JP2020049741A - Image recording method, method for creation of data for correction, ink jet recording device, and program - Google Patents

Abstract

To provide an image recording method by which oscillation unevenness with reproductivity due to relative speed variation between an ink jet head and a recording medium can be adequately corrected, a method for creation of data for correction, an ink jet recording device, and a program.SOLUTION: According to this image recording method, droplet ejection is repeated simultaneously from each of plural nozzles for measurement and at a constant time interval, thereby recording plural dot rows for measurement, positional deviation values of dots are calculated from reading data of the dot rows for measurement, the positional deviation values of dots, which are droplet-ejected at the same moment, are averaged, and data for correction, which represents relative positional deviation value between an ink jet head and the recording medium, is calculated and is stored in a storage part. Image data is corrected by use of stored data for correction, and thus, ink ejection operation is controlled. The plural nozzles for measurement, which perform droplet ejection at the same moment, are connected to respective separate branch channels of an ink flow channel in the head.SELECTED DRAWING: Figure 16

Description

  The present invention relates to an image recording method, a correction data creating method, an inkjet recording apparatus, a recording control apparatus, and a program, and more particularly to an image correction technique when an image is recorded using an inkjet head.

  Patent Document 1 discloses an ink jet printer using a line type recording head, density unevenness due to two-dimensional meandering in the conveying direction of the recording medium, displacement due to vibration, change in the conveying speed of the recording medium, or speed unevenness. Is described. An inkjet printer is equivalent to an “inkjet recording device”.

  Patent Literature 2 discloses a correction technique that suppresses a landing position shift due to a change in the transport speed of a recording medium.

  Patent Literature 3 discloses an ink jet printer having a function of adjusting a landing position deviation between a plurality of head units to form a good image.

  Further, Patent Literatures 4 and 5 disclose techniques for suppressing density unevenness caused by periodic positional fluctuation between a print head and a print medium.

JP-A-2003-291325 Japanese Patent Application Laid-Open No. 2009-11312 JP 2006-27162 A JP 2011-42081 A JP 2010-173154 A

  When the relative speed between the ink jet head (recording head) and the recording medium fluctuates, the density of the image recorded on the recording medium fluctuates and is visually recognized as "unevenness", which is problematic. Causes of the fluctuation of the relative speed between the ink jet head and the recording medium include, for example, fluctuation of the conveying speed of the recording medium and / or natural vibration of the ink jet head. In this specification, density unevenness, which is an image defect caused by relative speed fluctuation between the inkjet head and the recording medium, may be referred to as “vibration unevenness”, and fluctuation in the relative speed between the inkjet head and the recording medium may be referred to as “relative vibration”.

  In order to suppress such vibration unevenness, the following measures 1 to 3 are generally considered.

  [Countermeasure 1] Control the conveyance of the recording medium so that the speed fluctuation of the recording medium is reduced.

  [Countermeasure 2] The jetting cycle is corrected by detecting the speed fluctuation of the recording medium. The correction of the jetting cycle corresponds to correcting the ink ejection timing.

  [Countermeasure 3] In order to suppress the vibration of the inkjet head, the rigidity of the mechanism for holding the inkjet head is increased.

  However, all of the measures 1 to 3 have a problem that the physical mechanism and / or the control system becomes large and / or complicated and the cost increases.

  Further, with respect to the measure 2, the fluctuation in the recording medium conveyance direction (y direction) can be corrected, but the fluctuation in the medium width direction (x direction) orthogonal to the conveyance direction cannot be corrected. In particular, in the case of an ink jet recording apparatus that employs a method in which a continuous medium is roll-conveyed, vibration in the x direction is likely to occur, which is a problem.

  The present invention has been made in view of such circumstances, and an image recording method, a correction data creation method, and an inkjet method capable of appropriately correcting reproducible vibration unevenness due to relative speed fluctuation between an inkjet head and a recording medium. It is an object to provide a recording device, a recording control device, and a program.

  An image recording method according to an aspect of the present disclosure is an image recording method that records an image on a recording medium using an inkjet head, and includes a method of recording a plurality of measurement nozzles specified from a nozzle array of the inkjet head. A step of recording a plurality of measurement dot arrays on the recording medium by repeatedly ejecting droplets at a constant time interval and conveying the recording medium, and converting the plurality of measurement dot arrays recorded on the recording medium into an image. A step of reading using a reading device, a step of calculating a positional deviation value of a dot included in the measurement dot array from read data indicating a read image of the measurement dot array obtained via the image reading device, Of the dots ejected from each of the measurement nozzles, the average of the positional deviation values of the dots ejected at the same moment is averaged to determine the relationship between the ink jet head and the recording medium. Calculating correction data representing the positional deviation value, storing the correction data in the storage unit, correcting the image data using the correction data stored in the storage unit, Controlling the ink ejection operation of the inkjet head using the image data obtained, the ink flow path provided inside the inkjet head, a plurality of branch flow paths, and a main flow path to which the plurality of branch flow paths are connected An image recording method in which a plurality of nozzles are connected to each of a plurality of branch channels, and a plurality of measurement nozzles that perform droplet ejection at the same moment are connected to separate branch channels, respectively. It is.

  According to this aspect, the correction data representing the relative positional deviation value between the inkjet head and the recording medium is calculated using the positional deviation values of dots ejected at the same moment from a plurality of measurement nozzles connected to different branch channels. Is done. The correction data is calculated by averaging the positional deviation values of the dots ejected using a plurality of measurement nozzles, so that the influence of the reading error of the dot position is reduced. Furthermore, according to this aspect, since the plurality of measurement nozzles that eject droplets at the same moment are connected to different branch channels, landing position deviation due to crosstalk in the ink channel is also suppressed. Thereby, the calculation accuracy of the relative position shift value between the inkjet head and the recording medium is improved.

  Note that the image recording method according to the present disclosure may be understood as an image correction method for correcting an image defect caused by a relative speed fluctuation between an inkjet head and a recording medium in an inkjet recording apparatus. Further, the image recording method of the present disclosure can be understood as a method of producing an image recorded matter (printed matter) using an inkjet head, and includes application as a printed matter manufacturing method.

  In the image recording method according to another aspect of the present disclosure, the recording medium is conveyed in the first direction, and each of the plurality of measurement nozzles is in a second direction that is a width direction of the recording medium orthogonal to the first direction. In the step of calculating the position shift value, the position shift values in the first direction and the second direction are calculated, and the step of calculating the correction data is performed in the first direction and the second direction. May be configured to calculate the correction data representing the respective positional deviation values.

  For example, the first direction can be referred to as “y direction” and the second direction can be referred to as “x direction”. According to this aspect, appropriate image correction can be performed for two-dimensional relative speed fluctuations in the x direction and the y direction.

  In the image recording method according to still another aspect of the present disclosure, the step of calculating the correction data includes ejecting a dot from a positional deviation value of a dot ejected at the same instant among a plurality of measurement dot rows. The configuration may include a step of calculating correction data by extrapolating the positional deviation value of the nozzle area that has not been performed.

  Since the measurement nozzles are a part of the nozzles in the nozzle array of the inkjet head, the positional deviation value relating to the positions of the nozzles other than the measurement nozzles is extrapolated from the positional deviation value of the dots due to the ejection from the measurement nozzles. You may ask. Further, an interpolation (interpolation) process may be performed as necessary.

  In an image recording method according to still another aspect of the present disclosure, when an image is recorded on a recording medium using a plurality of inkjet heads, each inkjet head has correction data, and each inkjet head has its own correction data. The configuration may be such that the image data corresponding to each ink jet head is corrected using the correction.

  As a configuration using a plurality of ink jet heads, for example, there is a mode in which an ink jet head is provided for each color of ink, a mode in which two or more ink jet heads ejecting ink of the same color are provided, or a mode in which these are combined. obtain.

  In the image recording method according to still another aspect of the present disclosure, the measurement dot row corresponds to at least one cycle of the repetition pattern when the relative speed fluctuation between the inkjet head and the recording medium is reproduced in a constant repetition pattern. The correction data may include a dot row having a length, and the correction data may include data corresponding to one cycle of the repeating pattern.

  It is preferable to calculate the correction data for one cycle by using the measurement result of the measurement dot row including one cycle of the relative speed fluctuation with reproducibility. When the cycle of the relative speed change in the first direction is different from the cycle of the relative speed change in the second direction, one cycle of correction data may be calculated for each direction.

  In the image recording method according to still another aspect of the present disclosure, the recording medium is conveyed using a rotating member, and a relative speed change between the inkjet head and the recording medium is reproduced in a rotation cycle of the rotating member. The application data may be configured to include data corresponding to the rotation cycle of the rotating member.

  The rotating member may be, for example, a drum, an endless belt, a roller, or the like.

  In the image recording method according to still another aspect of the present disclosure, the recording medium may be a continuous medium, and may have a configuration in which the recording medium is roll-conveyed.

  In the image recording device according to still another aspect of the present disclosure, the inkjet head may be a line head configured by connecting a plurality of head modules.

  In the image recording apparatus according to still another aspect of the present disclosure, at least some of the plurality of measurement nozzles that eject droplets at the same moment are connected to separate branch channels in the same head module. It may be a configuration.

  In the image recording apparatus according to still another aspect of the present disclosure, at least some of the plurality of measurement nozzles that eject droplets at the same moment may be configured to belong to different head modules.

  In the image recording apparatus according to still another aspect of the present disclosure, the plurality of measurement nozzles that eject droplets at the same moment include a plurality of nozzles connected to different branch channels in the same head module, and are different. A configuration including another plurality of nozzles belonging to the head module may be employed.

  A correction data creating method according to another aspect of the present disclosure is a method of creating correction data used when correcting an image defect caused by a relative speed change between an inkjet head and a recording medium in an inkjet recording apparatus, A plurality of dot rows for measurement are recorded on a recording medium by repeatedly ejecting droplets at a constant time interval from each of a plurality of measurement nozzles specified from a nozzle array of an ink jet head and transporting the recording medium. And reading the plurality of measurement dot rows recorded on the recording medium using an image reading device, and from read data indicating a read image of the measurement dot row obtained via the image reading device, Calculating the positional deviation value of the dots included in the measurement dot row; and determining the positions of the dots ejected from each of the plurality of measurement nozzles. Calculating the correction data representing the relative positional deviation value between the inkjet head and the recording medium by averaging the positional deviation values of the dots ejected at the same moment; and storing the correction data in the storage unit. Including, the ink flow path provided inside the inkjet head has a structure including a plurality of branch flow paths, a main flow path to which the plurality of branch flow paths are connected, and each of the plurality of branch flow paths has a plurality of A plurality of measurement nozzles that are connected to each other and eject droplets at the same moment are a method of creating correction data that are connected to separate branch channels.

  For example, the correction data obtained by executing the correction data creation method of the present embodiment can be stored in the storage unit of the inkjet recording apparatus in advance. The ink jet recording apparatus has a function of correcting an image defect (vibration unevenness) due to a relative speed fluctuation between the ink jet head and the recording medium using correction data stored in advance. Further, the inkjet recording apparatus may have a function of performing the correction data creation method of this aspect and updating the correction data to the latest data.

  In the correction data creating method according to this aspect, the same matters as those specified in each aspect of the image recording method described above can be appropriately combined.

  An inkjet recording apparatus according to another aspect of the present disclosure includes an inkjet head, a transport unit that transports a recording medium to the inkjet head, and a plurality of measurement nozzles specified from a nozzle array of the inkjet head. A first control unit that controls the recording of a plurality of dot rows for measurement on the recording medium by simultaneously repeating the droplet ejection at a constant time interval and conveying the recording medium; and a plurality of recording units recorded on the recording medium. An image reading device that reads a measurement dot row, and a process of calculating a positional deviation value of a dot included in the measurement dot row from read data indicating a read image of the measurement dot row obtained via the image reading apparatus. Of the dots ejected from each of the plurality of measurement nozzles, the average of the positional deviation values of the dots ejected at the same moment, the inkjet head A process of calculating correction data representing a relative displacement value of the recording medium; a correction data calculation processing unit that performs the processing; a storage unit that stores the correction data; and the correction data stored in the storage unit A correction processing unit that corrects image data using the image processing unit, and a second control unit that controls the ink ejection operation of the inkjet head using the image data corrected by the correction processing unit. The ink flow path has a structure including a plurality of branch flow paths and a main flow path to which the plurality of branch flow paths are connected.A plurality of nozzles are connected to each of the plurality of branch flow paths, and at the same moment, The plurality of measurement nozzles that perform droplet ejection are ink jet recording apparatuses that are respectively connected to different branch channels.

  In the ink jet recording apparatus according to this aspect, the same matters as those specified in each aspect of the image recording method described above can be appropriately combined. In such a case, the elements of the steps (processes) of the processes and operations specified in the image recording method can be grasped as elements of the processing unit, the functional unit, or the device or the like as means for performing the corresponding processes and operations. it can.

  A recording control device according to another aspect of the present disclosure is a recording control device that controls an inkjet recording device, and includes a plurality of measurement control devices specified from a nozzle array of an inkjet head used in the inkjet recording device. A first control unit that controls the recording of a plurality of measurement dot arrays on the recording medium by repeatedly ejecting droplets from each of the nozzles at a constant time interval and conveying the recording medium; and recording on the recording medium. The position deviation value of the dots included in the measurement dot row is calculated from the read data indicating the read image of the measurement dot row obtained by reading the plurality of measurement dot rows using the image reading device. Processing, and among the dots ejected from each of the plurality of measurement nozzles, the average of the positional deviation values of the dots ejected at the same moment is averaged to the inkjet head. Calculating a correction data representing a relative position shift value of the recording medium, a correction data calculation processing unit for performing the processing, a storage unit for storing the correction data, and a correction data stored in the storage unit. A correction processing unit that corrects the image data using the data, and a second control unit that controls the ink ejection operation of the inkjet head using the image data corrected by the correction processing unit. The provided ink flow path has a structure including a plurality of branch flow paths and a main flow path to which the plurality of branch flow paths are connected, and a plurality of nozzles are connected to each of the plurality of branch flow paths. The plurality of measurement nozzles that perform droplet ejection are recording control devices that are respectively connected to different branch channels.

  The recording control device according to the present embodiment can appropriately combine the same items as those specified in each embodiment of the image recording method described above. In such a case, the elements of the steps (processes) of the processes and operations specified in the image recording method can be grasped as elements of the processing unit, the functional unit, or the device or the like as means for performing the corresponding processes and operations. it can.

  The recording control device may be configured as a single device, or may be configured by combining a plurality of devices. For example, the recording control device can be realized using one or a plurality of computers. The term “apparatus” includes the concepts of “system” and “module”.

  A program according to another embodiment of the present disclosure is a program for causing a computer to realize a control function of an inkjet recording apparatus, and includes a plurality of programs specified from a nozzle array of an inkjet head used in the inkjet recording apparatus. A first control function of recording a plurality of measurement dot arrays on a recording medium by repeatedly ejecting droplets at a constant time interval from each of the measurement nozzles at the same time and conveying the recording medium, and recording on the recording medium. The position deviation value of the dots included in the measurement dot row is calculated from the read data indicating the read image including the measurement dot row obtained by reading the plurality of measurement dot rows using the image reading device. Function, and among the dots ejected from each of the plurality of measurement nozzles, the position deviation value of the dot ejected at the same moment is averaged. A function of calculating correction data representing a relative position shift value between the inkjet head and the recording medium, a function of storing correction data, and a correction of correcting image data using the stored correction data. A program for causing a computer to implement a processing function and a second control function of controlling an ink ejection operation of an inkjet head using image data corrected by the correction processing function, and is provided inside the inkjet head. The ink channel has a structure including a plurality of branch channels and a main channel to which the plurality of branch channels are connected.A plurality of nozzles are connected to each of the plurality of branch channels, and droplets are ejected at the same moment. The plurality of measurement nozzles to be executed are programs connected to separate branch channels.

  In the program according to this aspect, the same items as those specified in each aspect of the image recording method described above can be appropriately combined. In that case, the element of the step (process) of the process or operation specified in the image recording method can be grasped as a program element for implementing the corresponding step or function of the operation or operation.

  ADVANTAGE OF THE INVENTION According to this invention, the calculation accuracy of the relative positional deviation value of an inkjet head and a recording medium improves, and more accurate correction data can be obtained. Advantageous Effects of Invention According to the present invention, it is possible to reduce the visibility of vibration unevenness by image correction using correction data while avoiding an increase in size and / or complexity of an apparatus and / or a control system. Image recording becomes possible.

FIG. 1 is a block diagram schematically illustrating a configuration of an inkjet recording apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of an original image before correction. FIG. 3 is a diagram illustrating an example of an image after correction obtained by shifting the original image in FIG. 2 in the x direction and the y direction. FIG. 4 is a conceptual diagram of the correction processing when four inkjet heads are provided. FIG. 5 is an image example showing a recording result of measurement dots. FIG. 6 is an example of an image obtained by cutting out a band-shaped rectangular area including a dot row of interest and its peripheral pixels from read data of a read image obtained from the image reading apparatus. FIG. 7 is a density cross-sectional profile in the y direction obtained from the read data shown in FIG. FIG. 8 is a graph showing a vibration component in the y direction. FIG. 9 is a graph showing the vibration component in the x direction calculated based on the dot position information obtained in FIG. FIG. 10 is a perspective view showing an example of the ink jet head. FIG. 11 is a plan view of the nozzle surface of the head module viewed from the ejection side. FIG. 12 is a plan perspective view schematically showing an example of the internal flow channel structure in the head module. FIG. 13 is a longitudinal sectional view schematically showing a three-dimensional structure of the ejector. FIG. 14 is an explanatory diagram illustrating recording example 1 of the measurement dot row. FIG. 15 is an explanatory diagram showing recording example 2 of the measurement dot row. FIG. 16 is a flowchart illustrating an example of a procedure for creating correction data. FIG. 17 is a flowchart illustrating an example of an image recording method for performing image correction using correction data. FIG. 18 is a side view showing Configuration Example 1 of the inkjet recording apparatus. FIG. 19 is a block diagram illustrating a schematic configuration of a control system of the inkjet recording apparatus. FIG. 20 is a diagram illustrating another configuration example of the inkjet recording apparatus.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< Overview of First Embodiment >>
FIG. 1 is a block diagram schematically illustrating a configuration of an inkjet recording apparatus according to an embodiment of the present invention. The inkjet recording apparatus 10 is a single-pass inkjet printing system. The ink jet recording apparatus 10 includes a printing press main body 12 and a control device 14. The printing press main body 12 includes a transport unit 22 that transports the recording medium 20, a head unit 24, an image reading device 26, and a discharge unit 28. The term printing machine is synonymous with a printer, an image recording device, an image forming device, a drawing device, or the like.

  The head unit 24 includes at least one inkjet head as a full-line type recording head. For example, the head unit 24 may be configured to include a plurality of inkjet heads corresponding to inks of cyan (C), magenta (M), yellow (Y), and black (K). The head unit 24 records an image on the recording medium 20 by ejecting ink onto the recording surface of the recording medium 20 transported by the transport unit 22. In this specification, the term “ink-jet head” or “recording head” may be simply referred to as “head”.

  The transport direction of the recording medium 20 by the transport unit 22 is referred to as a “media transport direction”, and the width direction of the recording medium 20 perpendicular to the medium transport direction is referred to as a “media width direction”. In this specification, the medium width direction is called an x direction, and the medium transport direction is called a y direction. The x direction corresponds to the line direction in the line type recording head, that is, the nozzle arrangement direction. The x direction is an example of a “second direction”. The y direction is an example of a “first direction”.

  The image reading device 26 includes an image sensor that reads an image recorded on the recording medium 20 and converts an optical image into an electronic image signal. The image sensor may be a line sensor or an area sensor. The image reading device 26 is, for example, a scanner that is arranged on a transport path of the recording medium 20 in a section from the head unit 24 to the discharge unit 28.

  The discharge unit 28 discharges the recording medium 20 on which the image has been recorded to the outside of the apparatus. The discharge unit 28 includes an unillustrated accumulating device that accumulates the recording medium 20 on which an image is recorded.

  The control device 14 generates a print control signal from the image data 30 input as a print target, and controls the operation of the printer body 12. The control device 14 includes an image data acquisition unit 32, a dot data creation unit 34, a drawing control unit 36, and a correction data storage unit 38. The control device 14 is an example of a “recording control device”.

  The image data acquisition unit 32 is an interface that captures the image data 30 to be printed. The image data acquisition unit 32 includes, for example, a communication network terminal provided in the control device 14, a signal input terminal of a signal processing circuit included in the control device 14, a media interface terminal for an external storage medium, or a connection for an external device. A terminal or an appropriate combination of these may be used.

  The dot data creation unit 34 is an image processing unit that creates dot data from the input image data 30. The dot data creation unit 34 includes a correction processing unit 35. The correction processing unit 35 performs an image correction process using the correction data stored in the correction data storage unit 38. The dot data creation unit 34 may include a color conversion processing unit, a color separation processing unit, and a halftone processing unit (not shown), in addition to the correction processing unit 35. The color conversion processing unit performs, for example, a process of converting RGB image data having red (R), green (G), and blue (B) signal components into CMYK image data. The color separation processing unit performs a process of separating the image data for each color of the ink used in the head unit 24. The color separation processing unit performs, for example, a process of performing color separation into C, M, Y, and K images for each ink color. The color separation processing is synonymous with the color separation processing for creating image data of each color plane. When the image data 30 input to the image data acquisition unit 32 is image data that has been subjected to color separation processing, the color conversion processing and the color separation processing can be omitted.

  The drawing control unit 36 controls the ink ejection operation of each nozzle in the inkjet head based on the dot data created by the dot data creation unit 34. The operation of recording dots on the recording medium 20 by discharging ink from the nozzles is referred to as “dropping”. “Dropping” includes the concepts of ink ejection and dot recording. The drawing control unit 36 controls the ink ejection operation in accordance with the conveyance of the recording medium 20.

  In consideration of the reproducibility of the relative speed fluctuation between the ink jet head mounted on the head unit 24 and the recording medium 20, the ink jet recording apparatus 10 previously sets the relative displacement between the ink jet head and the recording medium 20 in each of the x and y directions. Is generated in numerical form, and stored in the correction data storage unit 38. Then, the input image data to be printed is corrected using the correction data, and the ink ejection operation of the inkjet head is controlled based on the corrected image data, thereby printing an image on the recording medium 20. .

  The drawing control unit 36 is an example of a “second control unit”. The function in which the control device 14 controls the ink ejection operation of the ink head based on the corrected image data is an example of a “second control function”.

  As an example of the correction processing performed by the correction processing unit 35, for example, the nozzle number responsible for the ejection of a certain pixel is shifted in accordance with the amount of displacement in the x direction and the amount of displacement in the y direction. The function of the correction processing unit 35 correcting the image data using the correction data is an example of the “correction processing function”.

  A specific example of the correction processing will be described with reference to FIGS. FIG. 2 is an example of an original image before correction. Each cell shown in FIG. 2 represents a pixel, and FIG. 2 shows an image area of 9 rows and 9 columns. FIG. 3 is an example of the corrected image obtained by shifting the original image of FIG. 2 in the x direction and the y direction. FIG. 3 shows an image in which the nozzle numbers are shifted by a correction amount of “+2 pixels” in the x direction and “+1 pixel” in the y direction. Note that shifting the nozzle number is referred to as “nozzle shift”.

  For example, if the landing position deviates by 0.5 pixel or more from a design ideal position (ideal landing position) due to reproducible relative speed fluctuation (position deviation occurs), the nozzle number is shifted. It shall be. Note that the threshold value of “0.5 pixel” is an example, and may be appropriately changed by a correction algorithm applied to the correction processing unit 35.

  The correction process may be performed at any timing before the halftone process, after the halftone process, before the color separation process, or after the color separation process.

  In the case of a configuration including a plurality of inkjet heads, correction data for each inkjet head is created. The “configuration including a plurality of inkjet heads” is not limited to an aspect including different inkjet heads for each color of ink, but may include an aspect including two or more inkjet heads that eject ink of the same color.

  FIG. 4 is a conceptual diagram of a correction process when four inkjet heads corresponding to each color of CMYK are provided. As shown in FIG. 4, input data for each color is created by color separation of input image data. Correction data is stored for each color corresponding to the inkjet head of each color of CMYK.

  The correction processing unit 35 performs a process (correction calculation) of correcting input data using correction data for each color, and creates output data of each color. The ink jet operation of each color is controlled based on the output data of each color created by the correction operation.

<< Example of how to create correction data >>
The correction data is such that dots are ejected from the same nozzle at regular time intervals on the recording medium 20, a print image including a dot row as a result of the ejection is read by the image reading device 26, and each dot is read from the read data. Is created by digitizing the amount of displacement in each of the x and y directions.

  Nozzles used for ejecting dots for measuring positional deviation are referred to as “measuring nozzles”. The measurement nozzle is a plurality of nozzles, and the position deviation values of a plurality of dots ejected at the same moment are averaged to reduce noise. When calculating the correction data, for example, the position of the center of the head is calculated from the positional deviation values measured using the measurement nozzles at the left, right, front and rear ends (near four corners) in the two-dimensional nozzle array of the inkjet head. The deviation value may be calculated by extrapolation. The “head center portion” here is an example of a nozzle area where no measurement dot is ejected.

  As shown in FIG. 1, the control device 14 includes a measurement nozzle setting unit 40 and a correction data creation unit 42 as means for creating the correction data.

  The measurement nozzle setting unit 40 performs a process of setting a measurement nozzle from the nozzle arrangement of the inkjet head. The measurement nozzle may be determined in advance according to a program, or may be set according to an input from a user interface (not shown). The measurement nozzle setting unit 40 may set the nozzle number of the measurement nozzle, or may create dot data representing an image of a dot row for position shift measurement. The dots for measuring the positional deviation that are ejected using the measurement nozzle are referred to as “measurement dots”.

  The drawing control unit 36 controls the ink ejection operation of the inkjet head according to the data from the measurement nozzle setting unit 40, and records the measurement dots on the recording medium 20. The combination of the measurement nozzle setting unit 40 and the drawing control unit 36 is an example of a “first control unit”. That is, the drawing control unit 36 has a function as a “first control unit” and a function as a “second control unit”. The function of controlling the control device 14 to record the measurement dots on the recording medium 20 using the plurality of measurement nozzles is an example of a “first control function”.

  The correction data creation unit 42 includes a read data acquisition unit 44, a read data storage unit 45, and a correction data calculation processing unit 46. The read data acquisition unit 44 is an interface that takes in read data from the image reading device 26. The read data acquisition unit 44 may be, for example, a communication network terminal or a signal input terminal.

  The read data storage unit 45 stores read data indicating a read image captured from the image reading device 26.

  The correction data calculation processing unit 46 includes a dot position measurement unit 47. The dot position measuring section 47 analyzes the read data and measures the dot position. The correction data calculation processing unit 46 creates correction data by digitizing the amount of dot displacement in each of the x and y directions based on the information on the measured dot positions. When creating the correction data, the average value of the positional deviation values of the dots ejected from the plurality of measurement nozzles at the same moment is calculated, and this average value is used as the relative positional deviation value between the inkjet head and the recording medium. . “Same moment” is synonymous with “same timing”.

  The correction data created by the correction data arithmetic processing unit 46 is stored in the correction data storage unit 38. The correction data storage unit 38 is an example of a “storage unit”.

  The correction data storage unit 38 and the read data storage unit 45 may be storage devices exemplified by a semiconductor memory, a hard disk drive, a solid state drive, an optical disk, or the like, or may be an appropriate combination thereof. The correction data storage unit 38 and the read data storage unit 45 may be internal storage devices built in the control device 14 or external storage devices connected to the control device 14.

  FIG. 5 is an image example showing a recording result of measurement dots. In FIG. 5, the horizontal direction is the y direction, and the vertical direction is the x direction. FIG. 5 shows a row of dots ejected at the same timing (simultaneously) at a constant time interval using five nozzles. A dot row of measurement dots ejected from the same nozzle at regular time intervals is referred to as a “measurement dot row”.

  In FIG. 5, the leftmost (leading) dot in each dot row for measurement is the dot that is first ejected. The position of the leftmost dot in each measurement dot row is recorded at a different position in the y direction because the nozzle arrangement in the inkjet head is a two-dimensional nozzle arrangement (see FIG. 11). ), Reflecting the physical arrangement of the measurement nozzles.

  The time interval of the droplet ejection when recording the measurement dot row may be any time interval in which each measurement dot is isolated and ejected, and is appropriately set in accordance with the transport speed by the transport unit 22 and the recording resolution. Is done. In the example shown in FIG. 5, droplet ejection is performed at a time interval corresponding to a pixel cycle of 1 on 3 off for a pixel row along the y direction. “On” means dot-on, that is, recording (dropping) a dot. “Off” means dot off, that is, no recording (dropping) of dots. In the example of FIG. 5, the dots continue to be printed in the right direction of FIG. 5 as time passes. In FIG. 5, the direction in which dot recording progresses over time (rightward direction) is referred to as a printing direction. In the case of the single pass system, the printing direction is opposite to the medium transport direction.

  Focusing on one nozzle in the inkjet head, if there is no relative speed fluctuation between the head and the recording medium in the x direction and the y direction, the x direction position and the y direction of each dot of the dot row ejected using this one nozzle The positions are ideal positions in design, and are essentially constant intervals. On the other hand, when a relative speed fluctuation occurs between the head and the recording medium, it is observed as a deviation in the x-direction position and / or a deviation in the y-direction position (fluctuation in interval) of each dot. In the present embodiment, the position shift value of each dot in the measurement dot row is measured, and information on the relative speed fluctuation between the head and the recording medium is obtained to generate correction data.

  FIG. 6 shows an example of read data of a dot row in a range surrounded by an ellipse in FIG. FIG. 6 is a cutout of a band-shaped rectangular area including a dot row of interest and its surrounding pixels from read data of a read image obtained from the image reading device 26. The rectangular area includes a dot row of interest as a calculation target, and has a certain pixel range in the x direction. The numbers “10”, “20”, and “30” on the vertical scale shown in FIG. 6 represent the positions of the pixels in the x direction on the read data, and the numbers “100” to “500” on the horizontal scale. Represents the position of the pixel in the y direction. Note that the pixel position in the read data can be converted to the recording position of the inkjet recording device 10. Here, an example is shown in which a recording dot recorded on a white recording medium 20 using black ink is read by the image reading device 26, and a rectangular area is cut out from the read image.

  FIG. 7 is a density cross-sectional profile in the y direction obtained from the read data shown in FIG. The horizontal axis in FIG. 7 represents a pixel position in the y direction, and the vertical axis represents a pixel value. The pixel value is a signal value indicating the brightness of the read image, and is represented by a gradation from 0 to 255. The maximum value 255 represents “white”, and the lower value represents the density of dots (black). Pixel values can vary from 0 to 255.

  The graph shown in FIG. 7 is obtained by integrating the pixel values of each pixel in the rectangular area shown in FIG. 6 in the x direction to calculate an average value. Looking at the density cross section in the x direction at each Y position in the rectangular area shown in FIG. 6, it is converted from white to black to white, and the average value of the density cross section profile (that is, the average value in the x direction) was obtained. This is the graph of FIG.

  Here, first, it is considered to measure the displacement in the y direction. Therefore, when the average value of the pixel values of the pixels arranged in the x direction in the rectangular area is calculated and the change is observed in the y direction, peaks and valleys are seen as shown in the graph of FIG. The “valley” (black vertex) in the graph of FIG. 7 corresponds to a “dot”. That is, in the graph of FIG. 7, the Y position having the minimum value corresponds to the dot position in the y direction.

  In FIG. 7, black dots are displayed at positions corresponding to “dots”. Although the interval between these black points in the y direction (dot interval in the y direction) should be essentially constant, the dot interval in the y direction can actually fluctuate due to the relative speed fluctuation between the head and the recording medium.

  The dot position in the y direction can be specified from a graph as shown in FIG. FIG. 8 is a graph showing a vibration component in the y direction. The horizontal axis represents the distance in the y direction, and the vertical axis represents the displacement in the y direction. The graph shown in FIG. 8 can be calculated by calculating the difference between the dot position in the y direction of each dot obtained in FIG. 7 and the ideal dot position in the y direction.

  When the position of the dot in the y direction is specified, a graph having the same profile as that of FIG. 7 is created in the x direction, and the dot position in the x direction is specified.

  For example, when the y-direction dot position is y = 90, the x-direction dot position is specified from the x-direction density fluctuation at the y = 90 position in the rectangular area in FIG.

  That is, a density cross-sectional profile in the x direction is created at the Y position of each black point in the graph shown in FIG. 7, and the x position of the valley is specified as a dot position in the x direction. Then, by calculating the difference between the dot position of each dot in the x direction and the ideal dot position in the x direction, a position shift value in the x direction can be obtained.

  FIG. 9 is a graph showing the vibration component in the x direction calculated based on the dot position information obtained in FIG. The graph shown in FIG. 9 can be calculated by calculating the difference between the dot position of each dot in the x direction and the ideal dot position in the x direction.

<Other methods for specifying dot positions>
The method of specifying the dot position described with reference to FIG. 7 is an example, and the method of specifying the position of each dot is not limited to this example. For example, it is also possible to apply an algorithm of extracting a circular (dot) region from a read image using image recognition processing and calculating the coordinates (center position) of the extracted circular by calculation.

<Reason for using information of dots ejected at the same moment from multiple measurement nozzles>
In the present embodiment, the relative position shift value between the inkjet head and the recording medium is calculated by averaging the calculation results of the position shift values of dots ejected at the same moment from a plurality of measurement nozzles.

  If the relative position deviation value between the ink jet head and the recording medium is obtained without using the dots ejected at the same moment, the calculation accuracy of the relative position deviation value decreases or the calculation algorithm becomes complicated.

  In this regard, by averaging the positional deviation values of a plurality of dots ejected at the same moment as in the present embodiment, the influence of noise such as a measurement error of the dot position is reduced, and the relative position of the inkjet head and the recording medium is reduced. The accuracy of calculating the deviation value is improved.

<< Reproducibility cycle of relative speed fluctuation >>
5 to 9 illustrate an example in which the measurement of the dot position and the calculation of the position shift value for a part of the measurement dot row are performed, but actually, the correction data for one cycle of the relative vibration with reproducibility is obtained. Create

  For example, when the vibration of the relative speed fluctuation is reproduced in a cycle synchronized with one rotation of the drum or other rotating member used in the transport unit 22, x of one rotation cycle, that is, one rotation of the rotating member is used. The pattern of the positional deviation in the direction and the pattern of the positional deviation in the y direction are stored in advance as correction data, and image correction is performed using these correction data.

  As described above, when the relative speed fluctuation is reproduced in a constant repetition pattern, and the cycle of the repetition pattern is periodicity derived from the physical structure of the transport system, the length of the cycle of the transport system is equal to the length of the transport system. It is preferable to hold correction data only and perform image correction in synchronization with the reference position of the transport system. The transport unit 22 is provided with a detector (not shown) for detecting a reference position (a starting point) and generating a synchronization signal.

  For example, in a configuration in which a drum conveyance method is applied to the conveyance unit 22 of the inkjet recording apparatus 10 and the medium is conveyed at the time of printing by adsorbing and holding the sheet-like recording medium 20 on the drawing drum facing the head unit 24, If two recording media 20 can be conveyed for one rotation, correction data is created using two recording media 20 as one cycle with reproducible relative speed fluctuation (vibration).

  That is, the correction data collectively holds correction data for two sheets of the recording medium 20 corresponding to one rotation of the drawing drum, and applies the first half of the correction data to image correction of the first sheet. The second half is applied to the second image correction.

  Therefore, it is necessary that the recording of the measurement dot row at the time of creating the correction data and the acquisition of the measurement data by reading the dot row be at least one cycle of the vibration. For this reason, when creating the correction data, it is necessary to first take the data sufficiently longer than one cycle, check the periodicity of the vibration, and then create the correction data for one cycle. preferable.

  When the relative speed change in the x direction and the relative speed change in the y direction are not linked to each other and have different periodicities, the start point of the cycle of the relative speed change in the x direction in the inkjet recording apparatus 10. And a detector that detects the starting point of the cycle of the relative speed fluctuation in the y direction are separately provided.

<< Configuration example of inkjet head >>
Next, an example of an ink jet head used in the head unit 24 will be described.

  FIG. 10 is a perspective view of the inkjet head 50. FIG. 10 illustrates a state in which the nozzle surface is looked up from an obliquely downward direction of the inkjet head 50. The ink-jet head 50 is a full-line type recording head in which a plurality of head modules 52 are connected and elongated in the line direction. The full line type print head is also called a page wide head. The bar-shaped inkjet head illustrated in FIG. 10 may be called an inkjet head bar.

  FIG. 10 shows an example in which 17 head modules 52 are connected to form an inkjet head bar. However, the structure of the head modules 52 and the number and arrangement of the head modules 52 are not limited to the illustrated example. Reference numeral 54 in the figure denotes a base frame that serves as a frame for connecting and fixing the plurality of head modules 52 in a bar shape. Reference numeral 56 denotes a flexible board connected to each head module 52. The plurality of head modules 52 are attached to and integrated with the base frame 54 to form one inkjet head bar.

  FIG. 11 is a plan view of the nozzle surface 52A of the head module 52 as viewed from the ejection side. Although FIG. 11 shows the number of nozzles reduced for convenience of illustration, 32 × 64 nozzles 60 are two-dimensionally arranged on the nozzle surface 52A of one head module 52, for example. The nozzle arrangement of the plurality of nozzles 60 arranged two-dimensionally is referred to as “two-dimensional nozzle arrangement”.

  The head module 52 has an end face on the long side along the V direction having an inclination of an angle γ with respect to the x direction, and an end face on a short side along the W direction with an inclination of an angle α with respect to the y direction. And has a parallelogram shape in plan view.

  By connecting a plurality of such head modules 52 in the x-direction (see FIG. 11), a nozzle row covering the entire drawing range of the recording medium 20 in the x-direction is formed, and the prescribed printing is performed by one drawing scan. A line head capable of recording an image at a resolution is configured. The prescribed recording resolution may be a recording resolution predetermined by the inkjet recording apparatus, or may be a recording resolution set by a user's selection or automatically selected by a program corresponding to a print mode. Good. The recording resolution can be, for example, 1200 dpi. dpi (dot per inch) is a unit notation representing the number of dots per inch.

  In the case of an inkjet head having a two-dimensional nozzle array, a projection nozzle array that projects (orthogonally projects) each nozzle in the two-dimensional nozzle array so as to be arranged in the x direction is a nozzle that achieves the maximum recording resolution in the x direction. It can be considered as equivalent to a single nozzle row in which the nozzles are arranged at substantially equal intervals in density. The term “substantially equal intervals” means that droplets are recordable at ink jet recording apparatuses at substantially equal intervals. For example, the concept of "equal intervals" includes a case in which the intervals are slightly different in consideration of manufacturing errors and the movement of liquid droplets on the recording medium due to landing interference. In consideration of a projection nozzle row (also referred to as a “substantial nozzle row”), a nozzle number representing a nozzle position can be associated with the arrangement order of projection nozzles arranged along the x direction.

  In order to realize high recording resolution, it is necessary to narrow the substantial nozzle spacing of the nozzle rows, and a matrix-shaped nozzle array having a plurality of nozzle rows of three or more rows in the y direction is employed. It is desirable.

  The arrangement of the nozzles 60 in the head module 52 is not limited to the illustrated example, and various nozzle arrangements can be adopted. For example, instead of the matrix arrangement described with reference to FIG. 11, a linear nozzle arrangement in one row, a V-shaped nozzle arrangement, a broken line nozzle arrangement such as a W-shaped arrangement having a V-shaped arrangement as a repeating unit, and the like. Is also possible.

  The operation of moving the recording medium 20 relatively to the inkjet head 50 (see FIG. 1) formed by combining a plurality of head modules 52 having such a nozzle arrangement is performed only once, that is, once in the y direction. The image having the prescribed recording resolution can be recorded in the image forming area of the recording medium 20 by the drawing scan. A drawing method capable of completing an image by one drawing scan is called a single-pass method.

  FIG. 12 is a perspective plan view schematically showing an example of the internal flow channel structure in the head module 52. Here, for convenience of illustration, an example of the arrangement of the ejectors 62 corresponding to each of the 12 nozzles 60 that are a part of the nozzle group in the head module 52 is shown. Note that the vertical direction in FIG. 12 corresponds to the W direction shown in FIG. 11, and the horizontal direction in FIG. 12 corresponds to the V direction.

  Inside the head module 52, a supply-side common main flow path 70 as an ink supply path for supplying ink to each ejector 62, a plurality of supply-side common branch flow paths 72 connected to the supply-side common main flow path 70, , Are provided. The supply-side common branch channel 72 is a branch channel branched from the supply-side common main channel 70. The supply-side common branch channel 72 is provided for each nozzle row along the W direction. A plurality of nozzles 60 are connected to each of the supply-side common branch channels 72. The supply-side common main flow path 70 is connected to an ink tank (not shown) via a supply connection port (not shown).

  The supply-side common branch channel 72 is an example of a “branch channel”. The supply-side common main flow path 70 to which the plurality of supply-side common branch flow paths 72 are connected is an example of a “main flow path”. An ink supply path having a flow path structure including the supply-side common main flow path 70 and the plurality of supply-side common branch flow paths 72 is an example of an “ink flow path”.

  Further, inside the head module 52, a collection-side common main flow path 80 as an ink collection path for collecting ink from the nozzle flow path of each ejector 62, and a plurality of collection sides connected to the collection-side common main flow path 80. And a side common branch channel 82. The collecting-side common branch channel 82 is a branch channel that merges with the collecting-side common main channel 80. The collection-side common branch flow path 82 is provided for each nozzle row along the W direction. A plurality of nozzles 60 are connected to each of the recovery-side common branch channels 82. The recovery-side common main channel 80 is connected to a recovery tank (not shown) via a recovery connection port (not shown). The ink collected in the collection tank may be sent to the supply-side channel again to circulate the ink.

  The recovery-side common branch channel 82 is an example of a “branch channel”. The collecting-side common main channel 80 to which the plurality of collecting-side common branch channels 82 are connected is an example of a “main channel”. An ink recovery path having a flow path structure including the recovery-side common main flow path 80 and a plurality of recovery-side common branch flow paths 82 is an example of an “ink flow path”.

  FIG. 13 is a longitudinal sectional view schematically showing the three-dimensional structure of the ejector 62. The ejector 62 includes a nozzle 60, a pressure chamber 90 communicating with the nozzle 60, and a piezoelectric element 92. The nozzle 60 communicates with the pressure chamber 90 via the nozzle channel 64. The pressure chamber 90 communicates with the supply-side common branch flow path 72 via the individual supply path 74.

  Further, an individual recovery path 84 is connected to the nozzle flow path 64. The nozzle flow path 64 is connected to the recovery-side common branch flow path 82 via the individual recovery path 84.

  The vibration plate 94 forming the top surface of the pressure chamber 90 has a conductive layer (not shown) functioning as a common electrode corresponding to the lower electrode of the piezoelectric element 92. The wall of the pressure chamber 90 and other flow path portions, the diaphragm 94, and the like can be made of silicon. The material of the vibration plate 94 is not limited to silicon, and an embodiment in which the vibration plate 94 is formed of a non-conductive material such as a resin is also possible. A conductive layer made of a conductive material is formed on the surface of the diaphragm member. The vibration plate 94 itself may be made of a metal material such as stainless steel, and may be a vibration plate also serving as a common electrode.

  A structure in which the piezoelectric element 92 is stacked on the vibration plate 94 constitutes a piezoelectric unimorph actuator. The piezoelectric body 98 is deformed by applying a drive voltage to the individual electrode 96 which is the upper electrode of the piezoelectric element 92, and the volume of the pressure chamber 90 is changed by bending the vibration plate 94. The ink is ejected from the nozzle 60 by the pressure change accompanying the volume change. When the piezoelectric element 92 returns to the original state after the ink is ejected, the pressure chamber 90 is filled with new ink from the supply side common branch channel 72 through the individual supply path 74. The operation of filling the pressure chamber 90 with ink is called “refill”. In this example, a configuration is described in which the diaphragm 94 is bent by using the distortion deformation of the piezoelectric body 98 in the d31 mode. However, the ejection is performed by using the mode using the d33 mode or the shear mode (shear deformation). Forms are also possible.

  Reference numeral 66 in FIG. 13 denotes a cover plate. The cover plate 66 is a member that secures the movable space 68 for the piezoelectric element 92 and seals the periphery of the piezoelectric element 92.

  In FIG. 13, a supply-side ink chamber (not shown) and a collection-side ink chamber (not shown) are formed above the cover plate 66. The supply-side ink chamber is connected to a supply-side common main flow path 70 (see FIG. 12) via a communication path (not shown). The collection-side ink chamber is connected to a collection-side common main channel 80 (see FIG. 12) via a communication path (not shown).

  The ink supplied from the supply-side common branch channel 72 to the pressure chamber 90 via the individual supply channel 74 is discharged from the nozzle 60 through the nozzle channel 64. In addition, ink not used for discharge is collected from the nozzle flow path 64 to the recovery-side common branch flow path 82 via the individual recovery path 84.

《Setting example of measurement nozzle》
Multiple nozzles for recording dots at the same moment in order to record a dot row for positional deviation measurement have different branch channels to prevent landing position deviation due to crosstalk in the head flow path. Use the one connected to.

  For example, in FIG. 12, three nozzles 60 surrounded by a broken line circle are each connected to a separate supply-side common branch channel 72, and each are connected to a separate recovery-side common branch channel 82. It can be a plurality of measurement nozzles that drop measurement dots instantaneously.

  The nozzles 60 belonging to different head modules 52 satisfy the condition that each is connected to a different branch channel.

  12 and 13, the head structure having the ink recovery path for recovering the ink from the nozzle flow path 64 has been described. However, an inkjet head having no ink recovery path may be employed.

  In addition, a plurality of measurement nozzles that perform droplet ejection at the same moment may belong to the same head module or may belong to different head modules, and a plurality of nozzles belonging to the same head module and a different head module It may be a combination with a plurality of nozzles.

  For the purpose of accurately calculating the relative position shift value between the inkjet head and the recording medium, the plurality of measurement nozzles are preferably set to be distributed over a wide range of the nozzle area of the inkjet head. For example, the plurality of measurement nozzles are set including two nozzles arranged near both ends in the x direction in the two-dimensional nozzle array of the inkjet head. In addition, for example, the plurality of measurement nozzles are set including nozzles arranged near the center in the x direction in the two-dimensional nozzle array of the inkjet head.

《Recording example of dot row for misalignment measurement》
The measurement dot row recorded to create the correction data may be recorded on a recording medium different from the recording medium that records the image of the image data according to the print designation (see FIG. 14), or may be printed. The image may be recorded in an area outside the image area on the same recording medium as the recording medium on which the image of the designated image data is recorded, for example, in a margin area adjacent to the image area in the x direction (see FIG. 15).

  FIG. 14 is an explanatory diagram illustrating recording example 1 of the measurement dot row. As shown in FIG. 14, when a single-sheet recording medium is used, a plurality of measurement dot arrays 41 are recorded on a recording medium 20B on a separate sheet from the recording medium 20A for recording an image of image data according to print designation. can do.

  The recording example 1 shown in FIG. 14 can also be applied to a continuous medium. When a continuous medium is used, the measurement dot row 41 can be recorded in a recording area where the position in the y direction is different from the recording area where the image of the image data relating to the print designation is recorded.

  FIG. 15 is an explanatory diagram showing recording example 2 of the measurement dot row. As shown in FIG. 15, when a single-sheet recording medium is used, measurement dots are formed in a blank area 21B outside the image area 21A on the same recording medium 20A as the recording medium 20A on which the image of the image data according to the print designation is printed. Column 41 can be recorded.

  The recording example 2 shown in FIG. 15 can also be applied to a continuous medium. When a continuous medium is used, the measurement dot row 41 can be recorded in a blank area outside the image area in the recording area at the same y-direction position as the recording area for recording the image of the image data according to the print designation.

  Further, in the case of the recording example 2 shown in FIG. 15, even when the relative speed fluctuation between the head and the recording medium changes over time, the image correction can be followed. For example, when N is an integer of 2 or more, it is possible to correct the image of the printed matter to be printed on the Nth day using the printed matter printed on the (N-1) th day. Further, by using the printed matter printed on the (N-1) th sheet, it is possible to correct the image of the printed matter printed on the Nth sheet.

<< Example of how to create correction data >>
FIG. 16 is a flowchart illustrating an example of a procedure for creating correction data. Each step of the flowchart shown in FIG. 16 is executed in accordance with a command from the control device 14.

  In step S12, the ink jet recording apparatus 10 performs droplet ejection simultaneously and at regular time intervals from a plurality of measurement nozzles connected to different branch channels, and records a measurement dot row. Step S12 is an example of “a step of recording a plurality of measurement dot arrays on a recording medium”.

  The correction data is preferably data that covers at least one cycle of the reproducible relative speed fluctuation. Therefore, it is preferable that the dot row for measurement is continuously recorded over a period of time exceeding one cycle of the reproducible relative speed fluctuation. One cycle of the relative speed fluctuation corresponds to, for example, one rotation of the rotating member employed in the transport unit 22.

  In order to further increase the calculation accuracy of the correction data, two or more cycles of relative speed fluctuation with reproducibility, continuous droplet ejection for a plurality of cycles, and measurement of dots for a plurality of cycles are performed. It is more preferable to take measures such as averaging the measurement results.

  In step S <b> 14, the inkjet recording device 10 reads the recording result of the dot row for measurement by the image reading device 26. The image reading device 26 creates read data as electronic image data of a read image including a dot row for measurement recorded on the recording medium 20. Step S <b> 14 is an example of “a step of reading a plurality of measurement dot rows recorded on a recording medium using an image reading device”.

  In step S16, the read data acquisition unit 44 acquires the read data of the measurement dot row from the image reading device 26. The acquired read data is stored in the read data storage unit 45.

  In step S18, the dot position measuring unit 47 measures the dot position by analyzing the acquired read data. The dot position measuring unit 47 specifies the x-direction position and the y-direction position of each dot by, for example, the method described with reference to FIGS. The method of specifying the dot position is not limited to this method. For example, a circular dot may be recognized from a read image by image recognition processing, and the center position of each dot may be obtained by calculation.

  In step S20, the correction data calculation processing unit 46 calculates a position shift value representing the amount and direction of the shift of each dot with respect to the ideal dot position from the measured dot position. The position shift value indicates the amount of dot position shift by a numerical value, and indicates the direction of the shift by a sign of “plus” or “minus”. Steps S18 and S20 are an example of “the step of calculating the positional deviation value of the dots included in the measurement dot row”.

  In step S22, the correction data calculation processing unit 46 calculates the average value of the positional deviation values of the dots ejected from the plurality of measurement nozzles at the same moment, and indicates the relative positional deviation value between the inkjet head and the recording medium. Calculate the correction data.

  The plurality of measurement dot rows are dot rows ejected at the same moment, and each measurement dot row carries the same vibration component. On the other hand, since the spatial arrangement of the nozzles in the ink jet head is fixed, the image for suppressing the vibration unevenness is based on the information on the relative speed fluctuation (vibration) with respect to time and the arrangement information of the nozzles in the head. Correction is possible.

  If the correction data is created from only one measurement dot row ejected using only one nozzle, the reading error when scanning the measurement dot row is affected.

  In the present embodiment, correction data is created by averaging data obtained from reading results of a plurality of measurement dot rows that are ejected at the same moment using a plurality of measurement nozzles. Thereby, the influence of a reading error or the like can be reduced.

  Since a plurality of measurement dot rows recorded at the same moment using a plurality of measurement nozzles have their leading dot positions shifted in the y direction, the data obtained from the plurality of measurement dot rows are averaged. In (2), the first dot position in each measurement dot row is aligned in the y direction (data is shifted in the y direction so that the first dot positions coincide with each other), and then the average value is calculated. By such averaging, it is possible to grasp in what pattern the relative position between the head and the recording medium varies with time.

  In step S22, the correction data calculation processing unit 46 uses the positional deviation values of the measurement dots recorded using the plurality of measurement nozzles, and calculates the positional deviation in the nozzle area where the measurement dots are not ejected. The value may be calculated by extrapolation (extrapolation method) to create correction data.

  In step S26, the control device 14 stores the correction data created by the correction data calculation processing unit 46 in the correction data storage unit 38.

  The correction data creation processing shown in FIG. 16 may be performed at an appropriate timing. For example, the correction data creation process may be performed in a manufacturing factory before shipping the inkjet recording device 10. Further, the correction data creation processing may be performed in a printing factory where the inkjet recording device 10 is installed, and the correction data may be updated as needed.

<< Example of image recording method >>
FIG. 17 is a flowchart illustrating an example of an image recording method for performing image correction using correction data. Each step of the flowchart shown in FIG. 16 is executed in accordance with a command from the control device 14.

  In step S32, the control device 14 acquires image data designated as a print target.

  In step S34, the correction processing unit 35 reads correction data stored in advance in the correction data storage unit 38.

  In step S36, the correction processing unit 35 performs a correction operation using the correction data, and creates corrected image data. The nozzle shift technique described with reference to FIGS. 2 and 3 can be applied to the correction calculation.

  In step S38, the control device 14 controls the ink ejection operation of the inkjet head according to the corrected image data and executes image recording.

<< Configuration Example 1 of Inkjet Recording Apparatus >>
FIG. 18 is a side view showing Configuration Example 1 of the inkjet recording apparatus. An ink jet recording apparatus 201 shown in FIG. 6 is one specific example of the ink jet recording apparatus 10 described in FIG. The inkjet recording apparatus 201 is a single-pass type image recording apparatus that forms a color image on a sheet of paper P using a plurality of color inks.

  The ink jet recording apparatus 201 includes a paper feed unit 210, a processing liquid application unit 220, a processing liquid drying unit 230, a drawing unit 240, an ink drying unit 250, and an accumulation unit 260.

  The paper supply unit 210 includes a paper supply device 212, a feeder board 214, and a paper supply drum 216. A bundle of sheets P is placed on a sheet feeding table 212A of the sheet feeding device 212. The type of the paper P is not particularly limited. For example, printing paper mainly composed of cellulose, such as high-quality paper, coated paper, and art paper, can be used. The sheet P is an example of a recording medium on which an image is recorded. The sheet feeding device 212 takes out the sheets P in a bundle set on the sheet feeding table 212A one by one in order from the top and feeds them to the feeder board 214. The feeder board 214 transfers the sheet P received from the sheet feeding device 212 to the sheet feeding drum 216.

  The paper feed drum 216 receives the paper P fed from the feeder board 214 and transfers the received paper P to the processing liquid application unit 220.

  The processing liquid application unit 220 applies the processing liquid to the paper P. The processing liquid is a liquid containing an aggregating agent that aggregates the color material components in the ink used in the drawing unit 240. The coagulant may be a compound that can change the pH (pH) of the ink composition. As the compound capable of lowering the pH, an acidic substance having high water solubility is preferably exemplified. The acidic substance may be used alone or in combination of two or more.

  The treatment liquid application unit 220 includes a treatment liquid application drum 222 and a treatment liquid application device 224. The processing liquid application drum 222 receives the paper P from the paper supply drum 216 and transfers the received paper P to the processing liquid drying unit 230. The processing liquid application drum 222 has a gripper 223 on the drum peripheral surface, and grips and rotates the leading end of the paper P with the gripper 223 to wind and convey the paper P around the peripheral surface.

  The processing liquid application device 224 applies the processing liquid to the paper P transported by the processing liquid application drum 222. The processing liquid application device 224 uniformly applies the processing liquid to the first surface of the sheet P conveyed by the processing liquid application drum 222. The first surface of the paper P corresponds to a recording surface on which an image is recorded by ink ejection. The surface of the sheet P opposite to the first surface is referred to as a second surface.

  The processing liquid application device 224 of this example applies the processing liquid to the paper P by a roller application method. That is, the treatment liquid application device 224 includes an application roller, and applies the treatment liquid to the entire surface of the sheet P by pressing the application roller having the peripheral surface to which the treatment liquid is applied against the recording surface of the sheet P. As the configuration of the treatment liquid coating device 224, for example, the configuration of a coating device described in JP-A-2013-014009 can be adopted. The application method of the treatment liquid application device 224 is not particularly limited, and instead of the roller application method, the treatment liquid is uniformly applied to the recording surface, such as a squeegee application method, a die application method, or a spray method. Other coating methods that can be applied may be adopted.

  The processing liquid drying unit 230 performs a drying process on the paper P to which the processing liquid has been applied. The processing liquid drying unit 230 includes a processing liquid drying drum 232 and a warm air blower 234. The treatment liquid drying drum 232 receives the sheet P from the treatment liquid application drum 222 and transfers the received sheet P to the drawing unit 240. The processing liquid drying drum 232 includes a gripper 233 on a peripheral surface thereof. The treatment liquid drying drum 232 conveys the paper P by gripping and rotating the leading end of the paper P with the gripper 233.

  The hot air blower 234 is disposed inside the processing liquid drying drum 232. The hot air blower 234 blows hot air onto the paper P conveyed by the processing liquid drying drum 232 to dry the processing liquid. As a result, an ink aggregation layer is formed on the first surface of the paper P. The ink aggregation layer refers to a layer of an ink aggregation agent contained in the treatment liquid. The processing liquid drying unit 230 evaporates the water in the processing liquid, and forms an ink aggregation layer, which is a thin layer of the ink aggregation agent of the processing liquid, on the first surface of the paper P.

  The drawing unit 240 includes a drawing drum 242, a head unit 244, and an image reading device 248 that is an inline sensor. The drawing drum 242 receives the paper P from the processing liquid drying drum 232 and transfers the received paper P to the ink drying unit 250. The drawing drum 242 includes a gripper 243 on the drum peripheral surface, and grips and rotates the leading end of the paper P with the gripper 243 to wind and convey the paper P around the peripheral surface. The drawing drum 242 includes a suction mechanism (not shown), and transports the paper P wound on the drum peripheral surface while adsorbing the paper P on the peripheral surface. A negative pressure is used for the adsorption. The drawing drum 242 has a large number of suction holes on the peripheral surface, and sucks the paper P onto the peripheral surface by sucking the inside through the suction holes.

  The head unit 244 includes inkjet heads 246K, 246C, 246M, and 246Y. The inkjet head 246C is a recording head that ejects droplets of cyan (C) ink. The inkjet head 246M is a recording head that ejects magenta (M) ink droplets. The inkjet head 246Y is a recording head that ejects droplets of yellow (Y) ink. The inkjet head 246K is a recording head that ejects black (K) ink droplets.

  Ink is supplied to each of the inkjet heads 246K, 246C, 246M, and 246Y from an ink tank (not shown), which is an ink supply source of a corresponding color, via a piping path (not shown).

  Each of the inkjet heads 246K, 246C, 246M, and 246Y is constituted by a line head corresponding to the paper width, and each nozzle surface is arranged to face the peripheral surface of the drawing drum 242. Here, the sheet width refers to the sheet width in a direction orthogonal to the transport direction of the sheet P. The inkjet heads 46K, 46C, 46M, and 46Y are arranged at regular intervals along the transport path of the paper P by the drawing drum 242, and the inkjet heads 246K, 246C, 246M, and 246Y are orthogonal to the transport direction of the paper P. It is installed to extend in the direction of The direction perpendicular to the transport direction of the paper P is a direction parallel to the rotation axis of the drawing drum 242.

  Each of the inkjet heads 246K, 246C, 246M, and 246Y may be a line head having a structure similar to the structure described with reference to FIGS.

  At least one of the inkjet heads 246K, 246C, 246M, and 246Y ejects ink droplets toward the paper P conveyed by the drawing drum 242, and the ejected droplets adhere to the paper P. The image is recorded on the sheet P.

  The drawing drum 242 functions as means for relatively moving the inkjet heads 246K, 246C, 246M, and 246Y and the paper P. The ejection timing of each of the inkjet heads 246K, 246C, 246M, and 246Y is synchronized with a rotary encoder signal obtained from a rotary encoder (not shown) arranged on the drawing drum 242. The ejection timing is the timing at which ink droplets are ejected, and is synonymous with the ejection timing.

  In this example, the configuration of the standard colors of KCMY (four colors) is illustrated, but the combination of the ink color and the number of colors is not limited to the present embodiment, and the light ink, the dark ink, and the special color may be used as needed. Ink and the like may be added. For example, a configuration in which an inkjet head that ejects light-colored inks such as light cyan and light magenta is added, and / or ink of one or more colors such as orange (O), violet (V), or white (W) is ejected A configuration in which an inkjet head is added is also possible. Further, the arrangement order of the inkjet heads of each color is not particularly limited.

  The image reading device 248 corresponds to the image reading device 26 in FIG. The image reading device 248 reads an image recorded on the sheet P by the inkjet heads 246K, 246C, 246M, and 246Y, and generates electronic image data indicating the read image. The image reading device 248 includes an imaging device that captures an image recorded on the paper P and converts the captured image into an electric signal indicating image information. A color CCD (Charge-Coupled Device) linear image sensor can be used as the imaging device. Note that a color CMOS (Complementary Metal Oxide Semiconductor) linear image sensor can be used instead of the color CCD linear image sensor.

  The image reading device 248 may include, in addition to the imaging device, an illumination optical system that illuminates a reading target and a signal processing circuit that processes signals obtained from the imaging device to generate digital image data. The image reading device 248 reads an image on the sheet P while the drawing drum 242 conveys the sheet P.

  When a sheet P on which an image is recorded using at least one of the inkjet heads 246K, 246C, 246M, and 246Y passes through a reading area of the image reading device 248, the image on the sheet P is read. The images recorded on the paper P include an image to be printed specified by a print job, a dot row for measurement, a defective nozzle detection pattern for inspecting the ejection state of each nozzle, a test pattern for print density correction, The print density unevenness correction test pattern, the dot diameter measurement chart, the ink amount measurement chart, and other various patterns may be included.

  Correction data is created based on the read data obtained from the image reading device 248. Further, a print image is inspected based on the read data obtained from the image reading device 248, and it is determined whether there is an image quality abnormality. In addition, based on read data obtained from the image reading device 248, information such as image density and ejection failure of the inkjet heads 246K, 246C, 246M, and 246Y can be obtained.

  The ink drying unit 250 performs a drying process on the sheet P on which the image is recorded in the drawing unit 240. The ink drying unit 250 includes a chain delivery 251, a paper guide 252, and a hot air blowing unit 253.

  The chain delivery 251 receives the paper P from the drawing drum 242 and transfers the received paper P to the stacking unit 260. The chain delivery 251 includes a pair of endless chains 254 traveling on a prescribed traveling route, and grips the leading end of the sheet P with a gripper 255 provided on the pair of chains 254 to transport the sheet P in a prescribed manner. Convey along the route. A plurality of grippers 255 are provided on the chain 254 at regular intervals.

  The paper guide 252 is a member that guides the conveyance of the paper P by the chain delivery 251. The paper guide 252 includes a first paper guide 252A and a second paper guide 252B. The first paper guide 252A guides the paper P conveyed in the first conveyance section of the chain delivery 251. The second paper guide 252B guides the paper conveyed in the second conveyance section subsequent to the first conveyance section. The hot air blowing unit 253 blows hot air on the paper P conveyed by the chain delivery 251.

  The stacking unit 260 includes a stacking device 262 that receives and stacks the sheets P conveyed from the ink drying unit 250 by the chain delivery 251.

  The chain delivery 251 releases the paper P at a predetermined stacking position. The stacking device 262 includes a stacking tray 262A, receives the sheets P released from the chain delivery 251, and stacks the sheets P on the stacking tray 262A. The stacking unit 260 corresponds to the discharging unit 28 (see FIG. 1).

<< Explanation of control system of inkjet recording device >>
FIG. 19 is a block diagram illustrating a schematic configuration of a control system of the inkjet recording apparatus 201. The inkjet recording apparatus 201 includes a system controller 300. The system controller 300 includes a CPU (Central Processing Unit) 300A, a ROM (Read Only Memory) 300B, and a RAM (Random Access Memory) 300C. The storage units such as the ROM 300B and the RAM 300C may be provided outside the system controller 300.

  The system controller 300 functions as a control device that controls each unit of the inkjet recording apparatus 201 in an integrated manner. Further, the system controller 300 functions as an arithmetic device that performs various arithmetic processes. Further, the system controller 300 functions as a memory controller that controls reading and writing of data in memories such as the ROM 300B and the RAM 300C.

  The ink jet recording apparatus 201 includes a communication unit 302, an image memory 304, an image processing unit 306, a transport control unit 310, a paper feed control unit 312, a processing liquid application control unit 314, a processing liquid drying control unit 316, a drawing control unit 318, an ink A drying control unit 324 and a paper discharge control unit 326 are provided. The components of these components are included in the control device 14 described with reference to FIG.

  Elements of each control unit including the system controller 300 can be configured by a combination of computer hardware and software. In addition, some or all of the processing functions required for control may be realized using an integrated circuit represented by a DSP (Digital Signal Processor) or an FPGA (Field Programmable Gate Array).

  The communication unit 302 includes a communication interface (not shown), and can transmit and receive data to and from the host computer 500 connected to the communication interface.

  The image memory 304 functions as a temporary storage unit for various data including image data. Image data captured from the host computer 500 via the communication unit 302 is temporarily stored in the image memory 304.

  The image processing unit 306 generates dot data from the input image data. The image processing unit 306 includes the dot data creation unit 34 described with reference to FIG. The image processing unit 306 includes a color separation processing unit, a color conversion processing unit, a correction processing unit, and a halftone processing unit. The image processing unit 306 performs color separation processing for separating input image data into RGB colors, color conversion processing for converting RGB data into CMYK data, various correction processing such as gamma correction, unevenness correction, and the like. A halftone process is performed to convert each of the grayscale values into a grayscale value smaller than the original grayscale value. The correction processing performed by the image processing unit 306 includes, in addition to the image correction processing for suppressing the vibration unevenness, a defect correction processing for suppressing an image defect caused by a defective nozzle.

  The input image data is continuous tone image data. As an example of input image data, raster data represented by digital values from 0 to 255 can be given. The dot data obtained as a result of the halftone processing may be binary, or may be multivalued having three or more values and less than the gradation value before the halftone processing. Some or all of the processing functions of the image processing unit 306 may be included in the system controller 300 or the drawing control unit 318. The drawing control unit 318 corresponds to the drawing control unit 36 described with reference to FIG.

  The transport control unit 310 controls the operation of the transport system 211 of the paper P in the inkjet recording apparatus 201. The transport system 211 includes a medium transport mechanism such as the paper feed drum 216, the processing liquid application drum 222, the processing liquid drying drum 232, and the drawing drum 242 shown in FIG. The transport system 211 includes a motor as a power source (not shown) and a drive unit such as a motor drive circuit. The transport system 211 is included in the transport unit 22 described with reference to FIG.

  The paper feed control unit 312 illustrated in FIG. 19 operates the paper feed unit 210 according to a command from the system controller 300. The paper feed control unit 312 controls a supply start operation of the paper P, a supply stop operation of the paper P, and the like.

  The processing liquid application control section 314 operates the processing liquid application section 220 according to a command from the system controller 300. The processing liquid application control unit 314 controls the application amount of the processing liquid, the application timing, and the like.

  The processing liquid drying control unit 316 operates the processing liquid drying unit 230 according to a command from the system controller 300. The treatment liquid drying control unit 316 controls a drying gas temperature, a drying gas flow rate, and / or a drying gas injection timing.

  The drawing control unit 318 controls the drawing operation of the head unit 244 according to a command from the system controller 300. The drawing control unit 318 includes a waveform generation unit, a waveform storage unit, and a drive circuit. Illustration of the waveform generation unit, the waveform storage unit, and the drive circuit is omitted. The waveform generation unit generates a waveform of a driving voltage that causes each inkjet head of the head unit 244 to perform an ejection operation. The waveform storage unit stores the waveform of the drive voltage. The drive circuit generates a drive voltage having a drive waveform according to the dot data. The drive circuit supplies a drive voltage to the inkjet head of the head unit 244.

  The ink jet recording apparatus 201 includes an encoder 308 as a unit for detecting a rotation angle of the drawing drum 242 in the transport system 211. The encoder 308 is provided in the drawing drum 242, and outputs a signal corresponding to the amount of paper P transported by the drawing drum 242. Here, a rotary encoder that outputs a pulse signal for each unit rotation angle of the rotation axis of the drawing drum 242 is used. The ejection timing of each of the inkjet heads 246K, 246C, 246M, and 246Y is controlled in accordance with an ejection timing signal generated from an encoder signal output from the encoder 308.

  Based on the dot data generated through the processing by the image processing unit 306, the ejection timing and the ink ejection amount at each pixel position are determined, and the ejection timing at each pixel position, the driving voltage according to the ink ejection amount, and each pixel A control signal for determining the ejection timing of the image is generated. The drive voltage generated by the drawing control unit 318 is supplied to the inkjet heads 246K, 246C, 246M, 246Y, and dots are recorded by ink ejected from the inkjet heads 246K, 246C, 246M, 246Y.

  The ink drying control unit 324 operates the ink drying unit 250 according to a command from the system controller 300. The ink drying control unit 324 controls the drying gas temperature, the flow rate of the drying gas, and / or the timing of ejecting the drying gas.

  The paper discharge control unit 326 operates the stacking unit 260 in response to a command from the system controller 300. When the stacking device 262 shown in FIG. 18 includes an elevating mechanism, the paper discharge control unit 326 controls the operation of the elevating mechanism according to the increase or decrease of the sheet P. The paper discharge control unit 326 may control the sorting for sorting the printed matter.

  Further, the inkjet recording apparatus 201 includes an operation unit 330, a display unit 332, a data storage unit 334, and a program storage unit 336.

  The operation unit 330 includes an input device including an operation button, a keyboard, a mouse, a touch panel, a voice input device, or an appropriate combination of these. Information input via the operation unit 330 is sent to the system controller 300. The system controller 300 causes various processes to be executed according to the information input from the operation unit 330.

  The display unit 332 includes a display device such as a liquid crystal panel. The display unit 332 can display various setting information of the apparatus or various information such as abnormality information in response to a command from the system controller 300. The user can set various parameters and input and edit various information using the operation unit 330 while viewing the content displayed on the screen of the display unit 332.

  The data storage unit 334 stores data such as various parameters and tables used in the inkjet recording apparatus 201. Data such as various parameters and tables stored in the data storage unit 334 is read out via the system controller 300 and set in each unit of the apparatus.

  The program storage unit 336 stores a program used in each unit of the inkjet recording apparatus 201. Various programs stored in the program storage unit 336 are read out via the system controller 300 and are executed in each unit of the apparatus. The data storage unit 334 and the program storage unit 336 are configured using a storage device such as a hard disk device and / or a semiconductor memory.

  The inkjet recording apparatus 201 has a function of creating correction data described with reference to FIG. 16 and a function of image correcting vibration unevenness using correction data stored in advance.

<< Configuration Example 2 of Inkjet Recording Apparatus >>
FIG. 20 is a diagram illustrating another configuration example of the inkjet recording apparatus. An inkjet recording apparatus 410 shown in FIG. 20 is an apparatus that records an image on the surface (one side) of continuous paper 490 such as roll paper. Note that the downward direction in FIG. 20 coincides with the direction of gravity.

  As the continuous paper 490, for example, the following continuous paper 490 is assumed. That is, the continuous paper 490 has a thickness of 0.05 to 0.4 mm (more preferably, 0.1 to 0.3 mm), high-quality paper, medium-quality paper, coated paper, art paper, coated paper, lightweight coated paper. , India paper, high-quality color paper, fancy paper, newsprint paper, or PET (polyethylene terephthalate) having a thickness of 0.005 to 0.25 mm (more preferably 0.012 to 0.050 mm), polypropylene, nylon, polyethylene, Alternatively, it is a soft packaging material or label based on PVC (polyvinyl chloride).

  The inkjet recording device 410 has a transport unit 420 that transports the continuous paper 490 along a predetermined transport path. The transport section 420 includes a plurality of cylindrical rotating members including a drawing drum 440, a drying drum 450, and other rollers 429. The transport unit 420 roll-transports the continuous paper 490 along the transport path from the paper feed unit 421 to the winding unit 425.

  The ink jet recording apparatus 410 includes a paper feeding unit 421, a preprocessing unit 422, a drawing unit 423, a drying unit 424, and a winding unit 425. The paper feeding unit 421, the preprocessing unit 422, the drawing unit 423, the drying unit 424, and the winding unit 425 are arranged in this order along the transport path.

  In the paper supply unit 421, the continuous paper 490 is sent out. The paper feeding unit 421 has an unwinding roll 421A on which the continuous paper 490 is wound in advance. The unwinding roll 421A is a driving roller driven by a motor or the like, and sends out the continuous paper 490 by being driven. The paper feeding unit 421 applies a constant tension to the continuous paper 490 by rotation in a direction opposite to the unwinding direction of the unwinding roll 421A, a brake mechanism (not shown), and the like to feed the continuous paper 490.

  The pre-processing unit 422 performs pre-processing before printing (ink spraying) on the continuous paper 490. Specifically, the pretreatment unit 422 performs a step of applying an acid precoat liquid as an undercoat before printing on the continuous paper 490 and a step of drying the applied acid precoat liquid. The acid precoat liquid corresponds to the processing liquid described in FIG.

  In the drawing unit 423, a step of spraying ink on the continuous paper 490 is performed. The drawing unit 423 includes a drawing drum 440 around which the continuous paper 490 is wound, and a head unit 430 that sprays ink onto the continuous paper 490 wound around the drawing drum 440. The head unit 430 includes inkjet heads 432K, 432C, 432M, and 432Y that eject ink of each color of CMYK onto the surface of the continuous paper 490. Each of the inkjet heads 432K, 432C, 432M, and 432Y may be a line head having a structure similar to the structure described with reference to FIGS.

  The diameter of the drawing drum 440 is, for example, 50 to 1300 mm (more preferably 225 to 743 mm), and is about 450 mm in the present embodiment.

  The material of the drawing drum 440 is not particularly limited, but is stainless steel, carbon steel, aluminum, or the like. As stainless steel, for example, SUS (Steel Use Stainless) 304, SUS316, SUS313, or the like is used.

  The drawing drum 440 has been subjected to a surface treatment in order to improve hardness, corrosion resistance, and wear resistance. As the surface treatment, for example, a surface treatment such as hard chromium plating, electroless nickel plating, or alumite is used. As an example, the drawing drum 440 of the present embodiment is made of stainless steel and has been subjected to hard chrome plating surface treatment.

  In the drying unit 424, a drying step of drying the ink sprayed by the head unit 430 is performed. The drying unit 424 has a drying drum 450 around which the continuous paper 490 is wound. The drying drum 450 is, for example, a heating roll. As the heating roll, a roll in which a heating heater is incorporated inside the roll to heat the roll surface is used. The drying drum 450 may be an adsorption type roll. As a suction-type roll, for example, a suction hole for suctioning continuous paper on the roll surface is provided, and a negative pressure generating device (e.g., a vacuum pump, or a blower or the like) installed outside the printing press is used to suction the roll. The one that holds the continuous paper 490 being conveyed is used.

  Further, the drying unit 424 may have a drying box structure in order to improve the drying efficiency. That is, the drying unit 424 may include a drying box (not shown) that houses the drying drum 450 and the like. Further, the drying unit 424 may include a hot air device (not shown) that blows hot air on the continuous paper 490. The hot air device includes a hot air generator, a blowing nozzle, a suction blower for circulating hot air in the drying box, and the like.

  In the winding unit 425, the continuous paper 490 on which the image is recorded is wound. The winding unit 425 has a winding roll 425A for winding into a roll form. The take-up roll 425A is a drive roller.

  The control device of the inkjet recording device 410 shown in FIG. 20 may have the same configuration as the control device 14 described in FIG. The ink jet recording apparatus 410 has a function of creating correction data described with reference to FIG. 16 and a function of image correcting vibration unevenness using correction data stored in advance.

<< Advantages of Embodiment >>
(1) Since the correction data is calculated by averaging the positional deviation values of the dots ejected at the same moment using a plurality of measurement nozzles, the influence of the dot position reading error is reduced. Furthermore, since the plurality of measurement nozzles that eject droplets at the same moment are connected to different branch channels, landing position deviation due to crosstalk in the ink channel is also suppressed. Thereby, the calculation accuracy of the correction data is improved.

  (2) Since image correction is performed using the correction data calculated in this way, visibility of vibration unevenness can be suppressed.

  (3) Since image correction is performed using correction data stored in advance, it is possible to avoid an increase in size and complexity of the apparatus and its control system.

  (4) The image correction technique according to the present disclosure is effective not only when using a single-sheet recording medium but also when using a continuous medium such as roll paper.

<< Hardware configuration of each processing unit and control unit >>
The image data acquisition unit 32, the dot data creation unit 34, the correction processing unit 35, the drawing control unit 36, the correction data storage unit 38, the measurement nozzle setting unit 40, and the correction data creation unit of the control device 14 described in FIG. 42, a read data acquisition unit 44, a read data storage unit 45, a correction data calculation processing unit 46, and a dot position measurement unit 47, and the communication unit 302, the image processing unit 306, the transport control unit 310 described in FIG. A processing unit (processing unit) that executes various processes such as a paper control unit 312, a processing liquid application control unit 314, a processing liquid drying control unit 316, a drawing control unit 318, an ink drying control unit 324, a paper discharge control unit 326, and the like. The hardware structure of ()) includes various processors as follows.

  Various processors include general-purpose processors that execute programs and function as various processing units, such as CPUs (Central Processing Units) and FPGAs (Field Programmable Gate Arrays). A dedicated electric circuit, which is a processor having a circuit configuration specifically designed to execute a specific process such as a programmable logic device (PLD) or an ASIC (Application Specific Integrated Circuit), is included.

  One processing unit may be configured by one of these various processors, or may be configured by two or more processors of the same type or different types. For example, one processing unit may be configured by a plurality of FPGAs or a combination of a CPU and an FPGA. Further, a plurality of processing units may be configured by one processor. As an example of configuring a plurality of processing units with one processor, first, as represented by a computer such as a client or a server, one processor is configured by a combination of one or more CPUs and software. There is a form in which a processor functions as a plurality of processing units. Second, as represented by a system-on-chip (SoC), a form using a processor that realizes the function of the entire system including a plurality of processing units by one IC (Integrated Circuit) chip is used. is there. As described above, the various processing units are configured by using one or more of the above various processors as a hardware structure.

  Furthermore, the hardware structure of these various processors is more specifically an electric circuit (circuitry) combining circuit elements such as semiconductor elements.

<< About the program that makes a computer function as a control device >>
A program for causing a computer to function as the control device 14 described in the above embodiment is recorded on an optical disk, a magnetic disk, or another computer-readable medium (a non-transitory information storage medium that is a tangible entity), and the program is provided through the information storage medium. It is possible to Instead of providing the program by storing the program in such an information storage medium, the program signal can be provided as a download service using a communication network such as the Internet.

  Further, it is also possible to provide the function of the control device 14 according to the present embodiment as an application server, and perform a service of providing a processing function through a communication network.

  Further, by incorporating this program into a computer, each function of the control device 14 can be realized by the computer, and the correction data creation function, the correction processing function, the recording control function, and the like described in the above embodiment are realized. can do.

  A part or all of a program for realizing recording control including a correction data creation function and other various processing functions described in the present embodiment is incorporated in a higher-level control device such as a host computer. Can be applied as an operation program of the central processing unit (CPU).

<< About the transport mechanism of the recording medium >>
The transport mechanism for transporting the recording medium is not limited to the drum transport system, but may employ various forms such as a suction belt transport system, a nip transport system, a chain transport system, and a pallet transport system. When a continuous medium is used, a so-called roll-to-roll transport mechanism such as a web transport scheme is used.

<< About recording media >>
The “recording medium” is a general term for various terms such as paper, recording paper, printing paper, printing medium, printing medium, printing medium, image forming medium, image forming medium, image receiving medium, and discharging medium. The material and shape of the recording medium are not particularly limited, and various sheet materials can be used regardless of the material or shape, such as a seal sheet, a resin sheet, a film, a cloth, a nonwoven fabric, or the like.

《Discharge method》
The ejector of the ink jet head includes a nozzle that discharges a liquid, a pressure chamber that communicates with the nozzle, and a discharge energy generating element that applies discharge energy to the liquid in the pressure chamber. With respect to the ejection method for ejecting liquid droplets from the nozzle of the ejector, means for generating ejection energy is not limited to a piezoelectric element, and various ejection energy generating elements such as a heating element and an electrostatic actuator can be applied. For example, a method in which droplets are ejected using pressure of film boiling caused by heating of a liquid by a heating element can be adopted. Depending on the ejection method of the ink jet head, a corresponding ejection energy generating element is provided in the channel structure.

<< Another embodiment of the inkjet recording apparatus >>
In the above-described embodiment, the single-pass type inkjet recording apparatus has been described. However, the application range of the present invention is not limited to this, and a plurality of short-length recording heads such as a serial type (shuttle scan type) head are moved while moving. The present invention is also applicable to an ink jet recording apparatus that performs image recording by performing head scanning twice. When a color image is formed using an ink jet recording head, a head may be arranged for each color of a plurality of inks, or a single recording head may eject a plurality of inks. Good.

<< About recording media >>
“Recording medium” is a medium used for recording an image. The term recording medium includes the concept of what is called by various terms such as recording paper, printing paper, printing medium, printing medium, printing medium, image forming medium, image forming medium, image receiving medium, and discharging medium. The material and shape of the recording medium are not particularly limited, and various sheet materials can be used regardless of the material or shape, such as a seal sheet, a resin sheet, a film, a cloth, a nonwoven fabric, or the like. The recording medium is not limited to a single-sheet medium, but may be a continuous medium such as continuous paper. In addition, the sheet-fed recording medium is not limited to a cut sheet prepared in advance to a prescribed size, but may be a sheet obtained by cutting a continuous medium to a prescribed size as needed.

《Terminology》
The term “ink-jet recording device” is a concept of a term such as a printing machine, a printer, a printing device, a printing device, an image forming device, an image recording device, an image output device, or a drawing device that records an image by an ink-jet method. Including. Further, the term “inkjet recording device” includes the concept of an image recording system in which a plurality of devices are combined.

  The “image” is to be interpreted in a broad sense, and includes a color image, a black and white image, a single color image, a gradation image, a uniform density (solid) image, and the like. "Image" is not limited to a photographic image, but includes a pattern, a character, a symbol, a line drawing, a mosaic pattern, a color separation pattern, a line pattern, a dot pattern, various other patterns, a test chart, or an appropriate combination thereof. Used as a generic term.

  “Recording” an image includes the concept of terms such as image formation, printing, printing, drawing, and printing, and these terms can be interchanged as appropriate.

  As used herein, the term “orthogonal” or “perpendicular” refers to the case where the light beam intersects at an angle of substantially 90 ° among the modes of intersecting at an angle of less than 90 ° or more than 90 °. And a mode in which the same operation and effect as those described above are generated. The term “parallel” in the present specification includes, among strictly non-parallel aspects, aspects that can be regarded as substantially parallel, which provide substantially the same operation and effect as in the case of parallel.

《Other》
In the embodiment of the present invention described above, constituent elements can be appropriately changed, added, or deleted without departing from the spirit of the present invention. The present invention is not limited to the above-described embodiments, and many modifications can be made by those having ordinary knowledge in the related field within the technical spirit of the present invention.

  In the embodiment of the present invention described above, constituent elements can be appropriately changed, added, or deleted without departing from the spirit of the present invention. The present invention is not limited to the above-described embodiments, and many modifications can be made by those having ordinary knowledge in the related field within the technical spirit of the present invention.

DESCRIPTION OF SYMBOLS 10 Ink-jet recording apparatus 12 Printer main body 14 Control device 20, 20A, 20B Recording medium 21A Image area 21B Margin area 22 Conveyance part 24 Head unit 26 Image reading device 28 Ejection part 30 Image data 32 Image data acquisition part 34 Dot data creation part 35 correction processing unit 36 drawing control unit 38 correction data storage unit 40 measurement nozzle setting unit 41 measurement dot row 42 correction data creation unit 44 read data acquisition unit 45 read data storage unit 46 correction data calculation processing unit 47 dot Position measuring unit 50 Ink jet head 52 Head module 52A Nozzle surface 54 Base frame 56 Flexible substrate 60 Nozzle 62 Ejector 64 Nozzle channel 66 Cover plate 68 Movable space 70 Supply-side common main channel 72 Supply-side common branch channel 74 Individual supply channel 80 Collection Side common main flow path 82 Collection side common branch flow path 84 Individual collection path 90 Pressure chamber 92 Piezoelectric element 94 Vibrating plate 96 Individual electrode 98 Piezoelectric body 201 Inkjet recording device 210 Paper supply unit 211 Transport system 212 Paper supply device 212A Paper supply table 214 Feeder Board 216 Paper feed drum 220 Processing liquid coating unit 222 Processing liquid coating drum 223 Gripper 224 Processing liquid coating unit 230 Processing liquid drying unit 232 Processing liquid drying drum 233 Gripper 234 Hot air blower 240 Drawing unit 242 Drawing drum 243 Gripper 244 Head unit 246K 246C, 246M, 246Y Inkjet head 248 Image reading device 250 Ink drying unit 251 Chain delivery 252 Paper guide 252A First paper guide 252B Second paper guide 253 Hot air blowing unit 254 Chain 255 Upper 260 Stacking unit 262 Stacking device 262A Stacking tray 300 System controller 302 Communication unit 304 Image memory 306 Image processing unit 308 Encoder 310 Transport control unit 312 Feed control unit 314 Processing liquid application control unit 316 Processing liquid drying control unit 318 Drawing control Unit 324 Ink drying control unit 326 Discharge control unit 330 Operation unit 332 Display unit 334 Data storage unit 336 Program storage unit 410 Ink jet recording device 420 Transport unit 421 Feed unit 421A Unwind roll 422 Preprocessing unit 423 Drawing unit 424 Drying unit 425 Take-up unit 425A Take-up roll 429 Other rollers 430 Head unit 432K, 432C, 432M, 432Y Inkjet head 440 Drawing drum 450 Drying drum 490 Continuous paper 500 Host computer P Paper S12- 24 step of step S32~S38 image recording method of the correction data creation method

Claims (15)

An image recording method for recording an image on a recording medium using an inkjet head,
By repeatedly ejecting droplets at a constant time interval from each of the plurality of measurement nozzles specified from the nozzle array of the ink jet head, and by transporting the recording medium, a plurality of measurement dots are formed on the recording medium. Recording the columns;
Reading the plurality of measurement dot rows recorded on the recording medium using an image reading device,
From the read data indicating the read image of the measurement dot row obtained via the image reading device, a step of calculating a position shift value of the dots included in the measurement dot row,
Among the dots ejected from each of the plurality of measurement nozzles, the average of the positional deviation values of the dots ejected at the same instant represents a relative positional deviation value between the inkjet head and the recording medium. Calculating correction data;
Storing the correction data in a storage unit;
Correcting image data using the correction data stored in the storage unit,
Controlling the ink ejection operation of the inkjet head using the corrected image data,
The ink flow path provided inside the inkjet head has a structure including a plurality of branch paths and a main flow path to which the plurality of branch paths are connected, and each of the plurality of branch paths has a plurality of branch paths. The nozzle is connected,
The image recording method, wherein the plurality of measurement nozzles that eject droplets at the same moment are respectively connected to the different branch channels. The recording medium is transported in a first direction, and each of the plurality of measurement nozzles is arranged at a different position in a second direction that is a width direction of the recording medium orthogonal to the first direction,
In the step of calculating the position shift value, the position shift value in each of the first direction and the second direction is calculated,
2. The image recording method according to claim 1, wherein, in the step of calculating the correction data, the correction data representing the position shift value in each of the first direction and the second direction is calculated. 3.   The step of calculating the correction data includes, based on the positional deviation values of the dots ejected at the same moment in the plurality of measurement dot rows, a positional deviation value of a nozzle area where the dots are not ejected. 3. The image recording method according to claim 1, further comprising a step of calculating the correction data by extrapolating the data. When recording an image on the recording medium using a plurality of the inkjet heads, each inkjet head has the correction data,
4. The image recording method according to claim 1, wherein image data corresponding to each inkjet head is corrected using the correction data for each inkjet head. 5. The measurement dot row includes a dot row having a length corresponding to at least one cycle of the repetition pattern when the relative speed fluctuation between the inkjet head and the recording medium is reproduced in a constant repetition pattern,
The image recording method according to claim 1, wherein the correction data includes data corresponding to one cycle of the repeating pattern. The recording medium is conveyed using a rotating member,
The relative speed fluctuation between the inkjet head and the recording medium is reproduced in a rotation cycle of the rotating member,
The image recording method according to claim 5, wherein the correction data includes data corresponding to a rotation cycle of the rotating member.   The image recording method according to claim 1, wherein the recording medium is a continuous medium, and the recording medium is roll-conveyed.   The image recording method according to claim 1, wherein the inkjet head is a line head configured by connecting a plurality of head modules.   9. The image recording method according to claim 8, wherein at least some of the plurality of measurement nozzles that eject droplets at the same moment are connected to the respective separate branch channels in the same head module. 10. .   The image recording method according to claim 8, wherein at least some of the plurality of measurement nozzles that eject droplets at the same moment belong to different head modules.   The plurality of measurement nozzles that eject droplets at the same moment include a plurality of nozzles connected to the respective separate branch passages in the same head module, and another plurality of nozzles belonging to different head modules. The image recording method according to claim 8, comprising: A method for creating correction data used when correcting an image defect caused by a relative speed variation between an inkjet head and a recording medium in an inkjet recording apparatus,
By repeatedly ejecting droplets at a constant time interval from each of the plurality of measurement nozzles specified from the nozzle array of the ink jet head, and by transporting the recording medium, a plurality of measurement dots are formed on the recording medium. Recording the columns;
Reading the plurality of measurement dot rows recorded on the recording medium using an image reading device,
From the read data indicating the read image of the measurement dot row obtained via the image reading device, a step of calculating a position shift value of the dots included in the measurement dot row,
Of the dots ejected from each of the plurality of measurement nozzles, the average of the position offset values of the dots ejected at the same moment is used to calculate the relative position offset value between the inkjet head and the recording medium. Calculating the correction data to represent;
Storing the correction data in a storage unit;
Including
The ink flow path provided inside the inkjet head has a structure including a plurality of branch paths and a main flow path to which the plurality of branch paths are connected, and each of the plurality of branch paths has a plurality of branch paths. The nozzle is connected,
The correction data creating method, wherein the plurality of measurement nozzles that eject droplets at the same moment are connected to different branch channels, respectively. An inkjet head,
A transport unit that transports a recording medium to the inkjet head,
By repeatedly ejecting droplets at a constant time interval from each of the plurality of measurement nozzles specified from the nozzle array of the ink jet head, and by transporting the recording medium, a plurality of measurement dots are formed on the recording medium. A first control unit that performs control to record a column;
An image reading device that reads the plurality of measurement dot rows recorded on the recording medium,
A process of calculating a displacement value of a dot included in the measurement dot row from read data indicating a read image of the measurement dot row obtained via the image reading device; and the plurality of measurement nozzles Of the dots ejected at the same moment among the dots ejected from each of the above, an average of the displacement values of the dots ejected at the same moment is calculated as correction data representing a relative displacement value of the ink jet head and the recording medium. A correction data calculation processing unit for performing
A storage unit for storing the correction data,
A correction processing unit that corrects image data using the correction data stored in the storage unit,
A second control unit that controls an ink ejection operation of the inkjet head using the image data corrected by the correction processing unit,
The ink flow path provided inside the inkjet head has a structure including a plurality of branch paths and a main flow path to which the plurality of branch paths are connected, and each of the plurality of branch paths has a plurality of branch paths. The nozzle is connected,
The inkjet recording apparatus, wherein the plurality of measurement nozzles that perform droplet ejection at the same moment are connected to the respective separate branch channels. A recording control device that controls an inkjet recording device,
By repeatedly discharging droplets at predetermined time intervals simultaneously from each of a plurality of measurement nozzles specified from a nozzle array of an ink jet head used in the ink jet recording apparatus, and by conveying a recording medium, the recording is performed. A first control unit that controls recording of a plurality of measurement dot arrays on a medium;
The plurality of measurement dot rows recorded on the recording medium are included in the measurement dot row from read data indicating a read image of the measurement dot row obtained by reading using an image reading device. A process of calculating a displacement value of a dot, and, among the dots ejected from each of the plurality of measurement nozzles, averaging the displacement values of the dots ejected at the same moment, the inkjet printing A process of calculating correction data representing a relative position shift value between the head and the recording medium, and a correction data calculation processing unit that performs
A storage unit for storing the correction data,
A correction processing unit that corrects image data using the correction data stored in the storage unit,
A second control unit that controls an ink ejection operation of the inkjet head using the image data corrected by the correction processing unit,
The ink flow path provided inside the inkjet head has a structure including a plurality of branch paths and a main flow path to which the plurality of branch paths are connected, and each of the plurality of branch paths has a plurality of branch paths. The nozzle is connected,
The recording control device, wherein the plurality of measurement nozzles that perform droplet ejection at the same moment are respectively connected to the separate branch channels. A program for causing a computer to realize a control function of the inkjet recording apparatus,
The droplets are repeatedly ejected simultaneously from each of the plurality of measurement nozzles specified from the nozzle array of the inkjet head used in the inkjet recording apparatus at a constant time interval, and the recording medium is conveyed, whereby the recording is performed. A first control function for recording a plurality of measurement dot arrays on a medium,
The plurality of measurement dot rows recorded on the recording medium are included in the measurement dot row from read data indicating a read image including the measurement dot row obtained by reading using an image reading device. A function for calculating the dot displacement value of the
Of the dots ejected from each of the plurality of measurement nozzles, the average of the position offset values of the dots ejected at the same moment is used to calculate the relative position offset value between the inkjet head and the recording medium. A function of calculating correction data to be represented;
A function of storing the correction data,
A correction processing function of correcting image data using the stored correction data,
A second control function of controlling an ink ejection operation of the inkjet head using the image data corrected by the correction processing function, and
The ink flow path provided inside the inkjet head has a structure including a plurality of branch paths and a main flow path to which the plurality of branch paths are connected, and each of the plurality of branch paths has a plurality of branch paths. The nozzle is connected,
The program in which the plurality of measurement nozzles that perform droplet ejection at the same moment are respectively connected to the separate branch channels.