark, and a detailed correspondence between the theoretical position in the first direction and the shooting position is obtained using information on the position of each of a plurality of line marks estimated using the obtained coarse correspondence relationship, which indicates a more detailed correspondence than the coarse correspondence relationship. When obtaining the density unevenness correction data, the detailed correspondence relationship for the first direction is used to estimate a density value for each position in the first direction of the density step pattern, thereby obtaining the density unevenness correction data.

[0065] According to the program of the 19th aspect, it is possible to obtain the same effect as the density unevenness correction data creating method of the 1st aspect. The constituent elements of the density unevenness correction data creating method of the 2nd to 16th aspects can be applied to the constituent elements of the program of the other aspects.

[0066] The test chart according to the 20th aspect is a test chart used when creating density unevenness correction data to be applied to single-pass printing using a line head in which multiple recording elements are arranged along a first direction, and includes a density step pattern including one or more density patterns corresponding to one or more density values, multiple alignment marks having mutually different shapes, and multiple line marks having a shape extending in a second direction perpendicular to the first direction.

[0067] According to the test chart of the 20th aspect, it is possible to create density unevenness correction data that realizes highly accurate density unevenness correction as density unevenness correction data used for density unevenness correction performed in single-pass printing using a line head.

[0068] The constituent elements of the density unevenness correction data generating methods according to the second to sixteenth aspects can be applied to the constituent elements of the test charts according to the other aspects.

[0069] A test chart according to a twenty-first aspect is the test chart of the twentieth aspect, wherein the plurality of line marks may have the same shape.

[0070] A test chart according to a twenty-second aspect may include an abnormal recording element detection pattern used when detecting an abnormality in a recording element in the test chart of the twentieth or twenty-first aspect.

[0071] A test chart according to a 23rd aspect is the test chart according to the 22nd aspect, wherein the abnormal recording element detection pattern is a plurality of lines recorded using each of a plurality of recording elements, and may include a plurality of lines extending in a second direction and having different positions in a first direction for each recording element.

[0072] A test chart data creation device according to a 24th aspect is a test chart data creation device that creates test chart data representing a test chart used to create density unevenness correction data applied to single-pass printing using a line head in which multiple recording elements are arranged along a first direction, the test chart being a test chart that includes a density step pattern including one or more density patterns corresponding to one or more density values, multiple alignment marks having different shapes, and multiple line marks having a shape extending in a second direction perpendicular to the first direction, and the test chart data creation device is equipped with a graphical user interface that is used when adjusting at least one of the alignment mark parameters applied to the alignment marks and the line mark parameters applied to the line marks.

[0073] A test chart data creation device according to a 25th aspect is the test chart data creation device of the 24th aspect, wherein the graphical user interface may be used to adjust at least any of the size of the alignment marks, the aspect ratio of the alignment marks, the density of the alignment marks, the number of alignment marks, and the spacing between adjacent alignment marks.

[0074] A test chart data creation device according to a 26th aspect is a test chart data creation device according to the 24th or 25th aspect, in which the graphical user interface may be used to adjust at least any of the size of the line marks, the aspect ratio of the line marks, the density of the line marks, the number of line marks, and the spacing between adjacent line marks.

[0075] A test chart data creation device according to a 27th aspect is a test chart data creation device according to any one of the 24th to 26th aspects, in which the line marks include low density portions having a relatively low density value and high density portions having a high density value relative to the low density portions, and the graphical user interface may be used to adjust at least one of the density of the low density portions, the length of the low density portions in a first direction, the density of the high density portions, and the length of the high density portions in the first direction. Effect of the Invention

[0076] According to the present invention, alignment marks are detected from a captured image of a first test chart, and a rough correspondence relationship between theoretical positions and captured positions is obtained using the detection result of the alignment marks. The center position of the line mark is estimated using the rough correspondence relationship, and a detailed correspondence relationship between the theoretical positions and captured positions is obtained. For a first direction corresponding to the arrangement direction of the recording elements of the line head, the density value of each recording element in the first direction is grasped using the detailed correspondence relationship, and density unevenness correction data is created based on the density value of each recording element in the first direction. This creates density unevenness correction data that can perform high-precision density unevenness correction. [Brief description of the drawings]

[0077] [Figure 1] FIG. 1 is a flowchart showing the procedure of a density unevenness correction data generating method according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram of a test chart. [Diagram 3] FIG. 3 is a diagram showing a specific example of the alignment marks and line marks shown in FIG. [Figure 4] FIG. 4 is a schematic diagram showing an example of the line mark adjustment screen. [Diagram 5] FIG. 5 is a schematic diagram showing a modified example of the test chart shown in FIG. [Figure 6] FIG. 6 is a flowchart showing the procedure of the density unevenness correction data update processing step shown in FIG. [Figure 7]FIG. 7 is a block diagram illustrating an example of an electrical configuration and hardware configuration of the density unevenness correction data generating device according to the first embodiment. [Figure 8] FIG. 8 is a functional block diagram showing an electrical configuration of the density unevenness correction data generating device shown in FIG. [Figure 9] FIG. 9 is a block diagram showing an example of a hardware configuration of an electrical configuration of a density unevenness correction data generating device according to a modified example. [Figure 10] FIG. 10 is a functional block diagram showing the electrical configuration of the density unevenness correction data generating device shown in FIG. [Figure 11] FIG. 11 is a flowchart showing the procedure of the alignment mark portion detection process. [Figure 12] FIG. 12 is a flow chart showing an outline of a density unevenness correction data generation sequence. [Figure 13] FIG. 13 is a flowchart showing a procedure when a correspondence relationship acquisition sequence is introduced separately from a density unevenness correction sequence. [Figure 14] FIG. 14 is a schematic diagram of a test chart applied to the correspondence relationship acquisition sequence shown in FIG. [Figure 15] FIG. 15 is a flow chart showing the procedure of a density unevenness correction data generating method in the case where a plurality of modes are provided. [Figure 16] FIG. 16 is a schematic diagram of a test chart according to a modified example. [Figure 17] FIG. 17 is a diagram showing the overall configuration of an inkjet printing system according to an embodiment. [Figure 18] FIG. 18 is a perspective view showing an example of the configuration of the ink-jet head shown in FIG. [Figure 19] FIG. 19 is a plan view showing an example of the nozzle arrangement of the ink-jet head shown in FIG. [Figure 20] FIG. 20 is a functional block diagram showing the electrical configuration of the inkjet printing system shown in FIG. [Figure 21] FIG. 21 is a block diagram illustrating an example of a hardware configuration of the electrical configuration shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification, the same components are given the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0079] [First embodiment] [Outline of density unevenness correction data creation method] Fig. 1 is a flowchart showing the procedure of a density unevenness correction data creating method according to the first embodiment. An example of the density unevenness correction data creating method is shown below, in which each step is performed using a density unevenness correction data creating device provided in a printing system. A computer equipped with a processor is applied as the density unevenness correction data creating device. An example is shown in which an inkjet printing device is applied as the printing system.

[0080] The density unevenness correction to which the density unevenness correction data is applied is a process for suppressing density unevenness in a printed image caused by variations in the ejection performance of a plurality of nozzles provided in an inkjet head, and is performed using density unevenness correction data that is created and stored in advance. Note that the plurality of nozzles described in the embodiment is an example of a plurality of recording elements.

[0081] The density unevenness correction data generating method shown in FIG. 1 includes a density unevenness correction data obtaining step S10, a test chart printing step S12, a scanned image generating step S14, and a density unevenness correction data updating step S16.

[0082] [Density unevenness correction data acquisition process] In the density unevenness correction data acquisition process S10, pre-stored current density unevenness correction data is acquired. Density unevenness correction can be performed repeatedly in a feedback manner. When the first density unevenness correction is performed, the current density unevenness correction data becomes initial data in an uncorrected state. The initial data may be acquired by reading an initial data file prepared in advance, or the initial data may be created within the software. Once the density unevenness correction data is acquired in the density unevenness correction data acquisition process S10, the process proceeds to a test chart printing process S12.

[0083] [Test chart printing process] In the test chart printing step S12, the current density unevenness correction data acquired in the density unevenness correction data acquisition step S10 is applied to create print data information for the test chart in a state in which the density unevenness correction process has been performed.

[0084] In the test chart printing step S12, ink is ejected from the inkjet head onto the print medium using the print data of the created test chart, and the test chart is printed on the print surface of the print medium. If the first density unevenness correction is performed, the density unevenness correction process may be omitted. If the density unevenness correction process is omitted, the density unevenness correction data acquisition step S10 in the previous step may be omitted.

[0085] The test chart printed in the test chart printing step S12 includes a density step pattern having a plurality of patterns corresponding to a plurality of density values. The details of the test chart will be described later. After the test chart is printed in the test chart printing step S12, the process proceeds to the scan image creation step S14.

[0086] [Scanned image creation process] In the scan image creation step S14, the printed test chart is photographed by an image sensor system equipped with an image sensor, and a scan image of the test chart is created. Note that the image sensor may be called an image sensor. An example of the image sensor system is a scanner device.

[0087] When the test chart is photographed, it is preferable to perform shading correction due to the performance of the image sensor system, such as unevenness in the amount of illumination light due to the light amount distribution of the illumination light and unevenness in reading due to the reading characteristic distribution of the image sensor.

[0088] The shading characteristics of the image sensor system can be acquired in advance by reading the white reference plate and the non-printed portion of the medium using the image sensor. The non-printed portion here may include the concept of a region.

[0089] For example, a non-printed portion may be provided on at least one of the upper side, the lower side, and the inside of the test chart on the print medium, and the shading characteristics may be acquired by utilizing the non-printed portion reflected in the scanned image of the test chart read at the timing when the density unevenness correction is performed. When the shading characteristics are acquired in this manner, even if the shading characteristics change over time, appropriate shading characteristics can be acquired when the density unevenness correction is performed. When the scanned image of the test chart is created in the scanned image creation step S14, the process proceeds to the density unevenness correction data update processing step S16. Note that the scanned image creation step described in the embodiment is an example of a test chart photographed image acquisition step.

[0090] [Density unevenness correction data update processing process] The density unevenness correction data update process S16 includes an analysis process of analyzing the scanned image of the test chart, a creation process of creating the latest density unevenness correction data using the analysis result of the scanned image, and a storage process of storing the latest density unevenness correction data. The printing system performs density unevenness correction processing on the print data of the print image using the latest density unevenness correction data, and performs printing.

[0091] [Example of test chart] [Configuration overview] FIG. 2 is a schematic diagram of a test chart. In the figure, a test chart TC1 printed on a printing medium is shown. The first direction shown in the figure is a direction corresponding to the direction in which a plurality of nozzles provided in the inkjet head are arranged. The second direction is a direction perpendicular to the first direction. The first and second directions are directions defined by the printing surface of the printing medium and are parallel to the printing surface of the printing medium.

[0092] When the nozzles of the inkjet head are arranged two-dimensionally, the above-mentioned direction in which the nozzles are arranged is the direction in which the nozzles are substantially arranged. In the case of a line head, the direction parallel to the width direction of the printing medium, which is perpendicular to the transport direction of the printing medium, is the direction in which the nozzles are substantially arranged.

[0093] In the test chart TC1 shown in FIG. 2, a plurality of alignment marks AM and a plurality of line marks LM are arranged on the outer periphery of the density step pattern SP, and the alignment marks AM and the line marks LM are arranged alternately in the first direction.

[0094] 2 illustrates an example of the outer periphery of the density step pattern SP, which is one outer side and the other outer side of the density step pattern SP in the second direction. In the figure, a test chart TC1 in which the number of alignment marks AM and the number of line marks LM are the same is illustrated, but the number of alignment marks AM and the number of line marks LM may be different.

[0095] [Alignment mark details] The alignment marks AM are used to estimate a rough position on the printing medium. Each of the alignment marks AM has a unique shape, making it possible to identify which alignment mark AM it is.

[0096] In Fig. 2, the difference in shape of each of the alignment marks AM is illustrated using a character string of different alphabets added to the word "marker." An example of a specific shape of the alignment marks AM is illustrated in Fig. 3.

[0097] [Line marking details] The line marks LM are used to estimate a detailed printing position in a first direction. The line direction in which the line marks LM extend is a second direction perpendicular to the first direction. The line marks LM are preferably simple solid lines, but any line that can generally be recognized as a line will do. For example, dotted lines and dashed lines may also be included in the concept of a line.

[0098] Each of the multiple line marks LM has a central line portion LMC to which a relatively low density value is applied at the central position in the first direction, and has peripheral line portions LMP to which relatively high density values ​​are applied on both sides of the central line portion LMC in the first direction. The central line portion LMC shown in Fig. 2 is applied with a minimum density value, and the peripheral line portion LMP is applied with a maximum density value. Regarding the densities of the central line portion LMC and the peripheral line portion LMP, it is sufficient that there is a contrast between the central line portion LMC and the peripheral line portion LMP, and the central line portion LMC may be applied with a density value exceeding the minimum density value, and the peripheral line portion LMP may be applied with a density value less than the maximum density value.

[0099] The central line portion LMC of each line mark LM is formed at the central position of each line mark LM in the first direction. The central position in the first direction of the central line portion LMC having a specified length in the first direction is specified as the central position of the central line portion LMC of each line mark LM. The position of the central line portion LMC of each line mark LM may be any position as long as the central line portion LMC can be recognized, and the central line portion LMC does not have to be the central position of each line mark LM in the first direction.

[0100] The relationship between the density value of the central line portion LMC and the density value of the peripheral line portion LMP in the line mark LM may be such that the density value of the central line portion LMC is greater than the density value of the peripheral line portion LMP, or the density value of the central line portion LMC is less than the density value of the peripheral line portion LMP. Of the central line portion LMC and the peripheral line portion LMP, the one to which the lower density value is applied may be applied with a density value of 0, and for example, no ink droplets may be ejected. It is preferable that the shapes of each of the multiple line marks LM are common.

[0101] 2 illustrates a plurality of line marks LM having the same shape. Examples of line marks LM that have a common shape rather than the same shape include a case where the size of the central line portion LMC is different, a case where the density value of the central line portion LMC is different, a case where the size of the peripheral line portion LMP is different, and a case where the density value of the peripheral line portion LMP is different.

[0102] [Contents of density step pattern] The density step pattern SP has a plurality of density patterns CP extending in a first direction. The same density value is applied to each density pattern CP. The plurality of density patterns CP are arranged along the second direction in ascending or descending order of density value. Figure 2 illustrates an example of a density step pattern SP in which the density value of the density pattern CP increases from one end to the other end in the second direction.

[0103] 2 illustrates an example of a density step pattern SP to which eight density values ​​are applied, but the number of density values ​​may be two or more, including a density value of zero, and density values ​​other than zero may be one or more. The minimum density value of the density step pattern SP may be the density value of the central line portion LMC of the line mark LM. The maximum density value of the density step pattern SP may be the density value of the peripheral line portion LMP of the line mark LM.

[0104] [Scan configuration] The image sensor IS scans the test chart TC1 printed on the print medium to create a scanned image of the test chart TC1. Hereinafter, the term "scanned image" may be read as a "scanned image of the test chart."

[0105] The image sensor IS may be a line sensor having a structure in which sensor elements are arranged in a line, or a two-dimensional sensor having a structure in which sensor elements are arranged two-dimensionally. A line sensor is advantageous in terms of cost.

[0106] In wide-width printing using a line head, it may not be possible to scan the entire width of the print medium using one image sensor IS. In the case of wide-width printing, multiple image sensors are provided, and each of the multiple image sensors is assigned to scan a different area, so that the multiple image sensors can be used to obtain a scanned image of the entire width of the print medium.

[0107] When multiple image sensors IS are used, the scan areas in the first direction are partially overlapped between adjacent image sensors IS in the first direction. Figure 2 illustrates a case where the scan overlap areas shown by arrows are set for two image sensors IS.

[0108] [Alignment mark size] In general, the detection rate of the alignment mark AM is improved as the size of the alignment mark AM is relatively larger. The detection rate of the alignment mark AM is the ratio of the number of alignment marks AM correctly detected to the number of attempts to detect the alignment mark AM.

[0109] When printing the test chart TC1 using a combination of ink and medium that easily bleeds, or when printing with many defects such as streaks, if the size of the alignment mark AM is relatively small, there is a concern that there will be a lack of information expressing the characteristics of the alignment mark AM. On the other hand, if the size of the alignment mark AM is relatively too large, there may be disadvantages such as the test chart TC1 becoming large. Therefore, it is preferable that the size of the alignment mark is freely adjustable using parameters, and the size of the alignment mark is adjusted according to the printing device and printing conditions. Details of the adjustment of the alignment mark will be described later.

[0110] [Aspect ratio of alignment marks] The detection process of the alignment mark AM is performed on the alignment mark portion of the scanned image. Therefore, it is preferable that the aspect ratio of the alignment mark AM is an appropriate aspect ratio in the alignment mark portion of the scanned image. For example, in the case where the aspect ratio of the alignment mark AM is preferable to be 1:1 for the detection process of the alignment mark AM, if the aspect ratio of the printing resolution and the aspect ratio of the scanning resolution are different, it is necessary to configure a test chart TC1 in which the aspect ratio of the alignment mark portion of the scanned image is 1:1.

[0111] For example, when the printing resolution is 1200×1200 dots per inch and the scanning resolution is 100×600 dots per inch, the aspect ratio of the alignment marks AM formed as the test chart TC1 is preferably 6:1.

[0112] When the aspect ratio of the alignment mark AM is defined as above, the aspect ratio of the alignment mark portion of the scanned image is 1:1. The print resolution and scan resolution are expressed in the format of resolution in the second direction x resolution in the first direction. The test chart TC1 shown in FIG. 2 is an example of the first test chart.

[0113] [Specific examples of alignment marks and line marks] Fig. 3 is a diagram showing a specific example of the alignment mark and line mark shown in Fig. 2. The alignment mark AM shown in Fig. 3 has a pattern shape conforming to the ArUco marker. That is, when the first direction is the horizontal direction and the second direction is the vertical direction, the alignment mark AM is an ArUco marker having an aspect ratio of 1:1 that is elongated six times in the second direction, resulting in an aspect ratio of 6:1.

[0114] 3 has the same aspect ratio as the alignment mark AM, ie, 6 to 1. The line mark LM shown in the figure has a ratio of 1 to 12 between the central line portion LMC and the peripheral line portion LMP in the first direction.

[0115] When the ratio of the peripheral line portion LMP to the central line portion LMC in the first direction is relatively large and the central line portion LMC is relatively thin, the positional accuracy of the central line portion LMC improves but recognition of the central line portion LMC may become difficult. On the other hand, when the ratio of the peripheral line portion LMP to the central line portion LMC in the first direction is relatively small and the central line portion LMC is relatively thick, recognition of the central line portion LMC becomes easy but the positional accuracy of the central line portion LMC may decrease.

[0116] It is preferable to provide a user interface that allows adjustment of the ratio between the central line portion LMC and the peripheral line portion LMP in the first direction of the line mark LM. For example, an adjustment screen for the line mark LM is displayed on a display device, and an operator operates input devices such as a keyboard and a mouse to set various conditions for the line mark LM.

[0117] 4 is a schematic diagram showing an example of a line mark adjustment screen. A line mark adjustment screen 1000 shown in the figure displays a line mark display area 1002 in which a line mark LM is enlarged and displayed. The line mark display area 1002 displays a scale 1004 below the line mark LM. The scale 1004 may be freely switched between display and non-display in response to a user input or the like.

[0118] The line mark adjustment screen 1000 displays a center density setting section 1010 for setting the density of the central line portion LMC and a peripheral density setting section 1012 for setting the density of the peripheral line portion LMP. The center density setting section 1010 includes a center density input section 1014 for inputting the density of the central line portion LMC. The center density input section 1014 may input the density of the central line portion LMC by applying a pull-down menu. The center density input section 1014 may also apply a format for inputting a numerical value representing a density value.

[0119] The peripheral density setting section 1012 includes a peripheral density input section 1016 for inputting the density of the peripheral line portion LMP. The peripheral density input section 1016 may be configured similarly to the central density input section 1014.

[0120] The line mark adjustment screen 1000 displays an aspect ratio setting section 1020 for setting the aspect ratio of the line mark LM. The aspect ratio setting section 1020 includes an aspect ratio input section 1021 for inputting the aspect ratio of the line mark LM. The aspect ratio input section 1021 may apply a format for inputting a numerical value representing the aspect ratio of the line mark LM. The numerical value applied to the aspect ratio may be an integer or may be a numerical value having a decimal part.

[0121] The line mark adjustment screen 1000 displays a center width setting section 1022 for setting the width of the center line portion LMC. The center width setting section 1022 includes a center width input section 1023 for inputting the width of the center line portion LMC. The center width input section 1023 may apply a format for inputting a numerical value representing the width of the center line portion LMC. The width of the center line portion LMC is the length of the center line portion LMC in the first direction. The center width setting section 1022 may set the width of the center line portion LMC in units of one pixel.

[0122] The line mark adjustment screen 1000 displays a peripheral width setting section 1024 for setting the width of the peripheral line part LMP. The peripheral width setting section 1024 includes a peripheral width input section 1025 for inputting the width of the peripheral line part LMP. The peripheral width input section 1025 may apply a format for inputting a numerical value representing the width of the peripheral line part LMP. The width of the peripheral line part LMP is the length of the peripheral line part LMP in the first direction.

[0123] The width of the peripheral line portion LMP may be the length in the first direction of either of the two peripheral line portions LMP sandwiching the central line portion LMC. The widths of the two peripheral line portions LMP sandwiching the central line portion LMC may be the same or different. When the widths of the two peripheral line portions LMP sandwiching the central line portion LMC are different, the width may be set for each of the two peripheral line portions LMP. The peripheral width setting unit 1024 may set the width of the peripheral line portion LMP in units of one pixel.

[0124] A line mark number setting section 1026 for setting the number of line marks LM is displayed on the line mark adjustment screen 1000. The line mark number setting section 1026 includes a line mark number input section 1027 for inputting the number of line marks LM. The line mark number input section 1027 may adopt a format for inputting a numerical value representing the number of line marks LM.

[0125] The line mark adjustment screen 1000 displays an interval setting section 1028 for setting the interval between the line marks LM. The interval setting section 1028 includes an interval input section 1029 for inputting the interval between the line marks LM. The interval input section 1029 may adopt a format for inputting a numerical value representing the interval between the line marks LM. The interval setting section 1028 may set the interval between the line marks LM in units of one pixel.

[0126] The interval between the line marks LM is the distance between two line marks LM adjacent to each other in the first direction. The distance between the two line marks LM may be the distance between the centers of the two line marks LM.

[0127] A set button 1030 for finalizing settings such as the aspect ratio of the line mark LM and a cancel button 1032 for canceling the settings are displayed on the line mark adjustment screen 1000. When the set button 1030 is operated, the settings are finalized, and when the cancel button 1032 is operated, the settings are cancelled.

[0128] Although not shown in the figures, a configuration is also possible in which the aspect ratio, etc., of the alignment mark AM shown in Fig. 3 can be adjusted. An alignment mark adjustment screen similar to the line mark adjustment screen 1000 shown in Fig. 4 is displayed on a display device, and the operator operates input devices such as a keyboard and a mouse to set various conditions of the alignment mark AM.

[0129] The line mark adjustment screen 1000 shown in FIG. 4 can function as a graphical user interface provided in a test chart data creating device that creates test chart data representing the test chart TC1 shown in FIG.

[0130] A graphical user interface provided in the test chart creation device can adjust at least one of the parameters of the alignment mark AM and the parameters of the line marker LM.

[0131] Examples of parameters of the alignment mark AM include the size of the alignment mark, the aspect ratio of the alignment mark, the density of the alignment mark, the number of alignment marks, and the spacing between adjacent alignment marks.

[0132] Examples of the parameters of the line marks LM include the size of the line marks, the aspect ratio of the line marks, the density of the line marks, the number of line marks, and the interval between adjacent line marks.

[0133] Other examples of the parameters of the line marker LM include the density of the central line portion LMC, the width of the central line portion LMC, the density of the peripheral line portion LMP, and the width of the peripheral line portion LMP.

[0134] The test chart data creation device is a computer. The test chart data creation device includes one or more processors and one or more memories, and the one or more processors execute instructions of a program stored in the one or more memories to realize various functions of the test chart data creation device.

[0135] The parameters of the alignment mark AM described in the embodiment are an example of alignment mark parameters. The parameters of the line mark LM described in the embodiment are an example of line mark parameters. The central line portion LMC described in the embodiment is an example of a low density portion having a relatively low density value. The peripheral line portion LMP described in the embodiment is an example of a high density portion having a high density value relative to the low density portion. The width of the central line portion LMC described in the embodiment is an example of the length of the low density portion in the first direction. The width of the peripheral line portion LMP described in the embodiment is an example of the length of the high density portion in the first direction.

[0136] [Modifications of the Test Chart] Due to the configuration of the inkjet head, the concentration distribution in the first direction at any first position in the second direction may vary due to the influence of the concentration distribution in the second direction at a second position different from the first position.

[0137] In particular, when the physical arrangement of multiple nozzle openings in an inkjet head is distributed two-dimensionally and multiple different nozzle openings are connected to the same common flow path, the above-mentioned phenomenon, known as crosstalk, is likely to occur.

[0138] When the crosstalk phenomenon occurs, there is a concern that the density distribution of the alignment mark AM, etc. may affect the density distribution of the portion of the density step pattern SP adjacent to the alignment mark AM, etc., causing pseudo density unevenness, and the pseudo density unevenness may be overcorrected. Therefore, it is preferable to physically separate the alignment mark AM, etc. and the density step pattern SP by a certain distance in the second direction.

[0139] Fig. 5 is a schematic diagram showing a modified example of the test chart shown in Fig. 2. In the test chart TC2 shown in the figure, a non-pattern portion NP is provided between the alignment mark AM and the line mark LM and the density step pattern SP in the second direction. In Fig. 5, the non-pattern portion NP is illustrated using a two-dot chain line.

[0140] 5 is defined to have a length in the second direction sufficient to ignore the effects of crosstalk. The length of the non-patterned portion NP in the second direction depends on the configuration of the inkjet head in which the nozzles are arranged two-dimensionally.

[0141] For example, during a period when a certain nozzle group is printing a density pattern CP, another nozzle group may be printing alignment marks AM and line marks LM. In such a case, if the nozzle group that prints the density pattern CP and the nozzle group that prints the alignment marks AM etc. are supplied with ink from the same flow path inside the inkjet head, the printing of the density pattern CP may be affected by the printing of the alignment marks AM etc. Similarly, the printing of the alignment marks AM etc. may be affected by the printing of the density pattern CP.

[0142] Since the alignment marks AM and line marks LM are not uniform patterns, even though the printing of the density pattern CP is an originally uniform pattern, it is possible that the printing will be correlated with the printing of the alignment marks AM, etc. This phenomenon is called crosstalk.

[0143] If density correction is performed using the density pattern CP in a state in which crosstalk occurs during printing of the density pattern CP, the non-uniform patterns of the density pattern CP may be recognized as unevenness, resulting in overcorrection.

[0144] When printing the density pattern CP, it is preferable that the alignment marks AM and the like are printed in a uniform pattern at least in the first direction, which is the direction in which the unevenness correction characteristics are obtained, and as a method for this, a non-pattern portion NP having sufficient length in the second direction is provided.

[0145] A density pattern CP similar to an adjacent density pattern CP may be arranged in the non-pattern portion NP. For example, a density pattern CP to which the same density value as that of an adjacent density pattern CP is applied may be arranged in the non-pattern portion NP.

[0146] The test chart TC2 shown in FIG. 5 is also effective in improving the robustness against flare of the lens provided in the image sensor IS shown in FIG. 2. The length of the non-patterned portion NP in the second direction may be appropriately specified depending on the conditions of the inkjet head and the combination of the printing medium and the ink. A user interface for adjusting the length of the non-patterned portion NP in the second direction may be provided. The test chart TC2 shown in FIG. 5 is an example of the first test chart.

[0147] [Details on creating density unevenness correction data] Fig. 6 is a flowchart showing the procedure of the density unevenness correction data update processing step shown in Fig. 1. The density unevenness correction data update processing step includes an alignment mark portion detection step S20, a line mark portion center position estimation step S22, a density data estimation step S24, and a density unevenness correction data creation step S26.

[0148] [Alignment mark portion detection process] In the alignment mark portion detection process S20, image processing is performed on the scanned image to detect the alignment mark portion from the scanned image. The multiple alignment marks AM each have a unique shape, and by using information on the detected alignment mark portion, correspondence information that indicates the correspondence between the theoretical position and the scan position can be acquired. The correspondence information can include a correspondence in a first direction and a correspondence in a second direction. Note that the scan position described in the embodiment is an example of a shooting position. The process of acquiring the correspondence information using the detection information of the alignment mark portion described in the embodiment is an example of a correspondence information acquisition process. Hereinafter, the acquisition of the correspondence information may be described as the acquisition of the correspondence.

[0149] Here, obtaining the correspondence information may include the concept of deriving the correspondence using information on the theoretical position and information on the scanning position, such as a mode of calculating the correspondence and a mode of estimating the correspondence. Also, the correspondence between the theoretical position and the scanning position may be obtained for any coordinate from the information on the correspondence between the theoretical position and the scanning position. This may solve the above-mentioned problem 4.

[0150] The theoretical position is a general term for the theoretical position of the alignment mark AM on the test chart TC1 and the theoretical position of the line mark LM on the test chart TC1. Hereinafter, the theoretical position of the alignment mark AM on the test chart TC1 and the theoretical position of the line mark LM on the test chart TC1 may be distinguished and referred to as the theoretical position of the alignment mark AM.

[0151] The scan position is a general term for the actual position of the alignment mark portion in the scanned image and the actual position of the line mark portion in the scanned image. The actual position of the alignment mark portion in the scanned image and the actual position of the line mark portion in the scanned image may be distinguished and referred to as the scan position of the scan line mark portion.

[0152] The correspondence relationship between the theoretical position and the scan position can be understood as the correspondence relationship between the theoretical position of the alignment mark AM and the scan position of the alignment mark portion, or the correspondence relationship between the theoretical position of the line mark LM and the scan position of the line mark portion. The correspondence relationship between the theoretical position of the alignment mark AM and the scan position of the alignment mark portion can be understood as a rough correspondence relationship. The correspondence relationship between the theoretical position of the line mark LM and the scan position of the line mark portion can be understood as a detailed correspondence relationship. The rough correspondence relationship described in the embodiment is an example of a rough correspondence relationship, and the detailed correspondence relationship is an example of a detailed correspondence relationship.

[0153] In the alignment mark portion detection process S20, when the correspondence relationship between the theoretical position and the scan position is acquired for the first direction and the second direction, a line mark portion center position estimation process S22 is executed. Note that the alignment mark portion detection process S20 described in the embodiment is an example of an alignment mark detection process.

[0154] [Number of alignment marks that need to be detected] In a two-dimensional coordinate system in which the X and Y directions are defined, in order to obtain a rough correspondence relationship, an amount of information that allows two linearly independent vectors to be defined is required. That is, for one image sensor IS, it is necessary to detect three or more alignment marks AM with different directions. On the other hand, more alignment marks AM may be detected, and when a large number of alignment marks AM are detected, the correspondence relationship can be obtained in a least squares manner from the positions of each alignment mark AM. In addition, the correspondence relationship can be obtained in a piecewise complementary manner from the positions of each alignment mark AM. When a large number of alignment marks AM are detected, the accuracy of the correspondence relationship can be improved. Note that the position of each alignment mark AM described in the embodiment is an example of the position of each alignment mark.

[0155] [Definition of alignment mark reference position] To obtain a rough correspondence, it is necessary to determine which position of one alignment mark AM should be used as the reference. As an example, the center position of the alignment mark AM in the top, bottom, left, and right directions can be used as the reference position. The center positions of the top, bottom, left, and right directions can be understood as two directions that are mutually perpendicular.

[0156] As another example, one of the corners of the alignment mark AM can be set as the reference position. An example of a corner is a vertex of a rectangle when the outline of the alignment mark AM is a rectangle. In this way, the reference position can be defined in various ways.

[0157] [Getting scan mark position] The theoretical position can be calculated theoretically, but the scan position needs to be estimated from the scan image. The scan image is a scan luminance image obtained by scanning a test chart TC1 using the image sensor IS shown in Figure 2.

[0158] When the reference position of the alignment mark AM is the central position in the top, bottom, left and right directions, for example, the center position of the alignment mark part can be obtained in the scanned image, and the reference position of the alignment mark part can be estimated from the center position of the alignment mark part. Alternatively, image processing such as edge detection processing can be performed to estimate multiple edges and multiple corners of the alignment mark part, and then the midpoint of the multiple edges or the midpoint of the multiple corners can be obtained, and the reference position of the alignment mark part can be estimated from the midpoint of the multiple edges, etc.

[0159] [Precision of correspondence] The estimation accuracy of the scanning position affects the accuracy of the correspondence. For example, when the scanning position is estimated at the resolution level of the image sensor IS, the accuracy of the correspondence is equal to or lower than the resolution level of the image sensor IS. If the density unevenness correction data is created based on the rough correspondence obtained using the alignment mark AM, there is a concern that the accuracy of the density unevenness correction data may be insufficient, as described in the above problems 1-A to 1-D. On the other hand, in the density unevenness correction data creation method according to this embodiment, the correspondence in the first direction, which requires high accuracy, is obtained using the detailed correspondence obtained using the line mark LM.

[0160] [Line mark center position estimation process] In the line mark portion center position estimating step S22, the center position of the line mark portion in the scanned image is estimated using the rough correspondence relationship acquired in the alignment mark portion detection step S20. Note that the line mark portion center position estimating step S22 described in the embodiment is an example of a line mark position estimating step.

[0161] Specifically, since a rough correspondence is acquired in the alignment mark portion detection process S20, the approximate positions of the line mark portions can be specified without detecting the line mark portions individually from the scanned image. The approximate positions of the line mark portions are the positions of the line mark portions at the resolution level of the image sensor IS. Therefore, the line marks LM may all have the same shape.

[0162] The processing performed on the line mark portion of the scanned image is to estimate the position of the line mark portion in a first direction with high accuracy and obtain a detailed correspondence between the theoretical position and the scanned position in the first direction. The theoretical position can be expressed by applying coordinates defined on the medium. The scanned position is estimated from the theoretical position using the correspondence between the theoretical position and the scanned position.

[0163] The estimation accuracy of the center position of the line mark portion needs to be higher than the estimation accuracy of the position of the alignment mark portion. The estimation accuracy of the center position of the line mark portion needs to be able to be estimated with a higher resolution than the resolution of the scanned image. Various methods are conceivable for estimating the high resolution, but the following procedure can be applied as a method for estimating the high resolution. <1> The line mark portion of the scanned image is subjected to averaging or integration processing in the second direction to convert it into one-dimensional data. <2> A blurring filter process is performed on the one-dimensional data using a blurring filter. <3> The positions of the luminance peaks in the blurred data are determined. The positions of the luminance peaks are calculated with the accuracy of the scan resolution level. <4> Using the brightness gradient information of the peak position and the positions before and after the peak position, the peak position is estimated in detail at the sub-pixel level.

[0164] [Number of line marks] Since the greater the number of line marks LM, the greater the accuracy of the detailed correspondence relationship, so basically the greater the number of line marks LM is the better. It is preferable that the number of line marks LM and the interval between the line marks LM in the first direction can be freely set, and that the interval between the line marks LM in the first direction can be appropriately set. As an example of a user interface for setting the number of line marks, etc., a line mark adjustment screen 1000 is illustrated in FIG. 4.

[0165] [Center line width] It is preferable to configure the width of the central line portion LMC in the line mark LM to be freely set, and to be able to set the width of the central line portion LMC in the line mark LM as appropriate. For example, in a combination of a printing medium and ink in which bleeding is relatively large, if the width of the central line portion LMC is made relatively small, there is a concern that the central line portion LMC will disappear due to bleeding of the ink. By setting the width of the central line portion LMC as appropriate, it is possible to avoid the disappearance of the central line portion LMC, etc.

[0166] [Concentration data estimation process] In the density data estimation step S24, a detailed correspondence is used for the first direction and a rough correspondence is used for the second direction, and a density value for each nozzle is estimated from each density pattern CP of the density step pattern SP. The density value for each nozzle corresponds to the density value for each position in the first direction.

[0167] Specifically, for each density pattern CP, the theoretical position in the first direction of one point for each nozzle is obtained from the scan position. For the obtained theoretical position in the first direction, the scanned image is averaged or calculated for each density within the area of ​​the density pattern CP in the second direction to estimate the density value for each density pattern CP of each nozzle.

[0168] [Processing without image deformation] In the device described in Patent Document 1, the scanned image of the test pattern is deformed two-dimensionally. As described in Problem 2 above, image deformation can cause problems such as consumption of computational resources and increased computation time. Therefore, in the density unevenness correction data creation method according to this embodiment, as described above, the density value for each density pattern CP of each nozzle is estimated. This realizes low computational resources and high-speed computation. Note that the density value for each density pattern CP described in the embodiment is an example of the density value for each density pattern.

[0169] [Density unevenness correction data creation process] In the density unevenness correction data creation process S26, an input gradation value that flattens the density distribution in the first direction is calculated for each nozzle from the characteristic data that indicates the relationship between the input gradation value and the output density for each nozzle, and density unevenness correction data is created. The created density unevenness correction data is stored as the latest density unevenness correction data.

[0170] [Example of configuration of density unevenness correction data generating device according to the first embodiment] 7 is a block diagram showing an example of an electrical configuration and hardware configuration of the density unevenness correction data generating device according to the first embodiment. The density unevenness correction data generating device is applied with a computer having one or more processors and one or more memories. The computer may be in the form of a server, a personal computer, a workstation, a tablet terminal, or the like.

[0171] The density unevenness correction data generating device 100 includes a processor 102, a computer-readable medium 104 which is a non-transitory tangible object, a communication interface 106, and an input / output interface 108.

[0172] The processor 102 includes a central processing unit (CPU). The processor 102 may include a graphics processing unit (GPU). The processor 102 is connected to a computer-readable medium 104, a communication interface 106, and an input / output interface 108 via a bus 110. An input device 120 and a display device 122 are connected to the bus 110 via the input / output interface 108.

[0173] The computer-readable medium 104 includes a memory 112 which is a primary storage device and a storage 114 which is a secondary storage device. The computer-readable medium 104 may be a semiconductor memory, a hard disk drive, a solid-state drive, or the like. The computer-readable medium 104 may be any combination of multiple devices.

[0174] A hard disk device may be referred to as an HDD, which is an abbreviation of the English term Hard Disk Drive, and a solid state drive device may be referred to as an SSD, which is an abbreviation of the English term Solid State Drive.

[0175] The density unevenness correction data generating device 100 is connected to a network via a communication interface 106, and is communicably connected to an external device. The network may be a local area network (LAN) or the like. The network is not shown in the figure.

[0176] The computer-readable medium 104 stores a density unevenness correction data update program 130. The density unevenness correction data update program 130 includes an alignment mark portion detection program 132, a line mark portion center estimation program 134, a density data estimation program 136, and a density unevenness correction data creation program 138.

[0177] 6, the density unevenness correction data update program 130 realizes a function of creating and updating density unevenness correction data. The updated latest density unevenness correction data 150 is stored in the storage 114. The density unevenness correction data before the update may be stored separately from the latest density unevenness correction data 150 by adding identification information.

[0178] The alignment mark portion detection program 132 is applied to the alignment mark portion detection step S20 shown in Fig. 6. The line mark portion center estimation program 134 is applied to the line mark portion center position estimation step S22. The density data estimation program 136 is applied to the density data estimation step S24. The density unevenness correction data creation program 138 is applied to the density unevenness correction data creation step S26.

[0179] Various programs stored in the computer-readable medium 104 include one or more instructions. The computer-readable medium 104 stores various data, various parameters, and the like.

[0180] In the density unevenness correction data generating device 100, the processor 102 executes various programs stored in a computer-readable medium 104 to realize various functions of the density unevenness correction data generating device 100. Note that the term "program" is synonymous with the term "software."

[0181] The density unevenness correction data generating device 100 performs data communication with an external device via a communication interface 106. The communication interface 106 may be compliant with various standards such as USB (Universal Serial Bus). The communication form of the communication interface 106 may be either wired communication or wireless communication.

[0182] An input device 120 and a display device 122 are connected to the density unevenness correction data creating device 100 via an input / output interface 108. The input device 120 is implemented by input devices such as a keyboard and a mouse. The display device 122 displays various information applied to the density unevenness correction data creating device 100. For example, the display device 122 can display a line mark adjustment screen 1000 shown in FIG.

[0183] A liquid crystal display, an organic EL display, a projector, etc. may be used as the display device 122. Any combination of a plurality of devices may be used as the display device 122. Note that the EL in the organic EL display is an abbreviation for Electro-Luminescence.

[0184] Here, examples of the hardware structure of the processor 102 include a CPU, a GPU, a PLD (Programmable Logic Device), and an ASIC (Application Specific Integrated Circuit). The CPU is a general-purpose processor that executes programs and acts as various functional units. The GPU is a processor specialized for image processing.

[0185] A PLD is a processor whose electrical circuitry can be reconfigured after the device is manufactured. An example of a PLD is the Field Programmable Gate Array (FPGA). An ASIC is a processor that contains dedicated electrical circuitry designed specifically to perform a specific task.

[0186] A processing unit may be composed of one of these various processors, or may be composed of two or more processors of the same or different types. Examples of combinations of various processors include a combination of one or more FPGAs and one or more CPUs, and a combination of one or more FPGAs and one or more GPUs. Another example of a combination of various processors includes a combination of one or more CPUs and one or more GPUs.

[0187] A single processor may be used to configure multiple functional units. An example of using a single processor to configure multiple functional units is a configuration in which a single processor is configured by applying a combination of one or more CPUs and software, such as a SoC (System On a Chip) as typified by a computer such as a client or server, and the processor is made to operate as multiple functional units.

[0188] Another example of using one processor to configure multiple functional units is a processor that uses one IC chip to realize the functions of the entire system including the multiple functional units. Note that IC is an abbreviation for Integrated Circuit.

[0189] In this way, the various functional units are configured as a hardware structure using one or more of the various processors described above. More specifically, the hardware structure of the various processors described above is an electric circuit (circuitry) that combines circuit elements such as semiconductor elements.

[0190] The computer-readable medium 104 may include semiconductor elements such as a Read Only Memory (ROM), a Random Access Memory (RAM), and a Solid State Drive (SSD). The computer-readable medium 104 may include a magnetic storage medium such as a hard disk. The computer-readable medium 104 may include multiple types of storage media.

[0191] Fig. 8 is a functional block diagram showing the electrical configuration of the density unevenness correction data generating device shown in Fig. 7. The density unevenness correction data generating device 100 includes a density unevenness correction data acquiring unit 200, a print data generating unit 202, and a scan image generating unit 204.

[0192] The density unevenness correction data acquisition unit 200 executes the density unevenness correction data acquisition step S10 shown in Fig. 1. The density unevenness correction data acquisition unit 200 acquires the latest density unevenness correction data from the density unevenness correction data storage unit 214.

[0193] 7, the latest density unevenness correction data acquired from the density unevenness correction data storage unit 214 is omitted. The latest density unevenness correction data is illustrated in FIG 6 as density unevenness correction data 150. In addition, the density unevenness correction data storage unit 214 illustrated in FIG 8 is included in the storage 114 illustrated in FIG 7.

[0194] The print data creation unit 202 executes the test chart printing step S12 using the printing device 180. The scan image creation unit 204 executes the scan image creation step S14 using the image sensor system 190.

[0195] The density unevenness correction data generating device 100 includes an alignment mark portion detection unit 206 , a line mark portion center estimation unit 208 , a density data estimation unit 210 , a density unevenness correction data generating unit 212 , and a density unevenness correction data storage unit 214 .

[0196] The alignment mark portion detection unit 206 executes the alignment mark portion detection program 132 shown in Fig. 7 to carry out the processing of the alignment mark portion detection step S20 shown in Fig. 6. The line mark portion center estimation unit 208 executes the line mark portion center estimation program 134 to carry out the processing of the line mark portion center position estimation step S22.

[0197] The density data estimation unit 210 executes the density data estimation program 136 to perform the process of the density data estimation step S24. The density unevenness correction data creation unit 212 executes the density unevenness correction data creation program 138 to perform the process of the density unevenness correction data creation step S26. The density unevenness correction data creation unit 212 performs a process of storing the density unevenness correction data in the density unevenness correction data storage unit 214.

[0198] 8 may be provided in an external device of the density unevenness correction data creating device 100. An example of the external device of the density unevenness correction data creating device 100 is a control device of the printing device 180.

[0199] [Modification of Density Unevenness Correction Data Creation Apparatus] Fig. 9 is a block diagram showing an example of the electrical hardware configuration of a density unevenness correction data generating device according to a modified example. The density unevenness correction data generating device 100A shown in the figure is provided with a memory 112A instead of the memory 112 shown in Fig. 7. A density unevenness correction data updating program 130A stored in the memory 112A adds a detection improvement processing program 131 to the various programs shown in Fig. 7. The detection improvement processing program is executed in the alignment mark portion detection process S20 shown in Fig. 6.

[0200] Fig. 10 is a functional block diagram showing an electrical configuration of the density unevenness correction data generating device shown in Fig. 9. The density unevenness correction data generating device 100A shown in Fig. 10 is obtained by adding a detection improvement processing unit 205 to the density unevenness correction data generating device 100 shown in Fig. 8.

[0201] The detection improvement processing unit 205 executes the detection improvement processing program 131 to perform detection improvement processing on the alignment mark portion when detecting the alignment mark portion from the scanned image. A specific example of the detection improvement processing is shown below. Note that the process in which the detection improvement processing shown in the embodiment is performed is an example of a detection improvement processing process.

[0202] [First example of improved alignment mark detection rate due to pre-processing] For example, in single-pass printing, if a nozzle in an inkjet head has a discharge defect, streaks are likely to occur in the printed image, and streaks may also occur in the alignment mark AM. If a streak defect occurs in the alignment mark AM, the probability of failing to detect the alignment mark portion in the scanned image becomes relatively high.

[0203] Furthermore, if the scanned image is created with the print medium on which the test chart TC1 is printed having dirt or other contaminants attached thereto, the probability of failing to detect the alignment mark portion in the scanned image increases relatively. Therefore, before estimating the scan position, various pre-processing steps can be applied to improve the detection rate of the alignment mark portion in the scanned image.

[0204] Examples of various pre-processing processes include a filter process that applies a blurring filter to the scanned image in advance, a median filter process, and a morphological process. Examples of morphological processes include an opening process and a closing process. By performing various pre-processing processes, the influence of printing defects such as streak defects and attachments such as dust on the detection of the alignment mark portion in the scanned image can be reduced.

[0205] [Second example of improved detection rate of alignment marks due to pre-processing] The brightness contrast of the alignment mark portion in the scanned image is likely to affect the detection rate of the alignment mark portion. In general, when the brightness contrast is relatively low, the detection rate decreases. Therefore, the detection of the alignment mark portion is performed with the brightness contrast of the alignment mark portion emphasized. This can improve the detection rate of the alignment mark portion.

[0206] However, if the contrast enhancement process is applied too much, there is a risk that highlight blowout, black crush, etc. will occur in the alignment mark portion, resulting in a decrease in the detection rate. Therefore, it is preferable to grasp the brightness contrast of the alignment mark portion in advance and enhance the brightness contrast of the alignment mark portion within a range where highlight blowout, black crush, etc. will not occur.

[0207] On the other hand, it is difficult to grasp the brightness contrast of the alignment mark portion before the alignment mark portion is detected. To address this issue, the alignment mark portion detection process shown in the following procedure is effective.

[0208] 11 is a flow chart showing the procedure of the alignment mark portion detection process. The procedure of the alignment mark portion detection process shown in the figure can be understood as the procedure of an alignment mark portion detection method. The alignment mark portion detection process shown in the figure includes a first detection step S30 corresponding to alignment mark portion detection 1, a brightness contrast confirmation step S32, a brightness contrast enhancement step S34, and a second detection step S36 corresponding to alignment mark portion detection 2.

[0209] In the first detection process S30, the alignment mark portion is detected without contrast enhancement. In the first detection process S30, two or more alignment mark portions are detected. In the brightness contrast confirmation process S32, the brightness contrast of each of the alignment mark portions is confirmed from the brightness information of each of the two or more alignment mark portions detected in the first detection process S30. In the brightness contrast confirmation process S32, it is understood how much brightness contrast enhancement is required for the alignment mark portion.

[0210] In the luminance contrast emphasizing step S34, an appropriate range of luminance contrast enhancement amount is applied to the alignment mark portion according to the luminance contrast of the alignment mark portion confirmed in the luminance contrast checking step S32, thereby performing an enhancement process on the alignment mark portion.

[0211] In the second detection step S36, the alignment mark portion is detected from the scanned image in which the luminance contrast of the alignment mark portion has been enhanced in the luminance contrast enhancement step S34. In the second detection step S36, an improvement in the detection rate of the alignment mark portion is expected compared to the first detection step S30.

[0212] After the second detection step S36, the process may proceed to a brightness contrast confirmation step S32, and the brightness contrast confirmation step S32 and the brightness contrast enhancement step S34 may be performed to execute a second second detection step S36 in which the alignment mark portion is detected for the third time.

[0213] That is, after the second detection step S36, the brightness contrast confirmation step S32 and the brightness contrast enhancement step S34 may be executed to further optimize the degree of contrast enhancement that is optimal for detection of the alignment mark portion.

[0214] The second detection step S36, the luminance contrast confirmation step S32, and the luminance contrast enhancement step S34 may be repeated a number of times to optimize the luminance contrast enhancement of the alignment mark portion.

[0215] [Effect of alignment mark detection rate improvement processing on the estimation accuracy of scan mark position] Although the process for improving the detection rate of the alignment mark portion has the effect of improving the detection rate of the alignment mark portion, there is a risk of reducing the estimation accuracy of the position of the alignment mark portion in the scanned image due to the processing performed on the scanned image. However, in the method for creating density unevenness correction data according to the embodiment, the estimation accuracy of the position of the alignment mark portion is not so important, and even if the estimation accuracy of the position of the alignment mark portion is reduced, it does not become a problem for the overall processing.

[0216] [Disabling use of image sensors that do not detect alignment marks] Density unevenness correction may be performed on printing media of various sizes. When the size of the printing medium used for printing is relatively small and multiple image sensors IS are used, it is possible that only a specific image sensor IS scans the test chart TC1. In such a case, the alignment mark portion is not detected from the scan image of the image sensor IS other than the specific image sensor IS. Therefore, the scan image created using the image sensor IS in which the alignment mark portion is not detected from the scan image is excluded from the subsequent processing, and the subsequent processing is preferably performed using only the scan image created using the image sensor IS in which the alignment mark portion is detected.

[0217] [Processing of scanned images without pre-processing for detection of alignment mark portions] The pre-processing performed in the detection of the alignment mark portion may adversely affect the estimation of the center position of the line mark portion. Therefore, it is preferable to store a scan image on which the pre-processing in the detection of the alignment mark portion has not been performed, and estimate the center position of the line mark portion using the scan image on which the pre-processing has not been performed. Of course, pre-processing to improve the estimation accuracy of the center position of the line mark portion may be performed on the scan image on which the pre-processing has not been performed. The scan image on which the pre-processing described in the embodiment has not been performed is an example of a test chart image on which the detection improvement processing has not been performed.

[0218] [Removal of low-precision data] There is a risk that the estimated center positions of the line mark portions contain low-precision data due to some disturbance such as printing defects in the test chart and dust on the test chart. Therefore, it is possible to determine whether the data is low-precision by using a rough correspondence relationship obtained based on the alignment mark portions. The procedure for detecting low-precision data is shown below. <1> A coarse correspondence is applied to estimate the center position of each line mark portion. <2> The center position of the line mark portion estimated by applying the detailed correspondence relationship is compared with the center position of the line mark portion estimated by applying the coarse correspondence relationship. <3> When the difference between the central positions of the two types of line mark portions is relatively large, it is determined that the accuracy of the central position of the line mark portion estimated by applying the detailed correspondence relationship is low.

[0219] In general, the center position of the line mark portion estimated by applying a rough correspondence relationship is more robust against disturbances than the center position of the line mark portion estimated by applying a detailed correspondence relationship. Therefore, the process to which the above-mentioned procedure is applied can be performed to detect low-precision data and exclude the low-precision data from the process of determining the detailed correspondence relationship. Note that when the deviation between the center positions of the two types of line mark portions described in the embodiment is relatively large, this is an example of a line mark in which the difference in position for each line mark exceeds a specified range.

[0220] [Effects of the first embodiment] The method and device for creating data for correcting density unevenness according to the first embodiment can provide the following advantageous effects.

[0221] [1] An alignment mark portion corresponding to the alignment mark AM is detected from a scanned image of a test chart having the alignment mark AM and the line mark LM, and a rough correspondence relationship between the theoretical position and the scanned position is obtained using the detection result of the alignment mark portion.

[0222] The center position of the line mark portion is estimated using the rough correspondence relationship, and a detailed correspondence relationship between the theoretical position and the scan position is obtained. Density unevenness correction data is created using the detailed correspondence relationship for a first direction corresponding to the arrangement direction of the nozzles of the inkjet head.

[0223] This allows the printing system to perform highly accurate density unevenness correction using density unevenness correction data created using the detailed correspondence relationships.

[0224] [2] In the first direction, data of the center position of the line mark portion, which is obtained using a rough correspondence relationship and has low accuracy, is excluded from data used to obtain the detailed correspondence relationship. This improves the accuracy of the detailed correspondence relationship, and makes it possible to create density unevenness correction data using the detailed correspondence relationship with high accuracy.

[0225] [3] When detecting the alignment mark portion, a detection improvement process is performed on the scanned image, which can improve the robustness of the detection of the alignment mark portion.

[0226] [4] The density estimation for each nozzle is performed using the correspondence between the theoretical position and the scan position, and the density unevenness correction data is created using the density estimation value for each nozzle. This makes it possible to create the density unevenness correction data without performing image transformation processing that consumes a lot of calculation resources and takes a long processing time.

[0227] [Second embodiment] [How to cope with cases where the medium shrinkage is large at step concentration] 12 is a flowchart showing an outline of a sequence for generating density unevenness correction data. In the above description, the acquisition of the correspondence data 300 representing the correspondence between the theoretical position and the scanning position is performed in one density unevenness correction data generation sequence.

[0228] That is, in the density unevenness correction data generation sequence shown in FIG. 12, a correspondence acquisition process S40 is performed to acquire correspondence data 300 representing the correspondence between the theoretical position and the scanning position, and the next process, a density unevenness correction data creation process S42, is performed to create density unevenness correction data 302 using the correspondence data 300.

[0229] However, as shown in the above-mentioned problem 3, the correspondence between the theoretical position and the scan position may vary depending on the step density. In the second embodiment described below, a correspondence acquisition sequence is prepared in addition to the density unevenness correction data generation sequence. Note that the step density is the density value applied to each density pattern CP of the density step pattern SP. Note that the sequence shown in FIG. 12 is an example of the first sequence.

[0230] [Introduction of correspondence acquisition sequence] 13 is a flowchart showing the procedure when a correspondence acquisition sequence is introduced separately from the density unevenness correction sequence. As shown in the figure, in the correspondence acquisition sequence, a correspondence acquisition step S40 is executed, the correspondence data 300 is acquired, the correspondence data 300 is stored, and the process ends.

[0231] In the density unevenness correction data generating sequence, a density unevenness correction data creating step S42 is executed in advance using the correspondence relationship data 300 acquired in the correspondence relationship acquisition sequence, the density unevenness correction data 302 is created, the density unevenness correction data 302 is stored, and the process ends. The sequence shown in FIG. 13 is an example of the second sequence.

[0232] [Acquisition of correspondence in the first direction in the correspondence acquisition sequence] Fig. 14 is a schematic diagram of a test chart applied to the correspondence relationship acquisition sequence shown in Fig. 13. In the correspondence relationship acquisition sequence shown in Fig. 13, a test chart TC3 including a step line patch SLP shown in Fig. 14 is applied.

[0233] That is, the test chart TC3 shown in Fig. 14 includes a step line patch SLP instead of the density step pattern SP of the test chart TC1 shown in Fig. 1. In the step line patch SLP, a line pattern LP is inserted into the density step pattern SP shown in Fig. 1.

[0234] In the correspondence acquisition sequence shown in Fig. 13, detailed correspondence information in the first direction is acquired from information on the step line patch portion in the scanned image corresponding to the step line patch SLP shown in Fig. 14. The detailed correspondence information in the first direction is a correspondence between a theoretical position and a scanning position obtained at a similar density position in the unevenness correction data creation sequence, and by applying the detailed correspondence information in the first direction, the theoretical position can be calculated from the scanning position in the first direction in the density unevenness correction data creation sequence.

[0235] That is, when detailed information on the correspondence relationship in the first direction is obtained, information on the step line patch portion is used instead of information on the line mark portion, thereby solving the above-mentioned problem 3.

[0236] 14 shows an example of a line pattern LP to which a density value of zero is applied. The density of the line pattern LP may be any density that can distinguish each density pattern CP from the line pattern LP. A preferred embodiment includes a user interface for setting the density value of the line pattern LP.

[0237] [Line pattern width in step line patch] It is preferable that the width of the line pattern LP in the step line patch SLP is freely adjustable as appropriate according to the step density. The width of the line pattern LP extending in the first direction is the length of the line pattern LP in the second direction. For example, in a combination of an ink and a printing medium that are relatively prone to bleeding, if the width of the line pattern LP is relatively small, there is a concern that the line pattern LP will disappear due to bleeding. In addition, the degree of bleeding may vary according to the step density. Note that the test chart TC3 shown in FIG. 14 is an example of the second test chart.

[0238] [Correcting discrepancies between sequences] A correspondence relationship acquisition sequence is introduced separately from the density unevenness correction data creation sequence. The timing at which the density unevenness correction sequence is executed differs from the timing at which the correspondence relationship acquisition sequence is executed, and a deviation due to some conditional difference may occur. For example, between the density unevenness correction data creation sequence and the correspondence relationship acquisition sequence, the ambient environment such as the ambient temperature of the image sensor IS may change, causing a slight change in the resolution of the image sensor IS, resulting in a deviation between the scanned images.

[0239] Furthermore, between the density unevenness correction data creation sequence and the correspondence relationship acquisition sequence, the positional relationship between the inkjet head and the image sensor IS may mechanically change due to some factor, which may result in a deviation between the scanned images.

[0240] In order to improve robustness against such deviations, it is preferable to correct the deviation between the density unevenness correction sequence and the correspondence acquisition sequence. The deviation between the sequences can be corrected using image information common to each sequence. For example, the line mark LM shown in FIG. 14 is information common to each sequence. Therefore, in order to reduce the difference in position information of the line mark LM in each sequence, the detailed correspondence in the first direction acquired using the step line patch SLP is used after taking into account the enlargement processing information, reduction processing information, and translation processing information in the first direction. This can improve robustness against deviations between the sequences.

[0241] In addition, the edge in the first direction of the step line patch SLP is information common to each sequence. Therefore, in order to reduce the difference in position information of the edge in the first direction of the step line patch SLP in each sequence, detailed correspondence in the first direction acquired using the step line patch SLP is used after taking into account enlargement processing information, reduction processing information, and translation processing information in the first direction. This can improve robustness against misalignment between sequences.

[0242] [When multiple image sensors are used] When multiple image sensors IS are provided, the misalignment between the sequences becomes even more complicated. For example, between the density unevenness correction data creation sequence and the correspondence relationship acquisition sequence, the ambient environment, such as the ambient temperature, of at least one of the multiple image sensors IS may change slightly, causing a slight change in the resolution of the image sensor IS, resulting in a misalignment between the scanned images. This may cause the amount of overlap in the overlapping regions of the multiple image sensors IS to change.

[0243] When the overlap amount of the overlap area of ​​the multiple image sensors IS varies, it is effective to perform correction using information common to each sequence present in the overlap area. For example, one or more line marks LM are arranged in the overlap area, and the detailed correspondence in the first direction obtained using the step line patch SLP is used after further taking into account the change in the overlap amount between the sequences. This can improve robustness against misalignment between the sequences.

[0244] As many line marks LM as possible are arranged in the overlap region, and the change in the overlap amount is statistically obtained from the positions of the line marks LM. This makes it possible to obtain the change in the overlap amount with higher accuracy. Examples of statistical index values ​​include arithmetic mean values ​​and median values. Note that the process of acquiring a detailed correspondence relationship in the first direction using the step line patch SLP after further taking into account the change in the overlap amount described in the embodiment is an example of an overlap region correction process.

[0245] [Multiple modes available] A mode in which the density unevenness correction data creation sequence shown in Fig. 12 is used is referred to as a first mode, and a mode in which the density unevenness correction data creation sequence shown in Fig. 13 is used is referred to as a second mode. The first mode has the advantage that it is possible to easily create density unevenness correction data because the correspondence relationship acquisition step S40 is performed in the density unevenness correction data creation sequence, and there is no need to perform a separate correspondence relationship acquisition sequence. On the other hand, the first mode has the disadvantage that robustness against differences in paper deformation for each step density is relatively low.

[0246] The second mode has the advantage of being relatively robust against differences in paper deformation for each step density, but has the disadvantage that it is difficult to easily create density unevenness correction data because a correspondence relationship acquisition sequence must be performed in advance in addition to the density unevenness correction data creation sequence.

[0247] Therefore, when a density unevenness correction data generating function is incorporated into a printing system, it is preferable that the first and second modes are prepared and that the first and second modes can be selectively switched as required.

[0248] 15 is a flowchart showing the procedure of a method for creating density unevenness correction data when multiple modes are provided. In a mode information acquisition step S100, mode information for creating density unevenness correction data is acquired. In the mode information acquisition step S100, mode information input by an operator using the input device 120 shown in FIG. 7 can be acquired.

[0249] In the mode information acquisition step S100, mode information corresponding to printing conditions such as the type of printing paper and the type of ink may be automatically acquired, or mode information corresponding to environmental conditions such as the environmental temperature may be automatically acquired. When the mode information is acquired in the mode information acquisition step S100, the process proceeds to a mode determination step S102.

[0250] In the mode determination step S102, it is determined whether the mode information acquired in the mode information acquisition step S100 represents the first mode or the second mode. If the mode information representing the first mode is acquired in the mode determination step S102, the determination is No. If the determination is No, the density unevenness correction data creation sequence shown in FIG. 12 is executed, and density unevenness correction data 302 is created and stored.

[0251] On the other hand, if the mode information indicating the second mode is acquired in the mode determination step S102, the determination is Yes. If the determination is Yes, the correspondence acquisition sequence shown in Fig. 13 is executed, and the correspondence data 300 is acquired and stored.

[0252] In the second mode, the density unevenness correction data creation sequence shown in Fig. 13 is executed using the correspondence data 300 acquired in the correspondence acquisition sequence executed in advance, and density unevenness correction data 302 is created and stored. Note that the mode determination step S102 described in the embodiment may include a mode switching step of selectively switching between the first mode and the second mode.

[0253] [Effects of the second embodiment] The method and device for generating data for correcting density unevenness according to the second embodiment can provide the following advantageous effects.

[0254] [1] In the correspondence acquisition sequence, a line pattern LP extending in a first direction is added to the density step pattern, and correspondence data 300 including the detailed correspondence is created and stored based on the center position of the line pattern portion. This allows the detailed correspondence to be acquired with high robustness against shrinkage of the printing medium.

[0255] [2] Apart from the density unevenness correction data creation sequence, a correspondence acquisition sequence is executed in advance to acquire the correspondence data 300. In the density unevenness correction data creation sequence, density unevenness correction data is created using the previously acquired correspondence data 300. This allows the density unevenness correction data creation sequence to be easily executed.

[0256] [3] The first mode is selectively switched between a first mode in which the density unevenness correction data creation sequence includes a correspondence relationship acquisition sequence and a first mode in which the density unevenness correction data is created using the correspondence relationship data 300 acquired in advance. This allows for a case in which the shrinkage of the printing medium is relatively large. Also, when the shrinkage of the printing medium is relatively small, the density unevenness correction data creation sequence is simply performed.

[0257] [4] In the second mode, the mismatch between the correspondence between the sequences is corrected using common information between the correspondence acquisition sequence and the density unevenness correction data creation sequence. The common information between the sequences uses edge information in the first direction of the density step pattern SP and line mark LM information. This allows high-precision density unevenness correction data to be created even if the shrinkage of the printing medium is relatively large.

[0258] [5] In the second mode, when multiple image sensors IS are provided, the information on the line marks is used to correct the misalignment of the overlapping areas of the image capturing areas of the multiple image sensors IS. This allows high-precision density unevenness correction data to be created even when the shrinkage of the print medium is relatively large.

[0259] [Test chart variation] Fig. 16 is a schematic diagram of a test chart according to a modified example. In the test chart TC4 shown in Fig. 16, a defective nozzle detection pattern NCP is added to the test chart TC2 shown in Fig. 5. Note that Fig. 16 illustrates a test chart TC4 in which a defective nozzle detection pattern NCP is added to the test chart TC2 shown in Fig. 5, but the test chart TC4 according to the modified example may be in a form in which a defective nozzle detection pattern NCP is added to the test chart TC1 shown in Fig. 2, or in which a defective nozzle detection pattern NCP is added to the test chart TC1 shown in Fig. 14.

[0260] 16 shows an example of the defective nozzle detection pattern NCP, which is a ladder pattern including multiple lines extending in the second direction that are drawn using each nozzle of the inkjet head. The ladder pattern may be an inverted pattern in which the lines and background shown in FIG. 16 are inverted.

[0261] That is, the defective nozzle detection pattern NCP may be used to determine whether each nozzle is normal or abnormal based on the analysis information of the defective nozzle detection pattern NCP. For example, an image of the defective nozzle detection pattern NCP may be captured using an image capture device, and the captured data may be analyzed to determine whether each nozzle is normal or abnormal.

[0262] 16 is disposed at one end of the printing medium in the second direction. The defective nozzle detection pattern NCP may be disposed at the other end of the printing medium in the second direction, or may be disposed between the alignment mark AM and line mark LM and the density step pattern SP in the second direction, and may be disposed at any position.

[0263] The defective nozzle detection pattern NCP may be arranged at multiple positions on the printing medium. For example, the defective nozzle detection pattern NCP may be arranged at one end and the other end in the second direction of the printing medium. When multiple defective nozzle detection patterns NCP are formed, the analysis results of the multiple defective nozzle detection patterns NCP may be judged comprehensively to determine whether each nozzle is normal or abnormal.

[0264] In the analysis process of the faulty nozzle detection pattern NCP, the analysis target data of the faulty nozzle detection pattern NCP is extracted using a rough correspondence based on the alignment marks AM, and the extracted analysis target data is input to the analysis processing unit of the faulty nozzle detection pattern NCP. Extraction of the analysis target data of the faulty nozzle detection pattern NCP may be performed using a detailed correspondence based on the line marks LM.

[0265] The defective nozzles that are determined to be abnormal are intentionally masked. The printing position of the defective nozzle is subjected to a non-ejection correction process in which printing is performed using normal nozzles in the vicinity of the defective nozzle. Note that the defective nozzle detection pattern NCP described in the embodiment is an example of an abnormal recording element detection pattern.

[0266] Here, a defective nozzle is a nozzle in which the droplet ejection position and droplet ejection size are outside the normal range, such as a nozzle that does not eject droplets or a nozzle whose ejection direction is significantly curved. A defective nozzle may be called a non-ejecting nozzle, a non-ejecting nozzle, an abnormal nozzle, etc.

[0267] [Application example to inkjet printing system] An example of application of a density unevenness correction data generating method and a density unevenness correction data generating device to an inkjet printing system will be described.

[0268] [Overall configuration of the inkjet printing system] 17 is a diagram showing the overall configuration of an inkjet printing system according to an embodiment of the present invention. The inkjet printing system 400 shown in the figure is equipped with a digital printing device 406 that applies single-pass printing to print a color image on a printing medium.

[0269] The printing medium may be a paper medium such as a sheet of paper or a continuous paper. The printing medium may have a structure in which fibers such as a fabric are woven. The printing medium may be roll paper wound into a roll. The printing medium may be called printing paper or printing paper.

[0270] The inkjet printing system 400 includes a print medium supply device 402, a first intermediate transport device 404, a printing device 406, a second intermediate transport device 408, an inspection device 410, a drying device 412, and a stacking device 414. Each of these devices will be described in detail below.

[0271] [Print media supply device] When the printing medium is in a continuous form, the printing medium supplying device 402 includes a roll storage unit that stores a roll of the printing medium. When the printing medium is in a sheet-like form, the printing medium supplying device 402 includes a tray that stores the printing medium. The printing medium supplying device 402 supplies the printing medium to the first intermediate transport device 404 in response to the printing control of the printing device 406. The printing medium supplying device 402 may include a correction mechanism that corrects the attitude of the printing medium.

[0272] [First intermediate conveying device] The first intermediate transport device 404 delivers the print medium supplied from the print medium supply device 402 to the printing device 406. The first intermediate transport device 404 may have a known configuration according to the form of the print medium. Note that the arrow line from the print medium supply device 402 to the first intermediate transport device 404 indicates the medium transport direction, which is the transport direction of the print medium.

[0273] [Printing device] Printing device 406 includes inkjet head 420C, inkjet head 420M, inkjet head 420Y, and inkjet head 420K. Inkjet head 420C, inkjet head 420M, inkjet head 420Y, and inkjet head 420K are arranged in the above-described order from the upstream side along the medium transport direction.

[0274] Inkjet head 420C ejects cyan ink, inkjet head 420M ejects magenta ink, inkjet head 420Y ejects yellow ink, and inkjet head 420K ejects black ink.

[0275] The inkjet head 420C and the like may be a line head in which multiple nozzles are arranged over a length equal to or greater than the entire length of the print medium in the medium width direction, which is perpendicular to the medium transport direction and parallel to the printing surface of the print medium. An example of the line head configuration is a configuration in which multiple head modules are joined together. The multiple nozzles provided in the inkjet head 420C and the like are arranged in a two-dimensional manner, such as a matrix arrangement.

[0276] The inkjet head 420C may employ a piezoelectric ejection method having a piezoelectric element as an ejection pressure element that generates an ejection pressure. The inkjet head 420C may employ a thermal method that ejects ink by utilizing the film boiling phenomenon of ink.

[0277] The printing device 406 forms a color image on a printing medium using color inks such as cyan ink. The printing device 406 may also include an inkjet head that ejects special color inks other than process inks such as cyan ink, such as an inkjet head that forms a white image that serves as a background image of a color image using white ink.

[0278] The printing device 406 includes a print drum 422. The print drum 422 has a cylindrical shape and is supported so as to be rotatable about a central axis. The print drum 422 includes a print medium support area that supports a print medium on its circumferential surface.

[0279] Inkjet heads 420C etc. are disposed at positions where their nozzle faces face the circumferential surface of print drum 422, and are oriented such that the normal to print drum 422 and the normal to the nozzle face are parallel.

[0280] The rotation shaft of the print drum 422 is connected to a motor (not shown) via a drive mechanism (not shown). When the motor is rotated, the print drum 422 rotates in the direction indicated by the arrow. When the print drum 422 is rotated, the print medium supported on the circumferential surface of the print drum 422 is transported in the direction of rotation of the print drum 422.

[0281] A plurality of suction holes are formed in the print medium support area on the circumferential surface of the print drum 422. The plurality of suction holes are arranged based on a specified pattern. The plurality of suction holes communicate with a suction flow passage (not shown). The suction flow passage is connected to a suction pump (not shown). The suction pump is operated to generate negative pressure in the plurality of suction holes, and the print medium is suctioned and supported on the circumferential surface of the print drum 422.

[0282] The transport form of the print medium in the printing device 406 is not limited to a transport form using the print drum 422. For example, a transport form using a transport belt or a transport form using a plurality of rollers can be applied.

[0283] The printing device 406 includes an in-line sensor 424. The image sensor IS shown in FIG. 1 and the like may be an in-line sensor 424 shown in FIG. 17. The in-line sensor 424 is disposed at a position downstream of the inkjet head 420K in the medium transport direction. The in-line sensor 424 reads a test chart printed on the printing medium and outputs a read signal of the test chart. The printing device 406 detects an abnormality in the nozzles provided in the inkjet head 420C and the like based on the read signal of the test chart.

[0284] The in-line sensor 424 includes an image sensor that captures an image to be printed on the print medium. The image sensor may be a CCD image sensor, a CMOS image sensor, or the like. The in-line sensor 424 has an imaging area that corresponds to the full width of the print medium in the medium width direction. The in-line sensor 424 may be equipped with an optical member such as a condenser lens. Note that CCD is an abbreviation for Charge Coupled Device. CMOS is an abbreviation for Complementary Metal Oxide Semiconductor.

[0285] [Second intermediate conveying device] The second intermediate conveying device 408 delivers the print medium delivered from the print drum 422 to the inspection device 410. The second intermediate conveying device 408 may have a similar configuration to the first intermediate conveying device 404. Note that the arrow line shown on the second intermediate conveying device 408 indicates the medium conveying direction in the second intermediate conveying device 408.

[0286] [Inspection equipment] The inspection device 410 includes an image capture device that captures a print image printed on a print medium. The inspection device 410 outputs a scanned image of the print image. The inspection device 410 can detect defects in the print image based on the scanned image of the print image. The arrows shown on the inspection device 410 indicate the medium transport direction in the inspection device 410.

[0287] [Drying equipment] The drying device 412 performs a drying process on the print medium on which the print image has been printed. The drying device 412 may be equipped with a heater and a fan, and may be configured to blow hot air onto the printed print medium. The drying device 412 is equipped with a drying conveying section that conveys the print medium. As the print medium conveying form applied to the drying conveying section, known conveying forms such as drum conveying, belt conveying, and roller conveying may be applied. The arrow line shown on the drying device 412 indicates the medium conveying direction in the drying device 412.

[0288] [Integration device] The stacking device 414 stores the print medium delivered from the drying device 412. When the print medium is in a continuous form, the stacking device 414 includes a roll storage section that stores a roll on which the print medium is wound. When the print medium is in a sheet form, the stacking device 414 includes a tray in which the print medium is stored.

[0289] The inkjet printing system 400 may employ a two-liquid system that uses a treatment liquid that aggregates or insolubilizes color materials contained in the ink. That is, the inkjet printing system 400 may employ an embodiment that includes a treatment liquid application device that applies treatment liquid to the print medium before printing, and the treatment liquid application device is located upstream of the printing device 406 in the medium transport direction.

[0290] In an embodiment including a treatment liquid application device, a treatment liquid drying device that dries the treatment liquid applied to the print medium may be provided. The treatment liquid drying device is disposed downstream of the treatment liquid application device in the medium transport direction and upstream of the printing device 406 in the medium transport direction.

[0291] [Example of inkjet head configuration] Fig. 18 is a perspective view showing an example of the configuration of the inkjet head shown in Fig. 17. The same configuration can be applied to inkjet head 420C, inkjet head 420M, inkjet head 420Y, and inkjet head 420K shown in Fig. 17. Here, inkjet head 420C and the like are collectively referred to as inkjet head 420.

[0292] The inkjet head 420 has a structure in which a plurality of head modules 430 are connected in a row along the longitudinal direction of the inkjet head 420. The plurality of head modules 430 are integrated and supported by a head frame 432.

[0293] The inkjet head 420 is a line head in which a plurality of nozzles are arranged across a length corresponding to the full width of the print medium in the medium width direction. Note that the nozzles are not shown in Fig. 17. The nozzles are shown in Fig. 18 and labeled with the reference numeral 442.

[0294] The planar shape of the nozzle surface 430A of the head module 430 is a parallelogram. Dummy plates 434 are attached to both ends of the head frame 432. The planar shape of the nozzle surface 430A of the inkjet head 420, including the head module 430 and the dummy plates 434, is a rectangle as a whole.

[0295] A flexible substrate 436 is attached to the head module 430. The flexible substrate 436 is a wiring member that transmits a driving voltage supplied to the head module 430. One end of the flexible substrate 436 is electrically connected to the head module 430, and the other end is electrically connected to a driving voltage supply circuit. Note that the driving voltage supply circuit is not shown in the figure.

[0296] Each of the multiple head modules 430 provided in the inkjet head 420 can be associated with a module number indicating the position of the head module 430, starting from the head module 430 arranged at one end of the inkjet head 420.

[0297] Fig. 19 is a plan view showing an example of the nozzle arrangement of the inkjet head shown in Fig. 18. The central portion of the nozzle surface 430A of the head module 430 is provided with a strip-shaped nozzle arrangement portion 440. The nozzle arrangement portion 440 substantially functions as the nozzle surface 430A.

[0298] A plurality of nozzles 442 are arranged in the nozzle arrangement section 440. The nozzles 442 include nozzle openings 444 formed in the nozzle surface 430A. A structural example of the nozzles 442 will be described later. In the following description, the arrangement of the nozzles 442 may be read as the arrangement of the nozzle openings 444.

[0299] The head module 430 shown in Figure 19 has a planar shape of a parallelogram having a long side end face aligned in the V direction and inclined at an angle β with respect to the medium width direction, as shown with the symbol X, and a short side end face aligned in the W direction and inclined at an angle α with respect to the medium transport direction, as shown with the symbol Y.

[0300] In the head module 430, a plurality of nozzles 442 are arranged in a matrix with respect to the row direction along the V direction and the column direction along the W direction. The nozzles 442 may be arranged in the row direction along the medium width direction and in the column direction obliquely intersecting the medium width direction.

[0301] In the case of the inkjet head 420 in which a plurality of nozzles 442 are arranged in a matrix, a projected nozzle array obtained by projecting each nozzle 442 in the matrix arrangement along the nozzle array direction can be considered to be equivalent to a single nozzle array in which the nozzles 442 are arranged at approximately equal intervals at a density that achieves the maximum recording resolution in the nozzle array direction. The projected nozzle array is a nozzle array obtained by orthogonally projecting each nozzle 442 in the matrix arrangement along the nozzle array direction.

[0302] "Approximately equal intervals" means that the droplet ejection points are substantially equal in intervals as recordable droplet ejection points in a printing device. For example, the concept of equal intervals also includes cases where the intervals are slightly different in consideration of at least one of manufacturing errors and droplet movement on the printing medium due to landing interference. The projected nozzle row corresponds to the actual nozzle row. When the projected nozzle row is taken into consideration, a nozzle number indicating the nozzle position can be associated with each nozzle 442 in the order of the projected nozzles aligned along the nozzle row direction. In other words, the actual arrangement direction of the multiple nozzles 442 is understood to be the medium width direction.

[0303] Although FIG. 19 illustrates an example of inkjet head 420 in which a plurality of nozzles 442 are arranged in a matrix, the plurality of nozzles 442 may be arranged in a single row, or in a zigzag arrangement in two rows.

[0304] The effective density of the nozzles 442 in the medium width direction corresponds to the print resolution in the medium width direction. An example of the print resolution in the medium width direction is 1200 dots per inch. Dots per inch, which represents the number of dots per inch, can be referred to as dpi, which is an abbreviation of Dot Per Inch.

[0305] [Electrical configuration of the inkjet printing system] Fig. 20 is a functional block diagram showing the electrical configuration of the inkjet printing system shown in Fig. 17. The inkjet printing system 400 shown in Fig. 17 includes a control device 450 shown in Fig. 20. A computer including a processor is applied to the control device 450.

[0306] The control device 450 executes various programs to control the operation of each part of the inkjet printing system 400. The control device 450 includes a system control unit 451, a transport control unit 452, a printing control unit 454, a drying control unit 456, and an inspection control unit 458.

[0307] The system control unit 451 functions as an overall control unit that comprehensively controls various control units such as the transport control unit 452. The system control unit 451 functions as a memory controller that controls reading and storing of data from and to a storage device such as the memory 470.

[0308] The transport control unit 452 controls the operation of the transport device 460 based on a command signal transmitted from the system control unit 451. That is, the transport control unit 452 operates the transport device 460 based on preset medium transport conditions, and controls the transport of the print medium.

[0309] 20 includes the first intermediate conveying device 404, the second intermediate conveying device 408, the printing drum 422, the inspection conveying device provided in the inspection device 410, and the drying conveying device provided in the drying device 412, all of which are shown in FIG 17. The conveying device 460 may also include the printing medium supply device 402 and the accumulation device 414 shown in FIG 17.

[0310] The print control unit 454 controls the operation of the printing device 406 based on a command signal transmitted from the system control unit 451. That is, the print control unit 454 operates the printing device 406 based on preset printing conditions to control printing on a print medium.

[0311] The print control unit 454 includes an image processing unit. The image processing unit performs color separation processing, color conversion processing, and halftone processing on the print data to generate dot data for printing. The image processing unit performs various correction processes such as density unevenness correction processing and non-discharge correction processing. The density unevenness correction processing is performed for each nozzle using density unevenness correction data created by the density unevenness correction data creating device 100 and stored in the density unevenness correction data storage unit 214.

[0312] The print control unit 454 includes a drive voltage generation unit that generates a drive voltage to be supplied to the inkjet head 420 based on the halftone data for each color. The print control unit 454 includes a drive voltage output unit that outputs a drive voltage to be supplied to the inkjet head 420. The drive voltage output unit includes a power amplifier circuit.

[0313] The print control unit 454 includes a discharge control unit. The discharge control unit generates a discharge control signal that specifies the discharge timing for each nozzle from dot data generated by the image processing unit. The discharge control unit also generates a drive waveform signal that is applied to the drive voltage using drive waveform data that is generated and stored in advance.

[0314] The print control unit 454 includes a head drive circuit. The head drive circuit uses a drive waveform signal to generate a drive voltage to be supplied to the piezoelectric element for each nozzle provided in the inkjet head 420. The head drive circuit generates an ejection timing signal that controls the on / off of the piezoelectric element for each nozzle. The head drive circuit supplies a drive voltage to each piezoelectric element for each nozzle at a specified ejection timing.

[0315] The drying control unit 456 controls the operation of the drying device 412 based on a command signal transmitted from the system control unit 451. That is, the drying control unit 456 operates the drying device 412 based on preset drying conditions to control the drying process for the print medium.

[0316] The inspection control unit 458 controls the operation of the inspection device 410 based on a command signal transmitted from the system control unit 451. That is, the inspection control unit 458 operates the inspection device 410 based on preset inspection conditions to control the inspection of the printed matter. The inspection control unit 458 transmits the inspection results of the printed matter to the system control unit 451. In accordance with the inspection results of the printed matter, the system control unit 451 transmits command signals for operations corresponding to the inspection results of the printed matter to various control units such as the transport control unit 452.

[0317] The control device 450 includes a memory 470. The memory 470 stores programs, parameters, and data used by the control device 450. The system control unit 451 reads out and executes various programs stored in the memory 470 to realize various functions of the inkjet printing system 400. The system control unit 451 reads out parameters and data required for executing the various programs from the memory 470.

[0318] The system control unit 451 acquires various detection information from various sensors 472 provided in the inkjet printing system 400. Examples of the various sensors 472 include a temperature sensor and a print medium position detection sensor. The system control unit 451 transmits command signals to various control units according to the acquired sensor information.

[0319] Fig. 21 is a block diagram showing an example of a hardware configuration of the electrical configuration shown in Fig. 20. Note that the processor 502, communication interface 506, input / output interface 508, bus 510, input device 512, and display device 514 shown in Fig. 21 are the same components as the processor 102, communication interface 106, input / output interface 108, bus 110, input device 120, and display device 122 shown in Fig. 7, and the description here will be omitted as appropriate.

[0320] The computer-readable medium 504 shown in Fig. 21 includes a memory 520 and a storage 522, similar to the computer-readable medium 504 shown in Fig. 7. The memory 520 stores various programs that realize various functions of the inkjet printing system 400. In addition, the storage 522 stores various data and various parameters used when the various programs are executed.

[0321] The memory 520 stores a transport control program 530, a print control program 532, a drying control program 534, and an inspection control program 536. The transport control program 530 is applied to a transport control unit 452 shown in Fig. 20. The transport control program 530 realizes the function of a transport device 460 that transports the print medium.

[0322] The print control program 532 is applied to the print control unit 454. The print control program 532 realizes various functions of the printing device 406. The drying control program 534 is applied to the drying control unit 456. The drying control program 534 realizes the function of the drying device 412 that dries the printed print medium. The inspection control program 536 is applied to the inspection control unit 458. The inspection control program 536 realizes the function of the inspection device 410 that inspects the printed image.

[0323] The memory 520 stores the density unevenness correction data update program 130. The density unevenness correction data update program 130 shown in Fig. 21 is the same as the density unevenness correction data update program 130 shown in Fig. 7. The memory 520 may store the density unevenness correction data update program 130A shown in Fig. 9.

[0324] The above-described embodiment of the present invention may be modified, added, or deleted as appropriate without departing from the spirit of the present invention. The present invention is not limited to the above-described embodiment, and many modifications are possible within the technical concept of the present invention by those having ordinary skill in the art. [Explanation of symbols]

[0325] 100 Density unevenness correction data creation device 100A Density unevenness correction data creation device 102 processors 104 Computer-readable medium 106 Communication Interface 108 Input / Output Interface 110 Bus 112 Memory 112A Memory 114 Storage 120 Input Device 122 Display device 130 Density unevenness correction data update program 131 Detection and Processing Program 132 Alignment mark detection program 134 Line mark center estimation program 136 Concentration Data Estimation Program 138 Density unevenness correction data creation program 150 Density unevenness correction data 180 Printing equipment 190 Image Sensor System 200 Density unevenness correction data acquisition section 202 Print Data Creation Department 204 Scan Image Creation Department 205 Detection Improvement Processing Unit 206 Alignment mark detection section 208 Line mark center estimation section 210 Concentration data estimation unit 212 Density unevenness correction data creation section 214 Density unevenness correction data storage unit 300 Correspondence Data 302 Density unevenness correction data 400 Inkjet Printing System 402 Print media supply device 404 First intermediate conveying device 406 Printing device in the media transport direction 406 Printing device 408 Second intermediate conveying device 410 Inspection Equipment 412 Drying equipment 414 Accumulation Device 420 Inkjet head 420C Inkjet Head 420K Inkjet Head 420M Inkjet Head 420Y Inkjet Head 422 Printing drum 424 Inline Sensor 430 Head Module 430A Nozzle surface 432 Head Frame 434 Dummy Plate 436 Flexible PCB 440 Nozzle arrangement section 442 Nozzle 444 Nozzle opening 450 Control Device 451 System Control Unit 452 Transport control section 454 Printing control unit 456 Drying control unit 458 Inspection Control Unit 460 Transport Equipment 470 Memory 472 Sensors 502 processor 504 Computer-readable medium 506 Communication Interface 508 Input / Output Interface 510 Bus 512 Input Device 514 Display device 520 Memory 522 Storage 530 Transport Control Program 532 Printing control program 534 Drying Control Program 536 Inspection Control Program 1000 Line mark adjustment screen 1002 Line mark display area 1004 Scale at bottom 1010 Center density setting section 1012 Peripheral density setting section 1014 Central density input section 1016 Peripheral density input section 1020 Aspect ratio setting section 1021 aspect ratio input section 1022 Center width setting section 1023 Center width input section 1024 Periphery width setting section 1025 Periphery width input section 1026 Line mark number setting section 1027 Line mark number input section 1028 Interval setting section 1029 Interval input section 1030 Settings button 1032 Cancel button AM alignment mark CP concentration pattern IS Image Sensor LM Line Mark LMC central line section LMP peripheral line section LP Line Pattern NCP defective nozzle detection pattern NP Non-patterned part S20 to S26 Each step of the density unevenness correction data update process S40 to S42: Each step of the density unevenness correction data generation sequence S100 to S102: Steps of the density unevenness correction data creation method when multiple modes are provided

Claims

1. 1. A method for generating density unevenness correction data that is applied to single-pass printing using a line head in which a plurality of recording elements are arranged along a first direction, comprising: a test chart image acquisition step of acquiring a test chart image obtained by photographing a first test chart printed on a printing medium, the test chart including a density step pattern including one or more density patterns corresponding to one or more density values, a plurality of alignment marks having mutually different shapes, and a plurality of line marks having a shape extending in a second direction perpendicular to the first direction; a correspondence information acquiring step of acquiring correspondence information representing a correspondence relationship between a theoretical position on the first test chart and a photographing position on a photographed image of the test chart for the first direction and the second direction; a density unevenness correction data creating step of creating the density unevenness correction data by using density information of the density step pattern in the photographed test chart image; Including, The correspondence relationship information acquisition step includes: acquiring a rough correspondence relationship indicating a correspondence relationship between the theoretical position in the first direction and the photographing position by using information on a position of each of the alignment marks in the first direction specified based on a shape of each of the alignment marks; acquiring a detailed correspondence relationship between the theoretical position and the photographing position in the first direction, the detailed correspondence relationship indicating a more detailed correspondence relationship than the rough correspondence relationship, by using information on the positions of the plurality of line marks estimated using the acquired rough correspondence relationship; The density unevenness correction data creation process uses the detailed correspondence relationship for the first direction to estimate density values ​​for each position in the first direction of the density step pattern, thereby creating the density unevenness correction data.

2. the density unevenness correction data generating step includes an alignment mark detecting step of detecting the plurality of alignment marks from the captured image of the test chart, 2. The density unevenness correction data generating method according to claim 1, wherein the alignment mark detection step includes a detection improvement processing step of performing a detection improvement process on the photographed image of the test chart to improve a probability of detecting the alignment mark.

3. 3. The density unevenness correction data generating method according to claim 2, wherein the correspondence information acquiring step acquires the detailed correspondence in the first direction from a photographed image of the test chart that has not been subjected to the detection improvement processing.

4. The detection enhancement processing step includes: determining an amount of luminance contrast enhancement for the test chart photographed image from luminance information of the alignment mark not subjected to the detection improvement processing; 3. The density unevenness correction data generating method according to claim 2, further comprising the step of: performing contrast enhancement processing on the photographed image of the test chart using the determined amount of luminance contrast enhancement.

5. 3. The density unevenness correction data generating method according to claim 2, wherein the detection improvement processing step applies at least one of blurring filter processing, median filter processing, and morphology processing to the photographed image of the test chart.

6. 2. The density unevenness correction data generating method according to claim 1, wherein the plurality of line marks have the same shape.

7. 2. The density unevenness correction data generating method according to claim 1, wherein the correspondence information acquiring step acquires the correspondence in the second direction based on information on positions of the plurality of alignment marks in the second direction.

8. 2. The density unevenness correction data creation method according to claim 1, wherein the correspondence information acquisition process includes a line mark position estimation process for estimating the position of the line mark in the first direction by applying image processing to the line mark in the test chart photographed image when creating the detailed correspondence in the first direction.

9. The line mark position estimation step includes:

9. The density unevenness correction data creation method according to claim 8, wherein, for the estimated positions of the plurality of line marks, a line mark for which a difference between a position of the line mark estimated using the rough correspondence relationship and a position of the line mark estimated using the detailed correspondence relationship exceeds a specified range is excluded from the line marks used to obtain the detailed correspondence relationship.

10. The density unevenness correction data creating step includes: using the correspondence relationship, determining at least one theoretical position for each of the recording elements for each density pattern included in the density step pattern from the photographed image of the test chart; averaging or integrating the test chart photographed image within the range of the density pattern in a second direction for the theoretical positions of the recording elements obtained from the test chart photographed image; 2. The method for generating data for correcting density unevenness according to claim 1, further comprising estimating a density for each of said density patterns for each of said recording elements.

11. a mode switching step of selectively switching between a first mode in which the density unevenness correction data is created based on a captured image of the first test chart and a second mode which is performed separately from the first mode and in which the density unevenness correction data is created based on a second test chart in which a line pattern extending in the second direction is superimposed on the density step pattern included in the first test chart, In the second mode, estimating a position of the line pattern in the first direction for a captured test chart image of the second test chart; acquiring the detailed correspondence relationship in the first direction using information on the estimated position of the line pattern in the first direction; 2. The method of claim 1, further comprising the steps of: estimating a density value for each position in the first direction of the density step pattern using the detailed correspondence relationship in the first direction;

12. In the second mode, The density unevenness correction data creation method of claim 11, further comprising the step of correcting a deviation in the correspondence between the first sequence and the second sequence by utilizing common information common to a first sequence for generating density unevenness correction data to be applied to the first mode and a second sequence for generating density unevenness correction data to be applied to the second mode.

13. The density unevenness correction data generating method according to claim 12 , wherein the common information includes information on an edge of the density pattern in the first direction.

14. The density unevenness correction data generating method according to claim 12 , wherein the common information includes information about the positions of the plurality of line marks in the first direction.

15. 13. The density unevenness correction data creation method according to claim 12, further comprising an overlap area correction process for correcting a deviation in the correspondence between the first sequence and the second sequence in the first direction by using information on the line marks included in an overlap area where the shooting areas of the image sensors overlap when the test chart shooting image is generated using a plurality of image sensors.

16. The overlap area correction step includes: The density unevenness correction data creation method according to claim 15, further comprising the step of correcting the deviation in the correspondence between the first sequence and the second sequence using information obtained by statistically processing the positions of the line marks arranged in the overlapping area.

17. 1. A density unevenness correction data generating device that generates density unevenness correction data that is applied to single-pass printing using a line head in which a plurality of recording elements are arranged along a first direction, comprising: one or more processors; One or more memories in which programs to be executed by the one or more processors are stored; Equipped with The one or more processors execute instructions of the program, a density step pattern including one or more density patterns corresponding to one or more density values, a plurality of alignment marks having mutually different shapes, and a plurality of line marks having a shape extending in a second direction perpendicular to the first direction, the first test chart being printed on a printing medium; and a test chart image is acquired by photographing the first test chart; acquiring correspondence relationship information that indicates a correspondence relationship between a theoretical position on the first test chart and a photographing position on a photographed image of the test chart for the first direction and the second direction; creating the density unevenness correction data using density information of the density step pattern in the photographed image of the test chart; When acquiring the correspondence information, acquiring a rough correspondence relationship indicating a correspondence relationship between the theoretical position in the first direction and the photographing position by using information on a position of each of the alignment marks in the first direction specified based on a shape of each of the alignment marks; acquiring a detailed correspondence relationship between the theoretical position and the photographing position in the first direction, the detailed correspondence relationship indicating a more detailed correspondence relationship than the rough correspondence relationship, by using information on the positions of the plurality of line marks estimated using the acquired rough correspondence relationship; A density unevenness correction data creation device that, when creating the density unevenness correction data, uses the detailed correspondence relationship for the first direction to estimate a density value for each position in the first direction of the density step pattern, thereby creating the density unevenness correction data.

18. a line head in which a plurality of recording elements are arranged along a first direction; a density unevenness correction data creating device that creates density unevenness correction data that is applied to single-pass printing using the line head; The density unevenness correction data generating device includes: one or more processors; One or more memories in which programs to be executed by the one or more processors are stored; Equipped with The one or more processors execute instructions of the program, a density step pattern including one or more density patterns corresponding to one or more density values, a plurality of alignment marks having mutually different shapes, and a plurality of line marks having a shape extending in a second direction perpendicular to the first direction, the first test chart being printed on a printing medium; and a test chart image is acquired by photographing the first test chart; acquiring correspondence relationship information that indicates a correspondence relationship between a theoretical position on the first test chart and a photographing position on a photographed image of the test chart for the first direction and the second direction; creating the density unevenness correction data using density information of the density step pattern in the photographed image of the test chart; When acquiring the correspondence information, acquiring a rough correspondence relationship indicating a correspondence relationship between the theoretical position in the first direction and the photographing position by using information on a position of each of the alignment marks in the first direction specified based on a shape of each of the alignment marks; acquiring a detailed correspondence relationship between the theoretical position and the photographing position in the first direction, the detailed correspondence relationship indicating a more detailed correspondence relationship than the rough correspondence relationship, by using information on the positions of the plurality of line marks estimated using the acquired rough correspondence relationship; A printing system that, when creating the density unevenness correction data, estimates a density value for each position in the first direction of the density step pattern using the detailed correspondence relationship for the first direction, thereby creating the density unevenness correction data.

19. A program for creating density unevenness correction data to be applied to single-pass printing using a line head in which a plurality of recording elements are arranged along a first direction, comprising: The computer a density step pattern including one or more density patterns corresponding to one or more density values, a plurality of alignment marks having mutually different shapes, and a plurality of line marks having a shape extending in a second direction perpendicular to the first direction, the first test chart being printed on a printing medium; and a test chart image is acquired by photographing the first test chart; acquiring correspondence relationship information that indicates a correspondence relationship between a theoretical position on the first test chart and a photographing position on a photographed image of the test chart for the first direction and the second direction; creating the density unevenness correction data using density information of the density step pattern in the photographed image of the test chart; When acquiring the correspondence information, acquiring a rough correspondence relationship indicating a correspondence relationship between the theoretical position in the first direction and the photographing position by using information on a position of each of the alignment marks in the first direction specified based on a shape of each of the alignment marks; acquiring a detailed correspondence relationship between the theoretical position and the photographing position in the first direction, the detailed correspondence relationship indicating a more detailed correspondence relationship than the rough correspondence relationship, by using information on the positions of the plurality of line marks estimated using the acquired rough correspondence relationship; a program for estimating a density value for each position in the first direction of the density step pattern using the detailed correspondence relationship for the first direction when creating the density unevenness correction data, thereby creating the density unevenness correction data;

20. A test chart used in creating density unevenness correction data applied to single-pass printing using a line head in which a plurality of recording elements are arranged along a first direction, A test chart including a density step pattern including one or more density patterns corresponding to one or more density values, a plurality of alignment marks having different shapes, and a plurality of line marks having a shape extending in a second direction perpendicular to the first direction.

21. 21. The test chart according to claim 20, wherein the plurality of line marks have the same shape.

22. 21. The test chart according to claim 20, further comprising an abnormal recording element detection pattern used when detecting an abnormality in the recording element.

23. 23. The test chart according to claim 22, wherein the abnormal recording element detection pattern is a plurality of lines recorded using each of the plurality of recording elements, the positions of the recording elements in the first direction differing for each recording element, and the abnormal recording element detection pattern includes a plurality of lines extending in the second direction.

24. 1. A test chart data creation device that creates test chart data representing a test chart used to create density unevenness correction data that is applied to single-pass printing using a line head in which a plurality of recording elements are arranged along a first direction, comprising: the test chart includes a density step pattern including one or more density patterns corresponding to one or more density values, a plurality of alignment marks having mutually different shapes, and a plurality of line marks having a shape extending in a second direction perpendicular to the first direction; A test chart data creation device comprising a graphical user interface used when adjusting at least one of alignment mark parameters applied to the alignment marks and line mark parameters applied to the line marks.

25. 25. The test chart data creation device of claim 24, wherein the graphical user interface is used to adjust at least one of the size of the alignment mark, the aspect ratio of the alignment mark, the density of the alignment mark, the number of the alignment marks, and the spacing between adjacent alignment marks.

26. 25. The test chart data creation device according to claim 24, wherein the graphical user interface is used to adjust at least one of the size of the line marks, the aspect ratio of the line marks, the density of the line marks, the number of the line marks, and the spacing between adjacent line marks.

27. the line mark includes a low density portion having a relatively low density value and a high density portion having a density value higher than the low density portion, 27. The test chart data creation device according to claim 26, wherein the graphical user interface is used when adjusting at least one of the density of the low density portion, the length of the low density portion in the first direction, the density of the high density portion, and the length of the high density portion in the first direction.

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